An Autonomic Control Plane (ACP)
draft-ietf-anima-autonomic-control-plane-08
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 RFC 8994.
|
|
|---|---|---|---|
| Authors | Michael H. Behringer , Toerless Eckert , Steinthor Bjarnason | ||
| Last updated | 2017-07-18 | ||
| Replaces | draft-behringer-anima-autonomic-control-plane | ||
| RFC stream | Internet Engineering Task Force (IETF) | ||
| Formats | |||
| Reviews |
SECDIR Telechat review
(of
-16)
by Liang Xia
Has issues
GENART Telechat review
(of
-16)
by Elwyn Davies
Ready w/nits
SECDIR Early review
(of
-13)
by Liang Xia
Has issues
|
||
| Additional resources | Mailing list discussion | ||
| Stream | WG state | WG Document | |
| Document shepherd | Sheng Jiang | ||
| IESG | IESG state | Became RFC 8994 (Proposed Standard) | |
| Consensus boilerplate | Yes | ||
| Telechat date | (None) | ||
| Responsible AD | (None) | ||
| Send notices to | "Sheng Jiang" <jiangsheng@huawei.com> |
draft-ietf-anima-autonomic-control-plane-08
ANIMA WG M. Behringer, Ed.
Internet-Draft
Intended status: Standards Track T. Eckert, Ed.
Expires: January 21, 2018 Huawei
S. Bjarnason
Arbor Networks
July 20, 2017
An Autonomic Control Plane (ACP)
draft-ietf-anima-autonomic-control-plane-08
Abstract
Autonomic functions need a control plane to communicate, which
depends on some addressing and routing. This Autonomic Control Plane
should ideally be self-managing, and as independent as possible of
configuration. This document defines an "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 communications
over a network that is not configured, or mis-configured.
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-
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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 January 21, 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
(http://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents
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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. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 5
3. Use Cases for an Autonomic Control Plane . . . . . . . . . . 8
3.1. An Infrastructure for Autonomic Functions . . . . . . . . 8
3.2. Secure Bootstrap over an Unconfigured Network . . . . . . 8
3.3. Data Plane Independent Permanent Reachability . . . . . . 8
4. Requirements . . . . . . . . . . . . . . . . . . . . . . . . 9
5. Overview . . . . . . . . . . . . . . . . . . . . . . . . . . 10
6. Self-Creation of an Autonomic Control Plane (ACP) (Normative) 11
6.1. Domain Certificate . . . . . . . . . . . . . . . . . . . 12
6.1.1. ACP information . . . . . . . . . . . . . . . . . . . 12
6.1.2. Maintenance . . . . . . . . . . . . . . . . . . . . . 14
6.2. AN Adjacency Table . . . . . . . . . . . . . . . . . . . 16
6.3. Neighbor Discovery with DULL GRASP . . . . . . . . . . . 16
6.4. Candidate ACP Neighbor Selection . . . . . . . . . . . . 19
6.5. Channel Selection . . . . . . . . . . . . . . . . . . . . 19
6.6. Candidate ACP Neighbor certificate verification . . . . . 21
6.7. Security Association protocols . . . . . . . . . . . . . 21
6.7.1. ACP via IKEv2 . . . . . . . . . . . . . . . . . . . . 21
6.7.2. ACP via dTLS . . . . . . . . . . . . . . . . . . . . 22
6.7.3. ACP Secure Channel Requirements . . . . . . . . . . . 23
6.8. GRASP in the ACP . . . . . . . . . . . . . . . . . . . . 23
6.8.1. GRASP as a core service of the ACP . . . . . . . . . 23
6.8.2. ACP as the Security and Transport substrate for GRASP 23
6.9. Context Separation . . . . . . . . . . . . . . . . . . . 24
6.10. Addressing inside the ACP . . . . . . . . . . . . . . . . 25
6.10.1. Fundamental Concepts of Autonomic Addressing . . . . 25
6.10.2. The ACP Addressing Base Scheme . . . . . . . . . . . 26
6.10.3. ACP Zone Addressing Sub-Scheme . . . . . . . . . . . 27
6.10.4. ACP V8 Addressing Sub-Scheme . . . . . . . . . . . . 29
6.10.5. Other ACP Addressing Sub-Schemes . . . . . . . . . . 29
6.11. Routing in the ACP . . . . . . . . . . . . . . . . . . . 30
6.11.1. RPL Profile . . . . . . . . . . . . . . . . . . . . 30
6.12. General ACP Considerations . . . . . . . . . . . . . . . 33
6.12.1. Addressing of Secure Channels in the data plane . . 33
6.12.2. MTU . . . . . . . . . . . . . . . . . . . . . . . . 33
6.12.3. Multiple links between nodes . . . . . . . . . . . . 34
6.12.4. ACP interfaces . . . . . . . . . . . . . . . . . . . 34
7. ACP support on L2 switches/ports (Normative) . . . . . . . . 36
7.1. Why . . . . . . . . . . . . . . . . . . . . . . . . . . . 36
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7.2. How (per L2 port DULL GRASP) . . . . . . . . . . . . . . 37
8. Workarounds for Non-Autonomic Nodes (Normative) . . . . . . . 38
8.1. Non-Autonomic Controller / NMS system (ACP connect) . . . 38
8.2. ACP through Non-Autonomic L3 Clouds (Remote ACP
neighbors) . . . . . . . . . . . . . . . . . . . . . . . 40
8.2.1. Configured Remote ACP neighbor . . . . . . . . . . . 40
8.2.2. Tunneled Remote ACP Neighbor . . . . . . . . . . . . 41
8.2.3. Summary . . . . . . . . . . . . . . . . . . . . . . . 42
9. Benefits (Informative) . . . . . . . . . . . . . . . . . . . 42
9.1. Self-Healing Properties . . . . . . . . . . . . . . . . . 42
9.2. Self-Protection Properties . . . . . . . . . . . . . . . 43
9.2.1. From the outside . . . . . . . . . . . . . . . . . . 43
9.2.2. From the inside . . . . . . . . . . . . . . . . . . . 44
9.3. The Administrator View . . . . . . . . . . . . . . . . . 45
10. Further Considerations (Informative) . . . . . . . . . . . . 45
10.1. Domain Certificate provisioning / enrollment . . . . . . 45
10.2. ACP Neighbor discovery protocol selection . . . . . . . 47
10.2.1. LLDP . . . . . . . . . . . . . . . . . . . . . . . . 47
10.2.2. mDNS and L2 support . . . . . . . . . . . . . . . . 47
10.2.3. Why DULL GRASP . . . . . . . . . . . . . . . . . . . 47
10.3. Choice of routing protocol (RPL) . . . . . . . . . . . . 48
10.4. Extending ACP channel negotiation (via GRASP) . . . . . 49
10.5. CAs, domains and routing subdomains considerations . . . 51
11. Security Considerations . . . . . . . . . . . . . . . . . . . 53
12. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 53
13. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 53
14. Change log [RFC Editor: Please remove] . . . . . . . . . . . 54
14.1. Initial version . . . . . . . . . . . . . . . . . . . . 54
14.2. draft-behringer-anima-autonomic-control-plane-00 . . . . 54
14.3. draft-behringer-anima-autonomic-control-plane-01 . . . . 54
14.4. draft-behringer-anima-autonomic-control-plane-02 . . . . 54
14.5. draft-behringer-anima-autonomic-control-plane-03 . . . . 54
14.6. draft-ietf-anima-autonomic-control-plane-00 . . . . . . 55
14.7. draft-ietf-anima-autonomic-control-plane-01 . . . . . . 55
14.8. draft-ietf-anima-autonomic-control-plane-02 . . . . . . 56
14.9. draft-ietf-anima-autonomic-control-plane-03 . . . . . . 56
14.10. draft-ietf-anima-autonomic-control-plane-04 . . . . . . 56
14.11. draft-ietf-anima-autonomic-control-plane-05 . . . . . . 57
14.12. draft-ietf-anima-autonomic-control-plane-06 . . . . . . 57
14.13. draft-ietf-anima-autonomic-control-plane-07 . . . . . . 58
14.14. draft-ietf-anima-autonomic-control-plane-08 . . . . . . 59
15. References . . . . . . . . . . . . . . . . . . . . . . . . . 61
15.1. Normative References . . . . . . . . . . . . . . . . . . 61
15.2. Informative References . . . . . . . . . . . . . . . . . 62
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 63
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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 a stable and robust infrastructure to
communicate on. This infrastructure should be as robust as possible,
and it should be re-usable by all autonomic functions. [RFC7575]
calls it the "Autonomic Control Plane". This document defines the
Autonomic Control Plane.
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 operationally expensive.
In increasingly automated networks either controllers or distributed
autonomic service agents in the network require a control plane which
is independent of the network they manage, to avoid impacting their
own operations.
This document describes options for a self-forming, self-managing and
self-protecting "Autonomic Control Plane" (ACP) which is inband on
the network, yet as independent as possible of configuration,
addressing and routing problems (for details how this achieved, see
Section 6). It therefore remains operational even in the presence of
configuration errors, addressing or routing issues, or where policy
could inadvertently affect control plane connectivity. 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 substrate".
o An operator can use it to log into remote devices, even if the
data plane is misconfigured or unconfigured.
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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 some use cases for the ACP in Section 3, it
defines the requirements in Section 4, Section 5 gives an overview
how an Autonomic Control Plane is constructed, and in Section 6 the
detailed process is explained. Section 8 explains how non-autonomic
nodes and networks can be integrated, and Section 6.7 the first
channel types for the ACP.
The document "Autonomic Network Stable Connectivity"
[I-D.ietf-anima-stable-connectivity] describes how the ACP can be
used to provide stable connectivity for OAM applications. It also
explains on how existing management solutions can leverage the ACP in
parallel with traditional management models, when to use the ACP
versus the data plane, how to integrate IPv4 based management, etc.
2. Terminology
This document uses the following terms (sorted alphabetically):
ACP "Autonomic Control Plane". The Autonomic Function defined in
this document. It provides secure zero-touch network wide IPv6
connectivity between devices supporting it. 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.
ACP address An IPv6 ULA address assigned to the ACP device. It is
stored in the ACP information field of an ACP devices LDevID.
ACP connect A physical interface on an ACP device providing access
to the ACP for non ACP capable devices. See Section 8.1.
ACP device A device supporting the ACP according to this document.
ACP information (field) An rfc822Name information element (eg:
field) in the Domain Certificate in which the ACP relevant
information is encoded: the AN Domain Name and the ACP address.
ACP (loopback) interface The loopback interface in the ACP VRF that
hosts the ACP address.
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ACP secure channel A virtual subinterface/tunnel established hop-by-
hop between adjacent ACP devices to carry traffic of the ACP VRF
separated from Data Plane traffic inband over the same links as
the Data Plane.
ACP secure channel protocol The protocol used to build an ACP secure
channel, eg: IKEv2/IPsec or dTLS.
ACP virtual interface An interface in the ACP VRF mapped to one or
more ACP secure channels. See Section 6.12.4.
ACP VRF The ACP is modelled in this document as a "Virtual Routing
and Forwarding" (VRF) component in a network device.
AN "Autonomic Network". A network according to
[I-D.ietf-anima-reference-model]. Its main components are Intent,
Autonomic Functions and ANI.
AN Domain Name A string name (typically in a format of a DNS domain
name) identifying an Autonomic Network. It is stored in the ACP
information field of an ANI devices LDevID.
ANI (device/network) "Autonomic Network Infrastructure". A device
with ANI supports ACP, BRSKI and GRASP. The ANI is the
infrastructure to enable autonomic functions. An ANI network or
device is a most basic Autonomic Network or device: it does not
need to have ASAs other than the ones implementing ACP, BRSKI and
GRASP nor Intent support. A simple ANI network (without further
autonomic functions) can for example support secure zero touch
bootstrap and stble connectivity for SDN networks - see
[I-D.ietf-anima-stable-connectivity].
ANIMA "Autonomic Networking Integrated Model and Approach". ACP,
BRSKI and GRASP are work products of ANIMA.
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 Devices.
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 devices use ACP and BRSKI.
