ANIMA WG M. Behringer, Ed.
Internet-Draft
Intended status: Standards Track T. Eckert, Ed.
Expires: January 4, 2018 Huawei
S. Bjarnason
Arbor Networks
July 3, 2017
An Autonomic Control Plane
draft-ietf-anima-autonomic-control-plane-07
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
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This Internet-Draft will expire on January 4, 2018.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Use Cases for an Autonomic Control Plane . . . . . . . . . . 4
2.1. An Infrastructure for Autonomic Functions . . . . . . . . 5
2.2. Secure Bootstrap over an Unconfigured Network . . . . . . 5
2.3. Data Plane Independent Permanent Reachability . . . . . . 5
3. Requirements . . . . . . . . . . . . . . . . . . . . . . . . 6
4. Overview . . . . . . . . . . . . . . . . . . . . . . . . . . 7
5. Self-Creation of an Autonomic Control Plane . . . . . . . . . 8
5.1. Preconditions . . . . . . . . . . . . . . . . . . . . . . 8
5.1.1. Domain Certificate with ACP information . . . . . . . 8
5.1.2. AN Adjacency Table . . . . . . . . . . . . . . . . . 10
5.2. Neighbor discovery . . . . . . . . . . . . . . . . . . . 11
5.2.1. L2 topology considerations . . . . . . . . . . . . . 11
5.2.2. CDP/LLDP/mDNS considerations . . . . . . . . . . . . 12
5.2.3. Discovery with GRASP . . . . . . . . . . . . . . . . 12
5.3. Candidate ACP Neighbor Selection . . . . . . . . . . . . 15
5.4. Channel Selection . . . . . . . . . . . . . . . . . . . . 15
5.5. Candidate ACP Neighbor certificate verification . . . . . 17
5.6. Security Association protocols . . . . . . . . . . . . . 17
5.6.1. ACP via IKEv2 . . . . . . . . . . . . . . . . . . . . 17
5.6.2. ACP via dTLS . . . . . . . . . . . . . . . . . . . . 18
5.6.3. ACP Security Profiles . . . . . . . . . . . . . . . . 19
5.7. GRASP instance details . . . . . . . . . . . . . . . . . 19
5.8. Context Separation . . . . . . . . . . . . . . . . . . . 19
5.9. Addressing inside the ACP . . . . . . . . . . . . . . . . 20
5.9.1. Fundamental Concepts of Autonomic Addressing . . . . 20
5.9.2. The ACP Addressing Base Scheme . . . . . . . . . . . 21
5.9.3. ACP Addressing Sub-Scheme . . . . . . . . . . . . . . 22
5.9.4. Usage of the Zone Field . . . . . . . . . . . . . . . 23
5.9.5. Other ACP Addressing Sub-Schemes . . . . . . . . . . 24
5.10. Routing in the ACP . . . . . . . . . . . . . . . . . . . 24
5.10.1. RPL Profile for the ACP . . . . . . . . . . . . . . 25
5.11. General ACP Considerations . . . . . . . . . . . . . . . 25
6. Workarounds for Non-Autonomic Nodes . . . . . . . . . . . . . 26
6.1. Non-Autonomic Controller / NMS system (ACP connect) . . . 26
6.2. ACP through Non-Autonomic L3 Clouds . . . . . . . . . . . 28
7. Self-Healing Properties . . . . . . . . . . . . . . . . . . . 28
8. Self-Protection Properties . . . . . . . . . . . . . . . . . 29
9. The Administrator View . . . . . . . . . . . . . . . . . . . 30
10. Security Considerations . . . . . . . . . . . . . . . . . . . 30
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11. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 31
12. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 31
13. Change log [RFC Editor: Please remove] . . . . . . . . . . . 31
13.1. Initial version . . . . . . . . . . . . . . . . . . . . 31
13.2. draft-behringer-anima-autonomic-control-plane-00 . . . . 31
13.3. draft-behringer-anima-autonomic-control-plane-01 . . . . 32
13.4. draft-behringer-anima-autonomic-control-plane-02 . . . . 32
13.5. draft-behringer-anima-autonomic-control-plane-03 . . . . 32
13.6. draft-ietf-anima-autonomic-control-plane-00 . . . . . . 32
13.7. draft-ietf-anima-autonomic-control-plane-01 . . . . . . 33
13.8. draft-ietf-anima-autonomic-control-plane-02 . . . . . . 33
13.9. draft-ietf-anima-autonomic-control-plane-03 . . . . . . 34
13.10. draft-ietf-anima-autonomic-control-plane-04 . . . . . . 34
13.11. draft-ietf-anima-autonomic-control-plane-05 . . . . . . 34
13.12. draft-ietf-anima-autonomic-control-plane-06 . . . . . . 35
13.13. draft-ietf-anima-autonomic-control-plane-07 . . . . . . 35
14. References . . . . . . . . . . . . . . . . . . . . . . . . . 37
Appendix A. Background on the choice of routing protocol . . . . 39
Appendix B. Extending ACP channel negotiation (via GRASP) . . . 41
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 43
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
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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.ietf-anima-reference-model]. For example, GRASP
[I-D.ietf-anima-grasp] can run 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.
