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Versions: 00 01 02 draft-ietf-anima-stable-connectivity

ANIMA                                                          T. Eckert
Internet-Draft                                              M. Behringer
Intended status: Informational                                     Cisco
Expires: April 21, 2016                                 October 19, 2015


  Using Autonomic Control Plane for Stable Connectivity of Network OAM
               draft-eckert-anima-stable-connectivity-02

Abstract

   OAM (Operations, Administration and Management) processes for data
   networks are often subject to the problem of circular dependencies
   when relying on network connectivity of the network to be managed for
   the OAM operations itself.  Provisioning during device/network bring
   up tends to be far less easy to automate than service provisioning
   later on, changes in core network functions impacting reachability
   can not be automated either because of ongoing connectivity
   requirements for the OAM equipment itself, and widely used OAM
   protocols are not secure enough to be carried across the network
   without security concerns.

   This document describes how to integrate OAM processes with the
   autonomic control plane (ACP) in Autonomic Networks (AN). to provide
   stable and secure connectivity for those OAM processes.

Status of This Memo

   This Internet-Draft is submitted in full conformance with the
   provisions of BCP 78 and BCP 79.

   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF).  Note that other groups may also distribute
   working documents as Internet-Drafts.  The list of current Internet-
   Drafts is at http://datatracker.ietf.org/drafts/current/.

   Internet-Drafts are draft documents valid for a maximum of six months
   and may be updated, replaced, or obsoleted by other documents at any
   time.  It is inappropriate to use Internet-Drafts as reference
   material or to cite them other than as "work in progress."

   This Internet-Draft will expire on April 21, 2016.

Copyright Notice

   Copyright (c) 2015 IETF Trust and the persons identified as the
   document authors.  All rights reserved.




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   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents
   (http://trustee.ietf.org/license-info) in effect on the date of
   publication of this document.  Please review these documents
   carefully, as they describe your rights and restrictions with respect
   to this document.  Code Components extracted from this document must
   include Simplified BSD License text as described in Section 4.e of
   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
     1.1.  Self dependent OAM connectivity . . . . . . . . . . . . .   2
     1.2.  Data Communication Networks (DCNs)  . . . . . . . . . . .   3
     1.3.  Leveraging the ACP  . . . . . . . . . . . . . . . . . . .   3
   2.  Solutions . . . . . . . . . . . . . . . . . . . . . . . . . .   4
     2.1.  Stable connectivity for centralized OAM operations  . . .   4
       2.1.1.  Simple connectivity for non-autonomic NOC application
               devices . . . . . . . . . . . . . . . . . . . . . . .   4
       2.1.2.  Limitations and enhancement overview  . . . . . . . .   5
       2.1.3.  Simultaneous ACP and data plane connectivity  . . . .   6
       2.1.4.  IPv4 only NOC application devices . . . . . . . . . .   7
       2.1.5.  Path selection policies . . . . . . . . . . . . . . .   8
       2.1.6.  Autonomic NOC device/applications . . . . . . . . . .  10
       2.1.7.  Encryption of data-plane connections  . . . . . . . .  10
       2.1.8.  Long term direction of the solution . . . . . . . . .  11
     2.2.  Stable connectivity for distributed network/OAM functions  12
   3.  Security Considerations . . . . . . . . . . . . . . . . . . .  12
   4.  No IPv4 for ACP . . . . . . . . . . . . . . . . . . . . . . .  14
   5.  Further considerations  . . . . . . . . . . . . . . . . . . .  14
   6.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  14
   7.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .  14
   8.  Change log [RFC Editor: Please remove]  . . . . . . . . . . .  15
   9.  References  . . . . . . . . . . . . . . . . . . . . . . . . .  15
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  16

1.  Introduction

1.1.  Self dependent OAM connectivity

   OAM (Operations, Administration and Management) processes for data
   networks are often subject to the problem of circular dependencies
   when relying on network connectivity of the network to be managed for
   the OAM operations itself:

   The ability to perform OAM operations on a network device requires
   first the execution of OAM procedures necessary to create network



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   connectivity to that device in all intervening devices.  This
   typically leads to sequential, 'expanding ring configuration' from a
   NOC.  It also leads to tight dependencies between provisioning tools
   and security enrollment of devices.  Any process that wants to enroll
   multiple devices along a newly deployed network topology needs to
   tightly interlock with the provisioning process that creates
   connectivity before the enrollment can move on to the next device.

