QoS config for Video Traffic

dtran · ‎10-29-2008

Hello all,

I have a campus network with several remote sites, at the campus I have a 6509 at the core and 3560 and 3750 switches at the access layer. I do have QoS enable on the 6509 and I am using auto QoS on the 3560 and 3750 switches and all seems to be working fine with my existing VOIP environment. But now as I am in the middle of rolling out a video conferencing solution with the existing QoS config I am experiencing a noticeable delay between audio and video. Example like during a video call I can tell that the voice and the lips of the person speaking are not in synch.

Has anyone run into this issue ? can someone provide me a sample QoS config for the 6509 and 3560/3750 switches ?

P.S. I am using a Tandberg/Codian solution for video conferencing with Tandberg/Codian MCU, IP Gateway, ISDN Gateway and Tandberg endpoints. And both the endpoints and the back-end infrastructure devices and are set for IP Precedence 5.

Thank you very much in advance !!!

Danny

allan.thomas · ‎11-01-2008

The main concern with configuring your back-end infrastructure devices with IP Precedence value 5 is that the 3560/3750 auto-qos will map this value to Q1 which is ordinarily the strict priority Q.

In most cases auto-qos will also configure or map Video to Q3, you can see this as a majority SRR bandwidth is assigned to the Q.

In order to use the strict priority queue, it has to be enabled on the interface 'priority-queue out', without it Q1 will not be emptied before the others. It will be serviced according to the weight.

With auto-qos Q1 will not have enough bandwidth as it will be assigned to Q3. Therefore you could initially enable priority-queue if not already enabled so that Q1 is emptied first, or you increase the weight.

The next question is whether you are using egress scheduling within the Core? and this conforms to your edge classification for Video?

HTH.

Allan