Qos for H323 Video tele conference traffic

Answered Question

Hi All,

I am using Tandberg video equipment(bridge MPS200, endpoint MPX2000, MPX6000). My WAN routers are Cisco 2800/3800 connecting to MPLS network.

Jitters are between 4ms - 20ms. Picture quality is not very good when I use the bridge calls out to 8 endpoints at 384Kbps.

would you put audio and video traffic into the same class and mark it as EF, or seperate them with marking RTP audio as EF and RTP video = Ip precedence 4?



Correct Answer by Brandon Buffin about 9 years 10 months ago

Yes, keep in mind that the priority command will only take affect during periods of congestion. If the link is not congested, then the excess bandwidth can be used by the default class.


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Overall Rating: 4.5 (2 ratings)
Brandon Buffin Thu, 05/17/2007 - 07:48
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Cisco's recommendation is to mark voice and video with different DSCP values, marking voice as EF and video as AF41 (IP Prec 4). The question of having voice and video share LLQ is up for debate, but in general it's recommended to put only voice in the priority queue. The following link is an excellent document regarding QoS with H.323 video conferencing.


Hope this helps. If so, please rate the post.



Thanks for the link. I have another quick question. If my WAN circuit is 4500K, and I have the below policy-map to reserve 3000K for the priority queue, and the utilization of the priority class at the moment is 2000k, will traffic in my class-default allow to use 1000k available bandwidth in the priority queue?

policy-map OUT


priority 3000 512000

class class-default


Correct Answer
Brandon Buffin Thu, 05/17/2007 - 10:55
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Yes, keep in mind that the priority command will only take affect during periods of congestion. If the link is not congested, then the excess bandwidth can be used by the default class.


israel-reyes Tue, 06/05/2007 - 20:19
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I am working on IPVC for first time, do you have some examples or general temples for gatekeeper, Gateway H.320/H.323 configuration and QoS, for Video, Voice and Data.

allan.wells Wed, 08/29/2007 - 03:32
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Just for the record

The Cisco Enterprise QoS SRND reccomends putting Video AF41 in the PQ.

1st ref 3-12

policy-map WAN-EDGE

class Voice

priority percent 18 ! Voice gets 552 kbps of LLQ

class Interactive Video

priority percent 15 ! 384 kbps IP/VC needs 460 kbps of LLQ

class Call Signaling

bandwidth percent 5 ! BW guarantee for Call-Signaling

class Network Control

bandwidth percent 5 ! Routing and Network Management get min 5% BW

class Critical Data

bandwidth percent 27 ! Critical Data gets min 27% BW

random-detect dscp-based ! Enables DSCP-WRED for Critical-Data class

class Bulk Data

bandwidth percent 4 ! Bulk Data gets min 4% BW guarantee


When provisioning for Interactive Video (IP Videoconferencing) traffic, the following guidelines are


? Interactive Video traffic should be marked to DSCP AF41; excess Interactive-Video traffic can be

marked down by a policer to AF42 or AF43.

? Loss should be no more than 1 %.

? One-way Latency should be no more than 150 ms.

? Jitter should be no more than 30 ms.

? Overprovision Interactive Video queues by 20% to accommodate bursts

Because IP Videoconferencing (IP/VC) includes a G.711 audio codec for voice, it has the same loss,

delay, and delay variation requirements as voice, but the traffic patterns of videoconferencing are

radically different from voice.

tammyc Wed, 06/06/2007 - 06:27
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You state using MPLS for a WAN environment. How many classes of service (CoS) does your carrier use in the MPLS environment? How many classes do you use in you in the MAN and in the LAN environments? Place the interactive audio in EF, as you mention. Place the interactive video (VTC services) into AF41. However, be aware that you will probably be condensing from LAN at 10 classes down to WAN at 4 classes; whereby you will want to make sure the AF41 and EF are both in the same CoS within the MPLS carrier.




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