| Summary: |
This document gives examples of SIP (Session Initiation Protocol)
call flows for IP telephony. 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). IP telephony 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 ISDN (Integrated Services
Digital Network), ANSI ISUP (ISDN User Part), and FGB (Feature Group
B) circuit associated signaling. PSTN calls are illustrated using
global telephone numbers from the PSTN and private extensions served
on by a PBX (Private Branch Exchange). Example SIP messages used for
testing during SIP 'bakeoff' events include SIP 'torture test'
messages, and messages with invalid parameters, methods, and tags.
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