Bit Indexed Explicit Replication
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Bit Indexed Explicit Replication WG
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The BIER (Bit Index Explicit Replication) Working Group has defined
an architecture [RFC 8279] for multicast forwarding that uses an
encapsulation [RFC 8296] that can be used on MPLS or Ethernet transport.
The BIER-WG is now chartered to produce Standards Track RFCs and to
update or do a Status Change for those RFCs previously published as
Experimental (RFC 8279, RFC 8296, etc.).
First and primarily, the BIER-WG will complete its work on:
1) Transition Mechanisms: The WG will describe how BIER
can be introduced in existing multicast networks to shift multicast
delivery either end-to-end or in part of a network from mechanisms
such as PIM, ng-MVPN, etc. A minimum of the necessary mechanisms
to support incremental deployment and/or managing
different BIER mask-length compatibility may be defined.
Operation of BIER in non-congruent topologies, i.e.
topologies where not all routers are BIER capable can
also be addressed. In addition to tunneling solutions, other
approaches to make BIER deployable in such environments
can be worked on. Each such mechanism must include an
applicability statement to differentiate its necessity from
other proposed mechanisms.
2) Applicability Statements: The WG will describe how BIER can
be applied to multicast L3VPN and to EVPN. This draft will
describe what mechanism is used to communicate the group
membership between the ingress router and the egress routers,
what scalability considerations may arise, and any deployment
considerations. The WG will work on additional applicability
statements, as needed, describing how BIER can be applied.
3) Use Case: The WG may produce one use-case document that clearly
articulates the potential benefits of BIER for different use-cases.
4) Manageability and OAM: The WG will describe how OAM will work in
a BIER domain and what simplifications BIER offers for managing the
multicast traffic. A strong preference will be given to extensions to
5) Management models: The WG may work on YANG models and, as needed,
management APIs to support common manageability.
6) IGP extensions. When a BIER domain falls within a "link state IGP"
network, the information needed to set up the BIER forwarding tables
(e.g., the mapping between a given bit position and a given egress
router) may be carried in the link state advertisements of the IGP.
The link state advertisements may also carry other information related
to forwarding (e.g., the IGP may support multiple topologies, in which
case it may be necessary to advertise which topologies are to be used
for BIER forwarding). Any necessary extensions to the IGP will be
specified by the WG as Standards Track, in cooperation with the LSR WG.
The BIER-WG is additionally chartered to start Standards Track work on:
7) BIER in IPv6 : A mechanism to use BIER natively in IPv6 may be
standardized if coordinated with the 6MAN WG and with understood
8) BIER Traffic Engineering: An architecture for BIER-TE is defined
in draft-ietf-bier-te-arch; associated fundamental technology is included.
9) Extensions to support BIER in multi-area IGP Deployments
The BIER-WG is chartered to investigate the following topics. The adoption
of any Standards Track drafts will require a milestone approved by the
responsible Area Director.
10) Novel uses of the BIER bitmap: There are a variety of proposals for
additional algorithms and other uses of the BIER bitmap and
encapsulation beyond BIER and BIER-TE.
11) BIER between Autonomous Domains: With understood applicability,
these scenarios may be investigated.
12) Use of BIER in Controller-based Architectures: How might controllers
be used to provide calculated BIRTs and/or BIFTs tables to BFRs?
13) Applicability of BIER to Applications: The WG may advise on the
applicability of BIER to various applications.
The BIER-WG will coordinate with several different working groups and
must include the relevant other working groups during working group
last call on the relevant drafts. BIER-WG will coordinate with MPLS-WG
on the associated MPLS-based OAM mechanisms. BIER-WG will coordinate with
LSR-WG on extensions to flood BIER-related information. BIER-WG will
advise BABEL-WG on Babel extensions to support BIER. BIER-WG will
coordinate with BESS-WG and IDR-WG on the applicability of existing
BGP-based mechanisms for providing multicast group membership information.
BIER-WG will coordinate with PIM-WG on the applicability of and extensions
to PIM, IGMP, and MLD to support BIER operations and transition; BIER-WG
will work directly on the applicability statements, as needed.