An Autonomic Control Plane (ACP)
draft-ietf-anima-autonomic-control-plane-12
The information below is for an old version of the document.
| Document | Type | This is an older version of an Internet-Draft that was ultimately published as an RFC. | |
|---|---|---|---|
| Authors | Michael H. Behringer , Toerless Eckert , Steinthor Bjarnason | ||
| Last updated | 2017-11-29 (Latest revision 2017-10-13) | ||
| Replaces | draft-behringer-anima-autonomic-control-plane | ||
| Stream | Internet Engineering Task Force (IETF) | ||
| Formats | |||
| Reviews |
RTGDIR Last Call review
(of
-24)
Not Ready
SECDIR Telechat review
(of
-16)
Has Issues
GENART Telechat review
(of
-16)
Ready with Nits
SECDIR Early review
(of
-13)
Has Issues
GENART Last Call review
(of
-13)
Not Ready
|
||
| Stream | WG state | WG Document | |
| Document shepherd | Sheng Jiang | ||
| IESG | IESG state | I-D Exists | |
| Consensus boilerplate | Yes | ||
| Telechat date | (None) | ||
| Responsible AD | (None) | ||
| Send notices to | "Sheng Jiang" <jiangsheng@huawei.com> |
draft-ietf-anima-autonomic-control-plane-12
ANIMA WG M. Behringer, Ed.
Internet-Draft
Intended status: Standards Track T. Eckert, Ed.
Expires: April 15, 2018 Huawei
S. Bjarnason
Arbor Networks
October 12, 2017
An Autonomic Control Plane (ACP)
draft-ietf-anima-autonomic-control-plane-12
Abstract
Autonomic functions need a control plane to communicate, which
depends on some addressing and routing. This Autonomic Management
and Control Plane should ideally be self-managing, and as independent
as possible of configuration. This document defines such a plane and
calls it the "Autonomic Control Plane", with the primary use as a
control plane for autonomic functions. It also serves as a "virtual
out of band channel" for OAM (Operations Administration and
Management) communications over a network that is secure and reliable
even when the network is not configured, or not misconfigured.
Status of This Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet-
Drafts is at https://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress."
This Internet-Draft will expire on April 15, 2018.
Copyright Notice
Copyright (c) 2017 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents
Behringer, et al. Expires April 15, 2018 [Page 1]
Internet-Draft An Autonomic Control Plane (ACP) October 2017
(https://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents
carefully, as they describe your rights and restrictions with respect
to this document. Code Components extracted from this document must
include Simplified BSD License text as described in Section 4.e of
the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 4
2. Acronyms and Terminology . . . . . . . . . . . . . . . . . . 6
3. Use Cases for an Autonomic Control Plane . . . . . . . . . . 10
3.1. An Infrastructure for Autonomic Functions . . . . . . . . 10
3.2. Secure Bootstrap over a not configured Network . . . . . 10
3.3. Data-Plane Independent Permanent Reachability . . . . . . 11
4. Requirements . . . . . . . . . . . . . . . . . . . . . . . . 12
5. Overview . . . . . . . . . . . . . . . . . . . . . . . . . . 12
6. Self-Creation of an Autonomic Control Plane (ACP) (Normative) 14
6.1. ACP Domain, Certificate and Network . . . . . . . . . . . 14
6.1.1. Certificate Domain Information Field . . . . . . . . 15
6.1.2. ACP domain membership check . . . . . . . . . . . . . 18
6.1.3. Certificate Maintenance . . . . . . . . . . . . . . . 18
6.2. ACP Adjacency Table . . . . . . . . . . . . . . . . . . . 20
6.3. Neighbor Discovery with DULL GRASP . . . . . . . . . . . 21
6.4. Candidate ACP Neighbor Selection . . . . . . . . . . . . 23
6.5. Channel Selection . . . . . . . . . . . . . . . . . . . . 24
6.6. Candidate ACP Neighbor verification . . . . . . . . . . . 26
6.7. Security Association protocols . . . . . . . . . . . . . 26
6.7.1. ACP via IKEv2 . . . . . . . . . . . . . . . . . . . . 26
6.7.2. ACP via dTLS . . . . . . . . . . . . . . . . . . . . 27
6.7.3. ACP Secure Channel Requirements . . . . . . . . . . . 28
6.8. GRASP in the ACP . . . . . . . . . . . . . . . . . . . . 28
6.8.1. GRASP as a core service of the ACP . . . . . . . . . 28
6.8.2. ACP as the Security and Transport substrate for GRASP 29
6.9. Context Separation . . . . . . . . . . . . . . . . . . . 33
6.10. Addressing inside the ACP . . . . . . . . . . . . . . . . 33
6.10.1. Fundamental Concepts of Autonomic Addressing . . . . 33
6.10.2. The ACP Addressing Base Scheme . . . . . . . . . . . 35
6.10.3. ACP Zone Addressing Sub-Scheme . . . . . . . . . . . 35
6.10.4. ACP Manual Addressing Sub-Scheme . . . . . . . . . . 38
6.10.5. ACP Vlong Addressing Sub-Scheme . . . . . . . . . . 39
6.10.6. Other ACP Addressing Sub-Schemes . . . . . . . . . . 40
6.11. Routing in the ACP . . . . . . . . . . . . . . . . . . . 40
6.11.1. RPL Profile . . . . . . . . . . . . . . . . . . . . 41
6.12. General ACP Considerations . . . . . . . . . . . . . . . 44
6.12.1. Performance . . . . . . . . . . . . . . . . . . . . 44
6.12.2. Addressing of Secure Channels in the data-plane . . 45
Behringer, et al. Expires April 15, 2018 [Page 2]
Internet-Draft An Autonomic Control Plane (ACP) October 2017
6.12.3. MTU . . . . . . . . . . . . . . . . . . . . . . . . 45
6.12.4. Multiple links between nodes . . . . . . . . . . . . 46
6.12.5. ACP interfaces . . . . . . . . . . . . . . . . . . . 46
7. ACP support on L2 switches/ports (Normative) . . . . . . . . 49
7.1. Why . . . . . . . . . . . . . . . . . . . . . . . . . . . 49
7.2. How (per L2 port DULL GRASP) . . . . . . . . . . . . . . 50
8. Support for Non-ACP Components (Normative) . . . . . . . . . 52
8.1. ACP Connect . . . . . . . . . . . . . . . . . . . . . . . 52
8.1.1. Non-ACP Controller / NMS system . . . . . . . . . . . 52
8.1.2. Software Components . . . . . . . . . . . . . . . . . 54
8.1.3. Auto Configuration . . . . . . . . . . . . . . . . . 55
8.1.4. Combined ACP/Data-Plane Interface (VRF Select) . . . 56
8.1.5. Use of GRASP . . . . . . . . . . . . . . . . . . . . 57
8.2. ACP through Non-ACP L3 Clouds (Remote ACP neighbors) . . 58
8.2.1. Configured Remote ACP neighbor . . . . . . . . . . . 58
8.2.2. Tunneled Remote ACP Neighbor . . . . . . . . . . . . 59
8.2.3. Summary . . . . . . . . . . . . . . . . . . . . . . . 60
9. Benefits (Informative) . . . . . . . . . . . . . . . . . . . 60
9.1. Self-Healing Properties . . . . . . . . . . . . . . . . . 60
9.2. Self-Protection Properties . . . . . . . . . . . . . . . 61
9.2.1. From the outside . . . . . . . . . . . . . . . . . . 61
9.2.2. From the inside . . . . . . . . . . . . . . . . . . . 62
9.3. The Administrator View . . . . . . . . . . . . . . . . . 63
10. Further Considerations (Informative) . . . . . . . . . . . . 63
10.1. BRSKI Bootstrap (ANI) . . . . . . . . . . . . . . . . . 63
10.2. ACP (and BRSKI) Diagnostics . . . . . . . . . . . . . . 65
10.3. Enabling and disabling ACP/ANI . . . . . . . . . . . . . 69
10.3.1. Filtering for non-ACP/ANI packets . . . . . . . . . 70
10.3.2. Admin Down State . . . . . . . . . . . . . . . . . . 70
10.3.3. Interface level ACP/ANI enable . . . . . . . . . . . 73
10.3.4. Which interfaces to auto-enable ? . . . . . . . . . 73
10.3.5. Node Level ACP/ANI enable . . . . . . . . . . . . . 75
10.3.6. Undoing ANI/ACP enable . . . . . . . . . . . . . . . 76
10.3.7. Summary . . . . . . . . . . . . . . . . . . . . . . 77
10.4. ACP Neighbor discovery protocol selection . . . . . . . 77
10.4.1. LLDP . . . . . . . . . . . . . . . . . . . . . . . . 77
10.4.2. mDNS and L2 support . . . . . . . . . . . . . . . . 78
10.4.3. Why DULL GRASP . . . . . . . . . . . . . . . . . . . 78
10.5. Choice of routing protocol (RPL) . . . . . . . . . . . . 78
10.6. Extending ACP channel negotiation (via GRASP) . . . . . 80
10.7. CAs, domains and routing subdomains . . . . . . . . . . 81
10.8. Adopting ACP concepts for other environments . . . . . . 83
11. Security Considerations . . . . . . . . . . . . . . . . . . . 85
12. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 86
13. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 87
14. Change log [RFC Editor: Please remove] . . . . . . . . . . . 87
14.1. Initial version . . . . . . . . . . . . . . . . . . . . 87
14.2. draft-behringer-anima-autonomic-control-plane-00 . . . . 87
Behringer, et al. Expires April 15, 2018 [Page 3]
Internet-Draft An Autonomic Control Plane (ACP) October 2017
14.3. draft-behringer-anima-autonomic-control-plane-01 . . . . 87
14.4. draft-behringer-anima-autonomic-control-plane-02 . . . . 88
14.5. draft-behringer-anima-autonomic-control-plane-03 . . . . 88
14.6. draft-ietf-anima-autonomic-control-plane-00 . . . . . . 88
14.7. draft-ietf-anima-autonomic-control-plane-01 . . . . . . 88
14.8. draft-ietf-anima-autonomic-control-plane-02 . . . . . . 89
14.9. draft-ietf-anima-autonomic-control-plane-03 . . . . . . 89
14.10. draft-ietf-anima-autonomic-control-plane-04 . . . . . . 90
14.11. draft-ietf-anima-autonomic-control-plane-05 . . . . . . 90
14.12. draft-ietf-anima-autonomic-control-plane-06 . . . . . . 91
14.13. draft-ietf-anima-autonomic-control-plane-07 . . . . . . 91
14.14. draft-ietf-anima-autonomic-control-plane-08 . . . . . . 93
14.15. draft-ietf-anima-autonomic-control-plane-09 . . . . . . 94
14.16. draft-ietf-anima-autonomic-control-plane-10 . . . . . . 96
14.17. draft-ietf-anima-autonomic-control-plane-11 . . . . . . 98
14.18. draft-ietf-anima-autonomic-control-plane-12 . . . . . . 98
15. References . . . . . . . . . . . . . . . . . . . . . . . . . 100
15.1. Normative References . . . . . . . . . . . . . . . . . . 100
15.2. Informative References . . . . . . . . . . . . . . . . . 102
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 105
1. Introduction
Autonomic Networking is a concept of self-management: Autonomic
functions self-configure, and negotiate parameters and settings
across the network. [RFC7575] defines the fundamental ideas and
design goals of Autonomic Networking. A gap analysis of Autonomic
Networking is given in [RFC7576]. The reference architecture for
Autonomic Networking in the IETF is currently being defined in the
document [I-D.ietf-anima-reference-model]
Autonomic functions need an autonomously built communications
infrastructure or network plane (there is no well-established name
for this). This infrastructure needs to be secure, resilient and re-
usable by all autonomic functions. Section 5 of [RFC7575] introduces
that infrastructure and calls it the "Autonomic Control Plane" (ACP).
More descriptively it would be the "Autonomic communications
infrastructure for Management and Control". For naming consistency
with that prior document, this document continues to use the name ACP
though.
Today, the management and control plane of networks typically runs in
the global routing table, which is dependent on correct configuration
and routing. Misconfigurations or routing problems can therefore
disrupt management and control channels. Traditionally, an out of
band network has been used to recover from such problems, or
personnel is sent on site to access devices through console ports
(craft ports). However, both options are expensive.
Behringer, et al. Expires April 15, 2018 [Page 4]
Internet-Draft An Autonomic Control Plane (ACP) October 2017
In increasingly automated networks either centralized management
systems or distributed autonomic service agents in the network
require a control plane which is independent of the configuration of
the network they manage, to avoid impacting their own operations
through the configuration actions they take.
This document describes a modular design for a self-forming, self-
managing and self-protecting "Autonomic Control Plane" (ACP) which is
a virtual in-band network designed to be as independent as possible
of configuration, addressing and routing problems. The details how
this achieved are defined in Section 6. The ACP is designed to
remains operational even in the presence of configuration errors,
addressing or routing issues, or where policy could inadvertently
affect connectivity of both data packets or control packets.
This document uses the term "data-plane" to refer to anything in the
network nodes that is not the ACP, and therefore considered to be
dependent on (mis-)configuration. This data-plen includes both the
traditional forwarding-plane, as well as any pre-existing control-
plane, such as routing protocols that establish routing tables for
the forwarding plane.
The Autonomic Control Plane serves several purposes at the same time:
o Autonomic functions communicate over the ACP. The ACP therefore
supports directly Autonomic Networking functions, as described in
[I-D.ietf-anima-reference-model]. For example, GRASP
[I-D.ietf-anima-grasp] runs securely inside the ACP and depends on
the ACP as its "security and transport substrate".
o An operator can use it to log into remote devices, even if the
network is misconfigured or not configured.
o A controller or network management system can use it to securely
bootstrap network devices in remote locations, even if the network
in between is not yet configured; no data-plane dependent
bootstrap configuration is required. An example of such a secure
bootstrap process is described in
[I-D.ietf-anima-bootstrapping-keyinfra]
This document describes these use cases for the ACP in Section 3, it
defines the requirements in Section 4. Section 5 gives an overview
how the ACP is constructed, and in Section 6 the process is defined
in detail. Section 7 defines how to support ACP on L2 switches.
Section 8 explains how non-ACP nodes and networks can be integrated.
The following sections are non-normative: Section 7 reviews benefits
of the ACP (after all the details have been defined), Section 10
provides additional explanations and describes additional details or
Behringer, et al. Expires April 15, 2018 [Page 5]
Internet-Draft An Autonomic Control Plane (ACP) October 2017
future work possibilities that where considered not to be appropriate
for standardization in this document but nevertheless assumed to be
helpful for candidate adopters of the ACP.
The ACP as defined in this document can be implemented and operated
without dependency against other components of autonomous networks
except for the GRASP protocol on which it depends. The document
"Autonomic Network Stable Connectivity"
[I-D.ietf-anima-stable-connectivity] describes how the ACP alone can
be used to provide stable connectivity for autonomic and non-
autonomic OAM applications ("Operations Administration and
Management"). It also explains on how existing management solutions
can leverage the ACP in parallel with traditional management models,
when to use the ACP and, how to integrate IPv4 based management, etc.
Combining ACP with BRSKI ("Bootstrapping Remote Secure Key
Infrastructures", see [I-D.ietf-anima-bootstrapping-keyinfra])
results in the "Autonomic Network Infrastructure" as defined in
[I-D.ietf-anima-reference-model]. which provides autonomic
connectivity (from ACP) with full secure zero touch bootstrap (from
BRSKI). The ANI itself does not constitute an Autonomic Network, but
it enables building more or less autonomic networks on top of it -
using either centralized, SDN ("Software Defined Networking", see
[RFC7426]) style automation or distributed automation via ASA
("Autonomic Service Agents") / "Autonomic Functions" - or a mixture
of both. See [I-D.ietf-anima-reference-model] for more information.
2. Acronyms and Terminology
In the rest of the document we will refer to systems using the ACP as
"nodes". Typically such a node is a physical (network equipment)
device, but it can equally be some virtualized system. Therefore, we
do not refer to them as devices unless the context specifically calls
for a physical system.
This document introduces or uses the following terms (sorted
alphabetically). Terms introduced are explained on first use, so
this list is for reference only.
ACP: "Autonomic Control Plane". The Autonomic Function defined in
this document. It provides secure zero-touch transitive (network
wide) IPv6 connectivity for all nodes in the same ACP domain. The
ACP is primarily meant to be used as a component of the ANI to
enable Autonomic Networks but it can equally be used in simple ANI
networks (with no other Autonomic Functions) or completely by
itself.
Behringer, et al. Expires April 15, 2018 [Page 6]
Internet-Draft An Autonomic Control Plane (ACP) October 2017
ACP address: An IPv6 address assigned to the ACP node. It is stored
in the domain information field of the ACP domain certificate.
ACP address range/set: The ACP address may imply a range or set of
addresses that the node can assign for different purposes. This
address range/set is derived by the node from the format of the
ACP address called the "addressing sub-scheme".
ACP connect: An interface on an ACP node providing access to the ACP
for non ACP capable nodes without using an ACP secure channel.
See Section 8.1.1.
ACP domain: The ACP domain is the set of nodes with domain
certificates that allow them to authenticate each other as members
of the ACP domain. See Section 6.1.2.
domain information (field): An rfc822Name information element (e.g.:
field) in the domain certificate in which the ACP relevant
information is encoded: the domain name and the ACP address.
ACP loopback interface: The interface in the ACP VRF that has the
ACP address assigned to it.
ACP network: The ACP network constitutes all the nodes that have
access to the ACP. It is the set of active and transitively
connected nodes of an ACP domain plus all nodes that get access to
the ACP of that domain via ACP edge nodes.
ACP (ULA) prefix(es): The prefixes routed across the ACP. In the
normal/simple case, the ACP has one ULA prefix, see Section 6.10.
The ACP routing table may include multiple ULA prefixes if the
"rsub" option is used to create addresses from more than one ULA
prefix. See Section 6.1.1. The ACP may also include non-ULA
prefixes if those are configured on ACP connect interfaces. See
Section 8.1.1.
ACP secure channel: A security association established hop-by-hop
between adjacent ACP nodes to carry traffic of the ACP VRF
separated from data-plane traffic in-band over the same links as
the data-plane.
ACP secure channel protocol: The protocol used to build an ACP
secure channel, e.g.: IKEv2/IPsec or dTLS.
ACP virtual interface: An interface in the ACP VRF mapped to one or
more ACP secure channels. See Section 6.12.5.
Behringer, et al. Expires April 15, 2018 [Page 7]
Internet-Draft An Autonomic Control Plane (ACP) October 2017
AN "Autonomic Network": A network according to
[I-D.ietf-anima-reference-model]. Its main components are ANI,
Autonomic Functions and Intent.
(AN) Domain Name: An FQDN (Fully Qualified Domain Name) in the
domain information field of the Domain Certificate. See
Section 6.1.1.
ANI (nodes/network): "Autonomic Network Infrastructure". The ANI is
the infrastructure to enable Autonomic Networks. It includes ACP,
BRSKI and GRASP. Every Autonomic Network includes the ANI, but
not every ANI network needs to include autonomic functions beyond
the ANI (nor intent). An ANI network without further autonomic
functions can for example support secure zero touch bootstrap and
stable connectivity for SDN networks - see
[I-D.ietf-anima-stable-connectivity].
ANIMA: "Autonomic Networking Integrated Model and Approach". ACP,
BRSKI and GRASP are products of the IETF ANIMA working group.
ASA: "Autonomic Service Agent". Autonomic software modules running
on an ANI device. The components making up the ANI (BRSKI, ACP,
GRASP) are also described as ASAs.
Autonomic Function: A function/service in an Autonomic Network (AN)
composed of one or more ASA across one or more ANI nodes.
BRSKI: "Bootstrapping Remote Secure Key Infrastructures"
([I-D.ietf-anima-bootstrapping-keyinfra]. A protocol extending
EST to enable secure zero touch bootstrap in conjunction with ACP.
ANI nodes use ACP, BRSKI and GRASP.
data-plane: The counterpoint to the ACP VRF in an ACP node: all VRFs
other than the ACP VRF. In a simple ACP or ANI node, the data-
plane is typically provisioned non-autonomic, for example manually
(including across the ACP) or via SDN controllers. In a full
Autonomic Network node, the data-plane is managed autonomically
via Autonomic Functions and Intent. Note that other (non-ANIMA)
RFC use the data-plane to refer to what is better called the
forwarding plane. This is not the way the term is used in this
document!
ACP (ANI/AN) Domain Certificate: A provisioned certificate (LDevID)
carrying the domain information field which is used by the ACP to
learn its address in the ACP and to derive and cryptographically
assert its membership in the ACP domain.
device: A physical system, or physical node.
Behringer, et al. Expires April 15, 2018 [Page 8]
Internet-Draft An Autonomic Control Plane (ACP) October 2017
Enrollment: The process where a node presents identification (for
example through keying material such as the private key of an
IDevID) to a network and acquires a network specific identity and
trust anchor such as an LDevID.
EST: "Enrollment over Secure Transport" ([RFC7030]). IETF standard
protocol for enrollment of a node with an LDevID. BRSKI is based
on EST.
GRASP: "Generic Autonomic Signaling Protocol". An extensible
signaling protocol required by the ACP for ACP neighbor discovery.
The ACP also provides the "security and transport substrate" for
the "ACP instance of GRASP" which is run inside the ACP to support
BRSKI and other future Autonomic Functions. See
[I-D.ietf-anima-grasp].
IDevID: An "Initial Device IDentity" X.509 certificate installed by
the vendor on new equipment. Contains information that
establishes the identity of the node in the context of its vendor/
manufacturer such as device model/type and serial number. See
[AR8021].
Intent: Northbound operator and automation facing interface of an
Autonomic Network according to [I-D.ietf-anima-reference-model].
LDevID: A "Local Device IDentity" is an X.509 certificate installed
during "enrollment". The Domain Certificate used by the ACP is an
LDevID. See [AR8021].
MIC: "Manufacturer Installed Certificate". Another word not used in
this document to describe an IDevID.
native interface: Interfaces existing on a node without
configuration of the already running node. On physical nodes
these are usually physical interfaces. On virtual nodes their
equivalent.
node: A system, e.g.: supporting the ACP according to this document.
Can be virtual or physical. Physical nodes are called devices.
RPL: "IPv6 Routing Protocol for Low-Power and Lossy Networks". The
routing protocol used in the ACP.
MASA (service): "Manufacturer Authorized Signing Authority". A
vendor/manufacturer or delegated cloud service on the Internet
used as part of the BRSKI protocol.
Behringer, et al. Expires April 15, 2018 [Page 9]
Internet-Draft An Autonomic Control Plane (ACP) October 2017
sUDI: "secured Unique Device Identifier". Another term not used in
this document to refer to an IDevID.
UDI: "Unique Device Identifier". In the context of this document
unsecured identity information of a node typically consisting of
at least device model/type and serial number, often in a vendor
specific format. See sUDI and LDevID.
ULA: A "Unique Local Address" (ULA) is an IPv6 address in the block
fc00::/7, defined in [RFC4193]. It is the approximate IPv6
counterpart of the IPv4 private address ([RFC1918]).
(ACP) VRF: The ACP is modelled in this document as a "Virtual
Routing and Forwarding" (VRF) component in a network node.
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
"OPTIONAL" in this document are to be interpreted as described in
[RFC2119] when they appear in ALL CAPS. When these words are not in
ALL CAPS (such as "should" or "Should"), they have their usual
English meanings, and are not to be interpreted as [RFC2119] key
words.
3. Use Cases for an Autonomic Control Plane
3.1. An Infrastructure for Autonomic Functions
Autonomic Functions need a stable infrastructure to run on, and all
autonomic functions should use the same infrastructure to minimize
the complexity of the network. This way, there is only need for a
single discovery mechanism, a single security mechanism, and other
processes that distributed functions require.
3.2. Secure Bootstrap over a not configured Network
Today, bootstrapping a new node typically requires all nodes between
a controlling node such as an SDN controller ("Software Defined
Networking", see [RFC7426]) and the new node to be completely and
correctly addressed, configured and secured. Bootstrapping and
configuration of a network happens in rings around the controller -
configuring each ring of devices before the next one can be
bootstrapped. Without console access (for example through an out of
band network) it is not possible today to make devices securely
reachable before having configured the entire network leading up to
them.
With the ACP, secure bootstrap of new devices can happen without
requiring any configuration such as the transit connectivity to
Behringer, et al. Expires April 15, 2018 [Page 10]
Internet-Draft An Autonomic Control Plane (ACP) October 2017
bootstrap further devices. A new device can automatically be
bootstrapped in a secure fashion and be deployed with a domain
certificate. This does not require any configuration on intermediate
nodes, because they can communicate zero-touch and securely through
the ACP.
3.3. Data-Plane Independent Permanent Reachability
Today, most critical control plane protocols and network management
protocols are running in the data-plane (global routing table) of the
network. This leads to undesirable dependencies between control and
management plane on one side and the data-plane on the other: Only if
the data-plane is operational, will the other planes work as
expected.
Data-plane connectivity can be affected by errors and faults, for
example misconfigurations that make AAA (Authentication,
Authorization and Accounting) servers unreachable can lock an
administrator out of a device; routing or addressing issues can make
a device unreachable; shutting down interfaces over which a current
management session is running can lock an admin irreversibly out of
the device. Traditionally only console access can help recover from
such issues.
Data-plane dependencies also affect applications in a NOC ("Network
Operations Center") such as SDN controller applications: Certain
network changes are today hard to operate, because the change itself
may affect reachability of the devices. Examples are address or mask
changes, routing changes, or security policies. Today such changes
require precise hop-by-hop planning.
The ACP provides reachability that is independent of the data-plane
(except for the dependency discussed in Section 6.12.2 which can be
removed through future work), which allows control plane and
management plane to operate more robustly:
o For management plane protocols, the ACP provides the functionality
of a "Virtual-out-of-band (VooB) channel", by providing
connectivity to all nodes regardless of their configuration or
global routing table.
o For control plane protocols, the ACP allows their operation even
when the data-plane is temporarily faulty, or during transitional
events, such as routing changes, which may affect the control
plane at least temporarily. This is specifically important for
autonomic service agents, which could affect data-plane
connectivity.
Behringer, et al. Expires April 15, 2018 [Page 11]
Internet-Draft An Autonomic Control Plane (ACP) October 2017
The document "Autonomic Network Stable Connectivity"
[I-D.ietf-anima-stable-connectivity] explains the use cases for the
ACP in significantly more detail and explains how the ACP can be used
in practical network operations.
4. Requirements
The Autonomic Control Plane has the following requirements:
ACP1: The ACP SHOULD provide robust connectivity: As far as
possible, it should be independent of configured addressing,
configuration and routing. Requirements 2 and 3 build on this
requirement, but also have value on their own.
ACP2: The ACP MUST have a separate address space from the data-
plane. Reason: traceability, debug-ability, separation from
data-plane, security (can block easily at edge).
