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Community Member

Help with ATM OC3 module configurations

Hi one and all.

I am after some advice concerning ATM OC3 modules which I am about to install in a pair of 3640 routers. These routers form the main core devices in my network, and the ATM links will bascially be the backbone.

I have been able to get IP running OK over 2 main PVC's I have configured using sub-interfaces. Next I began thinking about weighted fair queueing, as this is what is controlling the frame-relay trafiic we have else where. So I checked the existing queueing on the ATM interface and the router tells me it is Per VC queueing. What is this and how does it compare to WFQ. The last thing I want to do is implement the ATM stuff and discover I have decreased throughput because of a bad queueing strategy.

There is a project underway to implement QoS on the network but as usual this will be done after I must have the OC3's working.

Any advice appreciated. Ta.


Re: Help with ATM OC3 module configurations

Per VC Queuing on the 3600 ATM modules is very simular to WFQ based on the fact that no one VC can compromise the enture BW. Traffic shaping is also a capability and this will help with your future QOS rollout. VC Queing is done basically by limiting the amount of TX Queues per VC. As for determining your queuing stradegy. You'll need to determine your application requirements and take a good measure of your network under normal and peak loads to determine what will suit your needs.

Here is a URL with some information about the 3600 ATM modules:

Hope this helps,


Community Member

Re: Help with ATM OC3 module configurations

Thanks Don.

I was able to place a policy map which uses the default classes. Next I put WFQ on each of the 3 PVC's I have defined. This seems to work OK. Using the show policy int command I can see each PVC using WFQ and the 8 traffic classes. At this stage everything is running at 0 (routine) except for the router stuff which is running at class 6 which is fine for now. I was more interested in the flow control than traffic marking or colouring.

Again, Ta for your help.

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