From: Sam Munzani (sam@munzani.com)
Date: Thu Mar 06 2003 - 12:59:25 GMT-3
This is what I am doing now. To get information about how much traffic is
being dropped because of burst causing buffer problem. I am going to collect
the Input/Output queue drop rate for every 5 min cycle. Compare this drop
rate to the interface bandwidth. If I see .25% packet in drop rate, it would
make sense to get more bandwidth. Drop rate less than that is caused by
occational burst and doesn't justify more bandwidth.
Thanks a lot to all people who provided their input.
Sam
> In the other engineers opinion, would you see the performance hit
> because the "3640 supports only 75000 pps with 64 bytes packets"? I can
> assure you a T1 wouldn't show performance loss until virtually 100% for
> the same reasons you said. Hell, an old 2500 with minimal memory and
> old IOS can handle routing a full t1 (actually we have situations with a
> 2500 running MLPPP using 2 T1s and can handle that with both pipes
> packed). A 3640 can handle a boatload more than one T1. We also use
> 3640s to handle our two PRI dialup (which is the same bandwidth as T1s)
> and it's CPU never gets above 10%. I've also used a 2610 to trunk
> multiple voice T1s (again same bandwidth, different application), and
> even a 2610 can handle it, and a 3640 smokes a 2610...... AND the 3640
> has the same CPU as the 4700 routers, and we're using 4700s to handle
> 155Mbps OC-3. Your friend is whack!
>
> Mike W.
>
> -----Original Message-----
> From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf Of
> Sam Munzani
> Sent: Wednesday, March 05, 2003 9:51 AM
> To: ccielab@groupstudy.com
> Subject: At what percentage of T1 utilization you should see performance
> degrade?
>
>
> Hi,
>
> Today we got in to a debate about T1 saturation and performance
> degradation. Below is 2 different opinions from my self and other
> engineer.
>
> What I say.
> T1 is a full duplex mechanism. So until it hits 100% utilization on it's
> Serial(Full T1) interface it will forward to packet and no packet drop
> will happen. Only the time it will do a queue drop is when the traffic
> bursts above 100%. This queue drop is because of Serial interface short
> on forwarding buffers. Same behavior will happen on inbound. Only the
> time this would be a bottleneck is if router CPU is a bottleneck. This
> is on 3640 with Fast switching turned on. I am assuming 3640 can handle
> more than 1 T1 bandwidth.
>
> The other engineer's opinion.
> 3640 supports only 75000 pps with 64 bytes packets. His opinion is, your
> users will see performance problems even before T1 is hitting
> 100%(aroung 70 to 80%).
>
> Any opinions with enough supporting proofs are most welcome.
>
> Regards,
>
> Sam Munzani
> CCIE # 6479(R&S, Security)
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