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BGP Extended Community for Identifying the Target Nodes
draft-dong-idr-node-target-ext-comm-05

Document Type Active Internet-Draft (candidate for idr WG)
Authors Jie Dong , Shunwan Zhuang , Gunter Van de Velde
Last updated 2022-09-27 (Latest revision 2022-07-11)
RFC stream Internet Engineering Task Force (IETF)
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draft-dong-idr-node-target-ext-comm-05
Network Working Group                                            J. Dong
Internet-Draft                                                 S. Zhuang
Intended status: Standards Track                     Huawei Technologies
Expires: 12 January 2023                                 G. Van de Velde
                                                                   Nokia
                                                            11 July 2022

        BGP Extended Community for Identifying the Target Nodes
                 draft-dong-idr-node-target-ext-comm-05

Abstract

   BGP has been used to distribute different types of routing and policy
   information.  In some cases, the information distributed may be only
   intended for one or a particular group of BGP nodes in the network.
   Currently BGP does not have a generic mechanism of designating the
   target nodes of the routing information.  This document defines a new
   type of BGP Extended Community called "Node Target".  The mechanism
   of using the Node Target Extended Community to steer BGP route
   distribution to particular BGP nodes is specified.

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 https://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 12 January 2023.

Copyright Notice

   Copyright (c) 2022 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 (https://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

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   and restrictions with respect to this document.  Code Components
   extracted from this document must include Revised BSD License text as
   described in Section 4.e of the Trust Legal Provisions and are
   provided without warranty as described in the Revised BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
     1.1.  Requirements Language . . . . . . . . . . . . . . . . . .   3
   2.  Node Target Extended Communities  . . . . . . . . . . . . . .   3
   3.  Procedures  . . . . . . . . . . . . . . . . . . . . . . . . .   4
   4.  Compatibility Considerations  . . . . . . . . . . . . . . . .   5
   5.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   5
   6.  Security Considerations . . . . . . . . . . . . . . . . . . .   5
   7.  Contributors  . . . . . . . . . . . . . . . . . . . . . . . .   6
   8.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .   6
   9.  References  . . . . . . . . . . . . . . . . . . . . . . . . .   6
     9.1.  Normative References  . . . . . . . . . . . . . . . . . .   6
     9.2.  Informative References  . . . . . . . . . . . . . . . . .   6
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .   7

1.  Introduction

   BGP [RFC4271] has been used to distribute different types of routing
   and policy information.  In some cases, the information distributed
   may be only intended for one or a group of receiving BGP nodes in the
   network.  One typical use case is the distribution of BGP Flow Spec
   [RFC8955] [RFC8956] rules only to a particular group of BGP nodes.
   Such a targeted distribution mechanism is considered useful as it can
   save the resources on nodes which do not need that information.

   Currently BGP does not have a generic mechanism of designating the
   set of nodes to which the information is to be distributed.  Route
   Target (RT) as defined in [RFC4364] was designed for the matching of
   VPN routes into the target VPN Routing and Forwarding tables (VRFs)
   on the PE nodes.  [I-D.ietf-idr-segment-routing-te-policy] introduces
   the mechanism of steering the SR Policy information to the target
   head end node based on RT, it is only applicable to the SR Policy
   Address Family.  Although it is possible to reuse RT to control the
   distribution of non-VPN information to one or a group of receiving
   nodes, such mechanism is not applicable when the information to be
   distributed is VPN-specific and is advertised with another set of RTs
   for the VRF matching, as the matching or any of the VPN RT in the BGP
   route would result in that route being imported to a local VRF,
   regardless of whether the receiving node is the target node or not.
   Thus a general mechanism which is independent from the control of VPN
   route to VRF import is needed.

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   Another possible approach is to configure, on each router, a
   community and the corresponding policies to match the community to
   determine whether to accept the received routes or not.  Such
   mechanism relies on manual configuration thus is considered error-
   prone.  It is preferable by some operators that an automatic approach
   can be provided, which would make the operation much easier.

   This document defines a new type of BGP Extended Community called
   "Node Target".  The mechanism of using the Node Target extended
   community to control the BGP route distribution only to particular
   BGP nodes is also specified.

1.1.  Requirements Language

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
   "OPTIONAL" in this document are to be interpreted as described in BCP
   14 [RFC2119] [RFC8174] when, and only when, they appear in all
   capitals, as shown here.

