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Steve B

SRTP to RTP one way audio?

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So I have an issue on two new trunk providers (One I am testing and One I inherited). If I have my snom 320 phones connected to the PBX in TLS, I get some intermittent one way audio problems when calling to an outbound number. If I change the phones to TCP or UDP, no one way audio. I know from one of the providers that they don't support SRTP, could this be causing the problem? If the provider does not support SRTP, is there a setting somewhere for this?

 

I am running 4.5.1090 and have a 5.0.5 pbx that has seen similar issues.

 

-Steve

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The SRTP does not flow "through" the PBX. The PBX does always SRTP transcoding. The trunk should be completely isolated from SRTP problem the the phone.

 

Can you isolate the problem with extension-to-extension calls?

 

Also the question is what phone firmware you are using. There were versions years ago that had issues with SRTP. IMHO 8.4.35 should be working well with SRTP. We are also testing 8.7.4.7, although this version is still in beta. The 8.7.3 builds did not work so well for 3xx phones for us.

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We have not had problems on extension to extension calling even with remote extensions involved. We only have problems when using certain outbound providers. I have not run a pcap in this instance but last time I had this problem and had to switch to UDP (ugh) to solve it, I could hear both sides of the conversation on the PBX but only one side at the phone.

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We have not had problems on extension to extension calling even with remote extensions involved. We only have problems when using certain outbound providers. I have not run a pcap in this instance but last time I had this problem and had to switch to UDP (ugh) to solve it, I could hear both sides of the conversation on the PBX but only one side at the phone.

 

That sounds like a coincidence to me. I would try to get a complete PCAP for the trunk traffic and then get a clue if the media is coming to the PBX or not. The PBX is a B2BUA with very little dependence between the sides and should be isolating such problems very well.

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hello

 

I have experienced the same problem; calls from extensions to outside have no inbound audio path. The problem wasn't the firewall, but in the translation from RTP to SRTP by Snom One. As per the OP above, turning off encryption for extensions 'fixes' the problem.

 

I should also say that this problem did not occur for all calls.

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