Cisco 3750 Latency

Unanswered Question
Mar 25th, 2009

Hi,

We currently deploy Cisco 3750 series switches and our clients are constantly requesting latency information on these.

Can you please advise what the latency across the box is at different frame sizes. For example:

64 byte packet

256 byte packet

1512 byte packet

9216 byte packet

Many Thanks,

Sunny

I have this problem too.
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sonisnr01 Wed, 03/25/2009 - 10:04

Hi,

Thanks. I have been qouting these figures, however I need latency figures for specific frame sizes, ie:

64 byte packet

256 byte packet

1512 byte packet

9216 byte packet

Thanks,

Sunny

Joseph W. Doherty Wed, 03/25/2009 - 10:32

I haven't seen anything with that level of detail. If no one else responds, you might try TAC. Otherwise, assuming the information we do have is for minimum and maximum frame sizes (i.e. 94 and 9216), you could interpolate for 256 and 1512.

PS:

I'm curious why your clients need this level of detail. With modern switches, for most things, other latency factors would be much more significant, e.g. transient congestion.

If 7 to 26 us, alone is an issue, then you may need "low latency" switches, such as Cisco's InfiniBand Switches. Even for those, I didn't notice a specification for multiple frame sizes.

sonisnr01 Wed, 03/25/2009 - 10:53

Thanks Joseph.

Recently customers are getting latency sensitive due to the applications they are using. Selling Ethernet services over an Ethernet backbone is relatively easy, but customer are now requesting figures. The latency does not just end with the boxes, but we also take into account the distance from client site to client site. Providing and end-to-end latency calculation.

To accurately provide figures, I need to know exact numbers, rather than adding 26us. These client applications are now measuring latency in Microseconds, so we need to be accurate.

Thanks again.

Sunny

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