BGP Link-State extensions for BIER
draft-ietf-bier-bgp-ls-bier-ext-20
| Document | Type | Active Internet-Draft (bier WG) | |
|---|---|---|---|
| Authors | Ran Chen , Zheng Zhang , Vengada Prasad Govindan , IJsbrand Wijnands , Zhaohui (Jeffrey) Zhang | ||
| Last updated | 2025-06-03 | ||
| RFC stream | Internet Engineering Task Force (IETF) | ||
| Intended RFC status | (None) | ||
| Formats | |||
| Additional resources | Mailing list discussion | ||
| Stream | WG state | In WG Last Call | |
| Document shepherd | Gyan Mishra | ||
| Shepherd write-up | Show Last changed 2020-11-03 | ||
| IESG | IESG state | I-D Exists | |
| Consensus boilerplate | Unknown | ||
| Telechat date | (None) | ||
| Responsible AD | (None) | ||
| Send notices to | Gyan Mishra <hayabusagsm@gmail.com> |
draft-ietf-bier-bgp-ls-bier-ext-20
BIER Working Group R. Chen
Internet-Draft Z. Zhang
Intended status: Standards Track ZTE Corporation
Expires: 4 December 2025 V. Govindan
Cisco
IJ. Wijnands
Individual
Z. Zhang
Juniper Networks
2 June 2025
BGP Link-State extensions for BIER
draft-ietf-bier-bgp-ls-bier-ext-20
Abstract
Bit Index Explicit Replication (BIER) is an architecture that
provides optimal multicast forwarding through a "BIER domain" without
requiring intermediate routers to maintain any multicast related per-
flow state. BIER also does not require any explicit tree-building
protocol for its operation. A multicast data packet enters a BIER
domain at a "Bit-Forwarding Ingress Router" (BFIR), and leaves the
BIER domain at one or more "Bit-Forwarding Egress Routers" (BFERs).
The BFIR router adds a BIER header to the packet. The BIER header
contains a bitstring in which each bit represents exactly one BFER to
forward the packet to. The set of BFERs to which the multicast
packet needs to be forwarded is expressed by setting the bits that
correspond to those routers in the BIER header.
BGP Link-State (BGP-LS) enables the collection of various topology
informations from the network, and the topology informations are used
by the controller to calculate the fowarding tables and then
propagate them onto the BFRs(instead of having each node to calculate
on its own) and that can be for both inter-as and intra-as
situations.
This document specifies extensions to the BGP Link-state address-
family in order to advertise the BIER informations.
Status of This Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
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Internet-Drafts are working documents of the Internet Engineering
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working documents as Internet-Drafts. The list of current Internet-
Drafts is at https://datatracker.ietf.org/drafts/current/.
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 4 December 2025.
Copyright Notice
Copyright (c) 2025 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents (https://trustee.ietf.org/
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Please review these documents carefully, as they describe your rights
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provided without warranty as described in the Revised BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
1.1. Requirements Language . . . . . . . . . . . . . . . . . . 3
2. BGP-LS Extensions for BIER . . . . . . . . . . . . . . . . . 3
2.1. Prefix Attributes TLVs . . . . . . . . . . . . . . . . . 4
2.2. The BIER information TLV . . . . . . . . . . . . . . . . 4
2.3. The BIER MPLS Encapsulation TLV . . . . . . . . . . . . . 5
2.4. The BIER non-MPLS Encapsulation TLV . . . . . . . . . . . 6
3. Equivalent IS-IS BIER TLVs/Sub-TLVs . . . . . . . . . . . . . 7
4. Equivalent OSPFv2/OSPFV3 BIER TLVs/Sub-TLVs . . . . . . . . . 7
5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 8
6. Security Considerations . . . . . . . . . . . . . . . . . . . 8
7. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 9
8. References . . . . . . . . . . . . . . . . . . . . . . . . . 9
8.1. Normative References . . . . . . . . . . . . . . . . . . 9
8.2. Informative References . . . . . . . . . . . . . . . . . 10
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 11
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1. Introduction
Bit Index Explicit Replication (BIER) is an architecture that
provides optimal multicast forwarding through a "BIER domain" without
requiring intermediate routers to maintain any multicast related per-
flow state. BIER also does not require any explicit tree-building
protocol for its operation. A multicast data packet enters a BIER
domain at a "Bit-Forwarding Ingress Router" (BFIR), and leaves the
BIER domain at one or more "Bit-Forwarding Egress Routers" (BFERs).