   When performing change operations on a network, it likewise is
   necessary to understand at any step of that process that there is no
   interruption of connectivity that could lead to removal of
   connectivity to remote devices.  This includes especially change
   provisioning of routing, security and addressing policies in the
   network that often occur through mergers and acquisitions, the
   introduction of IPv6 or other mayor re-hauls in the infrastructure
   design.

   All this circular dependencies make OAM processes complex and
   potentially fragile.  When automation is being used, for example
   through provisioning systems or network controllers, this complexity
   extends into that automation software.

1.2.  Data Communication Networks (DCNs)

   In the late 1990'th and early 2000, IP networks became the method of
   choice to build separate OAM networks for the communications
   infrastructure in service providers.  This concept was standardized
   in G.7712/Y.1703 and called "Data Communications Networks" (DCN).
   These where (and still are) physically separate IP(/MPLS) networks
   that provide access to OAM interfaces of all equipment that had to be
   managed, from PSTN switches over optical equipment to nowadays
   ethernet and IP/MPLS production network equipment.

   Such DCN provide stable connectivity not subject to aforementioned
   problems because they are separate network entirely, so change
   configuration of the production IP network is done via the DCN but
   never affects the DCN configuration.  Of course, this approach comes
   at a cost of buying and operating a separate network and this cost is
   not feasible for many networks, most notably smaller service
   providers, most enterprises and typical IoT networks.

1.3.  Leveraging the ACP

   One goal of the Autonomic Networks Autonomic Control plane (ACP) is
   to provide similar stable connectivity as a DCN, but without having
   to build a separate DCN.  It is clear that such 'in-band' approach
   can never achieve fully the same level of separation, but the goal is
   to get as close to it as possible.



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   This solution approach has several aspects.  One aspect is designing
   the implementation of the ACP in network devices to make it actually
   perform without interruption by changes in what we will call in this
   document the "data-plane", aka: the operator or controller configured
   services planes of the network equipment.  This aspect is not
   currently covered in this document.

   Another aspect is how to leverage the stable IPv6 connectivity
   provided by the ACP to build actual OAM solutions.  This is the
   current scope of this document.

2.  Solutions

2.1.  Stable connectivity for centralized OAM operations

   In the most common case, OAM operations will be performed by one or
   more applications running on a variety of centralized NOC systems
   that communicate with network devices.  We describe differently
   advanced approaches to leverage the ACP for stable connectivity
   leveraging the ACP.  The descriptions will show that there is a wide
   range of options, some of which are simple, some more complex.

   Most easily we think there are three stages of interest:

   o  There are simple options described first that we consider to be
      good starting points to operationalize the use of the ACP for
      stable connectivity.

   o  The are more advanced intermediate options that try to establish
      backward compatibility with existing deployed approached such as
      leveraging NAT.  Selection and deployment of these approaches
      needs to be carefully vetted to ensure that they provide positive
      RoI.  This very much depends on the operational processes of the
      network operator.

   o  It seems clearly feasible to build towards a long-term
      configuration that provides all the desired operational, zero
      touch and security benefits of an autonomic network, but a range
      of details for this still have to be worked out.

2.1.1.  Simple connectivity for non-autonomic NOC application devices

   In the most simple deployment case, the ACP extends all the way into
   the NOC via a network device that is set up to provide access into
   the ACP natively to non-autonomic devices.  It acts as the default-
   router to those hosts and provides them with only IPv6 connectivity
   into the ACP - but no IPv4 connectivity.  NOC devices with this setup




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   need to support IPv6 but require no other modifications to leverage
   the ACP.

   This setup is sufficient for troubleshooting OAM operations such as
   SSH into network devices, NMS that perform SNMP read operations for
   status checking, for software downloads into autonomic devices and so
   on.  In conjunction with otherwise unmodified OAM operations via
   separate NOC devices/applications it can provide a good subset of the
   interesting stable connectivity goals from the ACP.

   Because the ACP provides 'only' for IPv6 connectivity, and because
   the addressing provided by the ACP does not include any addressing
   structure that operations in a NOC often relies on to recognize where
   devices are on the network, it is likely highly desirable to set up
   DNS so that the ACP IPv6 addresses of autonomic devices are known via
   domain names with logical names.  For example, if DNS in the network
   was set up with names for network devices as
   devicename.noc.example.com, then the ACP address of that device could
   be mapped to devicename-acp.noc.exmaple.com.

