SIP Telephony Call Flow Examples

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Last updated 1999-10-21
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This document gives examples of SIP IP Telephony call flows. Elements in these call flows include SIP User Agents and Clients, SIP Proxy and Redirect Servers, and Gateways to the PSTN (Public Switch Telephone Network). Scenarios include SIP Registration, SIP to SIP calling, SIP to Gateway, Gateway to SIP, and Gateway to Gateway via SIP. Call flow diagrams and message details are shown. PSTN telephony protocols are illustrated using SS7 (Signaling System 7), ISDN (Integrated Services Digital Network) and FGB (Feature Group B) circuit associated signaling. PSTN calls are illustrated using global telephone numbers from the PSTN and from private extensions served on a PBX (Private Branch Exchange).


Steve Donovan (
Robert Sparks (
Kevin Summers (
Cathy Cunningham (

(Note: The e-mail addresses provided for the authors of this Internet-Draft may no longer be valid.)