Whats going on behind Asterisk?

hi. i need the real understanding of how asterisk implements different features. i have configured various features and they are working fine. i need the theory of the operation including the protocol layers and all the basic stuff. kindly guide me where can i get this documentation.

The nature of Asterisk’s development over time and by many different parties means that your best source for information is simply the source code itself.

But that is very much complex to understand. Is there any book or tutorial available which guides through this process?

Maybe TFOT:Asterisk book from www.asteriskdocs.org has what you’re looking for.