ANIMA WG M. Behringer, Ed.
Internet-Draft S. Bjarnason
Intended status: Standards Track Balaji. BL
Expires: April 8, 2016 T. Eckert
Cisco Systems
October 6, 2015
An Autonomic Control Plane
draft-ietf-anima-autonomic-control-plane-01
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
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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
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This Internet-Draft will expire on April 8, 2016.
Copyright Notice
Copyright (c) 2015 IETF Trust and the persons identified as the
document authors. All rights reserved.
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to this document. Code Components extracted from this document must
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described in the Simplified BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Use Cases for an Autonomic Control Plane . . . . . . . . . . 4
2.1. An Infrastructure for Autonomic Functions . . . . . . . . 4
2.2. Secure Bootstrap over an Unconfigured Network . . . . . . 4
2.3. Data Plane Independent Permanent Reachability . . . . . . 5
3. Requirements . . . . . . . . . . . . . . . . . . . . . . . . 5
4. Overview . . . . . . . . . . . . . . . . . . . . . . . . . . 6
5. Self-Creation of an Autonomic Control Plane . . . . . . . . . 8
5.1. Preconditions . . . . . . . . . . . . . . . . . . . . . . 8
5.2. Candidate ACP Neighbor Selection . . . . . . . . . . . . 8
5.3. Capability Negotiation . . . . . . . . . . . . . . . . . 9
5.4. Channel Establishment . . . . . . . . . . . . . . . . . . 9
5.5. Context Separation . . . . . . . . . . . . . . . . . . . 10
5.6. Addressing inside the ACP . . . . . . . . . . . . . . . . 10
5.7. Routing in the ACP . . . . . . . . . . . . . . . . . . . 12
6. Workarounds for Non-Autonomic Nodes . . . . . . . . . . . . . 12
6.1. Connecting a Non-Autonomic Controller / NMS system . . . 12
6.2. ACP through Non-Autonomic L3 Clouds . . . . . . . . . . . 13
7. The Negotiation Protocol . . . . . . . . . . . . . . . . . . 13
8. The Channel Type . . . . . . . . . . . . . . . . . . . . . . 13
9. Self-Healing Properties . . . . . . . . . . . . . . . . . . . 14
10. Self-Protection Properties . . . . . . . . . . . . . . . . . 15
11. The Administrator View . . . . . . . . . . . . . . . . . . . 15
12. Security Considerations . . . . . . . . . . . . . . . . . . . 16
13. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 16
14. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 16
15. Change log [RFC Editor: Please remove] . . . . . . . . . . . 17
15.1. Initial version . . . . . . . . . . . . . . . . . . . . 17
15.2. draft-behringer-anima-autonomic-control-plane-00 . . . . 17
15.3. draft-behringer-anima-autonomic-control-plane-01 . . . . 17
15.4. draft-behringer-anima-autonomic-control-plane-02 . . . . 17
15.5. draft-behringer-anima-autonomic-control-plane-03 . . . . 18
15.6. draft-ietf-anima-autonomic-control-plane-00 . . . . . . 18
15.7. draft-ietf-anima-autonomic-control-plane-01 . . . . . . 18
16. References . . . . . . . . . . . . . . . . . . . . . . . . . 19
Appendix A. Background on the choice of routing protocol . . . . 20
Appendix B. Alternative: An ACP without Separation . . . . . . . 21
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 22
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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.behringer-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.
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 5). 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.behringer-anima-reference-model]. For example, GRASP
[I-D.ietf-anima-grasp] can run inside the ACP.
o An operator can use it to log into remote devices, even if the
data plane is misconfigured or unconfigured.
o A controller or network management system can use it to securely
bootstrap network devices in remote locations, even if the network
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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 2, it
defines the requirements in Section 3, Section 4 gives an overview
how an Autonomic Control Plane is constructed, and in Section 5 the
detailed process is explained. Section 6 explains how non-autonomic
nodes and networks can be integrated, Section 7 defines the
negotiation protocol, and Section 8 the first channel types for the
ACP.
The document "Autonomic Network Stable Connectivity"
[I-D.eckert-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. Use Cases for an Autonomic Control Plane
2.1. 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.
2.2. 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.
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2.3. 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
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.eckert-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.
3. Requirements
The Autonomic Control Plane has the following requirements:
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1. 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.
2. 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).
3. 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.
4. 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.
5. 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 end-to-end connectivity in some cases,
for example to provide an end-to-end security association for some
protocols. This is possible, but then has a dependency on routable
address space.
