From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-iy0-f171.google.com (mail-iy0-f171.google.com [209.85.210.171]) (using TLSv1 with cipher RC4-SHA (128/128 bits)) (Client CN "smtp.gmail.com", Issuer "Google Internet Authority" (verified OK)) by huchra.bufferbloat.net (Postfix) with ESMTPS id 3D463200B10; Thu, 8 Dec 2011 00:20:50 -0800 (PST) Received: by iaen33 with SMTP id n33so3565998iae.16 for ; Thu, 08 Dec 2011 00:20:49 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=gamma; h=mime-version:date:message-id:subject:from:to:content-type :content-transfer-encoding; bh=FGBm9iUict+Wc5U2eKiQPqKqy4INsPj3Iv5rkee82AQ=; b=NJBs/j/NbMM+59HQNpAN7DFZqYLHzvGccDhYWULR5aFwkH/2xRA6RYJuZ4Fk/Aq2ta VrZYR8T+MW1Ndd+sXivet4Lnq8iGPiKuvD5ei1W7KuCTlTPsGcxHmsfAsI8+SbH6akty PhAym1aPhFacB1U97+sjCi0Pi28sZ0LfEOFH4= MIME-Version: 1.0 Received: by 10.231.20.227 with SMTP id g35mr503777ibb.32.1323332449456; Thu, 08 Dec 2011 00:20:49 -0800 (PST) Received: by 10.231.204.83 with HTTP; Thu, 8 Dec 2011 00:20:49 -0800 (PST) Date: Thu, 8 Dec 2011 09:20:49 +0100 Message-ID: From: Dave Taht To: cerowrt-devel@lists.bufferbloat.net, cerowrt@lists.bufferbloat.net Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: quoted-printable Subject: [Cerowrt-devel] Coping with wireless-n [#305] X-BeenThere: cerowrt-devel@lists.bufferbloat.net X-Mailman-Version: 2.1.13 Precedence: list List-Id: Development issues regarding the cerowrt test router project List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Thu, 08 Dec 2011 08:20:50 -0000 This is the 6th in a series of mails doing a post-mortem and rethink of what is in cerowrt. Basically I think the 2.4ghz spectrum is beyond hope. Everywhere I've been there are dozens of radios all on all the channels available, all competing, all interfering, and the difference in performance results I get minute to minute, hour to hour varies so wildly that in order to get a good picture of how basic 2.4ghz performance worked I had to go to remote valley in france where there was no competing signals to deal with. There I got pretty equivalent results between 2.4ghz and 5. The rest of the time, not so much. As for wireless-g vs n, the current architecture of the mac80211 stack buries packet aggregation so deeply within it that the two technologies are very incompatible. It also bothers me that management frames are buried so deeply, too. The only places I've been this year that had a functional wireless network, rigorously divided up the SSIDs into g, n, ipv4 and ipv6 specific parts, and were using Cisco hardware. I don't see the need to have separate SSIDs for 4 and 6, but I think g+QFQ, and n+SFQ might do better in the general case on an AP. QFQ would work well on client machines, particularly with n, to break up packet bursts more sanely into multiple streams. SFQ, less so. I'd rather pursue QFQ on the clients as it better 'shreds' competing bursts. I'd like others to play with it too. and in all cases getting to where something BQL-like + Time in Queue on top of those two techniques will help most of all, but better feedback loops and means of determining bandwidth differences between destinations are kind of required. And doing MUCH better classification into the hardware queues would be good, too. So in the next release of cerowrt I'm planning on having a separate n-only or g-only SSID available on the 5ghz channel, and to experiment with the above qdiscs. I sort of have some major ANT and DSCP specific classifier code that I plan to polish up. as for BQL and Time in Queue, that work is only just beginning and I hope to track it closely. As to how to make it apply to wireless, I look forward to the engineering debate(s). It's a ton of work. --=20 Dave T=E4ht SKYPE: davetaht US Tel: 1-239-829-5608 FR Tel: 0638645374 http://www.bufferbloat.net