T1
SIP
Messages, dialogs, and media
Sources and go deeper
Opened 2026-10. A row marked confirm has no link, because that page was not verified.
- RFC. RFC 3261, SIP last checked 2026-10
- RFC. RFC 3550, RTP last checked 2026-10
- RFC. RFC 4566, SDP last checked 2026-10
- Cisco. Cisco Unified Communications Manager product support last checked 2026-10
- Cisco. System Configuration Guide for CUCM, Release 15 last checked 2026-10
- Protocol and ports. CUCM 15 TCP and UDP port usage last checked 2026-10
- Protocol and ports. IANA SIP parameters last checked 2026-10
- Protocol and ports. IANA RTP parameters last checked 2026-10
- Community. Cisco Community, Collaboration knowledge base last checked 2026-10
- Wikipedia. Session Initiation Protocol (Wikipedia) last checked 2026-10
- Wikipedia. Real-time Transport Protocol (Wikipedia) last checked 2026-10
- Cisco. Collaboration 12 SRND book. confirm. The historical Collaboration 12 SRND path opened as a product listing, not the design book. Use the Preferred Architecture index, which was opened. last checked 2026-10
- RFC. RFC 3264, offer/answer last checked 2026-10
- Wikipedia. Session Description Protocol (Wikipedia) last checked 2026-10
- Wikipedia. Skinny Client Control Protocol (Wikipedia) last checked 2026-10
- Wikipedia. CUCM (Wikipedia disambiguation) last checked 2026-10
- Wikipedia. English Wikipedia article for Cisco Unified Communications Manager. confirm. That title returned HTTP 404. The CUCM disambiguation page is the Wikipedia page that opened. last checked 2026-10
- RFC. RFC 3262, reliable provisional responses (PRACK) last checked 2026-10
SIP transactions and dialogs
A transaction pairs a request with its responses.
Offer and answer
SDP is the offer or the answer, not a second signaling protocol you ignore.
Registration
REGISTER publishes a Contact. It does not place a call.
Early media and PRACK
183 Session Progress can carry SDP before answer.
Sources and go deeper
Opened 2026-10. A row marked confirm has no link, because that page was not verified.
- RFC. RFC 3261, SIP last checked 2026-10
- RFC. RFC 3550, RTP last checked 2026-10
- RFC. RFC 4566, SDP last checked 2026-10
- Cisco. Cisco Unified Communications Manager product support last checked 2026-10
- Cisco. System Configuration Guide for CUCM, Release 15 last checked 2026-10
- Protocol and ports. CUCM 15 TCP and UDP port usage last checked 2026-10
- Protocol and ports. IANA SIP parameters last checked 2026-10
- Protocol and ports. IANA RTP parameters last checked 2026-10
- Community. Cisco Community, Collaboration knowledge base last checked 2026-10
- Wikipedia. Session Initiation Protocol (Wikipedia) last checked 2026-10
- Wikipedia. Real-time Transport Protocol (Wikipedia) last checked 2026-10
- Cisco. Collaboration 12 SRND book. confirm. The historical Collaboration 12 SRND path opened as a product listing, not the design book. Use the Preferred Architecture index, which was opened. last checked 2026-10
- RFC. RFC 3264, offer/answer last checked 2026-10
- Wikipedia. Session Description Protocol (Wikipedia) last checked 2026-10
- Wikipedia. Skinny Client Control Protocol (Wikipedia) last checked 2026-10
- Wikipedia. CUCM (Wikipedia disambiguation) last checked 2026-10
- Wikipedia. English Wikipedia article for Cisco Unified Communications Manager. confirm. That title returned HTTP 404. The CUCM disambiguation page is the Wikipedia page that opened. last checked 2026-10
- RFC. RFC 3262, reliable provisional responses (PRACK) last checked 2026-10