[c-nsp] Router/Switch Sizing terms

[Sukumar Subburayan]

While we are on this topic, I just want to mention that for 
Catalyst 65xx/76xx from SXF based releases we added 
'show platform hardware capacity' to give a snapshot of all the current HW 
capacity and usage, for various capacity planning purposes.

sukumar




On Mon, 8 Jan 2007, Justin M. Streiner wrote:

> On Mon, 8 Jan 2007, Pete Templin wrote:
>
>>> 3) Switching Capacity
>>
>> L2 devices switch packets from ingress to egress.  L3 devices route, and
>> then switch packets from ingress to egress.  Either method requires an
>> appropriate (L2, L3, etc.) lookup, one time per packet regardless of
>> packet payload size, and therefore most switches and routers are
>> performance-limited by the number of frames/packets they can perform
>> switching/routing lookups on (and then switch the packet to the egress
>> port).
>>
>>> 4) Forwarding performance
>>
>> Often a measure of switching capacity multiplied by minimum, average,
>> weighted, and/or maximum packet size.  Used to differentiate between
>> devices that can only fill their ports if maximum-sized packets are
>> used, and devices that can fill their ports if minimum-sized packets are
>> used.
>
> Also, sometimes it's well worth taking the performance numbers that a
> vendor gives you with a healthy grain of salt.  A vendor can make a claim
> like "Our new ABC9000 platform will forward up to 40 million packets per
> second", but without knowing exactly what this number means and how they
> arrived at it, i.e. what tests they used, etc, it's at best disingenuous
> and at worst flat-out wrong.  Packet forwarding tests need to discuss
> forwarding performance at a wide range of packet sizes.  This is
> especially true for a router, or a switch that has routing functionality.
> Small packets, especially lots of small packets, are generally more
> taxing, especially on a software-based router.
>
> Also important to know are:
> * Does the device (route|forward) in hardware or software?
> * If it does so in hardware, what conditions exist that could cause it to
> (route|forward) in software?
> * What is the performance impact of doing so?
>
> If you're dealing other features like NAT or IPSEC, those will often have
> their own sets of performance numbers.
>
> jms
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