From: Malcom Sargla (msargla@rim.com)
Date: Thu Mar 19 2009 - 12:32:47 ART
Dear Folks,
We are currently testing qos extensively in our lab and I'm at the point
now where I'm trying to decide to use fair-queuing or cbwfq for class
Class-default.
To expand, we've done our homework to create efficient class-maps and
respective acl's so Class-default should never really see any traffic
once we go live with our policy. However, under testing we wanted to
traffic stress class-default in order to understand the true behavior of
qos as a whole.
We found under a traffic saturation test ( where all 4 classes were
stressed) that when fair-queue is applied to Class-default that it
actually consumes about 3% more traffic then we expected it would.
However when I fix bandwidth percent X and random-detect on
class-default it consumes approximately the remaining bandwidth and does
not grow into another class.
Question - Opinion's
- What would be the pro's or con's of using CBWFQ with
bandwidth percent and random detect over WFQ? I know WFQ provides
another level of intelligence in deciding how to queue packets and
provide fairness but I don't think we need it. On the other hand CBWFQ
only considers 'bandwidth percent' as a weight when deciding to how to
divide additional bandwidth so I'm not sure if fixing a percentage to
Class-default is a good idea, particularly if we have other, more
important classes that we would like to dynamically grow if under times
of congestion. Essentially I don't want class-default to have the
lion's share of bw over another defined class.
- Secondly, CS6 router traffic - my understanding is that
pak-priority is given to -all- igp routing protocols by default on most
new ios - pak-priority (cs6) traffic is essentially treated similarly to
llq traffic in that it is forwarded to the tx ring before all other
traffic. However, pak-priority does not apply to BGP - how do most
people handle this? Set up an access-list, class, and set CS6 or is
there another preferred configuration to prioritize BGP routing updates
when peering with an external neighbour?
Thank you very much in advance,
Malcom.
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