rfc9272v2.txt   rfc9272.txt 
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Request for Comments: 9272 A. Przygienda Request for Comments: 9272 A. Przygienda
Updates: 8401, 8444 Juniper Networks Updates: 8401, 8444 Juniper Networks
Category: Standards Track A. Dolganow Category: Standards Track A. Dolganow
ISSN: 2070-1721 Individual ISSN: 2070-1721 Individual
H. Bidgoli H. Bidgoli
Nokia Nokia
IJ. Wijnands IJ. Wijnands
Individual Individual
A. Gulko A. Gulko
Edward Jones Wealth Management Edward Jones Wealth Management
August 2022 September 2022
Underlay Path Calculation Algorithm and Constraints for Bit Index Underlay Path Calculation Algorithm and Constraints for Bit Index
Explicit Replication (BIER) Explicit Replication (BIER)
Abstract Abstract
This document specifies general rules for the interaction between the This document specifies general rules for the interaction between the
BIER Algorithm (BAR) and the IGP Algorithm (IPA) used for underlay BIER Algorithm (BAR) and the IGP Algorithm (IPA) used for underlay
path calculation within the Bit Index Explicit Replication (BIER) path calculation within the Bit Index Explicit Replication (BIER)
architecture. The semantics defined in this document update RFC 8401 architecture. The semantics defined in this document update RFC 8401
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"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
"OPTIONAL" in this document are to be interpreted as described in "OPTIONAL" in this document are to be interpreted as described in
BCP 14 [RFC2119] [RFC8174] when, and only when, they appear in all BCP 14 [RFC2119] [RFC8174] when, and only when, they appear in all
capitals, as shown here. capitals, as shown here.
2. Updated Definitions for IPA and BAR Fields 2. Updated Definitions for IPA and BAR Fields
The definitions for the IPA and BAR fields in Section 6.1 of The definitions for the IPA and BAR fields in Section 6.1 of
[RFC8401] and Section 2.1 of [RFC8444] are updated as follows. [RFC8401] and Section 2.1 of [RFC8444] are updated as follows.
IPA: IGP Algorithm. Specifies a generic Routing Algorithm (RA) and IPA: IGP Algorithm. Specifies a generic Routing Algorithm and
related Routing Constraints (RC) to calculate underlay paths to related Routing Constraints to calculate underlay paths to reach
reach other Bit-Forwarding Routers (BFRs). Values are from the other Bit-Forwarding Routers (BFRs). Values are from the "IGP
"IGP Algorithm Types" registry. One octet. Algorithm Types" registry. One octet.
BAR: BIER Algorithm. Specifies a BIER-specific Algorithm (BA) and BAR: BIER Algorithm. Specifies a BIER-specific Algorithm and BIER-
BIER-specific Constraints (BC) used to either modify, enhance, or specific Constraints used to either modify, enhance, or replace
replace the calculation of underlay paths to reach other BFRs as the calculation of underlay paths to reach other BFRs as defined
defined by the IPA value. Values are allocated from the "BIER by the IPA value. Values are allocated from the "BIER Algorithm"
Algorithm" registry. One octet. registry. One octet.
When a BAR value is defined, the corresponding BA and BC semantics When a BAR value is defined, the corresponding BIER-specific
SHOULD be specified. For an IGP Algorithm to be used as a BIER Algorithm (BA) and BIER-specific Constraint (BC) semantics SHOULD
IPA, its RA and RC semantics SHOULD be specified. If any of these be specified. For an IGP Algorithm to be used as a BIER IPA, its
semantics is not specified, it MUST be interpreted as the "NULL" Routing Algorithm (RA) and Routing Constraint (RC) semantics
algorithm or constraint. For example, the IGP Algorithm 0 defined SHOULD be specified. If any of these semantics is not specified,
in [RFC8665] is treated as having a NULL RC, i.e., no constraints it MUST be interpreted as the "NULL" algorithm or constraint. For
(see Section 3). example, the IGP Algorithm 0 defined in [RFC8665] is treated as
having a NULL RC, i.e., no constraints (see Section 3).
If a specification is not available for a specific BAR value, its If a specification is not available for a specific BAR value, its
value MUST be from the Private or Experimental Use range of the value MUST be from the Private or Experimental Use range of the
registry. registry.
3. General Rules for the BAR and IPA Interaction 3. General Rules for the BAR and IPA Interaction
For a particular sub-domain, all BFRs MUST be provisioned with and For a particular sub-domain, all BFRs MUST be provisioned with and
signal the same BAR and IPA values. If a BFR discovers another BFR signal the same BAR and IPA values. If a BFR discovers another BFR
advertising a different BAR or IPA value for a sub-domain, it MUST advertising a different BAR or IPA value for a sub-domain, it MUST
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