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One Way Voice Traffic

Posted on 2008-06-25
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Last Modified: 2012-05-05
We have been trying to get this IP phone working at a house off site for some time now.  Today, we hooked it up, and if he pages me here at the office, I can hear his voice crystal clear, but if I talk, he can only hear jumble... almost like alien noises...  

We have opened almost all ports on his router with the same results.  I figure since we have made a connection to his phone at the house, and I can hear him crystal clear, the problem may reside on his end?  

How can I test this further?  What ports do I need to have open?  Is there anything I can do to troubleshoot this.  Our IP Phone company is ripping us off on this deal, and we really want this to work.  Please let me know if you have any questions.  I'm on stand by.
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Question by:laustandphound
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by:feptias
ID: 21872497
Those symptoms sound like a problem with connection speed/bandwidth or mis-matched codecs, not with firewall configuration. If the correct firewall ports aren't open then you would get no audio in one direction. Can you select different codecs on the IP phone? G.729 requires less bandwidth than most others.
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by:Reid Palmeira
ID: 21872659
i'd agree with feptias. What kind of connection does he have and is there any way to measure QoS on his connection at home? a general bandwidth test to start, both upload and download. If you're using a G.711 codec you'll need about 80 Kbps bi-directional for the RTP stream. You might also check the RTP ports on your router, not just the TCP ports (which are typically signalling only) but if he's getting some sound it probably isn't an issue with the firewall.

you might also want to make sure he's not doing anything else on the network, (VPN connection for example) which might impede performance on the voice side.
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by:laustandphound
ID: 21874257
What exactly is an RTP Ports on a router  How do I check those settings...
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feptias earned 500 total points
ID: 21874463
SIP normally uses port 5060 to send control messages (requests to start or end the call etc), but it uses other connection ports for the media stream (i.e. the audio). The media is streamed using RTP - Realtime Transport Protocol.
http://en.wikipedia.org/wiki/Real-time_Transport_Protocol

Most IP phones can be configured to use a specific range of port numbers for RTP. If you can find the relevant config menu on the phone then you will be able to see what it is set to use now. You might find the range is preset to 10000-20000, but don't assume those numbers are right. An IP phone doesn't need that many ports for audio streaming - I don't know why so many are set by default.

However, we don't think port forwarding on the router is your problem so all this is probably irrelevant!
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Author Comment

by:laustandphound
ID: 21875733
Ok. changed some settings, and bipassed our networks firewall, and we can get the IP Phone to work outside the network, though with this config, The IP phones inside the network only get one way voice data.  (Meaning no noise at all one way)  

I assume we just need to open UDP ports on the firewall and point to the local IP Phones.

Sound correct?

I am new to this, so if that proposal sounds ridiculous, disregard it. :)
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Expert Comment

by:feptias
ID: 21876044
> I assume we just need to open UDP ports on the firewall and point to the local IP Phones.
Yes, that sounds quite likely if the problem is no audio at all one way, but I got a bit lost with the "what's inside and what's outside your network".
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Author Closing Comment

by:laustandphound
ID: 31470688
Thanks.
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