Using Autonomic Control Plane for Stable Connectivity of Network OAM
draft-ietf-anima-stable-connectivity-07

Versions: (draft-eckert-anima-stable-connectivity)         Informational
          00 01 02 03 04 05 06 07                                       
ANIMA                                                     T. Eckert, Ed.
Internet-Draft                                                    Huawei
Intended status: Informational                              M. Behringer
Expires: March 21, 2018                               September 17, 2017


  Using Autonomic Control Plane for Stable Connectivity of Network OAM
                draft-ietf-anima-stable-connectivity-06

Abstract

   OAM (Operations, Administration and Maintenance - as per BCP161,
   [RFC6291]) processes for data networks are often subject to the
   problem of circular dependencies when relying on connectivity
   provided by the network to be managed for the OAM purposes.

   Provisioning while bringing up devices and networks tends to be more
   difficult to automate than service provisioning later on, changes in
   core network functions impacting reachability cannot be automated
   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) in order to
   provide stable and secure connectivity for those OAM processes.  This
   connectivity is not subject to aforementioned circular dependencies.

Status of This Memo

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

   Internet-Drafts are working documents of the Internet Engineering
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   This Internet-Draft will expire on March 21, 2018.







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Copyright Notice

   Copyright (c) 2017 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents
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   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  . . . . . . . . . . . . . . . . . . .   4
   2.  Solutions . . . . . . . . . . . . . . . . . . . . . . . . . .   4
     2.1.  Stable Connectivity for Centralized OAM . . . . . . . . .   4
       2.1.1.  Simple Connectivity for Non-ACP capable NMS Hosts . .   5
       2.1.2.  Challenges and Limitation of Simple Connectivity  . .   6
       2.1.3.  Simultaneous ACP and Data Plane Connectivity  . . . .   7
       2.1.4.  IPv4-only NMS Hosts . . . . . . . . . . . . . . . . .   8
       2.1.5.  Path Selection Policies . . . . . . . . . . . . . . .  11
       2.1.6.  Autonomic NOC Device/Applications . . . . . . . . . .  12
       2.1.7.  Encryption of data-plane connections  . . . . . . . .  13
       2.1.8.  Long Term Direction of the Solution . . . . . . . . .  14
     2.2.  Stable Connectivity for Distributed Network/OAM . . . . .  15
   3.  Architectural Considerations  . . . . . . . . . . . . . . . .  15
     3.1.  No IPv4 for ACP . . . . . . . . . . . . . . . . . . . . .  15
   4.  Security Considerations . . . . . . . . . . . . . . . . . . .  16
   5.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  17
   6.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .  17
   7.  Change log [RFC Editor: Please remove]  . . . . . . . . . . .  18
   8.  References  . . . . . . . . . . . . . . . . . . . . . . . . .  19
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  21

1.  Introduction

1.1.  Self dependent OAM Connectivity

   OAM (Operations, Administration and Maintenance - as per BCP161,
   [RFC6291]) for data networks is often subject to the problem of
   circular dependencies when relying on the connectivity service



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   provided by the network to be managed.  OAM can easily but
   unintentionally break the connectivity required for its own
   operations.  Avoiding these problems can lead to complexity in OAM.
   This document describes this problem and how to use the Autonomic
   Control Plane (ACP) to solve it without further OAM complexity:

   The ability to perform OAM on a network device requires first the
   execution of OAM necessary to create network connectivity to that
   device in all intervening devices.  This typically leads to
   sequential, 'expanding ring configuration' from a NOC (Network
   Operations Center).  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, forwarding, 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.  Examples include change of an IGP or areas, PA (Provider
   Aggregatabe) to PI (Provider Independent) addressing, or systematic
   topology changes (such as L2 to L3 changes).

   All these circular dependencies make OAM complex and potentially
   fragile.  When automation is being used, for example through
   provisioning systems, 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 within Network Providers.  This concept was
   standardized in ITU-T G.7712/Y.1703 [ITUT] 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 (Public
   Switched Telephone Network) 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



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   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 providers, most notably smaller providers, most
   enterprises and typical IoT networks (Internet of Things).

