Hi Castillo, I would like to asking you about the Time-stamp header in SIP messages,  and why this header does not supported in most open SIP servers, Is it recommended or not?  Is there any open source support the time stamp header. Is this fact true ?? I think The problem is that both UAS and UAC must have the same system time to generate a useful result. So therefore both or all SIP devices (think about an intermediate proxy) must have NTP activated. Please Help me;