Internet-Draft ISIS for BIER-TE July 2023
Chen, et al. Expires 7 January 2024 [Page]
Workgroup:
Network Working Group
Internet-Draft:
draft-ietf-bier-te-isis-08
Published:
Intended Status:
Standards Track
Expires:
Authors:
H. Chen
Futurewei
M. McBride
Futurewei
A. Wang
China Telecom
G. Mishra
Verizon Inc.
Y. Fan
Casa Systems
L. Liu
Fujitsu
X. Liu
Alef Edge

IS-IS Extensions for BIER-TE

Abstract

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

Requirements Language

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

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/.

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This Internet-Draft will expire on 7 January 2024.

Table of Contents

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.

[RFC8401] describes IS-IS Extensions for distributing the BFR identifier (BFR-id) configured on a BFR. This document specifies IS-IS 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 IS-IS

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

An Extended IS Reachability TLV (Type 22) defined in [RFC5305] may contain Sub-TLVs (such as those for TE) that apply to a link/interface to a neighbor. To encode multiple links or interfaces to neighbors, the structure inside TLV is repeated.

MT Intermediate Systems TLV (Type 222) defined in [RFC5120] may contain Sub-TLVs (such as those for TE) that apply to a link/interface. It is aligned with Extended IS Reachability TLV (Type 22) beside an additional two bytes in front at the beginning of the TLV for MT-ID.

Link-BP Sub-TLV of the following format is defined and used in Extended IS Reachability TLV (Type 22) and/or MT Intermediate Systems TLV (Type 222) to advertise a link BP.

Type:
TBD1 is to be assigned by IANA.
Length:
Variable, dependent on Sub-Sub-TLVs.
BAR, IPA and sub-domain-id:
They are defined in Section 6.1 of [RFC8401].
BitPosition:
A 2-octet field encoding the BitPosition locally configured on the link/interface to an Intermediate System neighbor.
DisEndBitPosition:
A 2-octet field encoding the BitPosition of the connection on the designated Intermediate Systems (Dis) end. This field exists when the neighbor is a pseudonode. If the neighbor is not a pseudonode, this field MUST NOT exist. The DisEndBitPosition 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].

No Sub-Sub-TLVs are currently defined.

2.2. Routed and Localdecap BitPositions

A Sub-TLV, called Node BPs Sub-TLV, is defined and carried within the TLVs 235, 237 [RFC5120], 135 [RFC5305], or 236 [RFC5308]. It contains Sub-Sub-TLVs. Two types of Sub-Sub-TLVs are defined. One is for a Routed BitPosition and the other for a Localdecap BitPosition. The Node BPs 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 (TBD2)   |    Length     |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |      BAR      |    IPA        | sub-domain-id |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                        Sub-Sub-TLVs                           ~
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 2: Node BPs Sub-TLV
Type:
TBD2 is to be assigned by IANA.
Length:
Variable.
BAR, IPA and sub-domain-id:
They are defined in Section 6.1 of [RFC8401].
Sub-Sub-TLVs:
They are Routed-BP Sub-Sub-TLVs for Routed BPs and/or Localdecap-BP Sub-Sub-TLV for Localdecap BP.

The Routed-BP Sub-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 3: Routed-BP Sub-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-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 (2)    |   Length(2)   |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |         BitPosition           |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 4: Localdecap-BP Sub-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 IS-IS security.

4. IANA Considerations

Under "IS-IS Sub-TLVs for TLVs Advertising Neighbor Information" registry, IANA is requested to assign a new Sub-TLV Type for Link BP as follows:

  +=======+=============+==+==+==+===+===+===+=============+
  | Type  |Description  |22|23|25|141|222|223|reference    |
  +=======+=============+==+==+==+===+===+===+=============+
  | TBD1  |  Link BP    |y |y |n | n | y | y |This document|
  +-------+-------------+--+--+--+---+---+---+-------------+

Under "IS-IS Sub-TLVs for TLVs Advertising Prefix Reachability" registry, IANA is requested to assign a new Sub-TLV Type for Node BPs as follows:

  +=======+=============+==+===+===+===+===+=============+
  | Type  |Description  |27|135|235|236|237|reference    |
  +=======+=============+==+===+===+===+===+=============+
  | TBD2  | Node BPs    |n | y | y | y | y |This document|
  +-------+-------------+--+---+---+---+---+-------------+

IANA is requested to create a new sub-registry "Sub-Sub-TLVs for Node BPs Sub-TLV" as follows:

  +==============+===================+=====================+
  |     Type     |      Name         |    reference        |
  +==============+===================+=====================+
  |     0        |                Reserved                 |
  +--------------+-------------------+---------------------+
  |     1        |   Routed BP       |    This document    |
  +--------------+-------------------+---------------------+
  |     2        |   Localdecap BP   |    This document    |
  +--------------+-------------------+---------------------+
  |     3 - 255  |                Unassigned               |
  +--------------+-------------------+---------------------+

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, , <https://www.rfc-editor.org/info/rfc2119>.
[RFC5120]
Przygienda, T., Shen, N., and N. Sheth, "M-ISIS: Multi Topology (MT) Routing in Intermediate System to Intermediate Systems (IS-ISs)", RFC 5120, DOI 10.17487/RFC5120, , <https://www.rfc-editor.org/info/rfc5120>.
[RFC5305]
Li, T. and H. Smit, "IS-IS Extensions for Traffic Engineering", RFC 5305, DOI 10.17487/RFC5305, , <https://www.rfc-editor.org/info/rfc5305>.
[RFC5308]
Hopps, C., "Routing IPv6 with IS-IS", RFC 5308, DOI 10.17487/RFC5308, , <https://www.rfc-editor.org/info/rfc5308>.
[RFC8174]
Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, , <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, , <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, , <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, , <https://www.rfc-editor.org/info/rfc8401>.

Acknowledgments

The authors would like to thank Acee Lindem, Les Ginsberg, Tony Przygienda, Jeffrey Zhang and Toerless Eckert for their comments on this work.

Authors' Addresses

Huaimo Chen
Futurewei
Boston, MA,
United States of America
Mike McBride
Futurewei
Aijun Wang
China Telecom
Beiqijia Town, Changping District
Beijing
102209
China
Gyan S. Mishra
Verizon Inc.
13101 Columbia Pike
Silver Spring, MD 20904
United States of America
Phone: 301 502-1347
Yanhe Fan
Casa Systems
United States of America
Lei Liu
Fujitsu
United States of America
Xufeng Liu
Alef Edge
United States of America