The BFIR router adds a BIER header to the packet. The BIER header
contains a bitstring in which each bit represents exactly one BFER to
forward the packet to. The set of BFERs to which the multicast
packet needs to be forwarded are expressed by setting the bits that
correspond to those routers in the BIER header.
The BGP-LS address-family/sub-address-family have been defined to
allow BGP to carry Link-State informations. This document specifies
extensions to the BGP Link-state address-family in order to advertise
BIER-specific informations, Similar to BGP-LS Advertisement of IGP
Traffic Engineering Performance Metric Extensions([RFC8571]). An
external component (e.g., a controller/a PCE(see [RFC4655] for PCE-
Based Architecture ,[RFC5440] for PCEP and [RFC5376] for Inter-AS
Requirements for the PCEP.))then can learn the BIER informations in
the "northbound" direction and calculate BIRT/BIFT and then propagate
them onto BFRs (instead of having each BFR to calculate on its own),
and that can be for both inter-as and intra-as situations.
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 BIER
[RFC8279] defines the BFR - A router that supports BIER is known as a
"Bit-Forwarding Router"(BFR), and each BFR MUST be assigned a "BFR-
Prefix". A BFR's Prefix MUST be an IP address (either IPv4 or IPv6)
of the BFR, and MUST be unique and routable within the BIER domain as
described in section 2 of [RFC8279], and then external component
(e.g., a controller) need to collect BIER informations of BIER
routers are associated with the BFR-Prefix in the "northbound"
direction within the BIER domain.
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Given that the BIER informations are associated with the prefix, the
Prefix Attribute TLV [RFC9552] can be used to carry the BIER
informations. The new Prefix Attribute TLVs are defined for the
encoding of BIER informations.
2.1. Prefix Attributes TLVs
The following Prefix Attribute TLVs are defined:
+======+=============================+=============+
| Type | Description | Section |
+======+=============================+=============+
| TBD1 | BIER information | section 3.2 |
+------+-----------------------------+-------------+
| TBD2 | BIER MPLS Encapsulation | section 3.3 |
+------+-----------------------------+-------------+
| TBD3 | BIER non-MPLS Encapsulation | section 3.4 |
+------+-----------------------------+-------------+
Table 1: The new Prefix Attribute TLVs
2.2. The BIER information TLV
A new Prefix Attribute TLV (defined in [RFC9552] is defined for
distributing BIER informations. The new TLV is called the BIER
information TLV. The BIER information TLV may appear multiple times.
The following BIER information TLV is defined:
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 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| subdomain-id | BFR-ID | Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| BAR | IPA | Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 1: The BIER information TLV
Type: A 2-octet field with value TBD, see IANA Considerations
section.
Length: 2 octets.
Subdomain-id: Unique value identifying the BIER sub-domain, 1 octet.
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BFR-ID: A 2-octet field encoding the BFR-ID, as documented in
[RFC8279]. If the BFR-ID is zero, it means, the advertising router
is not advertising any BIER-id.In some environment, BFR-ID can be
configured by NMS, The BFR-ID should be sent to a controller.
BAR: A 1-octet field encoding the BIER Algorithm, used to calculate
underlay paths to reach BFERs. Values are allocated from the "BIER
Algorithms" registry which are defined in [RFC8401], [RFC8444]and
[I-D.ietf-bier-ospfv3-extensions].
IPA: A 1-octet field encoding the IGP Algorithm, used to either
modify,enhance, or replace the calculation of underlay paths to reach
BFERs as defined by the BAR value. Values are from the "IGP
Algorithm" registry.
Reserved: MUST be 0 on transmission, ignored on reception. May be
used in future versions.
2.3. The BIER MPLS Encapsulation TLV
The BIER MPLS Encapsulation TLV is used in order to advertise MPLS
specific informations used for BIER. It MAY appear multiple times.
In some environment, each router allocates its labels, and advertises
it to the controller. That solution is simpler as the controller
does not need to deal with label allocation. If the controller has
to deal with Label allocation , there needs to be a (global) range
carved out such there are no conflicts. We can avoid all that by
having the router allocate the BIER Label range and advertise it to
the controller.
The following the BIER MPLS Encapsulation Sub-TLV is defined:
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 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Max SI |BS Len | Label |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 2: The BIER MPLS Encapsulation TLV
Type: A 2-octet field with value TBD, see IANA Considerations
section.
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Length: 2 octets.
Max SI: A 1-octet field encoding the maximum Set Identifier(as
defined in [RFC8279]), used in the encapsulation for this BIER
subdomain for this BitString length.
