From: Chris Lewis \(chrlewis\) (chrlewis@cisco.com)
Date: Tue Sep 06 2005 - 23:41:33 GMT-3
Shun and Simon,
I believe your questions are in fact resulting from the same issue.
Before MQC came about, each platfrom had its own QoS configuration. MQC
is an attempt over time to bring a common method of configuration to all
Cisco platforms. The idea is that if for example you want to assign
bandwidth to a class, you can use the bandwidth command in MQC on all
platforms. Some platfotms may use different mechanisms to ensure that
the bandwidth is assigned. The 3550 uses WRR, the 12K uses MDRR, others
use something else, but the result is intended to be the same, whatever
actual mechanism the platfrom uses to assign bandwidth is transparent to
the one configuring MQC, just the bandwidth command needs to be
configured and all the rest gets worked out under the hood.
However some platfroms (like the 3550) do not have the hardware
necessary to complete these migrations.
Also software gets re-used from platform to platform and some things can
be configured that are not actually supported on a per platfrom basis.
So we get to this situation, where you can use MQC to configure say a
policer on the 3550 and it works, but not bandwidth allocation, that is
still by the legacy wrr-queue configuration.
By configuring different weights for the different queues, and assigning
the traffic you want to the queues (with wrr-queue cos-map), you can
effectively give different bandwidth guarantees to different traffic
types.
Chris
-----Original Message-----
From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf Of
kumara.shunmugam@wipro.com
Sent: Tuesday, September 06, 2005 6:11 AM
To: ccielab@groupstudy.com
Subject: 3550- "bandwidth & Priority" Policy-map commands
Hi
Can any one comment on the above two command support on Cat3550. Many
forums say that the 3550 will not properly support bandwidth command
under policy-map (egress queue). If we want to change the bandwidth, the
only way is to go is by using "wrr-queue bandwidth command. But I think
the wrr-queue bandwidth command is the mechanism to assign weights to
each queue. Where as the policy-map will provide minimum bandwidth
guarantee for an identified traffic during time of congestion. Can
anyone discuss the policy-map limitations in 3550?
Regards
Shun
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