Return-path: Received: from ebb.errno.com ([69.12.149.25]:2766 "EHLO ebb.errno.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1758386AbYBTXwv (ORCPT ); Wed, 20 Feb 2008 18:52:51 -0500 Message-ID: <47BCBD4B.6080602@errno.com> (sfid-20080220_235254_613262_CACDD6CE) Date: Wed, 20 Feb 2008 15:52:43 -0800 From: Sam Leffler MIME-Version: 1.0 To: Guy Cohen CC: Tomas Winkler , Johannes Berg , linux-wireless , Ron Rindjunsky , Nick Kossifidis , Michael Renzmann , "Luis R. Rodriguez" , bruno randolf Subject: Re: implementing APSD? References: <1203521087.17534.74.camel@johannes.berg> <1ba2fa240802201043v1bd4fbddsc55c2230eb2a1480@mail.gmail.com> <47BC76FC.7070109@errno.com> <247d6d340802201511u59b56ac8g128b28147fe92176@mail.gmail.com> In-Reply-To: <247d6d340802201511u59b56ac8g128b28147fe92176@mail.gmail.com> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Sender: linux-wireless-owner@vger.kernel.org List-ID: Guy Cohen wrote: > On 2/20/08, Sam Leffler wrote: > >> Tomas Winkler wrote: >> >>> On Feb 20, 2008 5:24 PM, Johannes Berg wrote: >>> >>> >>>> Hi, >>>> >>>> I've long thought about implementing APSD but it seems to require >>>> setting the "more data" bit in an ACK frame and various other things. >>>> Ron, I think you're the QoS expert, is that really how APSD works? If >>>> so, does iwl firmware implement that? >>>> >>>> >>> We have uAPSD implementation, mainly AP part, yet again it for older >>> mac. It will take a bit time to merge it in >>> It's a mandatory feature for HT AP. >>> >>> >> Really? Can you point where that's called out in the spec? >> > > You can not get WFA 11n certification without getting first WMM-uAPSD > certification. > > 4965AGN uCode image supports uAPSD in client mode (and certified under > Windows). uAPSD in AP mode is under developement currently. > Maybe your comment refers to a later version of the WFA spec than I have (D2.0 from 2007). I'd be curious to hear of products that actually make use of uapsd (I'm aware of a few but they typically work only within a closed system). > >>>> Also, does Atheros hardware implement that, and how? It doesn't look >>>> like Broadcom firmware implements it, and I don't really understand how >>>> one could implement it without many hardware queues, since it seems >>>> timing critical to send out the frames to the station that is using >>>> APSD. >>>> >>>> >>>> >>> Don't believe it's possible to that without HW support. >>> >>> >> Sorry, this is incorrect; you can do UAPSD w/o any special h/w support. >> >> Sam >> > > I think you may do uAPSD client mode w/o special HW/FW support (though > it won't be optimized), but definitelly not AP mode - you need some RT > capabilites for tracking the client state (wake/sleep/doze) and stop > sending frames to a client that entered a sleep state, need to avoid > out-of-order transmission when rescheduling frames that were dropped > because a client entered sleep/doze state, Service Period control, > etc. > > I guess this comes back to the question of what must be done in hw vs sw. You say it's gotta be done in hw. I know it can be done in sw but you need hw that's designed to support a model where the host is responsible for this sort of stuff. Sam