SIP Service Examples
Steve Donovan, Chris Cunningham, Robert Sparks · 2001
This document gives examples of SIP (Session Initiation Protocol) telephony services. This covers most features offered in so-called Centrex offerings from local exchange carriers and PBX (Private Branch Exchange) features. Most of the services shown in this document are implemented in the SIP User Agents, although some require the assistance of a SIP Proxy. Some require some extensions to SIP including third party call control (3pcc) extensions such as the REFER method. These features are not intented to be an exhaustive set, but rather show implementations of common features likely to be implemented on SIP IP Telephones in a business environment.