I'm on ADSL with a slow link. Only 4.5 Mbit down/1Mbit up.

When the upload is satturated, the download slows to a crawl - this is well documented behaviour common to ADSL that has something to do with too many ack packets not geting through and/or the router unable to process ack packets fast enough.

QOS is supposed to help - the default clearOS QOS gives highest priority to non-TCP packets (includes ack packets ) so it keeps up.

In practice I'm finding that QOS is not helping.

What does help is to install the old app-bandwidth and set a ceiling rate on uploads that is a little below the maximum (e.g. I throttle uploads to 900kbit when the link is capable of 1000kbit up)

This instantly restores the download speed.

So my Q's.

Why doesnt QOS help?
Why do people say app-bandwidth and app-qos dont play well together? I have them both installed now and can't see any miss-behaviour but not sure what I should be looking for. I'd like to keep QOS around as we run VoIP phones... but only if its useful. app-bandwidth actually seems to solve our VoIP stutter (due to people uploading) better than QOS did.

What am I missing?