Re: Quality of Service in GNOME

[Samuel Abels <newsgroups debain org>]

On Sa, 2005-09-17 at 00:58 +0100, Alan Cox wrote:
> On Gwe, 2005-09-16 at 23:06 +0200, Samuel Abels wrote:
> > kernel-level scheduler/queue. For example, give the application that has
> > currently focus a higher network priority, or make that VoIP application
> > work perfectly even if you have a few downloads/bittorrent running, etc.
> 
> Except in special cases it won't help much. Marking bulk transfers
> appropriately can help a little as can marking interactive traffic but
> really only for outgoing traffic. Big routers don't have big enough
> queues to do anything. In addition capture effect on the network means
> the highest rate incoming stream will tend to hog the system the moment
> you meet 100% bandwidth utilisation.

Yes, the scheduler mainly helps for outbound traffic. However, using
traffic shaping and/or ECN there is also a good way for improving the
inbound traffic behaviour. Even without ECN, the TCP mechanisms can
still be used in conjunction with mechanisms like RED to discourage
specific (i.e. aggressive) streams.

> That isn't to say applications shouldn't support options to limit their
> data rate - gftp has this and for a modem in particular its a real
> godsend. Most good VoIP tools do bandwith limiting controls too.

Implemented properly, traffic shaping can provide the same
functionality, with the added benefit that it is completely dynamic and
transparent (configuration-free) to the user.

-Samuel