ACP3: The ACP MUST use autonomically managed address space. Reason:
easy bootstrap and setup ("autonomic"); robustness (admin
can't mess things up so easily). This document suggests to
use ULA addressing for this purpose ("Unique Local Address",
see [RFC4193]).
ACP4: The ACP MUST be generic. Usable by all the functions and
protocols of the AN infrastructure. It MUST NOT be tied to a
particular application or transport protocol.
ACP5: The ACP MUST provide security: Messages coming through the ACP
MUST be authenticated to be from a trusted node, and SHOULD
(very strong SHOULD) be encrypted.
The ACP operates hop-by-hop, because this interaction can be built on
IPv6 link local addressing, which is autonomic, and has no dependency
on configuration (requirement 1). It may be necessary to have ACP
connectivity across non-ACP nodes, for example to link ACP nodes over
the general Internet. This is possible, but introduces a dependency
against stable/resilient routing over the non-ACP hops (see
Section 8.2).
5. Overview
The Autonomic Control Plane is constructed in the following way (for
details, see Section 6):
1. An ACP node creates a VRF ("Virtual Routing and Forwarding")
instance, or a similar virtual context.
Behringer, et al. Expires April 15, 2018 [Page 12]
Internet-Draft An Autonomic Control Plane (ACP) October 2017
2. It determines, following a policy, a candidate peer list. This
is the list of nodes to which it should establish an Autonomic
Control Plane. Default policy is: To all link-layer adjacent
nodes supporting ACP.
3. For each node in the candidate peer list, it authenticates that
node and negotiates a mutually acceptable channel type.
4. It then establishes a secure tunnel of the negotiated channel
type. These tunnels are placed into the previously set up VRF.
This creates an overlay network with hop-by-hop tunnels.
5. Inside the ACP VRF, each node sets up a loopback interface with
its ULA IPv6 address.
6. Each node runs a lightweight routing protocol, to announce
reachability of the virtual addresses inside the ACP (see
Section 6.12.5).
Note:
o Non-autonomic NMS ("Network Management Systems") or SDN
controllers have to be manually connected into the ACP.
o Connecting over non-ACP Layer-3 clouds initially requires a tunnel
between ACP nodes.
o None of the above operations (except manual ones) is reflected in
the configuration of the node.
The following figure illustrates the ACP.
ACP node 1 ACP node 2
................... ...................
secure . . secure . . secure
tunnel : +-----------+ : tunnel : +-----------+ : tunnel
..--------| ACP VRF |---------------------| ACP VRF |---------..
: / \ / \ <--routing--> / \ / \ :
: \ / \ / \ / \ / :
..--------| loopback |---------------------| loopback |---------..
: | interface | : : | interface | :
: +-----------+ : : +-----------+ :
: : : :
: data-plane :...............: data-plane :
: : link : :
:.................: :.................:
Figure 1
Behringer, et al. Expires April 15, 2018 [Page 13]
Internet-Draft An Autonomic Control Plane (ACP) October 2017
The resulting overlay network is normally based exclusively on hop-
by-hop tunnels. This is because addressing used on links is IPv6
link local addressing, which does not require any prior set-up. This
way the ACP can be built even if there is no configuration on the
node, or if the data-plane has issues such as addressing or routing
problems.
6. Self-Creation of an Autonomic Control Plane (ACP) (Normative)
This section describes the components and steps to set up an
Autonomic Control Plane (ACP), and highlights the key properties
which make it "indestructible" against many inadvertent changes to
the data-plane, for example caused by misconfigurations.
An ACP node can be a router, switch, controller, NMS host, or any
other IP capable node. Initially, it must have a certificate, as
well as an (empty) ACP Adjacency Table (described in Section 6.2).
It then can start to discover ACP neighbors and build the ACP. This
is described step by step in the following sections:
6.1. ACP Domain, Certificate and Network
ACP relies on group security. An ACP domain is a group of nodes that
trust each other to participate in ACP operations. To establish
trust, the ACP requires certificates: An ACP node MUST have keying
material consisting of a certificate (LDevID), with which it can
cryptographically assert its membership in the ACP domain and trust
anchor(s) associated with that certificate with which it can verify
the membership of other nodes (see Section 6.1.2). The certificate
is called the ACP domain certificate, the trust anchor(s) are the CA
("Certificate Authority") of the ACP domain.
The ACP does not mandate specific mechanisms by which this keying
material is provisioned into the ACP node, it only requires the
following ACP specific information field in its domain certificate as
well as those of candidate ACP peers. See Section 10.1 for more
information about enrollment or provisioning options.
Note: LDevID ("Local Device IDentification") is the term used to
indicate a certificate that was provisioned by the owner of a node as
opposed to IDevID ("Initial Device IDentifier") that may has been
loaded on the node during manufacturing time. Those IDevID do not
include owner and deployment specific information to allows autonomic
establishment of trust for the operations of an ACP domain (e.g.:
between two ACP nodes without relying on any third party).
This document uses the term ACP in many places where its reference
document use the word autonomic. This is done because those
Behringer, et al. Expires April 15, 2018 [Page 14]
Internet-Draft An Autonomic Control Plane (ACP) October 2017
reference document consider fully autonomic network and nodes, but
support of ACP does not require support for other components of
autonomic networks. Therefore the word autonomic would be irritating
to operators interested in only the ACP:
[RFC7575] defines the term "Autonomic Domain" as a collection of
autonomic nodes. ACP nodes do not need to be fully autonomic, but
when they are, then the ACP domain is an autonomic domain. Likewise,
[I-D.ietf-anima-reference-model] defines the term "Domain
Certificate" as the certificate used in an autonomic domain. The ACP
domain certificate is that domain certificate when ACP nodes are
(fully) autonomic nodes. Finally, this document uses the term ACP
network to refer to the network created by active ACP nodes in an ACP
domain. The ACP network itself can extend beyond ACP nodes through
the mechanisms described in Section 8.1).
The ACP domain certificate can and should be used for any
authentication between ACP nodes where the required security is
domain membership. Section 6.1.2 defines this "ACP domain membership
check". The uses of this check that are standardized in this
document are for the establishment of ACP secure channels
(Section 6.6) and for ACP GRASP (Section 6.8.2). Other uses are
subject to future work, but it is recommended that it is the default
security check for any end-to-end connections between ASA. It is
equally useable by other functions such as legacy OAM functions.
6.1.1. Certificate Domain Information Field
Information about the domain MUST be encoded in the domain
certificate in a subjectAltName / rfc822Name field according to the
following ABNF definition ([RFC5234]):
[RFC Editor: Please substitute SELF in all occurences of rfcSELF with
the RFC number assigned to this document and remove this comment
line]
domain-information = local-part "@" domain
local-part = key "." local-info
key = "rfcSELF"
local-info = [ acp-address ] [ "+" rsub extensions ]
acp-address = 32hex-dig
hex-dig = DIGIT / "a" / "b" / "c" / "d" / "e" / "f"
Behringer, et al. Expires April 15, 2018 [Page 15]
Internet-Draft An Autonomic Control Plane (ACP) October 2017
rsub = [ domain-name ] ; empty if not used
domain = domain-name
routing-subdomain = [ rsub " ." ] domain
domain-name = ; <domain> according to section 3.5 of [RFC1034]
extensions = *( "+" extension )
extension = ; future definition. Must fit into [RFC5322] simple dot-
atom format.
Example:
domain-information = rfcSELF+fda379a6f6ee00000200000064000000+area5
1.research@acp.example.com
routing-subdomain = area51.research.acp.example.com
"acp-address" MUST be the ACP address of the node. It is optional to
support variations of the ACP mechanisms, for example other means for
nodes to assign ACP addresses to themselves. Such methods are
subject to future work though.
Note: "acp-address" cannot use standard IPv6 address formats because
it must match the simple dot-atom format of [RFC5322]. ":" are not
allowed in that format.
"domain" is used to indicate the ACP Domain across which all ACP
nodes trust each other and are willing to build ACP channel to each
other. See Section 6.1.2. Domain SHOULD be the FQDN of a domain
owned by the operator assigning the certificate. This is a simple
method to ensure that the domain is globally unique and collision of
ACP addresses would therefore only happen due to ULA hash collisions.
If the operator does not own any FQDN, it should choose a string in
FQDN format that intends to be equally unique.
"routing-subdomain" is the autonomic subdomain that is used to
calculate the hash for the ULA prefix of the ACP address of the node.
"rsub" is optional and should only be used when its impacts are
understood. When "rsub" is not used, "routing-subdomain" is the same
as "domain".
The optional "extensions" field is used for future extensions to this
specification. It MUST be ignored if present and not understood.
Behringer, et al. Expires April 15, 2018 [Page 16]
Internet-Draft An Autonomic Control Plane (ACP) October 2017
Note that the maximum size of "domain-information" is 254 characters
and the maximum size of node-info is 64 characters according to
[RFC5280] that is referring to [RFC2821] (superseded by [RFC5321]).
The subjectAltName / rfc822Name encoding of the ACP domain name and
ACP address is used for the following reasons:
o There are a wide range of pre-existing protocols/services where
authentication with LDevID is desirable. Enrolling and
maintaining separate LDevIDs for each of these protocols/services
is often undesirable overhead. Therefore, the information element
required for the ACP in the domain certificate should be encoded
in a way that minimizes the possibility of creating
incompatibilities with such other uses beside the authentication
for the ACP.
o The elements in the LDevID required for the ACP should not cause
incompatibilities with any pre-existing ASN.1 software potentially
in use in those other pre-existing SW systems. This eliminates
the use of novel information elements because those require
extensions to those pre-existing ASN.1 parsers.
o subjectAltName / rfc822Name is a pre-existing element that must be
supported by all existing ASN.1 parsers for LDevID.
o The elements in the LDevID required for the ACP should also not be
misinterpreted by any pre-existing protocol/service that might use
the LDevID. If the elements used for the ACP are interpreted by
other protocols/services, then the impact should be benign.
o Using an IP address format encoding could result in non-benign
misinterpretation of the domain information field; other protocol/
services unaware of the ACP could try to do something with the ACP
address that would fail to work correctly. For example, the
address could be interpreted to be an address of the node in a VRF
other than the ACP VRF.
o At minimum, both the AN domain name and the non-domain name
derived part of the ACP address need to be encoded in one or more
appropriate fields of the certificate, so there are not many
alternatives with pre-existing fields where the only possible
conflicts would likely be beneficial.
o rfc822Name encoding is quite flexible. We choose to encode the
full ACP address AND the domain name with sub part into a single
rfc822Name information element it, so that it is easier to
examine/use the "domain information field".
Behringer, et al. Expires April 15, 2018 [Page 17]
Internet-Draft An Autonomic Control Plane (ACP) October 2017
o The format of the rfc822Name is chosen so that an operator can set
up a mailbox called rfcSELF@<domain> that would receive emails
sent towards the rfc822Name of any node inside a domain. This is
possible because in many modern mail systems, components behind a
"+" character are considered part of a single mailbox. In other
words, it is not necessary to set up a separate mailbox for every
ACP node, but only one for the whole domain.
o In result, if any unexpected use of the ACP addressing information
in a certificate happens, it is benign and detectable: it would be
mail to that mailbox.
See section 4.2.1.6 of [RFC5280] for details on the subjectAltName
field.
6.1.2. ACP domain membership check
The following points constitute the ACP domain membership check:
o The peer certificate is valid as proven by the security
associations protocol exchange.
o The peers certificate is signed by one of the trust anchors
associated with the ACP domain certificate.
o If the node certificates indicate a CDP (or OCSP) then the peer's
certificate must be valid according to those criteria. e.g.: OCSP
check across the ACP or not listed in the CRL retrieved from the
CDP.
o The peers certificate has a syntactically valid domain information
field (subjectAltName / rfc822Name) and the domain name in that
peers domain information field is the same as in this ACP node
certificate. Note that future Intent rules may modify this. See
Section 10.7.
6.1.3. Certificate Maintenance
ACP nodes MUST support certificate renewal via EST ("Enrollment over
Secure Transport", see [RFC7030]) and MAY support other mechanisms.
An ACP network must have at least one ACP node supporting EST server
functionality across the ACP so that EST renewal is useable. The
mechanism by which the domain certificate was initially provisioned
SHOULD provide a mechanism to store the URL of one EST server with
its ACP address into the node for later renewal. This server does
not have to be the same as the one performing the initial certificate
enrolment.
Behringer, et al. Expires April 15, 2018 [Page 18]
Internet-Draft An Autonomic Control Plane (ACP) October 2017
ACP nodes that are EST servers MUST announce their service via GRASP
in the ACP through M_FLOOD messages:
Example:
[M_FLOOD, 12340815, h'fda379a6f6ee0000200000064000001', 210000,
["SRV.est", 4, 255, "EST-TLS"],
[O_IPv6_LOCATOR,
h'fda379a6f6ee0000200000064000001', TCP, 80]
]
The formal CDDL definition is:
flood-message = [M_FLOOD, session-id, initiator, ttl,
+[objective, (locator-option / [])]]
objective = ["SRV.est", objective-flags, loop-count,
objective-value]
objective-flags = sync-only ; as in GRASP spec
sync-only = 4 ; M_FLOOD only requires synchronization
loop-count = 255 ; recommended
objective-value = text ; name of the (list of) of supported
; protocols: "EST-TLS" for RFC7030.
The objective value "SRV.est" indicates that the objective is an
[RFC7030] compliant EST server.
The M_FLOOD message MUST be sent periodically. The default SHOULD be
60 seconds, the value SHOULD be operator configurable. It must be so
high that the aggregate amount of periodic M_FLOODs from all flooded
objectives causes only negligible traffic across the ACP. The ttl
parameter SHOULD be 3.5 times the period so that up to three
consecutive messages can be dropped before considering an
announcement expired. In the example above, the ttl is 210000 msec,
3.5 times 60 seconds.
Domain certificates SHOULD by default be renewed 50% into their
lifetime. When performing renewal, the node SHOULD attempt to
connect to the remembered EST server. If that fails, it SHOULD
attempt to connect to EST server(s) learned via GRASP. The server
with which certificate renewal succeeds SHOULD be remembered for the
next renewal.
Remembering the last renewal server and preferring it provides
stickiness which can help diagnostics. It also provides some
protection against off-path compromised ACP members announcing bogus
information into GRASP.
Behringer, et al. Expires April 15, 2018 [Page 19]
Internet-Draft An Autonomic Control Plane (ACP) October 2017
The ACP node MUST support CRLs ("Certificate Revocation Lists") via
HTTPs from one or more CDPs ("CRL Distribution Points"). These CDPs
MUST be indicated in the Domain Certificate when used. If the CDP
URL uses an IPv6 ULA, the ACP node will try to reach it via the ACP.
In that case the ACP address in the domain certificate of the CDP as
learned by the ACP node during the HTTPs TLS handshake SHOULD match
that ULA address in the HTTPs URL.
Renewal of certificates SHOULD start after less than 50% of the
domain certificate lifetime so that network operations has ample time
to investigate and resolve any problems that cause a node to not
renew its domain certificate in time - and to allow prolonged periods
of running parts of a network disconnected from any CA.
Certificate lifetime should be set to be as short as feasible. Given
how certificate renewal is fully automated via ACP and EST, the
primarily limiting factor for shorter certificate lifetimes (than the
typical one year) is load on the EST server(s) and CA. It is
therefore recommended that ACP domain certificates are managed via a
CA chain where the assigning CA has enough performance to manage
short lived certificates.
See Section 10.1 for further optimizations of certificate maintenance
when BRSKI can be used ("Bootstrapping Remote Secure Key
Infrastructures", see [I-D.ietf-anima-bootstrapping-keyinfra]).
6.2. ACP Adjacency Table
To know to which nodes to establish an ACP channel, every ACP node
maintains an adjacency table. The adjacency table contains
information about adjacent ACP nodes, at a minimum: node-ID, Link-
local IPv6 address (discovered by GRASP as explained below), domain,
certificate. An ACP node MUST maintain this adjacency table up to
date. This table is used to determine to which neighbor an ACP
connection is established.
Where the next ACP node is not directly adjacent, the information in
the adjacency table can be supplemented by configuration. For
example, the node-ID and IP address could be configured.
The adjacency table MAY contain information about the validity and
trust of the adjacent ACP node's certificate. However, subsequent
steps MUST always start with authenticating the peer.
The adjacency table contains information about adjacent ACP nodes in
general, independently of their domain and trust status. The next
step determines to which of those ACP nodes an ACP connection should
be established.
Behringer, et al. Expires April 15, 2018 [Page 20]
Internet-Draft An Autonomic Control Plane (ACP) October 2017
Interaction between ACP and other autonomic elements like GRASP (see
below) or ASAs should be via an API that allows (appropriately access
controlled) read/write access to the ACP Adjacency Table.
Specification of such an API is subject to future work.
6.3. Neighbor Discovery with DULL GRASP
The ACP uses one instance of DULL GRASP ( See section 3.5.2.2 of
[I-D.ietf-anima-grasp] for its formal definition) for every physical
L2 subnet of the ACP node to discover physically adjacent candidate
ACP neighbors. Native interfaces (e.g.: physical interfaces on
physical nodes) SHOULD be brought up automatically enough so that ACP
discovery can be performed and any native interfaces with ACP
neighbors can then be brought into the ACP even if the interface is
otherwise not configured. Reception of packets on such otherwise not
configured interfaces MUST be limited so that at first only IPv6
link-local address assignment (SLAAC) and DULL GRASP works and then
only the following ACP secure channel setup packets - but not any
other unnecessary traffic (e.g.: no other link-local IPv6 transport
stack responders for example).
Note that the use of the IPv6 link-local multicast address
(ALL_GRASP_NEIGHBORS) implies the need to use MLD ([RFC3810]) to
announce the desire to receive packets for that address. Otherwise
DULL GRASP could fail to operate correctly in the presence of MLD
snooping, non-ACP enabled L2 switches - because those would stop
forwarding DULL GRASP packets. Switches not supporting MLD snooping
simply need to operate as pure L2 bridges for IPv6 multicast packets
for DULL GRASP to work.
ACP discovery SHOULD NOT be enabled by default on non-native
interfaces. In particular, ACP discovery MUST NOT run inside the ACP
across ACP virtual interfaces. See Section 10.3 for further, non-
normative suggestions how to enable/disable ACP at node and interface
level. See Section 8.2.2 for more details about tunnels (typical
non-native interfaces). See Section 7 for how ACP should be extended
on devices operating (also) as L2 bridges.
Note: If an ACP node also implements BRSKI (see Section 10.1) then
the above considerations also apply to discovery for BRSKI. Each
DULL instance of GRASP set up for ACP is then also used for the
discovery of a bootstrap proxy via BRSKI when the node does not have
a domain certificate. Discovery of ACP neighbors happens only when
the node does have the certificate. The node therefore never needs
to discover both a bootstrap proxy and ACP neighbor at the same time.
An ACP node announces itself to potential ACP peers by use of the
"AN_ACP" objective. This is a synchronization objective intended to
Behringer, et al. Expires April 15, 2018 [Page 21]
Internet-Draft An Autonomic Control Plane (ACP) October 2017
be flooded on a single link using the GRASP Flood Synchronization
(M_FLOOD) message. In accordance with the design of the Flood
message, a locator consisting of a specific link-local IP address, IP
protocol number and port number will be distributed with the flooded
objective. An example of the message is informally:
Example:
[M_FLOOD, 12340815, h'fe80000000000000c0011001FEEF0000, 180000,
["AN_ACP", 4, 1, "IKEv2"],
[O_IPv6_LOCATOR,
h'fe80000000000000c0011001FEEF0000, UDP, 15000]
]
The formal CDDL definition is:
flood-message = [M_FLOOD, session-id, initiator, ttl,
+[objective, (locator-option / [])]]
objective = ["AN_ACP", objective-flags, loop-count,
objective-value]
objective-flags = sync-only ; as in the GRASP specification
sync-only = 4 ; M_FLOOD only requires synchronization
loop-count = 1 ; limit to link-local operation
objective-value = text ; name of the (list of) secure
; channel negotiation protocol(s)
The objective-flags field is set to indicate synchronization.
The loop-count is fixed at 1 since this is a link-local operation.
In the above (recommended) example the period of sending of the
objective could be 60 seconds the indicated ttl of 180000 msec means
that the objective would be cached by ACP nodes even when two out of
three messages are dropped in transit.
The session-id is a random number used for loop prevention
(distinguishing a message from a prior instance of the same message).
In DULL this field is irrelevant but must still be set according to
the GRASP specification.
The originator MUST be the IPv6 link local address of the originating
ACP node on the sending interface.
The 'objective-value' parameter is (normally) a string indicating the
secure channel protocol available at the specified or implied
locator.
Behringer, et al. Expires April 15, 2018 [Page 22]
Internet-Draft An Autonomic Control Plane (ACP) October 2017
The locator is optional and only required when the secure channel
protocol is not offered at a well-defined port number, or if there is
no well-defined port number. "IKEv2" is the abbreviation for
"Internet Key Exchange protocol version 2", as defined in [RFC7296].
It is the main protocol used by the Internet IP security architecture
("IPsec", see [RFC4301]). We therefore use the term "IKEv2" and not
"IPsec" in the GRASP definitions below and example above. "IKEv2"
has a well-defined port number 500, but in the above example, the
candidate ACP neighbor is offering ACP secure channel negotiation via
IKEv2 on port 15000 (for the sake of creating a non-standard
example).
If a locator is included, it MUST be an O_IPv6_LOCATOR, and the IPv6
address MUST be the same as the initiator address (these are DULL
requirements to minimize third party DoS attacks).
The secure channel methods defined in this document use the objective
values of "IKEv2" and "dTLS". There is no distinction between IKEv2
native and GRE-IKEv2 because this is purely negotiated via IKEv2.
A node that supports more than one secure channel protocol needs to
flood multiple versions of the "AN_ACP" objective, each accompanied
by its own locator. This can be in a single GRASP M_FLOOD message.
If multiple secure channel protocols are supported that all are run
on well-defined ports, then they can be announced via a single AN_ACP
objective using a list of string names as the objective value without
a following locator-option.
Note that a node serving both as an ACP node and BRSKI Join Proxy may
choose to distribute the "AN_ACP" objective and the respective BRSKI
in the same M_FLOOD message, since GRASP allows multiple objectives
in one message. This may be impractical though if ACP and BRSKI
operations are implemented via separate software modules / ASAs.
The result of the discovery is the IPv6 link-local address of the
neighbor as well as its supported secure channel protocols (and non-
standard port they are running on). It is stored in the ACP
Adjacency Table, see Section 6.2 which then drives the further
building of the ACP to that neighbor.
6.4. Candidate ACP Neighbor Selection
An ACP node must determine to which other ACP nodes in the adjacency
table it should build an ACP connection. This is based on the
information in the ACP Adjacency table.
Behringer, et al. Expires April 15, 2018 [Page 23]
Internet-Draft An Autonomic Control Plane (ACP) October 2017
The ACP is by default established exclusively between nodes in the
same domain. This includes all routing subdomains. Section 10.7
explains how ACP connections across multiple routing subdomains are
special.
Future extensions to this document including Intent can change this
default behavior. Examples include:
o Build the ACP across all domains that have a common parent domain.
For example ACP nodes with domain "example.com", nodes of
"example.com", "access.example.com", "core.example.com" and
"city.core.example.com" could all establish one single ACP.
o ACP connections across domains with different CA (certificate
authorities) could establish a common ACP by installing the
alternate domains' CA into the trusted anchor store. This is an
executive management action that could easily be accomplished
through the control channel created by the ACP.
Since Intent is transported over the ACP, the first ACP connection a
node establishes is always following the default behavior. See
Section 10.7 for more details.
The result of the candidate ACP neighbor selection process is a list
of adjacent or configured autonomic neighbors to which an ACP channel
should be established. The next step begins that channel
establishment.
6.5. Channel Selection
To avoid attacks, initial discovery of candidate ACP peers cannot
include any non-protected negotiation. To avoid re-inventing and
validating security association mechanisms, the next step after
discovering the address of a candidate neighbor can only be to try
first to establish a security association with that neighbor using a
well-known security association method.
At this time in the lifecycle of ACP nodes, it is unclear whether it
is feasible to even decide on a single MTI (mandatory to implement)
security association protocol across all ACP nodes:
From the use-cases it seems clear that not all type of ACP nodes can
or need to connect directly to each other or are able to support or
prefer all possible mechanisms. For example, code space limited IoT
devices may only support dTLS ("datagram Transport Layer Security
version 1.2", see [RFC6347]) because that code exists already on them
for end-to-end security, but low-end in-ceiling L2 switches may only
want to support MacSec because that is also supported in their chips.
Behringer, et al. Expires April 15, 2018 [Page 24]
Internet-Draft An Autonomic Control Plane (ACP) October 2017
Only a flexible gateway device may need to support both of these
mechanisms and potentially more.
To support extensible secure channel protocol selection without a
single common MTI protocol, ACP nodes must try all the ACP secure
channel protocols it supports and that are feasible because the
candidate ACP neighbor also announced them via its AN_ACP GRASP
parameters (these are called the "feasible" ACP secure channel
protocols).
To ensure that the selection of the secure channel protocols always
succeeds in a predictable fashion without blocking, the following
rules apply:
An ACP node may choose to attempt initiate the different feasible ACP
secure channel protocols it supports according to its local policies
sequentially or in parallel, but it MUST support acting as a
responder to all of them in parallel.
Once the first secure channel protocol succeeds, the two peers know
each other's certificates because it must be used by all secure
channel protocols for mutual authentication. The node with the lower
Node-ID in the ACP address becomes Bob, the one with the higher Node-
ID in the certificate Alice.
Bob becomes passive, he does not attempt to further initiate ACP
secure channel protocols with Alice and does not consider it to be an
error when Alice closes secure channels. Alice becomes the active
party, continues to attempt setting up secure channel protocols with
Bob until she arrives at the best one from her view that also works
with Bob.
For example, originally Bob could have been the initiator of one ACP
secure channel protocol that Bob prefers and the security association
succeeded. The roles of Bob and Alice are then assigned. At this
stage, the protocol may not even have completed negotiating a common
security profile. The protocol could for example could have been
IPsec via IKEv2 ("IP security", see [RFC4301] and "Internet Key
Exchange protocol version 2", see [RFC7296]. It is now up to Alice
to decide how to proceed. Even if the IPsec connecting determined a
working profile with Bob, Alice might prefer some other secure
protocol (e.g.: dTLS) and try to set that up with Bob. If that
succeeds, she would close the IPsec connection. If no better
protocol attempt succeeds, she would keep the IPsec connection.
All this negotiation is in the context of an "L2 interface". Alice
and Bob will build ACP connections to each other on every "L2
interface" that they both connect to. An autonomic node must not
Behringer, et al. Expires April 15, 2018 [Page 25]
Internet-Draft An Autonomic Control Plane (ACP) October 2017
assume that neighbors with the same L2 or link-local IPv6 addresses
on different L2 interfaces are the same node. This can only be
determined after examining the certificate after a successful
security association attempt.
