Distribution of Traffic Engineering Extended Administrative Groups Using the Border Gateway Protocol - Link State (BGP-LS)
Extracted elements (8)
The original administrative groups were defined as a fixed-length 32-bit bitmask. As networks grew and more use cases emerged, the 32-bit length was found to be constraining, motivating the introduction of extended administrative groups (EAGs) in RFC 7308.
The EAG TLV is not a replacement for the existing Administrative Group (color) TLV 1088; as specified in RFC 7308, both values can coexist in a BGP-LS advertisement. The behavior of BGP-LS consumers receiving both TLVs is out of scope for this document.
The Length field of the Extended Administrative Group TLV MUST be a multiple of 4. If the length is not a multiple of 4, the TLV MUST be considered malformed.
The Extended Administrative Group TLV (Type 1173) is a new BGP-LS Link Attribute TLV that encodes extended administrative groups (EAGs) for links. The Value field contains one or more 32-bit bitmasks indicating which administrative groups are enabled on the link.
IANA assigned code point 1173 from the 'BGP-LS Node Descriptor, Link Descriptor, Prefix Descriptor, and Attribute TLVs' registry for the Extended Administrative Group TLV, with a corresponding IS-IS TLV/Sub-TLV reference of 22/14.
It is assumed that IGP instances originating the EAG TLV will support required security mechanisms for OSPF (RFC 7474, RFC 4552, RFC 7166) and IS-IS (RFC 5304) to prevent security issues when propagating the Sub-TLVs into BGP-LS.
The procedures and protocol extensions defined in this document do not affect the BGP security model. Any syntactic error in the new Attribute TLV would result in the BGP-LS Attribute being discarded per RFC 7752. The advertisement of EAG link attribute information presents no significant additional risk beyond existing link attribute information already supported in RFC 7752.
The EAG TLV has a 16-bit Type field (value 1173), a 16-bit Length field (variable, in octets), and a variable-length Value field consisting of one or more 32-bit bitmasks. The Length MUST be a multiple of 4 octets.