RFC 3392 (rfc3392) - Page 2 of 6
Capabilities Advertisement with BGP-4
Alternative Format: Original Text Document
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