Return-path: Received: from smtp.nokia.com ([131.228.20.173]:20467 "EHLO mgw-ext14.nokia.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1757442AbXKLLOq (ORCPT ); Mon, 12 Nov 2007 06:14:46 -0500 To: Jouni Malinen Cc: Johannes Berg , Michael Buesch , linux-wireless , Ben Greear , Michael Wu , Jiri Benc Subject: Re: [RFC] b43: multiple MAC addresses support References: <1194572631.4793.64.camel@johannes.berg> <1194605550.4793.93.camel@johannes.berg> <20071111025808.GK4031@jm.kir.nu> From: Kalle Valo Date: Mon, 12 Nov 2007 13:14:11 +0200 In-Reply-To: <20071111025808.GK4031@jm.kir.nu> (ext Jouni Malinen's message of "Sat\, 10 Nov 2007 18\:58\:08 -0800") Message-ID: <87pryfd8cc.fsf@nokia.com> (sfid-20071112_111451_046579_6848E9DE) MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Sender: linux-wireless-owner@vger.kernel.org List-ID: Jouni Malinen writes: > On Fri, Nov 09, 2007 at 11:52:30AM +0100, Johannes Berg wrote: > >> Something I'm not clear on right now is the timing of it all. If there >> are say two BSSes, the driver can simply program the hardware to half >> the beacon period and then the beacons will alternate. But if there are >> seven BSSes, the beacon period might not be divisible by seven so timing >> errors will happen and, worse yet, accumulate. Does hostapd somehow >> account for this? Or should the beaconing work completely differently, >> for example with all N beacons sent in a burst? > > You could always modify the beacon period to a suitable number that > would be divisible by whatever number of BSSes there are and/or add > empty slot to move from, say, 7 to 8, and just not send a beacon at some > of the slots. Sending a burst of all beacons at the same time is also a > valid option up to a certain limit on how long a time would be allocated > for this. However, this may have some timing issues when there are > multiple power save buffered broadcast/multicast frames waiting to be > sent out. In general, it would be good to try to send the beacon frames > as close to their correct time as possible to allow power saving > stations to remain asleep most of the time. Exactly, it is important for small mobile devices that beacons are sent at the correct time. For example, I have seen broken APs which Target Beacon Transmission Time fluctuates and Nokia N800 has high power consumption because of that. -- Kalle Valo