QOS Configuration Question

Unanswered Question

I am working on some quality issues with video traffic in the following policy.


policy-map Queue-Wan-Edge-Out

class Queue-RT-OCS-Audio

priority 128

class Queue-RT-OCS-Video

bandwidth 840

class class-default

shape peak 568000 71000 100000

service-policy output Queue-Other-Apps


I am reserving 128k for voice in the priority queue and using CBWFQ for 840kbps of video traffic. The remaining 568kbps is being shaped with a peak shaper that allows it to burst to the 90 percent of the interface speed. However, when we congest the link with a multiple FTP transfers the video traffic finally dies. Any ideas why?


The peak shaper should not over run BW that has been reserved using the bandwidth command if that bandwidth is being used should it?



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Giuseppe Larosa Tue, 10/14/2008 - 11:43
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Hello Michael,

I would rewrite the policy-map without using any shaping commands only queueing, you could even use fair-queue on the class-default.

I would provide bandwidth commands for all the traffic classes that are now under Queue-Other-Apps with a single level of policy.


Another variant could be that of using two LLQ queues one for voice and the other for video and bandwidth commands for the other classes.


Usually when using multiple levels of policy maps all traffic classes are treated at the same level with external policy shaping all traffic.


Hope to help

Giuseppe


allan.thomas Tue, 10/14/2008 - 12:55
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The issue could be attributed to the fact that you have possibly oversubscribed the bandwidth using nested policies.


Within the service-policy for Class class-default what bandwidth has been allocated for the other traffic? Essentially any CBFWQ classes assigned to this service-policy will have their bandwidth guaranteed regardless of what you have provision for Voice and Video.


If possible please post your configuration.


Rgds

Allan.





Joseph W. Doherty Tue, 10/14/2008 - 17:02
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"The peak shaper should not over run BW that has been reserved using the bandwidth command if that bandwidth is being used should it?"


But you don't show a bandwidth command in the class-default, just the shaper. If you added a "bandwidth 568", that might help. What does service-policy Queue-Other-Apps look like?


Two questions on the shaper: 1) why use it at all (and not the bandwidth command), 2) why peak especially with such large burst sizes?


Is your voice real-time or streaming? Does class Queue-RT-OCS-Video show drops?


What type of interface is this being applied to? (I assume some type of T1 from your bandwidth and shape values, but what kind?)

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