2.1.2.  Limitations and enhancement overview

   This most simple type of attachment of NOC applications to the ACP
   suffers from a range of limitations:

   1.  NOC applications can not directly probe whether the desired so
       called 'data-plane' network connectivity works because they do
       not directly have access to it.  This problem is not dissimilar
       to probing connectivity for other services (such as VPN services)
       that they do not have direct access to, so the NOC may already
       employ appropriate mechanisms to deal with this issue (probing
       proxies).

   2.  NOC applications need to support IPv6 which often is still not
       the case in many enterprise networks.

   3.  Performance of the ACP will be limited versus normal 'data-plane'
       connectivity.  The setup of the ACP will often support only non-
       hardware accelerated forwarding.  Running a large amount of
       traffic through the ACP, especially for tasks where it is not
       necessary will reduce its performance/effectiveness for those
       operations where it is necessary or highly desirable.

   4.  Security of the ACP is reduced by exposing the ACP natively (and
       unprotected) into a LAN In the NOC where the NOC devices are
       attached to it.





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   These four problems can be tackled independently of each other by
   solution improvements.  Combining these solutions improvements
   together ultimately leads towards the the target long term solution.

2.1.3.  Simultaneous ACP and data plane connectivity

   Simultaneous connectivity to both ACP and data-plane can be achieved
   in a variety of ways.  If the data-plane is only IPv4, then any
   method for dual-stack attachment of the NOC device/application will
   suffice: IPv6 connectivity from the NOC provides access via the ACP,
   IPv4 will provide access via the data-plane.  If as explained above
   in the most simple case, an autonomic device supports native
   attachment to the ACP, and the existing NOC setup is IPv4 only, then
   it could be sufficient to simply attach the ACP device(s) as the IPv6
   default-router to the NOC LANs and keep the existing IPv4 default
   router setup unchanged.

   If the data-plane of the network is also supporting IPv6, then the
   NOC devices that need access to the ACP should have a dual-homing
   IPv6 setup.  One option is to make the NOC devices multi-homed with
   one logical or physical IPv6 interface connecting to the data-plane,
   and another into the ACP.  The LAN that provides access to the ACP
   should then be given an IPv6 prefix that shares a common prefix with
   the IPv6 ULA of the ACP so that the standard IPv6 interface selection
   rules on the NOC host would result in the desired automatic selection
   of the right interface: towards the ACP facing interface for
   connections to ACP addresses, and towards the data-plane interface
   for anything else.  If this can not be achieved automatically, then
   it needs to be done via simple IPv6 static routes in the NOC host.

   Providing two virtual (eg: dot1q subnet) connections into NOC hosts
   may be seen as undesired complexity.  In that case the routing policy
   to provide access to both ACP and data-plane via IPv6 needs to happen
   in the NOC network itself: The NOC application device gets a single
   attachment interface but still with the same two IPv6 addresses as in
   before - one for use towards the ACP, one towards the data-plane.
   The first-hop router connecting to the NOC application device would
   then have separate interfaces: one towards the data-plane, one
   towards the ACP.  Routing of traffic from NOC application hosts would
   then have to be based on the source IPv6 address of the host: Traffic
   from the address designated for ACP use would get routed towards the
   ACP, traffic from the designated data-plane address towards the data-
   plane.

   In the most simple case, we get the following topology: Existing NOC
   application devices connect via an existing NOClan and existing first
   hop Rtr1 to the data-plane.  Rtr1 is not made autonomic, but instead
   the edge router of the Autonomic network ANrtr is attached via a



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   separate interface to Rtr1 and ANrtr provides access to the ACP via
   ACPaccessLan.  Rtr1 is configured with the above described IPv6
   source routing policies and the NOC-app-devices are given the
   secondary IPv6 address for connectivity into the ACP.

                                     --... (data-plane)
 NOC-app-device(s) -- NOClan -- Rtr1
                                     --- ACPaccessLan -- ANrtr ... (ACP)


                                 Figure 1

   If Rtr1 was to be upgraded to also implement Autonomic Networking and
   the ACP, the picture would change as follows:


                                                ---- ... (data-plane)
       NOC-app-device(s) ---- NOClan --- ANrtr1
                                         .  .   ---- ... (ACP)
                                         \-/
                                         (ACP to data-plane loopback)


                                 Figure 2

   In this case, ANrtr1 would have to implement some more advanced
   routing such as cross-VRF routing because the data-plane and ACP are
   most likely run via separate VRFs.  A simple short-term workaround
   could be a physical external loopback cable into two ports of ANrtr1
   to connect the data-plane and ACP VRF as shown in the picture.