Label: First label of the range, 20 bits. The labels are as defined
in [RFC8296].
BS Len: A 4-bit field field encoding the Bitstring length as per
[RFC8296].
BS length in multiple BIER MPLS Encapsulation Sub-TLV associated with
the same BIER Sub-TLV MUST NOT repeat, otherwise only the first BIER
MPLS Encapsulation Sub-TLV with such BS length MUST be used and any
subsequent BIER MPLS Encapsulation Sub-TLVs with the same BS length
MUST be ignored.
2.4. The BIER non-MPLS Encapsulation TLV
The BIER non-MPLS Encapsulation TLV is used in order to advertise
non-MPLS encapsulation(e.g. ethernet encapsulation ) capability and
other associated parameters of the encapsulation.It MAY appear
multiple times.
The following the BIER non-MPLS Encapsulation Sub-TLV is defined:
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 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Max SI |BS Len | BIFT-id |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 3: The BIER non-MPLS Encapsulation TLV
Type: A 2-octet field with value TBD, see IANA Considerations
section.
Length: 2 octets.
Max SI: A 1-octet field encoding the maximum Set Identifier(as
defined in [RFC8279]), used in the encapsulation for this BIER
subdomain for this BitString length.
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BIFT-id: A 20 bit field encoding the first BIFT-id of the BIFT-id
range.
The "BIFT-id range" is the set of 20-bit values beginning with the
BIFT-id and ending with (BIFT-id + (Max SI)). A unique BIFT-id range
is allocated for each BitString length and sub-domain-id. These
BIFT-id's are used for BIER forwarding as described in [RFC8279])and
[RFC8296].
Local BitString Length (BS Len): A 4-bit field encoding the Bitstring
length as per [RFC8296].
Reserved:SHOULD be set to 0 on transmission and MUST be ignored on
reception.
3. Equivalent IS-IS BIER TLVs/Sub-TLVs
This section illustrates the IS-IS BIER Extensions Sub-TLVs/Sub-Sub-
TLVs mapped to the ones defined in this document.
The following table illustrates for each BGP-LS TLV, and its
equivalence in IS-IS.
+=============+=============+=======================================+
| Description | IS-IS TLV/ | Reference |
| | Sub-TLV | |
+=============+=============+=======================================+
| BIER | BIER info | [RFC8401] |
| information | Sub-TLV | |
+-------------+-------------+---------------------------------------+
| BIER MPLS | BIER MPLS | [RFC8401] |
|Encapsulation|Encapsulation| |
| | Sub-Sub-TLV | |
+-------------+-------------+---------------------------------------+
|BIER non-MPLS|BIER non-MPLS|[I-D.ietf-bier-lsr-non-mpls-extensions]|
|Encapsulation|Encapsulation| |
| | Sub-Sub-TLV | |
+-------------+-------------+---------------------------------------+
Table 2: IS-IS BIER Extensions Sub-TLVs/Sub-Sub-TLVs
4. Equivalent OSPFv2/OSPFV3 BIER TLVs/Sub-TLVs
This section illustrates the BIER Extensions TLVs/Sub-TLVs mapped to
the ones defined in this document.
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The following table illustrates for each BGP-LS TLV, and its
equivalence in OSPFv2/OSPFV3.
+=============+=============+=======================================+
| Description |OSPFv2/OSPFV3| Reference |
| | sub-TLV/Sub-| |
| | Sub-TLV | |
+=============+=============+=======================================+
| BIER | BIER Sub-TLV|[RFC8444], |
| information | |[I-D.ietf-bier-ospfv3-extensions] |
+-------------+-------------+---------------------------------------+
| BIER MPLS | BIER MPLS |[RFC8444], |
|Encapsulation|Encapsulation|[I-D.ietf-bier-ospfv3-extensions] |
| | Sub-TLV | |
+-------------+-------------+---------------------------------------+
|BIER non-MPLS|BIER non-MPLS|[I-D.ietf-bier-lsr-non-mpls-extensions]|
|Encapsulation|Encapsulation| |
| | Sub-TLV | |
+-------------+-------------+---------------------------------------+
Table 3: OSPFv2/OSPFV3 BIER TLVs/Sub-TLVs
5. IANA Considerations
IANA maintains a registry group called "Border Gateway Protocol -
Link State (BGP-LS) Parameters" with a registry called "BGP-LS NLRI
and Attribute TLVs". The following TLV codepoints are suggested (for
early allocation by IANA):
+============+=============================+==================+
| Code Point | Description | Value defined in |
+============+=============================+==================+
| TBD1 | BIER information | this document |
+------------+-----------------------------+------------------+
| TBD2 | BIER MPLS Encapsulation | this document |
+------------+-----------------------------+------------------+
| TBD3 | BIER non-MPLS Encapsulation | this document |
+------------+-----------------------------+------------------+
Table 4: The new Prefix Attribute TLVs
6. 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.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 the Bit
Index Explicit Replication (BIER) defined in [RFC8401], [RFC8444] ,
[I-D.ietf-bier-ospfv3-extensions], and
[I-D.ietf-bier-lsr-non-mpls-extensions]. These TLVs represent the
bier information associated with the prefix. It is assumed that the
IGP instances originating these TLVs will support all the required
security and authentication mechanisms in [RFC8401], [RFC8444],
[I-D.ietf-bier-ospfv3-extensions] ,and
[I-D.ietf-bier-lsr-non-mpls-extensions] in order to prevent any
security issues when propagating the TLVs into BGP-LS. The
advertisement of the link attribute information defined in this
document present no additional risk beyond that associated with the
existing link attribute informations already supported in [RFC9552].
