Return-path: Received: from wr-out-0506.google.com ([64.233.184.226]:4424 "EHLO wr-out-0506.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751350AbYHLR4r (ORCPT ); Tue, 12 Aug 2008 13:56:47 -0400 Received: by wr-out-0506.google.com with SMTP id 69so2024772wri.5 for ; Tue, 12 Aug 2008 10:56:46 -0700 (PDT) Message-ID: <43e72e890808121056ua211e66lbc7bc8d619390bfd@mail.gmail.com> (sfid-20080812_195652_683577_19712257) Date: Tue, 12 Aug 2008 10:56:45 -0700 From: "Luis R. Rodriguez" To: "Jouni Malinen" Subject: Re: Pondering: how to improve mac80211 roaming ... Cc: "Helmut Schaa" , "Holger Schurig" , linux-wireless@vger.kernel.org In-Reply-To: <20080812154223.GE4981@jm.kir.nu> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 References: <200808120838.52888.hs4233@mail.mn-solutions.de> <20080812082246.GD4981@jm.kir.nu> <200808121440.24098.hschaa@suse.de> <20080812154223.GE4981@jm.kir.nu> Sender: linux-wireless-owner@vger.kernel.org List-ID: On Tue, Aug 12, 2008 at 8:42 AM, Jouni Malinen wrote: > On Tue, Aug 12, 2008 at 02:40:23PM +0200, Helmut Schaa wrote: > >> JFYI I already started to rework the existing scan code in mac80211 >> (software scan) to do something like background scanning: >> >> 1) notify current AP about leaving the channel >> 2) scan one channel > > It might be useful to leave this "one" as a parameter to allow easy > experiments with scanning more than one channel at a time to reduce > latency. Ideally, this--along the interval for background scans--could > be something that is dynamically changed based on the expected traffic > pattern. Whenever there is lot of data traffic being (mostly > successfully) transmitted, it would be beneficial not to jump to other > channels as frequently or for as long a time. If there has not been any > data transmission for some time, it may be more acceptable to scan more > frequently and to remain away from the operational channel for longer > periods of time. Though, we should also keep in mind that background > scans are going to increase power consumption on otherwise inactive > situation, so setting a suitable policy for this can get quite complex. > > If we can somehow figure out whether there is periodic need for some > traffic (e.g., VoIP), it would also be nice to be able to schedule the > background scans to happen when there is no expected packet being sent > or received at the time. Obviously, this gets much more complex, so this > is not really something that would need to be included in the first > version ;-). Anyway, it would be useful to keep in mind that there may > be needs for making the background scan parameters change dynamically > and there is need to be able to configure a suitable policy from user > space. If someone is picking this up please extend our TODO list for roaming and mention it: http://wireless.kernel.org/en/developers/todo-list#Roaming Luis