Anshuman S. Rawat wrote: > Hi All, > > I am facing some ICE issues when I make a call between 2 agents which > use SipXTapi. Scenario is that the 2 agents are behind the same NAT > but register with a public SIP proxy. When I make a call between the > 2, there is one way media. The caller can be heard but the callee is > never heard. From ethereal trace, I can see that the caller completes > the ICE procedures (i.e. sends STUN requests to each candidate in > answer) but the callee doesn't do that. Behaviour is consistent when > the caller and callee UAs are switched. > The problem is the NAT server. In the end the RTP conversation will be between the two devices behind the NAT - however each thinks the other device is a public address (actually the same public address shared by both devices)
The NAT server has to receive RTP packets from a device behind the NAT and then figure out to 'reflect' it back to the other device behind the NAT. In general a NAT will not be able to do this. Hence one way audio of no audio. In this case a topology with a SIP registrar/proxy inside the NAT will solve the problem. Calls that terminate outside the NAT will be redirected correctly by the proxy/registrar. Calls internally will have no problems at all.
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