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Data Plane The counterpoint to the ACP in an ACP device: all VRFs
other than the ACP. In a simple ACP or ANI device, the Data Plane
is typically provisioned non-autonomic, for example manually
(including across the ACP) or via SDN controllers. In a full
Autonomic Network Device, the Data Plane is managed autonomically
via Autonomic Functions and Intent.
Domain Certificate An LDevID with an information element defined in
this document used by the ACP to derive and cryptographically
assert its membership in an autonomic domain.
enrollment The process where a device 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 device 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 device in the context of its
vendor/manufacturer such as device model/type and serial number.
LDevID A "Local Device IDentity" X.509 certificate installed during
an "enrollment". The ACP depends on a Domain Certificate which is
an LDevID.
MIC "Manufacturer Installed Certificate". Another word not used in
this document to describe an IDevID.
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.
sUDI "secured Unique Device Identifier". Another term not used in
this document to refer to an IDevID.
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UDI "Unique Device Identifier". In the context of this document
unsecured identity information of a device typically consisting of
at least device model/type and serial number, often in a vendor
specific format. See sUDI and LDevID.
ULA "Unique Local Address". The IPv6 equivalent to RFC1918 IPv4
addresses. ACP addresses are ULA.
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 minimise
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 an Unconfigured Network
Today, bootstrapping a new device typically requires all devices
between a controlling node (such as an SDN controller) and the new
device to be completely and correctly addressed, configured and
secured. Therefore, bootstrapping a network happens in layers around
the controller. 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 between.
With the ACP, secure bootstrap of new devices can happen without
requiring any configuration on the network. 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 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 certain AAA misconfigurations 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
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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 NOC/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 largely independent of the data
plane, 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 devices 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.
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.
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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 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 default mode of operation of the ACP is 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 over non-autonomic
nodes, for example to link autonomic nodes over the general Internet.
This is possible, but then has a dependency on routing over the non-
autonomic hops (see Section 8.2).
5. Overview
The Autonomic Control Plane is constructed in the following way (for
details, see Section 6):
1. An autonomic node creates a virtual routing and forwarding (VRF)
instance, or a similar virtual context.
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 adjacent nodes in the
same domain.
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 virtual (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.
Note:
o Non-autonomic NMS systems or controllers have to be manually
connected into the ACP.
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o Connecting over non-autonomic Layer-3 clouds initially requires a
tunnel between autonomic nodes.
o None of the above operations (except manual ones) is reflected in
the configuration of the device.
The following figure illustrates the ACP.
autonomic node 1 autonomic node 2
................... ...................
secure . . secure . . secure
tunnel : +-----------+ : tunnel : +-----------+ : tunnel
..--------| ACP VRF |---------------------| ACP VRF |---------..
: / \ / \ <--routing--> / \ / \ :
: \ / \ / \ / \ / :
..--------| virtual |---------------------| virtual |---------..
: | interface | : : | interface | :
: +-----------+ : : +-----------+ :
: : : :
: data plane :...............: data plane :
: : link : :
:.................: :.................:
Figure 1
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
devices, 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 steps to set up an Autonomic Control Plane
(ACP), and highlights the key properties which make it
"indestructible" against many inadvert changes to the data plane, for
example caused by misconfigurations.
An ACP device can be a router, switch, controller, NMS host, or any
other IP device. Initially, it must have a globally unique domain
certificate (LDevID), as well as an adjacency table. It then can
start to discover ACP neighbors and build the ACP. This is described
step by step in the following sections:
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6.1. Domain Certificate
To establish an ACP securely, an ACP device MUST have a globally
unique domain certificate (LDevID), with which it can
cryptographically assert its membership in the domain as well as the
CA certificate chain used to sign the LDevID. This CA certificate
chain is used to verify the LDevID of candidate ACP peers (see
Section 6.6). The ACP does not mandate specific mechanism by which
this certificate information is provisioned onto the ACP device, it
only requires the following ACP specific information field in its
LDevID as well as the LDevIDs of candidate ACP peers. See
Section 10.1 for more information about enrollment or provisioning
options.
6.1.1. ACP information
The domain certificate (LDevID) of an autonomic node MUST contain ACP
specific information, specifically the domain name, the address of
the device in the ACP with the Zone-ID set to zero ("ACP address").
This information MUST be encoded in the LDevID in the subjectAltName
/ rfc822Name field in the following way:
anima.acp+<acp-address>{+<rsub>{+<extensions>}}@<domain>
Example:
anima.acp+fda379A6f6ee00000200000064000001+area51.research@acp.exampl
e.com
The acp-address MUST be specified as a string of 32 hex characters
with only lower letters a-f and numbers 0-9 so that the local part of
the address can matches the simple dot-atom format of [RFC5322] (":"
are not allowed in that format).
<domain> is used to indicate the autonomic "domain" across which all
ACP nodes trust each other and are willing to build ACP channel with
each other. See Section 6.6.
{<rsub>.}<domain> is the autonomic "routing subdomain" that is used
used in addressing to calculate the hash used in the creation of the
ACP address of the device. As the name implies, every routing
subdomain is also a separate routing subdomain. <rsub> is optional
and should only used when its impacts are understood. The domain
without any leading rsub field is also just another routing
subdomain.
The optional <extensions> field is used for future extensions to this
specification. It MUST be ignored if present and not understood.
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The subjectAlName / 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
incompatibilites 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 ACP information, for example 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
device 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 encoded "ACP information (field)".
o The format of the rfc822Name is choosen so that an operator can
set up a mailbox called anima.acp@<domain> that would receive
emails sent towards the rfc822Name of any AN device inside a
domain. This is possible because components behind a plus symbol
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are considered part of a single mailbox. In other words, it is
not necessary to set up a separate mailbox for every autonomic
devices ACP information field, 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. Maintenance
The ACP network MUST have one or more nodes that support EST server
([RFC7030] functionality (eg: as an ASA) through which ACP nodes can
renew their domain certificate. The ACP address of at least one such
EST server SHOULD have been enrolled/provisioned into the ACP device
during initial installation of the domain certificate.
