BGP unsupported capability code

If A tries to peer with B, and B sends a BGP capability 64 to A, if A does not support that capability what would proper and/or reasonable behavior for A be? (a "published" source for it, if you could possibly do so.) a) send unsupported capability code 64 lengh 6 ## 2006-08-17 19:17:05 : [bgp/stack]: send NOTIFICATION msg code (Open-Error) subcode(Open Message Error: Unsupported Capability) to peer w9.x4.y7.z9 via socket 415 b) ignore it c) admin defined rfc3392.txt only appears to address the case where if A tries to peer with B, and B sends a BGP capability 64 to A, if A does not support that capability, B MAY terminate the connection with the above notification. (section 3 paragraph 5) Thanks, Joe