Internet Engineering Task Force (IETF)                       J. Tantsura
Request for Comments: 9104                                     Microsoft
Category: Standards Track                                        Z. Wang
ISSN: 2070-1721                                                    Q. Wu
                                                           K. Talaulikar
                                                           Cisco Systems
                                                             August 2021

   Distribution of Traffic Engineering Extended Administrative Groups
        Using the Border Gateway Protocol - Link State (BGP-LS)


   Administrative groups are link attributes used for traffic
   engineering.  This document defines an extension to the Border
   Gateway Protocol - Link State (BGP-LS) for advertisement of extended
   administrative groups (EAGs).

Status of This Memo

   This is an Internet Standards Track document.

   This document is a product of the Internet Engineering Task Force
   (IETF).  It represents the consensus of the IETF community.  It has
   received public review and has been approved for publication by the
   Internet Engineering Steering Group (IESG).  Further information on
   Internet Standards is available in Section 2 of RFC 7841.

   Information about the current status of this document, any errata,
   and how to provide feedback on it may be obtained at

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Table of Contents

   1.  Introduction
     1.1.  Requirements Language
   2.  Advertising Extended Administrative Groups in BGP-LS
   3.  IANA Considerations
   4.  Manageability Considerations
   5.  Security Considerations
   6.  References
     6.1.  Normative References
     6.2.  Informative References
   Authors' Addresses

1.  Introduction

   Administrative groups (commonly referred to as "colors" or "link
   colors") are link attributes that are advertised by link-state
   protocols like IS-IS [RFC1195], OSPFv2 [RFC2328], and OSPFv3
   [RFC5340].  The Border Gateway Protocol - Link State (BGP-LS)
   advertisement of the originally defined (non-extended) administrative
   groups is encoded using the Administrative Group (color) TLV 1088 as
   defined in [RFC7752].

   These administrative groups are defined as a fixed-length 32-bit
   bitmask.  As networks grew and more use cases were introduced, the
   32-bit length was found to be constraining, and hence extended
   administrative groups (EAGs) were introduced in [RFC7308].

   The EAG TLV (Section 2) is not a replacement for the Administrative
   Group (color) TLV; as explained in [RFC7308], both values can
   coexist.  It is out of scope for this document to specify the
   behavior of the BGP-LS consumer [RFC7752].

   This document specifies an extension to BGP-LS for advertisement of
   the extended administrative groups.

1.1.  Requirements Language

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "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.  Advertising Extended Administrative Groups in BGP-LS

   This document defines an extension that enables BGP-LS speakers to
   signal the EAG of links in a network to a BGP-LS consumer of network
   topology such as a centralized controller.  The centralized
   controller can leverage this information in traffic engineering
   computations and other use cases.  When a BGP-LS speaker is
   originating the topology learned via link-state routing protocols
   like OSPF or IS-IS, the EAG information of the links is sourced from
   the underlying extensions as defined in [RFC7308].

   The EAG of a link is encoded in a new Link Attribute TLV [RFC7752]
   using the following format:

      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
     |              Type             |             Length            |
     |    Extended Administrative Group (variable)                  //

             Figure 1: Extended Administrative Group TLV Format


   Type:  1173

   Length:  variable length that represents the total length of the
      value field in octets.  The length value MUST be a multiple of 4.
      If the length is not a multiple of 4, the TLV MUST be considered

   Value:  one or more sets of 32-bit bitmasks that indicate the
      administrative groups (colors) that are enabled on the link when
      those specific bits are set.

3.  IANA Considerations

   IANA has assigned a code point from the "BGP-LS Node Descriptor, Link
   Descriptor, Prefix Descriptor, and Attribute TLVs" registry as
   described in the following table.

    | Code Point | Description                   | IS-IS TLV/Sub-TLV |
    | 1173       | Extended Administrative Group | 22/14             |

                                 Table 1

4.  Manageability Considerations

   The new protocol extensions introduced in this document augment the
   existing IGP topology information that is distributed via [RFC7752].
   Procedures and protocol extensions defined in this document do not
   affect the BGP protocol operations and management other than as
   discussed in Section 6 ("Manageability Considerations") of [RFC7752].
   Specifically, the tests for malformed attributes, to perform
   syntactic checks as described in Section 6.2.2 ("Fault Management")
   of [RFC7752], now encompass the new BGP-LS Attribute TLV defined in
   this document.  The semantic or content checking for the TLV
   specified in this document and its association with the BGP-LS
   Network Layer Reachability Information (NLRI) types or its BGP-LS
   Attribute are left to the consumer of the BGP-LS information (e.g.,
   an application or a controller) and not to BGP itself.