1.3.  Leveraging the ACP

   One of the goals of the Autonomic Networks Autonomic Control Plane
   (ACP as defined in [I-D.ietf-anima-autonomic-control-plane] ) 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.

   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", a.k.a: 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 for OAM purposes.  This is the current scope of
   this document.

2.  Solutions

2.1.  Stable Connectivity for Centralized OAM

   The ANI is the "Autonomic Networking Infrastructure" consisting of
   secure zero touch Bootstrap (BRSKI -
   [I-D.ietf-anima-bootstrapping-keyinfra]), GeneRic Autonomic Signaling
   Protocol (GRASP - [I-D.ietf-anima-grasp]), and Autonomic Control
   Plane (ACP - [I-D.ietf-anima-autonomic-control-plane]).  Refer to
   [I-D.ietf-anima-reference-model]  for an overview of the ANI and how
   its components interact and [RFC7575] for concepts and terminology of
   ANI and autonomic networks.

   This section describes stable connectivity for centralized OAM via
   ACP/ANI starting by what we expect to be the most easy to deploy
   short-term option.  It then describes limitation and challenges of
   that approach and their solutions/workarounds to finish with the
   preferred target option of autonomic NOC devices in Section 2.1.6.

   This order was chosen because it helps to explain how simple initial
   use of ACP can be, how difficult workarounds can become (and
   therefore what to avoid), and finally because one very promising




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   long-term solution alternative is exactly like the most easy short-
   term solution only virtualized and automated.

   In the most common case, OAM 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.  There is a
   wide range of options, some of which are simple, some more complex.

   Three stages can be considered:

   o  There are simple options described in sections Section 2.1.1
      through Section 2.1.3 that we consider to be good starting points
      to operationalize the use of the ACP for stable connectivity
      today.  These options require only network and OAN/NOC device
      configuration.

   o  The are workarounds to connect the ACP to non-IPv6 capable NOC
      devices through the use of IPv4/IPv6 NAT (Network Address
      Translation) as described in section Section 2.1.4.  These
      workarounds are not recommended but if such non-IPv6 capable NOC
      devices need to be used longer term, then this is the only option
      to connect them to the ACP.

   o  Near to long term options can provide 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 and
      development work on NOC/OAM equipment is necessary.  These options
      are discussed in sections Section 2.1.5 through Section 2.1.8.

2.1.1.  Simple Connectivity for Non-ACP capable NMS Hosts

   In the most simple candidate deployment case, the ACP extends all the
   way into the NOC via one or more "ACP edge devices" as defined in
   section 6.1 of [I-D.ietf-anima-autonomic-control-plane].  These
   devices "leak" the (otherwise encrypted) ACP natively to NMS hosts.
   They acts as the default router to those NMS hosts and provide them
   with IPv6 connectivity into the ACP.  NMS hosts with this setup need
   to support IPv6 (see e.g.  [RFC6434]) but require no other
   modifications to leverage the ACP.

   Note that even though the ACP only uses IPv6, it can of course
   support OAM for any type of network deployment as long as the network
   devices support the ACP: The Data Plane can be IPv4 only, dual-stack
   or IPv6 only.  It is always spearate from the ACP, therefore there is
   no dependency between the ACP and the IP version(s) used in the Data
   Plane.




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   This setup is sufficient for troubleshooting such as SSH into network
   devices, NMS that performs SNMP read operations for status checking,
   software downloads into autonomic devices, provisioning of devices
   via NETCONF and so on.  In conjunction with otherwise unmodified OAM
   via separate NMS hosts it can provide a good subset of the stable
   connectivity goals.  The limitations of this approach are discussed
   in the next section.