EST servers MUST announce their service via GRASP in the ACP through
M_FLOOD messages:
Example:
[M_FLOOD, 12340815, h'fda379a6f6ee0000200000064000001', 180000,
["AN_join_registrar", SYNCH-FLAG, 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 = ["AN_join_registrar", objective-flags, loop-count,
objective-value]
objective-flags = SYNCH-FLAG ; as in GRASP spec
loop-count = 255 ; mandatory maximum
objective-value = text ; name of the (list of) of supported
; protocols: "EST-TLS" for RFC7030.
The M_FLOOD message MUST be sent periodic. The period is subject to
network administrator policy (EST server configuration). It must be
so low that the aggregate amount of periodic M_FLOOD from all EST
servers causes negligible traffic across the ACP.
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In the above (recommended) example the period could be 60 seconds and
the indicated ttl of 180000 msec means that the objective would
continuously be cached by ACP devices even when two out of three
messages are dropped in transit (which is unlikely because GRASP hop-
by-hop forwarding is realiable).
The locator-option indicates the ACP transport address for the EST
server. The loop-count MUST be sete to 255. When an ACP node
receives the M_FLOOD, it will have been reduced by the number of hops
from the EST server.
When it is time for domain certificate reneal, the ACP device MUST
attempt to connect to the EST server(s) learned via GRASP starting
with the one that has the highest remaining loop-count (closest one).
If certificate renewal does not succeed, the device MUST attempt to
use the EST server(s) learned during initial provisioning/enrollment
of the certificate. After successful renewal of the domain
certificate, the ACP address from the certificate of the EST server
(as learned during the TLS handshake) is added to the top of the list
or provisioned/configured EST-server(s).
This logic of selecting an EST server for renewal is choosen to allow
for distributed EST servers to be used effectively but to also allow
fallback to the most reliably learned EST server - those that
performed already successful enrollment in before. A compromised
(non EST-server) ACP device for example can filter or fake GRASP
announcements, but it can not successfully renew a certificate and
can only prohibit traffic to a valid EST server when it is on the
path between the ACP device and the EST server.
The ACP device MUST support Certificate Revocation Lists via HTTPs
from one or more Certificate Distribution Points. These CDPs MUST be
indicated in the Domain Certificate when used. If the CDP URL uses
an IPv6 ULA, the ACP device 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 device during the HTTPs TLS handshake MUST 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 device 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 imiting factor for shorter certificate lifetimes (than the
typical one year) is load on the EST server(s) and CA. It is
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therefore recommended that ACP domain certificates are managed via a
CA chain where the assigning CA has enough peformance to manage short
lived certificates.
See Section 10.1 for further optimizationss of certificate
optimizations when BRSKI can be used.
6.2. AN Adjacency Table
To know to which nodes to establish an ACP channel, every autonomic
node maintains an adjacency table. The adjacency table contains
information about adjacent autonomic nodes, at a minimum: node-ID, IP
address, domain, certificate. An autonomic device 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 autonomic device 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 autonomic node's certificate. However,
subsequent steps MUST always start with authenticating the peer.
The adjacency table contains information about adjacent autonomic
nodes in general, independently of their domain and trust status.
The next step determines to which of those autonomic nodes an ACP
connection should be established.
6.3. Neighbor Discovery with DULL GRASP
Because of the the considerations in Section 10.2, the ACP uses DULL
(Discovery Unsolicited Link-Local) insecure instances of GRASP for
discovery of ACP neighbors. See section 3.5.2.2 of
[I-D.ietf-anima-grasp] for its formal definition.
The ACP uses one instance of DULL GRASP for every physical L2 subnet
of the ACP device to discovery physcially adjacent candidate ACP
neighbors. Ideally, all physcial interfaces SHOULD be brought up
enough so that ACP discovery can be performed and any physcially
connected 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 unconfigure 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 (eg: no other link-
local IPv6 transport stack responders for example).
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ACP discovery MUST NOT be enabled by default on any non-physcial
interfaces. See Section 8.2.2 how to enable and use ACP with auto-
discovery across configured tunnels.
See Section 7 for how ACP should be extended on L3/L2 devices.
Note: If an ACP device 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 device does not
have a domain certificate. Discovery of ACP neighbors happens only
when the device does have the certificate. The device therefore
never needs to discover both a bootstrap proxy and ACP neighbor at
the same time.
An autonomic node announces itself to potential ACP peers by use of
the "AN_ACP" objective. This is a synchronization objective intended
to 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, 1,
["AN_ACP", SYNCH-FLAG, 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 = ; as in the GRASP specification
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 ttl and loop-count are fixed at 1 since this is a link-local
operation.
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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
autonomic 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.
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. For example, "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 "AN_join_proxy"
objective in the same flood message, since GRASP allows multiple
objectives in one Flood message. This may be impractical though if
ACP and BRSKI operations are implemented via separate software
modules / ASAs though.
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 AN Adjacency
Table, see Section 6.2 which then drives the further building of the
ACP to that neighbor.
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6.4. Candidate ACP Neighbor Selection
An autonomic node must determine to which other autonomic nodes in
the adjacency table it should build an ACP connection. This is based
on the information in the AN Adjacency table.
The ACP is by default established exclusively between nodes in the
same domain. This includes all routing subdomains. Section 10.5
explains how ACP connections across routing subdomains are special.
Future extensions to this document including Intent can change this
default behaviour. 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 domain with different CA (certificate
authorities) could establish a common ACP by prior adding the
other domains CA as recognized trust anchors.
Since Intent is transported over the ACP, the first ACP connection a
node establishes is always following the default behaviour. See
Section 10.5 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 can not
include any non-protected negotiation. To avoid re-inventing and
validating security association mechanisms, the next step after
discoving 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 autonomic devices, it is unclear
whether it is feasible to even decide on a single MTI (mandatory to
implement) security association protocol across all autonomic
devices:
From the use-cases it seems clear that not all type of autonomic
devices can or need to connect directly to each other or are able to
support or prefer all possible mechanisms. For example, code space
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limited IoT devices may only support dTLS (because that code exists
already on them for end-to-end security use-cases), but low-end in-
ceiling L2 switches may only want to support MacSec because that is
also supported in HW, and only a more 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, autonomic devices 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 autonomic device may choose to attempt initiate the different
feasible ACP secure channel protocol 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 others certificates (because that must be used by all secure
channel protocols for mutual authentication. The device with the
lower Device-ID in the ACP address becomes Bob, the one with the
higher Device-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 preferred and the security
association succeeded. The roles of Bob abd Alice are then assigned.
