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Mastering FreeSWITCH

You're reading from   Mastering FreeSWITCH Advanced tips and tricks for advanced multimedia communication

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Product type Paperback
Published in Jul 2016
Publisher Packt
ISBN-13 9781784398880
Length 300 pages
Edition 1st Edition
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Authors (8):
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Darren Schreiber Darren Schreiber
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Darren Schreiber
Russell Treleaven Russell Treleaven
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Russell Treleaven
Kalyani Kulkarni Kalyani Kulkarni
Author Profile Icon Kalyani Kulkarni
Kalyani Kulkarni
Seven Du Seven Du
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Seven Du
Charles Bujold Charles Bujold
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Charles Bujold
Ken Rice Ken Rice
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Ken Rice
Florent Krieg Florent Krieg
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Florent Krieg
Mike Jerris Mike Jerris
Author Profile Icon Mike Jerris
Mike Jerris
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Table of Contents (15) Chapters Close

Preface 1. Typical Voice Uses for FreeSWITCH FREE CHAPTER 2. Deploying FreeSWITCH 3. ITSP and Voice Codecs Optimization 4. VoIP Security 5. Audio File and Streaming Formats, Music on Hold, Recording Calls 6. PSTN and TDM 7. WebRTC and Mod_Verto 8. Audio and Video Conferencing 9. Faxing and T38 10. Advanced IVR with Lua 11. Write Your FreeSWITCH Module in C 12. Tracing and Debugging VoIP 13. Homer, Monitoring and Troubleshooting Your Communication Platform Index

Correlating A-leg and B-leg

As we have seen many times in this book, because FreeSWITCH is a B2BUA (Back to Back User Agent), when a user makes a call via FS, FS actually originates a completely independent new call (to callee), and bridges the two calls' audio streams. The streams then flow from caller to FreeSWITCH to callee (and back). In this context, the first call (from caller to FS) is named "A-leg", while the second (from FS to callee) is named "B-leg".

From the point of view of the user, what she experiences as a call is what for us VoIP geeks is two calls, or a bridged call, or A-leg and B-leg.

It's obviously very useful to be able to visualize and debug a complete bridged call, made by the two legs. This gives us the complete picture of what was experienced by the end user.

We have at least two sides to configure: We need FreeSWITCH to introduce into SIP packets a correlation ID that will tag two calls as two legs of a bridged call, and we need to instruct...

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