An Update on BGP Support for 4-byte ASN Enke Chen enke@redback.com February 2001

Summary of Protocol Extensions <draft-ietf-idr-as4bytes-00.txt> “4-byte AS number capability” defined Encode the AS number as 4 bytes in the AS_PATH and AGGREGATOR attributes when the capability is shared. Two new attributes: NEW_AS_PATH, NEW_AGGREGATOR introduced Both are optional and transitive. Complete AS path info can be re-constructed One 2-byte ASN reserved for transition

Transition A matter of software upgrade No flag day is required Community-based filtering 4-byte ASN can not be encoded directly into a community as specified in RFC 1997. Either encode the private AS number in community, or use extended community

Implementation Protocol Extensions AS-path Based Policy capability advertisement, new attributes construct as path from both attributes AS-path Based Policy 1:100 as part of regular expression (if so used) Community Based Policy support of extended community is optional

Estimated Timeline Finalize protocol in 1Q’2001 Protocol spec in reasonable shape Requested capability code, and attributes codes from IANA Implementation/test in 2Q’2001 extended community is optional estimated coding time: 2 weeks interoperability testing Initial deployment in 2001

Acknowledgements Thanks to Yakov Rekhter for his effort and significant contributions toward the proposed 4-byte AS number solution.