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limitations of QoS in a congested link

Dear Friends,

I understand that QoS is designed to provide good service to sesitive traffics like Video and Voice in a Congested link.

We also have implemented the same in our network to get better support for our Voip and other applications.

Last week we had a request from one customer to enable QoS for video at their site inorder for a better Video conferece carrying out this week.

We have configured dscp 63 (in class AF41)at the router, note that the utilization of this link high.

Last day we received a feedback that the video conference session breaks for abt 3 to 4  times and each time they requires to reconnect it.

My believe is QoS should perform well in a congested link, thats what it designed for, right ???

Kindly advice is there any limitations in QoS to support in a congested link or any other changes to notify while enabling QOS for application like Video.

Thanks in advance

Riyas RAsheed                  

Super Bronze

Re: limitations of QoS in a congested link


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Video can be very bandwidth demanding in short term time intervals.  I.e. video's short term bandwidth demand can be much, much higher than its nominal or average bandwidth usage.  Real-time video, like video conferencing, also often has tight timing requirements, so when there's a burst, you don't want to delay it.

Ideally you want to treat video conferencing video like LLQ/PQ and have sufficient bandwidth that there's no to very little queuing.

Marking video AF41 can mean much or mean little.  Many additional variables apply.