| Internet-Draft | ISIS for BIER-TE | July 2023 |
| Chen, et al. | Expires 6 January 2024 | [Page] |
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.¶
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.¶
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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.¶
[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).¶
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.¶
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 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| BAR | IPA | sub-domain-id |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| BitPosition | DisEndBitPosition |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
~ Sub-Sub-TLVs (variable) ~
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
No Sub-Sub-TLVs are currently defined.¶
A TLV, called Node BPs TLV, is defined. 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. The Node BPs 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-TLVs ~
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
The Routed-BP 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 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
The Localdecap-BP 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 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Protocol extensions defined in this document do not affect the IS-IS security.¶
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| +-------+-------------+--+--+--+---+---+---+-------------+¶
IANA is requested to make a new allocation in the "IS-IS TLV Codepoint Registry" under the registry name "IS-IS TLV Codepoints" as follows:¶
+==============+===================+=====================+ | TLV Type | TLV Name | reference | +==============+===================+=====================+ | TBD2 | Node BPs ID | This document | +--------------+-------------------+---------------------+ Note that TBD2 is less than 255.¶
IANA is requested to create a new sub-registry "Sub-TLVs for TLV type TBD2 (Node BPs TLV)" under the IANA IS-IS TLV Codepoints as follows:¶
+==============+===================+=====================+ | Type | Name | reference | +==============+===================+=====================+ | 0 | Reserved | +--------------+-------------------+---------------------+ | 1 | Routed BP | This document | +--------------+-------------------+---------------------+ | 2 | Localdecap BP | This document | +--------------+-------------------+---------------------+ | 3 - 255 | Unassigned | +--------------+-------------------+---------------------+¶
The authors would like to thank Acee Lindem, Les Ginsberg, Tony Przygienda, Jeffrey Zhang and Toerless Eckert for their comments on this work.¶