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queue-limit and hw-buffer

hi,

my question:

i have a router with a serial frame-relay link.

on this link i enabled cbwfq - gold,silver queue.

i saw a lot of drops in the gold-queue, so i tuned the gold-queue with the "queue-limit" command - and now it is ok.

my question is a general on:

is there a relationship between the "queue-buffer" and the "hardware-buffer" from the interface.

in my understanding it is necessary to increase the hw-buffer (tx-ring) if i increase the softwarebuffer in the queues - right.

i did a lot of search on cco but i did not find the right paper.

is anyone out there who has a technical describtion of this relationship??

thanks a lot and greetings from austria

  • WAN Routing and Switching
2 REPLIES
Purple

Re: queue-limit and hw-buffer

Greetings from Australia to you !

The "queue-limit" command configures the size of the software queue. The "tx-ring-limit" command configures the size of the hardware queue.

When using a fancy queueing mechanism like CBWFQ on an interface, IOS will automatically set the tx-ring size to a smaller value. You can tune this further using the tx-ring-limit command. In general, when using software queueing, you want the tx-ring size to be as small as possible (while being large enough to drive the interface to full capacity).

So the answer to your question is: NO, you do not need to increase the hw-queue size when increasing the software queue-limit.

Hope that helps - pls rate posts that help.

Regards,

Paresh

Re: queue-limit and hw-buffer

Don't know if you knew this one already:

http://www.cisco.com/en/US/tech/tk543/tk757/technologies_tech_note09186a0080103eae.shtml

I hope it comes close to what you are looking for.

Regards,

Leo

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