[Serusers] Mediaproxy Call hold/unhold

Dear All, I encountered a problem like this. Case 1: ------- If UA1 calls UA2 using the following: Normal call: UA1 ------invite -------port 30000 -----> UA2 UA1 <--------OK---port 26000--------------UA2 The connection and media is established. Hold the call: UA1------invite ---port 30000 (hold)--> UA2 UA1 <----------OK port 26000----------UA2 The media is in hold state. Unhold the call: UA1------invite ----port 30000--------->UA2 UA1 <---------OK port 260000----------UA2 Media resume. The above mentioned work fine with mediaproxy. Case 2: ------- If UA1 calls UA2 using the following: Normal call: UA1 ------invite -------port 30000 -----> UA2 UA1 <--------OK---port 26000--------------UA2 The connection and media is established. Hold the call: UA1------invite ---port 30000 (hold)--> UA2 UA1 <----------OK port 26000----------UA2 The media is in hold state. Unhold the call: UA1------invite ----port 30001--------->UA2 UA1 <---------OK port 260000----------UA2 *****Noticed that the reinvite has a different port! In this situation, media does not resume and mediaproxy has a "stray hold" session. I tested case2 without flowing through the mediaproxy and found that the call can be hold/unhold successfully. I am not familiar with RFC at all, please help! (1) I would like to know whether it is valid to reinvite with a different port as in case 2, i.e., is the UA1 ill-behave in case 2 when unhold the call with different port? (2) Is the mediaproxy designed to work using the some port when hold/unhold. Thanks you very much for any help available. Regards, TC Chan