clearing confusion....

I would appreciate if anyone could provide any hints to clear my confusion over H323 , MGCP , SIP beside RTP, RTCP, cRTP
Other than that how does TDM being replaced over VoIP network...
It seems like the reference is a bit confusing and slightly difficult to digest.....
Other than that how does TDM being replaced over VoIP network...
It seems like the reference is a bit confusing and slightly difficult to digest.....