[aclug-L] Re: Ideas for Sept Aclug Meeting?

[Chris Owen <owenc@xxxxxxxxxx>]

On Fri, 3 Sep 2004, Jonathan Hall wrote:

> An interesting side note when comparing CPUs for routers... I believe
> many Cisco routers use 486-type CPUs (perhaps even exactly 486 CPUs...
> Someone on this list I'm sure knows more precisely).  I do know that the
> Portmaster 3 terminal server I used to use when I ran an ISP used a
> 486/66 CPU, and the Portmaster 2 uses a 386/33 CPU (if memory serves).
> And both of these machines do much more than the typical "Linux router"
> in terms of bandwidth usage.

While I certainly wouldn't argue that a low end CPU isn't completely fine
for a home linux router, comparing the CPU in something like a Cisco
router or a PM3 to that in a linux router is really comparing apples and
oranges.

Yes a PM3 only had a 486 in it but really the CPU in a box like that
doesn't do much more than run the command line.  The thing is loaded with
DSPs and other chips that do most of the real work.  Usually your linux
router isn't going to have any of these things.

A Cisco 7200 doing standard routing on several DS3s worth or traffic is
going to have a CPU load of about nothing.  However, as soon as you start
putting a bunch of policy routing and other things that the CPU needs to
think about you can melt it with probably no more than a DS1's worth of
traffic.

Ironically for that reason a linux router can usually do much better than
a Cisco when it comes to things like policy routes or NAT.  The Cisco
boxes are just designed to offload the real work elsewhere and as soon as
the CPU has to do much they can get in trouble fast.

Chris

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