Hello all; I need some Clarification about timestamp header in RFC 3261; i need to use it to estimate the RTT value; how it is work in this scenario?: Invite UA --------------------> Proxy1 | | Invite | | ------------------------------ --------->Proxy2 | 100 trying | | | <---------------------------| | invite | | | | | | --------------------------------------->UA2 | | <-------100 trying------------------- | | | | | <--------180 Ringing-------------- | | | <---------------180 Ringing------- | | | | | | |<---180 Ringing----------| | | UA send invite to proxy1 with timestamp=10 ; then the Proxy1 send the invite message to proxy2 and reply with provisional response (100 trying) and with timestamp=10 0.5; When UA receive 100trying; UA will adapt its retransmition timer T1 to the calculated value from timestamp; then UA adapt T2 Timer value; is This true? Here Can Proxy1 send invite message with timestamp header?; for example timestamp=8 and when proxy2 recive invite request, it send it to UA and he send 100 trying to proxy1 with timestamp=8 0.4; Please Help me; Thanks; Mustafa AL Rifaee