Choosing WRED Min and Max Thresholds

Hi Gang,

I am trying to choose the best WRED Min and Max Thresholds for a DS3.

So far the best guide I could find was here:

http://www.cisco.com/en/US/docs/ios/11_2/feature/guide/wred_gs.html

However, neither the Cisco default values nor the recommended values on that
page make any sense.

For example, the default value for the WRED maximum threshold on a DS3
interface is 40 packets.

Assuming a maximum packet size of 1500 bytes that would mean the most
throughput you would get on a DS3 interface with WRED would be 40 packets *
(1500 bytes per packet) * (8 bits per byte) = 480,000 bps or 480 kbps.

Which means you would be at full drop at only 480 kbps?!?

Even if you took the recommended setting of 367 packets for maximum
threshold:

367 packets * (1500 bytes per packet) * (8 bits per byte) = 4,404,000 bps or
4,404 kbps (1/10 the bandwidth of a DS3)

I know the goal of WRED is to drop packets before you reach congestion, but
dropping all packets when reaching 1/10th of the DS3 bandwidth seems a
little ridiculous.

Am I missing something here?

Thanks,
Gregory Gombas
CCIE #19649

Blogs and organic groups at http://www.ccie.net
Received on Mon Nov 01 2010 - 09:34:26 ART