It has been a great archness from me to illustrate anything, as I’m not able to draw practically anything. Really you would have a hard time to say whether my drawing is supposed to be an apple or a cat. Yet I couldn’t help myself. I simply believe that graphics help to understand complex IMS flows. And unfortunately there are nearly none in telecom standards. Hope this gentle guide will provide you into the world of SIP protocol in VoLTE environment and you’ll gain some new and useful information.
Have a tea/coffee, take it slowly, sip by sip. Enjoy!
If you are new to IMS and VoLTE, please read firstly these posts:
In the first chapter we talk about basic SIP principles and architecture.
In the second post we analyze SIP message and its basic headers.
The third post article is about IMS Registration and we discuss basics of SIP Routing
I’d recommend also to go through other related posts, which are not directly focused on SIP, but which you might find useful:
- Much Ado about Registration
- How to read tcpdump – Registration
- Third Party Registration
- Sh Interface
The fourth post explains basic SIP/VoLTE session signalling.
In the fifth sip we analyze session routing, including Server location discovery.