6.6. Candidate ACP Neighbor verification
Independent of the security association protocol chosen, candidate
ACP neighbors need to be authenticated based on their domain
certificate. This implies that any secure channel protocol MUST
support certificate based authentication that can support the ACP
domain membership check as defined in Section 6.1.2. If it fails,
the connection attempt is aborted and an error logged (with
throttling).
6.7. Security Association protocols
The following sections define the security association protocols that
we consider to be important and feasible to specify in this document:
6.7.1. ACP via IKEv2
An ACP node announces its ability to support IKEv2 as the ACP secure
channel protocol in GRASP as "IKEv2".
6.7.1.1. Native IPsec
To run ACP via IPsec natively, no further IANA assignments/
definitions are required. An ACP node supporting native IPsec MUST
use IPsec security setup via IKEv2, tunnel mode, local and peer link-
local IPv6 addresses used for encapsulation, ESP with AES256 for
encryption and SHA256 hash.
In terms of IKEv2, this means the initiator will offer to support
IPsec tunnel mode with next protocol equal 41 (IPv6).
IPsec tunnel mode is required because the ACP will route/forward
packets received from any other ACP node across the ACP secure
channels, and not only its own generated ACP packets. With IPsec
transport mode, it would only be possible to send packets originated
by the ACP node itself.
ESP is used because ACP mandates the use of encryption for ACP secure
channels.
Behringer, et al. Expires April 15, 2018 [Page 26]
Internet-Draft An Autonomic Control Plane (ACP) October 2017
6.7.1.2. IPsec with GRE encapsulation
In network devices it is often more common to implement high
performance virtual interfaces on top of GRE encapsulation than on
top of a "native" IPsec association (without any other encapsulation
than those defined by IPsec). On those devices it may be beneficial
to run the ACP secure channel on top of GRE protected by the IPsec
association.
To run ACP via GRE/IPsec, no further IANA assignments/definitions are
required. The ACP node MUST support IPsec security setup via IKEv2,
IPsec transport mode, local and peer link-local IPv6 addresses used
for encapsuation, ESP with AES256 encryption and SHA256 hash.
When GRE is used, transport mode is sufficient because the routed ACP
packets are not "tunneled" by IPsec but rather by GRE: IPsec only has
to deal with the GRE/IP packet which always uses the local and peer
link-local IPv6 addresses and is therefore applicable to transport
mode.
ESP is used because ACP mandates the use of encryption for ACP secure
channels.
In terms of IKEv2 negotiation, this means the initiator must offer to
support IPsec transport mode with next protocol equal to GRE (47)
followed by the offer for native IPsec as described above (because
that option is mandatory to support).
If IKEv2 initiator and responder support GRE, it will be selected.
The version of GRE to be used must the according to [RFC7676].
6.7.2. ACP via dTLS
We define the use of ACP via dTLS in the assumption that it is likely
the first transport encryption code basis supported in some classes
of constrained devices.
To run ACP via UDP and dTLS v1.2 [RFC6347] a locally assigned UDP
port is used that is announced as a parameter in the GRASP AN_ACP
objective to candidate neighbors. All ACP nodes supporting dTLS as a
secure channel protocol MUST support AES256 encryption and not permit
weaker crypto options.
There is no additional session setup or other security association
besides this simple dTLS setup. As soon as the dTLS session is
functional, the ACP peers will exchange ACP IPv6 packets as the
payload of the dTLS transport connection. Any dTLS defined security
Behringer, et al. Expires April 15, 2018 [Page 27]
Internet-Draft An Autonomic Control Plane (ACP) October 2017
association mechanisms such as re-keying are used as they would be
for any transport application relying solely on dTLS.
6.7.3. ACP Secure Channel Requirements
A baseline ACP node MUST support IPsec natively and MAY support IPsec
via GRE. A constrained ACP node MUST support dTLS. ACP nodes
connecting constrained areas with baseline areas MUST therefore
support IPsec and dTLS.
ACP nodes need to specify in documentation the set of secure ACP
mechanisms they support.
An ACP secure channel MUST immediately be terminated when the
lifetime of any certificate in the chain used to authenticate the
neighbor expires or becomes revoked. Note that this is not standard
behavior in secure channel protocols such as IPsec because the
certificate authentication only influences the setup of the secure
channel in these protocols.
6.8. GRASP in the ACP
6.8.1. GRASP as a core service of the ACP
The ACP MUST run an instance of GRASP inside of it. It is a key part
of the ACP services. They function in GRASP that makes it
fundamental as a service is the ability for ACP wide service
discovery (called objectives in GRASP). In most other solution
designs such distributed discovery does not exist at all or was added
as an afterthought and relied upon inconsistently.
ACP provides IP unicast routing via the RPL routing protocol
(described below).
The ACP does not use IP multicast routing nor does it provide generic
IP multicast services. Instead, the ACP provides service discovery
via the objective discovery/announcement and negotiation mechanisms
of the ACP GRASP instance (services are a form of objectives). These
mechanisms use hop-by-hop reliable flooding of GRASP messages for
both service discovery (GRASP M_DISCOVERY messages) and service
announcement (GRASP M_FLOOD messages).
IP multicast is not used by the ACP because the ANI (Autonomic
Networking Infrastructure) itself does not require IP multicast but
only service announcement/discovery. Using IP multicast for that
would have made it necessary to develop a zero-touch autoconfiguring
solution for ASM (Any Source Multicast - original form of IP
multicast defined in [RFC1112]), which would be quite complex and
Behringer, et al. Expires April 15, 2018 [Page 28]
Internet-Draft An Autonomic Control Plane (ACP) October 2017
difficult to justify. One aspect of complexity that has never been
attempted to be solved in IETF documents is the automatic-selection
of routers that should be PIM-SM rendezvous points (RPs) (see
[RFC7761]). The other aspects of complexity are the implementation
of MLD ([RFC4604]), PIM-SM and Anycast-RP (see [RFC4610]). If those
implementations already exist in a product, then they would be very
likely tied to accelerated forwarding which consumes hardware
resources, and that in return is difficult to justify as a cost of
performing only service discovery.
Future ASA may need high performance in-network data replication.
That is the case when the use of IP multicast is justified. These
ASA can then use service discovery from ACP GRASP, and then they do
not need ASM but only SSM (Source Specific Multicast, see [RFC4607])
for the IP multicast replication. SSM itself can simply be enabled
in the data-plane (or even in an update to the ACP) without any other
configuration than just enabling it on all nodes and only requires a
simpler version of MLD (see [RFC5790]).
LSP (Link State Protocol) based IGP routing protocols typically have
a mechanism to flood information, and such a mechanism could be used
to flood GRASP objectives by defining them to be information of that
IGP. This would be a possible optimization in future variations of
the ACP that do use an LSP routing protocol. Note though that such a
mechanism would not work easily for GRASP M_DISCOVERY messages which
are constrained flooded up to a node where a responder is found. We
do expect that many future services in ASA will have only few
consuming ASA, and for those cases, M_DISCOVERY is the more efficient
method than flooding across the whole domain.
Because the ACP uses RPL, one desirable future extension is to use
RPLs existing notion of loop-free distribution trees (DODAG) to make
GRASPs flooding more efficient both for M_FLOOD and M_DISCOVERY) See
Section 6.12.5 how this will be specifically beneficial when using
NBMA interfaces. This is not currently specified in this document
because it is not quite clear yet what exactly the implications are
to make GRASP flooding depend on RPL DODAG convergence and how
difficult it would be to let GRASP flooding access the DODAG
information.
6.8.2. ACP as the Security and Transport substrate for GRASP
In the terminology of GRASP ([I-D.ietf-anima-grasp]), the ACP is the
security and transport substrate for the GRASP instance run inside
the ACP ("ACP GRASP").
This means that the ACP is responsible to ensure that this instance
of GRASP is only sending messages across the ACP GRASP virtual
Behringer, et al. Expires April 15, 2018 [Page 29]
Internet-Draft An Autonomic Control Plane (ACP) October 2017
interfaces. Whenever the ACP adds or deletes such an interface
because of new ACP secure channels or loss thereof, the ACP needs to
indicate this to the ACP instance of GRASP. The ACP exists also in
the absence of any active ACP neighbors. It is created when the node
has a domain certificate. In this case ASAs using GRASP running on
the same node would still need to be able to discover each other's
objectives. When the ACP does not exist, ASAs leveraging the ACP
instance of GRASP via APIs MUST still be able to operate, and MUST be
able to understand that there is no ACP and that therefore the ACP
instance of GRASP can not operate.
The way ACP acts as the security and transport substrate for GRASP is
visualized in the following picture:
[RFC Editor: please try to put the following picture on a single page
and remove this note. We cannot figure out how to do this with XML.
The picture does fit on a single page.]
ACP:
...............................................................
. .
. /-GRASP-flooding-\ ACP GRASP instance .
. / \ .
. GRASP GRASP GRASP .
. link-local unicast link-local .
. multicast messages multicast .
. messages | messages .
. | | | .
...............................................................
. v v v ACP security and transport .
. | | | substrate for GRASP .
. | | | .
. | ACP GRASP | - ACP GRASP .
. | loopback | loopback interface .
. | interface | - AN-cert auth .
. | TLS | .
. ACP GRASP | ACP GRASP - ACP GRASP virtual .
. subnet1 | subnet2 virtual interfaces .
. TCP | TCP .
. | | | .
...............................................................
. | | | ^^^ Users of ACP (GRASP/ASA) .
. | | | ACP interfaces/addressing .
. | | | .
. | | | .
. | ACP-loopback Interf.| <- ACP loopback interface .
. | ACP-address | - address (global ULA) .
. subnet1 | subnet2 <- ACP virtual interfaces .
Behringer, et al. Expires April 15, 2018 [Page 30]
Internet-Draft An Autonomic Control Plane (ACP) October 2017
. link-local | link-local - link-local addresses .
...............................................................
. | | | ACP routing and forwarding .
. | RPL-routing | .
. | /IP-Forwarding\ | .
. | / \ | .
. ACP IPv6 packets ACP IPv6 packets .
. |/ \| .
. IPsec/dTLS IPsec/dTLS - AN-cert auth .
...............................................................
| | data-plane
| |
| | - ACP secure channel
link-local link-local - encap addresses
subnet1 subnet2 - data-plane interfaces
| |
ACP-Nbr1 ACP-Nbr2
Figure 2
GRASP unicast messages inside the ACP always use the ACP address.
Link-local ACP addresses must not be used inside objectives. GRASP
unicast messages inside the ACP are transported via TLS 1.2
([RFC5246]) connections with AES256 encryption and SHA256. Mutual
authentication uses the ACP domain membership check defined in
(Section 6.1.2).
GRASP link-local multicast messages are targeted for a specific ACP
virtual interface (as defined Section 6.12.5) but are sent by the ACP
into an equally built ACP GRASP virtual interface constructed from
the TCP connection(s) to the IPv6 link-local neighbor address(es) on
the underlying ACP virtual interface. If the ACP GRASP virtual
interface has two or more neighbors, the GRASP link-local multicast
messages are replicated to all neighbor TCP connections.
TLS and TLS connections for GRASP in the ACP use the IANA assigned
TCP port for GRASP (7107). Effectively the transport stack is
expected to be TLS for connections from/to the ACP address (e.g.:
global scope address(es)) and TCP for connections from/to link-local
addresses on the ACP virtual interfaces. The latter ones are only
used for flooding of GRASP messages.
6.8.2.1. Discussion
TCP encapsulation for GRASP M_DISCOVERY and M_FLOOD link local
messages is used because these messages are flooded across
potentially many hops to all ACP nodes and a single link with even
temporary packet loss issues (e.g.: WiFi/Powerline link) can reduce
Behringer, et al. Expires April 15, 2018 [Page 31]
Internet-Draft An Autonomic Control Plane (ACP) October 2017
the probability for loss free transmission so much that applications
would want to increase the frequency with which they send these
messages. This would result in more traffic flooding than hop-by-hop
reliable retransmission as provided for by TCP.
TLS is mandated for GRASP non-link-local unicast because the ACP
secure channel mandatory authentication and encryption protects only
against attacks from the outside but not against attacks from the
inside: Compromised ACP members that have (not yet) been detected and
removed (e.g.: via domain certificate revocation / expiry).
If GRASP peer connections would just use TCP, compromised ACP members
could simply eavesdrop passively on GRASP peer connections for whom
they are on-path ("Man In The Middle" - MITM). Or intercept and
modify them. With TLS, it is not possible to completely eliminate
problems with compromised ACP members, but attacks are a lot more
complex:
Eavesdropping/spoofing by a compromised ACP node is still possible
because in the model of the ACP and GRASP, the provider and consumer
of an objective have initially no unique information (such as an
identity) about the other side which would allow them to distinguish
a benevolent from a compromised peer. The compromised ACP node would
simply announce the objective as well, potentially filter the
original objective in GRASP when it is a MITM and act as an
application level proxy. This of course requires that the
compromised ACP node understand the semantic of the GRASP negotiation
to an extend that allows it to proxy it without being detected, but
in an AN environment this is quite likely public knowledge or evens
standardized.
The GRASP TLS connections are run like any other ACP traffic through
the ACP secure channels. This leads to double authentication/
encryption. Future work optimizations could avoid this but it is
unclear how beneficial/feasible this is:
o The security considerations for GRASP change against attacks from
non-ACP (e.g.: "outside") nodes: TLS is subject to reset attacks
while secure channel protocols may be not (e.g.: IPsec is not).
o The secure channel method may leverage hardware acceleration and
there may be little or no gain in eliminating it.
o The GRASP TLS connections need to implement any additional
security options that are required for secure channels. For
example the closing of connections when the peers certificate has
expired.
Behringer, et al. Expires April 15, 2018 [Page 32]
Internet-Draft An Autonomic Control Plane (ACP) October 2017
6.9. Context Separation
The ACP is in a separate context from the normal data-plane of the
node. This context includes the ACP channels IPv6 forwarding and
routing as well as any required higher layer ACP functions.
In classical network systems, a dedicated so called "Virtual routing
and forwarding instance" (VRF) is one logical implementation option
for the ACP. If possible by the systems software architecture,
separation options that minimize shared components are preferred,
such as a logical container or virtual machine instance. The context
for the ACP needs to be established automatically during bootstrap of
a node. As much as possible it should be protected from being
modified unintentionally by ("data-plane") configuration.
Context separation improves security, because the ACP is not
reachable from the global routing table. Also, configuration errors
from the data-plane setup do not affect the ACP.
6.10. Addressing inside the ACP
The channels explained above typically only establish communication
between two adjacent nodes. In order for communication to happen
across multiple hops, the autonomic control plane requires ACP
network wide valid addresses and routing. Each ACP node must create
a loopback interface with an ACP network wide unique address inside
the ACP context (as explained in in Section 6.9). This address may
be used also in other virtual contexts.
With the algorithm introduced here, all ACP nodes in the same routing
subdomain have the same /48 ULA global ID prefix. Conversely, ULA
global IDs from different domains are unlikely to clash, such that
two networks can be merged, as long as the policy allows that merge.
See also Section 9.1 for a discussion on merging domains.
Links inside the ACP only use link-local IPv6 addressing, such that
each node only requires one routable virtual address.
6.10.1. Fundamental Concepts of Autonomic Addressing
o Usage: Autonomic addresses are exclusively used for self-
management functions inside a trusted domain. They are not used
for user traffic. Communications with entities outside the
trusted domain use another address space, for example normally
managed routable address space (called "data-plane" in this
document).
Behringer, et al. Expires April 15, 2018 [Page 33]
Internet-Draft An Autonomic Control Plane (ACP) October 2017
o Separation: Autonomic address space is used separately from user
address space and other address realms. This supports the
robustness requirement.
o Loopback-only: Only ACP loopback interfaces (and potentially those
configured for "ACP connect", see Section 8.1) carry routable
address(es); all other interfaces (called ACP virtual interfaces)
only use IPv6 link local addresses. The usage of IPv6 link local
addressing is discussed in [RFC7404].
o Use-ULA: For loopback interfaces of ACP nodes, we use Unique Local
Addresses (ULA), as specified in [RFC4193]. An alternative scheme
was discussed, using assigned ULA addressing. The consensus was
to use ULA-random [[RFC4193] with L=1], because it was deemed to
be sufficient.
o No external connectivity: They do not provide access to the
Internet. If a node requires further reaching connectivity, it
should use another, traditionally managed address scheme in
parallel.
o Addresses in the ACP are permanent, and do not support temporary
addresses as defined in [RFC4941].
o Addresses in the ACP are not considered sensitive on privacy
grounds because ACP nodes are not expected to be end-user devices.
Therefore, ACP addresses do not need to be pseudo-random as
discussed in [RFC7721]. Because they are not propagated to
untrusted (non ACP) nodes and stay within a domain (of trust), we
also consider them not to be subject to scanning attacks.
The ACP is based exclusively on IPv6 addressing, for a variety of
reasons:
o Simplicity, reliability and scale: If other network layer
protocols were supported, each would have to have its own set of
security associations, routing table and process, etc.
o Autonomic functions do not require IPv4: Autonomic functions and
autonomic service agents are new concepts. They can be
exclusively built on IPv6 from day one. There is no need for
backward compatibility.
o OAM protocols no not require IPv4: The ACP may carry OAM
protocols. All relevant protocols (SNMP, TFTP, SSH, SCP, Radius,
Diameter, ...) are available in IPv6.
Behringer, et al. Expires April 15, 2018 [Page 34]
Internet-Draft An Autonomic Control Plane (ACP) October 2017
6.10.2. The ACP Addressing Base Scheme
The Base ULA addressing scheme for ACP nodes has the following
format:
8 40 2 78
+--+-------------------------+------+------------------------------+
|fd| hash(routing-subdomain) | Type | (sub-scheme) |
+--+-------------------------+------+------------------------------+
Figure 3: ACP Addressing Base Scheme
The first 48 bits follow the ULA scheme, as defined in [RFC4193], to
which a type field is added:
o "fd" identifies a locally defined ULA address.
o The 40 bits ULA "global ID" (term from [RFC4193]) for ACP
addresses carried in the domain information field of domain
certificates are the first 40 bits of the SHA256 hash of the
routing subdomain from the same domain information field. In the
example of Section 6.1.1, the routing subdomain is
"area51.research.acp.example.com" and the 40 bits ULA "global ID"
a379a6f6ee.
o To allow for extensibility, the fact that the ULA "global ID" is a
hash of the routing subdomain SHOULD NOT be assumed by any ACP
node during normal operations. The hash function is only executed
during the creation of the certificate. If BRSKI is used then the
registrar will create the domain information field in response to
the CSR Attribute Request by the pledge.
o Type: This field allows different address sub-schemes. This
addresses the "upgradability" requirement. Assignment of types
for this field will be maintained by IANA.
The sub-scheme may imply a range or set of addresses assigned to the
node, this is called the ACP address range/set and explained in each
sub-scheme.
6.10.3. ACP Zone Addressing Sub-Scheme
The sub-scheme defined here is defined by the Type value 00b (zero)
in the base scheme.
Behringer, et al. Expires April 15, 2018 [Page 35]
Internet-Draft An Autonomic Control Plane (ACP) October 2017
64 64
+-----------------+---------+---++-----------------------------+---+
| (base scheme) | Zone-ID | Z || Node-ID |
| | | || Registrar-ID | Node-Number| V |
+-----------------+---------+---++--------------+--------------+---+
50 13 1 48 15 1
Figure 4: ACP Zone Addressing Sub-Scheme
The fields are defined as follows:
o Zone-ID: If set to all zero bits: The Node-ID bits are used as an
identifier (as opposed to a locator). This results in a non-
hierarchical, flat addressing scheme. Any other value indicates a
zone. See Section 6.10.3.1 on how this field is used in detail.
o Z: MUST be 0.
o Node-ID: A unique value for each node.
The 64 bit Node-ID is derived and composed as follows:
o Registrar-ID (48 bit): A number unique inside the domain that
identifies the registrar which assigned the Node-ID to the node.
A MAC address of the registrar can be used for this purpose.
o Node-Number: A number which is unique for a given registrar, to
identify the node. This can be a sequentially assigned number.
o V (1 bit): Virtualization bit: 0: Indicates the ACP itself ("ACP
node base system); 1: Indicates the optional "host" context on the
ACP node (see below).
In the Zone addressing sub-scheme, the ACP address in the certificate
has Zone and V fields as all zero bits. The ACP address set includes
addresses with any Zone value and any V value.
The "Node-ID" itself is unique in a domain (i.e., the Zone-ID is not
required for uniqueness). Therefore, a node can be addressed either
as part of a flat hierarchy (zone ID = 0), or with an aggregation
scheme (any other zone ID). A address with zone-ID = 0 is an
identifier, with another zone-ID as a locator. See Section 6.10.3.1
for a description of the zone bits.
The Virtual bit in this sub-scheme allows to easily add the ACP as a
component to existing systems without causing problems in the port
number space between the services in the ACP and the existing system.
Behringer, et al. Expires April 15, 2018 [Page 36]
Internet-Draft An Autonomic Control Plane (ACP) October 2017
V:0 is the ACP router (autonomous node base system), V:1 is the host
with pre-existing transport endpoints on it that could collide with
the transport endpoints used by the ACP router. The ACP host could
for example have a p2p virtual interface with the V:0 address as its
router into the ACP. Depending on the SW design of ASA (outside the
scope of this specification), they may use the V:0 or V:1 address.
The location of the V bit(s) at the end of the address allows to
announce a single prefix for each ACP node. For example, in a
network with 20,000 ACP nodes, this avoid 20,000 additional routes in
the routing table.
6.10.3.1. Usage of the Zone Field
The "Zone-ID" allows for the introduction of structure in the
addressing scheme.
Zone = zero is the default addressing scheme in an ACP domain. Every
ACP node MUST respond to its ACP address with zone=0. Used on its
own this leads to a non-hierarchical address scheme, which is
suitable for networks up to a certain size. In this case, the
addresses primarily act as identifiers for the nodes, and aggregation
is not possible.
If aggregation is required, the 13 bit value allows for up to 8192
zones. The allocation of zone numbers may either happen
automatically through a to-be-defined algorithm; or it could be
configured and maintained manually.
If a node learns through an autonomic method or through configuration
that it is part of a zone, it MUST also respond to its ACP address
with that zone number. In this case the ACP loopback is configured
with two ACP addresses: One for zone 0 and one for the assigned zone.
This method allows for a smooth transition between a flat addressing
scheme and an hierarchical one.
(Theoretically, the 13 bits for the Zone-ID would allow also for two
levels of zones, introducing a sub-hierarchy. We do not think this
is required at this point, but a new type could be used in the future
to support such a scheme.)
Note: The Zone-ID is one method to introduce structure or hierarchy
into the ACP. Another way is the use of the routing subdomain field
in the ACP that leads to different /40 ULA prefixes within an ACP
domain. This gives future work two options to consider.
Behringer, et al. Expires April 15, 2018 [Page 37]
Internet-Draft An Autonomic Control Plane (ACP) October 2017
6.10.4. ACP Manual Addressing Sub-Scheme
The sub-scheme defined here is defined by the Type value 00b (zero)
in the base scheme.
64 64
+---------------------+---------+---++-----------------------------+
| (base scheme) |Subnet-ID| Z || Interface Identifier |
+---------------------+---------+---++-----------------------------+
50 13 1
Figure 5: ACP Manual Addressing Sub-Scheme
The fields are defined as follows:
o Subnet-ID: Configured subnet identifier.
o Z: MUST be 1.
o Interface Identifier.
This sub-scheme is meant for "manual" allocation to subnets where the
other addressing schemes cannot be used. The primary use case is for
assignment to ACP connect subnets (see Section 8.1.1).
"Manual" means that allocations of the Subnet-ID need to be done
today with pre-existing, non-autonomic mechanisms. Every subnet that
uses this addressing sub-scheme needs to use a unique Subnet-ID
(unless some anycast setup is done). Future work may define
mechanisms for auto-coordination between ACP nodes and auto-
allocation of Subnet-IDs between them.
The Z field is following the Subnet-ID field so that future work
could allocate/coordinate both Zone-ID and Subnet-ID consistently and
use an integrated aggregatable routing approach across them. Z=0
(Zone sub-scheme) would then be used for network wide unique,
registrar assigned (and certificate protected) Node-IDs primarily for
ACP nodes while Z=1 would be used for node-level assigned Interface
Identifiers primarily for non-ACP-nodes (on logical subnets where the
ACP node is a router).
Manual addressing sub-scheme addresses SHOULD only be used in domain
certificates assigned to nodes that cannot fully participate in the
automatic establishment of ACP secure channels or ACP routing. The
intended use are nodes connecting to the ACP via an ACP edge node and
Behringer, et al. Expires April 15, 2018 [Page 38]
Internet-Draft An Autonomic Control Plane (ACP) October 2017
ACP connect (see Section 8.1) - such as legacy NOC equipment. They
would not use their domain certificate for ACP secure channel
creation and therefore do not need to participate in ACP routing
either. They would use the certificate for authentication of any
transport services. The value of the Interface Identifier is left
for future definitions.
6.10.5. ACP Vlong Addressing Sub-Scheme
The sub-scheme defined here is defined by the Type value 01b (one) in
the base scheme.
50 78
+---------------------++-----------------------------+----------+
| (base scheme) || Node-ID |
| || Registrar-ID | Node-Number| V |
+---------------------++--------------+--------------+----------+
46 33/17 8/16
Figure 6: ACP Vlong Addressing Sub-Scheme
This addressing scheme foregoes the Zone field to allow for larger,
flatter routed networks (e.g.: as in IoT) with more than 2^32 Node-
Numbers. It also allows for up to 2^16 - 65536 different virtualized
addresses, which could be used to address individual software
components in an ACP node.
The fields are the same as in the Zone sub-scheme with the following
refinements:
o V: Virtualization bit: Values 0 and 1 as in Zone sub-scheme,
further values use via definition in future work.
o Registrar-ID: To maximize Node-Number and V, the Registrar-ID is
reduced to 46 bits. This still allows to use the MAC address of a
registrar by removing the V and U bits from the 48 bits of a MAC
address (those two bits are never unique, so they cannot be used
to distinguish MAC addresses).
o If the first bit of the "Node-Number" is "1", then the Node-Number
is 17 bit long and the V field is 16 bit long. Otherwise the
Node-Number is 33 bit long and the V field is 8 bit long. "0" bit
Node-Numbers are intended to be used for "general purpose" ACP
nodes that would potentially have a limited number (< 256) of
clients (ASA/Autonomic Functions or legacy services) nof the ACP
that require separate V(irtual) addresses. "1" bit Node-Numbers
are intended for ACP nodes that are ACP edge nodes (see
Behringer, et al. Expires April 15, 2018 [Page 39]
Internet-Draft An Autonomic Control Plane (ACP) October 2017
Section 8.1.1) or that have a large number of clients requiring
separate V(irtual) addresses. For example large SDN controllers
with container modular software architecture (see Section 8.1.2).