   Because the ACP provides 'only' for IPv6 connectivity, and because
   addressing provided by the ACP does not include any topological
   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 (Domain Name System - see [RFC1034]) so that
   the ACP IPv6 addresses of autonomic devices are known via domain
   names that include the desired structure.  For example, if DNS in the
   network was set up with names for network devices as
   devicename.noc.example.com, and the well known structure of the Data
   Plane IPv4 addresses space was used by operators to infer the region
   where a device is located in, then the ACP address of that device
   could be set up as devicename_<region>.acp.noc.example.com, and
   devicename.acp.noc.example.com could be a CNAME to
   devicename_<region>.acp.noc.example.com.  Note that many networks
   already use names for network equipment where topological information
   is included, even without an ACP.

2.1.2.  Challenges and Limitation of Simple Connectivity

   This simple connectivity of non-autonomic NMS hosts suffers from a
   range of challenges (that is, operators may not be able to do it this
   way) or limitations (that is, operator cannot achieve desired goals
   with this setup).  The following list summarizes these challenges and
   limitations.  The following sections describe additional mechanisms
   to overcome them.

   Note that these challenges and limitations exist because ACP is
   primarily designed to support distributed ASA (Autonomic Service
   Agent, a piece of autonomic software) in the most lightweight
   fashion, but not mandatorily require support for additional
   mechanisms to best support centralized NOC operations.  It is this
   document that describes additional (short term) workarounds and (long
   term) extensions.

   1.  (Limitation) NMS hosts cannot directly probe whether the desired
       so called 'data-plane' network connectivity works because they do
       not directly have access to it.  This problem is similar to
       probing connectivity for other services (such as VPN services)
       that they do not have direct access to, so the NOC may already




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       employ appropriate mechanisms to deal with this issue (probing
       proxies).  See Section 2.1.3 for candidate solutions.

   2.  (Challenge) NMS hosts need to support IPv6 which often is still
       not possible in enterprise networks.  See Section 2.1.4 for some
       workarounds.

   3.  (Limitation) 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.  See Section 2.1.5 for candidate solutions.

   4.  (Limitation) Security of the ACP is reduced by exposing the ACP
       natively (and unencrypted) into a subnet in the NOC where the NOC
       devices are attached to it.  See Section 2.1.7 for candidate
       solutions.

   These four problems can be tackled independently of each other by
   solution improvements.  Combining some of these solutions
   improvements together can lead towards a candiate 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 IPv4-only, 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 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 attach the ACP device(s) as the IPv6 default router to
   the NOC subnet and keep the existing IPv4 default router setup
   unchanged.

   If the data-plane of the network is also supporting IPv6, then the
   most compatible setup for NOC devices is to have two IPv6 interfaces.
   One virtual ((e.g. via IEEE 802.1Q [IEEE802.1Q]) or physical
   interface connecting to a data-plane subnet, and another into an ACP
   connect subnet as specified in the ACP connection section of
   [I-D.ietf-anima-autonomic-control-plane].  That document also
   specifies how the NOC devices can receive autoconfigured addressing
   and routes towards the ACP connect subnet if it supports [RFC6724]
   and [RFC4191].





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   Configuring a second interface on a NOC host may be impossible or be
   seen as undesired complexity.  In that case the ACP edge device needs
   to provide support for a "Combined ACP and Data Plane interface" as
   also described in the ACP connect section of
   [I-D.ietf-anima-autonomic-control-plane].  This setup may not work
   with autoconfiguration and all NOC host network stacks due to
   limitations in those network stacks.  They need to be able to perform
   RFC6724 source address selection rule 5.5 including caching of next-
   hop information.  See the ACP document text for more details.

   For security reasons, it is not considered appropriate in the ACP
   document to connect a non-ACP router to an ACP connect interface.
   The reason is that the ACP is a secured network domain and all NOC
   devices connecting via ACP connect interfaces are also part of that
   secure domain - the main difference is that the physical link between
   the ACP edge device and the NOC devices is not authenticated/
   encrypted and therefore needs to be physically secured.  If the
   secure ACP was extendable via untrusted routers then it would be a
   lot more verify the secure domain assertion.  Therefore the ACP edge
   devices are not supposed to redistribute routes from non-ACP routers
   into the ACP.