2.1.4.  IPv4 only NOC application devices

   With the ACP being intentionally IPv6 only, attachment of IPv4 only
   NOC application devices to the ACP requires the use of IPv4 to IPv6
   NAT.  This NAT setup could for example be done in Rt1r1 in above
   picture to also support IPv4 only NOC application devices connected
   to NOClan.

   To support connections initiated from IPv4 only NOC applications
   towards the ACP of network devices, it is necessary to create a
   static mapping of ACP IPv6 addresses into an unused IPv4 address
   space and dynamic or static mapping of the IPv4 NOC application
   device address (prefix) into IPv6 routed in the ACP.  The main issue
   in this setup is the mapping of all ACP IPv6 addresses to IPv4.
   Without further network intelligence, this needs to be a 1:1 address
   mapping because the prefix used for ACP IPv6 addresses is too long to
   be mapped directly into IPv4 on a prefix basis.



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   One could implement in router software dynamic mappings by leveraging
   DNS, but it seems highly undesirable to implement such complex
   technologies for something that ultimately is a temporary problem
   (IPv4 only NOC application devices).  With today's operational
   directions it is likely more preferable to automate the setup of 1:1
   NAT mappings in that NAT router as part of the automation process of
   network device enrollment into the ACP.

   The ACP can also be used for connections initiated by the network
   device into the NOC application devices.  For example syslog from
   autonomic devices.  In this case, static mappings of the NOC
   application devices IPv4 addresses are required.  This can easily be
   done with a static prefix mapping into IPv6.

   Overall, the use of NAT is especially subject to the RoI
   considerations, but the methods described here may not be too
   different from the same problems encountered totally independent of
   AN/ACP when some parts of the network are to introduce IPv6 but NOC
   application devices are not (yet) upgradeable.

2.1.5.  Path selection policies

   As mentioned above, the ACP is not expected to have high performance
   because its primary goal is connectivity and security, and for
   existing networ device platforms this often means that it is a lot
   more effort to implement that additional connectivity with hardware
   acceleration than without - especially because of the desire to
   support full encryption across the ACP to achieve the desired
   security.

   Some of these issues may go away in the future with further adoption
   of the ACP and network device designs that better tender to the needs
   of a separate OAM plane, but it is wise to plan for even long-term
   designs of the solution that does NOT depend on high-performance of
   the ACP.  This is opposite to the expectation that future NOC
   application devices will have IPv6, so that any considerations for
   IPv4/NAT in this solution are temporary.

   To solve the expected performance limitations of the ACP, we do
   expect to have the above describe dual-connectivity via both ACP and
   data-plane between NOC application devices and AN devices with ACP.
   The ACP connectivity is expected to always be there (as soon as a
   device is enrolled), but the data-plane connectivity is only present
   under normal operations but will not be present during eg: early
   stages of device bootstrap, failures, provisioning mistakes or during
   network configuration changes.





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   The desired policy is therefore as follows: In the absence of further
   security considerations (see below), traffic between NOC application
   and AN devices should prefer data-plane connectivity and resort only
   to using the ACP when necessary, unless it is an operation known to
   be so much tied to the cases where the ACP is necessary that it makes
   no sense to try using the data plane.  An example here is of course
   the SSH connection from the NOC into a network device to troubleshoot
   network connectivity.  This could easily always rely on the ACP.
   Likewise, if a NOC application is known to transmit large amounts of
   data, and it uses the ACP, then its performance need to be controlled
   so that it will not overload the ACP performance.  Typical examples
   of this are software downloads.

   There is a wide range of methods to build up these policies.  We
   describe a few:

   DNS can be used to set up names for the same network devices but with
   different addresses assigned: One name (name.noc.example.com) with
   only the data-plane address(es) (IPv4 and/or IPv6) to be used for
   probing connectivity or performing routine software downloads that
   may stall/fail when there are connectivity issues.  One name (name-
   acp.noc.example.com) with only the ACP reachable address of the
   device for troubleshooting and probing/discovery that is desired to
   always only use the ACP.  One name with data plane and ACP addresses
   (name-both.noc.example.com).

