6500 : Tx Queue Sizes

Unanswered Question
Feb 13th, 2009


I read that by default there are different Tx Queue Sizes for different queues available.

1. Can we change the Tx Queue Size of Priority Queue ?

2. I guess we can change the Tx Queue Size of Standard Queues by <<wrr-queue bandwidth X Y Z >> command. Plz confirm..



I have this problem too.
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Giuseppe Larosa Fri, 02/13/2009 - 08:30

Hello Gaurav,

in C6500 for its high modularity capabilities and default values are linecard model dependent.

However, you should be able to tune them within the allowed range for a specific linecard.

For some linecards there can be even more varations depending if they mount a DFC or not (not sure of this but it can happen)



and table 41-3

Weighted Round Robin (WRR)-WRR does not explicitly reserve bandwidth for the queues. Instead, the amount of bandwidth assigned to each queue is user configurable. The percentage or weight allocated to a queue defines the amount of bandwidth allocated to the queue.

Hope to help


gauravprakash Sun, 02/15/2009 - 21:21

say on Sup 10G 3C supervisor port , can we change the TX queue value for Strict Priority class ?



Giuseppe Larosa Mon, 02/16/2009 - 05:01

Hello Gaurav,

see table 37-2 in following doc


notice that the queues structure changes if you decide to disable the GE ports on the supervisor linecard

for tx queues the structure is


1p7q4t indicates the following:

-One strict-priority queue

-Seven standard queues, each with four thresholds, each threshold configurable as either WRED-drop or tail-drop

this should mean that you cannot choice the size of the priority queue

Actually a strict priority queue is served until the queue is empty: this is the meaning of strict priority queue so its size is in some ways less important then in normal queues

Hope to help



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