Subject: Re: multiple Tx queues
To: Sam Leffler <firstname.lastname@example.org>
From: Greg Troxel <email@example.com>
Date: 01/11/2004 13:17:40
The Atheros 5212-based cards support multiple xmit queues and
implement a variety of queueing policies in h/w. This stuff is
explicitly intended to supoprt QoS as set out, for example, the WME
spec. Applications include VoIP and streaming video. To
effectively use this stuff applications need to be able to tag
packets and have the OS stay out of the way except to not smash the
tag before it reaches the driver (where it can be used to select the
I haven't read the WME/802.11e specs yet.
Why couldn't this be handled by an application setting the TOS (er,
DSCP) with a setsockopt, and having the driver sort into queues based
on the DSCP? If there is a qos mechanism for sending packets over
wireless, then I would think it useful for it to work on packets
originated on a wired host that are being forwarded by another host
over wireless (e.g. connection sharing over Ethernet, etc. of a host
with an 802.11 connection).
I realize that the above is perhaps harder in general than having
driver-specific tagging rules, but something that said that
IPTOS_PREC_IMMEDIATE and higher got the high-priority queue would be
pretty easy to implement in the driver.