   Traffic policing and/or shaping of at the ACP edge in the NOC can be
   used to throttle applications such as software download into the ACP.

   MP-TCP is a very attractive candidate to automate the use of both
   data-plane and ACP and minimize or fully avoid the need for the above
   mentioned logical names to pre-set the desired connectivity (data-
   plane-only, ACP only, both).  For example, a set-up for non MP-TCP
   aware applications would be as follows:

   DNS naming is set up to provide the ACP IPv6 address of network
   devices.  Unbeknownst to the application, MP-TCP is used.  MP-TCP
   mutually discovers between the NOC and network device the data-plane
   address and caries all traffic across it when that MP-TCP sub-flow
   across the data-plane can be built.

   In the Autonomic network devices where data-plane and ACP are in
   separate VRFs, it is clear that this type of MP-TCP sub-flow creation
   across different VRFs is new/added functionality.  Likewise the
   policies of preferring a particular address (NOC-device) or VRF (AN
   device) for the traffic is potentially also a policy not provided as
   a standard.




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2.1.6.  Autonomic NOC device/applications

   Setting up connectivity between the NOC and autonomic devices when
   the NOC device itself is non-autonomic is as mentioned in the
   beginning a security issue.  It also results as shown in the previous
   paragraphs in a range of connectivity considerations, some of which
   may be quite undesirable or complex to operationalize.

   Making NOC application devices autonomic and having them participate
   in the ACP is therefore not only a highly desirable solution to the
   security issues, but can also provide a likely easier
   operationalization of the ACP because it minimizes NOC-special edge
   considerations - the ACP is simply built all the way automatically,
   even inside the NOC and only authorized and authenticate NOC devices/
   applications will have access to it.

   Supporting the ACP all the way into an application device requires
   implementing the following aspects in it: AN bootstrap/enrollment
   mechanisms, the secure channel for the ACP and at least the host side
   of IPv6 routing setup for the ACP.  Minimally this could all be
   implemented as an application and be made available to the host OS
   via eg: a tap driver to make the ACP show up as another IPv6 enabled
   interface.

   Having said this: If the structure of NOC applications is transformed
   through virtualization anyhow, then it may be considered equally
   secure and appropriate to construct a (physical) NOC application
   system by combining a virtual AN/ACP enabled router with non-AN/ACP
   enabled NOC-application VMs via a hypervisor, leveraging the
   configuration options described in the previous sections but jut
   virtualizing them.

2.1.7.  Encryption of data-plane connections

   When combining ACP and data-plane connectivity for availability and
   performance reasons, this too has an impact on security: When using
   the ACP, the traffic will be mostly encryption protected, especially
   when considering the above described use of AN application devices.
   If instead the data-plane is used, then this is not the case anymore
   unless it is done by the application.

   The most simple solution for this problem exists when using AN NOC
   application devices, because in that case the communicating AN NOC
   application and the AN network device have certificates through the
   AN enrollment process that they can mutually trust (same AN domain).
   In result, data-plane connectivity that does support this can simply
   leverage TLS/dTLS with mutual AN-domain certificate authentication -
   and does not incur new key management.



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   If this automatic security benefit is seen as most important, but a
   "full" ACP stack into the NOC application device is unfeasible, then
   it would still be possible to design a stripped down version of AN
   functionality for such NOC hosts that only provides enrollment of the
   NOC host into the AN domain to the extend that the host receives an
   AN domain certificate, but without directly participating in the ACP
   afterwards.  Instead, the host would just leverage TLS/dTLS using its
   AN certificate via the data-plane with AN network devices as well as
   indirectly via the ACP with the above mentioned in-NOC network edge
   connectivity into the ACP.

   When using the ACP itself, TLS/dTLS for the transport layer between
   NOC application and network device is somewhat of a double price to
   pay (ACP also encrypts) and could potentially be optimized away, but
   given the assumed lower performance of the ACP, it seems that this is
   an unnecessary optimization.

2.1.8.  Long term direction of the solution

   If we consider what potentially could be the most lightweight and
   autonomic long term solution based on the technologies described
   above, we see the following direction:

   1.  NOC applications should at least support IPv6.  IPv4/IPv6 NAT in
       the network to enable use of ACP is long term undesirable.
       Having IPv4 only applications automatically leverage IPv6
       connectivity via host-stack options is likely non-feasible (NOTE:
       this has still to be vetted more).

