[Users] Random error with NAT (error in 'c field')

[Bruno Machado]

Hi fellows
 
     Our system is showing an anormal behavior. Sometimes, our clients devices behind NAT cannot obtain successfuls call to other device. Take a look at the SDP headers below. These 2 dumps were made between SIP Proxy and client (at private IP 192.168.0.13). Notice that the 'c field' is differente between them. The first SDP has the public address from RTPProxy (X.Y.Z.A). This call is a example of a perfect situation. The SDP below that shows the 'c field' with a private address. When the call is established, the RTP from my phone is sent to this private IP, 192.168.0.13, in our LAN. 
 
     All the sinalization is sent among the 2 devices and SIP Proxy normally.
 
     When the 'openser' process is restarted, the calls flows without any problems. 
 
     Somebody knows what can be happen?
 
 
     Thanks in advance
 
     Bruno Machado
 
 
 ..................
 INVITE,ACK,CANCEL,BYE,NOTIFY,REFER,OPTIONS,INFO,SUBSCRIBE,UPDATE
 Content-Type: application/sdp
 Content-Length: 402
 P-hint: usrloc applied
 P-hint: nat-p2p
 v=0
 o=11000600 8000 8002 IN IP4 192.168.0.13
 s=SIP Call
 c=IN IP4 X.Y.Z.A..t=0 0
 m=audio 56304 RTP/AVP 18 4 0 8 2 99 101
 a=sendrecv
 a=rtpmap:18 G729/8000
 a=rtpmap:4 G723/8000
 a=rtpmap:0 PCMU/8000
 ...................
 
 
 INVITE,ACK,CANCEL,BYE,NOTIFY,REFER,OPTIONS,INFO,SUBSCRIBE,UPDATE
 Content-Type: application/sdp
 Content-Length: 381
 P-hint: usrloc applied
 P-hint: nat-p2p
 v=0
 o=11000600 8000 8002 IN IP4 192.168.0.13
 s=SIPCall
 c=IN IP4 192.168.0.13
 t=0 0
 m=audio 5004 RTP/AVP 18 4 0 8 2 99 101
 a=sendrecv
 a=rtpmap:18 G729/8000
 a=rtpmap:4 G723/8000
 a=rtpmap:0 PCMU/8000..a=rtpmap:8
 .......................
 
 
 
 
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