Chapter 17. Call Control
Since the inception of the core SIP, numerous SIP extensions have been defined that provide new tools and capabilities to manipulate SIP calls and dialogs. The combination of these tools allows us to build many SIP-based services. In this chapter, we will look at some of these extensions. We start by explaining what we mean by “call control” in the remit of SIP, and then we will see different approaches to implement call control and the tools that are available.
What Is Call Control?
In the remit of SIP, we will use the term call control to refer to the manipulation of SIP session dialogs or SIP conference media policy in order to cause participants in a conversation to perceive specific media relationships. All the participants ...