In the Vlong addressing sub-scheme, the ACP address in the
certificate has all V field bits as zero. The ACP address set for
the node includes any V value.
6.10.6. Other ACP Addressing Sub-Schemes
Before further addressing sub-schemes are defined, experience with
the schemes defined here should be collected. The schemes defined in
this document have been devised to allow hopefully sufficiently
flexible setup of ACPs for a variety of situation. These reasons
also lead to the fairly liberal use of address space: The Zone
addressing sub-schemes is intended to enable optimized routing in
large networks by reserving bits for zones. The Vlong addressing
sub-scheme enables the allocation of 8/16 bit of addresses inside
individual ACP nodes. Both address spaces allow distributed,
uncoordinated allocation of node addresses by reserving bits for the
Registrar-ID field in the address.
IANA is asked need to assign a new "type" for each new addressing
sub-scheme. With the current allocations, only 2 more schemes are
possible, so the last addressing scheme should consider to be
extensible in itself (e.g.: by reserving bits from it for further
extensions.
6.11. Routing in the ACP
Once ULA address are set up all autonomic entities should run a
routing protocol within the autonomic control plane context. This
routing protocol distributes the ULA created in the previous section
for reachability. The use of the autonomic control plane specific
context eliminates the probable clash with the global routing table
and also secures the ACP from interference from the configuration
mismatch or incorrect routing updates.
The establishment of the routing plane and its parameters are
automatic and strictly within the confines of the autonomic control
plane. Therefore, no manual configuration is required.
All routing updates are automatically secured in transit as the
channels of the autonomic control plane are by default secured, and
this routing runs only inside the ACP.
The routing protocol inside the ACP is RPL ([RFC6550]). See
Section 10.5 for more details on the choice of RPL.
Behringer, et al. Expires April 15, 2018 [Page 40]
Internet-Draft An Autonomic Control Plane (ACP) October 2017
RPL adjacencies are set up across all ACP channels in the same domain
including all its routing subdomains. See Section 10.7 for more
details.
6.11.1. RPL Profile
The following is a description of the RPL profile that ACP nodes need
to support by default. The format of this section is derived from
draft-ietf-roll-applicability-template.
6.11.1.1. Summary
In summary, the profile chosen for RPL is one that expects a fairly
reliable network reasonable fast links so that RPL convergence will
be triggered immediately upon recognition of link failure/recovery.
The key limitation of the chosen profile is that it is designed to
not require any data-plane artifacts (such as [RFC6553]). While the
senders/receivers of ACP packets can be legacy NOC devices connected
via "ACP connect" (see Section 8.1.1 to the ACP, their connectivity
can be handled as non-RPL-aware leafs (or "Internet") according to
the data-plane architecture explained in
[I-D.ietf-roll-useofrplinfo]. This non-artifact profile is largely
driven by the desire to avoid introducing the required Hop-by-Hop
headers into the ACP VRF control plane. Many devices will have their
VRF forwarding code designed into silicon.
In this profile choice, RPL has no data-plane artifacts. A simple
destination prefix based upon the routing table is used. A
consequence of supporting only a single instanceID (containing one
DODAG), the ACP will only accommodate only a single class of routing
table and cannot create optimized routing paths to accomplish latency
or energy goals.
Consider a network that has multiple NOCs in different locations.
Only one NOC will become the DODAG root. Other NOCs will have to
send traffic through the DODAG (tree) rooted in the primary NOC.
Depending on topology, this can be an annoyance from a latency point
of view, but it does not represent a single point of failure, as the
DODAG can reconfigure itself when it detects data plane forwarding
failures.
The lack of a RPI (the header defined by [RFC6553]), means that the
data-plane will have no rank value that can be used to detect loops.
As a result, traffic may loop until the TTL of the packet reaches
zero. This the same behavior as that of other IGPs that do not have
the data-plane options as RPPL. There are a variety of heuristics
Behringer, et al. Expires April 15, 2018 [Page 41]
Internet-Draft An Autonomic Control Plane (ACP) October 2017
that can be used to signal from the data-plane to the RPL control
plane that a new route is needed.
Additionally, failed ACP tunnels will be detected by IKEv2 Dead Peer
Detection (which can function as a replacement for an LLN's ETX). A
failure of an ACP tunnel should signal the RPL control plane to pick
a different parent.
Future Extensions to this RPL profile can provide optimality for
multiple NOCs. This requires utilizing data-plane artifact including
IPinIP encap/decap on ACP routers and processing of IPv6 RPI headers.
Alternatively, (Src,Dst) routing table entries could be used. A
decision for the preferred technology would have to be done when such
extension is defined.
6.11.1.2. RPL Instances
Single RPL instance. Default RPLInstanceID = 0.
6.11.1.3. Storing vs. Non-Storing Mode
RPL Mode of Operations (MOP): mode 3 "Storing Mode of Operations with
multicast support". Implementations should support also other modes.
Note: Root indicates mode in DIO flow.
6.11.1.4. DAO Policy
Proactive, aggressive DAO state maintenance:
o Use K-flag in unsolicited DAO indicating change from previous
information (to require DAO-ACK).
o Retry such DAO DAO-RETRIES(3) times with DAO- ACK_TIME_OUT(256ms)
in between.
6.11.1.5. Path Metric
Hopcount.
6.11.1.6. Objective Function
Objective Function (OF): Use OF0 [RFC6552]. No use of metric
containers.
rank_factor: Derived from link speed: <= 100Mbps:
LOW_SPEED_FACTOR(5), else HIGH_SPEED_FACTOR(1)
Behringer, et al. Expires April 15, 2018 [Page 42]
Internet-Draft An Autonomic Control Plane (ACP) October 2017
6.11.1.7. DODAG Repair
Global Repair: we assume stable links and ranks (metrics), so no need
to periodically rebuild DODAG. DODAG version only incremented under
catastrophic events (e.g.: administrative action).
Local Repair: As soon as link breakage is detected, send No-Path DAO
for all the targets that where reachable only via this link. As soon
as link repair is detected, validate if this link provides you a
better parent. If so, compute your new rank, and send new DIO that
advertises your new rank. Then send a DAO with a new path sequence
about yourself.
stretch_rank: none provided ("not stretched").
Data Path Validation: Not used.
Trickle: Not used.
6.11.1.8. Multicast
Not used yet but possible because of the selected mode of operations.
6.11.1.9. Security
[RFC6550] security not used, substituted by ACP security.
6.11.1.10. P2P communications
Not used.
6.11.1.11. IPv6 address configuration
Every ACP node (RPL node) announces an IPv6 prefix covering the
address(es) used in the ACP node. The prefix length depends on the
chosen addressing sub-scheme of the ACP address provisioned into the
certificate of the ACP node, e.g.: /127 for Zone addressing sub-
scheme or /112 or /120 for Vlong addressing sub-scheme. See
Section 6.10 for more details.
Every ACP node MUST install a black hole (aka null) route for
whatever ACP address space that it advertises (i.e.: the /96 or
/127). This is avoid routing loops for addresses that an ACP node
has not (yet) used.
Behringer, et al. Expires April 15, 2018 [Page 43]
Internet-Draft An Autonomic Control Plane (ACP) October 2017
6.11.1.12. Administrative parameters
Administrative Preference ([RFC6552], 3.2.6 - to become root):
Indicated in DODAGPreference field of DIO message.
o Explicit configured "root": 0b100
o Registrar (Default): 0b011
o AN-connect (non-registrar): 0b010
o Default: 0b001.
6.11.1.13. RPL Data-Plane artifacts
RPI (RPL Packet Information [RFC6553]): Not used as there is only a
single instance, and data path validation is not being used.
SRH (RPL Source Routing - RFC6552): Not used. Storing mode is being
used.
6.11.1.14. Unknown Destinations
Because RPL minimizes the size of the routing and forwarding table,
prefixes reachable through the same interface as the RPL root are not
known on every ACP node. Therefore traffic to unknown destination
addresses can only be discovered at the RPL root. The RPL root
SHOULD have attach safe mechanisms to operationally discover and log
such packets.
6.12. General ACP Considerations
Since channels are by default established between adjacent neighbors,
the resulting overlay network does hop by hop encryption. Each node
decrypts incoming traffic from the ACP, and encrypts outgoing traffic
to its neighbors in the ACP. Routing is discussed in Section 6.11.
6.12.1. Performance
There are no performance requirements against ACP implementations
defined in this document because the performance requirements depend
on the intended use case. It is expected that full autonomic node
with a wide range of ASA can require high forwarding plane
performance in the ACP, for example for telemetry, but that
determination is for future work. Implementations of ACP to solely
support traditional/SDN style use cases can benefit from ACP at lower
performance, especially if the ACP is used only for critical
Behringer, et al. Expires April 15, 2018 [Page 44]
Internet-Draft An Autonomic Control Plane (ACP) October 2017
operations, e.g.: when the data-plane is not available. See
[I-D.ietf-anima-stable-connectivity] for more details.
6.12.2. Addressing of Secure Channels in the data-plane
In order to be independent of the data-plane configuration of global
IPv6 subnet addresses (that may not exist when the ACP is brought
up), Link-local secure channels MUST use IPv6 link local addresses
between adjacent neighbors. The fully autonomic mechanisms in this
document only specify these link-local secure channels. Section 8.2
specifies extensions in which secure channels are tunnels. For
those, this requirement does not apply.
The Link-local secure channels specified in this document therefore
depend on basic IPv6 link-local functionality to be auto-enabled by
the ACP and prohibiting the data-plane from disabling it. The ACP
also depends on being able to operate the secure channel protocol
(e.g.: IPsec / dTLS) across IPv6 link-local addresses, something that
may be an uncommon profile. Functionally, these are the only
interactions with the data-plane that the ACP needs to have.
To mitigate these interactions with the data-plane, extensions to
this document may specify additional layer 2 or layer encapsulations
for ACP secure channels as well as other protocols to auto-discover
peer endpoints for such encapsulations (e.g.: tunneling across L3 or
use of L2 only encapsulations).
6.12.3. MTU
The MTU for ACP secure channels must be derived locally from the
underlying link MTU minus the secure channel encapsulation overhead.
ACP secure Channel protocols do not need to perform MTU discovery
because they are built across L2 adjacencies - the MTU on both sides
connecting to the L2 connection are assumed to be consistent.
Extensions to ACP where the ACP is for example tunneled need to
consider how to guarantee MTU consistency. This is a standard issue
with tunneling, not specific to running the ACP across it. Transport
stacks running across ACP can perform normal PMTUD (Path MTU
Discovery). Because the ACP is meant to be prioritize reliability
over performance, they MAY opt to only expect IPv6 minimum MTU (1280)
to avoid running into PMTUD implementation bugs or underlying link
MTU mismatch problems.
Behringer, et al. Expires April 15, 2018 [Page 45]
Internet-Draft An Autonomic Control Plane (ACP) October 2017
6.12.4. Multiple links between nodes
If two nodes are connected via several links, the ACP SHOULD be
established across every link, but it is possible to establish the
ACP only on a sub-set of links. Having an ACP channel on every link
has a number of advantages, for example it allows for a faster
failover in case of link failure, and it reflects the physical
topology more closely. Using a subset of links (for example, a
single link), reduces resource consumption on the node, because state
needs to be kept per ACP channel. The negotiation scheme explained
in Section 6.5 allows Alice (the node with the higher ACP address) to
drop all but the desired ACP channels to Bob - and Bob will not re-
try to build these secure channels from his side unless Alice shows
up with a previously unknown GRASP announcement (e.g.: on a different
link or with a different address announced in GRASP).
6.12.5. ACP interfaces
The ACP VRF has conceptually two type of interfaces: The "ACP
loopback interface(s)" to which the ACP ULA address(es) are assigned
and the "ACP virtual interfaces" that are mapped to the ACP secure
channels.
The term "loopback interface" was introduced initially to refer to an
internal interface on a node that would allow IP traffic between
transport endpoints on the node in the absence or failure of any or
all external interfaces, see [RFC4291] section 2.5.3.
Even though loopback interfaces where originally designed to hold
only loopback addresses not reachable from outside the node, these
interfaces are also commonly used today to hold addresses reachable
from the outside. They are meant to be reachable independent of any
external interface being operational, and therefore to be more
resilient. These addresses on loopback interfaces can be thought of
as "node addresses" instead of "interface addresses", and that is
what ACP address(es) are. This construct makes it therefore possible
to address ACP nodes with a well-defined set of addresses independent
of the number of external interfaces.
For these reason, the ACP (ULA) address(es) are assigned to loopback
interface(s).
ACP secure channels, e.g.: IPsec, dTLS or other future security
associations with neighboring ACP nodes can be mapped to ACP virtual
interfaces in different ways:
ACP point-to-point virtual interface:
Behringer, et al. Expires April 15, 2018 [Page 46]
Internet-Draft An Autonomic Control Plane (ACP) October 2017
Each ACP secure channel is mapped into a separate point-to-point ACP
virtual interface. If a physical subnet has more than two ACP
capable nodes (in the same domain), this implementation approach will
lead to a full mesh of ACP virtual interfaces between them.
ACP multi-access virtual interface:
In a more advanced implementation approach, the ACP will construct a
single multi-access ACP virtual interface for all ACP secure channels
to ACP capable nodes reachable across the same underlying (physical)
subnet. IPv6 link-local multicast packets sent into an ACP multi-
access virtual interface are replicated to every ACP secure channel
mapped into the ACP multicast-access virtual interface. IPv6 unicast
packets sent into an ACP multi-access virtual interface are sent to
the ACP secure channel that belongs to the ACP neighbor that is the
next-hop in the ACP forwarding table entry used to reach the packets
destination address.
There is no requirement for all ACP nodes on the same multi-access
subnet to use the same type of ACP virtual interface. This is purely
a node local decision.
ACP nodes MUST perform standard IPv6 operations across ACP virtual
interfaces including SLAAC (Stateless Address Auto-Configuration -
[RFC4862]) to assign their IPv6 link local address on the ACP virtual
interface and ND (Neighbor Discovery - [RFC4861]) to discover which
IPv6 link-local neighbor address belongs to which ACP secure channel
mapped to the ACP virtual interface. This is independent of whether
the ACP virtual interface is point-to-point or multi-access.
ACP nodes MAY reduce the amount of link-local IPv6 multicast packets
from ND by learning the IPv6 link-local neighbor address to ACP
secure channel mapping from other messages such as the source address
of IPv6 link-local multicast RPL messages - and therefore forego the
need to send Neighbor Solicitation messages.
ACP nodes MUST NOT derive their ACP virtual interface IPv6 link local
address from their IPv6 link-local address used on the underlying
interface (e.g.: the address that is used as the encapsulation
address in the ACP secure channel protocols defined in this
document). This ensures that the ACP virtual interface operations
will not depend on the specifics of the encapsulation used by the ACP
secure channel and that attacks against SLAAC on the physical
interface will not introduce new attack vectors against the
operations of the ACP virtual interface.
The link-layer address of an ACP virtual interface is the address
used for the underlying interface across which the secure tunnels are
Behringer, et al. Expires April 15, 2018 [Page 47]
Internet-Draft An Autonomic Control Plane (ACP) October 2017
built, typically Ethernet addresses. Because unicast IPv6 packets
sent to an ACP virtual interface are not sent to a link-layer
destination address but rather an ACP secure channel, the link-layer
address fields SHOULD be ignored on reception and instead the ACP
secure channel from which the message was received should be
remembered.
Multi-access ACP virtual interfaces are preferable implementations
when the underlying interface is a (broadcast) multi-access subnet
because they do reflect the presence of the underlying multi-access
subnet into the virtual interfaces of the ACP. This makes it for
example simpler to build services with topology awareness inside the
ACP VRF in the same way as they could have been built running
natively on the multi-access interfaces.
Consider also the impact of point-to-point vs. multi-access virtual
interface on the efficiency of flooding via link local multicasted
messages:
Assume a LAN with three ACP neighbors, Alice, Bob and Carol. Alice's
ACP GRASP wants to send a link-local GRASP multicast message to Bob
and Carol. If Alice's ACP emulates the LAN as one point-to-point
virtual interface to Bob and one to Carol, The sending applications
itself will send two copies, if Alice's ACP emulates a LAN, GRASP
will send one packet and the ACP will replicate it. The result is
the same. The difference happens when Bob and Carol receive their
packet. If they use ACP point-to-point virtual interfaces, their
GRASP instance would forward the packet from Alice to each other as
part of the GRASP flooding procedure. These packets are unnecessary
and would be discarded by GRASP on receipt as duplicates (by use of
the GRASP Session ID). If Bob and Charlies ACP would emulate a
multi-access virtual interface, then this would not happen, because
GRASPs flooding procedure does not replicate back packets to the
interface that they were received from.
Note that link-local GRASP multicast messages are not sent directly
as IPv6 link-local multicast UDP messages into ACP virtual
interfaces, but instead into ACP GRASP virtual interfaces, that are
layered on top of ACP virtual interfaces to add TCP reliability to
link-local multicast GRASP messages. Nevertheless, these ACP GRASP
virtual interfaces perform the same replication of message and,
therefore, result in the same impact on flooding. See Section 6.8.2
for more details.
RPL does support operations and correct routing table construction
across non-broadcast multi-access (NBMA) subnets. This is common
when using many radio technologies. When such NBMA subnets are used,
they MUST NOT be represented as ACP multi-access virtual interfaces
Behringer, et al. Expires April 15, 2018 [Page 48]
Internet-Draft An Autonomic Control Plane (ACP) October 2017
because the replication of IPv6 link-local multicast messages will
not reach all NBMA subnet neighbors. In result, GRASP message
flooding would fail. Instead, each ACP secure channel across such an
interface MUST be represented as a ACP point-to-point virtual
interface. These requirements can be avoided by coupling the ACP
flooding mechanism for GRASP messages directly to RPL (flood GRASP
across DODAG), but such an enhancement is subject for future work.
Care must also be taken when creating multi-access ACP virtual
interfaces across ACP secure channels between ACP nodes in different
domains or routing subdomains. The policies to be negotiated may be
described as peer-to-peer policies in which case it is easier to
create ACP point-to-point virtual interfaces for these secure
channels.
7. ACP support on L2 switches/ports (Normative)
7.1. Why
ANrtr1 ------ ANswitch1 --- ANswitch2 ------- ANrtr2
.../ \ \ ...
ANrtrM ------ \ ------- ANrtrN
ANswitchM ...
Figure 7
Consider a large L2 LAN with ANrtr1...ANrtrN connected via some
topology of L2 switches. Examples include large enterprise campus
networks with an L2 core, IoT networks or broadband aggregation
networks which often have even a multi-level L2 switched topology.
If the discovery protocol used for the ACP is operating at the subnet
level, every ACP router will see all other ACP routers on the LAN as
neighbors and a full mesh of ACP channels will be built. If some or
all of the AN switches are autonomic with the same discovery
protocol, then the full mesh would include those switches as well.
A full mesh of ACP connections like this can creates fundamental
scale challenges. The number of security associations of the secure
channel protocols will likely not scale arbitrarily, especially when
they leverage platform accelerated encryption/decryption. Likewise,
any other ACP operations (such as routing) needs to scale to the
number of direct ACP neighbors. An ACP router with just 4 physical
interfaces might be deployed into a LAN with hundreds of neighbors
connected via switches. Introducing such a new unpredictable scaling
factor requirement makes it harder to support the ACP on arbitrary
platforms and in arbitrary deployments.
Behringer, et al. Expires April 15, 2018 [Page 49]
Internet-Draft An Autonomic Control Plane (ACP) October 2017
Predictable scaling requirements for ACP neighbors can most easily be
achieved if in topologies like these, ACP capable L2 switches can
ensure that discovery messages terminate on them so that neighboring
ACP routers and switches will only find the physically connected ACP
L2 switches as their candidate ACP neighbors. With such a discovery
mechanism in place, the ACP and its security associations will only
need to scale to the number of physical interfaces instead of a
potentially much larger number of "LAN-connected" neighbors. And the
ACP topology will follow directly the physical topology, something
which can then also be leveraged in management operations or by ASAs.
In the example above, consider ANswitch1 and ANswitchM are ACP
capable, and ANswitch2 is not ACP capable. The desired ACP topology
is that ANrtr1 and ANrtrM only have an ACP connection to ANswitch1,
and that ANswitch1, ANrtr2, ANrtrN have a full mesh of ACP connection
amongst each other. ANswitch1 also has an ACP connection with
ANswitchM and ANswitchM has ACP connections to anything else behind
it.
7.2. How (per L2 port DULL GRASP)
To support ACP on L2 switches or L2 switched ports of an L3 device,
it is necessary to make those L2 ports look like L3 interfaces for
the ACP implementation. This primarily involves the creation of a
separate DULL GRASP instance/domain on every such L2 port. Because
GRASP has a dedicated link-local IPv6 multicast address
(ALL_GRASP_NEIGHBORS), it is sufficient that all packets for this
address are being extracted at the port level and passed to that DULL
GRASP instance. Likewise the IPv6 link-local multicast packets sent
by that DULL GRASP instance need to be sent only towards the L2 port
for this DULL GRASP instance.
If the device with L2 ports is supporting per L2 port ACP DULL GRASP
as well as MLD snooping ([RFC4541]), then MLD snooping must be
changed to never forward packets for ALL_GRASP_NEIGHBORS because that
would cause the problem that per L2 port ACP DULL GRASP is meant to
overcome (forwarding DULL GRASP packets across L2 ports).
The rest of ACP operations can operate in the same way as in L3
devices: Assume for example that the device is an L3/L2 hybrid device
where L3 interfaces are assigned to VLANs and each VLAN has
potentially multiple ports. DULL GRASP is run as described
individually on each L2 port. When it discovers a candidate ACP
neighbor, it passes its IPv6 link-local address and supported secure
channel protocols to the ACP secure channel negotiation that can be
bound to the L3 (VLAN) interface. It will simply use link-local IPv6
multicast packets to the candidate ACP neighbor. Once a secure
channel is established to such a neighbor, the virtual interface to
Behringer, et al. Expires April 15, 2018 [Page 50]
Internet-Draft An Autonomic Control Plane (ACP) October 2017
which this secure channel is mapped should then actually be the L2
port and not the L3 interface to best map the actual physical
topology into the ACP virtual interfaces. See Section 6.12.5 for
more details about how to map secure channels into ACP virtual
interfaces. Note that a single L2 port can still have multiple ACP
neighbors if it connect for example to multiple ACP neighbors via a
non-ACP enabled switch. The per L2 port ACP virtual interface can
therefore still be a multi-access virtual LAN.
For example, in the above picture, ANswitch1 would run separate DULL
GRASP instances on its ports to ANrtr1, ANswitch2 and ANswitchI, even
though all those three ports may be in the data plane in the same
(V)LAN and perform L2 switching between these ports, ANswitch1 would
perform ACP L3 routing between them.
The description in the previous paragraph was specifically meant to
illustrate that on hybrid L3/L2 devices that are common in
enterprise, IoT and broadband aggregation, there is only the GRASP
packet extraction (by Ethernet address) and GRASP link-local
multicast per L2-port packet injection that has to consider L2 ports
at the hardware forwarding level. The remaining operations are
purely ACP control plane and setup of secure channels across the L3
interface. This hopefully makes support for per-L2 port ACP on those
hybrid devices easy.
This L2/L3 optimized approach is subject to "address stealing", e.g.:
where a device on one port uses addresses of a device on another
port. This is a generic issue in L2 LANs and switches often already
have some form of "port security" to prohibit this. They rely on NDP
or DHCP learning of which port/MAC-address and IPv6 address belong
together and block duplicates. This type of function needs to be
enabled to prohibit DoS attacks. Likewise the GRASP DULL instance
needs to ensure that the IPv6 address in the locator-option matches
the source IPv6 address of the DULL GRASP packet.
In devices without such a mix of L2 port/interfaces and L3 interfaces
(to terminate any transport layer connections), implementation
details will differ. Logically most simply every L2 port is
considered and used as a separate L3 subnet for all ACP operations.
The fact that the ACP only requires IPv6 link-local unicast and
multicast should make support for it on any type of L2 devices as
simple as possible, but the need to support secure channel protocols
may be a limiting factor to supporting ACP on such devices. Future
options such as 802.1ae could improve that situation.
A generic issue with ACP in L2 switched networks is the interaction
with the Spanning Tree Protocol. Ideally, the ACP should be built
also across ports that are blocked in STP so that the ACP does not
Behringer, et al. Expires April 15, 2018 [Page 51]
Internet-Draft An Autonomic Control Plane (ACP) October 2017
depend on STP and can continue to run unaffected across STP topology
changes (where re-convergence can be quite slow). The above
described simple implementation options are not sufficient for this.
Instead they would simply have the ACP run across the active STP
topology and the ACP would equally be interrupted and re-converge
with STP changes.
8. Support for Non-ACP Components (Normative)
8.1. ACP Connect
8.1.1. Non-ACP Controller / NMS system
The Autonomic Control Plane can be used by management systems, such
as controllers or network management system (NMS) hosts (henceforth
called simply "NMS hosts"), to connect to devices (or other type of
nodes) through it. For this, an NMS host must have access to the
ACP. The ACP is a self-protecting overlay network, which allows by
default access only to trusted, autonomic systems. Therefore, a
traditional, non-ACP NMS system does not have access to the ACP by
default, just like any other external node.
If the NMS host is not autonomic, i.e., it does not support autonomic
negotiation of the ACP, then it can be brought into the ACP by
explicit configuration. To support connections to adjacent non-ACP
nodes, an ACP node must support "ACP connect" (sometimes also connect
"autonomic connect"):
"ACP connect" is a function on an autonomic node that is called an
"ACP edge node". With "ACP connect", interfaces on the node can be
configured to be put into the ACP VRF. The ACP is then accessible to
other (NOC) systems on such an interface without those systems having
to support any ACP discovery or ACP channel setup. This is also
called "native" access to the ACP because to those (NOC) systems the
interface looks like a normal network interface (without any
encryption/novel-signaling).
Behringer, et al. Expires April 15, 2018 [Page 52]
Internet-Draft An Autonomic Control Plane (ACP) October 2017
data-plane "native" (no ACP)
.
+--------+ +----------------+ . +-------------+
| ACP | |ACP Edge Node | . | |
| Node | | | v | |
| |-------|...[ACP VRF]....+-----------------| |+
| | ^ |. | | NOC Device ||
| | . | .[data-plane]..+-----------------| "NMS hosts" ||
| | . | [ VRF ] | . ^ | ||
+--------+ . +----------------+ . . +-------------+|
. . . +-------------+
. . .
data-plane "native" . ACP "native" (unencrypted)
+ ACP auto-negotiated . "ACP connect subnet"
and encrypted .
ACP connect interface
e.g.: "vrf ACP native" (config)
Figure 8: ACP connect
ACP connect has security consequences: All systems and processes
connected via ACP connect have access to all ACP nodes on the entire
ACP, without further authentication. Thus, the ACP connect interface
and (NOC) systems connected to it must be physically controlled/
secured. For this reason the mechanisms described here do explicitly
not include options to allow for a non-ACP router to be connected
across an ACP connect interface and addresses behind such a router
routed inside the ACP.