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 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, and Section 5.6 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. Use Cases for an Autonomic Control Plane
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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.
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.
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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.
3. 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.
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.
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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.
4. Overview
The Autonomic Control Plane is constructed in the following way (for
details, see Section 5):
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 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.
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.
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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.
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 a globally
unique domain certificate (LDevID), as well as an adjacency table.
5.1.1. Domain Certificate with ACP information
To establish an ACP securely, an Autnomic Node MUST have a globally
unique domain certificate (LDevID), with which it can
cryptographically assert its membership in the domain. The document
[I-D.ietf-anima-bootstrapping-keyinfra] (BRSKI) describes how a
domain certificate can automatically and securely be derived from a
vendor specific Unique Device Identifier (UDI) or IDevID certificate.
The domain certificate (LDevID) of an autonomic node MUST contain
ANIMA specific information, specifically the domain name, the address
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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>{+<extensions>}@<domain>
Example:
anima.acp+FDA3:79A6:F6EE:0:200:0:6400:1@example.com
The ACP address MUST be specified in its canonical form, as specified
in [RFC5952], to allow for easy textual comparisons.
The optional <extensions> field is used for future extensions to this
specification. It MUST be ignored unless otherwise specified.
The subjectAlName / rfc822Name encoding of the ACP domain name and
ACP address is used for the following reasons:
o The LDevID assigned by BRSKI should be reuseable for other
purposed beside authentication for ACP.
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 it is beneficial if the
BRSKI enrolled LDevID can also be used for other protocols/
services beside the ACP.
o The elements in the LDevID required for the ACP should therefore
not cause incompatibilities with any pre-existing ASN.1 code
potentially in use in those other pre-existing SW systems.
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 (because it
is in a different VRF than what they expect), or that could cause
security issues.
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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, so that it is easier to
examine/use the encoded "ACP information".
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
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, 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.
In the BRSKI bootstrap process in an ANIMA network, 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 ANIMA network MUST not change this,
and create the respective subjectAltName / rfc822Name in the
certificate.
ANIMA nodes can therefore find ACP address and domain using this
field in the domain certificate, both for themselves, as well as for
other nodes.
See section 4.2.1.6 of [RFC5280] for details on the subjectAltName
field.
5.1.2. 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.
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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. Neighbor discovery
5.2.1. L2 topology considerations
ANrtr1 ------ ANswitch1 --- ANswitch2 ------- ANrtr2
.../ \ \ ...
ANrtrM ------ \ ------- ANrtrN
ANswitchM ...
Figure 2
Consider a large L2 LAN with ANrtr1...ANrtrN connected via some
topology of L2 switches (eg: in a large enterprise campus or IoT
environment using large L2 LANs). 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
challenges. The number of security associations of the secure
channel protocols will not scale arbitrarily, especially when they
leverage platform accelerated encryption/decryption. Likewise, any
other ACP operations 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
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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
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.
5.2.2. CDP/LLDP/mDNS considerations
LLDP (and Cisco's 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-ANIMA switches.
mDNS operates at the subnet level, and is also used on L2 switches.
The authors of this document are not aware of mDNS implementation
that terminate their messages on L2 ports instead of the subnet
level. If mDNS was used as the ACP discovery mechanism on an ACP
capable L2 switch, then this would be necessary to implement. It is
likely that termination of mDNS messages could only be applied to all
mDNS messages from a port, which would then make it necessary to
software forward any non-ACP related mDNS messages to maintain prior
non-ACP mDNS functionality. With low performance of software
forwarding in many L2 switches, this could easily make the ACP
unsupportable on such L2 switches.
5.2.3. Discovery with GRASP
Because of the above considerations, 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] These
can easily be set up to match the aforementioned requirements without
affecting other uses of GRASP. Note that each such DULL instance of
GRASP is also used for the discovery of a bootstrap proxy when the
device is not yet enrolled into the autonomic domain. Because the
discover of ACP neighbors only happens after the device is enrolled
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into the autonomic domain, it never needs to discover 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:
[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.
