Message-ID: <4B19276F.5080604@roinet.com>
Date: Fri, 04 Dec 2009 10:14:55 -0500
From: David Acker <dacker@roinet.com>
MIME-Version: 1.0
To: Kalle Valo <kalle.valo@iki.fi>
CC: linux-wireless@vger.kernel.org, patrik.flykt@nokia.com
Subject: Re: WMM classification guideline for applications?
References: <87d42u6dnd.fsf@purkki.valot.fi>
In-Reply-To: <87d42u6dnd.fsf@purkki.valot.fi>
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Sender: linux-wireless-owner@vger.kernel.org

Kalle Valo wrote:
> Hello,
> 
> me and Patrik have been pondering what's the proper way for user space
> applications to do packet classification to get the benefits from WMM.
> VoIP application is a good example here.
> 
> For the time being we have identified three different methods:
> 
> 1. SO_PRIORITY with values 0-7 (we used this in nokia n810)
> 2. SO_PRIORITY with values 256-263 (used by mac80211)
> 3. IPv4 DSCP field with values 0-7 (used by mac80211)
> 
> Method 1 is easy, applications need to just use setsockopt() and be
> done with it. I don't know how widely supported values 0-7 are, but at
> least they make sense. The problem is that priority is used only in
> the first link, rest of the route is not able to benefit from the
> classification.
> 
> Method 2 (priorities 256-263) doesn't sound very portable. I doubt if
> any other stack or driver (even non-wifi ones) use these values.
> Otherwise this is similar with Method 1.
> 
> Method 3 (IPv4 DSCP field) feels most portable to us, at least most,
> if not all, wifi drivers should use it. And, in theory, the receiver
> should also benefit from the classification, unless ISPs modify it of
> course. But the standardisation for IPv4 QoS bits is a mess and I
> don't really understand where the use of DSCP bits (as used in WMM
> implementations) is specified. Also I was told that root privileges
> are needed to set this and that's somewhat cumbersome from application
> developer's point of view.

What do think of also supporting a method 4, VLAN priority field (0-7)?
-ack