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Global Call IP Technology Guide — November 2007 337
Dialogic Corporation
5
5.Third Party Call Control (3PCC)
Operations and Multimedia
Support
This chapter provides an overview of the libraries and protocols used for third party call control
(3PCC) and describes how to use the Dialogic
®
Global Call API to perform certain third party call
control operations in a SIP environment. Topics include:
• Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 337
• Global Call in Third Party Call Control Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 343
• Session Description Protocol Parser/Generator Example . . . . . . . . . . . . . . . . . . . . . . . 353
• Message Sequence Diagrams . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 353
• Processing Intraframe Requests for Video Streams. . . . . . . . . . . . . . . . . . . . . . . . . . . . 371
5.1 Overview
This section provides an overview of third party call control, along with brief descriptions of the
libraries and protocols required to support third party call control. The following topics are
presented in this section:
• Third Party Call Control
• Global Call Library and IP Media Library for Third Party Call Control
• Session Description Protocol
5.1.1 Third Party Call Control
Third party call control enables one entity (for example, a third party call controller) to create,
modify, or terminate a media session between two or more endpoints. Call control signaling and
media exchange are separated and independently managed.
The key attributes of third party call control are:
• A distinct third party call controller initiates the session.
• The third party call controller initiates communications via a SIP signaling interface to each of
the endpoints involved in the session.
• The endpoints do not need to directly establish signaling interfaces between one another;
instead, they have a signaling relationship with the third party call controller.
• The third party call controller does not serve as an endpoint for the media stream; the media
stream flows between the two endpoints.