2.1.4.  IPv4-only NMS Hosts

   ACP does not support IPv4: Single stack IPv6 management of the
   network via ACP and (as needed) data plane.  Independent of whether
   the data plane is dual-stack, has IPv4 as a service or is single
   stack IPv6.  Dual plane management, IPv6 for ACP, IPv4 for the data
   plane is likewise an architecturally simple option.

   The implication of this architectural decision is the potential need
   for short-term workarounds when the operational practices in a
   network do not yet meet these target expectations.  This section
   explains when and why these workarounds may be operationally
   necessary and describes them.  However, the long term goal is to
   upgrade all NMS hosts to native IPv6, so the workarounds described in
   this section should not be considered permanent.

   Most network equipment today supports IPv6 but it is by far not
   ubiquitously supported in NOC backend solutions (HW/SW), especially
   not in the product space for enterprises.  Even when it is supported,
   there are often additional limitations or issues using it in a dual
   stack setup or the operator mandates for simplicity single stack for
   all operations.  For these reasons an IPv4 only management plane is
   still required and common practice in many enterprises.  Without the
   desire to leverage the ACP, this required and common practice is not
   a problem for those enterprises even when they run dual stack in the




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   network.  We discuss these workarounds here because it is a short
   term deployment challenge specific to the operations of the ACP.

   To connect IPv4 only management plane devices/applications with the
   ACP, some form of IP/ICMP translation of packets IPv4<->IPv6 is
   necessary.  The basic mechanisms for this are defined in SIIT
   ([RFC7915]).  There are multiple solutions using this mechanisms.  To
   understand the possible solutions, we consider the requirements:

   1.  NMS hosts need to be able to initiate connections to any ACP
       device for management purposes.  Examples include provisioning
       via Netconf/(SSH), SNMP poll operations or just diagnostics via
       SSH connections from operators.  Every ACP device/function that
       needs to be reachable from NMS hosts needs to have a separate
       IPv4 address.

   2.  ACP devices need to be able to initiate connections to NMS hosts
       for example to initiate NTP or radius/diameter connections, send
       syslog or SNMP trap or initiate Netconf Call Home connections
       after bootstrap.  Every NMS host needs to have a separate IPv6
       address reachable from the ACP.  When connections from ACP
       devices are made to NMS hosts, the IPv4 source address of these
       connections as seen by the NMS Host must also be unique per ACP
       device and the same address as in (1) to maintain the same
       addressing simplicity as in a native IPv4 deployment.  For
       example in syslog, the source-IP address of a logging device is
       used to identify it, and if the device shows problems, an
       operator might want to SSH into the device to diagnose it.

   Because of these requirements, the necessary and sufficient set of
   solutions are those that provide 1:1 mapping of IPv6 ACP addresses
   into IPv4 space and 1:1 mapping of IPv4 NMS host space into IPv6 (for
   use in the ACP).  This means that stateless SIIT based solutions are
   sufficient and preferred.

   Note that ACP devices may use multiple IPv6 addresses in the ACP
   based on which Sub-Scheme they use.  For example in the Zone Sub-
   Scheme, an ACP device could use two addresses, one with the last
   address bit (V-bit) 0 and one with 1.  Both addresses may need to be
   reachable thought the IPv6/IPv4 address translation.

   The need to allocate for every ACP device one or multiple IPv4
   addresses should not be a problem if - as we assume - the NMS hosts
   can use private IPv4 address space ([RFC1918]).  Nevertheless even
   with RFC1918 address space it is important that the ACP IPv6
   addresses can efficiently be mapped into IPv4 address space without
   too much waste.




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   The currently most flexible mapping scheme to achieve this is
   [RFC7757] because it allows configured IPv4 <-> IPv6 prefix mapping.
   Assume the ACP uses the Zone Addressing Sub-Scheme and there are 3
   registrars.  In the Zone Addressing Sub-Scheme, there is for each
   registrar a constant /112 prefix for which in RFC7757 an EAM
   (Explicit Address Mapping) into a /16 (eg: RFC1918) prefix into IPv4
   can be configured.  Within the registrars /112 prefix, Device-Numbers
   for devices are sequentially assigned: with V-bit effectively two
   numbers are assigned per ACP device.  This also means that if IPv4
   address space is even more constrained, and it is known that a
   registrar will never need the full /15 extent of Device-Numbers, then
   a longer than /112 prefix can be configured into the EAM to use less
   IPv4 space.

