RFC 7307, "LDP Extensions for Multi-Topology", July 2014Source of RFC: mpls (rtg)
Errata ID: 5145
Reported By: Sandra Murphy
Date Reported: 2017-10-05
Section 4.3.2 says:
The format of this sub-TLV is similar to the LDP IPv4 FEC sub-TLV as defined in [RFC4379]. In addition to "IPv4 prefix" and "Prefix Length" fields, this new sub-TLV also specifies the MT-ID (Multi- Topology ID). The Length for this sub-TLV is 5.
It should say:
The format of the MT LDP IPv4 prefix sub-TLV (type 31) is similar to the LDP IPv4 prefix sub-TLV (type 1) as defined in [RFC4379]. In addition to the "IPv4 prefix" and "Prefix Length" fields already defined in the LDP IPv4 prefix sub-TLV, the new MT LDP IPv4 prefix sub-TLV also specifies the MT-ID (Multi-Topology ID) field. While the length of the LDP IPv4 prefix sub-TLV is 5 (and does not include the trailing MBZ bytes), the length of this new MT LDP IPv6 prefix sub-TLV is 8 (and does include the internal MBZ byte).
The original text uses "this sub-TLV" in ways that can be ambiguous. In particular, the final sentence "The Length for this sub-TLV is 5." is incorrect if "this sub-TLV" refers to the topic of the section, i.e., "MT LDP IPv4 FEC Sub-TLV", but is correct if "this sub-TLV" refers to the LDP IPv4 prefix sub-TLV defined in RFC4379/RFC8029. The revised text is suggested to remove the ambiguities. Adrian Farrell provided the bulk of the suggested revisions.
In addition, the sub-TLV names are changed to match the names that were registered in the IANA registry, to aid those trying to find the registry entries.