--------->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