From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-lj1-x22c.google.com (mail-lj1-x22c.google.com [IPv6:2a00:1450:4864:20::22c]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by lists.bufferbloat.net (Postfix) with ESMTPS id BEC903B2A4 for ; Mon, 24 May 2021 10:30:39 -0400 (EDT) Received: by mail-lj1-x22c.google.com with SMTP id e11so33808464ljn.13 for ; Mon, 24 May 2021 07:30:39 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=mime-version:subject:from:in-reply-to:date:cc :content-transfer-encoding:message-id:references:to; bh=p+GdsmPBp2d82lLNheriMM7ogY2PSQePjnCEGFx1lN4=; b=HDNyYdL8VYSbBjA5itsYNekPuO2wD1l8lWZnTP+vTWXuZY1iG3Gt604gpWJ5o+Ii6M Q68rTZEjetXhisroCgNI8uEUriOE/PGdrnnR+v3aFvQqPXFadkZTe8dDaMvVEoTCmBli o4VlnLVy2LRoVjxpIhvRNkR7n8imnoYj6AkBmBu+zHRvwNpWkVH5FwDIi51pGq4FHQbR d42QcmtdoaKjESFn+/+agDxlsiN+GgjJaQTUfgjIw0EXVcNqVf1g4lB76WEqOoBhQF0m ATsPgxkPbX9hF5sP6rrXhViwZHpJ7huX/NkpJ0LgJ0sMoxqWDD24r5JC9qIeMyzwN5FT fA0g== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:subject:from:in-reply-to:date:cc :content-transfer-encoding:message-id:references:to; bh=p+GdsmPBp2d82lLNheriMM7ogY2PSQePjnCEGFx1lN4=; b=UlcPd2mwLjI1xDJrb6Lf/8LTD5EzW+fcPui4ubcJdFQUem2pctCf+YHztD2A3Rm/Gb 1mcMCnsB7WMjX2LzOkA2AXgqw7t6YcHXHaAJLGfeZvkSho2G6gHoKzXLTkXumoU5KcUT DR2SnBmdoyjBAhpST8UpLN3NiBxt9Gv+GKgqqUcdjSMVnR7K6prS+57PZIjpSSip8+Jb xu6hF/BlX0whP7We1m3XLkbZ3exu5M8Z9Ksq+Hhp9pL4dP+uuWckLEnzSk7RDLT29U7u 3xaJETLjVIit+gz90B7hs/lA9XxfE08s56AJpC50utRakHJiHhjz9n91OWUI8lG62kw1 nbwA== X-Gm-Message-State: AOAM5318Zam5TTRYu93FEu3zeeLmLK3fsP6OUY8nxHF+KDLHAg5fHmCP fyhcUrr5pZMVfvHW8Q1aurU= X-Google-Smtp-Source: ABdhPJwUlKLdE/Gf4VXMtamTOGxa7mcZsg/2DS8l2/yKWpXLr5q4pFadSpRjet3m0OhnwbYg4CX3Ag== X-Received: by 2002:a2e:9f44:: with SMTP id v4mr17567123ljk.475.1621866638402; Mon, 24 May 2021 07:30:38 -0700 (PDT) Received: from jonathartonsmbp.lan (37-136-237-77.rev.dnainternet.fi. [37.136.237.77]) by smtp.gmail.com with ESMTPSA id 131sm1355935lfm.73.2021.05.24.07.30.37 (version=TLS1_2 cipher=ECDHE-ECDSA-AES128-GCM-SHA256 bits=128/128); Mon, 24 May 2021 07:30:37 -0700 (PDT) Content-Type: text/plain; charset=utf-8 Mime-Version: 1.0 (Mac OS X Mail 11.5 \(3445.9.7\)) From: Jonathan Morton In-Reply-To: <8CA408F6-C8FA-4AAF-908A-B52BDC5030FF@cable.comcast.com> Date: Mon, 24 May 2021 17:30:36 +0300 Cc: "bloat@lists.bufferbloat.net" Content-Transfer-Encoding: quoted-printable Message-Id: <9CDBF19A-C131-4497-9456-285343F93787@gmail.com> References: <8CA408F6-C8FA-4AAF-908A-B52BDC5030FF@cable.comcast.com> To: "Livingood, Jason" X-Mailer: Apple Mail (2.3445.9.7) Subject: Re: [Bloat] AQM & Net Neutrality X-BeenThere: bloat@lists.bufferbloat.net X-Mailman-Version: 2.1.20 Precedence: list List-Id: General list for discussing Bufferbloat List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Mon, 24 May 2021 14:30:40 -0000 > On 24 May, 2021, at 4:09 pm, Livingood, Jason via Bloat = wrote: >=20 > I=E2=80=99m looking for opinions here re bloat-busting techniques like = AQM in the context of network neutrality (NN). The worry I have is = whether some non-technical people will misunderstand how AQM works & = conclude that implementing it may violate NN because it would make = interactive traffic perform better than it does today. That is true of = course =E2=80=93 it=E2=80=99s a design goal of AQM, but non-interactive = traffic performs as well as it always has =E2=80=93 it is not = disadvantaged. > =20 > Maybe the worries I have heard just points out the need for more = education/awareness about what delay is and why things like AQM are not = prioritization/QoS? I appreciate any thoughts. I'm pleased to help with education in this area. The short and = simplistic answer would be that AQM treats all traffic going through it = equally; the non-interactive traffic *also* sees a reduction in latency; = though many people won't viscerally notice this, they can observe it if = they look closely. More importantly, it's not necessary for traffic to = make any sort of business or authentication arrangement in order to = benefit from