IPv6 Address Specific BGP Extended Community Attribute
updated by
Extracted elements (11)
A new BGP attribute (rather than a new Extended Community type) was required because the existing BGP Extended Community attribute [RFC4360] defines all Extended Communities as exactly 8 octets, which is insufficient to carry a 16-octet IPv6 address alongside sub-type and local administrator fields.
The sub-types of the IPv6 Address Specific Extended Community are the same as those defined for the IPv4 Address Specific Extended Community (RFC 4360), allowing applications designed for IPv4-based communities to map directly to the IPv6 variant.
The first high-order octet of the type field indicates transitivity: 0x00 means the community is transitive across ASes; 0x40 means it is non-transitive. The second octet indicates the sub-type.
The Global Administrator field is 16 octets and contains an IPv6 unicast address assigned by one of the Internet registries.
The IPv6 Address Specific Extended Community Attribute is a transitive, optional BGP attribute consisting of a set of IPv6 Address Specific extended communities. All routes carrying this attribute belong to the communities listed in it, and it supports multiple sub-types.
The Local Administrator field is 2 octets; the organization holding the IPv6 address in the Global Administrator field may encode any information in this field, with format and meaning defined by the community sub-type.
IANA created a registry entitled 'IPv6 Address Specific Extended Community' for the new BGP attribute (value 25). Future assignments follow First Come First Served policy. Transitive type values are 0x0000–0x00ff; non-transitive are 0x4000–0x40ff.
Two initial type assignments are made in the IPv6 Address Specific Extended Community registry: IPv6 address specific Route Target (0x0002) and IPv6 address specific Route Origin (0x0003).
A potential serious issue exists if a malformed, optional, transitive BGP attribute is received; implementations should follow the error-handling guidance in [OPT_TRANS] (draft-scudder-idr-optional-transitive) to mitigate this risk.
This document introduces no new security issues beyond those already applicable to BGP Extended Communities. Implementers should refer to ongoing BGP security work such as RFC 4593 and SIDR.
Each IPv6 Address Specific extended community is encoded as a 20-octet quantity: 1-octet type (0x00 transitive or 0x40 non-transitive), 1-octet sub-type, 16-octet Global Administrator (IPv6 unicast address), and 2-octet Local Administrator.