BGP-LS Extensions for IS-IS Flood Reflection
draft-ietf-idr-bgp-ls-isis-flood-reflection-04

Inter-Domain Routing                                        J. Head, Ed.
Internet-Draft                                             T. Przygienda
Intended status: Experimental                           Juniper Networks
Expires: 12 August 2024                                  9 February 2024

              BGP-LS Extensions for IS-IS Flood Reflection
             draft-ietf-idr-bgp-ls-isis-flood-reflection-04

Abstract

   IS-IS Flood Reflection is a mechanism that allows flat, single-area
   IS-IS topologies to scale beyond their traditional limitations.

   This document defines new BGP-LS (BGP Link-State) TLVs in order to
   carry IS-IS Flood Reflection information.

Status of This Memo

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   This Internet-Draft will expire on 12 August 2024.

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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
     1.1.  Requirements Language . . . . . . . . . . . . . . . . . .   2
   2.  BGP-LS Extensions for IS-IS Flood Reflection  . . . . . . . .   2
     2.1.  IS-IS Flood Reflection TLV  . . . . . . . . . . . . . . .   3
   3.  Design Considerations . . . . . . . . . . . . . . . . . . . .   3
   4.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   4
     4.1.  Requested TLV Entries . . . . . . . . . . . . . . . . . .   4
   5.  Security Considerations . . . . . . . . . . . . . . . . . . .   4
   6.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .   5
   7.  References  . . . . . . . . . . . . . . . . . . . . . . . . .   5
     7.1.  Normative References  . . . . . . . . . . . . . . . . . .   5
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .   6

1.  Introduction

   IS-IS Flood Reflection [RFC9377] is a mechanism that allows flat,
   single-area IS-IS topologies to scale beyond their existing
   limitations.

   Flood Reflection topologies are broken into clusters.  The
   participating nodes must convey their unique Cluster ID signifying
   their membership in a particular topology as well as their role (e.g.
   Flood Reflector or Client).

   BGP Link-State RFC9552 [RFC9552] defines mechanisms to advertise
   information about the underlying IGP in BGP NLRI to an external
   entity (e.g. a controller).  A new BGP-LS TLV is required in order to
   describe IS-IS Flood Reflection node and link details.  This document
   defines that TLV.

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.  BGP-LS Extensions for IS-IS Flood Reflection

   Controllers may need to compute traffic engineered paths across Flood
   Reflection clusters.  This requires that they be aware of Flood
   Reflection information (be it operational or configured), such as
   Cluster ID, C-bit (which indicates Flood Reflector or Client), and
   any applicable sub-TLVs.

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   The IS-IS Flood Reflection TLV can be advertised in BGP-LS as either
   a Node attribute or a Link attribute.  When describing a node, values
   are derived from the IS-IS Flood Reflection Discovery Sub-TLV.  When
   describing a link, values are derived from the IS-IS Adjacency Sub-
   TLV.  The semantics of any fields within the TLV/sub-TLVs are
   described in [RFC9377].

   This document defines the following BGP-LS TLVs for use with IS-IS
   Flood Reflection.

      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            |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |C|  RESERVED   |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                  Flood Reflection Cluster ID                  |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                          Sub-TLVs ...                         |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                    Figure 1: IS-IS Flood Reflection TLV

2.1.  IS-IS Flood Reflection TLV

   This section defines a BGP-LS Attribute that corresponds to IS-IS
   Flood Reflection TLVs/sub-TLVs as described in [RFC9377]

   where:

      *Type:*  1160

      *Length:*  variable

3.  Design Considerations

   It is typical that a BGP-LS extension mirror all of the corresponding
   IGP components (i.e.  TLVs, sub-TLVs, and sub-sub-TLVs) in order to
   carry the necessary IGP information.  IS-IS Flood Reflection
   [RFC9377] describes "Tunnel-Based" deployments where an optional
   "Flood Reflection Discovery Tunnel Type Sub-Sub-TLV" is used to
   facilitate the creation of "L1 Shortcuts" (i.e. tunnels) between
   nodes in a Flood Reflection cluster.  In this document, it is
   RECOMMENDED that this sub-sub-TLV be excluded from the BGP-LS
   extension for the following reasons.