7. Acknowledgments
The authors thank Peter Psenak, Ketan Talaulikar, Gyan Mishra and
Benchong Xu and many others for their suggestions and comments.
8. References
8.1. Normative References
[I-D.ietf-bier-lsr-non-mpls-extensions]
Dhanaraj, S., Yan, G., Wijnands, I., Psenak, P., Zhang, Z.
J., and J. Xie, "LSR Extensions for BIER non-MPLS
Encapsulation", Work in Progress, Internet-Draft, draft-
ietf-bier-lsr-non-mpls-extensions-03, 7 February 2024,
<https://datatracker.ietf.org/doc/html/draft-ietf-bier-
lsr-non-mpls-extensions-03>.
[I-D.ietf-bier-ospfv3-extensions]
Psenak, P., Nainar, N. K., and I. Wijnands, "OSPFv3
Extensions for BIER", Work in Progress, Internet-Draft,
draft-ietf-bier-ospfv3-extensions-07, 1 December 2022,
<https://datatracker.ietf.org/doc/html/draft-ietf-bier-
ospfv3-extensions-07>.
[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>.
[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>.
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[RFC8279] 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, November 2017,
<https://www.rfc-editor.org/info/rfc8279>.
[RFC8296] 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, January
2018, <https://www.rfc-editor.org/info/rfc8296>.
[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>.
[RFC8571] Ginsberg, L., Ed., Previdi, S., Wu, Q., Tantsura, J., and
C. Filsfils, "BGP - Link State (BGP-LS) Advertisement of
IGP Traffic Engineering Performance Metric Extensions",
RFC 8571, DOI 10.17487/RFC8571, March 2019,
<https://www.rfc-editor.org/info/rfc8571>.
[RFC9552] Talaulikar, K., Ed., "Distribution of Link-State and
Traffic Engineering Information Using BGP", RFC 9552,
DOI 10.17487/RFC9552, December 2023,
<https://www.rfc-editor.org/info/rfc9552>.
8.2. Informative References
[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,
<https://www.rfc-editor.org/info/rfc4271>.
[RFC4655] Farrel, A., Vasseur, J.-P., and J. Ash, "A Path
Computation Element (PCE)-Based Architecture", RFC 4655,
DOI 10.17487/RFC4655, August 2006,
<https://www.rfc-editor.org/info/rfc4655>.
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[RFC5376] Bitar, N., Zhang, R., and K. Kumaki, "Inter-AS
Requirements for the Path Computation Element
Communication Protocol (PCECP)", RFC 5376,
DOI 10.17487/RFC5376, November 2008,
<https://www.rfc-editor.org/info/rfc5376>.
[RFC5440] Vasseur, JP., Ed. and JL. Le Roux, Ed., "Path Computation
Element (PCE) Communication Protocol (PCEP)", RFC 5440,
DOI 10.17487/RFC5440, March 2009,
<https://www.rfc-editor.org/info/rfc5440>.
Authors' Addresses
Ran Chen
ZTE Corporation
Nanjing
China
Email: chen.ran@zte.com.cn
Zheng Zhang
ZTE Corporation
Nanjing
China
Email: zhang.zheng@zte.com.cn
Vengada Prasad Govindan
Cisco
Email: venggovi@cisco.com
IJsbrand Wijnands
Individual
Email: ice@braindump.be
Zhaohui Zhang
Juniper Networks
Email: zzhang@juniper.net
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