Initially, most SIP proxies were only transaction-aware—they had only the information regarding requests and replies. However, in many cases, this was a problem for solution developers. If we cannot control a dialog, it is not even possible to know how many simultaneous calls the system is handling. To supersede these limitations, we have the dialog module. This module is extremely important in applications such as prepaid billing, calling cards, and limiting of simultaneous calls per user, gateway, and route. Whenever you need to count, disconnect, and display active calls, you should use this module. In this chapter, we will cover the following topics:
Enabling the dialog module
Creating a dialog
Describing and controlling the dialog matching process
Listing the dialog states
Setting a default timeout for established calls
Discussing dialog variables and flags
Profiling a dialog
Disconnecting calls using the MI interface
Using topology hiding based on the dialog module...