OSPFv2 Extensions for BIER-TE

Internet-Draft	OSPFv2 for BIER-TE	July 2023
Chen, et al.	Expires 6 January 2024	[Page]

Abstract

This document describes OSPFv2 extensions for distributing the BitPositions configured on a Bit-Forwarding Router (BFR) in a "Bit Index Explicit Replication Traffic Engineering" (BIER-TE) domain.¶

Status of This Memo

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1. Introduction

[RFC9262] introduces Bit Index Explicit Replication (BIER) Traffic/Tree Engineering (BIER-TE). It is an architecture for per-packet stateless explicit point to multipoint (P2MP) multicast path/tree. There are three types of BitPositions (BPs) in a BIER-TE domain: link BitPosition (BP), routed BP and localdecap BP. A link BP is a BP configured on a link from Bit-Forwarding Router (BFR) X to BFR Y for a forward connected adjacency from X to Y. A routed BP is a BP configured on BFR X for a forward routed adjacency from X to a remote BFR Z not directly connected to X. A localdecap BP is a BP configured on a BFR.¶

[RFC8444] describes OSPFv2 Extensions for distributing the BFR identifier (BFR-id) configured on a BFR. This document specifies OSPFv2 extensions for distributing the BitPositions configured a BFR in a BIER-TE domain. The BitPositions distributed may be used by a BFR as a Point of Local Repair (PLR) for Fast-ReRoute (FRR).¶

2. Extensions to OSPFv2

This section describes protocol extensions to OSPFv2 for distributing the BitPositions configured on a BFR in a BIER-TE domain.¶

2.1. Link BitPosition

This section defines a Sub-TLV for distributing a link BitPosition (BP).¶

[RFC7684] defines the OSPFv2 Extended Link TLV to advertise the information about a link. Multiple Link TLVs for the links of a router are included in the OSPFv2 Extended Link Opaque LSA of the router. The OSPFv2 Extended Link TLV has 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 (1)           |      Length (Variable)        |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |   Link Type   |                    Reserved                   |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                             Link ID                           |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                            Link Data                          |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                       Sub-TLVs (variable)                     |
   ~                                                               ~
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

Figure 1: OSPFv2 Extended Link TLV

Type:: 1.¶
Length:: Variable, dependent on Sub-TLVs.¶
Link Type, Link ID and Link Data:: They are defined in Section A.4.2 of [RFC2328].¶
Reserved:: MUST be set to 0 on transmission and MUST be ignored on reception.¶

Under the OSPFv2 Extended Link TLV for a link, a Sub-TLV, called Link-BP Sub-TLV, is defined for distributing a link BitPosition. A Link-BP Sub-TLV is included in the Link TLV for a link of Link Type P2P (Point-to-Point) or Broadcast (or say LAN or Transit Network). The Link-BP Sub-TLV has 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 (TBD1)          |            Length             |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   | sub-domain-id |     MT-ID     |      BAR      |    IPA        |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |         BitPosition           |         DrEndBitPosition      |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

Figure 2: Link-BP Sub-TLV

Type:: TBD1 is to be assigned by IANA.¶
Length:: Variable.¶
sub-domain-id, MT-ID, BAR and IPA:: They are defined in Section 2.1 of [RFC8444].¶
BitPosition:: A 2-octet field encoding the BitPosition locally configured on the link/interface when the Link Type of the link in the OSPFv2 Extended Link TLV containing this Sub-TLV is 1 (i.e., Point-to-Point connection to another router) or 2 (i.e., connection to Transit Network or say LAN).¶
DrEndBitPosition:: A 2-octet field encoding the BitPosition of the connection on the designated router (DR) end. This field exists when the Link Type in the OSPFv2 Extended Link TLV containing this Sub-TLV is 2 (i.e., Transit Network or LAN). For the other value of the Link Type, this field MUST NOT exist. The DrEndBitPosition may be configured on the link/interface to a transit network (i.e., broadcast link or say LAN) as described in [I-D.chen-bier-te-lan].¶

2.2. Routed and Localdecap BitPositions

A TLV, called Node BPs TLV, is defined within the body of the OSPF Router Information (RI) Opaque Link State Advertisement (LSA) [RFC7770]. The TLV contains Sub-TLVs. Two types of Sub-TLVs are defined. One is for a Routed BitPosition and the other for a Localdecap BitPosition.¶

The Node BPs TLV has 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 (TBD2)          |            Length             |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   | sub-domain-id |     MT-ID     |      BAR      |    IPA        |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                            Sub-TLVs                           ~
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

Figure 3: Node BPs TLV

Type:: TBD2 is to be assigned by IANA.¶
Length:: Variable.¶
sub-domain-id, MT-ID, BAR and IPA:: They are defined in Section 2.1 of [RFC8444].¶
Sub-TLVs:: They are Routed-BP Sub-TLVs for Routed BPs and/or Localdecap-BP Sub-TLV for Localdecap BP.¶

