…fc7826 2 42 pages 1998-04 Proposed Standard RFC Obsoleted by rfc4566 Updated by rfc3266 2 151 pages RFC 2543 SIP: Session Initiation Protocol 1999-03 Proposed Standard RFC Obsoleted by rfc3261 , rfc3262 , rfc3263 , rfc3264 , rfc3265 2 18 pages 2000-10 Experimental RFC 110 pages R…