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.
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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 the 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 disstinction 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 packet.
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.
As explained above, in an ACP enabled L2 switch, each of these GRASP
instances would actually need to be per-L2-port. 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 5.1.2 which then drives the further building of the ACP to
that neighbor.
For example, 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. This is easily
achieved by extracting native GRASP multicast messages by their MAC
multicast destination address. None of the other type of GRASP
instances (eg: as used inside the ACP) use GRASP messages that would
be affected by such extraction, because all other GRASP messages have
encrypted encapsulations.
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5.3. 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.
Intent can change this default behaviour. Since Intent is
transported over the ACP, the first ACP connection a node establishes
is always following the default behaviour. The precise format for
this Intent needs to be defined outside this document. Example
Intent policies which need to be supported include:
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.
5.4. 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 negotiationg
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.
5.5. 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 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.
o The peers certificate is valid according to the CRL or OCSP method
indicated in the devices certificate. If the peers certificate
fails any of these checks, the connection attempt is aborted and
an error logged (with throttling).
This document does not mandate specific support for CRL or OCSP
options. If CRL or OCSP URLs are specified in the devices
certificate then the device SHOULD connect to the URL via the ACP if
it has an IPv6 address that is reachable via the ACP. Better
mechanisms to locate CRL or OCSP server(s), for example via GRASP are
subject to future documents.
5.6. Security Association protocols
The following sections define the security association protocols that
we consider to be important and feasible to specify in this document:
5.6.1. 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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5.6.1.1. 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).
5.6.1.2. 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].
5.6.2. 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 use AES256 encryption.
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
association mechanisms such as re-keying are used as they would be
for any transport application relying solely on dTLS.
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5.6.3. ACP Security Profiles
A baseline autonomic device MUST support IPsec. A constrained
autonomic device MUST support dTLS. Autonomic edge device connecting
constrained areas with baseline areas MUST therefore support IPsec
and dTLS.
The MTU for ACP secure channels must be derived locally from the
underlying link MTU minus the security encapsulation overhead. Given
how ACP channels are built across layer2 connections only, the
probability for MTU mismatch is low. For additional reliability,
applications to be runa cross the ACP should only assume to have
minimum MTU available (1280).
Autonomic devices need to specify in documentation the set of secure
ACP mechanisms they suppport.
5.7. GRASP instance details
Received GRASP packets are assigned to an instance of GRASP by the
context they are received on:
o GRASP packets received on an ACP (virtual) interfaces are assigned
to the ACP instance of GRASP
o GRASP/UDP packets received on L2 interfaces/ports where the device
is willing to run ACP are assigned to a DULL instance of GRASP for
that interface/port.
5.8. 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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5.9. 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 5.8. This address may be used
also in other virtual contexts.
With the algorithm introduced here, 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 7 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.
5.9.1. 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.
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 a
routable address; 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.
5.9.2. The ACP Addressing Base Scheme
The Base ULA addressing scheme for autonomic nodes has the following
format:
8 40 3 77
+--+--------------+------+------------------------------------------+
|FD| hash(domain) | Type | (sub-scheme) |
+--+--------------+------+------------------------------------------+
Figure 3: ACP Addressing Base Scheme
The first 48 bits follow the ULA scheme, as defined in [RFC4193], to
which a type field is added:
o "FD" identifies a locally defined ULA address.
o The ULA "global ID" is set here to be a hash of the domain name,
which results in a pseudo-random 40 bit value. It is calculated
as the first 40 bits of the SHA256 hash of the domain name, in the
example "example.com".
o To allow for extensibility, the fact that the ULA "global ID" is
such a hash MUST NOT be assumed by any autonomic device during
normal operations but only by registrars during the creation of a
response to the CSR Attribute request, eg: when the certificate is
created in which the address is inserted via the ACP information
attribute.
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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.
5.9.3. ACP Addressing Sub-Scheme
The sub-scheme defined here is defined by the Type value 0 (zero) in
the base scheme.
51 13 63 1
+------------------------+---------+----------------------------+---+
| (base scheme) | Zone-ID | Device-ID | V |
+------------------------+---------+----------------------------+---+
Figure 4: ACP Addressing Sub-Scheme
The fields are defined as follows: [Editor's note: The lengths of the
fields is for discussion.]
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 5.9.4 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.
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
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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 5.9.4 for a description of the zone bits.