4. Overview
The Autonomic Control Plane is constructed in the following way (for
details, see Section 5):
o An autonomic node creates a virtual routing and forwarding (VRF)
instance, or a similar virtual context.
o 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. Intent can override this default policy.
o For each node in the candidate peer list, it authenticates that
node and negotiates a mutually acceptable channel type.
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o 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.
o Inside the ACP VRF, each node sets up a virtual interface with its
ULA IPv6 address.
o Each node runs a lightweight routing protocol, to announce
reachability of the virtual addresses inside the ACP.
o Non-autonomic NMS systems or controllers have to be manually
connected into the ACP.
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.
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5. Self-Creation of an Autonomic Control Plane
This section describes the steps to set up an Autonomic Control
Plane, and highlights the key properties which make it
"indestructible" against many inadvert changes to the data plane, for
example caused by misconfigurations.
5.1. Preconditions
An autonomic node can be a router, switch, controller, NMS host, or
any other IP device. We assume an autonomic node has:
o A globally unique domain certificate, with which it can
cryptographically assert its membership of the domain. The
document [I-D.ietf-anima-bootstrapping-keyinfra] describes how a
domain certificate can be automatically and securely derived from
a vendor specific Unique Device Identifier (UDI) or IDevID
certificate. (Note the UDI used in this document is NOT the UUID
specified in [RFC4122].)
o An adjacency table, which contains information about adjacent
autonomic nodes, at a minimum: node-ID, IP address, domain,
certificate. An autonomic device maintains this adjacency table
up to date. 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.
5.2. Candidate ACP Neighbor Selection
An autonomic node must determine to which other autonomic nodes in
the adjacency table it should build an ACP connection.
The ACP is by default established exclusively between nodes in the
same domain.
Intent can change this default behaviour. The precise format for
this Intent needs to be defined outside this document. Example
Intent policies are:
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o The ACP should be built between all sub-domains for a given parent
domain. For example: For domain "example.com", nodes of
"example.com", "access.example.com", "core.example.com" and
"city.core.example.com" should all establish one single ACP.
o Two domains should build one single ACP between themselves, for
example "example1.com" should establish the ACP also with nodes
from "example2.com". For this case, the two domains must be able
to validate their trust, typically by cross-signing their
certificate infrastructure.
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.
5.3. Capability Negotiation
Autonomic devices may have different capabilities based on the type
of device, OS version, etc. To establish a trusted secure ACP
channel, devices must first negotiate their mutual capabilities in
the data plane. This allows for the support of different channel
types in the future.
For each node on the candidate ACP neighbor list, capabilities need
to be exchanged. The capability negotiation is based on GRASP
[I-D.ietf-anima-grasp]. The relevant protocol details are defined in
Section 7. This negotiation MUST be secure: The identity of the
other node MUST be validated during capability negotiation, and the
exchange MUST be authenticated.
The first parameter to be negotiated is the ACP Channel type. The
channel types are defined in Section 8. Other parameters may be
added later.
Intent may also influence the capability negotiation. For example,
Intent may require a minimum ACP tunnel security. This is outside
scope for this document.
5.4. Channel Establishment
After authentication and capability negotiation autonomic nodes
establish a secure channel towards the AN neighbors with the above
negotiated parameters.
The channel establishment MUST be authenticated. Whether or not, and
how, a channel is encrypted is part of the capability negotiation,
potentially controlled by Intent.
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In order to be independent of configured link addresses, channels
SHOULD use IPv6 link local addresses between adjacent neighbors
wherever possible. This way, the ACP tunnels are independent of
correct network wide routing.
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 5.7.
If two nodes are connected via several links, the ACP SHOULD be
established on 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.
5.5. 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.
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.
[EDNOTE: Previous versions of this document also discussed an option
where the ACP runs in the data plane without logical separation.
Consensus is to focus only on the separated ACP now, and to remove
the ACP in the data plane from this document. See Appendix B for the
reasons for this decision.]
5.6. 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
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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 5.5.
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.
Once an autonomic node is enrolled in a domain, it automatically
creates a network wide Unique Local Addresses (ULA) in accordance
with [RFC4193] with the following algorithm:
o Prefix FD00::/8, defining locally assigned unique local addresses.
See Section 3.1 of [RFC4193].
o Global ID: an MD5 hash of the domain ID, using the 40 least
significant bits. This results in a pseudo-random global ID, in
accordance with Section 3.2 of [RFC4193].
o Subnet ID and interface ID:
[I-D.behringer-anima-autonomic-addressing] defines how these
fields can be constructed and used.
