Comment #6 on issue 2278 by jean.deruelle: the "branch" parameter in Via header duplicated in different SIP transaction
http://code.google.com/p/mobicents/issues/detail?id=2278
The only thing I see that could do this is that the INVITE 200 OK was so fast that System.nanotime() returned the same value between the initial INVITE creation and the INVITE creation in response to the 200 OK...