   A consumer of the BGP-LS information retrieves this information over
   a BGP-LS session (refer to Sections 1 and 2 of [RFC7752]).

5.  Security Considerations

   The procedures and protocol extensions defined in this document do
   not affect the BGP security model.  See the "Security Considerations"
   section of [RFC4271] for a discussion of BGP security.  This document
   only introduces a new Attribute TLV, and any syntactic error in it
   would result in the BGP-LS Attribute being discarded [RFC7752].
   Also, refer to [RFC4272] and [RFC6952] for analyses of security
   issues for BGP.  Security considerations for acquiring and
   distributing BGP-LS information are discussed in [RFC7752].  The TLV
   introduced in this document is used to propagate the EAG extensions
   defined in [RFC7308].  It is assumed that the IGP instances
   originating this TLV will support any required security mechanisms
   for OSPF and IS-IS, in order to prevent any security issues when
   propagating the Sub-TLVs into BGP-LS.

   Security concerns for OSPF are addressed in [RFC7474], [RFC4552], and
   [RFC7166].  Further security analysis for the OSPF protocol is done
   in [RFC6863].

   Security considerations for IS-IS are specified by [RFC5304].

   The advertisement of the link attribute information defined in this
   document presents no significant additional risk beyond that
   associated with the existing link attribute information already
   supported in [RFC7752].

6.  References

6.1.  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,

   [RFC7308]  Osborne, E., "Extended Administrative Groups in MPLS
              Traffic Engineering (MPLS-TE)", RFC 7308,
              DOI 10.17487/RFC7308, July 2014,

   [RFC7752]  Gredler, H., Ed., Medved, J., Previdi, S., Farrel, A., and
              S. Ray, "North-Bound Distribution of Link-State and
              Traffic Engineering (TE) Information Using BGP", RFC 7752,
              DOI 10.17487/RFC7752, March 2016,

   [RFC8174]  Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
              2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
              May 2017, <>.

6.2.  Informative References

   [RFC1195]  Callon, R., "Use of OSI IS-IS for routing in TCP/IP and
              dual environments", RFC 1195, DOI 10.17487/RFC1195,
              December 1990, <>.

   [RFC2328]  Moy, J., "OSPF Version 2", STD 54, RFC 2328,
              DOI 10.17487/RFC2328, April 1998,

   [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,

   [RFC4272]  Murphy, S., "BGP Security Vulnerabilities Analysis",
              RFC 4272, DOI 10.17487/RFC4272, January 2006,

   [RFC4552]  Gupta, M. and N. Melam, "Authentication/Confidentiality
              for OSPFv3", RFC 4552, DOI 10.17487/RFC4552, June 2006,

   [RFC5304]  Li, T. and R. Atkinson, "IS-IS Cryptographic
              Authentication", RFC 5304, DOI 10.17487/RFC5304, October
              2008, <>.

   [RFC5340]  Coltun, R., Ferguson, D., Moy, J., and A. Lindem, "OSPF
              for IPv6", RFC 5340, DOI 10.17487/RFC5340, July 2008,

   [RFC6863]  Hartman, S. and D. Zhang, "Analysis of OSPF Security
              According to the Keying and Authentication for Routing
              Protocols (KARP) Design Guide", RFC 6863,
              DOI 10.17487/RFC6863, March 2013,

   [RFC6952]  Jethanandani, M., Patel, K., and L. Zheng, "Analysis of
              BGP, LDP, PCEP, and MSDP Issues According to the Keying
              and Authentication for Routing Protocols (KARP) Design
              Guide", RFC 6952, DOI 10.17487/RFC6952, May 2013,

   [RFC7166]  Bhatia, M., Manral, V., and A. Lindem, "Supporting
              Authentication Trailer for OSPFv3", RFC 7166,
              DOI 10.17487/RFC7166, March 2014,

   [RFC7474]  Bhatia, M., Hartman, S., Zhang, D., and A. Lindem, Ed.,
              "Security Extension for OSPFv2 When Using Manual Key
              Management", RFC 7474, DOI 10.17487/RFC7474, April 2015,


   The authors would like to thank Eric Osborne, Les Ginsberg, Tim
   Chown, Ben Niven-Jenkins, and Alvaro Retana for their reviews and
   valuable comments.

Authors' Addresses

   Jeff Tantsura


   Zitao Wang
   Yuhua District
   101 Software Avenue
   Jiangsu, 210012


   Qin Wu
   Yuhua District
   101 Software Avenue
   Jiangsu, 210012


   Ketan Talaulikar
   Cisco Systems