DSCP marking for QoS

Unanswered Question
May 17th, 2007

I'm working on a QoS mechanism. NBAR looks like the most straightforward way to get at most of the protocols, but I need to set the DSCP bits for the MPLS provider to respect my classes.

Do I need to mark the packets at ingress on the dot1q trunk to the switch, or should I do all the queuing, marking, and nbar on the outbount interfaces? What if I have my own VPN as a potential outbound path and want to replicate the same QoS classes, does it start to make sense to mark at ingress instead of egress?

I have this problem too.
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mohammedmahmoud Thu, 05/17/2007 - 04:44


I'd recommend doing the classification and marking on the ingress, in order to be effective whatever the outgoing interface is, accordingly C&M will be done once.

Please don't hesitate for any further question.

HTH, please do rate all helpful replies,

Mohammed Mahmoud.

royalblues Thu, 05/17/2007 - 05:52

Classification and Marking should be done as close to the source as possible. This might require that you classify them at the switchport level.

If you do not want to mark and classify the traffic at the switches, you can configure the trunks to just trust the DSCP settings.

On the edge routers, just match these DSCP settings and apply your QoS accordingly.

If you want to make sure that the dscp settings are passed to the provider, you can set them again under the policy map applied on the outbound interface

HTH, rate if it does



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