ats version is v100r003c01. during test we find some ims to ims call the caller and called side can not hear each other. the call can be answered normally, but there is no voice.
but the ptime value of caller side is 20 while called side is 30, that is why the both side can not hear each other.
we can execute 'mod sipcfg: sfpara=support_multi_ptime-1;' on ats to make ats support multiple ptimes to solve this problem. after setting, the problem is solved.
1. the media ip can not ping.
2. the ptime in sdp is inconsistent.
because this is an inner ims call, both caller and called terminals are in the same network, so the first condition does not hold. so we need to check the ptime parameter.