Internet-Draft OSPF for BIER-TE July 2021
Chen, et al. Expires 28 January 2022 [Page]
Network Working Group
Intended Status:
Standards Track
H. Chen
M. McBride
A. Wang
China Telecom
G. Mishra
Verizon Inc.
Y. Fan
Casa Systems
L. Liu
X. Liu
Volta Networks

OSPF Extensions for BIER-TE


This document describes OSPF extensions for distributing BitPositions configured on the links in "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

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 28 January 2022.

1. Introduction

[I-D.ietf-bier-te-arch] 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. A link in a BIER-TE domain has its BitPositions. For a link between two nodes X and Y, there are two BitPositions for two forward connected adjacencies. These two adjacency BitPositions could be configured on nodes X and Y respectively. The BitPosition configured on X is the forward connected adjacency of Y. The BitPosition configured on Y is the forward connected adjacency of X.

This document proposes OSPF extensions for distributing BitPositions configured on the links in "Bit Index Explicit Replication Traffic Engineering" (BIER-TE) domain.

1.1. Terminology

Bit Index Explicit Replication.
BIER Traffic Engineering.
Bit-Forwarding Router.
Bit-Forwarding Ingress Router.
Bit-Forwarding Egress Router.
BFR Identifier. It is a number in the range [1,65535].
BFR Neighbor.
Link State Advertisement.
Open Shortest Path First.

2. Extensions to OSPFv2

This section describes protocol extensions to OSPFv2 for distributing BIER-TE information such as the BitPositions configured on the links in a BIER-TE domain.

[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:

Variable, dependent on Sub-TLVs.
Link Type, Link ID and Link Data:
They are defined in Section A.4.2 of [RFC2328].
SHOULD 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 BIER-TE Sub-TLV, is defined for distributing BIER-TE information about the link. A BIER-TE Sub-TLV is included in the Link TLV for a link of Link Type Point-to-Point or Broadcast (or say LAN or Transit Network). The BIER-TE 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: BIER-TE Sub-TLV
TBD1 is to be assigned by IANA.
8 (octets).
Unique value identifying a BIER-TE sub-domain.
Multi-Topology ID identifying the topology that is associated with the BIER-TE sub-domain.
Single-octet BIER Algorithm used to calculate underlay paths to reach other BFRs. Values are allocated from the "BIER Algorithm" registry defined in [RFC8401].
Single-octet IGP Algorithm used to either modify, enhance, or replace the calculation of underlay paths to reach other BFRs as defined by the BAR value. Values are defined in the "IGP Algorithm Types" registry.
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).
A 2-octet field encoding the BitPosition of the connection on the designated router (DR) end. This field is valid 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 be ignored. The DrEndBitPosition may be configured on the link/interface to a transit network (i.e., broadcast link or say LAN).

Note that if each of BitPosition and DrEndBitPosition uses more than 2 octets, we use 4 or more octets for each of them.

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 BIER-TE Sub-TLV as follows:

  |  Value       |  Description      |    reference        |
  |  TBD1 (25)   |  BIER-TE          |    This document    |

5. Acknowledgements

The authors would like to thank Acee Lindem and Tony Przygienda for their comments on this work.

6. References

6.1. Normative References

Eckert, T., Cauchie, G., and M. Menth, "Tree Engineering for Bit Index Explicit Replication (BIER-TE)", Work in Progress, Internet-Draft, draft-ietf-bier-te-arch-10, , <>.
Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/RFC2119, , <>.
Moy, J., "OSPF Version 2", STD 54, RFC 2328, DOI 10.17487/RFC2328, , <>.
Narten, T. and H. Alvestrand, "Guidelines for Writing an IANA Considerations Section in RFCs", RFC 5226, DOI 10.17487/RFC5226, , <>.
Psenak, P., Gredler, H., Shakir, R., Henderickx, W., Tantsura, J., and A. Lindem, "OSPFv2 Prefix/Link Attribute Advertisement", RFC 7684, DOI 10.17487/RFC7684, , <>.
Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, , <>.
Wijnands, IJ., Ed., Rosen, E., Ed., Dolganow, A., Przygienda, T., and S. Aldrin, "Multicast Using Bit Index Explicit Replication (BIER)", RFC 8279, DOI 10.17487/RFC8279, , <>.
Lindem, A., Roy, A., Goethals, D., Reddy Vallem, V., and F. Baker, "OSPFv3 Link State Advertisement (LSA) Extensibility", RFC 8362, DOI 10.17487/RFC8362, , <>.

6.2. Informative References

Berger, L., Bryskin, I., Zinin, A., and R. Coltun, "The OSPF Opaque LSA Option", RFC 5250, DOI 10.17487/RFC5250, , <>.
Wijnands, IJ., Ed., Rosen, E., Ed., Dolganow, A., Tantsura, J., Aldrin, S., and I. Meilik, "Encapsulation for Bit Index Explicit Replication (BIER) in MPLS and Non-MPLS Networks", RFC 8296, DOI 10.17487/RFC8296, , <>.
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, , <>.
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, , <>.
Rosen, E., Ed., Sivakumar, M., Przygienda, T., Aldrin, S., and A. Dolganow, "Multicast VPN Using Bit Index Explicit Replication (BIER)", RFC 8556, DOI 10.17487/RFC8556, , <>.

Authors' Addresses

Huaimo Chen
Boston, MA,
United States of America
Mike McBride
Aijun Wang
China Telecom
Beiqijia Town, Changping District
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
United States of America
Xufeng Liu
Volta Networks
McLean, VA
United States of America