Please explain what is the difference between Via, From and Contact header in SIP INVITE and they these headers contain redundant information? Please don't give reference to RFC3261 because I have already read that but it didn't help!! From Header  ...

Why do we hear ringing/IVR when we hear RTP in wireshark from SIP traces when RTP is supposed to be established after 200 OK followed by ACK and all these things happen before ACK? I think the only thing which should be in RTP is the conversation whi...

Why do we make different dial-peers for different type of calls like Long distance calls, local calls, international calls, 911 calls(emergency calls). Why can't we match the dialed digits as "destination-pattern 0T" instead of making and managing so...