Where to apply Qos

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Aug 25th, 2008
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I am currently experiencing congestion on my link to branches, so i will like to apply Qos. My problem is I am using tunnels to the braches from the backhaul, through the ISP cloud to the braches, my proble now is should i apply the qos on physical interface, how will i apply it on the tunnel, if i can,

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Giuseppe Larosa Mon, 08/25/2008 - 01:31
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Hello Just,

the answer is IOS release dependent.

I suggest to try to apply the service policy on the tunnel interface first.

If the CLI provides error messages

you need to config on the physical interface in this case you need to mark traffic on the inside with different DSCP byte or TOS and the service-policy will have to match on DSCP value or IP precedence

Hope to help


Joseph W. Doherty Mon, 08/25/2008 - 03:57
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If the congestion you're experiencing is outbound on the physical interface at your main site, that's where you should apply your QoS policy. If the traffic is already marked before it enters the tunnels, you can use those markings at the physical interface. Otherwise, you'll need to use the QoS pre-classify (see Faisal's reference) on the physical interface. (The latter assumes the tunnels are sourced on the same device.)


If there's also congestion egressing the ISP cloud to a branch, you either need to rely on the ISP to apply QoS or you'll need to shape your tunnel to correspond to the branch link's bandwidth.


If the sum of all your tunnels' bandwidth don't exceed your main link's bandwidth, and there isn't any other traffic on the links, you could also just shape all the tunnels to match the branches link bandwidth.


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