An ACP connect interface provides exclusively access to only the ACP.
This is likely insufficient for many NMS hosts. Instead, they would
require a second "data-plane" interface outside the ACP for
connections between the NMS host and administrators, or Internet
based services, or for direct access to the data-plane. The document
"Autonomic Network Stable Connectivity"
[I-D.ietf-anima-stable-connectivity] explains in more detail how the
ACP can be integrated in a mixed NOC environment.
The ACP connect interface must be (auto-)configured with an IPv6
address prefix. Is prefix SHOULD be covered by one of the (ULA)
prefix(es) used in the ACP. If using non-autonomic configuration, it
SHOULD use the ACP Manual Addressing Sub-Scheme (Section 6.10.4). It
SHOULD NOT use a prefix that is also routed outside the ACP so that
the addresses clearly indicate whether it is used inside the ACP or
not.
Behringer, et al. Expires April 15, 2018 [Page 53]
Internet-Draft An Autonomic Control Plane (ACP) October 2017
The prefix of ACP connect subnets MUST be distributed by the ACP edge
node into the ACP routing protocol (RPL). The NMS hosts MUST connect
to prefixes in the ACP routing table via its ACP connect interface.
In the simple case where the ACP uses only one ULA prefix and all ACP
connect subnets have prefixes covered by that ULA prefix, NMS hosts
can rely on [RFC6724] - The NMS host will select the ACP connect
interface because any ACP destination address is best matched by the
address on the ACP connect interface. If the NMS hosts ACP connect
interface uses another prefix or if the ACP uses multiple ULA
prefixes, then the NMS hosts require (static) routes towards the ACP
interface.
ACP Edge Nodes MUST only forward IPv6 packets received from an ACP
connect interface into the ACP that has an IPv6 address from the ACP
prefix assigned to this interface (sometimes called "RPF filtering").
This MAY be changed through administrative measures.
To limit the security impact of ACP connect, nodes supporting it
SHOULD implement a security mechanism to allow configuration/use of
ACP connect interfaces only on nodes explicitly targeted to be
deployed with it (such as those physically secure locations like a
NOC). For example, the certificate of such node could include an
extension required to permit configuration of ACP connect interfaces.
This prohibits that a random ACP node with easy physical access that
is not meant to run ACP connect could start leaking the ACP when it
becomes compromised and the intruder configures ACP connect on it.
The full workflow including the mechanism by which a registrar would
select which node to give such a certificate to is subject to future
work.
8.1.2. Software Components
The ACP connect mechanism be only be used to connect physically
external systems (NMS hosts) to the ACP but also other applications,
containers or virtual machines. In fact, one possible way to
eliminate the security issue of the external ACP connect interface is
to collocate an ACP edge node and an NMS host by making one a virtual
machine or container inside the other; and therefore converting the
unprotected external ACP subnet into an internal virtual subnet in a
single device. This would ultimately result in a fully ACP enabled
NMS host with minimum impact to the NMS hosts software architecture.
This approach is not limited to NMS hosts but could equally be
applied to devices consisting of one or more VNF (virtual network
functions): An internal virtual subnet connecting out-of-band-
management interfaces of the VNFs to an ACP edge router VNF.
The core requirement is that the software components need to have a
network stack that permits access to the ACP and optionally also the
Behringer, et al. Expires April 15, 2018 [Page 54]
Internet-Draft An Autonomic Control Plane (ACP) October 2017
data-plane. Like in the physical setup for NMS hosts this can be
realized via two internal virtual subnets. One that is connecting to
the ACP (which could be a container or virtual machine by itself),
and one (or more) connecting into the data-plane.
This "internal" use of ACP connect approach should not considered to
be a "workaround" because in this case it is possible to build a
correct security model: It is not necessary to rely on unprovable
external physical security mechanisms as in the case of external NMS
hosts. Instead, the orchestration of the ACP, the virtual subnets
and the software components can be done by trusted software that
could be considered to be part of the ANI (or even an extended ACP).
This software component is responsible to ensure that only trusted
software components will get access to that virtual subnet and that
only even more trusted software components will get access to both
the ACP virtual subnet and the data-plane (because those ACP users
could leak traffic between ACP and data-plane). This trust could be
established for example through cryptographic means such signed
software packages. The specification of these mechanisms is subject
to future work.
Note that ASA (Autonomic Software Agents) could also be software
components as described in this section, but further details of ASAs
are subject to future work.
8.1.3. Auto Configuration
ACP edge nodes, NMS hosts and software components that as described
in the previous section are meant to be composed via virtual
interfaces SHOULD support on the ACP connect subnet Stateless Address
Autoconfiguration (SLAAC - [RFC4862]) and route autoconfiguration
according to [RFC4191].
The ACP edge node acts as the router on the ACP connect subnet,
providing the (auto-)configured prefix for the ACP connect subnet to
NMS hosts and/or software components. The ACP edge node uses route
prefix option of RFC4191 to announce the default route (::/) with a
lifetime of 0 and aggregated prefixes for routes in the ACP routing
table with normal lifetimes. This will ensure that the ACP edge node
does not become a default router, but that the NMS hosts and software
components will route the prefixes used in the ACP to the ACP edge
node.
Aggregated prefix means that the ACP edge node needs to only announce
the /48 ULA prefixes used in the ACP but none of the actual /64
(Manual Addressing Sub-Scheme), /127 (Zone Addressing Sub-Scheme),
/112 or /120 (Vlong Addressing Sub-Scheme) routes of actual ACP
nodes. If ACP interfaces are configured with non ULA prefixes, then
Behringer, et al. Expires April 15, 2018 [Page 55]
Internet-Draft An Autonomic Control Plane (ACP) October 2017
those prefixes cannot be aggregated without further configured policy
on the ACP edge node. This explains the above recommendation to use
ACP ULA prefix covered prefixes for ACP connect interfaces: They
allow for a shorter list of prefixes to be signaled via RFC4191 to
NMS hosts and software components.
The ACP edge nodes that have a Vlong ACP address MAY allocate a
subset of their /112 or /120 address prefix to ACP connect
interface(s) to eliminate the need to non-autonomically configure/
provision the address prefixes for such ACP connect interfaces.
8.1.4. Combined ACP/Data-Plane Interface (VRF Select)
Combined ACP and Data-Plane interface
.
+--------+ +--------------------+ . +--------------+
| ACP | |ACP Edge No | . | NMS Host(s) |
| Node | | | . | / Software |
| | | [ACP ]. | . | |+
| | | .[VRF ] .[VRF ] | v | "ACP address"||
| +-------+. .[Select].+--------+ "Date Plane ||
| | ^ | .[Data ]. | | Address(es)"||
| | . | [Plane] | | ||
| | . | [VRF ] | +--------------+|
+--------+ . +--------------------+ +--------------+
.
data-plane "native" and + ACP auto-negotiated/encrypted
Figure 9: VRF select
Using two physical and/or virtual subnets (and therefore interfaces)
into NMS Hosts (as per Section 8.1.1) or Software (as per
Section 8.1.2) may be seen as additional complexity, for example with
legacy NMS Hosts that support only one IP interface.
To provide a single subnet into both ACP and data-plane, the ACP Edge
node needs to de-multiplex packets from NMS hosts into ACP VRF and
data-plane VRF. This is sometimes called "VRF select". If the ACP
VRF has no overlapping IPv6 addresses with the data-plane (as it
should), then this function can use the IPv6 Destination address.
The problem is Source Address Selection on the NMS Host(s) according
to RFC6724.
Consider the simple case: The ACP uses only one ULA prefix, the ACP
IPv6 prefix for the Combined ACP and data-plane interface is covered
by that ULA prefix. The ACP edge node announces both the ACP IPv6
Behringer, et al. Expires April 15, 2018 [Page 56]
Internet-Draft An Autonomic Control Plane (ACP) October 2017
prefix and one (or more) prefixes for the data-plane. Without
further policy configurations on the NMS Host(s), it may select its
ACP address as a source address for data-plane ULA destinations
because of Rule 8 of RFC6724. The ACP edge node can pass on the
packet to the data-plane, but the ACP source address should not be
used for data-plane traffic, and return traffic may fail.
If the ACP carries multiple ULA prefixes or non-ULA ACP connect
prefixes, then the correct source address selection becomes even more
problematic.
With separate ACP connect and data-plane subnets and RFC4191 prefix
announcements that are to be routed across the ACP connect interface,
RFC6724 source address selection Rule 5 (use address of outgoing
interface) will be used, so that above problems do not occur, even in
more complex cases of multiple ULA and non-ULA prefixes in the ACP
routing table.
To achieve the same behavior with a Combined ACP and data-plane
interface, the ACP Edge Node needs to behave as two separate routers
on the interface: One link-local IPv6 address/router for its ACP
reachability, and one link-local IPv6 address/router for its data-
plane reachability. The Router Advertisements for both are as
described above (Section 8.1.3): For the ACP, the ACP prefix is
announced together with RFC4191 option for the prefixes routed across
the ACP and lifetime=0 to disqualify this next-hop as a default
router. For the data-plane, the data-plane prefix(es) are announced
together with whatever dafault router parameters are used for the
data-plane.
In result, RFC6724 source address selection Rule 5.5 may result in
the same correct source address selection behavior of NMS hosts
without further configuration on it as the separate ACP connect and
data-plane interfaces. As described in the text for Rule 5.5, this
is only a may, because IPv6 hosts are not required to track next-hop
information. If an NMS Host does not do this, then separate ACP
connect and data-plane interfaces are the preferable method of
attachment.
ACP edge nodes MAY support the Combined ACP and Data-Plane interface.
8.1.5. Use of GRASP
GRASP can and should be possible to use across ACP connect
interfaces, especially in the architectural correct solution when it
is used as a mechanism to connect Software (e.g.: ASA or legacy NMS
applications) to the ACP. Given how the ACP is the security and
transport substrate for GRASP, the trustworthiness of nodes/software
Behringer, et al. Expires April 15, 2018 [Page 57]
Internet-Draft An Autonomic Control Plane (ACP) October 2017
allowed to participate in the ACP GRASP domain is one of the main
reasons why the ACP section describes no solution with non-ACP
routers participating in the ACP routing table.
ACP connect interfaces can be dealt with in the GRASP ACP domain like
any other ACP interface assuming that any physical ACP connect
interface is physically protected from attacks and that the connected
Software or NMS Hosts are equally trusted as that on other ACP nodes.
ACP edge nodes SHOULD have options to filter GRASP messages in and
out of ACP connect interfaces (permit/deny) and MAY have more fine-
grained filtering (e.g.: based on IPv6 address of originator or
objective).
When using "Combined ACP and Data-Plane Interfaces", care must be
taken that only GRASP messages intended for the ACP GRASP domain
received from Software or NMS Hosts are forwarded by ACP edge nodes.
Currently there is no definition for a GRASP security and transport
substrate beside the ACP, so there is no definition how such
Software/NMS Host could participate in two separate GRASP Domains
across the same subnet (ACP and data-plane domains). At current it
is assumed that all GRASP packets on a Combined ACP and data-plane
interface belong to the GRASP ACP Domain. They must all use the ACP
IPv6 addresses of the Software/NMS Hosts. The link-local IPv6
addresses of Software/NMS Hosts (used for GRASP M_DISCOVERY and
M_FLOOD messages) are also assumed to belong to the ACP address
space.
8.2. ACP through Non-ACP L3 Clouds (Remote ACP neighbors)
Not all nodes in a network may support the ACP. If non-ACP Layer-2
devices are between ACP nodes, the ACP will work across it since it
is IP based. However, the autonomic discovery of ACP neighbors via
DULL GRASP is only intended to work across L2 connections, so it is
not sufficient to autonomically create ACP connections across non-ACP
Layer-3 devices.
8.2.1. Configured Remote ACP neighbor
On the ACP node, remote ACP neighbors are configured as follows:
remote-peer = [ local-address, method, remote-address ]
local-address = ip-address
remote-address = transport-address
transport-address =
[ (ip-address | pattern) ?( , protocol ?(, port)) (, pmtu) ]
ip-address = (ipv4-address | ipv6-address )
method = "IKEv2" / "dTLS" / ..
pattern = some IP address set
Behringer, et al. Expires April 15, 2018 [Page 58]
Internet-Draft An Autonomic Control Plane (ACP) October 2017
For each candidate configured remote ACP neighbor, the secure channel
protocol "method" is configured with its expected local IP address
and remote transport endpoint. Transport protocol and port number
for the remote transport endpoint are usually not necessary to
configure if defaults for the secure channel protocol method exist.
This is the same information that would be communicated via DULL for
L2 adjacent candidate ACP neighbors. DULL is not used because the
remote IP address would need to be configured anyhow and if the
remote transport address would not be configured but learned via DULL
then this would create a third party attack vector.
The secure channel method leverages the configuration to filter
incoming connection requests by the remote IP address. This is
supplemental security. The primary security is via the mutual domain
certificate based authentication of the secure channel protocol.
On a hub node, the remote IP address may be set to some pattern
instead of explicit IP addresses. In this case, the node does not
attempt to initiate secure channel connections but only acts as their
responder. This allows for simple hub&spoke setups for the ACP where
some method (subject to further specification) provisions the
transport-address of hubs into spokes and hubs accept connections
from any spokes. The typical use case for this are spokes connecting
via the Internet to hubs. For example, this would be simple
extension to BRSKI to allow zero-touch security across the Internet.
Unlike adjacent ACP neighbor connections, configured remote ACP
neighbor connections can also be across IPv4. Not all (future)
secure channel methods may support running IPv6 (as used in the ACP
across the secure channel connection) over IPv4 encapsulation.
Unless the secure channel method supports PMTUD, it needs to be set
up with minimum MTU or the path mtu (pmtu) should be configured.
8.2.2. Tunneled Remote ACP Neighbor
An IPinIP, GRE or other form of pre-existing tunnel is configured
between two remote ACP peers and the virtual interfaces representing
the tunnel are configured to "ACP enable". This will enable IPv6
link local addresses and DULL on this tunnel. In result, the tunnel
is used for normal "L2 adjacent" candidate ACP neighbor discovery
with DULL and secure channel setup procedures described in this
document.
Tunneled Remote ACP Neighbor requires two encapsulations: the
configured tunnel and the secure channel inside of that tunnel. This
makes it in general less desirable than Configured Remote ACP
Behringer, et al. Expires April 15, 2018 [Page 59]
Internet-Draft An Autonomic Control Plane (ACP) October 2017
Neighbor. Benefits of tunnels are that it may be easier to implement
because there is no change to the ACP functionality - just running it
over a virtual (tunnel) interface instead of only native interfaces.
The tunnel itself may also provide PMTUD while the secure channel
method may not. Or the tunnel mechanism is permitted/possible
through some firewall while the secure channel method may not.
8.2.3. Summary
Configured/Tunneled Remote ACP neighbors are less "indestructible"
than L2 adjacent ACP neighbors based on link local addressing, since
they depend on more correct data-plane operations, such as routing
and global addressing.
Nevertheless, these options may be crucial to incrementally deploy
the ACP, especially if it is meant to connect islands across the
Internet. Implementations SHOULD support at least Tunneled Remote
ACP Neighbors via GRE tunnels - which is likely the most common
router-to-router tunneling protocol in use today.
Future work could envisage an option where the edge nodes of the L3
cloud is configured to automatically forward ACP discovery messages
to the right exit point. This optimisation is not considered in this
document.
9. Benefits (Informative)
9.1. Self-Healing Properties
The ACP is self-healing:
o New neighbors will automatically join the ACP after successful
validation and will become reachable using their unique ULA
address across the ACP.
o When any changes happen in the topology, the routing protocol used
in the ACP will automatically adapt to the changes and will
continue to provide reachability to all nodes.
o If the domain certificate of an existing ACP node gets revoked, it
will automatically be denied access to the ACP as its domain
certificate will be validated against a Certificate Revocation
List during authentication. Since the revocation check is only
done at the establishment of a new security association, existing
ones are not automatically torn down. If an immediate disconnect
is required, existing sessions to a freshly revoked node can be
re-set.
Behringer, et al. Expires April 15, 2018 [Page 60]
Internet-Draft An Autonomic Control Plane (ACP) October 2017
The ACP can also sustain network partitions and mergers. Practically
all ACP operations are link local, where a network partition has no
impact. Nodes authenticate each other using the domain certificates
to establish the ACP locally. Addressing inside the ACP remains
unchanged, and the routing protocol inside both parts of the ACP will
lead to two working (although partitioned) ACPs.
There are few central dependencies: A certificate revocation list
(CRL) may not be available during a network partition; a suitable
policy to not immediately disconnect neighbors when no CRL is
available can address this issue. Also, a registrar or Certificate
Authority might not be available during a partition. This may delay
renewal of certificates that are to expire in the future, and it may
prevent the enrolment of new nodes during the partition.
After a network partition, a re-merge will just establish the
previous status, certificates can be renewed, the CRL is available,
and new nodes can be enrolled everywhere. Since all nodes use the
same trust anchor, a re-merge will be smooth.
Merging two networks with different trust anchors requires the trust
anchors to mutually trust each other (for example, by cross-signing).
As long as the domain names are different, the addressing will not
overlap (see Section 6.10).
It is also highly desirable for implementation of the ACP to be able
to run it over interfaces that are administratively down. If this is
not feasible, then it might instead be possible to request explicit
operator override upon administrative actions that would
administratively bring down an interface across which the ACP is
running. Especially if bringing down the ACP is known to disconnect
the operator from the node. For example any such down administrative
action could perform a dependency check to see if the transport
connection across which this action is performed is affected by the
down action (with default RPL routing used, packet forwarding will be
symmetric, so this is actually possible to check).
9.2. Self-Protection Properties
9.2.1. From the outside
As explained in Section 6, the ACP is based on secure channels built
between nodes that have mutually authenticated each other with their
domain certificates. The channels themselves are protected using
standard encryption technologies like DTLS or IPsec which provide
additional authentication during channel establishment, data
integrity and data confidentiality protection of data inside the ACP
and in addition, provide replay protection.
Behringer, et al. Expires April 15, 2018 [Page 61]
Internet-Draft An Autonomic Control Plane (ACP) October 2017
An attacker will not be able to join the ACP unless having a valid
domain certificate, also packet injection and sniffing traffic will
not be possible due to the security provided by the encryption
protocol.
The ACP also serves as protection (through authentication and
encryption) for protocols relevant to OAM that may not have secured
protocol stack options or where implementation or deployment of those
options fails on some vendor/product/customer limitations. This
includes protocols such as SNMP, NTP/PTP, DNS, DHCP, syslog,
Radius/Diameter/TACACS, IPFIX/Netflow - just to name a few.
Protection via the ACP secure hop-by-hop channels for these protocols
is meant to be only a stopgap though: The ultimate goal is for these
and other protocols to use end-to-end encryption utilizing the domain
certificate and rely on the ACP secure channels primarily for zero-
touch reliable connectivity, but not primarily for security.
The remaining attack vector would be to attack the underlying AN
protocols themselves, either via directed attacks or by denial-of-
service attacks. However, as the ACP is built using link-local IPv6
address, remote attacks are impossible. The ULA addresses are only
reachable inside the ACP context, therefore, unreachable from the
data-plane. Also, the ACP protocols should be implemented to be
attack resistant and not consume unnecessary resources even while
under attack.
9.2.2. From the inside
The security model of the ACP is based on trusting all members of the
group of nodes that do receive an ACP domain certificate for the same
domain. Attacks from the inside by a compromised group member are
therefore the biggest challenge.
Group members must overall the secured so that there are no easy way
to compromise them, such as data-plane accessible privilege level
with simple passwords. This is a lot easier to do in devices whose
software is designed from the ground up with security in mind than
with legacy software based system where ACP is added on as another
feature.
As explained above, traffic across the ACP SHOULD still be end-to-end
encrypted whenever possible. This includes traffic such as GRASP,
EST and BRSKI inside the ACP. This minimizes man in the middle
attacks by compromised ACP group members. Such attackers cannot
eavesdrop or modify communications, they can just filter them (which
is unavoidable by any means).
Behringer, et al. Expires April 15, 2018 [Page 62]
Internet-Draft An Autonomic Control Plane (ACP) October 2017
Further security can be achieved by constraining communication
patterns inside the ACP, for example through roles that could be
encoded into the domain certificates. This is subject for future
work.
9.3. The Administrator View
An ACP is self-forming, self-managing and self-protecting, therefore
has minimal dependencies on the administrator of the network.
Specifically, since it is independent of configuration, there is no
scope for configuration errors on the ACP itself. The administrator
may have the option to enable or disable the entire approach, but
detailed configuration is not possible. This means that the ACP must
not be reflected in the running configuration of nodes, except a
possible on/off switch.
While configuration is not possible, an administrator must have full
visibility of the ACP and all its parameters, to be able to do
trouble-shooting. Therefore, an ACP must support all show and debug
options, as for any other network function. Specifically, a network
management system or controller must be able to discover the ACP, and
monitor its health. This visibility of ACP operations must clearly
be separated from visibility of data-plane so automated systems will
never have to deal with ACP aspect unless they explicitly desire to
do so.
Since an ACP is self-protecting, a node not supporting the ACP, or
without a valid domain certificate cannot connect to it. This means
that by default a traditional controller or network management system
cannot connect to an ACP. See Section 8.1.1 for more details on how
to connect an NMS host into the ACP.
10. Further Considerations (Informative)
The following sections cover topics that are beyond the primary cope
of this document (e.g.: bootstrap), that explain decisions made in
this document (e.g.: choice of GRASP) or that explain desirable
extensions or implementation details for the ACP that are not
considered to be appropriate to standardize in this document.
10.1. BRSKI Bootstrap (ANI)
[I-D.ietf-anima-bootstrapping-keyinfra] (BRSKI) describes how nodes
with an IDevID certificate can securely and zero-touch enroll with a
domain certificate (LDevID) to support the ACP. BRSKI also leverages
the ACP to enable zero touch bootstrap of new nodes across networks
without any configuration requirements across the transit nodes
(e.g.: no DHCP/DS forwarding/server setup). This includes otherwise
Behringer, et al. Expires April 15, 2018 [Page 63]
Internet-Draft An Autonomic Control Plane (ACP) October 2017
not configured networks as described in Section 3.2. Therefore BRSKI
in conjunction with ACP provides for a secure and zero-touch
management solution for complete networks. Nodes supporting such an
infrastructure (BRSKI and ACP) are called ANI nodes (Autonomic
Networking Infrastructure), see [I-D.ietf-anima-reference-model].
Nodes that do not support an IDevID but only an (insecure) vendor
specific Unique Device Identifier (UDI) or nodes whose manufacturer
does not support a MASA could use some future security reduced
version of BRSKI.
When BRSKI is used to provision a domain certificate (which is called
enrollment), the registrar (acting as an EST server) must include the
subjectAltName / rfc822Name encoded ACP address and domain name to
the enrolling node (called pledge) via its response to the pledges
EST CSR Attribute request that is mandatory in BRSKI.
The Certificate Authority in an ACP network must not change the
subjectAltName / rfc822Name in the certificate. The ACP nodes can
therefore find their ACP address and domain using this field in the
domain certificate, both for themselves, as well as for other nodes.
The use of BRSKI in conjunction with the ACP can also help to further
simplify maintenance and renewal of domain certificates. Instead of
relying on CRL, the lifetime of certificates can be made extremely
small, for example in the order of hours. When a node fails to
connect to the ACP within its certificate lifetime, it cannot connect
to the ACP to renew its certificate across it (using just EST), but
it can still renew its certificate as an "enrolled/expired pledge"
via the BRSKI bootstrap proxy. This requires only that the BRSKI
registrar honors expired domain certificates and that the pledge
first attempts to perform TLS authentication for BRSKI bootstrap with
its expired domain certificate - and only reverts to its IDevID when
this fails. This mechanism could also render CRLs unnecessary
because the BRSKI registrar in conjunction with the CA would not
renew revoked certificates - only a "no-not-renew" list would be
necessary on registrars/CA.
In the absence of BRSKI or less secure variants thereof, provisioning
of certificates may involve one or more touches or non-standardized
automation. Node vendors usually support provisioning of
certificates into nodes via PKCS#7 (see [RFC2315]) and may support
this provisioning through vendor specific models via Netconf
([RFC6241]). If such nodes also support Netconf Zero-Touch
([I-D.ietf-netconf-zerotouch]) then this can be combined to zero-
touch provisioning of domain certificates into nodes. Unless there
are equivalent integration of Netconf connections across the ACP as
there is in BRSKI, this combination would not support zero-touch
bootstrap across a not configured network though.
Behringer, et al. Expires April 15, 2018 [Page 64]
Internet-Draft An Autonomic Control Plane (ACP) October 2017
10.2. ACP (and BRSKI) Diagnostics
Even though ACP and ANI in general are taking out many manual
configuration mistakes through their automation, it is important to
provide good diagnostics for them.
The basic diagnostics is support of (yang) data models representing
the complete (auto-)configuration and operational state of all
components: BRSKI, GRASP, ACP and the infrastructure used by them:
TLS/dTLS, IPsec, certificates, trust anchors, time, VRF and so on.
While necessary, this is not sufficient:
Simply representing the state of components does not allow operators
to quickly take action - unless they do understand how to interpret
the data, and that can mean a requirement for deep understanding of
all components and how they interact in the ACP/ANI.
Diagnostic supports should help to quickly answer the questions
operators are expected to ask, such as "is the ACP working correctly
?", or "why is there no ACP connection to a known neighboring node ?"
In current network management approaches, the logic to answer these
questions is most often built as centralized diagnostics software
that leverages the above mentioned data models. While this approach
is feasible for components utilizing the ANI, it is not sufficient to
diagnose the ANI itself:
o Developing the logic to identify common issues requires
operational experience with the components of the ANI. Letting
each management system define its own analysis is inefficient. As
much as possible, future work should attempt to standardize data
models that support common error diagnostic.
o When the ANI is not operating correctly, it may not be possible to
run diagnostics from remote because of missing connectivity. The
ANI should therefore have diagnostic capabilities available
locally on the nodes themselves.
o Certain operations are difficult or impossible to monitor in real-
time, such as initial bootstrap issues in a network location where
no capabilities exist to attach local diagnostics. Therefore it
is important to also define means of capturing (logging)
diagnostics locally for later retrieval. Ideally, these captures
are also non-volatile so that they can survive extended power-off
conditions - for example when a device that fails to be brought up
zero-touch is being sent back for diagnostics at a more
appropriate location.
