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WFQ and ADSL ?


I have a cisco 1721 router along with an ADSL WIC (and ADSL line), which work fine.

When one of the LAN user sends through ftp a large file to an external server, it renders every over external access sluggish (ssh, telnet, dns and even web browsing are suffering).

Looking at either interface (FastEthernet, ATM, Dialer), they do not seem to exhibit output drops, but they are all setup as FIFO queue.

From what I understood in the documentations, WFQ could solve my issue. I then wanted to activate it on the Dialer (output interface), but it does not help (mainly I guess because the only interface that knows the bandwidth is the ATM one).

Putting the WFQ on the ATM interface does not seem to be supported.

Oh and I forgot to say that the router is also doing NAT (overload).

The router has plenty of free memory and is using about 15% of CPU.

What should I do to solve this issue ?

I can post the actual configuration, if needed.




Brice Figureau


Re: WFQ and ADSL ?

it won't make much difference because it is only sorta running "weighted" fair queue. The weight is the precendence of the packets and unless you change it all will be the same. Just fairqueue will make interactive stuff a little better but you will still see the large FTP transfers impact.

If you set the precendence of all your traffic to say 2 and leave the FTP at 0 (which is default) the weighted part will take effect. In this example each user would get 2 times the bandwidth of FTP traffic.

Be sure you are appling this to the correct side of the link. There is little you can do if the traffic is inbound and you do not control the far end of the link. If the far end is a ISP the issue is almost always incoming traffic and not outgoing and you will need to contact your ISP to do something.

Community Member

Re: WFQ and ADSL ?

Thanks for the answer.

The problem is outbound so it is ok, I can control it.

If I understood your answer, you're suggesting to add a CBWFQ in which I reserve a class for the ftp transfer and a class for the other protocols, is that right ?

Then on which interface should I apply this setup ?

(I think I must read some comprehensive text on QOS, as I'm really new to this topic :-))




Brice Figureau


Re: WFQ and ADSL ?

using CBWFQ is even more advanced where you can limit traffic and more finely control data that just WFQ.

You could put all non ftp traffic in a class and give it special treatment and/or police the ftp traffic.

You don't need to use classed based stuff you could just use route-maps and policy routing to set the precendence as the traffic enters the router.

Since you asked about class based I will give you a example that set the precedence using class based.

You can set your output interface to fairqueue which is actually "weighted" even though it doesn't say it.

class-map match-all matchftp

match protocol ftp

policy-map markpackets

class matchftp

set ip precedence 0

class class-default

set ip precedence 2

Interface fastethenet 0/0

service-policy input markpackets

This is just a simple use of precedence and letting WFQ do all the work. If you look up WFQ they have the math involved that shows how much each stream will get. You of course can use the Class Based on the output but this is more often used to commit bandwidth to traffic rather than restrict it.

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