[c-nsp] Typical Cisco router (12000/7600) per-box latency for packet switching?

[LJ Wobker]

This is correct... the hardware based platforms all move packets around so
quickly that the *uncongested* latency values are essentially meaningless.
The network impact of 20 microseconds vs 100 microseconds vs 500
microseconds is functionally nil.

Bill's comment about circuit/buffer sizing is spot on: What you need to pay
attention to is how well the system manages latency in the case of
congestion: specifically the ability to provide voice traffic with low and
predictable latency values regardless of how badly oversubscribed the other
queues are.

--lj

On Mon Sep 25, 2006 at 06:02:49PM -0400, Bill Wichers wrote:
>> Are there known, typical latency values added to
>> packets by a single hop high-end Cisco router
>> like the 12000 series and 7600 series?
>>
>> I'm sure this one is a really multifaceted issue,
>> but it would nonetheless be very enlightening to
>> find experiences and recommended documents
>> about it.
>
>For "real world" latency you have to consider circuit congestion and
>buffer sizes. Cisco I believe does specify the latency for a "Cisco Cell"
>traversing the 12000's switch fabric, which is in the microsecond range if
>I remember correctly. I've never seen anything specified for the 7600
>series, but then again I haven't ever really looked either :-)
>
>I would imagine that the 7600 latency would be very similar to, if not the
>same as, latency on the 6500 platform since they're essentially the same
>on the hardware side.
>
>     -Bill
>
>
>*****************************
>Waveform Technology
>Systems Engineer
>
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Lawrence J. Wobker   "Highly trained network monkey"    lwobker at cisco.com
CCIE #5020         Technical Marketing Engineer, Routing Technology Group
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