Subject: Re: [PATCH 2/3] [VLAN]: Update iif when receiving via VLAN device

From: Patrick McHardy <[email-masked]>
Date: Tue, 27 Jun 2006 00:49:30 +0200

Patrick McHardy wrote:
> All my testing (quite a lot) in this area so far suggested that queueing
> at ingress doesn't work and is actually counter-productive. It gets
> worse with increasing signal propagation delays (signal in this case
> means congestion indications). I actually wish I never introduced
> the stupid IMQ device, it raises false hope and a lot of people seem
> to fall for it.

Small clarification: with queueing at ingress I mean queueing after
the bottleneck. It might work if you introduce a virtual bottleneck,
but in that case in my experience the bandwidth limit you have to use
is dependant on the number of TCP flows, so usually you can't specify
a limit that will always work, and its wasteful if there is a smaller
number of TCP flows. The reason why you would do it, limiting or
prioritizing incoming traffic on the _real_ bottleneck, is not
achievable of course. Also noteworthy is that policers don't behave
any better, and any other schemes I've tried (I also experienced a
lot of with TCP rate control) have similar or related problems.