Behringer, et al. Expires April 15, 2018 [Page 65]
Internet-Draft An Autonomic Control Plane (ACP) October 2017
The most simple form of diagnostics answering questions like the
above is to represent the relevant information sequentially in
dependency order, so that the first non-expected/non-operational item
is the most likely root cause. Or just log/highlight that item. For
example:
Q: Is ACP operational to accept neighbor connections:
o Check if any potentially necessary configuration to make ACP/ANI
operational are correct (see Section 10.3 for a discussion of such
commands).
o Does the system time look reasonable, or could it be the default
system time after clock chip battery failure (certificate checks
depend on reasonable notion of time).
o Does the node have keying material - domain certificate, trust
anchors.
o If no keying material and ANI is supported/enabled, check the
state of BRSKI (not detailed in this example).
o Check the validity of the domain certificate:
* Does the certificate authenticate against the trust anchor ?
* Has it been revoked ?
* Was the last scheduled attempt to retrieve a CRL successful
(e.g.: do we know that our CRL information is up to date).
* Is the certificate valid: validity start time in the past,
expiration time in the future ?
* Does the certificate have a correctly formatted ACP information
field ?
o Was the ACP VRF successfully created ?
o Is ACP enabled on one or more interfaces that are up and running ?
If all this looks good, the ACP should be running locally "fine" -
but we did not check any ACP neighborships.
Question: why does the node not create a working ACP connection to a
neighbor on an interface ?
Behringer, et al. Expires April 15, 2018 [Page 66]
Internet-Draft An Autonomic Control Plane (ACP) October 2017
o Is the interface physically up ? Does it have an IPv6 link-local
address ?
o Is it enabled for ACP ?
o Do we successfully send DULL GRASP messages to the interface (link
layer errors) ?
o Do we receive DULL GRASP messages on the interface ? If not, some
intervening L2 equipment performing bad MLD snooping could have
caused problems. Provide e.g.: diagnostics of the MLD querier
IPv6 and MAC address.
o Do we see the ACP objective in any DULL GRASP message from that
interface ? Diagnose the supported secure channel methods.
o Do we know the MAC address of the neighbor with the ACP objective
? If not, diagnose SLAAC/ND state.
o When did we last attempt to build an ACP secure channel to the
neighbor ?
o If it failed, why:
* Did the neighbor close the connection on us or did we close the
connection on it because the domain certificate membership
failed ?
* If the neighbor closed the connection on us, provide any error
diagnostics from the secure channel protocol.
* If we failed the attempt, display our local reason:
+ There was no common secure channel protocol supported by the
two neighbors (this could not happen on nodes supporting
this specification because it mandates common support for
IPsec).
+ The ACP domain certificate membership check (Section 6.1.2)
fails:
- The neighbors certificate does not have the required
trust anchor. Provide diagnostics which trust anchor it
has (can identify whom the device belongs to).
- The neighbors certificate does not have the same domain
(or no domain at all). Diagnose domain-name and
potentially other other cert info.
Behringer, et al. Expires April 15, 2018 [Page 67]
Internet-Draft An Autonomic Control Plane (ACP) October 2017
- The neighbors certificate has been revoked or could not
be authenticated by OCSP.
- The neighbors certificate has expired - or is not yet
valid.
* Any other connection issues in e.g.: IKEv2 / IPsec, dTLS ?".
Question: Is the ACP operating correctly across its secure channels
?:
o Are there one or more active ACP neighbors with secure channels ?
o Is the RPL routing protocol for the ACP running ?
o Is there a default route to the root in the ACP routing table ?
o Is there for each direct ACP neighbor not reachable over the ACP
virtual interface to the root a route in the ACP routing table ?
o Is ACP GRASP running ?
o Is at least one SRV.est objective cached (to support certificate
renewal) ?
o Is there at least one BRSKI registrar objective cached (in case
BRSKI is supported)
o Is BRSKI proxy operating normally on all interfaces where ACP is
operating ?
o ...
These lists are not necessarily complete, but illustrate the
principle and show that there are variety of issues ranging from
normal operational causes (a neighbor in another ACP domain) over
problems in the credentials management (certificate lifetimes),
explicit security actions (revocation) or unexpected connectivity
issues (intervening L2 equipment).
The items so far are illustrating how the ANI operations can be
diagnosed with passive observation of the operational state of its
components including historic/cached/counted events. This is not
necessary sufficient to provide good enough diagnostics overall:
The components of ACP and BRSKI are designed with security in mind
but they do not attempt to provide diagnostics for building the
network itself. Consider two examples:
Behringer, et al. Expires April 15, 2018 [Page 68]
Internet-Draft An Autonomic Control Plane (ACP) October 2017
1. BRSKI does not allow for a neighboring device to identify the
pledges certificate (IDevID). Only the selected BRSKI-registrar
can do this, but it may be difficult to disseminate information
about undesired pledges from those registrars to locations/nodes
where information about those pledges is desired.
2. LLDP disseminates information about nodes to their immediate
neighbors, such as node model/type/software and interface name/
number of the connection. This information is often helpful or
even necessary in network diagnostics. It can equally considered
to be too insecure to make this information available unprotected
to all possible neighbors.
An "interested adjacent party" can always determine the IDevID of a
BRSKI pledge by behaving like a BRSKI proxy/registrar. Therefore the
IDevID of a BRSKI pledge is not meant to be protected - it just has
to be queried and is not signaled unsolicited (as it would be in
LLDP) so that other observers on the same subnet can determine who is
an "interested adjacent party".
Desirable options for additional diagnostics subject to future work
include:
1. Determine if LLDP should be a recommended functionality for ANI
devices to improve diagnostics, and if so, which information
elements it should signal (insecure).
2. In alternative to LLDP, A DULL GRASP diagnostics objective could
be defined to carry these information elements.
3. The IDevID of BRSKI pledges should be included in the selected
insecure diagnostics option.
4. A richer set of diagnostics information should be made available
via the secured ACP channels, using either single-hop GRASP or
network wide "topology discovery" mechanisms.
10.3. Enabling and disabling ACP/ANI
Both ACP and BRSKI require interfaces to be operational enough to
support sending/receiving their packets. In node types where
interfaces are by default (e.g.: without operator configuration)
enabled, such as most L2 switches, this would be less of a change in
behavior than in most L3 devices (e.g.: routers), where interfaces
are by default disabled. In almost all network devices it is common
though for configuration to change interfaces to a physically
disabled state and that would break the ACP.
Behringer, et al. Expires April 15, 2018 [Page 69]
Internet-Draft An Autonomic Control Plane (ACP) October 2017
In this section, we discuss a suggested operational model to enable/
disable interfaces and nodes for ACP/ANI in a way that minimizes the
risk of operator action to break the ACP in this way, and that also
minimizes operator surprise when ACP/ANI becomes supported in node
software.
10.3.1. Filtering for non-ACP/ANI packets
Whenever this document refers to enabling an interface for ACP (or
BRSKI), it only requires to permit the interface to send/receive
packets necessary to operate ACP (or BRSKI) - but not any other data-
plane packets. Unless the data-plane is explicitly configured/
enabled, all packets not required for ACP/BRSKI should be filtered on
input and output:
Both BRSKI and ACP require link-local only IPv6 operations on
interfaces and DULL GRASP. IPv6 link-local operations means the
minimum signaling to auto-assign an IPv6 link-local address and talk
to neighbors via their link-local address: SLAAC (Stateless Address
Auto-Configuration - [RFC4862]) and ND (Neighbor Discovery -
[RFC4861]). When the device is a BRSKI pledge, it may also require
TCP/TLS connections to BRSKI proxies on the interface. When the
device has keying material, and the ACP is running, it requires DULL
GRASP packets and packets necessary for the secure-channel mechanism
it supports, e.g.: IKEv2 and IPsec ESP packets or dTLS packets to the
IPv6 link-local address of an ACP neighbor on the interface. It also
requires TCP/TLS packets for its BRSKI proxy functionality, if it
does support BRSKI.
10.3.2. Admin Down State
Interfaces on most network equipment have at least two states: "up"
and "down". These may have product specific names. "down" for
example could be called "shutdown" and "up" could be called "no
shutdown". The "down" state disables all interface operations down
to the physical level. The "up" state enables the interface enough
for all possible L2/L3 services to operate on top of it and it may
also auto-enable some subset of them. More commonly, the operations
of various L2/L3 services is controlled via additional node-wide or
interface level options, but they all become only active when the
interface is not "down". Therefore an easy way to ensure that all
L2/L3 operations on an interface are inactive is to put the interface
into "down" state. The fact that this also physically shuts down the
interface is in many cases just a side effect, but it may be
important in other cases (see below).
To provide ACP/ANI resilience against operators configuring
interfaces to "down" state, this document recommends to separate the
Behringer, et al. Expires April 15, 2018 [Page 70]
Internet-Draft An Autonomic Control Plane (ACP) October 2017
"down" state of interfaces into an "admin down" state where the
physical layer is kept running and ACP/ANI can use the interface and
a "physical down" state. Any existing "down" configurations would
map to "admin down". In "admin down", any existing L2/L3 services of
the data-plane should see no difference to "physical down" state. To
ensure that no data-plane packets could be sent/received, packet
filtering could be established automatically as described above in
Section 10.3.1.
As necessary (see discussion below) new configuration options could
be introduced to issue "physical down". The options should be
provided with additional checks to minimize the risk of issuing them
in a way that breaks the ACP without automatic restoration. For
example they could be denied to be issued from a control connection
(netconf/ssh) that goes across the interface itself ("do not
disconnect yourself"). Or they could be performed only temporary and
only be made permanent with additional later reconfirmation.
In the following sub-sections important aspects to the introduction
of "admin down" state are discussed.
10.3.2.1. Security
Interfaces are physically brought down (or left in default down
state) as a form of security. "Admin down" state as described above
provides also a high level of security because it only permits ACP/
ANI operations which are both well secured. Ultimately, it is
subject to security review for the deployment whether "admin down" is
a feasible replacement for "physical down".
The need to trust into the security of ACP/ANI operations need to be
weighed against the operational benefits of permitting this: Consider
the typical example of a CPE (customer premises equipment) with no
on-site network expert. User ports are in physical down state unless
explicitly configured not to be. In a misconfiguration situation,
the uplink connection is incorrectly plugged into such a user port.
The device is disconnected from the network and therefore no
diagnostics from the network side is possible anymore.
Alternatively, all ports default to "admin down". The ACP (but not
the data-plane) would still automatically form. Diagnostics from the
network side is possible and operator reaction could include to
either make this port the operational uplink port or to instruct re-
cabling. Security wise, only ACP/ANI could be attacked, all other
functions are filtered on interfaces in "admin down" state.
Behringer, et al. Expires April 15, 2018 [Page 71]
Internet-Draft An Autonomic Control Plane (ACP) October 2017
10.3.2.2. Fast state propagation and Diagnostics
"Physical down" state propagates on many interface types (e.g.:
Ethernet) to the other side. This can trigger fast L2/L3 protocol
reaction on the other side and "admin down" would not have the same
(fast) result.
Bringing interfaces to "physical down" state is to the best of our
knowledge always a result of operator action, but today, never the
result of (autonomous) L2/L3 services running on the nodes.
Therefore one option is to change the operator action to not rely on
link-state propagation anymore. This may not be possible when both
sides are under different operator control, but in that case it is
unlikely that the ACP is running across the link and actually putting
the interface into "physical down" state may still be a good option.
Ideally, fast physical state propagation is replaced by fast software
driven state propagation. For example a DULL GRASP "admin-state"
objective could be used to autoconfigure a BFD session between the
two sides of the link that would be used to propagate the "up" vs.
admin down state.
Triggering physical down state may also be used as a mean of
diagnosing cabling in the absence of easier methods. It is more
complex than automated neighbor diagnostics because it requires
coordinated remote access to both (likely) sides of a link to
determine whether up/down toggling will cause the same reaction on
the remote side.
See Section 10.2 for a discussion about how LLDP and/or diagnostics
via GRASP could be used to provide neighbor diagnostics, and
therefore hopefully eliminating the need for "physical down" for
neighbor diagnostics - as long as both neighbors support ACP/ANI.
10.3.2.3. Low Level Link Diagnostics
"Physical down" is performed to diagnose low-level interface behavior
when higher layer services (e.g.: IPv6) are not working. Especially
Ethernet links are subject to a wide variety of possible wrong
configuration/cablings if they do not support automatic selection of
variable parameters such as speed (10/100/1000 Mbps), crossover
(Auto-MDIX) and connector (fiber, copper - when interfaces have
multiple but can only enable one at a time). The need for low level
link diagnostic can therefore be minimized by using fully
autoconfiguring links.
In addition to "Physical down", low level diagnostics of Ethernet or
other interfaces also involve the creation of other states on
Behringer, et al. Expires April 15, 2018 [Page 72]
Internet-Draft An Autonomic Control Plane (ACP) October 2017
interfaces, such as physical loopback (internal and/or external) or
bringing down all packet transmissions for reflection/cable-length
measurements. Any of these options would disrupt ACP as well.
In cases where such low-level diagnostics of an operational link is
desired but where the link could be a single point of failure for the
ACP, ASA on both nodes of the link could perform a negotiated
diagnostics that automatically terminates in a predetermined manner
without dependence on external input ensuring the link will become
operational again.
10.3.2.4. Power Consumption
Power consumption of "physical down" interfaces may be significantly
lower than those in "admin down" state, for example on long range
fiber interfaces. Assuming reasonable clocks on devices, mechanisms
for infrequent periodic probing could allow to automatically
establish ACP connectivity across such links. Bring up interfaces
for 5 seconds to probe if there is an ACP neighbor on the remote end
every 500 seconds = 1% power consumption.
10.3.3. Interface level ACP/ANI enable
The interface level configuration option "ACP enable" enables ACP
operations on an interface, starting with ACP neighbor discovery via
DULL GRAP. The interface level configuration option "ANI enable" on
nodes supporting BRSKI and ACP starts with BRSKI pledge operations
when there is no domain certificate on the node. On ACP/BRSKI nodes,
"ACP enable" may not need to be supported, but only "ANI enable".
Unless overridden by global configuration options (see later), "ACP/
ANI enable" will result in "down" state on an interface to behave as
"admin down".
10.3.4. Which interfaces to auto-enable ?
(Section 6.3) requires that "ACP enable" is automatically set on
native interfaces, but not on non-native interfaces (reminder: a
native interface is one that exists without operator configuration
action such as physical interfaces in physical devices).
Ideally, ACP enable is set automatically on all interfaces that
provide access to additional connectivity that allows to reach more
nodes of the ACP domain. The best set of interfaces necessary to
achieve this is not possible to determine automatically. Native
interfaces are the best automatic approximation.
Consider an ACP domain of ACP nodes transitively connected via native
interfaces. A data-plane tunnel between two of these nodes that are
Behringer, et al. Expires April 15, 2018 [Page 73]
Internet-Draft An Autonomic Control Plane (ACP) October 2017
non-adjacent is created and "ACP enable" is set for that tunnel. ACP
RPL sees this tunnel as just as a single hop. Routes in the ACP
would use this hop as an attractive path element to connect regions
adjacent to the tunnel nodes. In result, the actual hop-by-hop paths
used by traffic in the ACP can become worse. In addition, correct
forwarding in the ACP now depends on correct data-plane forwarding
config including QoS, filtering and other security on the data-plane
path across which this tunnel runs. This is the main issue why "ACP/
ANI enable" should not be set automatically on non-native interfaces.
If the tunnel would connect two previously disjoint ACP regions, then
it likely would be useful for the ACP. A data-plane tunnel could
also run across nodes without ACP and provide additional connectivity
for an already connected ACP network. The benefit of this additional
ACP redundancy has to be weighed against the problems of relying on
the data-plane. If a tunnel connects two separate ACP regions: how
many tunnels should be created to connect these ACP regions reliably
enough ? Between which nodes ? These are all standard tunneled
network design questions not specific to the ACP, and there are no
generic fully automated answers.
Instead of automatically setting "ACP enable" on these type of
interfaces, the decision needs to be based on the use purpose of the
non-native interface and "ACP enable" needs to be set in conjunction
with the mechanism through which the non-native interface is created/
configured.
In addition to explicit setting of "ACP/ANI enable", non-native
interfaces also need to support configuration of the ACP RPL cost of
the link - to avoid the problems of attracting too much traffic to
the link as described above.
Even native interfaces may not be able to automatically perform BRSKI
or ACP because they may require additional operator input to become
operational. Example include DSL interfaces requiring PPPoE
credentials or mobile interfaces requiring credentials from a SIM
card. Whatever mechanism is used to provide the necessary config to
the device to enable the interface can also be expanded to decide on
whether or not to set "ACP/ANI enable".
The goal of automatically setting "ACP/ANI enable" on interfaces
(native or not) is to eliminate unnecessary "touches" to the node to
make its operation as much as possible "zero-touch" with respect to
ACP/ANI. If there are "unavoidable touches" such a creating/
configuring a non-native interface or provisioning credentials for a
native interface, then "ACP/ANI enable" should be added as an option
to that "touch". If a wrong "touch" is easily fixed (not creating
another high-cost touch), then the default should be not to enable
Behringer, et al. Expires April 15, 2018 [Page 74]
Internet-Draft An Autonomic Control Plane (ACP) October 2017
ANI/ACP, and if it is potentially expensive or slow to fix (e.g.:
parameters on SIM card shipped to remote location), then the default
should be to enable ACP/ANI.
10.3.5. Node Level ACP/ANI enable
A node level command "ACP/ANI enable [up-if-only]" enables ACP or ANI
on the node (ANI = ACP + BRSKI). Without this command set, any
interface level "ACP/ANI enable" is ignored. Once set, ACP/ANI will
operate interface where "ACP/ANI enable" is set. Setting of
interface level "ACP/ANI enable" is either automatic (default) or
explicit through operator action as described in the previous
section.
If the option "up-if-only" is selected, the behavior of "down"
interfaces is unchanged, and ACP/ANI will only operate on interfaces
where "ACP/ANI enable" is set and that are "up". When it is not set,
then "down" state of interfaces with "ACP/ANI enable" is modified to
behave as "admin down".
10.3.5.1. Brownfield nodes
A "brownfield" node is one that already has a configured data-plane.
Executing global "ACP/ANI enable [up-if-only]" on each node is the
only command necessary to create an ACP across a network of
brownfield nodes once all the nodes have a domain certificate. When
BRSKI is used ("ANI enable"), provisioning of the certificates only
requires set-up of a single BRSKI-registrar node which could also
implement a CA for the network. This is the most simple way to
introduce ACP/ANI into existing (== brownfield) networks.
The need to explicitly enable ACP/ANI is especially important in
brownfield nodes because otherwise software updates may introduce
support for ACP/ANI: Automatic enablement of ACP/ANI in networks
where the operator does not only not want ACP/ANI but where he likely
never even heard of it could be quite irritating to him. Especially
when "down" behavior is changed to "admin down".
Automatically setting "ANI enable" on brownfield nodes where the
operator is unaware of it could also be a critical security issue
depending on the vouchers used by BRKSI on these nodes. An attacker
could claim to be the owner of these devices and create an ACP that
the attacker has access/control over. In network where the operator
explicitly wants to enable the ANI this could not happen, because he
would create a BRSKI registrar that would discover attack attempts.
Nodes requiring "ownership vouchers" would not be subject to that
attack. See [I-D.ietf-anima-bootstrapping-keyinfra] for more
Behringer, et al. Expires April 15, 2018 [Page 75]
Internet-Draft An Autonomic Control Plane (ACP) October 2017
details. Note that a global "ACP enable" alone is not subject to
these type of attacks, because it always depends on some other
mechanism first to provision domain certificates into the device.
10.3.5.2. Greenfield nodes
A "greenfield" node is one that did not have any prior configuration.
For greenfield nodes, only "ANI enable" is relevant. If another
mechanism than BRSKI is used to (zero-touch) bootstrap a node, then
it is up to that mechanism to provision domain certificates and to
set global "ACP enable" as desired.
Nodes supporting full ANI functionality set "ANI enable"
automatically when they decide that they are greenfield, e.g.: that
they are powering on from factory condition. They will then put all
native interfaces into "admin down" state and start to perform BRSKI
pledge functionality - and once a domain certificate is enrolled they
automatically enable ACP.
Attempts for BRSKI pledge operations in greenfield state should
terminate automatically when another method of configuring the node
is used. Methods that indicate some form of physical possession of
the device such as configuration via the serial console could lead to
immediate termination of BRSKI, while other parallel
autoconfiguration methods subject to remote attacks might lead to
BRSKI termination only after they were successful. Details of this
may vary widely over different type of nodes. When BRSKI pledge
operation terminates, this will automatically unset "ANI enable" and
should terminate any temporarily needed state on the device to
perform BRSKI - DULL GRASP, BRSKI pledge and any IPv6 configuration
on interfaces.
10.3.6. Undoing ANI/ACP enable
Disabling ANI/ACP by undoing "ACP/ANI enable" is a risk for the
reliable operations of the ACP if it can be executed by mistake or
unauthorized. This behavior could be influenced through some
additional property in the certificate (e.g.: in the domain
information extension field) subject to future work: In an ANI
deployment intended for convenience, disabling it could be allowed
without further constraints. In an ANI deployment considered to be
critical more checks would be required. One very controlled option
would be to not permit these commands unless the domain certificate
has been revoked or is denied renewal. Configuring this option would
be a parameter on the BRSKI registrar(s). As long as the node did
not receive a domain certificate, undoing "ANI/ACP enable" should not
have any additional constraints.
Behringer, et al. Expires April 15, 2018 [Page 76]
Internet-Draft An Autonomic Control Plane (ACP) October 2017
10.3.7. Summary
Node-wide "ACP/ANI enable [up-if-only]" commands enable the operation
of ACP/ANI. This is only auto-enabled on ANI greenfield devices,
otherwise it must be configured explicitly.
If the option "up-if-only" is not selected, interfaces enabled for
ACP/ANI interpret "down" state as "admin down" and not "physical
down". In "admin-down" all non-ACP/ANI packets are filtered, but the
physical layer is kept running to permit ACP/ANI to operate.
(New) commands that result in physical interruption ("physical down",
"loopback) of ACP/ANI enabled interfaces should be built to protect
continuance or reestablishment of ACP as much as possible.
Interface level "ACP/ANI enable" control per-interface operations.
It is enabled by default on native interfaces and has to be
configured explicitly on other interfaces.
Disabling "ACP/ANI enable" global and per-interface should have
additional checks to minimize undesired breakage of ACP. The degree
of control could be a domain wide parameter in the domain
certificates.
10.4. ACP Neighbor discovery protocol selection
This section discusses why GRASP DULL was chosen as the discovery
protocol for L2 adjacent candidate ACP neighbors. The contenders
considered where GRASP, mDNS or LLDP.
10.4.1. LLDP
LLDP (and Cisco's similar CDP) are example of L2 discovery protocols
that terminate their messages on L2 ports. If those protocols would
be chosen for ACP neighbor discovery, ACP neighbor discovery would
therefore also terminate on L2 ports. This would prevent ACP
construction over non-ACP capable but LLDP or CDP enabled L2
switches. LLDP has extensions using different MAC addresses and this
could have been an option for ACP discovery as well, but the
additional required IEEE standardization and definition of a profile
for such a modified instance of LLDP seemed to be more work than the
benefit of "reusing the existing protocol" LLDP for this very simple
purpose.
Behringer, et al. Expires April 15, 2018 [Page 77]
Internet-Draft An Autonomic Control Plane (ACP) October 2017
10.4.2. mDNS and L2 support
mDNS [RFC6762] with DNS-SD RRs (Resource Records) as defined in
[RFC6763] is a key contender as an ACP discovery protocol. because it
relies on link-local IP multicast, it does operates at the subnet
level, and is also found in L2 switches. The authors of this
document are not aware of mDNS implementation that terminate their
mDNS messages on L2 ports instead of the subnet level. If mDNS was
used as the ACP discovery mechanism on an ACP capable (L3)/L2 switch
as outlined in Section 7, then this would be necessary to implement.
It is likely that termination of mDNS messages could only be applied
to all mDNS messages from such a port, which would then make it
necessary to software forward any non-ACP related mDNS messages to
maintain prior non-ACP mDNS functionality. Adding support for ACP
into such L2 switches with mDNS could therefore create regression
problems for prior mDNS functionality on those nodes. With low
performance of software forwarding in many L2 switches, this could
also make the ACP risky to support on such L2 switches.
10.4.3. Why DULL GRASP
LLDP was not considered because of the above mentioned issues. mDNS
was not selected because of the above L2 mDNS considerations and
because of the following additional points:
If mDNS was not already existing in a node, it would be more work to
implement than DULL GRASP, and if an existing implementation of mDNS
was used, it would likely be more code space than a separate
implementation of DULL GRASP or a shared implementation of DULL GRASP
and GRASP in the ACP.
10.5. Choice of routing protocol (RPL)
This Appendix explains why RPL - "IPv6 Routing Protocol for Low-Power
and Lossy Networks ([RFC6550] was chosen as the default (and in this
specification only) routing protocol for the ACP. The choice and
above explained profile was derived from a pre-standard
implementation of ACP that was successfully deployed in operational
networks.
Requirements for routing in the ACP are:
o Self-management: The ACP must build automatically, without human
intervention. Therefore routing protocol must also work
completely automatically. RPL is a simple, self-managing
protocol, which does not require zones or areas; it is also self-
configuring, since configuration is carried as part of the
protocol (see Section 6.7.6 of [RFC6550]).
Behringer, et al. Expires April 15, 2018 [Page 78]
Internet-Draft An Autonomic Control Plane (ACP) October 2017
o Scale: The ACP builds over an entire domain, which could be a
large enterprise or service provider network. The routing
protocol must therefore support domains of 100,000 nodes or more,
ideally without the need for zoning or separation into areas. RPL
has this scale property. This is based on extensive use of
default routing. RPL also has other scalability improvements,
such as selecting only a subset of peers instead of all possible
ones, and trickle support for information synchronization.
o Low resource consumption: The ACP supports traditional network
infrastructure, thus runs in addition to traditional protocols.
The ACP, and specifically the routing protocol must have low
resource consumption both in terms of memory and CPU requirements.
Specifically, at edge nodes, where memory and CPU are scarce,
consumption should be minimal. RPL builds a destination-oriented
directed acyclic graph (DODAG), where the main resource
consumption is at the root of the DODAG. The closer to the edge
of the network, the less state needs to be maintained. This
adapts nicely to the typical network design. Also, all changes
below a common parent node are kept below that parent node.
o Support for unstructured address space: In the Autonomic
Networking Infrastructure, node addresses are identifiers, and may
not be assigned in a topological way. Also, nodes may move
topologically, without changing their address. Therefore, the
routing protocol must support completely unstructured address
space. RPL is specifically made for mobile ad-hoc networks, with
no assumptions on topologically aligned addressing.
o Modularity: To keep the initial implementation small, yet allow
later for more complex methods, it is highly desirable that the
routing protocol has a simple base functionality, but can import
new functional modules if needed. RPL has this property with the
concept of "objective function", which is a plugin to modify
routing behavior.
o Extensibility: Since the Autonomic Networking Infrastructure is a
new concept, it is likely that changes in the way of operation
will happen over time. RPL allows for new objective functions to
be introduced later, which allow changes to the way the routing
protocol creates the DAGs.
o Multi-topology support: It may become necessary in the future to
support more than one DODAG for different purposes, using
different objective functions. RPL allow for the creation of
several parallel DODAGs, should this be required. This could be
used to create different topologies to reach different roots.
