Dispute: shud video or voice get higher priority?

Unanswered Question
Feb 1st, 2007

we'er just starting to do some video conferencing across the wan as well as our first 2 sites doing voip. we are having a disagreement. one guy says video is more sensitive to latency than voice. he asserts we should mark video as a '5' and then voice as a 4. I'm hearing that even if that is so, users will have much less tolerance with voice than with video. so i'm saying mark voice as 5 and video as 4.


I have this problem too.
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mheusinger Fri, 02/02/2007 - 00:08


just a note. The marking alone will not resolve any QoS issue with VoIP or video. It will depend on the policy implemented for those markings. You could even setup a policy, which puts all traffic with "0" in a priority queue and drops all traffic with "5".

So from this point of view I would recommend to stick with the DiffServ compliant and best practice values: VoIP data with IP precedence "5" or DSCP EF and video with a different marking (AF41 is suggested by Cisco).

The advantage will also be, that VoIP devices are usually already marking the traffic with "5" or EF, so no remarking is necessary.

When it comes to policy implementation, make sure VoIP and video conferencing both get priority treatment with enough bandwidth.

Also be aware that video conferencing and video streaming have different QoS requirements. Thus both types of traffic should be in different classes, if occuring simultaneously in a network.

A detailed description with configuration details can be found in "IP Videoconferencing Solution Reference Network Design (SRND)"


"Voice and Video Enabled IPsec VPN (V3PN) SRND"


and in "Enterprise QoS Solution Reference Network Design Guide Version 3.3"


Hope this helps!

Regards, Martin


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