   When using the Vlong Addressing Sub-Scheme, it is unlikely that one
   wants or need to translate the full /8 or /16 bits of addressing
   space per ACP device into IPv4.  In this case, the EAM rules of
   dropping trailing bits can be used to map only N bits of the V-bits
   into IPv4.  This does imply though that only V-addresses that differ
   in those high-order N V-bits can be distinguished on the IPv4 side.

   Likewise, the IPv4 address space used for NMS hosts can easily be
   mapped into an ACP prefix assigned to an ACP connect interface.

   A full specification of a solution to perform SIIT in conjunction
   with ACP connect following the considerations below is outside the
   scope of this document.

   To be in compliance with security expectations, SIIT has to to happen
   on the ACP edge device itself so that ACP security considerations can
   be taken into account.  Eg: that IPv4 only NMS hosts can be dealt
   with exactly like IPv6 hosts connected to an ACP connect interface.

   Note that prior solutions such as NAT64 ([RFC6146]) may equally be
   useable to translate between ACP IPv6 address space and NMS Hosts
   IPv4 address space, and that as workarounds this can also be done on
   non ACP Edge Devices connected to an ACP connect interface.  The
   details vary depending on implementation because the options to
   configure address mappings vary widely.  Outside of EAM, there are no
   standardized solutions that allow for mapping of prefixes, so it will
   most likely be necessary to explicitly map every individual (/128)
   ACP device address to an IPv4 address.  Such an approach should use
   automation/scripting where these address translation entries are
   created dynamically whenever an ACP device is enrolled or first
   connected to the ACP network.

   Overall, the use of NAT is especially subject to the ROI (Return On
   Investment) considerations, but the methods described here may not be



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   too different from the same problems encountered totally independent
   of AN/ACP when some parts of the network are to introduce IPv6 but
   NMS hosts 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 network 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 NMS hosts
   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 e.g.  early
   stages of device bootstrap, failures, provisioning mistakes or during
   network configuration changes.

   The desired policy is therefore as follows: In the absence of further
   security considerations (see below), traffic between NMS hosts 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 an NMS host 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:





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   Ideally, a NOC system would learn and keep track of all addresses of
   a device (ACP and the various data plane addresses).  Every action of
   the NOC system would indicate via a "path-policy" what type of
   connection it needs (e.g. only data-plane, ACP-only, default to data-
   plane, fallback to ACP,...).  A connection policy manager would then
   build connection to the target using the right address(es).  Shorter
   term, a common practice is to identify different paths to a device
   via different names (e.g. loopback vs. interface addresses).  This
   approach can be expanded to ACP uses, whether it uses NOC system
   local names or DNS.  We describe example schemes using DNS:

   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.

   MPTCP (Multipath TCP -see [RFC6824]) 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 MPTCP aware applications would be as follows:

   DNS naming is set up to provide the ACP IPv6 address of network
   devices.  Unbeknownst to the application, MPTCP is used.  MPTCP
   mutually discovers between the NOC and network device the data-plane
   address and caries all traffic across it when that MPTCP subflow
   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 MPTCP subflow 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.

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



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   paragraphs in a range of connectivity considerations, some of which
   may be quite undesirable or complex to operationalize.

   Making NMS hosts 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 e.g. a tap driver to make the ACP show up as another IPv6 enabled
   interface.

   Having said this: If the structure of NMS hosts is transformed
   through virtualization anyhow, then it may be considered equally
   secure and appropriate to construct (physical) NMS host 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 just 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 simplest solution for this problem exists when using AN capable
   NMS hosts, because in that case the communicating AN capable NMS host
   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 ([RFC5246]/[RFC6347]) with mutual AN-domain certificate
   authentication - and does not incur new key management.

