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[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
This section defines a Sub-TLV for distributing a link
[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:¶
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:¶
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
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
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
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.¶
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|
Psenak, P., Gredler, H., Shakir, R., Henderickx, W., Tantsura, J., and A. Lindem, "OSPFv2 Prefix/Link Attribute Advertisement", RFC 7684, DOI 10.17487/RFC7684, , <https://www.rfc-editor.org/info/rfc7684>.
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, , <https://www.rfc-editor.org/info/rfc7770>.
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>.
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, , <https://www.rfc-editor.org/info/rfc8444>.