With this algorithm, all autonomic devices in the same domain 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 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.
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5.7. 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.
The routing protocol inside the ACP should be light weight and highly
scalable to ensure that the ACP does not become a limiting factor in
network scalability. We suggest the use of RPL [RFC6550] as one such
protocol which is light weight and scales well for the control plane
traffic. See Appendix A for more details on the choice of RPL.
6. Workarounds for Non-Autonomic Nodes
6.1. Connecting a Non-Autonomic Controller / NMS system
The Autonomic Control Plane can be used by management systems, such
as controllers or network management system (NMS) hosts (henceforth
called simply "NMS hosts"), to connect to devices through it. For
this, an NMS host must have access to the ACP. By default, the ACP
is a self-protecting overlay network, which only allows access to
trusted systems. Therefore, a traditional, non-autonomic 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. On an adjacent autonomic node with ACP, the
interface with the NMS host can be configured to be part of the ACP.
In this case, the NMS host is with this interface entirely and
exclusively inside the ACP. It would likely require a second
interface for connections between the NMS host and administrators, or
Internet based services. This mode of connecting an NMS host has
security consequences: All systems and processes connected to this
implicitly trusted interface have access to all autonomic nodes on
the entire ACP, without further authentication. Thus, this
connection must be physically controlled.
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The non-autonomic NMS host must be routed in the ACP. This involves
two parts: 1) the NMS host must point default to the AN device for
the ULA prefix used inside the ACP, and 2) the prefix used between AN
node and NMS host must be announced into the ACP, and distributed
there.
The document "Autonomic Network Stable Connectivity"
[I-D.eckert-anima-stable-connectivity] explains in more detail how
the ACP can be integrated in a mixed NOC environment.
6.2. ACP through Non-Autonomic L3 Clouds
Not all devices in a network may be autonomic. If non-autonomic
Layer-2 devices are between autonomic nodes, the communications
described in this document should work, since it is IP based.
However, non-autonomic Layer-3 devices do not forward link local
autonomic messages, and thus break the Autonomic Control Plane.
One workaround is to manually configure IP tunnels between autonomic
nodes across a non-autonomic Layer-3 cloud. The tunnels are
represented on each autonomic node as virtual interfaces, and all
autonomic transactions work across such tunnels.
Such manually configured tunnels are less "indestructible" than an
automatically created ACP based on link local addressing, since they
depend on correct data plane operations, such as routing and
addressing.
7. The Negotiation Protocol
This section describes the negotiation exchange in detail. It is
based on GRASP [I-D.ietf-anima-grasp]. Since at the time of
establishing the ACP channel there is obviously no ACP yet, this
negotiation protocol must run in the data plane. This negotiation
MUST be authenticated, to avoid downgrade attackes, where an attacker
injects bogus negotiation messages demanding a less secure ACP
channel type. The negotiation MAY be encrypted.
[The detailed negotiation flow and mapping into GRASP messages is to
be completed.]
8. The Channel Type
Two adjacent nodes negotiate an ACP channel. This channel MUST be
authenticated and SHOULD be encrypted.
The nodes negotiate a parameter called "ACP channel type". This
document defines a single, MUST implement channel type: GRE with
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IPsec transport mode. See IANA Considerations (Section 13) for the
formal definition of this parameter.
9. 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.
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 5.6).
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10. Self-Protection Properties
As explained in Section 5, the ACP is based on channels being built
between devices which have been previously authenticated based on
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.
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.
11. 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
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cannot connect to an ACP. See Section 6.1 for more details on how to
connect an NMS host into the ACP.
12. 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.
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.
13. IANA Considerations
Section 8 describes an option for the channel negotiation, the
channel type. We request IANA to create a registry for ACP channel
types.
The ACP channel type is a 8-bit unsigned integer. This document only
assigns the first value.
Number | Channel Type | RFC
---------+-----------------------------------+------------
0 | GRE tunnel protected with | this document
| IPsec transport mode |
1-255 | reserved for future channel types |
14. 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, Alex
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Clemm, Yves Hertoghs, Bruno Klauser, Max Pritikin, Ravi Kumar
Vadapalli.
Further input and suggestions were received from: Rene Struik, Brian
Carpenter, Benoit Claise.
15. Change log [RFC Editor: Please remove]
15.1. Initial version
First version of this document:
[I-D.behringer-autonomic-control-plane]
15.2. draft-behringer-anima-autonomic-control-plane-00
Initial version of the anima document; only minor edits.
15.3. 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.