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   For example, shortcuts could be point-to-point IS-IS tunnels or be
   encapsulated by other means.  In deployments where the tunnels are
   IS-IS based, no additional BGP-LS extension is required as the
   existing BGP-LS extensions for IS-IS will suffice.

   However, for deployments where tunnels are encapsulated by other
   means it is not desirable for BGP-LS to carry that information as it
   is tunnel information and not IGP information.  Other existing or new
   BGP-LS extensions that correspond to the particular tunnel type
   SHOULD be used to fulfill any BGP-LS requirements.

   An implementation MAY still choose to include the "Flood Reflection
   Discovery Tunnel Type Sub-Sub-TLV" for the sake of completeness.  For
   example, it might be beneficial for cases where BGP-LS is the only
   way this information can be obtained.

4.  IANA Considerations

   This section requests the following values from the "BGP-LS Node
   Descriptor, Link Descriptor, Prefix Descriptor, and Attribute TLVs"
   registry for the following TLVs:

4.1.  Requested TLV Entries

   +=======+=============+================================+===========+
   | TLV   | Description | IS-IS TLV/Sub-TLV              | Reference |
   | Code  |             |                                |           |
   | Point |             |                                |           |
   +=======+=============+================================+===========+
   | 1160  | IS-IS Flood | (22|23|25|141|222|223|242)/161 | This      |
   |       | Reflection  |                                | document. |
   +-------+-------------+--------------------------------+-----------+

                      Table 1: Requested TLV Entries

5.  Security Considerations

   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.  Also, refer
   to [RFC4272] and [RFC6952] for analyses of BGP security issues.
   Security considerations for acquiring and distributing BGP-LS
   information are discussed in [RFC9552].

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   The TLVs introduced in this document are used to propagate IS-IS
   Flood Reflection TLVs defined in [RFC9377].  These TLVs represent IS-
   IS Flood Reflection state and are therefore assumed to support any/
   all of the required security and authentication mechanisms as
   described in [RFC9377] to prevent any security issues when
   propagating the TLVs into BGP-LS.

6.  Acknowledgements

   The authors would like to thank Ketan Talaulikar for several
   iterations of review and practical suggestions.

7.  References

7.1.  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., Li, T., and S. Hares, "A Border Gateway
              Protocol 4 (BGP-4)", January 2006,
              <https://www.rfc-editor.org/info/rfc4271>.

   [RFC4272]  Murphy, S., "BGP Security Vulnerabilities Analysis",
              January 2006, <https://www.rfc-editor.org/info/rfc4272>.

   [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", May 2013,
              <https://www.rfc-editor.org/info/rfc6952>.

   [RFC8126]  Cotton, M., Leiba, B., and T. Narten, "Guidelines for
              Writing an IANA Considerations Section in RFCs", June
              2017, <https://www.rfc-editor.org/info/rfc8126>.

   [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>.

   [RFC9377]  Przygienda, T., Ed., Bowers, C., Lee, Y., Sharma, A., and
              R. White, "IS-IS Flood Reflection", RFC 9377,
              DOI 10.17487/RFC9377, April 2023,
              <https://www.rfc-editor.org/info/rfc9377>.

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   [RFC9552]  Talaulikar, K., "Distribution of Link-State and Traffic
              Engineering Information Using BGP", January 2024,
              <https://www.rfc-editor.org/info/rfc9552>.

Authors' Addresses

   Jordan Head (editor)
   Juniper Networks
   1137 Innovation Way
   Sunnyvale, CA
   United States of America
   Email: jhead@juniper.net

   Tony Przygienda
   Juniper Networks
   1137 Innovation Way
   Sunnyvale, CA
   United States of America
   Email: prz@juniper.net

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