Return-path: Received: from mx1.redhat.com ([66.187.233.31]:33200 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752209AbYHMMrn (ORCPT ); Wed, 13 Aug 2008 08:47:43 -0400 Subject: Re: Pondering: how to improve mac80211 roaming ... From: Dan Williams To: Helmut Schaa Cc: Jouni Malinen , Holger Schurig , linux-wireless@vger.kernel.org In-Reply-To: <200808131426.55673.hschaa@suse.de> References: <200808120838.52888.hs4233@mail.mn-solutions.de> <200808121440.24098.hschaa@suse.de> <20080812154223.GE4981@jm.kir.nu> <200808131426.55673.hschaa@suse.de> Content-Type: text/plain Date: Wed, 13 Aug 2008 08:49:15 -0400 Message-Id: <1218631755.29370.1.camel@localhost.localdomain> (sfid-20080813_144747_329541_26E1DE39) Mime-Version: 1.0 Sender: linux-wireless-owner@vger.kernel.org List-ID: On Wed, 2008-08-13 at 14:26 +0200, Helmut Schaa wrote: > Am Dienstag, 12. August 2008 17:42:23 schrieb Jouni Malinen: > > 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. > > Good point. > > > 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. > > It might even be beneficial to cancel a currently active background scan once > the TX queue is filling up and report the already gathered information to the > user space. If that's the case, we should also then have a response to the original scan request (or broadcast netlink message with the original request's cookie) that says "scan canceled" so that the requester can handle that. dan