AQM, only comply with existing, well-established = specifications as they already do. If the traffic supports ECN, the AQM can use that instead of packet = drops for signalling, which tends to actually *reduce* packet loss in = bulk transfers, compared to simply bouncing off the tail end of a dumb = FIFO. Reduced latency would already make recovering from these losses = easier for the transport, but eliminating them entirely means that the = application receives a completely smooth delivery, with no sudden pauses = and jumps caused by the recovery process. It's worth digging into the details a bit to solidify the message for a = broader range of audiences. You might start with my recently published = Informational draft discussing different types of latency: = https://datatracker.ietf.org/doc/html/draft-morton-tsvwg-interflow-intrafl= ow-delays-00 I'll note in passing that AQM can be used as part of a system that = would, in fact, violate Net Neutrality. It's important to distinguish = the effects caused by different parts of the system, so that a = Net-Neutral system can be obtained by deleting just the parts that are = incompatible with it. Current indications, for example, are that L4S = would fall under that definition, since it gives a strong throughput = priority to traffic carrying its identifier. Without an AQM or FQ system at the bottleneck, interactive traffic is at = the mercy of any competing traffic as to how much delay it will suffer = in the queue. Non-interactive traffic seeks to keep that queue full in = order to maximise throughput, with latency being considered unimportant. = If the queue size is chosen carefully, the damage can be limited to = some extent, but there is a limit to how much a buffer can be shrunk = before it starts reducing throughput as well. In short, it is not = possible to treat both types of traffic equally well with a dumb FIFO; = you must favour one or the other, and historically it was = throughput-sensitive applications that won that debate. I think there = is a little bit more awareness of right-sizing buffers these days, but = that can still easily lead to hundreds of milliseconds of unnecessary = delay to interactive traffic, which is difficult to tolerate. By contrast, when you implement both AQM and FQ at the bottleneck, = interactive traffic is no longer affected by competing traffic at all, = as long as they use less than their "fair share" of available throughput = capacity. When that threshold is exceeded, the AQM will start working = to inform them that they're sending too fast, and the FQ will regulate = the flow so that it *is* a fair share that it consumes. This "fair = share" metric has a number of different reasonable definitions, but it = should not be confused with a so-called "fair usage policy"; it only = kicks in when all the capacity on the link is already in use. You can also implement *just* AQM at the bottleneck. In this case the = benefit seen by interactive traffic is somewhat diluted, because all = traffic goes through the same queue in FIFO order. The AQM simply tells = traffic to slow down if the queue shows signs of filling up. This = leaves the queue still able to handle bursts of traffic (which are the = main concern for throughput), while minimising the delay since the queue = does not sit constantly full. An "Approximate Fairness" AQM also = dynamically steers AQM signalling towards traffic that contributes the = most to congestion, leaving lighter and interactive traffic alone. Alternatively, you could implement *just* FQ, although this is usually = seen as the more difficult component of the two to implement at high = speed and/or large scale. This would simply hold bulk traffic to its = "fair share", and keep it out of the way of interactive traffic, without = also reducing the delay to the bulk traffic flows. I would suggest that = if you implement FQ, you can also usually implement AQM on top with = little difficulty. Please do ask for further clarification if that would be helpful. - Jonathan Morton=