15.4. 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-eckert-anima-stable-
connectivity
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15.5. draft-behringer-anima-autonomic-control-plane-03
o Took out requirement for IPv6 --> that's in the reference doc.
o Added requirement section.
o Changed focus: more focus on autonomic functions, not only virtual
out of band. This goes a bit throughout the document, starting
with a changed abstract and intro.
15.6. draft-ietf-anima-autonomic-control-plane-00
No changes; re-submitted as WG document.
15.7. 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.
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o Updated links, lots of small edits.
16. References
[I-D.behringer-anima-autonomic-addressing]
Behringer, M., "An Autonomic IPv6 Addressing Scheme",
draft-behringer-anima-autonomic-addressing-01 (work in
progress), June 2015.
[I-D.behringer-anima-reference-model]
Behringer, M., Carpenter, B., Eckert, T., Ciavaglia, L.,
Liu, B., Jeff, J., and J. Strassner, "A Reference Model
for Autonomic Networking", draft-behringer-anima-
reference-model-03 (work in progress), June 2015.
[I-D.behringer-autonomic-control-plane]
Behringer, M., Bjarnason, S., BL, B., and T. Eckert, "An
Autonomic Control Plane", draft-behringer-autonomic-
control-plane-00 (work in progress), June 2014.
[I-D.eckert-anima-stable-connectivity]
Eckert, T. and M. Behringer, "Using Autonomic Control
Plane for Stable Connectivity of Network OAM", draft-
eckert-anima-stable-connectivity-01 (work in progress),
March 2015.
[I-D.ietf-anima-bootstrapping-keyinfra]
Pritikin, M., Richardson, M., Behringer, M., and S.
Bjarnason, "Bootstrapping Key Infrastructures", draft-
ietf-anima-bootstrapping-keyinfra-00 (work in progress),
August 2015.
[I-D.ietf-anima-grasp]
Carpenter, B. and B. Liu, "A Generic Autonomic Signaling
Protocol (GRASP)", draft-ietf-anima-grasp-00 (work in
progress), August 2015.
[RFC4122] Leach, P., Mealling, M., and R. Salz, "A Universally
Unique IDentifier (UUID) URN Namespace", RFC 4122,
DOI 10.17487/RFC4122, July 2005,
<http://www.rfc-editor.org/info/rfc4122>.
[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>.
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[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>.
[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>.
Appendix A. Background on the choice of routing protocol
In a pre-standard implementation, the "IPv6 Routing Protocol for Low-
Power and Lossy Networks (RPL, [RFC6550] was chosen. This
Appendix explains the reasoning behind that decision.
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
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directed acyclic graph (DODAG), where the main resource
consumption is at the root of the DODAG. The closer to the edge
of the network, the less state needs to be maintained. This
adapts nicely to the typical network design. Also, all changes
below a common parent node are kept below that parent node.
o Support for unstructured address space: In the Autonomic
Networking Infrastructure, node addresses are identifiers, and may
not be assigned in a topological way. Also, nodes may move
topologically, without changing their address. Therefore, the
routing protocol must support completely unstructured address
space. RPL is specifically made for mobile ad-hoc networks, with
no assumptions on topologically aligned addressing.
o Modularity: To keep the initial implementation small, yet allow
later for more complex methods, it is highly desirable that the
routing protocol has a simple base functionality, but can import
new functional modules if needed. RPL has this property with the
concept of "objective function", which is a plugin to modify
routing 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).
Appendix B. Alternative: An ACP without Separation
Section 5 explains how the ACP is constructed as a virtually
separated overlay network. An alternative ACP design can be achieved
without the VRFs. In this case, the autonomic virtual addresses are
part of the data plane, and subject to routing, filtering, QoS, etc
on the data plane. The secure tunnels are in this case used by
traffic to and from the autonomic address space. They are still
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required to provide the authentication function for all autonomic
packets.
At IETF 93 in Prague, the suggestion was made to not advance with the
data plane ACP, and only continue with the virtually separate ACP.
The reason for this decision is that the contextual separation of the
ACP provides a range of benefits (more robustness, less potential
interactions with user configurations), while it is not much harder
to achieve.
This appendix serves to explain the decision; it will be removed in
the next version of the draft.
Authors' Addresses
Michael H. Behringer (editor)
Cisco Systems
Building D, 45 Allee des Ormes
Mougins 06250
France
Email: mbehring@cisco.com
Steinthor Bjarnason
Cisco Systems
Email: sbjarnas@cisco.com
Balaji BL
Cisco Systems
Email: blbalaji@cisco.com
Toerless Eckert
Cisco Systems
Email: eckert@cisco.com
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