From: Jon Carmichael (jonc@xxxxxxxxxxx)
Date: Sun Feb 10 2002 - 03:43:14 GMT-3
I'm having lots of fun here trying to make WRED work. Following the book IP
Quality of Service, by Srinivas Vegesna for those of you who might have the
book or are interested in making this work. I'm struggling with the
relationship between WRED and CBWFQ, and why I'm being forced by the IOS to
treat those two as the same, perhaps WRED is a subset of CBWFQ?
I'm working an example similar to his on page 134, but not getting the
results I would like. I've done this on a 2500 and a 4500 with the same
result, and that is that it keeps thinking that I'm doing CBWFQ, when I want
to make WRED drop some packets. I'm setting my minimum-threshold to 2, my
maximim threshold to 4 for all precedence levels, where I think I can
generate enough tcp packets so force some drops, but the problem is that my
interfaces think it's CBWFQ as soon as I put a service-policy on them, when
what I thot I wanted is WRED.
Of course RED, is not WRED, and if you do "random-detect" on the interface,
you don't get to mess with weights, but a service-policy, to follow the
example in the book is coming up as CBWFQ. Even after I put "random-detect"
in my policy-map, I am still required to put a "bandwidth" before I can set
things like the "exponential-weighting-constant" or the "random-detect
precedence..." Of course once I apply the policy-map to the interface it
pops up with a queueing strategy of CBWFQ, where I was hoping to see WRED.
The relevant parts of my configuration are below..
* * *
class-map non-critical
match access-group 101
!
!
policy-map SET-WRED
class non-critical
bandwidth 8
random-detect
random-detect exponential-weighting-constant 3
random-detect precedence 0 2 4 1
random-detect precedence 1 2 4 1
random-detect precedence 2 2 4 1
random-detect precedence 3 2 4 1
random-detect precedence 4 2 4 1
random-detect precedence 5 2 4 1
random-detect precedence 6 2 4 1
random-detect precedence 7 2 4 1
!
* * *
JONC
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