Behringer, et al. Expires April 15, 2018 [Page 79]
Internet-Draft An Autonomic Control Plane (ACP) October 2017
o No need for path optimisation: RPL does not necessarily compute
the optimal path between any two nodes. However, the ACP does not
require this today, since it carries mainly non-delay-sensitive
feedback loops. It is possible that different optimisation
schemes become necessary in the future, but RPL can be expanded
(see point "Extensibility" above).
10.6. Extending ACP channel negotiation (via GRASP)
The mechanism described in the normative part of this document to
support multiple different ACP secure channel protocols without a
single network wide MTI protocol is important to allow extending
secure ACP channel protocols beyond what is specified in this
document, but it will run into problem if it would be used for
multiple protocols:
The need to potentially have multiple of these security associations
even temporarily run in parallel to determine which of them works
best does not support the most lightweight implementation options.
The simple policy of letting one side (Alice) decide what is best may
not lead to the mutual best result.
The two limitations can easier be solved if the solution was more
modular and as few as possible initial secure channel negotiation
protocols would be used, and these protocols would then take on the
responsibility to support more flexible objectives to negotiate the
mutually preferred ACP security channel protocol.
IKEv2 is the IETF standard protocol to negotiate network security
associations. It is meant to be extensible, but it is unclear
whether it would be feasible to extend IKEv2 to support possible
future requirements for ACP secure channel negotiation:
Consider the simple case where the use of native IPsec vs. IPsec via
GRE is to be negotiated and the objective is the maximum throughput.
Both sides would indicate some agreed upon performance metric and the
preferred encapsulation is the one with the higher performance of the
slower side. IKEv2 does not support negotiation with this objective.
Consider dTLS and some form of 802.1AE ([MACSEC]) are to be added as
negotiation options - and the performance objective should work
across all IPsec, dDTLS and 802.1AE options. In the case of MacSEC,
the negotiation would also need to determine a key for the peering.
It is unclear if it would be even appropriate to consider extending
the scope of negotiation in IKEv2 to those cases. Even if feasible
to define, it is unclear if implementations of IKEv2 would be eager
to adopt those type of extension given the long cycles of security
Behringer, et al. Expires April 15, 2018 [Page 80]
Internet-Draft An Autonomic Control Plane (ACP) October 2017
testing that necessarily goes along with core security protocols such
as IKEv2 implementations.
A more modular alternative to extending IKEv2 could be to layer a
modular negotiation mechanism on top of the multitude of existing or
possible future secure channel protocols. For this, GRASP over TLS
could be considered as a first ACP secure channel negotiation
protocol. The following are initial considerations for such an
approach. A full specification is subject to a separate document:
To explicitly allow negotiation of the ACP channel protocol, GRASP
over a TLS connection using the GRASP_LISTEN_PORT and the nodes and
peers link-local IPv6 address is used. When Alice and Bob support
GRASP negotiation, they do prefer it over any other non-explicitly
negotiated security association protocol and should wait trying any
non-negotiated ACP channel protocol until after it is clear that
GRASP/TLS will not work to the peer.
When Alice and Bob successfully establish the GRASP/TSL session, they
will negotiate the channel mechanism to use using objectives such as
performance and perceived quality of the security. After agreeing on
a channel mechanism, Alice and Bob start the selected Channel
protocol. Once the secure channel protocol is successfully running,
the GRASP/TLS connection can be kept alive or timed out as long as
the selected channel protocol has a secure association between Alice
and Bob. When it terminates, it needs to be re-negotiated via GRASP/
TLS.
Notes:
o Negotiation of a channel type may require IANA assignments of code
points.
o TLS is subject to reset attacks, which IKEv2 is not. Normally,
ACP connections (as specified in this document) will be over link-
local addresses so the attack surface for this one issue in TCP
should be reduced (note that this may not be true when ACP is
tunneled as described in Section 8.2.2.
o GRASP packets received inside a TLS connection established for
GRASP/TLS ACP negotiation are assigned to a separate GRASP domain
unique to that TLS connection.
10.7. CAs, domains and routing subdomains
There is a wide range of setting up different ACP solution by
appropriately using CAs and the domain and rsub elements in the
domain information field of the domain certificate. We summarize
Behringer, et al. Expires April 15, 2018 [Page 81]
Internet-Draft An Autonomic Control Plane (ACP) October 2017
these options here as they have been explained in different parts of
the document in before and discuss possible and desirable extensions:
An ACP domain is the set of all ACP nodes using certificates from the
same CA using the same domain field. GRASP inside the ACP is run
across all transitively connected ACP nodes in a domain.
The rsub element in the domain information field primarily allows to
use addresses from different ULA prefixes. One use case is to create
multiple networks that initially may be separated, but where it
should be possible to connect them without further extensions to ACP
when necessary.
Another use case for routing subdomains is as the starting point for
structuring routing inside an ACP. For example, different routing
subdomains could run different routing protocols or different
instances of RPL and auto-aggregation / distribution of routes could
be done across inter routing subdomain ACP channels based on
negotiation (e.g.: via GRASP). This is subject for further work.
RPL scales very well. It is not necessary to use multiple routing
subdomains to scale ACP domains in a way it would be possible if
other routing protocols where used. They exist only as options for
the above mentioned reasons.
If different ACP domains are to be created that should not allow to
connect to each other by default, these ACP domains simply need to
have different domain elements in the domain information field.
These domain elements can be arbitrary, including subdomains of one
another: Domains "example.com" and "research.example.com" are
separate domains if both are domain elements in the domain
information element of certificates.
It is not necessary to have a separate CA for different ACP domains:
an operator can use a single CA to sign certificates for multiple ACP
domains that are not allowed to connect to each other because the
checks for ACP adjacencies includes comparison of the domain part.
If multiple independent networks choose the same domain name but had
their own CA, these would not form a single ACP domain because of CA
mismatch. Therefore there is no problem in choosing domain names
that are potentially also used by others. Nevertheless it is highly
recommended to use domain names that one can have high probability to
be unique. It is recommended to use domain names that start with a
DNS domain names owned by the assigning organization and unique
within it. For example "acp.example.com" if you own "example.com".
Behringer, et al. Expires April 15, 2018 [Page 82]
Internet-Draft An Autonomic Control Plane (ACP) October 2017
Future extensions, primarily through intent can create more flexible
options how to build ACP domains.
Intent could modify the ACP connection check to permit connections
between different domains.
If different domains use the same CA one would change the ACP setup
to permit for the ACP to be established between the two ACP nodes,
but no routing nor ACP GRASP to be built across this adjacency. The
main difference over routing subdomains is to not permit for the ACP
GRASP instance to be built across the adjacency. Instead, one would
only build a point to point GRASP instance between those peers to
negotiate what type of exchanges are desired across that connection.
This would include routing negotiation, how much GRASP information to
transit and what data-plane forwarding should be done. This approach
could also allow for Intent to only be injected into the network from
one side and propagate via this GRASP connection.
If different domains have different CAs, they should start to trust
each other by intent injected into both domains that would add the
other domains CA as a trust point during the ACP connection setup -
and then following up with the previous point of inter-domain
connections across domains with the same CA (e.g.: GRASP
negotiation).
10.8. Adopting ACP concepts for other environments
The ACP as specified in this document is very explicit about the
choice of options to allow interoperable implementations. The
choices made may not be the best for all environments, but the
concepts used by the ACP can be used to build derived solutions:
The ACP specifies the use of ULA and deriving its prefix from the
domain name so that no address allocation is required to deploy the
ACP. The ACP will equally work not using ULA but any other /50 IPv6
prefix. This prefix could simply be a configuration of the
registrars when using BRSKI to enroll the domain certificates -
instead of the registrar deriving the /50 ULA prefix from the AN
domain name.
Some solutions may already have an auto-addressing scheme, for
example derived from existing unique device identifiers (e.g.: MAC
addresses). In those cases it may not be desirable to assign
addresses to devices via the ACP address information field in the way
described in this document. The certificate may simply serve to
identify the ACP domain, and the address field could be empty/unused.
The only fix required in the remaining way the ACP operate is to
define another element in the domain certificate for the two peers to
Behringer, et al. Expires April 15, 2018 [Page 83]
Internet-Draft An Autonomic Control Plane (ACP) October 2017
decide who is Alice and who is Bob during secure channel building.
Note though that future work may leverage the acp address to
authenticate "ownership" of the address by the device. If the
address used by a device is derived from some pre-existing permanent
local ID (such as MAC address), then it would be useful to store that
address in the certificate using the format of the access address
information field or in a similar way.
The ACP is defined as a separate VRF because it intends to support
well managed networks with a wide variety of configurations.
Therefore, reliable, configuration-indestructible connectivity cannot
be achieved from the data-plane itself. In solutions where all
transit connectivity impacting functions are fully automated
(including security), indestructible and resilient, it would be
possible to eliminate the need for the ACP to be a separate VRF.
Consider the most simple example system in which there is no separate
data-plane, but the ACP is the data-plane. Add BRSKI, and it becomes
a fully autonomic network - except that it does not support automatic
addressing for user equipment. This gap can then be closed for
example by adding a solution derived from
[I-D.ietf-anima-prefix-management].
The routing protocol chosen by the ACP design (RPL) does explicitly
not optimize for shortest paths and fastest convergence. Variations
of the ACP may want to use a different routing protocol.
Variations such as what routing protocol to use, or whether to
instantiate an ACP in a VRF or (as suggested above) as the actual
data-plane, can be automatically chosen in implementations built to
support multiple options by deriving them from future parameters in
the certificate. Parameters in certificates should be limited to
those that would not need to be changed more often than certificates
would need to be updated anyhow; Or by ensuring that these parameters
can be provisioned before the variation of an ACP is activated in a
node. Using BRSKI, this could be done for example as additional
follow-up signaling directly after the certificate enrolment, still
leveraging the BRSKI TLS connection and therefore not introducing any
additional connectivity requirements.
Last but not least, secure channel protocols including their
encapsulation are easily added to ACP solutions. Secure channels may
even be replaced by simple neighbor authentication to create
simplified ACP variations for environments where no real security is
required but just protection against non-malicious misconfiguration.
Or for environments where all traffic is known or forced to be end-
to-end protected and other means for infrastructure protection are
used. Any future network OAM should always use end-to-end security
Behringer, et al. Expires April 15, 2018 [Page 84]
Internet-Draft An Autonomic Control Plane (ACP) October 2017
anyhow and can leverage the domain certificates and is therefore not
dependent on security to be provided for by ACP secure channels.
11. Security Considerations
An ACP is self-protecting and there is no need to apply configuration
to make it secure. Its security therefore does not depend on
configuration.
However, the security of the ACP depends on a number of other
factors:
o The usage of domain certificates depends on a valid supporting PKI
infrastructure. If the chain of trust of this PKI infrastructure
is compromised, the security of the ACP is also compromised. This
is typically under the control of the network administrator.
o Security can be compromised by implementation errors (bugs), as in
all products.
There is no prevention of source-address spoofing inside the ACP.
This implies that if an attacker gains access to the ACP, it can
spoof all addresses inside the ACP and fake messages from any other
node.
Fundamentally, security depends on correct operation, implementation
and architecture. Autonomic approaches such as the ACP largely
eliminate the dependency on correct operation; implementation and
architectural mistakes are still possible, as in all networking
technologies.
Many details of ACP are designed with security in mind and discussed
elsewhere in the document:
IPv6 addresses used by nodes in the ACP are covered as part of the
nodes domain certificate as described in Section 6.1.1. This allows
even verification of ownership of a peers IPv6 address when using a
connection authenticated with the domain certificate.
The ACP acts as a security (and transport) substrate for GRASP inside
the ACP such that GRASP is not only protected by attacks from the
outside, but also by attacks from compromised inside attackers - by
relying not only on hop-by-hop security of ACP secure channels, but
adding end-to-end security for those GRASP messages. See
Section 6.8.2.
ACP provides for secure, resilient zero-touch discovery of EST
servers for certificate renewal. See Section 6.1.3.
Behringer, et al. Expires April 15, 2018 [Page 85]
Internet-Draft An Autonomic Control Plane (ACP) October 2017
ACP provides extensible, auto-configuring hop-by-hop protection of
the ACP infrastructure via the negotiation of hop-by-hop secure
channel protocols. See Section 6.5 and Section 10.6.
The ACP is designed to minimize attacks from the outside by
minimizing its dependency against any non-ACP operations on a node.
The only dependency in the specification in this document is the need
to share link-local addresses for the ACP secure channel
encapsulation with the data-plane. See Section 6.12.2.
In combination with BRSKI, ACP enables a resilient, fully zero-touch
network solution for short-lived certificates that can be renewed or
re-enrolled even after unintentional expiry (e.g.: because of
interrupted connectivity). See Section 10.1.
12. IANA Considerations
This document defines the "Autonomic Control Plane".
The IANA is requested to register the value "AN_ACP" (without quotes)
to the GRASP Objectives Names Table in the GRASP Parameter Registry.
The specification for this value is this document, Section 6.3.
The IANA is requested to register the value "SRV.est" (without
quotes) to the GRASP Objectives Names Table in the GRASP Parameter
Registry. The specification for this value is this document,
Section 6.1.3.
Note that the objective format "SRV.<service-name>" is intended to be
used for any <service-name> that is an [RFC6335] registered service
name. This is a proposed update to the GRASP registry subject to
future work and only mentioned here for informational purposed to
explain the unique format of the objective name.
The IANA is requested to create an ACP Parameter Registry with
currently one registry table - the "ACP Address Type" table.
The IANA is requested to create an ACP Parameter Registry with
currently one registry table - the "ACP Address Type" table.
"ACP Address Type" Table. The value in this table are numeric values
0...3 paired with a name (string). Future values MUST be assigned
using the Standards Action policy defined by [RFC8126]. The
following initial values are assigned by this document:
0: ACP Zone Addressing Sub-Scheme (ACP RFC Figure 4) / ACP Manual
Addressing Sub-Scheme (ACP RFC Section 6.10.4)
1: ACP Vlong Addressing Sub-Scheme (ACP RFC Section 6.10.5)
Behringer, et al. Expires April 15, 2018 [Page 86]
Internet-Draft An Autonomic Control Plane (ACP) October 2017
13. Acknowledgements
This work originated from an Autonomic Networking project at Cisco
Systems, which started in early 2010. Many people contributed to
this project and the idea of the Autonomic Control Plane, amongst
which (in alphabetical order): Ignas Bagdonas, Parag Bhide, Balaji
BL, Alex Clemm, Yves Hertoghs, Bruno Klauser, Max Pritikin, Michael
Richardson, Ravi Kumar Vadapalli.
Special thanks to Brian Carpenter and Sheng Jiang for their thorough
reviews and to Pascal Thubert and Michael Richardson to provide the
details for the recommendations of the use of RPL in the ACP
Further input and suggestions were received from: Rene Struik, Brian
Carpenter, Benoit Claise.
14. Change log [RFC Editor: Please remove]
14.1. Initial version
First version of this document: draft-behringer-autonomic-control-
plane
14.2. draft-behringer-anima-autonomic-control-plane-00
Initial version of the anima document; only minor edits.
14.3. draft-behringer-anima-autonomic-control-plane-01
o Clarified that the ACP should be based on, and support only IPv6.
o Clarified in intro that ACP is for both, between devices, as well
as for access from a central entity, such as an NMS.
o Added a section on how to connect an NMS system.
o Clarified the hop-by-hop crypto nature of the ACP.
o Added several references to GDNP as a candidate protocol.
o Added a discussion on network split and merge. Although, this
should probably go into the certificate management story longer
term.
Behringer, et al. Expires April 15, 2018 [Page 87]
Internet-Draft An Autonomic Control Plane (ACP) October 2017
14.4. draft-behringer-anima-autonomic-control-plane-02
Addresses (numerous) comments from Brian Carpenter. See mailing list
for details. The most important changes are:
o Introduced a new section "overview", to ease the understanding of
the approach.
o Merged the previous "problem statement" and "use case" sections
into a mostly re-written "use cases" section, since they were
overlapping.
o Clarified the relationship with draft-ietf-anima-stable-
connectivity
14.5. draft-behringer-anima-autonomic-control-plane-03
o Took out requirement for IPv6 --> that's in the reference doc.
o Added requirement section.
o Changed focus: more focus on autonomic functions, not only virtual
out of band. This goes a bit throughout the document, starting
with a changed abstract and intro.
14.6. draft-ietf-anima-autonomic-control-plane-00
No changes; re-submitted as WG document.
14.7. draft-ietf-anima-autonomic-control-plane-01
o Added some paragraphs in addressing section on "why IPv6 only", to
reflect the discussion on the list.
o Moved the data-plane ACP out of the main document, into an
appendix. The focus is now the virtually separated ACP, since it
has significant advantages, and isn't much harder to do.
o Changed the self-creation algorithm: Part of the initial steps go
into the reference document. This document now assumes an
adjacency table, and domain certificate. How those get onto the
device is outside scope for this document.
o Created a new section 6 "workarounds for non-autonomic nodes", and
put the previous controller section (5.9) into this new section.
Now, section 5 is "autonomic only", and section 6 explains what to
do with non-autonomic stuff. Much cleaner now.
Behringer, et al. Expires April 15, 2018 [Page 88]
Internet-Draft An Autonomic Control Plane (ACP) October 2017
o Added an appendix explaining the choice of RPL as a routing
protocol.
o Formalised the creation process a bit more. Now, we create a
"candidate peer list" from the adjacency table, and form the ACP
with those candidates. Also it explains now better that policy
(Intent) can influence the peer selection. (section 4 and 5)
o Introduce a section for the capability negotiation protocol
(section 7). This needs to be worked out in more detail. This
will likely be based on GRASP.
o Introduce a new parameter: ACP tunnel type. And defines it in the
IANA considerations section. Suggest GRE protected with IPSec
transport mode as the default tunnel type.
o Updated links, lots of small edits.
14.8. draft-ietf-anima-autonomic-control-plane-02
o Added explicitly text for the ACP channel negotiation.
o Merged draft-behringer-anima-autonomic-addressing-02 into this
document, as suggested by WG chairs.
14.9. draft-ietf-anima-autonomic-control-plane-03
o Changed Neighbor discovery protocol from GRASP to mDNS. Bootstrap
protocol team decided to go with mDNS to discover bootstrap proxy,
and ACP should be consistent with this. Reasons to go with mDNS
in bootstrap were a) Bootstrap should be reuseable also outside of
full anima solutions and introduce as few as possible new
elements. mDNS was considered well-known and very-likely even pre-
existing in low-end devices (IoT). b) Using GRASP both for the
insecure neighbor discovery and secure ACP operatations raises the
risk of introducing security issues through implementation issues/
non-isolation between those two instances of GRASP.
o Shortened the section on GRASP instances, because with mDNS being
used for discovery, there is no insecure GRASP session any longer,
simplifying the GRASP considerations.
o Added certificate requirements for ANIMA in section 5.1.1,
specifically how the ANIMA information is encoded in
subjectAltName.
o Deleted the appendix on "ACP without separation", as originally
planned, and the paragraph in the main text referring to it.
Behringer, et al. Expires April 15, 2018 [Page 89]
Internet-Draft An Autonomic Control Plane (ACP) October 2017
o Deleted one sub-addressing scheme, focusing on a single scheme
now.
o Included information on how ANIMA information must be encoded in
the domain certificate in section "preconditions".
o Editorial changes, updated draft references, etc.
14.10. draft-ietf-anima-autonomic-control-plane-04
Changed discovery of ACP neighbor back from mDNS to GRASP after
revisiting the L2 problem. Described problem in discovery section
itself to justify. Added text to explain how ACP discovery relates
to BRSKY (bootstrap) discovery and pointed to Michael Richardsons
draft detailing it. Removed appendix section that contained the
original explanations why GRASP would be useful (current text is
meant to be better).
14.11. draft-ietf-anima-autonomic-control-plane-05
o Section 5.3 (candidate ACP neighbor selection): Add that Intent
can override only AFTER an initial default ACP establishment.
o Section 6.10.1 (addressing): State that addresses in the ACP are
permanent, and do not support temporary addresses as defined in
RFC4941.
o Modified Section 6.3 to point to the GRASP objective defined in
draft-carpenter-anima-ani-objectives. (and added that reference)
o Section 6.10.2: changed from MD5 for calculating the first 40 bits
to SHA256; reason is MD5 should not be used any more.
o Added address sub-scheme to the IANA section.
o Made the routing section more prescriptive.
o Clarified in Section 8.1.1 the ACP Connect port, and defined that
term "ACP Connect".
o Section 8.2: Added some thoughts (from mcr) on how traversing a L3
cloud could be automated.
o Added a CRL check in Section 6.7.
o Added a note on the possibility of source-address spoofing into
the security considerations section.
Behringer, et al. Expires April 15, 2018 [Page 90]
Internet-Draft An Autonomic Control Plane (ACP) October 2017
o Other editoral changes, including those proposed by Michael
Richardson on 30 Nov 2016 (see ANIMA list).
14.12. draft-ietf-anima-autonomic-control-plane-06
o Added proposed RPL profile.
o detailed dTLS profile - dTLS with any additional negotiation/
signaling channel.
o Fixed up text for ACP/GRE encap. Removed text claiming its
incompatible with non-GRE IPsec and detailled it.
o Added text to suggest admin down interfaces should still run ACP.
14.13. draft-ietf-anima-autonomic-control-plane-07
o Changed author association.
o Improved ACP connect setion (after confusion about term came up in
the stable connectivity draft review). Added picture, defined
complete terminology.
o Moved ACP channel negotiation from normative section to appendix
because it can in the timeline of this document not be fully
specified to be implementable. Aka: work for future document.
That work would also need to include analysing IKEv2 and describin
the difference of a proposed GRASP/TLS solution to it.
o Removed IANA request to allocate registry for GRASP/TLS. This
would come with future draft (see above).
o Gave the name "ACP information field" to the field in the
certificate carrying the ACP address and domain name.
o Changed the rules for mutual authentication of certificates to
rely on the domain in the ACP information field of the certificate
instead of the OU in the certificate. Also renewed the text
pointing out that the ACP information field in the certificate is
meant to be in a form that it does not disturb other uses of the
certificate. As long as the ACP expected to rely on a common OU
across all certificates in a domain, this was not really true:
Other uses of the certificates might require different OUs for
different areas/type of devices. With the rules in this draft
version, the ACP authentication does not rely on any other fields
in the certificate.
Behringer, et al. Expires April 15, 2018 [Page 91]
Internet-Draft An Autonomic Control Plane (ACP) October 2017
o Added an extension field to the ACP information field so that in
the future additional fields like a subdomain could be inserted.
An example using such a subdomain field was added to the pre-
existing text suggesting sub-domains. This approach is necessary
so that there can be a single (main) domain in the ACP information
field, because that is used for mutual authentication of the
certificate. Also clarified that only the register(s) SHOULD/MUST
use that the ACP address was generated from the domain name - so
that we can easier extend change this in extensions.
o Took the text for the GRASP discovery of ACP neighbors from Brians
grasp-ani-objectives draft. Alas, that draft was behind the
latest GRASP draft, so i had to overhaul. The mayor change is to
describe in the ACP draft the whole format of the M_FLOOD message
(and not only the actual objective). This should make it a lot
easier to read (without having to go back and forth to the GRASP
RFC/draft). It was also necessary because the locator in the
M_FLOOD messages has an important role and its not coded inside
the objective. The specification of how to format the M_FLOOD
message shuold now be complete, the text may be some duplicate
with the DULL specificateion in GRASP, but no contradiction.
o One of the main outcomes of reworking the GRASP section was the
notion that GRASP announces both the candidate peers IPv6 link
local address but also the support ACP security protocol including
the port it is running on. In the past we shied away from using
this information because it is not secured, but i think the
additional attack vectors possible by using this information are
negligible: If an attacker on an L2 subnet can fake another
devices GRASP message then it can already provide a similar amount
of attack by purely faking the link-local address.
o Removed the section on discovery and BRSKI. This can be revived
in the BRSKI document, but it seems mood given how we did remove
mDNS from the latest BRSKI document (aka: this section discussed
discrepancies between GRASP and mDNS discovery which should not
exist anymore with latest BRSKI.
o Tried to resolve the EDNOTE about CRL vs. OCSP by pointing out we
do not specify which one is to be used but that the ACP should be
used to reach the URL included in the certificate to get to the
CRL storage or OCSP server.
o Changed ACP via IPsec to ACP via IKEv2 and restructured the
sections to make IPsec native and IPsec via GRE subsections.
o No need for any assigned dTLS port if ACP is run across dTLS
because it is signaled via GRASP.
Behringer, et al. Expires April 15, 2018 [Page 92]
Internet-Draft An Autonomic Control Plane (ACP) October 2017
14.14. draft-ietf-anima-autonomic-control-plane-08
Modified mentioning of BRSKI to make it consistent with current
(07/2017) target for BRSKI: MASA and IDevID are mandatory. Devices
with only insecure UDI would need a security reduced variant of
BRSKI. Also added mentioning of Netconf Zero-Touch. Made BRSKI non-
normative for ACP because wrt. ACP it is just one option how the
domain certificate can be provisioned. Instead, BRSKI is mandatory
when a device implements ANI which is ACP+BRSKI.
Enhanced text for ACP across tunnels to decribe two options: one
across configured tunnels (GRE, IPinIP etc) a more efficient one via
directed DULL.
Moved decription of BRSKI to appendex to emphasize that BRSKI is not
a (normative) dependency of GRASP, enhanced text to indicate other
options how Domain Certificates can be provisioned.
Added terminology section.
Separated references into normative and non-normative.
Enhanced section about ACP via "tunnels". Defined an option to run
ACP secure channel without an outer tunnel, discussed PMTU, benefits
of tunneling, potential of using this with BRSKI, made ACP via GREP a
SHOULD requirement.
Moved appendix sections up before IANA section because there where
concerns about appendices to be to far on the bottom to be read.
Added (Informative) / (Normative) to section titles to clarify which
sections are informative and which are normative
Moved explanation of ACP with L2 from precondition to separate
section before workarounds, made it instructive enough to explain how
to implement ACP on L2 ports for L3/L2 switches and made this part of
normative requirement (L2/L3 switches SHOULD support this).
Rewrote section "GRASP in the ACP" to define GRASP in ACP as
mandatory (and why), and define the ACP as security and transport
substrate to GRASP in ACP. And how it works.
Enhanced "self-protection" properties section: protect legacy
management protocols. Security in ACP is for protection from outside
and those legacy protocols. Otherwise need end-to-end encryption
also inside ACP, e.g.: with domain certificate.
Enhanced initial domain certificate section to include requirements
for maintenance (renewal/revocation) of certificates. Added
Behringer, et al. Expires April 15, 2018 [Page 93]
Internet-Draft An Autonomic Control Plane (ACP) October 2017
explanation to BRSKI informative section how to handle very short
lived certificates (renewal via BRSKI with expired cert).
