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New Member

Confrence Call Voice Quality

Hello folks,

We have a serious voice quality issue with the Conference calls. The IPT Network includes 68 sites nation wide with a centralized topology. There's absolutely no quality issue between two IP Phones but as soon as we conference few people, the quality gets affected greatly. The CallManager is 4.0 and the most of the Gateways are 2620 with few 2650 and 2610. Please note that the voice quality for the initiator of Conference call is not as bad as the other participants. The average jitter gets up to 450 and that's when everybody breaks up. The RxLost is 0000 even during the bad quality. We have 10 CFB, 7 MRG and 13 MRGL configured in the CallManager. Could you please let me know how can I resolve this issue?

Thanks,

Bahman

7 REPLIES
New Member

Re: Confrence Call Voice Quality

Your jitter is way out of line. What type of conferencing are you using? MeetMe, Ad-Hoc or other?

We found that any conference that needed transcoding resources could be expected to be poor. Whether it

is a problem with transcoding, or the fact that we

baesd our QoS on diff-serv and IOS based transcoding and conferencing is stuck with ToS, we could not say.

I suspect you need to tune QoS on your LAN/WAN.

New Member

Re: Confrence Call Voice Quality

Thanks,

I am uploading a router configuration which is the same for all routers. Could you please have a quick look at it and let me know if there's anything wrong with it.

Thanks,

BT

New Member

Re: Confrence Call Voice Quality

first comment, I would remove the attachment and re-add it without the passwords in it, and maybe even mask the ip addresses out. Security and all that.

Second, you have a pretty complete QoS architecture.

Since you labeled the serial interface as being an AT&T IPFR, I can comment that diffserv based Qos is honored on that network, but you do have to request it from AT&T. There is a posibility that AT&T is delaying your carefully tagged traffic.

Lastly, we have found that allowing bursting on frame circuits is a sure fire way to have poor quality. We spec the port and PVC to match eaxactly or as close to exactly as the carrier will allow.

Since you are not apparently using IOS conference resources, my comment about SCCP/TOS may not apply.

What are you using for conferencing, Call Manager resources, VG200 or catalyst DSP blades? Are your remote sites using G729? Is so, where are your transcoders?

New Member

Re: Confrence Call Voice Quality

Thanks for the advice. I removed the attached file. I will definitely verify with the telco.

I think we are using CallManager resources. I can see 48 availabe resources in Window Performance Monitor. How can I identify if we are using CallManager resources or DSP blades. We are using VG200 only for our Fax Machines

The remote sites are using G729 and we don't have any transcoder.

As everybody is G729, do we need a transcoder?

Thanks,

BT

New Member

Re: Confrence Call Voice Quality

Look Media Resources/Conference Bridges. If all you

see is the names of Call Manager servers, then you are not using hardware conferencing.

Cisco conferencing resources on the Call Managers cannot mix G729 audio, so you must have something

doing transcoding. I asked about the VG200 as we found them to be a terrible platform for transcoding, and had nothing but trouble with them.

I ended up moving the voice modules to a 3700 series router that was getting more regular IOS updates and the issue improved.

New Member

Re: Confrence Call Voice Quality

We do use hardware Confrerencing. CFB000F239F02A0 is one of the 10 CFB's that we are using. What could go wrong with CFB's? How can I troubleshoot a haredwate Conferencing?

Thanks,

BT

New Member

Re: Confrence Call Voice Quality

OK, what hardware provides that resource? I did not see a configuration in the sample router config you posted.

If it is on an IOS router, the issue may be QoS. The SCCP stack on the router that provides the CFB/MTP/Transcoder does not support DiffServ, so depending on your QoS strategy, those packets will not be matched/tagged. You can use a class map to match TOS 5 and retag it to diffserv EF, but that means that existing properly tagged packets will also be retagged.

I'de suggest a test plan to check three local phones using an Adhoc conference and a meetme, as the phone should be able to mix a three party call without a CFB resource. By keeping the phones local, you also avoid transcoding.

If that test produces good results, I would look closer at the CFB hardware settings (IOS or CatOS) and consider the QoS issues mentioned above.

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