At this stage, the protocol may not even have completed negotiating a
common security profile. The protocol could for example have been
IPsec. It is not up to Alice to devide how to proceed. Even if the
IPsec connecting determined a working profile with Bob, Alice might
prefer some other secure protocol (eg: 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.
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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 device must not
assume that neighbors with the same L2 or link-local IPv6 addresses
on different L2 interfaces are the ame devices. This can only be
determined after examining the certificate after a successful
security association attempt.
6.6. Candidate ACP Neighbor certificate verification
Independent of the security association protocol choosen, candidate
ACP neighbors need to be authenticated based on their autonomic
domain certificate. This implies that any security association
protocol MUST support certificate based authentication that can
support the following verification steps:
o The certificate is valid as proven by the security associations
protocol exchanges.
o The peers certificate is signed by the same CA as the devices
domain certificate.
o If our devices certificate indicates a CDP or OCSP then the peers
certificate must be valid occrding to those (eg: OCSP check across
the ACP or not listed in the CRL).
o The peers certificate has a valid ACP information field
(subjectAltName / rfc822Name) and the domain name in that peers
ACP information field is the same as in the devices certificate.
Note that future Intent rules may modify this for example in
support of subdomains. See Section 10.5.
If the peers certificate fails any of these checks, 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 autonomic device announces its ability to support IKEv2 as the ACP
secure channel protcol in GRASP as "IKEv2".
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6.7.1.1. Native IPsec
To run ACP via IPsec transport mode, no further IANA assignments/
definitions are required. All autonomic devices supporting IPsec
MUST support IPsec security setup via IKEv2, transport mode
encapsulation via the device and peer link-local IPv6 addresses,
AES256 encryption and SHA256 hash.
In terms of IKEv2, this means the initiator will offer to support
IPsec transport mode with next protocol equal 41 (IPv6).
6.7.1.2. IPsec with GRE encapsulation
In network devices it is often easier to provide virtual interfaces
on top of GRE encapsulation than natively on top of a simple IPsec
association. On those devices it may be necessary to run the ACP
secure channel on top of a GRE connection protected by the IPsec
association. The requirements for the IPsec association are the same
as in the native IPsec case, but instead of directly carrying the ACP
IPv6 packets, the payload is an ACP IPv6 packet inside GRE/IPv6. The
mandatory security profile is the same as for native IPsec: peer
link-local IPv6 addresses, AES256 encryption, SHA256 hash.
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 41 (IPv6) (because native IPsec is required to be
supported, see below).
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 autonomic devices supporting
ACP via dTLS 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
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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 autonomic device MUST support IPsec natively and MAY
support IPsec via GRE. A constrained autonomic device MUST support
dTLS. Autonomic edge device connecting constrained areas with
baseline areas MUST therefore support IPsec and dTLS.
Autonomic devices need to specify in documentation the set of secure
ACP mechanisms they suppport.
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 it was
added as an afterthought and relied upon inconsistently resulting in
diminished self configuration capabilities. of prior solutions.
The ACP does not provide generic IP multicast services, but only IP
unicast which is realized via the RPL routing protocol (described
below) and objective discovery and negotiation realized via the ACP
instance of GRASP. We consider this to be a more lightweight,
modular and easier to extend approach than trying to put service
announcement and discovery onto some autoconfigured network wide IP
multicast layer (for which so far there is no good definition) or
embed it into some IGP flooding mechanism (which makes it less
modular and agile to improve upon).
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.
This means that the ACP is responsible to ensure that this instance
of GRASP is only using the ACP virtual 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 device has a domain certificate.
In this case ASAs using GRASP running on the same device would still
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need to be able to discover each others 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
provide services.
GRASP inside the ACP uses link-local UDP IPv6 multicast across the
ACP virtual interfaces for GRASP neighbor discovery and IPv6 over TLS
across the ACP virtual interfaces for any of its unicast messages.
TLS is TLS 1.2 ([RFC5246]) with AES256 encryption and SHA256.
Authentication is via the the domain certificates on both sides.
TLS is mandated for GRASP 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 (eg: via domain
certificate revocation / expiry).
Eavesdropping/spoofing by a compromised ACP device is possible
because the provider and consumer of an objective have no unique
information about the other side that would allow them to distinguish
a benevolent from a compromised peer. The compromised ACP device
would simply announce the objective as well, potentially filter the
original objective in GRASP when it is a Man In The Middle (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.
6.9. Context Separation
The ACP is in a separate context from the normal data plane of the
device. This context includes the ACP channels IPv6 forwarding and
routing as well as any required higher layer ACP functions.
In classical network device platforms, a dedicated so called "Virtual
routing and forwarding instance" (VRF) is one logical implementation
option for the ACP. If possible by the platform SW 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 device. 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.
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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 internal
network wide valid addresses and routing. Each autonomic node must
create a virtual interface with a network wide unique address inside
the ACP context mentioned in Section 6.9. This address may be used
also in other virtual contexts.
With the algorithm introduced here, all ACP devices in the same
subdomain have the same /48 prefix. Conversely, 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).
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 loopback interfaces of autonomic nodes carry
routable address(es); all other interfaces exclusively use IPv6
link local for autonomic functions. The usage of IPv6 link local
addressing is discussed in [RFC7404].
o Use-ULA: For loopback interfaces of autonomic 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.
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o Addresses in the ACP are permanent, and do not support temporary
addresses as defined in [RFC4941].
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.
6.10.2. The ACP Addressing Base Scheme
The Base ULA addressing scheme for autonomic nodes has the following
format:
8 40 2 78
+--+-----------------+------+------------------------------------------+
|FD| hash(subdomain) | Type | (sub-scheme) |
+--+-----------------+------+------------------------------------------+
Figure 2: 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 ULA "global ID" is set here to be a hash of the subdomain
name, which results in a pseudo-random 40 bit value. It is
calculated as the first 40 bits of the SHA256 hash of the
subdomain name, in the example of Section 6.1.1
"area51.research.acp.example.com".
o To allow for extensibility, the fact that the ULA "global ID" is a
hash of the subdomain name SHOULD NOT be assumed by any autonomic
device 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 ACP information field in
response to the CSR Attribute Request by the pledge.
