CBWFQ and LLQ in real life: round two

From: Osterberg, Todd \(EM, ITS\) (Todd.Osterberg@ge.com)
Date: Thu Jun 10 2004 - 14:22:05 GMT-3


As a follow-up to Roi's questions in a previous thread...

There is a CCO doc titled "How to Configure Video over IP for Polycom Video Units" that recommends using LLQ for Video with the LLQ priority equal to the H.323 rate plus 25% for IP overhead. Assuming all sites have a frame pvc with a CIR of 1536, H.323 traffic is using 576K (64K voice, 512 video, 25% ip overhead), here is my baseline policy:

policy-map QoSPolicy
  class video-conference
   priority 720
  class important-apps
   bandwidth 256
   random-detect dscp
  class other-traffic
   bandwidth 128

Am I correct in my understanding that the 75% allocation rule will allocat the remaining un-allocation BW proprotionally among all the classes? How much BW would the default class receive?

So what happens if my CIR drops to 1024K and I still need to support the video conferencing @ a decent rate and must provide 256K for important apps. Do I dare change the maximum reserved bandwidth or do I drop the H.323 rate to 512K from 576k? Is the 25% ip overhead from the CCO doc 'double counted' via the 75% rule?

TIA,

Todd Allen Osterberg
GE IT Solutions



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