UC540 Conference Calls Choppy(Cisco Voice)

[Protoform-X]

I recently installed a UC540 for a small shop and configured it with CCA 2.2. Ever since the initial install the users have complained about "poor quality" or "choppy" audio when using ad-hoc conferencing. I've verified that G.711u is being used during the offending calls. I've also verified that the phones are on the correct "10.1.1.0" subnet and data is on a different subnet, so QoS *should* be working? I did alter the data subnet from the original 192.168.10.0 to the existing data subnet, so maybe I broke QoS? I guess it wouldn't make a whole lot of sense since 2-way calls seem to work great.

I decided to change the system over to hardware conferencing to see if that would resolve the issue, but it didn't make a difference. The choppyness is still there. I've tested with all 3 phones being internal to the network and the choppyness is still there. Any great ideas or troubleshooting steps I should take?

I'll gladly post the config if necessary, but it will take some time to scrub it.

 

[Protoform-X]

Bump.

 

[xphil3]

are these ad-hoc conferences of LAN or WAN? You say that its internal, so 100mbps phones?
Did you verify that you QoS policies are matching and queuing if necessary?
Is your WAN overloaded with choppy data which would lead to high jitter?
have you tried to switch the codec to G.729?

I would run two IPSLA endpoints through you LAN to get an average jitter value, which is what would cause your choppy voice. Enabling DSP's wouldn't do much if you LAN is causing excessive latency, but I find it difficult to believe that your LAN is the issue.

 

[Protoform-X]

LAN, WAN- doesn't matter, they both have choppyness. The switchports on the UC540 are all 10/100, so we're limited to 100mbps even though they're using 7970g phones.

Unfortunately I'm a complete scrub to QoS, though I'm trying to learn it. The system is still running the default config for QoS that CCA put on it which has worked great for many other UC5xx systems I've deployed.

The WAN is barely utilized at all. Running a ping test or jitter test to the WAN shows low jitter even from several States away.

I have not attempted a codec change. Is it highly recommended? All the other systems I've deployed are happily running on G.711u without issue.

What's an IPSLA and how do I do it? I agree that the LAN is probably not the issue since 2-way calls do not experience the choppy audio.

 

[xphil3]

Unfortunately I'm a complete scrub to QoS, though I'm trying to learn it. The system is still running the default config for QoS that CCA put on it which has worked great for many other UC5xx systems I've deployed.

Just becuase it worked for one scenario doesn't mean its going to work for them all. Verify that your experiencing congestion and that your QoS is actually queuing and working. Remember, if there is no congestion on the devices ports where you have your policies nothing will queued and given treatment by the scheduler.

The WAN is barely utilized at all. Running a ping test or jitter test to the WAN shows low jitter even from several States away.

What does it looks like? Maximum jitter should never be above 150ms, and optimally never above 100ms.

I have not attempted a codec change. Is it highly recommended? All the other systems I've deployed are happily running on G.711u without issue.

Is it recommended? Depends... Would you rather have 64Kbps per caller or 8Kbps per caller w/o overhead? Your MOS will drop a few 1/10's but its not going to be noticeable imo. I would change the codec and see if you notice a difference.

What's an IPSLA and how do I do it? I agree that the LAN is probably not the issue since 2-way calls do not experience the choppy audio.

http://www.cisco.com/en/US/technolo...technologies_white_paper0900aecd8017f8c9.html , im sure that you can dig up the configuration guide on cco.

Is there anyway that you can setup a meetme bridge as well for testing? I dont like ad-hoc conferences really as the phone is "bridge". I setup a meetme bridge for PeerIX awhile ago over a WAN and had about 6 people on it and there was no choppiness at all. I would try some other options to see if you see the same symptoms.