   2.  Build the ACP as a lightweight application for NOC application
       devices so ACP extends all the way into the actual NOC
       application devices.

   3.  Leverage and as necessary enhance MP-TCP with automatic dual-
       connectivity: If the MP-TCP unaware application is using ACP
       connectivity, the policies used should add sub-flow(s) via the
       data-plane and prefer them.

   4.  Consider how to best map NOC application desires to underlying
       transport mechanisms: With the above mentioned 3 points, not all
       options are covered.  Depending on the OAM operation, one may
       still want only ACP, only data-plane, or automatically prefer one
       over the other and/or use the ACP with low performance or high-
       performance (for emergency OAM actions such as countering DDoS).
       It is as of today not clear what the simplest set of tools is to
       enable explicitly the choice of desired behavior of each OAM
       operations.  The use of the above mentioned DNS and MP-TCP




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       mechanisms is a start, but this will require additional thoughts.
       This is likely a specific case of the more generic scope of TAPS.

2.2.  Stable connectivity for distributed network/OAM functions

   The ACP can provide common direct-neighbor discovery and capability
   negotiation and stable and secure connectivity for functions running
   distributed in network devices.  It can therefore eliminate the need
   to re-implement similar functions in each distributed function in the
   network.  Today, every distributed protocol does this with functional
   elements usually called "Hello" mechanisms and with often protocol
   specific security mechanisms.

   KARP has tried to start provide common directions and therefore
   reduce the re-invention of at least some of the security aspects, but
   it only covers routing-protocols and it is unclear how well it
   applicable to a potentially wider range of network distributed agents
   such as those performing distributed OAM functions.  The ACP can help
   in these cases.

   This section is TBD for further iterations of this draft.

3.  Security Considerations

   We discuss only security considerations not covered in the
   appropriate sub-sections of the solutions described.

   Even though ACPs are meant to be isolated, explicit operator
   misconfiguration to connect to insecure OAM equipment and/or bugs in
   ACP devices may cause leakage into places where it is not expected.
   Mergers/Aquisitions and other complex network reconfigurations
   affecting the NOC are typical examples.

   ULA addressing as proposed in this document is preferred over
   globally reachable addresses because it is not routed in the global
   Internet and will therefore be subject to more filtering even in
   places where specific ULA addresses are being used.

   Randomn ULA addressing provides more than sufficient protection
   against address collision even though there is no central assignment
   authority.  This is helped by the expectation, that ACPs are never
   expected to connect all together, but only few ACPs may ever need to
   connect together, eg: when mergers and aquisitions occur.

   If packets with unexpected ULA addresses are seen and one expects
   them to be from another networks ACP from which they leaked, then
   some form of ULA prefix registrastion (not allocation) can be
   beneficial.  Some voluntary registries exist, for example



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   https://www.sixxs.net/tools/grh/ula/, although none of them is
   preferrable because of being operated by some recognized authority.
   If an operator would want to make its ULA prefix known, it might need
   to register it with multiple existing registries.

   ULA Centrally assigned ULA addresses (ULA-C) was an attempt to
   introduce centralized registration of randomnly assigned addresses
   and potentially even carve out a different ULA prefix for such
   addresses.  This proposal is currently not proceeding, and it is
   questionable whether the stable connectivity use case provides
   sufficient motivation to revive this effort.

   Using current registration options implies that there will not be
   reverse DNS mapping for ACP addresses.  For that one will have to
   rely on looking up the unknown/unexpected network prefix in the
   registry registry to determine the owner of these addresses.

   Reverse DNS resolution may be beneficial for specific already
   deployed insecure legacy protocols on NOC OAM systems that intend to
   communicate via the ACP (eg: TFTP) and leverages reverse-DNS for
   authentication.  Given how the ACP provides path security except
   potentially for the last-hop in the NOC, the ACP does make it easier
   to extend the lifespan of such protocols in a secure fashion as far
   to just the transport is concerned.  The ACP does not make reverse
   DNS lookup a secure authentication method though.  Any current and
   future protocols must rely on secure end-to-end communications (TLD,
   dTLS) and identification and authentication via the certificates
   assigned to both ends.  This is enabled by the certificate mechanisms
   of the ACP.