2.  Node Target Extended Communities

   This section defines a new BGP Extended Community [RFC4360] called
   "Node Target Extended Community".  It can be a transitive extended
   community with the high-order octet of the type set to 0x01, or a
   non-transitive extended community with the high-order octet type set
   to 0x41.  The sub-type of the Node Target Extended Community is TBA.

   The format of Node Target Extended Community is shown in Figure 1.

       0                   1                   2                   3
       0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |  0x01 or 0x41 | Sub-Type(TBA) |    Target BGP Identifier      |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      | Target BGP Identifier (cont.) |           Reserved            |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

               Figure 1. Node Target extended community

   Where:

   Target BGP Identifier (4 octets): The BGP Identifier of a target
   node.  It is a 4-octet, unsigned, non-zero integer as defined in
   [RFC6286].

   Reserved field (2 octets): Reserved for future use, MUST be set to
   zero on transmission and ignored on receipt.

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   One or more Node Target extended communities MAY be carried in an
   Update message to designate a group of target BGP nodes.

3.  Procedures

   In this section, the mechanism for intra-domain scenario is
   described, the mechanism for inter-domain scenario is for further
   study.  The domain here refers to an administrative domain, which may
   consists of one or multiple ASes managed by a single operator.

   When a network controller or BGP speaker plans to advertise some BGP
   routing or policy information only to one or a group of BGP nodes in
   the network, it MUST put the BGP Identifier of each target node into
   the Node Target extended communities, and attach the Node Target
   extended communities to the routes or policies to be advertised.

   When a BGP speaker receives a BGP Update which contains one or more
   Node Target extended communities, it MUST check the target BGP
   Identifiers carried in the Node Target extended communities of the
   Update.

   *  If the target BGP Identifier in any of the Node Target extended
      community matches with the local BGP Identifier, this node is one
      of the target nodes of the Update, the information in the Update
      is eligible to be kept and installed on this node.

      -  If this node is a Route Reflector, and in the Update there is
         one or more Node Target extended communities which contains
         non-local BGP Identifiers, information in the Update are
         eligible be reflected to its peers according to the rules
         defined in [RFC4456].  The default behavior for the RR in this
         case is to reflect the Update to all its peers without checking
         their BGP Identifiers.  Depends on a configurable policy, the
         RR MAY further check the BGP Identifiers of its peers to
         determine the set of peers which are the target nodes of the
         Update, and only reflect the information in the Update to the
         matched BGP peers.

      -  If this node is an Autonomous System Border Router (ASBR), and
         the BGP Identifiers of one or more of its EBGP peers match with
         the Node Target extended communities in the Update, information
         in the Update is eligible to be advertised to the matched EBGP
         peers.

   *  If the target BGP Identifier in any of the Node target extended
      community does not match with the local BGP Identifier, this node
      is not the target node of Update, the information in the Update is
      not eligible to be installed on this node.

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      -  If this node is a Route Reflector, information in the Update is
         eligible to be reflected to its peers according to the rules
         defined in [RFC4456].  The default behavior for the RR in this
         case is to reflect the Update to all its peers without checking
         their BGP Identifiers.  Depends on a configurable policy, the
         RR MAY check the BGP Identifiers of its peers to determine the
         set of peers which are the target nodes of the Update, and only
         reflect the information in the Update to the matched BGP peers.

4.  Compatibility Considerations

   The Node Target extended community introduced in this document can be
   deployed incrementally in the network.  For BGP speakers which
   understand the Node Target extended community, it is used to
   determine whether the nodes are the target nodes of the Update.  For
   BGP speakers which do not understand the Node Target extended
   community, it will be ignored and the information in the Update will
   be processed and advertised based on normal BGP procedure.  Although
   this could ensure that the target nodes can always obtain the
   information needed, this may result in unnecessary state maintained
   on the legacy BGP nodes.  If the information advertised is the Flow
   Spec rules, the legacy BGP speakers may install unnecessary Flowspec
   rules, this may have impact on traffic which matches such rules, thus
   may result in unexpected traffic steering or filtering behaviors on
   such nodes.  This may be mitigated by setting appropriate routing
   policies on the legacy BGP nodes.

5.  IANA Considerations

   This document requests that IANA assigns one new sub-type for "Node
   Target Extended Community" from the "Transitive IPv4-Address-Specific
   Extended Community" registry of the "BGP Extended Communities"
   registry.

   This document requests that IANA assigns the same sub-type for "Node
   Target Extended Community" from the "Non-Transitive IPv4-Address-
   Specific Extended Community" registry of the "BGP Extended
   Communities" registry.