Modified the encoding of the ACP address to better fit RFC822 simple
local-parts (":" as required by RFC5952 are not permitted in simple
dot-atoms according to RFC5322. Removed reference to RFC5952 as its
now not needed anymore.
Introduced a sub-domain field in the ACP information in the
certificate to allow defining such subdomains with depending on
future Intent definitions. It also makes it clear what the "main
domain" is. Scheme is called "routing subdomain" to have a unique
name.
Added V8 (now called Vlong) addressing sub-scheme according to
suggestion from mcr in his mail from 30 Nov 2016
(https://mailarchive.ietf.org/arch/msg/anima/
nZpEphrTqDCBdzsKMpaIn2gsIzI). Also modified the explanation of the
single V bit in the first sub-scheme now renamed to Zone sub-scheme
to distinguish it.
14.15. draft-ietf-anima-autonomic-control-plane-09
Added reference to RFC4191 and explained how it should be used on ACP
edge routers to allow autoconfiguration of routing by NMS hosts.
This came after review of stable connectivity draft where ACP connect
is being referred to.
V8 addressing Sub-Scheme was modified to allow not only /8 device-
local address space but also /16. This was in response to the
possible need to have maybe as much as 2^12 local addresses for
future encaps in BRSKI like IPinIP. It also would allow fully
autonomic address assignment for ACP connect interfaces from this
local address space (on an ACP edge device), subject to approval of
the implied update to rfc4291/rfc4193 (IID length). Changed name to
Vlong addressing sub-scheme.
Added text in response to Brian Carpenters review of draft-ietf-
anima-stable-connectivity-04.
o The stable connectivity draft was vaguely describing ACP connect
behavior that is better standardized in this ACP draft.
o Added new ACP "Manual" addressing sub-scheme with /64 subnets for
use with ACP connect interfaces. Being covered by the ACP ULA
prefix, these subnets do not require additional routing entries
for NMS hosts. They also are fully 64-bit IID length compliant
and therefore not subject to 4191bis considerations. And they
Behringer, et al. Expires April 15, 2018 [Page 94]
Internet-Draft An Autonomic Control Plane (ACP) October 2017
avoid that operators manually assign prefixes from the ACP ULA
prefixes that might later be assigned autonomiously.
o ACP connect auto-configuration: Defined that ACP edge devices, NMS
hosts should use RFC4191 to automatically learn ACP prefixes.
This is especially necessary when the ACP uses multiple ULA
prefixes (via e.g.: the rsub domain certificate option), or if ACP
connect subinterfaces use manually configured prefixes NOT covered
by the ACP ULA prefixes.
o Explained how rfc6724 is (only) sufficient when the NMS host has a
separate ACP connect and data-plane interface. But not when there
is a single interface.
o Added a separate subsection to talk about "software" instead of
"NMS hosts" connecting to the ACP via the "ACP connect" method.
The reason is to point out that the "ACP connect" method is not
only a workaround (for NMS hosts), but an actual desirable long
term architectural component to modularily build software (e.g.:
ASA or OAM for VNF) into ACP devices.
o Added a section to define how to run ACP connect across the same
interface as the data-plane. This turns out to be quite
challenging because we only want to rely on existing standards for
the network stack in the NMS host/software and only define what
features the ACP edge device needs.
o Added section about use of GRASP over ACP connect.
o Added text to indicate packet processing/filtering for security:
filter incorrect packets arriving on ACP connect interfaces,
diagnose on RPL root packets to incorrect destination address (not
in ACP connect section, but because of it).
o Reaffirm security goal of ACP: Do not permit non-ACP routers into
ACP routing domain.
Made this ACP document be an update to RFC4291 and RFC4193. At the
core, some of the ACP addressing sub-schemes do effectively not use
64-bit IIDs as required by RFC4191 and debated in rfc4191bis. During
6man in prague, it was suggested that all documents that do not do
this should be classified as such updates. Add a rather long section
that summarizes the relevant parts of ACP addressing and usage and.
Aka: This section is meant to be the primary review section for
readers interested in these changes (e.g.: 6man WG.).
Added changes from Michael Richardsons review https://github.com/
anima-wg/autonomic-control-plane/pull/3/commits, textual and:
Behringer, et al. Expires April 15, 2018 [Page 95]
Internet-Draft An Autonomic Control Plane (ACP) October 2017
o ACP discovery inside ACP is bad *doh*!.
o Better CA trust and revocation sentences.
o More details about RPL behavior in ACP.
o black hole route to avoid loops in RPL.
Added requirement to terminate ACP channels upon cert expiry/
revocation.
Added fixes from 08-mcr-review-reply.txt (on github):
o AN Domain Names are FQDNs.
o Fixed bit length of schemes, numerical writing of bits (00b/01b).
o Lets use US american english.
14.16. draft-ietf-anima-autonomic-control-plane-10
Used the term routing subdomain more consistently where previously
only subdomain was used. Clarified use of routing subdomain in
creation of ULA "global ID" addressing prefix.
6.7.1.* Changed native IPsec encapsulation to tunnel mode
(necessary), explaned why. Added notion that ESP is used, added
explanations why tunnel/transport mode in native vs. GRE cases.
6.10.3/6.10.5 Added term "ACP address range/set" to be able to better
explain how the address in the ACP certificate is actually the base
address (lowest address) of a range/set that is available to the
device.
6.10.4 Added note that manual address sub-scheme addresses must not
be used within domain certificates (only for explicit configuration).
6.12.5 Refined explanation of how ACP virtual interfaces work (p2p
and multipoint). Did seek for pre-existing RFCs that explain how to
built a multi-access interface on top of a full mesh of p2p
connections (6man WG, anima WG mailing lists), but could not find any
prior work that had a succinct explanation. So wrote up an
explanation here. Added hopefully all necessary and sufficient
details how to map ACP unicast packets to ACP secure channel, how to
deal with ND packet details. Added verbage for ACP not to assign the
virtual interface link-local address from the underlying interface.
Addd note that GRAP link-local messages are treated specially but
logically the same. Added paragraph about NBMA interfaces.
Behringer, et al. Expires April 15, 2018 [Page 96]
Internet-Draft An Autonomic Control Plane (ACP) October 2017
remaining changes from Brian Carpenters review. See Github file
draft-ietf-anima-autonomic-control-plane/08-carpenter-review-reply.tx
for more detailst:
Added multiple new RFC references for terms/technologies used.
Fixed verbage in several places.
2. (terminology) Added 802.1AR as reference.
2. Fixed up definition of ULA.
6.1.1 Changed definition of ACP information in cert into ABNF format.
Added warning about maximum size of ACP address field due to domain-
name limitations.
6.2 Mentioned API requirement between ACP and clients leveraging
adjacency table.
6.3 Fixed TTL in GRASP example: msec, not hop-count!.
6.8.2 MAYOR: expanded security/transport substrate text:
Introduced term ACP GRASP virtual interface to explain how GRASP
link-local multicast messages are encapsulated and replicated to
neighbors. Explain how ACP knows when to use TLS vs. TCP (TCP only
for link-local address (sockets). Introduced "ladder" picture to
visualize stack.
6.8.2.1 Expanded discussion/explanation of security model. TLS for
GRASP unicsast connections across ACP is double encryption (plus
underlying ACP secure channel), but highly necessary to avoid very
simple man-in-the-middle attacks by compromised ACP members on-path.
Ultimately, this is done to ensure that any apps using GRASP can get
full end-to-end secrecy for information sent across GRASP. But for
publically known ASA services, even this will not provide 100%
security (this is discussed). Also why double encryption is the
better/easier solution than trying to optimize this.
6.10.1 Added discussion about pseudo-random addressing, scanning-
attaacks (not an issue for ACP).
6.12.2 New performance requirements section added.
6.10.1 Added notion to first experiment with existing addressing
schemes before defining new ones - we should be flexible enough.
Behringer, et al. Expires April 15, 2018 [Page 97]
Internet-Draft An Autonomic Control Plane (ACP) October 2017
6.3/7.2 clarified the interactions between MLD and DULL GRASP and
specified what needs to be done (e.g.: in 2 switches doing ACP per L2
port).
12. Added explanations and cross-references to various security
aspects of ACP discussed elsewhere in the document.
13. Added IANA requirements.
Added RFC2119 boilerplate.
14.17. draft-ietf-anima-autonomic-control-plane-11
Same text as -10 Unfortunately when uploading -10 .xml/.txt to
datatracker, a wrong version of .txt got uploaded, only the .xml was
correct. This impacts the -10 html version on datatra cker and the
PDF versions as well. Because rfcdiff also compares the .txt
version, this -11 version was crea ted so that one can compare
changes from -09 and changes to the next version (-12).
14.18. draft-ietf-anima-autonomic-control-plane-12
Sheng Jiangs extensive review. Thanks! See Github file draft-ietf-
anima-autonomic-control-plane/09-sheng-review-reply.txt for more
details. Many of the larger changes listed below where inspired by
the review.
Removed the claim that the document is updating RFC4291,RFC4193 and
the section detailling it. Done on suggestion of Michael Richardson
- just try to describe use of addressing in a way that would not
suggest a need claim update to architecture.
Terminology cleanup:
o Replaced "device" with "node" in text. Kept "device" only when
referring to "physical node". Added definitions for those words.
Includes changes of derived terms, especially in addressing:
"Node-ID" and "Node-Number" in the addressing details.
o Replaced term "autonomic FOOBAR" with "acp FOOBAR" as whereever
appropriate: "autonomic" would imply that the node would need to
support more than the ACP, but that is not correct in most of the
cases. Wanted to make sure that implementers know they only need
to support/implement ACP - unless stated otherwise. Includes
"AN->ACP node", "AN->ACP adjacency table" and so on.
1 Added explanation in the introduction about relationship between
ACP, BRSKI, ANI and Autonomic Networks.
Behringer, et al. Expires April 15, 2018 [Page 98]
Internet-Draft An Autonomic Control Plane (ACP) October 2017
6.1.1 Improved terminology and features of the certificate
information field. Now called domain information field instead of
ACP information field. The acp-address field in the domain
information field is now optional, enabling easier introduction of
various future options.
6.1.2 Moved ACP domainer membership check from section 6.6 to (ACP
secure channels setup) here because it is not only used for ACP
secure channel setup.
6.1.3 Fix text about certificate renewal after discussion with Max
Pritikin/Michael Richardson/Brian Carpenter:
o Version 10 erroneously assumed that the certificate itself could
store a URL for renewal, but that is only possible for CRL URLs.
Text now only refers to "remembered EST server" without implying
that this is stored in the certificate.
o Objective for RFC7030/EST domain certificate renewal was changed
to "SRV.est" See also IANA section for explanation.
o Removed detail of distance based service selection. This can be
better done in future work because it would require a lot more
detail for a good DNS-SD compatible approach.
o Removed detail about trying to create more security by using ACP
address from certificate of peer. After rethinking, this does not
seem to buy additional security.
6.10 Added reference to 6.12.5 in initial use of "loopback interface"
in section 6.10 in result of email discussion michaelR/michaelB.
10.2 Introduced informational section (diagnostics) because of
operational experience - ACP/ANI undeployable without at least
diagnostics like this.
10.3 Introduced informational section (enabling/disabling) ACP.
Important to discuss this for security reasons (e.g.: why to never
never auto-enable ANI on brownfield devices), for implementers and to
answer ongoing questions during WG meetings about how to deal with
shutdown interface.
10.8 Added informational section discussing possible future
variations of the ACP for potential adopters that cannot directly use
the complete solution described in this document unmodified.
Behringer, et al. Expires April 15, 2018 [Page 99]
Internet-Draft An Autonomic Control Plane (ACP) October 2017
15. References
15.1. Normative References
[I-D.ietf-anima-grasp]
Bormann, C., Carpenter, B., and B. Liu, "A Generic
Autonomic Signaling Protocol (GRASP)", draft-ietf-anima-
grasp-15 (work in progress), July 2017.
[RFC1034] Mockapetris, P., "Domain names - concepts and facilities",
STD 13, RFC 1034, DOI 10.17487/RFC1034, November 1987,
<https://www.rfc-editor.org/info/rfc1034>.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997,
<https://www.rfc-editor.org/info/rfc2119>.
[RFC3810] Vida, R., Ed. and L. Costa, Ed., "Multicast Listener
Discovery Version 2 (MLDv2) for IPv6", RFC 3810,
DOI 10.17487/RFC3810, June 2004,
<https://www.rfc-editor.org/info/rfc3810>.
[RFC4191] Draves, R. and D. Thaler, "Default Router Preferences and
More-Specific Routes", RFC 4191, DOI 10.17487/RFC4191,
November 2005, <https://www.rfc-editor.org/info/rfc4191>.
[RFC4193] Hinden, R. and B. Haberman, "Unique Local IPv6 Unicast
Addresses", RFC 4193, DOI 10.17487/RFC4193, October 2005,
<https://www.rfc-editor.org/info/rfc4193>.
[RFC4291] Hinden, R. and S. Deering, "IP Version 6 Addressing
Architecture", RFC 4291, DOI 10.17487/RFC4291, February
2006, <https://www.rfc-editor.org/info/rfc4291>.
[RFC4301] Kent, S. and K. Seo, "Security Architecture for the
Internet Protocol", RFC 4301, DOI 10.17487/RFC4301,
December 2005, <https://www.rfc-editor.org/info/rfc4301>.
[RFC4861] Narten, T., Nordmark, E., Simpson, W., and H. Soliman,
"Neighbor Discovery for IP version 6 (IPv6)", RFC 4861,
DOI 10.17487/RFC4861, September 2007,
<https://www.rfc-editor.org/info/rfc4861>.
[RFC4862] Thomson, S., Narten, T., and T. Jinmei, "IPv6 Stateless
Address Autoconfiguration", RFC 4862,
DOI 10.17487/RFC4862, September 2007,
<https://www.rfc-editor.org/info/rfc4862>.
Behringer, et al. Expires April 15, 2018 [Page 100]
Internet-Draft An Autonomic Control Plane (ACP) October 2017
[RFC5246] Dierks, T. and E. Rescorla, "The Transport Layer Security
(TLS) Protocol Version 1.2", RFC 5246,
DOI 10.17487/RFC5246, August 2008,
<https://www.rfc-editor.org/info/rfc5246>.
[RFC5280] Cooper, D., Santesson, S., Farrell, S., Boeyen, S.,
Housley, R., and W. Polk, "Internet X.509 Public Key
Infrastructure Certificate and Certificate Revocation List
(CRL) Profile", RFC 5280, DOI 10.17487/RFC5280, May 2008,
<https://www.rfc-editor.org/info/rfc5280>.
[RFC5322] Resnick, P., Ed., "Internet Message Format", RFC 5322,
DOI 10.17487/RFC5322, October 2008,
<https://www.rfc-editor.org/info/rfc5322>.
[RFC6347] Rescorla, E. and N. Modadugu, "Datagram Transport Layer
Security Version 1.2", RFC 6347, DOI 10.17487/RFC6347,
January 2012, <https://www.rfc-editor.org/info/rfc6347>.
[RFC6550] Winter, T., Ed., Thubert, P., Ed., Brandt, A., Hui, J.,
Kelsey, R., Levis, P., Pister, K., Struik, R., Vasseur,
JP., and R. Alexander, "RPL: IPv6 Routing Protocol for
Low-Power and Lossy Networks", RFC 6550,
DOI 10.17487/RFC6550, March 2012,
<https://www.rfc-editor.org/info/rfc6550>.
[RFC6552] Thubert, P., Ed., "Objective Function Zero for the Routing
Protocol for Low-Power and Lossy Networks (RPL)",
RFC 6552, DOI 10.17487/RFC6552, March 2012,
<https://www.rfc-editor.org/info/rfc6552>.
[RFC7030] Pritikin, M., Ed., Yee, P., Ed., and D. Harkins, Ed.,
"Enrollment over Secure Transport", RFC 7030,
DOI 10.17487/RFC7030, October 2013,
<https://www.rfc-editor.org/info/rfc7030>.
[RFC7296] Kaufman, C., Hoffman, P., Nir, Y., Eronen, P., and T.
Kivinen, "Internet Key Exchange Protocol Version 2
(IKEv2)", STD 79, RFC 7296, DOI 10.17487/RFC7296, October
2014, <https://www.rfc-editor.org/info/rfc7296>.
[RFC7676] Pignataro, C., Bonica, R., and S. Krishnan, "IPv6 Support
for Generic Routing Encapsulation (GRE)", RFC 7676,
DOI 10.17487/RFC7676, October 2015,
<https://www.rfc-editor.org/info/rfc7676>.
Behringer, et al. Expires April 15, 2018 [Page 101]
Internet-Draft An Autonomic Control Plane (ACP) October 2017
15.2. Informative References
[AR8021] IEEE SA-Standards Board, "IEEE Standard for Local and
metropolitan area networks - Secure Device Identity",
December 2009, <http://standards.ieee.org/findstds/
standard/802.1AR-2009.html>.
[I-D.ietf-anima-bootstrapping-keyinfra]
Pritikin, M., Richardson, M., Behringer, M., Bjarnason,
S., and K. Watsen, "Bootstrapping Remote Secure Key
Infrastructures (BRSKI)", draft-ietf-anima-bootstrapping-
keyinfra-07 (work in progress), July 2017.
[I-D.ietf-anima-prefix-management]
Jiang, S., Du, Z., Carpenter, B., and Q. Sun, "Autonomic
IPv6 Edge Prefix Management in Large-scale Networks",
draft-ietf-anima-prefix-management-05 (work in progress),
August 2017.
[I-D.ietf-anima-reference-model]
Behringer, M., Carpenter, B., Eckert, T., Ciavaglia, L.,
Pierre, P., Liu, B., Nobre, J., and J. Strassner, "A
Reference Model for Autonomic Networking", draft-ietf-
anima-reference-model-04 (work in progress), July 2017.
[I-D.ietf-anima-stable-connectivity]
Eckert, T. and M. Behringer, "Using Autonomic Control
Plane for Stable Connectivity of Network OAM", draft-ietf-
anima-stable-connectivity-06 (work in progress), September
2017.
[I-D.ietf-netconf-zerotouch]
Watsen, K., Abrahamsson, M., and I. Farrer, "Zero Touch
Provisioning for NETCONF or RESTCONF based Management",
draft-ietf-netconf-zerotouch-17 (work in progress),
September 2017.
[I-D.ietf-roll-useofrplinfo]
Robles, I., Richardson, M., and P. Thubert, "When to use
RFC 6553, 6554 and IPv6-in-IPv6", draft-ietf-roll-
useofrplinfo-16 (work in progress), July 2017.
[MACSEC] IEEE SA-Standards Board, "IEEE Standard for Local and
Metropolitan Area Networks: Media Access Control (MAC)
Security", June 2006,
<https://standards.ieee.org/findstds/
standard/802.1AE-2006.html>.
Behringer, et al. Expires April 15, 2018 [Page 102]
Internet-Draft An Autonomic Control Plane (ACP) October 2017
[RFC1112] Deering, S., "Host extensions for IP multicasting", STD 5,
RFC 1112, DOI 10.17487/RFC1112, August 1989,
<https://www.rfc-editor.org/info/rfc1112>.
[RFC1918] Rekhter, Y., Moskowitz, B., Karrenberg, D., de Groot, G.,
and E. Lear, "Address Allocation for Private Internets",
BCP 5, RFC 1918, DOI 10.17487/RFC1918, February 1996,
<https://www.rfc-editor.org/info/rfc1918>.
[RFC2315] Kaliski, B., "PKCS #7: Cryptographic Message Syntax
Version 1.5", RFC 2315, DOI 10.17487/RFC2315, March 1998,
<https://www.rfc-editor.org/info/rfc2315>.
[RFC2821] Klensin, J., Ed., "Simple Mail Transfer Protocol",
RFC 2821, DOI 10.17487/RFC2821, April 2001,
<https://www.rfc-editor.org/info/rfc2821>.
[RFC4541] Christensen, M., Kimball, K., and F. Solensky,
"Considerations for Internet Group Management Protocol
(IGMP) and Multicast Listener Discovery (MLD) Snooping
Switches", RFC 4541, DOI 10.17487/RFC4541, May 2006,
<https://www.rfc-editor.org/info/rfc4541>.
[RFC4604] Holbrook, H., Cain, B., and B. Haberman, "Using Internet
Group Management Protocol Version 3 (IGMPv3) and Multicast
Listener Discovery Protocol Version 2 (MLDv2) for Source-
Specific Multicast", RFC 4604, DOI 10.17487/RFC4604,
August 2006, <https://www.rfc-editor.org/info/rfc4604>.
[RFC4607] Holbrook, H. and B. Cain, "Source-Specific Multicast for
IP", RFC 4607, DOI 10.17487/RFC4607, August 2006,
<https://www.rfc-editor.org/info/rfc4607>.
[RFC4610] Farinacci, D. and Y. Cai, "Anycast-RP Using Protocol
Independent Multicast (PIM)", RFC 4610,
DOI 10.17487/RFC4610, August 2006,
<https://www.rfc-editor.org/info/rfc4610>.
[RFC4941] Narten, T., Draves, R., and S. Krishnan, "Privacy
Extensions for Stateless Address Autoconfiguration in
IPv6", RFC 4941, DOI 10.17487/RFC4941, September 2007,
<https://www.rfc-editor.org/info/rfc4941>.
[RFC5234] Crocker, D., Ed. and P. Overell, "Augmented BNF for Syntax
Specifications: ABNF", STD 68, RFC 5234,
DOI 10.17487/RFC5234, January 2008,
<https://www.rfc-editor.org/info/rfc5234>.
Behringer, et al. Expires April 15, 2018 [Page 103]
Internet-Draft An Autonomic Control Plane (ACP) October 2017
[RFC5321] Klensin, J., "Simple Mail Transfer Protocol", RFC 5321,
DOI 10.17487/RFC5321, October 2008,
<https://www.rfc-editor.org/info/rfc5321>.
[RFC5790] Liu, H., Cao, W., and H. Asaeda, "Lightweight Internet
Group Management Protocol Version 3 (IGMPv3) and Multicast
Listener Discovery Version 2 (MLDv2) Protocols", RFC 5790,
DOI 10.17487/RFC5790, February 2010,
<https://www.rfc-editor.org/info/rfc5790>.
[RFC6241] Enns, R., Ed., Bjorklund, M., Ed., Schoenwaelder, J., Ed.,
and A. Bierman, Ed., "Network Configuration Protocol
(NETCONF)", RFC 6241, DOI 10.17487/RFC6241, June 2011,
<https://www.rfc-editor.org/info/rfc6241>.
[RFC6335] Cotton, M., Eggert, L., Touch, J., Westerlund, M., and S.
Cheshire, "Internet Assigned Numbers Authority (IANA)
Procedures for the Management of the Service Name and
Transport Protocol Port Number Registry", BCP 165,
RFC 6335, DOI 10.17487/RFC6335, August 2011,
<https://www.rfc-editor.org/info/rfc6335>.
[RFC6553] Hui, J. and JP. Vasseur, "The Routing Protocol for Low-
Power and Lossy Networks (RPL) Option for Carrying RPL
Information in Data-Plane Datagrams", RFC 6553,
DOI 10.17487/RFC6553, March 2012,
<https://www.rfc-editor.org/info/rfc6553>.
[RFC6724] Thaler, D., Ed., Draves, R., Matsumoto, A., and T. Chown,
"Default Address Selection for Internet Protocol Version 6
(IPv6)", RFC 6724, DOI 10.17487/RFC6724, September 2012,
<https://www.rfc-editor.org/info/rfc6724>.
[RFC6762] Cheshire, S. and M. Krochmal, "Multicast DNS", RFC 6762,
DOI 10.17487/RFC6762, February 2013,
<https://www.rfc-editor.org/info/rfc6762>.
[RFC6763] Cheshire, S. and M. Krochmal, "DNS-Based Service
Discovery", RFC 6763, DOI 10.17487/RFC6763, February 2013,
<https://www.rfc-editor.org/info/rfc6763>.
[RFC7404] Behringer, M. and E. Vyncke, "Using Only Link-Local
Addressing inside an IPv6 Network", RFC 7404,
DOI 10.17487/RFC7404, November 2014,
<https://www.rfc-editor.org/info/rfc7404>.
Behringer, et al. Expires April 15, 2018 [Page 104]
Internet-Draft An Autonomic Control Plane (ACP) October 2017
[RFC7426] Haleplidis, E., Ed., Pentikousis, K., Ed., Denazis, S.,
Hadi Salim, J., Meyer, D., and O. Koufopavlou, "Software-
Defined Networking (SDN): Layers and Architecture
Terminology", RFC 7426, DOI 10.17487/RFC7426, January
2015, <https://www.rfc-editor.org/info/rfc7426>.
[RFC7575] Behringer, M., Pritikin, M., Bjarnason, S., Clemm, A.,
Carpenter, B., Jiang, S., and L. Ciavaglia, "Autonomic
Networking: Definitions and Design Goals", RFC 7575,
DOI 10.17487/RFC7575, June 2015,
<https://www.rfc-editor.org/info/rfc7575>.
[RFC7576] Jiang, S., Carpenter, B., and M. Behringer, "General Gap
Analysis for Autonomic Networking", RFC 7576,
DOI 10.17487/RFC7576, June 2015,
<https://www.rfc-editor.org/info/rfc7576>.
[RFC7721] Cooper, A., Gont, F., and D. Thaler, "Security and Privacy
Considerations for IPv6 Address Generation Mechanisms",
RFC 7721, DOI 10.17487/RFC7721, March 2016,
<https://www.rfc-editor.org/info/rfc7721>.
[RFC7761] Fenner, B., Handley, M., Holbrook, H., Kouvelas, I.,
Parekh, R., Zhang, Z., and L. Zheng, "Protocol Independent
Multicast - Sparse Mode (PIM-SM): Protocol Specification
(Revised)", STD 83, RFC 7761, DOI 10.17487/RFC7761, March
2016, <https://www.rfc-editor.org/info/rfc7761>.
[RFC8126] Cotton, M., Leiba, B., and T. Narten, "Guidelines for
Writing an IANA Considerations Section in RFCs", BCP 26,
RFC 8126, DOI 10.17487/RFC8126, June 2017,
<https://www.rfc-editor.org/info/rfc8126>.
Authors' Addresses
Michael H. Behringer (editor)
Email: michael.h.behringer@gmail.com
Toerless Eckert (editor)
Futurewei Technologies Inc.
2330 Central Expy
Santa Clara 95050
USA
Email: tte+ietf@cs.fau.de
Behringer, et al. Expires April 15, 2018 [Page 105]
Internet-Draft An Autonomic Control Plane (ACP) October 2017
Steinthor Bjarnason
Arbor Networks
2727 South State Street, Suite 200
Ann Arbor MI 48104
United States
Email: sbjarnason@arbor.net
Behringer, et al. Expires April 15, 2018 [Page 106]