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o Type: This field allows different address sub-schemes in the
future. The goal is to start with a single sub-schemes, but to
allow for extensions later if and when required. This addresses
the "upgradability" requirement. Assignment of types for this
field should be maintained by IANA.
6.10.3. ACP Zone Addressing Sub-Scheme
The sub-scheme defined here is defined by the Type value 0 (zero) in
the base scheme.
51 1 13 63 1
+---------------------+---+---------+-----------------------------+---+
| (base scheme) | Z | Zone-ID | Device-ID | V |
| | | | Registrar-ID | Device-Number| |
+---------------------+---+---------+--------------+--------------+---+
48 15
Figure 3: ACP Zone Addressing Sub-Scheme
The fields are defined as follows:
o Z: MUST be 0. This is an unused bit in this scheme that allows
for another encoding scheme to be defined in the future with this
bit set to 1.
o Zone-ID: If set to all zero bits: The Device-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 Section 6.10.3.1 on how this field is used in
detail.
o Device-ID: A unique value for each device.
o V: Virtualization bit: 0: autonomic node base system; 1: a virtual
context on an autonomic node.
The Device-ID is derived as follows: In an Autonomic Network, a
registrar is enrolling new devices. As part of the enrolment process
the registrar assigns a number to the device, which is unique for
this registrar, but not necessarily unique in the domain. The 64 bit
Device-ID is then composed as:
o 48 bit: Registrar ID, a number unique inside the domain that
identifies the registrar which assigned the name to the device. A
MAC address of the registrar can be used for this purpose.
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o 15 bit: Device number, a number which is unique for a given
registrar, to identify the device. This can be a sequentially
assigned number.
The "Device-ID" itself is unique in a domain (i.e., the Zone-ID is
not required for uniqueness). Therefore, a device 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.
V:0 is the ACP router (autonomous node base ssystem), V:1 is the host
with pre-existing transport endpoints on it that could collide with
the transport endpoints used by the AP router. The host can have a
virtual p2p interface with the V:0 address as its router into the
ACP. Depending on the SW design of systems, future ASA 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 autonomic node, while having
separate virtual contexts addressable directly.
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 autonomic domain.
Every autonomic 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 8191
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 device 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.
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(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
autonomic domain. This gives followup work two options to consider.
6.10.4. ACP V8 Addressing Sub-Scheme
The sub-scheme defined here is defined by the Type value 1 (one) in
the base scheme.
51 63 8
+---------------------+-----------------------------+----------+
| (base scheme) | Device-ID | V |
| | Registrar-ID | Device-Number| |
+---------------------+--------------+--------------+----------+
46 32
Figure 4: ACP V8 Addressing Sub-Scheme
This addressing scheme foregoes the Zone field to allow for larger,
flatter networks (eg: as in IoT) with up to 2^32 Device-Numbers. It
also allows for up to 2^8 - 256 different virtualized adddresses,
which could be used to address individual linecards or the like.
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,
values 2-255 for use via definition in followup work.
o Registrar-ID: To maximize Device-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 can not be used
to distinguish MAC addresses anyhow).
6.10.5. Other ACP Addressing Sub-Schemes
Other ACP addressing sub-schemes can be defined if and when required.
IANA would need to assign a new "type" for each new addressing sub-
scheme. With the current allocations, 5 more schemes are possible
without further reducing the number of bits in a future scheme.
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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 10.3 for more details on the choice of RPL.
RPL adjacencies are set up across all ACP channels in the same domain
including all its routing subdomains. See Section 10.5 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 choosen for RPL is one that expect 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 choosen profile is that it is design to not
require any dataplane artefacts. The sender/receivers of ACP packets
can be legacy NOC devices connected via "ACP connect" (see
Section 8.1 to the ACP. These devices could not handle RPL data
plane artefacts. The profile also avoids the complexity of
performing IpinIP encap/decap on ACP routers to deal with non-RPL
dataplane artefacts.
In return for this profile choice, RPL has no dataplane artefacts and
install just a simple destination prefix based routing table. As a
downside it will only create a DODAG for one root which will be
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either configured (eg: ACP connect NOC edge device) or a registrar
(likely the same ACP connect NOC edge device). Consider a network
has multiple NOCs in different locations, then only paths to the one
NOC with the RPL root will be optimal, the other ones will not be
optimal.
Future Extensions to this RPL profile can provide optimality for
multiple NOCs. This requires utilizing data plane artefacts
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)
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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 (eg: 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 seleced 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 device (RPL node) announces an IPv7 prefix covering the
address(es) used internally in the ACP device. The prefix length
depends on the choosen mode of the ACP address provisioned into the
certificate of the ACP device and is either /96 or /127. See
Section 6.10 for more details.
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
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o AN-connect (non registrar): 0b010
o Default: 0b001.
6.11.1.13. RPL Dataplane artifacts
RPI (RPL Packet Information): Not used. Because we are only using a
single instance and because we are not using data path validation.
SRH (RPL Source Routing - RFC6552): Not used. Because we are using
storing mode.
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. 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
specify extensions in which secure channels are tunnels, then 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
(eg: IPsec / dTLS) across IPv6 link-local addresses, something that
may be an uncommon profile. Functionaly, 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 (eg: tunneling across L3 or
use of L2 only encapsulations).
6.12.2. MTU
The MTU for ACP secure channels must be derived locally from the
underlying link MTU minus the secure channel encapsulation overhead.
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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.
6.12.3. 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 devices, 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 (eg: on a
different link or with a different address announced in GRASP).
6.12.4. 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 is commonly referred to internal pseudo
interfaces through which the device can only reach itself. In
network devices these interfaces are used to hold addresses used by
the transport stack of the system when an address should be reliable
reachable in the presence of arbitrary link failures. As long as
addresses on a loopback interface are routeable in the routing
protocol used, they will be reachable as long as there is at least
one working network path. This is opposed to routeable address
assigned to an externally connected interface. That address will
become unreachable when that interface goes down. For this reason,
the ACP (ULA) address(es) are assigned to loopback type interface.