This addressing sub-scheme allows the direct addressing of specific
virtual containers / VMs on an autonomic node. An increasing number
of hardware platforms have a distributed architecture, with a base OS
for the node itself, and the support for hardware blades with
potentially different OSs. The VMs on the blades could be considered
as separate autonomic nodes, in which case it would make sense to be
able to address them directly. Autonomic Service Agents (ASAs) could
be instantiated in either the base OS, or one of the VMs on a blade.
This addressing scheme allows for the easy separation of the hardware
context.
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.
[EDNOTE: various suggestions from mcr in his mail from 30 Nov 2016 to
be considered (https://mailarchive.ietf.org/arch/msg/anima/
nZpEphrTqDCBdzsKMpaIn2gsIzI).]
5.9.4. 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: Another way to introduce hierarchy is to use sub-domains in the
naming scheme. The node names "node17.subdomainA.example.com" and
"node4.subdomainB.example.com" would automatically lead to different
ULA prefixes, which can be used to introduce a routing hierarchy in
the network, assuming that the subdomains are aligned with routing
areas. Because the domain name in the ACP information field of the
certificate is used to authenticate an ACP peers certificate, care
must be taken when using such an approach though: To allow for
devices in separate subdomains to have mutually permitted
certificates, the domain part of the ACP information can not carry
the subdomain. Instead it shuold be carried as an extension to the
address part. This part will be ignored and instead only the address
field using the different subdomain hash based ULA prefix will be
used. Example:
anima.acp+FDA3:79A6:F6EE:0:200:0:6400:1+sub:subdomainA@example.com
5.9.5. 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.
5.10. 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]) with the
following profile. See Appendix A for more details on the choice of
RPL.
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5.10.1. RPL Profile for the ACP
o 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.
o Objective Function (OF): Use OF0 [RFC6552]. No use of metric
containers, Default RPLInstanceID = 0.
* stretch_rank: none provided ("not stretched").
* rank_factor: Derived from link speed: <= 100Mbps:
LOW_SPEED_FACTOR(5), else HIGH_SPEED_FACTOR(1)
o Trickle: Not used; Data Path Validation: Not used.
o Proactive, aggressive DAO state maintenance:
* Use K-flag in unsolicited DAO indicating change from previous
information (to require DAO-ACK).
* Retry such DAO DAO-RETRIES(3) times with DAO-
ACK_TIME_OUT(256ms) in between.
o Administrative Preference ([RFC6552], 3.2.6 - to become root):
Indicated in DODAGPreference field of DIO message.
* Explicit configured "root": 0b100
* Registrar (Default): 0b011
* AN-connect (non registrar): 0b010
* Default: 0b001.
The RPL root can create additional RPL instances with other OF and
metrics as desired, eg: via intent.
5.11. General ACP Considerations
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
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decrypts incoming traffic from the ACP, and encrypts outgoing traffic
to its neighbors in the ACP. Routing is discussed in Section 5.10.
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.
6. Workarounds for Non-Autonomic Nodes
6.1. 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
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).
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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 5: 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.
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.
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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.
Future work should envisage an option where the edge device 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.
7. 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
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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 5.9).
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).
8. Self-Protection Properties
As explained in Section 5, 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 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. 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 6.1 for more details on how to
connect an NMS host into the ACP.
10. 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
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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, (s)he 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.
11. IANA Considerations
12. 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.
13. Change log [RFC Editor: Please remove]
13.1. Initial version
First version of this document: draft-behringer-autonomic-control-
plane
13.2. draft-behringer-anima-autonomic-control-plane-00
Initial version of the anima document; only minor edits.
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13.3. 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.
13.4. 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
13.5. 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.
13.6. draft-ietf-anima-autonomic-control-plane-00
No changes; re-submitted as WG document.
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13.7. 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.
13.8. 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.
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13.9. 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 5.1.
o Editorial changes, updated draft references, etc.
13.10. 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).
13.11. 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.
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o Section 5.9.1 (addressing): State that addresses in the ACP are
permanent, and do not support temporary addresses as defined in
RFC4941.
o Modified Section 5.2.3 to point to the GRASP objective defined in
[I-D.carpenter-anima-ani-objectives]. (and added that reference)
o Section 5.9.2: 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 6.1 the ACP Connect port, and defined that
term "ACP Connect".
o Section 6.2: Added some thoughts (from mcr) on how traversing a L3
cloud could be automated.
o Added a CRL check in Section 5.6.
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).
13.12. 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.
