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[37.136.219.147]) by smtp.gmail.com with ESMTPSA id z1sm1333062lfh.137.2021.07.06.01.48.32 (version=TLS1_2 cipher=ECDHE-ECDSA-AES128-GCM-SHA256 bits=128/128); Tue, 06 Jul 2021 01:48:32 -0700 (PDT) Content-Type: text/plain; charset=us-ascii Mime-Version: 1.0 (Mac OS X Mail 11.5 \(3445.9.7\)) From: Jonathan Morton In-Reply-To: Date: Tue, 6 Jul 2021 11:48:31 +0300 Cc: Stuart Cheshire , Christoph Paasch , bloat Content-Transfer-Encoding: quoted-printable Message-Id: <5C8DA517-01DE-477F-9B3D-952D953EEC89@gmail.com> References: To: Matt Mathis X-Mailer: Apple Mail (2.3445.9.7) Subject: Re: [Bloat] Credit and/or collaboration on a responsiveness metric? 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: Tue, 06 Jul 2021 08:48:35 -0000 > On 6 Jul, 2021, at 2:21 am, Matt Mathis wrote: >=20 > The rounds based responsiveness metric is awesome! There are several = slightly different versions, with slightly different properties.... >=20 > I would like to write a little paper (probably for the IAB workshop), = but don't want to short change anybody else's credit, or worse, scoop = somebody else's work in progress. I don't really know if I am = retracing somebody else's steps, or on a parallel but different path = (more likely). I would be really sad to publish something and then = find out later that I trashed some PhD students' thesis.... It's possible that I had some small influence in originating it, = although Dave did most of the corporate marketing. My idea was simply to express delays and latencies as a frequency, in = Hz, so that "bigger numbers are better", rather than always in = milliseconds, where "smaller numbers are better". The advantage of Hz = is that you can directly compare it to framerates of video or gameplay. Conversely, an advantage of "rounds per minute" is that you don't need = to deal with fractions or rounding for relatively modest and common = levels of bloat, where latencies of 1-5 seconds are typical. I'm not overly concerned with taking credit for it, though. It's a = reasonably obvious idea to anyone who takes a genuine interest in this = field, and other people did most of the hard work. > Please let me know if you know of anybody else working in this space, = of any publications that might be in progress or if people might be = interested in another collaborator. There are two distinct types of latency that RPM can be used to measure, = and I have written a short Internet Draft describing the distinction: = https://www.ietf.org/archive/id/draft-morton-tsvwg-interflow-intraflow-del= ays-00.html Briefly, "inter-flow delays" (or BFID) are what you measure with an = independent latency-measuring flow, and "intra-flow delays" (or WFID) = are what you measure by inserting latency probes into an existing flow = (whether at the protocol level with HTTP2, or by extracting it from = existing application activity). The two typically differ when the path = bottleneck has a flow-isolating queue, or when the application flow = experiences loss and retransmission recovery. I think both measures are important in different contexts. An = individual application may be concerned with its own intra-flow delay, = as that determines how quickly it can respond to changes in network = conditions or user intent. Network engineers should be concerned with = inter-flow delays, as those determine what effect a bulk application = load has on other, more latency-sensitive applications. The two are = also optimally controlled by different mechanisms - FQ versus AQM - = which is why the combination of the two is so powerful. Feel free to use material from the above with appropriate attribution. - Jonathan Morton=