RFC 3392 (rfc3392) - Page 2 of 6

Capabilities Advertisement with BGP-4

RFC 3392         Capabilities Advertisement with BGP-4     November 2002


3. Overview of Operations

   When a BGP speaker [BGP-4] that supports capabilities advertisement
   sends an OPEN message to its BGP peer, the message MAY include an
   Optional Parameter, called Capabilities.  The parameter lists the
   capabilities supported by the speaker.

   A BGP speaker determines the capabilities supported by its peer by
   examining the list of capabilities present in the Capabilities
   Optional Parameter carried by the OPEN message that the speaker
   receives from the peer.

   A BGP speaker that supports a particular capability may use this
   capability with its peer after the speaker determines (as described
   above) that the peer supports this capability.

   A BGP speaker determines that its peer doesn't support capabilities
   advertisement, if in response to an OPEN message that carries the
   Capabilities Optional Parameter, the speaker receives a NOTIFICATION
   message with the Error Subcode set to Unsupported Optional Parameter.
   In this case the speaker SHOULD attempt to re-establish a BGP
   connection with the peer without sending to the peer the Capabilities
   Optional Parameter.

   If a BGP speaker that supports a certain capability determines that
   its peer doesn't support this capability, the speaker MAY send a
   NOTIFICATION message to the peer, and terminate peering (see Section
   "Extensions to Error Handling" for more details).  The Error Subcode
   in the message is set to Unsupported Capability.  The message SHOULD
   contain the capability (capabilities) that causes the speaker to send
   the message.  The decision to send the message and terminate peering
   is local to the speaker.  If terminated, such peering SHOULD NOT be
   re-established automatically.


















Chandra, et. al.            Standards Track