13.13. 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.
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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" 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 of the certificate
instead of the OU in the certificate. Also renewed the text
pointing out that the ACP information 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 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,
because that is used for mutual authentication of the certificate.
Also clarified that only the register(s) SHOULD/MUST use that the
ACP address was generated from the domain name - so that we can
easier extend change this in extensions.
o Took the text for the GRASP discovery of ACP neighbors from Brians
grasp-ani-objectives draft. Alas, that draft was behind the
latest GRASP draft, so i had to overhaul. The mayor change is to
describe in the ACP draft the whole format of the M_FLOOD message
(and not only the actual objective). This should make it a lot
easier to read (without having to go back and forth to the GRASP
RFC/draft). It was also necessary because the locator in the
M_FLOOD messages has an important role and its not coded inside
the objective. The specification of how to format the M_FLOOD
message shuold now be complete, the text may be some duplicate
with the DULL specificateion in GRASP, but no contradiction.
o One of the main outcomes of reworking the GRASP section was the
notion that GRASP announces both the candidate peers IPv6 link
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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. References
[I-D.carpenter-anima-ani-objectives]
Carpenter, B. and B. Liu, "Technical Objective Formats for
the Autonomic Network Infrastructure", draft-carpenter-
anima-ani-objectives-02 (work in progress), June 2017.
[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-06 (work in progress), May 2017.
[I-D.ietf-anima-grasp]
Bormann, C., Carpenter, B., and B. Liu, "A Generic
Autonomic Signaling Protocol (GRASP)", draft-ietf-anima-
grasp-14 (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.
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[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-02 (work in progress), February
2017.
[I-D.richardson-anima-6join-discovery]
Richardson, M., "GRASP discovery of Registrar by Join
Assistant", draft-richardson-anima-6join-discovery-00
(work in progress), October 2016.
[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>.
[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>.
[RFC5082] Gill, V., Heasley, J., Meyer, D., Savola, P., Ed., and C.
Pignataro, "The Generalized TTL Security Mechanism
(GTSM)", RFC 5082, DOI 10.17487/RFC5082, October 2007,
<http://www.rfc-editor.org/info/rfc5082>.
[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>.
[RFC5952] Kawamura, S. and M. Kawashima, "A Recommendation for IPv6
Address Text Representation", RFC 5952,
DOI 10.17487/RFC5952, August 2010,
<http://www.rfc-editor.org/info/rfc5952>.
[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>.
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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>.
[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>.
[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>.
[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>.
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:
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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
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.
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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. Extending ACP channel negotiation (via GRASP)
The mechanism described in the normative part of this document to
support multiple different ACP secure channel protocols without a
single network wide MTI protocol is important to allow extending
secure ACP channel protocols beyond what is specified in this
document, but it will run into problem if it would be used for
multiple protocols:
The need to potentially have multiple of these security associations
even temporarily run in parallel to determine which of them works
best does not support the most lightweight implementation options.
The simple policy of letting one side (Alice) decide what is best may
not lead to the mutual best result.
The two limitations can easier be solved if the solution was more
modular and as few as possible initial secure channel negotiation
protocols would be used, and these protocols would then take on the
responsibility to support more flexible objectives to negotiate the
mutually preferred ACP security channel protocol.
IKEv2 is the IETF standard protocol to negotiate network security
associations. It is meant to be extensible, but it is unclear
whether it would be feasible to extend IKEv2 to support possible
future requirements for ACP secure channel negotiation:
Consider the simple case where the use of native IPsec vs. IPsec via
GRE is to be negotiated and the objective is the maximum throughput.
Both sides would indicate some agreed upon performance metric and the
preferred encapsulation is the one with the higher performance of the
slower side. IKEv2 does not support negotiation with this objective.
Consider dTLS and some form of 802.1AE (MacSEC) are to be added as
negotiation options - and the performance objective should work
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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
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 is
highly reduced.
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.
Behringer, et al. Expires January 4, 2018 [Page 42]
Internet-Draft An Autonomic Control Plane July 2017
Authors' Addresses
Michael H. Behringer (editor)
Email: mchael.h.behringer@gmail.com
Toerless Eckert (editor)
Futurewei Technologies Inc.
2330 Central Expy
Santa Clara 95050
USA
Email: tte+ietf@cs.fau.de
Steinthor Bjarnason
Arbor Networks
2727 South State Street, Suite 200
Ann Arbor MI 48104
United States
Email: sbjarnason@arbor.net
Behringer, et al. Expires January 4, 2018 [Page 43]