ACP secure channels, eg: IPsec, dTLS or other future security
associations with neighboring ACP devices can be mapped to ACP
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virtual interfaces in different ways: In one case, every 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. 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 physical subnet. The multi-access
ACP virtual interace needs to replicate link-local IPv6 multicast
packets sent into the interface towards all ACP secure channels
mapped into it. There is no need for all ACP capable nodes on the
same physcial multi-access subnet to agree on a common implementation
approach. This is purely a node local decision.
Multi-access ACP virtual interfaces are preferrable because they do
reflect the presence of a multi-access physcial networks 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 habe been built running natively on the multi-
access interfaces. One example is the efficiency of flooding of
GRASP messages. Assume such a LAN with three ACP neighbors, Alice
Bob and Carol. Alice sends a GRASP link-local multicast message to
Bob and Carol. If Alices ACP emulates the LAN as one point-to-point
interface to Bob and one to Carol, GRASP itself will send two copies,
if Alices 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 point-to-point
ACP virtual interfaces, their GRASP instance would forward the packet
from Alice to each other as part of the GRASP flooding procedure.
These packets are of course redundant (unnecessary) and would be
discarded by GRASP on receipt as duplicates. If Bob and Charlies ACP
would emulate a LAN, then this would not happen, because GRASPs
flooding procedure does not send bac packets to the interface they
where received from.
For this reason, the ACP SHOULD map ACP secure channels on multi-
access LANs into multi-access ACP virtual interfaces.
Care must be taken when creating multi-access ACP virtual interfaces
across ACP secure channels between ACP devices 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 point-to-point ACP virtual interfaces for these secure
channels.
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7. ACP support on L2 switches/ports (Normative)
7.1. Why
ANrtr1 ------ ANswitch1 --- ANswitch2 ------- ANrtr2
.../ \ \ ...
ANrtrM ------ \ ------- ANrtrN
ANswitchM ...
Figure 5
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 AN router will see all other AN 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 neigbors. An AN router with just 4 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.
Predictable scaling requirements for ACP neighbors can most easily be
achieved if in topologies like these, AN capable L2 switches can
ensure that discovery messages terminate on them so that neighboring
AN routers and switches will only find the physcially connected AN 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 physcial 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 AN
capable, and ANswitch2 is not AN capable. The desired ACP topology
is therefore that ANrtr1 and ANrtrM only have an ACP connetion to
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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 switches ports of an L3 device,
it is necessary to 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 IPv6 link-local multicast address, it is
sufficient that all ethernet 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.
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
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 6.12.4 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
threfore 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 perfom 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
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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", eg:
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
depend on STP and can continue to run unaffected across STP topology
changes (where reconvergence 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
therefore the ACP would equally be interrupted and reconverge with
STP changes.
L3/L2 devices SHOULD support per-L2 port ACP.
8. Workarounds for Non-Autonomic Nodes (Normative)
8.1. Non-Autonomic Controller / NMS system (ACP connect)
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 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-autonomic
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NMS system does not have access to the ACP by default, just like any
other external device.
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-
autonomic nodes, an autonomic node with ACP must support "ACP
connect" (sometimes also connect "autonomic connect"):
"ACP connect" is a function on an autonomic device that we call an
"ACP edge device". With "ACP connect", interfaces on the device 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).
data-plane "native" (no ACP)
.
+-----------+ +-----------+ . +-------------+
| | | Autonomic | v | |+
| | | Device |-----------------| |+
| Autonomic |-----------|"ACP edge | | NOC Device ||
| Device | ^ | device" O-----------------| "NMS hosts" ||
| | . | | . ^ | ||
+-----------+ . +-----------+ . . +-------------+|
. . . +-------------+
data-plane "native" . ACP "native" (unencrypted)
+ ACP auto-negotiated .
and encrypted ACP connect interface
eg: "vrf ACP native" (config)
Figure 6: ACP connect
ACP connect has security consequences: All systems and processes
connected via ACP connect have access to all autonomic nodes on the
entire ACP, without further authentication. Thus, the ACP connect
interface and (NOC) systems connected to it must be physically
controlled/secured.
The ACP connect interface must be configured with some IPv6 address
prefix. This prefix could use the ACP address prefix or could be
different. It must be distributed into the ACP routing protocol
unless the ACP device is the root of the ACP routing protocol (eg:
when all other autonomic devices have a default route in the ACP
towards it). The NOC hosts must route the ACP address prefix to the
ACP edge devices address on the ACP connect interface.
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An ACP connect interface provides exclusively access to only the ACP.
This is likely insufficient for many NOC hosts. Instead, they would
likely require a second interface outside the ACP for connections
between the NMS host and administrators, or Internet based services,
or even 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.
Note: If an NMS host is autonomic itself, it negotiates access to the
ACP with its neighbor, like any other autonomic node and then runs a
normal (encrypted) ACP connection to the neighbor.
8.2. ACP through Non-Autonomic L3 Clouds (Remote ACP neighbors)
Not all devices 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 neigbhors 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 autonomic device 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
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.
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The secure channel method leverages the configuration to filter
incoming connection requests by the remote IP address. This is
suplemental security. The primary security is via the mutual domain
certificate based authentication of the secure channel protocol.
On a hub device, the remote IP address may be set to some pattern
instead of explicit IP addresses. In this case, the device 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
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 physical
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.
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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 devices 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 devices.
o If an existing device 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 device can be re-set.
The ACP can also sustain network partitions and mergers. Practically
all ACP operations are link local, where a network partition has no
impact. Devices 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.
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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 devices 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 devices can be enrolled everywhere. Since all devices 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 whicht the ACP is
running. Especially if bringing down the ACP is known to disconnect
the operator from the device. 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 devices 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.
An attacker will therefore 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.
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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 devices 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 can not
eavesdrop or modify communications, they can just filter them (which
is unavoidable by any means).
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.
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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 devices, 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 device 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 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 (eg: bootstrap), that explain decisions made in this
document (eg: choice of GRASP) or that explain desirable extensions
to the behavior of the ACP that are not far enough worked out to be
already standardized in this document.
