ip comunicator suddenly stop receiving rtp, reload pc work again

Unanswered Question
Mar 22nd, 2010

I have agents using ip comunicator. when their recieves calls suddenly stop hearing. the other end can hear it. only one way audio. the workaround is reload pc on worst case changing ip address and then re apply the ip address. and work again.

any ideas? 

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David Hailey Mon, 03/22/2010 - 18:43

I could go down the normal one-way audio troubleshooting but, in this case, your situation sounds like it may be more geared towards an issue with the CIPC client, PC, and/or combination of both.  Honestly, if I were you - I would attempt the following on one machine first:

1) Uninstall the CIPC client.  Reboot the machine.

2) Reinstall CIPC but specify an alternate default installation location.

3) Test calls to the user's machine on their standard subnet.

4) If you still have issues, move the user's PC to another subnet (do not reboot) and test calls from there.

Let's see what happens from there.


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a.gooding Mon, 03/22/2010 - 19:22

Still sounds network related though. If you dont reboot and dont change the ip but do a repair on the network connection, does this fix the issue. If it does, im thinking network. My first thought was firewall but check that first. Im assuming it happens to all agents at one time or the other or are all agents affected at the same time?

Do you have a Physical phone setup as well just to test..

David Hailey Mon, 03/22/2010 - 19:28

May well be network-related but possibly not infrastructure.  I ran into something similar to this a few years back with CIPC installed on the same model laptops at a very large organization.  It turned out there was a firmware issue with the wireless Ethernet cards installed on the laptop.  We had to work with the laptop vendor (after fully vetting the issue) and they released a firmware update that resolved the issue.

Never know, it could be many things but I always like to rule out the simple things first.


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a.gooding Mon, 03/22/2010 - 19:32

Id probably want to agree with you on the network card....i was thinking if

they could setup the hard phone that would at least be able to point in the same direction, that plus if all agents were having it maybe we could attempt to zero in.

lets see what the outcome is.


David Hailey Mon, 03/22/2010 - 19:35

Definitely, you make good points.  We'll see what happens and then I'm sure we can tag this issue right on up.


sdeltoro1 Mon, 03/22/2010 - 19:57

I made test calling even from agent to agent on same subnet and no audio on agent having problem, the phone display the rx 0,

and the problem happends on one pc on time, only one, maybe one day, or two later the same issue on another pc.

without reload the pc work doing only change  ip address. and after that I re apply the original ip add and it still works.

I will try make to repair the network card.

thanks for ideas I will update

sdeltoro1 Thu, 03/25/2010 - 20:52

I have captured on ethereal and I can see what is happening before restart the cumputer.

on the message send by computer that cant hear. not rx packet.

this computer send a message  skinny open receive channelAck that informt what is his ip address and port to receive rtp from the remote computer.

and I can see that port is 0. no no audio is received when th rtp is established end to end computers. the other site can hear.

when reload the pc  the  message is o.k with a port on range 16384 to 32767.

any ideas?

a.gooding Fri, 03/26/2010 - 12:12

i think we are all under the assumption something is blocking it for obvious reasons.

When it went silent, did you do the repair to see if that would work? Now you advised that its one PC but others have the same issue intermittently right? Same type of comp? Same network card?

Id try the repair - to see if a refresh of the setting assists. - If this works without changing the IP then ill say check your network card - Update driver or change card

If the repair doesnt work, change the IP to a known working system and put that known working system with the old IP. i suspect that would not make a difference meaning its defintely something with the computer itself.

If the working comp gives the issue now then we can assume the underlying network might be causing it. Id then check the Switch.

PS. Is your Network  firewall centric designed ? If it is, you can go through the logs on the firewall and see if it seeing it as some sort of attack or something of that nature.

i could be missing something here as well so hoping someone can assist as well.

Aaron Harrison Fri, 03/26/2010 - 12:22


Yeah, I was looking at this earlier but nothing concrete to add... except that if the CIPC is sending out a request to stream media to port 0 it will never work regardless of any NIC or security issues...

I did a quick bug search and turned up some old bugs where the CIPC would send out such a message if a non-default port range had been configured in network settings and it didn't like it - has anything like that been configured to a non-default setting?

There was another one where another program was grabbing high ports... any other softphone or media programs running that might be holding UDP ports?



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