Adding or Changing SIP Headers and Verbs (Windows CE 5.0)
Changing the contents of the SIP datagrams that the IP phone sends and receives is one way to customize the VoIP implementation provided with Windows CE.
For example, you might want to add a custom header to every outgoing SIP datagram. Or you might make a more extensive modification, like adding a new SIP verb that isn't provided or supported by the SIP stack included with RTC.
To do any SIP modification or addition and still use most of the IP phone functionality provided with Windows CE, you can replace the SIP stack used by the VAIL with another SIP stack that you have written or purchased. For information about replacing the SIP stack that the VAIL uses for signaling, see Customizing Non-UI IP Phone Functionality.
In addition, if you use another SIP stack for signaling, you do not need to give up the additional functionality — like presence and instant messaging — provided with the Microsoft SIP stack.
In fact, the TUI uses the VAIL for signaling and the RTC Client API Catalog item directly for presence and instant messaging. Therefore, you can change the VAIL signaling code to use a new SIP stack for signaling without affecting the use of presence and instant messaging functionality provided by the RTC Client API Catalog item.
See Also
Common IP Phone Customization Tasks | How to Develop an IP Phone | Telephony User Interface (TUI) | VoIP Application Interface Layer (VAIL)
Send Feedback on this topic to the authors