Which UA are you using??? It looks like all your issues comes from the implementation you are using as end-point and has nothing to do with SER. Samuel. Unclassified. Hi all I would like to explain some problem. When my UAC initiates INVITE the server response with 100 trying After receiving 100 trying the UAC sending again INVITE. ( HERE is the problem). RFC - 3261 ("After receiving a 1xx response, any retransmissions cease altogether "); Any help on that will be appreciated. In addition if there any way to extend the timeout between the INVITES. Thanks