   If DNS and especially reverse DNS are set up, then it should be set
   up in an automated fashion, linked to the autonomic registrar backend
   so that the DNS and reverse DNS records are actually derived from the
   subject name elements of the ACP device certificates in the same way
   as the autonomic devices themselves will derive their ULA addresses
   from their certificates to ensure correct and consistent DNS entries.

   If an operator feels that reverse DNS records are beneficial to its
   own operations but that they should not be made available publically
   for "security" by concealment reasons, then the case of ACP DNS
   entries is probably one of the least problematic use cases for split-
   DNS: The ACP DNS names are only needed for the NOC applications
   intending to use the ACP - but not network wide across the
   enterprise.







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4.  No IPv4 for ACP

   The ACP is targeted to be IPv6 only, and the prior explanations in
   this document show that this can lead to some complexity when having
   to connect IPv4 only NOC solutions, and that it will be impossible to
   leverage the ACP when the OAM agents on an ACP network device do not
   support IPv6.  Therefore, the question was raised whether the ACP
   should optionally also support IPv4.

   The decision not to include IPv4 for ACP as something that is
   considered in the use cases in this document is because of the
   following reasons:

   In SP networks that have started to support IPv6, often the next
   planned step is to consider moving out IPv4 from a native transport
   as just a service on the edge.  There is no benefit/need for multiple
   parallel transport families within the network, and standardizing on
   one reduces OPEX and improves reliability.  This evolution in the
   data plane makes it highly unlikely that investing development cycles
   into IPv4 support for ACP will have a longer term benefit or enough
   critical short-term use-cases.  Support for only IPv4 for ACP is
   purely a strategic choice to focus on the known important long term
   goals.

   In other type of networks as well, we think that efforts to support
   autonomic networking is better spent in ensuring that one address
   family will be support so all use cases will long-term work with it,
   instead of duplicating effort into IPv4.  Especially because auto-
   addressing for the ACP with IPv4 would be more ecomplex than in IPv6
   due to the the IPv4 addressing space.

5.  Further considerations

6.  IANA Considerations

   This document requests no action by IANA.

7.  Acknowledgements

   This work originated from an Autonomic Networking project at cisco
   Systems, which started in early 2010 including customers involved in
   the design and early testing.  Many people contributed to the aspects
   described in this document, including in alphabetical order: BL
   Balaji, Steinthor Bjarnason, Yves Herthoghs, Sebastian Meissner, Ravi
   Kumar Vadapalli.  The author would also like to thank Michael
   Richardson, James Woodyatt and Brian Carpenter for their review and
   comments.




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8.  Change log [RFC Editor: Please remove]

      02: Updated references.

      02: Modified ULA text to not suggest ULA-C as much better anymore,
      but still mention it.

      02: Added explanation why no IPv4 for ACP.

      01: Added security section discussing the role of address prefix
      selection and DNS for ACP.  Title change to emphasize focus on
      OAM.  Expanded abstract.

      00: Initial version.

9.  References

   [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-04 (work in progress), October 2015.

   [I-D.ietf-anima-autonomic-control-plane]
              Behringer, M., Bjarnason, S., BL, B., and T. Eckert, "An
              Autonomic Control Plane", draft-ietf-anima-autonomic-
              control-plane-01 (work in progress), October 2015.

   [I-D.ietf-anima-bootstrapping-keyinfra]
              Pritikin, M., Richardson, M., Behringer, M., and S.
              Bjarnason, "Bootstrapping Key Infrastructures", draft-
              ietf-anima-bootstrapping-keyinfra-01 (work in progress),
              October 2015.

   [I-D.irtf-nmrg-an-gap-analysis]
              Jiang, S., Carpenter, B., and M. Behringer, "General Gap
              Analysis for Autonomic Networking", draft-irtf-nmrg-an-
              gap-analysis-06 (work in progress), April 2015.

   [I-D.irtf-nmrg-autonomic-network-definitions]
              Behringer, M., Pritikin, M., Bjarnason, S., Clemm, A.,
              Carpenter, B., Jiang, S., and L. Ciavaglia, "Autonomic
              Networking - Definitions and Design Goals", draft-irtf-
              nmrg-autonomic-network-definitions-07 (work in progress),
              March 2015.






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   [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>.

Authors' Addresses

   Toerless Eckert
   Cisco

   Email: eckert@cisco.com


   Michael H. Behringer
   Cisco

   Email: mbehring@cisco.com



































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