10.1. Domain Certificate provisioning / enrollment
[I-D.ietf-anima-bootstrapping-keyinfra] (BRSKI) describes how devices
with an IDevID certificate can securely and zero-touch enroll with a
domain certificate to support the ACP. BRSKI also leverages the ACP
to enable zero touch bootstrap of new devices across networks without
any configuration requirements across the transit devices (eg: no
DHCP/DS forwarding/server setup). This includes otherwise
unconfigured 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. Devices supporting such
an infrastructure (BRSKI and ACP) are called ANI devices (Autonomic
Networking Infrstructure), see [I-D.ietf-anima-reference-model].
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Devices that do not support an IDevID but only an (insecure) vendor
specific Unique Device Identifier (UDI) or devices 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 device (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 this, and
create the respective 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 device fails to
connect to the ACP within its certificate lifetime, it can not
connect to the ACP to renew its certificate across it, but it can
still renew its certificate as an "enrolled/expired pledge" via the
BRSKI bootstrap proxy. This requires only that the enhanced EST
server that is part of BRSKI 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 also replaces
CRLs because the EST server (in conunction with the CA) would not
renew revoked certficates - but in this scheme only the EST-server
need to know which certificate was revoked.
In the absence of BRSKI or less secure variants thereof, provisioning
of certificates may involve one or more touches or non-standardized
automation. Device vendors usually support provisioning of
certificates into devices via PKCS#7 (see [RFC2315]) and may support
this provisioning through vendor specific models via Netconf
([RFC6241]). If such devices also support Netconf Zerotouch
([I-D.ietf-netconf-zerotouch]) then this can be combined to zero-
touch provisioning of domain certificates into devices. 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 an unconfigured network though.
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10.2. ACP Neighbor discovery protocol selection
This section discusses why GRASP DULL was choosen as the discovery
protocol for L2 adjacent candidate ACP neighbors. The contenders
considered where GRASP, mDNS or LLDP.
10.2.1. 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.
10.2.2. 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 devices. With low
performance of software forwarding in many L2 switches, this could
also make the ACP risky to support on such L2 switches.
10.2.3. 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 device, 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
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implementation of DULL GRASP or a shared implementation of DULL GRASP
and GRASP in the ACP.
10.3. 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]).
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 synchronisation.
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
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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 behaviour.
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.
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).
10.4. 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
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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
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 multitide 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 devices 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
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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.
10.5. CAs, domains and routing subdomains considerations
There is a wide range of setting up different ACP solution by
appropriately using CAs and the domain and rsub elements in the ACP
information field of the domain certificate. We summarize 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 devices using certificates from
the same CA using the same domain field. GRASP inside the ACP is run
across all transitively connected ACP devices in a domain.
The rsub element in the ACP 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 (eg: via GRASP). This is subject for further work.
RPL scales very well. It is not necessary to use multiple routing
subdomains to scale autonomic domains in a way it would be possible
if other routing protocols where used. They exist only as options
for the above mentioned reasons.
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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 ACP 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 ACP information
element of certificates.
It is not necessary to have a sparate 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".
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 devices,
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 build 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 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 (eg: GRASP negotiation).
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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
device.
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.
12. IANA Considerations
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, Ravi
Kumar Vadapalli.
Special thanks to Pascal Thubert to provide the details for the
recommendations of the RPL profile to use in the ACP
Further input and suggestions were received from: Rene Struik, Brian
Carpenter, Benoit Claise.
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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.
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.
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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.
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.
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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.
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).
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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 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.
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.
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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.
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
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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 signalled via GRASP.
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 Zerotouch. 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.
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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, eg: with domain certificate.
Enhanced initial domain certificate section to include requirements
for maintenance (renewal/revocation) of certificates. Added
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.
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Added V8 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.
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.
[RFC4193] Hinden, R. and B. Haberman, "Unique Local IPv6 Unicast
Addresses", RFC 4193, DOI 10.17487/RFC4193, October 2005,
<http://www.rfc-editor.org/info/rfc4193>.
[RFC5246] Dierks, T. and E. Rescorla, "The Transport Layer Security
(TLS) Protocol Version 1.2", RFC 5246,
DOI 10.17487/RFC5246, August 2008,
<http://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,
<http://www.rfc-editor.org/info/rfc5280>.
[RFC5322] Resnick, P., Ed., "Internet Message Format", RFC 5322,
DOI 10.17487/RFC5322, October 2008,
<http://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, <http://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,
<http://www.rfc-editor.org/info/rfc6550>.
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[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,
<http://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,
<http://www.rfc-editor.org/info/rfc7030>.
[RFC7676] Pignataro, C., Bonica, R., and S. Krishnan, "IPv6 Support
for Generic Routing Encapsulation (GRE)", RFC 7676,
DOI 10.17487/RFC7676, October 2015,
<http://www.rfc-editor.org/info/rfc7676>.
15.2. Informative References
[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-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-03 (work in progress), July
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-14 (work in progress), June
2017.
[RFC2315] Kaliski, B., "PKCS #7: Cryptographic Message Syntax
Version 1.5", RFC 2315, DOI 10.17487/RFC2315, March 1998,
<http://www.rfc-editor.org/info/rfc2315>.
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[RFC4941] Narten, T., Draves, R., and S. Krishnan, "Privacy
Extensions for Stateless Address Autoconfiguration in
IPv6", RFC 4941, DOI 10.17487/RFC4941, September 2007,
<http://www.rfc-editor.org/info/rfc4941>.
[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,
<http://www.rfc-editor.org/info/rfc6241>.
[RFC6762] Cheshire, S. and M. Krochmal, "Multicast DNS", RFC 6762,
DOI 10.17487/RFC6762, February 2013,
<http://www.rfc-editor.org/info/rfc6762>.
[RFC6763] Cheshire, S. and M. Krochmal, "DNS-Based Service
Discovery", RFC 6763, DOI 10.17487/RFC6763, February 2013,
<http://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,
<http://www.rfc-editor.org/info/rfc7404>.
[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,
<http://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,
<http://www.rfc-editor.org/info/rfc7576>.
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
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Steinthor Bjarnason
Arbor Networks
2727 South State Street, Suite 200
Ann Arbor MI 48104
United States
Email: sbjarnason@arbor.net
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