buffers and queues

Hi all,

I'm trying to get my head around how buffers and queues function. Am I correct in saying that the buffers shown by the "show buffers" command are used only by the hardware queues (tx and rx rings)?

If this is correct then can I assume that buffers for mqc based queues are held elsewhere in memory and we only really use the "show policy-map interface" command to work out what's going on?

Next I'm trying to work out the difference between the "hold-queue" command on an interface vs in a service policy. If I configure the following:

policy-map SCHEDULE
 class FTP
  bandwidth 200
  hold-queue 100
 class HTTP
  bandwidth 200
  hold-queue 100
policy-map TEST
 class class-default
  shape ave 512000
  hold-queue 200
  service-policy SCHEDULE

interface f0/0
 hold-queue 200
 service-policy output TEST

Am I correct in saying that the hold-queue 200 on the interface allocates enough memory to hold 200 packets for all layer 3 queues meaning that the hold-queue command under the class-default class of TEST should never be higher than 200?

In addition if I want to ensure that classes under the SCHEDULE map are guaranteed to get a buffer when required then the aggregate of hold-queues specified under classes in SCHEDULE should never exceed the 200 specified for the hold-queue for class-default of TEST?

many thanks for any insights here.

cheers,
Ben.

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Received on Mon Feb 27 2012 - 09:35:08 ART