I recently worked on a SIP B2BUA (back-to-back user agent) on a platform that was routing emergency 911 calls. The originating call used SIP protocol and the emergency service call destination used SS7 protocol, so the original SIP signaling message was translated into SIP-T with the ISUP message added to the body.
As anyone who has ever done protocol work knows, you tend to refer heavily on the RFC’s or ITU specs. Here is a list of the RFC’s that I found especially helpful when working on this SIP B2BUA project:
- RFC 3261, SIP: Session Initiation Protocol, http://www.faqs.org/rfcs/rfc3261.html
- RFC 3262, Reliability of Provisional Responses in the Session Initiation Protocol (SIP), http://www.ietf.org/rfc/rfc3262.txt
- RFC 3372, Session Initiation Protocol for Telephones (SIP-T): Context and Architectures, http://www.ietf.org/rfc/rfc3372.txt
- RFC 3204, MIME media types for ISUP and QSIG Objects, http://www.ietf.org/rfc/rfc3204.txt
- RFC 3325, Private Extensions to the Session Initiation Protocol (SIP) for Asserted Identity within Trusted Networks, http://www.ietf.org/rfc/rfc3325.txt