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

CiscoNSP_list CiscoNSP_list cisconsp_list at hotmail.com
Sat Feb 16 19:57:08 EST 2013

No...just genuinely interested in the differences between the 2 switches. 

Date: Sat, 16 Feb 2013 17:25:07 -0700
Subject: Re: [c-nsp] 2960 -> 4948 - no more drops :)
From: alex.presse at gmail.com
To: cisconsp_list at hotmail.com
CC: cisco-nsp at puck.nether.net

Not sure if guerrilla marketer trying to get readers to google this fantastic switch... 

On Sat, Feb 16, 2013 at 5:14 PM, CiscoNSP_list CiscoNSP_list <cisconsp_list at hotmail.com> wrote:

Hi Rob (Sorry for not replying inline, but hotmail screws the formatting)

We did try tuning qos buffers (It did improve the drops, but they were still significant), and we also tried disabling mls qos (Still saw significant drops)....Im really interested to know why there is such a difference between the two platforms....i.e. is it buffers/how they are allocated, architectural differences or combination of both?


> Date: Sun, 17 Feb 2013 00:27:31 +0100

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

> From: robhass at gmail.com

> To: cisconsp_list at hotmail.com

> CC: cisco-nsp at puck.nether.net


> > 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.


> Rob


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Alex Presse
"How much net work could a network work if a network could net work?"

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