From: Colin Barber (Colin.Barber@telewest.co.uk)
Date: Wed Mar 05 2003 - 14:53:16 GMT-3
75,000 packets per second with each packet 64 Bytes is a throughput of
around 38Mbps. How many of your packets are going to be just 64 Bytes? If
packets are larger then the throughput goes up.
What does happen though on a slow serial link that is utilised above 80% is
there is not enough bandwidth to cope with bursts of data without buffering,
and maybe dropping, packets. This increases latency and also could causing
problems with routing updates/hello packets being dropped. This is why Cisco
recommend a maximum average of 80% utilisation on a serial link.
Colin
-----Original Message-----
From: Sam Munzani [mailto:sam@munzani.com]
Sent: 05 March 2003 15:51
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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