From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-vx0-f171.google.com (mail-vx0-f171.google.com [209.85.220.171]) (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 11A1E200685 for ; Wed, 4 Jan 2012 09:23:21 -0800 (PST) Received: by vcbfl11 with SMTP id fl11so22532171vcb.16 for ; Wed, 04 Jan 2012 09:23:21 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=gamma; h=sender:message-id:date:from:organization:user-agent:mime-version:to :cc:subject:references:in-reply-to:content-type :content-transfer-encoding; bh=BAgK/B0Y2H2SPCPiKSdE5Omy+1rLYzHN7HwunndtM9g=; b=xpvlT3lhLF3cAgCQ5LjW/6zqj7+ZXDlx+TnmF1rx332Fgp3m92cJJzvlRuann549fs dcCZ8eBMPwwR7ZDsjPIbiaBRjNiUDsiurJ7zPr5JpCGOPDJJiyNn2dSxxwRWd3kZMjGH UeWqE0I594/79Wsuzltkkt+FWW3qdW4St4Yh0= Received: by 10.220.225.70 with SMTP id ir6mr32991930vcb.25.1325697801020; Wed, 04 Jan 2012 09:23:21 -0800 (PST) Received: from [192.168.1.5] (c-24-63-191-17.hsd1.ma.comcast.net. [24.63.191.17]) by mx.google.com with ESMTPS id g6sm23740563vdf.15.2012.01.04.09.23.19 (version=SSLv3 cipher=OTHER); Wed, 04 Jan 2012 09:23:20 -0800 (PST) Sender: Jim Gettys Message-ID: <4F048B06.7090707@freedesktop.org> Date: Wed, 04 Jan 2012 12:23:18 -0500 From: Jim Gettys Organization: Bell Labs User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:8.0) Gecko/20111124 Thunderbird/8.0 MIME-Version: 1.0 To: Dave Taht References: <1325481751.2526.23.camel@edumazet-laptop> <4F046F7B.6030905@freedesktop.org> In-Reply-To: Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Cc: "andrewmcgr@gmail.com" , bloat Subject: Re: [Bloat] What is fairness, anyway? was: Re: finally... winning on wired! X-BeenThere: bloat@lists.bufferbloat.net X-Mailman-Version: 2.1.13 Precedence: list List-Id: General list for discussing Bufferbloat List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Wed, 04 Jan 2012 17:23:22 -0000 On 01/04/2012 11:16 AM, Dave Taht wrote: > > 3) since game manufacturers have noted the diffserv marking in > PFIFO-FAST, what do these queuing disciplines currently do? > They pay no attention to diffserv. It's possible we have a small > problem here, but I'd wager not. That's not what I understand from talking to Andrew McGregor: he says the game companies have figured out that diffserv marking is respected by PFIFO-FAST, and are marking appropriately (since most current routers are doing PFIFO-FAST, as it's been the default in Linux for quite a while. But the flows may be sparse enough it may not matter so much. I think we need to understand this in more depth... > > If their packets are not saturating the link, and/or it's per > host FQ, they are going to win. > > isochronous flows (like voice, even (especially) skype) should respond well to > this stuff, too. do, actually. skype is nicer now. > > > footnotes: > > 1: the 'slower flows gain priority' question is my gravest concern > (eg, ledbat, bittorrent). It's fixable with per-host FQ. > > 2: I note that identifying "a host" is harder than it was in nagle's > day - with multiple protocols in use a hash against an IP address is > not accurate, nor, by the time you hit the egress interface, do you > have a mac address to use. > > I did not solve that problem in my home router gw/aqm/fq prototype. > The approximation was a hash that matched an ip or ipv6 address. > > 3: (and conversely, existing elephants slow down). (and when you drop > packets there is a good question, but you do end up with classic tail > drop behavior in both QFQ and SFQ on a per flow basis. You can get > head drop out of QFQ, actually) > > 4: especially in variable bandwidth scenarios, the depth of even the > fairest queue needs to be managed somehow. > > But I can live with the nearly two orders of magnitude of basic > latency improvement we've got now, as well > as the probability this induces of doing smarter/effective queue > length management, and keep getting the bugs out of it.... > >> > >