Line Rate vs CPU utilization info requested

Wed Feb 27 21:57:13 UTC 2002

I have run a DS-3 with T-1 backup and an ethernet at near full capacity on a
3640 with
no noted performance problems.  The CPU load was about 35%.  It has been my
experience that
the CPU load seems to be affected more by the number of running protocols
and the number of
access lists than traffic forwarding.  Once the routing tables are stable
and lines are up,
the CPU load does not get affected too much by changes in traffic unless
there is alot of
access list processing.

Another point is to find out what the backplane speed limits are because I
think your problem
running 800Mbps on the 3640 is not a processor constraint but a backplane
bandwidth constraint.
Cisco shows the capacity at 70,000 packets per second.  To give you an idea
of how much power
this is, one of my 7500 routers is running an OC-3 at about 48 mbps and it
shows me that is
equal to about 12,000 packets per second.  If I extrapolate these numbers I
come up with roughly
280 mbps as the rough capacity of the 3640 platform.  My traffic is service
provider transit so
it should be a good mix of packet sizes.

I would have to say that the 3640 will handle a fully loaded DS-3 and a
fully loaded ethernet
connection.  Every Cisco I have worked with will be more hurt processor-wise
by overly long
access lists and flapping protocols more than bandwidth.

Steve

> -----Original Message-----
> From: owner-nanog at merit.edu [mailto:owner-nanog at merit.edu]On Behalf Of
> Donn Lasher
> Sent: Wednesday, February 27, 2002 11:33 AM
> To: nanog at merit.edu
> Subject: Line Rate vs CPU utilization info requested
>
>
>
>
> Does anyone have a table / web site / etc that talks about realized IP
> throughput on various routers (3600 / 7100 / 7200, 5500, 6500,
> etc) versus
> cpu load? IE even though you can put 4 x 100M ethernet cards in a 3640,
> IMHO, you'd never see 400/800M aggregate throughput because the CPU would
> be on its' knees begging long before that point.
>
> I'm looking at a project that calls for a DS3, and the suggested
> router is
> a 3640, and I'm trying to prove / document that's not a wise
> idea. What has
> your experience been? Anecdotal or personal experience
> appreciated. Offline
> replies work just as well.
>
> Thanks in advance.
>
> -donn
>