6.  Security Considerations

   The mechanism defined in this document can limit the scope of the
   receiving nodes of BGP Updates, which make it possible for an
   attacker to do fine-grained targeting of malicious BGP Updates only
   to a restricted set of routers.  This would potentially make it more
   difficult for a network administrator to discover an attack.  This
   may be mitigated by filtering the Node Target Extended Communities at
   the administrative network boundaries.

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7.  Contributors

   Haibo Wang
   Email: rainsword.wang@huawei.com

8.  Acknowledgements

   The authors would like to thank Zhenbin Li, Ercin Torun, Jeff Haas,
   Robert Raszuk and John Scudder for the review and discussion of this
   document.

9.  References

9.1.  Normative References

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119,
              DOI 10.17487/RFC2119, March 1997,
              <https://www.rfc-editor.org/info/rfc2119>.

   [RFC4271]  Rekhter, Y., Ed., Li, T., Ed., and S. Hares, Ed., "A
              Border Gateway Protocol 4 (BGP-4)", RFC 4271,
              DOI 10.17487/RFC4271, January 2006,
              <https://www.rfc-editor.org/info/rfc4271>.

   [RFC4360]  Sangli, S., Tappan, D., and Y. Rekhter, "BGP Extended
              Communities Attribute", RFC 4360, DOI 10.17487/RFC4360,
              February 2006, <https://www.rfc-editor.org/info/rfc4360>.

   [RFC4456]  Bates, T., Chen, E., and R. Chandra, "BGP Route
              Reflection: An Alternative to Full Mesh Internal BGP
              (IBGP)", RFC 4456, DOI 10.17487/RFC4456, April 2006,
              <https://www.rfc-editor.org/info/rfc4456>.

   [RFC8174]  Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
              2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
              May 2017, <https://www.rfc-editor.org/info/rfc8174>.

9.2.  Informative References

   [I-D.ietf-idr-segment-routing-te-policy]
              Previdi, S., Filsfils, C., Talaulikar, K., Mattes, P.,
              Jain, D., and S. Lin, "Advertising Segment Routing
              Policies in BGP", Work in Progress, Internet-Draft, draft-
              ietf-idr-segment-routing-te-policy-18, 16 June 2022,
              <https://www.ietf.org/archive/id/draft-ietf-idr-segment-
              routing-te-policy-18.txt>.

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   [RFC4364]  Rosen, E. and Y. Rekhter, "BGP/MPLS IP Virtual Private
              Networks (VPNs)", RFC 4364, DOI 10.17487/RFC4364, February
              2006, <https://www.rfc-editor.org/info/rfc4364>.

   [RFC5575]  Marques, P., Sheth, N., Raszuk, R., Greene, B., Mauch, J.,
              and D. McPherson, "Dissemination of Flow Specification
              Rules", RFC 5575, DOI 10.17487/RFC5575, August 2009,
              <https://www.rfc-editor.org/info/rfc5575>.

   [RFC6286]  Chen, E. and J. Yuan, "Autonomous-System-Wide Unique BGP
              Identifier for BGP-4", RFC 6286, DOI 10.17487/RFC6286,
              June 2011, <https://www.rfc-editor.org/info/rfc6286>.

   [RFC8955]  Loibl, C., Hares, S., Raszuk, R., McPherson, D., and M.
              Bacher, "Dissemination of Flow Specification Rules",
              RFC 8955, DOI 10.17487/RFC8955, December 2020,
              <https://www.rfc-editor.org/info/rfc8955>.

   [RFC8956]  Loibl, C., Ed., Raszuk, R., Ed., and S. Hares, Ed.,
              "Dissemination of Flow Specification Rules for IPv6",
              RFC 8956, DOI 10.17487/RFC8956, December 2020,
              <https://www.rfc-editor.org/info/rfc8956>.

Authors' Addresses

   Jie Dong
   Huawei Technologies
   Huawei Campus, No. 156 Beiqing Rd.
   Beijing
   100095
   China
   Email: jie.dong@huawei.com

   Shunwan Zhuang
   Huawei Technologies
   Huawei Campus, No. 156 Beiqing Rd.
   Beijing
   100095
   China
   Email: zhuangshunwan@huawei.com

   Gunter Van de Velde
   Nokia
   Antwerp
   Belgium
   Email: gunter.van_de_velde@nokia.com

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