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Queue-limit 10G interface SIP601 - 12404

I’m trying to define the queue-limit for a QoS policy to apply on the output of a 10G interface/ SIP6-01 (12404 system):

policy-map EGRESS

class class1

  bandwidth remaining percent 2

  queue-limit <size> packets

class class-default

  queue-limit <size> packets

  bandwidth remaining percent 98


The LC output (FrFab) buffers resources are as follows:

Pool 1- 94155 buffers for 80 Byte data size

Pool 2 - 57389 buffers for 608 Byte data size

Pool 3 - 109849 buffers for 1616 Byte data size

Total buffers: 262142

I would like to receive suggestions for the queue limit that I should configure for each class without running out of buffers resources!

Super Bronze

Queue-limit 10G interface SIP601 - 12404


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There are a couple of approaches you might take; depends on your goals.  You could set queue limit based on how much latency you're willing to allow.  Or, you could also set queue limit to support BDP.  Actually configuration will be influenced by whether you want to allow for maximum size packets or your average size packets and, when working with multiple classes, will also be influenced by whether you want allow for the bandwidth allocated for a class, the maximum interface bandwidth, or average bandwidth normally available to the class.

For example:

10 ms @ 10 Gbps is 12.5 MB.  If we were then going to allocate based on 1500 byte packets, queue depth would be 8,333 packets.  (NB: probably more buffering than your hardware supports, but this is what 10 ms queue limit would require.)

If RTT was also 10 ms, BDP buffering would be the same for the same size packets.

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