   If this automatic security benefit is seen as most important, but a
   "full" ACP stack into the NMS host 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



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   AN domain to the extent 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
   NMS hosts 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.  NMS hosts 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 translation may be an option but this has not been
       investigated yet.

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

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

   4.  Consider how to best map NMS host desires to underlying transport
       mechanisms: With the above mentioned 3 points, not all options
       are covered.  Depending on the OAM, 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 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.  The use of the above
       mentioned DNS and MPTCP mechanisms is a start, but this will
       require additional thoughts.  This is likely a specific case of
       the more generic scope of TAPS.







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2.2.  Stable Connectivity for Distributed Network/OAM

   The ANI (ACP, Bootstrap, GRASP) can provide via the GRASP protocol
   common direct-neighbor discovery and capability negotiation (GRASP
   via ACP and/or data-plane) and stable and secure connectivity for
   functions running distributed in network devices (GRASP via ACP).  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 (Keying and Authentication for Routing Protocols, see [RFC6518])
   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.  The ACP can help in these cases.

3.  Architectural Considerations

3.1.  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 IPv4-only 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-



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   addressing for the ACP with IPv4 would be more complex than in IPv6
   due to the IPv4 addressing space.

4.  Security Considerations

   In this section, 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/Acquisitions and other complex network reconfigurations
   affecting the NOC are typical examples.

   ACP prefix addresses are ULA addresses.  Using these addresses also
   for NOC devices as proposed in this document is not only necessary
   for above explained simple routing functionality but it is also more
   secure than global IPv6 addresses.  ULA addresses are not routed in
   the global Internet and will therefore be subject to more filtering
   even in places where specific ULA addresses are being used.  Packets
   are therefore less likely to leak to be successfully injected into
   the isolated ACP environment.

   The random nature of a ULA prefix provides strong 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, e.g. when mergers and aquisitions occur.

   The ACP specification demands that only packets from configured ACP
   prefixes are permitted from ACP connect interfaces.  It also requires
   that RPL root ACP devices need to be able to diagnose unknown ACP
   destination addresses.

   To help diagnose packets that unexpectedly leaked for example from
   another ACP (that was meant to be deployed separately), it can be
   useful to voluntarily list your own the ULA ACP prefixes in one of
   the sites on the Internet, for example
   https://www.sixxs.net/tools/grh/ula/. Note that this does not
   constitute registration and if you want to ensure that your leaked
   ACP packets can be recognized to come from you, you may need to list
   your prefixes in multiple of those sites.

   Note that there is a provision in [RFC4193] for non-locally assigned
   address space (L bit = 0), but there is no existing standardization
   for this, so these ULA prefixes must not be used.





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   According to RFC4193 section 4.4, PTR records for ULA addresses
   should not be installed into the global DNS (no guaranteed
   ownership).  Hence also the need to rely on voluntary lists (and in
   prior paragraph) to make the use of an ULA prefix globally known.

   Nevertheless, some legacy OAM applications running across the ACP may
   rely on reverse DNS lookup for authentication of requests (eg: TFTP
   for download of network firmware/config/software).  Operators may
   therefore need to use a private DNS setup for the ACP ULA addresses.
   This is the same setup that would be necessary for using RFC1918
   addresses in DNS.  See for example [RFC1918] section 5, last
   paragraph.  In [RFC6950] section 4, these setups are discussed in
   more detail.

   Any current and future protocols must rely on secure end-to-end
   communications (TLS/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 NMS hosts intending to
   use the ACP - but not network wide across the enterprise.

5.  IANA Considerations

   This document requests no action by IANA.

6.  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.  Special thanks to Sheng Jiang and Mohamed Boucadair for
   their thorough review.



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7.  Change log [RFC Editor: Please remove]

      06: changed "split-horizon" term to "private-DNS" and reworded the
      paragraph about it.

