From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-gg0-f171.google.com (mail-gg0-f171.google.com [209.85.161.171]) (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 BD9ED2012AC; Wed, 9 May 2012 14:47:46 -0700 (PDT) Received: by ggki1 with SMTP id i1so996080ggk.16 for ; Wed, 09 May 2012 14:47:45 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20120113; h=sender:message-id:date:from:organization:user-agent:mime-version:to :cc:subject:references:in-reply-to:content-type :content-transfer-encoding; bh=tErgo7zK8RKyaJVrfYQPmmSCm6WT/kzvhg/cX8rumVQ=; b=YI5vXDaymGoA7A7dsYVpDFU5FPrDFgcfi/dO38Mx0r6pt4dchHuK16NA6/CnQx5Y4e 40ufduslFvvstr5AEEAZP3NQp5LCO3SGlWHJX4byugTh+5mM0+BEai3o8g2YHRgOnnsl hC9p6ZpTj4jGGQw7flxsNgpYLPYRfFNL0EktTXF1gKpOlBJNIjwixXhGuuu34HRpftAO l6TjG7catVA7dHxE9H3WADsIaeoDcCrsoJ5T9Zd6kA1btWEEPt/ZwfFt+KTVcz5Awh5T f+KrMuhXPAVH0OrrrBuqYg9hd+tWI7KI8i1OntnasSyITvRGgaRBoXkALezn68eJCkWa piFg== Received: by 10.236.124.73 with SMTP id w49mr2235487yhh.31.1336600065722; Wed, 09 May 2012 14:47:45 -0700 (PDT) Received: from [192.168.1.81] (c-50-138-162-108.hsd1.ma.comcast.net. [50.138.162.108]) by mx.google.com with ESMTPS id l13sm6369222ann.2.2012.05.09.14.47.30 (version=SSLv3 cipher=OTHER); Wed, 09 May 2012 14:47:31 -0700 (PDT) Sender: Jim Gettys Message-ID: <4FAAE5F0.2030404@freedesktop.org> Date: Wed, 09 May 2012 17:47:28 -0400 From: Jim Gettys Organization: Bell Labs User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:12.0) Gecko/20120430 Thunderbird/12.0.1 MIME-Version: 1.0 To: Fred Baker References: <4FA9FDC0.9010600@superduper.net> <44673AC5-4320-4C19-9788-87A63C47549D@cisco.com> In-Reply-To: <44673AC5-4320-4C19-9788-87A63C47549D@cisco.com> Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Cc: codel@lists.bufferbloat.net, bloat Subject: Re: [Codel] [Bloat] The challenge X-BeenThere: codel@lists.bufferbloat.net X-Mailman-Version: 2.1.13 Precedence: list List-Id: CoDel AQM discussions List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Wed, 09 May 2012 21:47:47 -0000 On 05/09/2012 04:06 PM, Fred Baker wrote: > On May 9, 2012, at 12:16 AM, Simon Barber wrote: > >> One question now remains - will codel AQM be sufficient on it's own in getting delays down to levels that users are happy with for the common latency sensitive interactive traffic - VoIP, gaming and Skype for example - or are the further reductions that can be had with traffic classification and smart queuing algorithms necessary? > In my opinion, AQM is enough to get traffic into the "reasonable" range, but if you're looking for a specific SLA that might be applicable to gaming etc, you will need to do some engineering in terms of diffserv etc. > _______________________________________________ > I used to think that, before I understood: 1) what the web was doing (again), by ignoring the 2 old TCP connection rule, crossed by web site "sharding". This is why I wrote the IW10 considered Evil draft last fall. 2) what the NIC offload engines were doing to generate line rate packet trains and injecting them into the net, where they can land "spat" at the customer end. 3) Ledbat won't help once an effective AQM is in place; the delay it's keying off of goes away, and then it competes like Reno with regular flows. 100 BitTorrent flows competing with your traffic can ruin your entire day. We get to revisit this topic. 4) a busy 802.11 net (or using one where the range to the AP drops the bandwidth to low rate) means even single big packets has 12 milliseconds of latency @ 1Mbps (even ignoring other 802.11 effects, just the bit transfer time). Even on high speed (50Mbps broadband) I see transients of > 100ms just browsing image heavy web sites. So while CoDel will help (a lot, particularly policing TCP so that it will respond quickly rather than suffering the quadratic responsiveness problem), I now firmly believe we have to probably delve into "fair" queuing and classification if we want a low latency edge to the Internet. This doesn't mean I believe we'll have to do all this beyond the broadband edge box (e.g. CMTS/DSLAM/FIOS) ; but I think these and the home network have to actually be careful. thankfully, at the edge, you have way more cycles/packet you can *afford* to use on such schemes. Having an AQM that actually works well enough to be "on" by default will help most of the other instances of bloat I know of elsewhere, but the edge, it's a different story.... - Jim