Choppy voice mail over IP trunks

[whitera]

We are having a problem with an IP trunking implementation.

In building 1 we have a Prologix (ver. 10) and an Intuity Audix connected via analog trunks. In building 2 we have another Prologix (ver. 10) that is trunked to building 1 via IP (Prowler board). The physical connection is an underutilized Gigaman circuit. The stations in building 2 are using the Audix in Building 1 for voice mail coverage.

When a station in building 1 calls a station in building 2, and the voice mail in building 1 covers the call, we have an intermittent problem where the recorded message is choppy. The way I would describe the resulting voice message is as though the volume level fluctuates above and below the point where the D/A converter decides to digitize information and send it or not send anything because it doesn't recognize there is voice present.

Any ideas on how to resolve this problem?

 

[BuckWeet]

What codecs are you running for the IP Trunks?


Is the the only Ip traffic going on from PBX to PBX? no Ip phones or anything?


BuckWeet

 

[whitera]

We are using G.729.

There are no other voip applications.

We are just using the ip trunking between locations.

There is data traffic on the connection, but the utilization is such that there should be no network contention.

 

[schned99]

Sounds like packet loss between the PBXs. Check your network region parameters. Also change ethernet options and change the media processor interfaces from auto to 100MB full duplex. In the data switch, hard code the ports that the media processors are plugged into to 100MB full duplex also. Make sure the amphenol to RJ45 connector is the right type (100MB). Make sure all your patch cabling is cat5e. There are a few other things you can try. I'll post if I remember them.

 

[whitera]

We've looked at the network and everything is fine there.

This never occurs during a live call. It only occurs when the call covers to voicemail.

What is happening is a call is set up from building 1 to building 2. The station at building 2 does not answer. The switch at building 2 then rings the voicemail at building 1, keeping two channels open. It is this senario that cuases the choppy voice messages.

 

[lopes1211]

That's 3 A/D conversions. I researched a similar scenario back around R8 and was told of such issues by Avaya due to the A/D conversion when makeing the call IP, + the A/D to send it back to switch 1 via IP, + the A/D conversion recording the vmail digitally. Something may have changed since R8 but I had been warned by our design engineer of that very issue. -CL

 

[whitera]

Interesting. Our design engineer didn't mention any potential issues.

I'll raise that question and let you know what we learn.

 

[shidots]

I had a similiar problem. The Definity had analog lines going back to the C.O. A call came into the Definity and was transferred to their onsite VM system What we proved was the analog line cards were of an old vintage and the cards were actually causing a loss in the voice trail while the VM was being recorded(the VM system was designed to automatically raise the gain while recording if the caller's voice was weak or low in gain which led to overmodulation. While its a digital recording it was as you described, choppy). After extensive research AT&T(at the time) sent out new analog cards and the problem was resolved.

 

[shidots]

Did you get your problem resolved?

 

[whitera]

No. The design engineer is telling us we'll have to set up Diff serv on the network. If that's the problem I'll eat my hat. We have a gigaman link that bursts to about 80 meg. I doubt that is causing the problem.

 

[whitera]

My hat is saved.

In the change trunk group screen, we changed the supplementary service protocol to "DCS-with-rerouting".

This stopped the tromboning and eliminated two A to D conversions.