      05: Integrated fixes from Brian Carpenters review.  See github
      draft-ietf-anima-stable-connectivity/04-brian-carpenter-review-
      reply.txt.  Details on semantic/structural changes:



      *  Folded most comments back into draft-ietf-anima-autonomic-
         control-plane-09 because this stable connectivity draft was
         suggesting things that are better written out and standardized
         in the ACP document.

      *  Section on simultaneous ACP and data plane connectivity section
         reduced/rewritten because of this.

      *  Re-emphasized security model of ACP - ACP-connect can not
         arbitrarily extend ACP routing domain.

      *  Re-wrote much of NMS section to be less suggestive and more
         descriptive, avoiding the term NAT and referring to relevant
         RFCs (SIIT etc.).

      *  Main additional text in IPv4 section is about explaining how we
         suggest to use EAM (Explicit Address Mapping) which actuall
         would well work with the Zone and Vlong Addressing Sub-Schemes
         of ACP.

      *  Moved, but not changed section of "why no IPv4 in ACP" before
         IANA considerations to make structure of document more logical.

      *  Refined security considerations: explained how optional ULA
         prefix listing on Internet is only for diagnostic purposes.
         Explained how this is useful because DNS must not be used.
         Explained how split horizon DNS can be used nevertheless.

      04: Integrated fixes from Mohamed Boucadairs review (thorough
      textual review).

      03: Integrated fixes from thorough Shepherd review (Sheng Jiang).

      01: Refresh timeout.  Stable document, change in author
      association.

      01: Refresh timeout.  Stable document, no changes.



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      00: Changed title/dates.

      individual-02: Updated references.

      individual-03: Modified ULA text to not suggest ULA-C as much
      better anymore, but still mention it.

      individual-02: Added explanation why no IPv4 for ACP.

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

      individual-00: Initial version.

8.  References

   [I-D.ietf-anima-autonomic-control-plane]
              Behringer, M., Eckert, T., and S. Bjarnason, "An Autonomic
              Control Plane (ACP)", draft-ietf-anima-autonomic-control-
              plane-09 (work in progress), August 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-07 (work in progress), July 2017.

   [I-D.ietf-anima-grasp]
              Bormann, C., Carpenter, B., and B. Liu, "A Generic
              Autonomic Signaling Protocol (GRASP)", draft-ietf-anima-
              grasp-15 (work in progress), July 2017.

   [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.

   [IEEE802.1Q]
              International Telecommunication Union, "802.1Q-2014 - IEEE
              Standard for Local and metropolitan area networks -
              Bridges and Bridged Networks", 2014.

   [ITUT]     International Telecommunication Union, "Architecture and
              specification of data communication network",
              ITU-T Recommendation G.7712/Y.1703, Noevember 2001.




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              This is the earliest but superceeded version of the
              series.  See REC-G.7712 Home Page [1] for current
              versions.

   [RFC1034]  Mockapetris, P., "Domain names - concepts and facilities",
              STD 13, RFC 1034, DOI 10.17487/RFC1034, November 1987,
              <https://www.rfc-editor.org/info/rfc1034>.

   [RFC1918]  Rekhter, Y., Moskowitz, B., Karrenberg, D., de Groot, G.,
              and E. Lear, "Address Allocation for Private Internets",
              BCP 5, RFC 1918, DOI 10.17487/RFC1918, February 1996,
              <https://www.rfc-editor.org/info/rfc1918>.

   [RFC4191]  Draves, R. and D. Thaler, "Default Router Preferences and
              More-Specific Routes", RFC 4191, DOI 10.17487/RFC4191,
              November 2005, <https://www.rfc-editor.org/info/rfc4191>.

   [RFC4193]  Hinden, R. and B. Haberman, "Unique Local IPv6 Unicast
              Addresses", RFC 4193, DOI 10.17487/RFC4193, October 2005,
              <https://www.rfc-editor.org/info/rfc4193>.

   [RFC5246]  Dierks, T. and E. Rescorla, "The Transport Layer Security
              (TLS) Protocol Version 1.2", RFC 5246,
              DOI 10.17487/RFC5246, August 2008,
              <https://www.rfc-editor.org/info/rfc5246>.

