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Extended Optional Parameters for the BGP OPEN Message (draft-chen-bgp-ext-opt-param.txt )

Extended Optional Parameters for the BGP OPEN Message (draft-chen-bgp-ext-opt-param.txt ). Enke Chen & John Scudder {enkechen, jgs}@cisco.com. Problem Description. BGP capabilities are carried in the Optional Parameters field which is limited to 255 bytes The limitation is becoming a concern

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Extended Optional Parameters for the BGP OPEN Message (draft-chen-bgp-ext-opt-param.txt )

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  1. Extended Optional Parameters for the BGP OPEN Message(draft-chen-bgp-ext-opt-param.txt ) Enke Chen & John Scudder {enkechen, jgs}@cisco.com

  2. Problem Description • BGP capabilities are carried in the Optional Parameters field which is limited to 255 bytes • The limitation is becoming a concern • New features continue to be introduced using capabilities • New address families continue to be added • Address family specific capabilities have a multiplier for the bytes required.

  3. Problem Description (cont) • Existing capabilities: 7 + pending + vendor specific ones • Exiting address families (afi, safi): 6+ • Address family specific capabilities: • Multi-protocol: 2 + 4 x N • Graceful Restart: 4 + 4 x N • ORF: 2 + 7 x N • … • Fixed length capabilities: • Route refresh: 2 + 4 • 4byte AS: 2 + 4 • …

  4. Proposed Solution • Introduce Extended Optional Parameters • Param. Length: 2 bytes • Identical semantics as the Opt. Param. • Existing optional parameters also valid for the extended optional parameters • The field can be optionally appended to the existing OPEN message • Its presence is determined by the Extended Optional Parameters Capability

  5. Proposed Solution (cont) • Extended Optional Parameters Capability • Capability length: 1 byte • Capability value indicates whether the Ext. Opt. Param. field is included, and whether a second OPEN is intended • The capability itself also indicates its support of the Ext. Opt. Param. Field

  6. Operation • Advertise the capability (with the proper value) • Include the Ext. Opt. Param field only if the remote speaker can handle it • After receiving the capability or • Via configuration • Use “double open” without knowing the remote speaker’s capability • Indicate the intention of 2nd OPEN in the 1st OPEN • Send the 2nd OPEN once the capability is received

  7. Operation (cont) • For the speaker on the receiving side of the “double open” procedure • Use the 1st OPEN for connection collision resolution • Use the 2nd OPEN for session properties • Advantages of “double open” • Predictable message format and behavior • Faster than tearing down the session, and retrying

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