Failed VCM?

[crumthwacket]

How do you determine that a VCM has failed?

We have 2 IPOs connected via a dedicated PtoP through Netopia routers. There is no traffic on the link other than voice calls from IPO to IPO. It has worked well for 2 years, but in the last week the voice quality has gone down the drain. The service provider dispatched techs to either end and the circuit has tested clean. After a system reboot, the connection is restored, but not with the same quality as before. No changes have been made to the translations. Before taking the expensive route and replacing the voice compression modules, I was hoping for some direction from you folks. When a VCM fails, is it completely out of service or does it fail gradually? Technical support suggests replacing the IPO and the VCM on both sides. I was expecting a more scientific approach than this. Any ideas? As you may guess, the customer is not very pleased with the estimate to replace an out of warranty VCM.

 

[IPAlot]

from what I've seen over the last few years, if its gone its gone.

Soopa Doopa Intergalactic IP Office installation mechanic and configuration corruptor from way back.

 

[intrigrant]

All the broken VCM's i have seen did result in a reboot of the IP Office at random times and immediatly after trying to setup a VoIP call.

 

[crumthwacket]

Thanks for the input, guys.

It seems logical, then, that the VCMs have not failed and the voice quality problems are the result of something else. Do you agree?

 

[intrigrant]

Yes, now you need to know what to do next i guess.
Open SysMonitor and trace both ends with all of H.323, perhaps that could shine a light on it. It could also be very well a poor cable or something stupid as that, check and replace if any doubt exists.
You could also sniffer the network with software like Observer in order to measure delays, jitter etc.Connect the PC with the sniffer as close to the IPO as possible, preferably on the hub of the IP Office.
If no faults are found then try to replace hardware and see if that solves it.

 

[crashtest1000]

From experience when VoIP has poor quality it is 9 times out of 10 a network issue Hub switch router. Check your IPO codec is set to G711 or G729 and not Auto.

Are you sure there is no data going over the network to prove this drop the LAN off at each end and make some phone calls to see how the VoIP sounds.

What is the ping time? with a standard packet.

On the IPOffice side there was a version around 1.4 where VoIP quality would drop off over time however this was when you used the IPO as a router fixed in 2.1.

 

[crumthwacket]

The problem turned out to be a failed VCM 20 module. I performed the H323 trace but interestingly enough it showed the call was connected and worked well. After some frustration, I pulled the VCM out and replaced it and voila, it worked.

Thanks for all your input.

 

[intrigrant]

For everything there must be a first time, i have never seen a broken VCM working a little bit.

 

[crumthwacket]

I don't know what to say, Intrigrant. The voice quality degraded over a week - until there was no audio at all (there was ringing, lamps, etc.). Replacing the VCM brought it back into service - no other changes were made.