   [RFC6146]  Bagnulo, M., Matthews, P., and I. van Beijnum, "Stateful
              NAT64: Network Address and Protocol Translation from IPv6
              Clients to IPv4 Servers", RFC 6146, DOI 10.17487/RFC6146,
              April 2011, <https://www.rfc-editor.org/info/rfc6146>.

   [RFC6291]  Andersson, L., van Helvoort, H., Bonica, R., Romascanu,
              D., and S. Mansfield, "Guidelines for the Use of the "OAM"
              Acronym in the IETF", BCP 161, RFC 6291,
              DOI 10.17487/RFC6291, June 2011,
              <https://www.rfc-editor.org/info/rfc6291>.

   [RFC6347]  Rescorla, E. and N. Modadugu, "Datagram Transport Layer
              Security Version 1.2", RFC 6347, DOI 10.17487/RFC6347,
              January 2012, <https://www.rfc-editor.org/info/rfc6347>.

   [RFC6418]  Blanchet, M. and P. Seite, "Multiple Interfaces and
              Provisioning Domains Problem Statement", RFC 6418,
              DOI 10.17487/RFC6418, November 2011,
              <https://www.rfc-editor.org/info/rfc6418>.






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   [RFC6434]  Jankiewicz, E., Loughney, J., and T. Narten, "IPv6 Node
              Requirements", RFC 6434, DOI 10.17487/RFC6434, December
              2011, <https://www.rfc-editor.org/info/rfc6434>.

   [RFC6518]  Lebovitz, G. and M. Bhatia, "Keying and Authentication for
              Routing Protocols (KARP) Design Guidelines", RFC 6518,
              DOI 10.17487/RFC6518, February 2012,
              <https://www.rfc-editor.org/info/rfc6518>.

   [RFC6724]  Thaler, D., Ed., Draves, R., Matsumoto, A., and T. Chown,
              "Default Address Selection for Internet Protocol Version 6
              (IPv6)", RFC 6724, DOI 10.17487/RFC6724, September 2012,
              <https://www.rfc-editor.org/info/rfc6724>.

   [RFC6824]  Ford, A., Raiciu, C., Handley, M., and O. Bonaventure,
              "TCP Extensions for Multipath Operation with Multiple
              Addresses", RFC 6824, DOI 10.17487/RFC6824, January 2013,
              <https://www.rfc-editor.org/info/rfc6824>.

   [RFC6950]  Peterson, J., Kolkman, O., Tschofenig, H., and B. Aboba,
              "Architectural Considerations on Application Features in
              the DNS", RFC 6950, DOI 10.17487/RFC6950, October 2013,
              <https://www.rfc-editor.org/info/rfc6950>.

   [RFC7575]  Behringer, M., Pritikin, M., Bjarnason, S., Clemm, A.,
              Carpenter, B., Jiang, S., and L. Ciavaglia, "Autonomic
              Networking: Definitions and Design Goals", RFC 7575,
              DOI 10.17487/RFC7575, June 2015,
              <https://www.rfc-editor.org/info/rfc7575>.

   [RFC7757]  Anderson, T. and A. Leiva Popper, "Explicit Address
              Mappings for Stateless IP/ICMP Translation", RFC 7757,
              DOI 10.17487/RFC7757, February 2016,
              <https://www.rfc-editor.org/info/rfc7757>.

   [RFC7915]  Bao, C., Li, X., Baker, F., Anderson, T., and F. Gont,
              "IP/ICMP Translation Algorithm", RFC 7915,
              DOI 10.17487/RFC7915, June 2016,
              <https://www.rfc-editor.org/info/rfc7915>.

Authors' Addresses










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   Toerless Eckert (editor)
   Futurewei Technologies Inc.
   2330 Central Expy
   Santa Clara  95050
   USA

   Email: tte+ietf@cs.fau.de


   Michael H. Behringer

   Email: michael.h.behringer@gmail.com







































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