[c-nsp] 2960 -> 4948 - no more drops :)

Robert Hass robhass at gmail.com
Sat Feb 16 18:27:31 EST 2013

> We recently upgraded a 2960G(Only doing L2) that was hitting ~500Mb/sec on one port, and we were seeing 40,000+ output drops (5Min) - Since the swap to the 4948, we see zero output drops. Is the difference in performance purely buffer size?  I *think* the 2960 has 1.9Mb (Per ASIC) and the 4948 has 16Mb (total?)?

It can also be default srr-queue configuration if mls qos was enabled.

Try connect host again to 2960G but configure 'srr-queue bandwidth
shape 0 0 0 0' on all ports before.

You can also :
- assign all traffic to one particular queue which increase amount of
buffers (eg. all dscp's to queue2)
- reconfigure (increase) thresholds for queue2

1900000/24 ports = (79166 / 4 queues) * 8bits = 160Kbit per queue

No so much. IMHO Cat4948 has more dynamic buffering instead of static
allocation per port / per queue.


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