The Routed-BP Sub-TLV has 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 (1)            |           Length(4)           |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |         BitPosition           |             BFR-id            |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

Figure 4: Routed-BP Sub-TLV

Type:: 1 is the type for routed BP.¶
Length:: It is 4.¶
BitPosition:: A 2-octet field encoding the BitPosition configured on a BFR for a forward routed adjacency to a remote BFR.¶
BFR-id:: A 2-octet field encoding the BFR-id of the remote BFR.¶

The Localdecap-BP Sub-TLV has 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 (T2)           |           Length(2)           |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |         BitPosition           |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

Figure 5: Localdecap-BP Sub-TLV

Type:: 2 is the type for localdecap BP.¶
Length:: It is 2.¶
BitPosition:: A 2-octet field encoding the localdecap BitPosition configured on a BFR.¶

3. Security Considerations

Protocol extensions defined in this document do not affect the OSPF security other than those as discussed in the Security Considerations section of [RFC7684].¶

4. IANA Considerations

Under "OSPFv2 Extended Link TLV Sub-TLVs" registry as defined in [RFC7684], IANA is requested to assign a new registry value for Link-BP Sub-TLV as follows:¶

  +==============+===================+=====================+
  |  Value       |  Description      |    reference        |
  +==============+===================+=====================+
  |  TBD1 (25)   |  Link-BP          |    This document    |
  +--------------+-------------------+---------------------+

Under "OSPF Router Information (RI) TLVs" registry as defined in [RFC7770], IANA is requested to assign a new registry value for Node BPs TLV as follows:¶

  +==============+===================+=====================+
  |  Value       |  Description      |    reference        |
  +==============+===================+=====================+
  |  TBD2 (21)   |  Node BPs         |    This document    |
  +--------------+-------------------+---------------------+

IANA is requested to create a new subregistry called the "OSPF Node BPs Sub-TLVs" under the "Open Shortest Path First (OSPF) Parameters" registry. The initial values are as follows:¶

  +===========+===================+========================+
  |  Value    |  Description      |    reference           |
  +===========+===================+========================+
  |    0      |  Reserved         |    This document       |
  +-----------+-------------------+------------------------+
  |    1      |  Routed BP        |    This document       |
  +-----------+-------------------+------------------------+
  |    2      |  Localdecap BP    |    This document       |
  +-----------+-------------------+------------------------+
  | 3 - 65535 |  To be allocated in First Come First Served|
  +-----------+-------------------+------------------------+

5. References

5.1. 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>.
[RFC2328]: Moy, J., "OSPF Version 2", STD 54, RFC 2328, DOI 10.17487/RFC2328, April 1998, <https://www.rfc-editor.org/info/rfc2328>.
[RFC7684]: Psenak, P., Gredler, H., Shakir, R., Henderickx, W., Tantsura, J., and A. Lindem, "OSPFv2 Prefix/Link Attribute Advertisement", RFC 7684, DOI 10.17487/RFC7684, November 2015, <https://www.rfc-editor.org/info/rfc7684>.
[RFC7770]: Lindem, A., Ed., Shen, N., Vasseur, JP., Aggarwal, R., and S. Shaffer, "Extensions to OSPF for Advertising Optional Router Capabilities", RFC 7770, DOI 10.17487/RFC7770, February 2016, <https://www.rfc-editor.org/info/rfc7770>.
[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>.
[RFC9262]: Eckert, T., Ed., Menth, M., and G. Cauchie, "Tree Engineering for Bit Index Explicit Replication (BIER-TE)", RFC 9262, DOI 10.17487/RFC9262, October 2022, <https://www.rfc-editor.org/info/rfc9262>.

5.2. Informative References

[I-D.chen-bier-te-lan]: Chen, H., McBride, M., Wang, A., Mishra, G. S., Liu, L., and X. Liu, "BIER-TE for Broadcast Link", Work in Progress, Internet-Draft, draft-chen-bier-te-lan-06, 9 March 2023, <https://datatracker.ietf.org/doc/html/draft-chen-bier-te-lan-06>.
[RFC8401]: Ginsberg, L., Ed., Przygienda, T., Aldrin, S., and Z. Zhang, "Bit Index Explicit Replication (BIER) Support via IS-IS", RFC 8401, DOI 10.17487/RFC8401, June 2018, <https://www.rfc-editor.org/info/rfc8401>.
[RFC8444]: Psenak, P., Ed., Kumar, N., Wijnands, IJ., Dolganow, A., Przygienda, T., Zhang, J., and S. Aldrin, "OSPFv2 Extensions for Bit Index Explicit Replication (BIER)", RFC 8444, DOI 10.17487/RFC8444, November 2018, <https://www.rfc-editor.org/info/rfc8444>.