<div dir="ltr"><a href="https://sourceforge.net/projects/iperf2/">iperf 2</a> supports one way delay and histograms for UDP packets, TCP writes to reads, and frames. The trick is to synchronize the clocks using something like PTPd2 or PTP4l to a reference, e.g. the GPS atomic clock. One can build a stratum 1 time server with a raspberry pi 4 and a GPS receiver that gives pulse per second. The output supports histograms and mean/min/max/stdev. \The network power metric uses avg throughput over one way delay.<br><br>For internal use we have more granularity than end/end and everything is mapped to the GPS time domain which allows for per message delay analysis as well as system analysis as a function of time.<br><br>We're finding that one way delay is becoming a key performance metric for our WiFi customers and peak throughput less so.<br><br>Bob</div><br><div class="gmail_quote"><div dir="ltr" class="gmail_attr">On Mon, May 17, 2021 at 2:27 PM Matt Mathis <<a href="mailto:mattmathis@google.com">mattmathis@google.com</a>> wrote:<br></div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex"><div dir="ltr">I just got a cool idea: I wonder if it is original....?<div><br><div>Write or adapt a spec based on "A One-way Active Measurement Protocol" (OWAMP - RFC4656), as an application layer LAG metric. Suitably framed OWAMP messages could be injected as close as possible to the socket write in the sending applications, and decoded as close as possible to the receiving application's read, independent of all other protocol details. </div><div><br></div><div>This could expose lag, latency and jitter in a standardized way, that can be reported by the applications and replicated by measurement diagnostics that can be compared apples-to-apples. The default data collection should probably be histograms of one way delays. </div><div><br></div><div>This would expose problematic delays in all parts of the stack, including excess socket buffers, etc.</div><div><br></div><div>This could be adapted to any application protocol that has an appropriate framing layer, including ndt7.<br><div><br></div><div>Thanks,<div><div dir="ltr"><div dir="ltr"><div dir="ltr"><div dir="ltr">--MM--<br>The best way to predict the future is to create it. - Alan Kay<br><br>We must not tolerate intolerance;</div><div dir="ltr"> however our response must be carefully measured: </div><div> too strong would be hypocritical and risks spiraling out of control;</div><div> too weak risks being mistaken for tacit approval.</div></div></div></div></div><br></div></div></div></div><br><div class="gmail_quote"><div dir="ltr" class="gmail_attr">On Mon, May 17, 2021 at 4:14 AM Jonathan Morton <<a href="mailto:chromatix99@gmail.com" target="_blank">chromatix99@gmail.com</a>> wrote:<br></div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex"><div><blockquote type="cite">On 13 May, 2021, at 12:10 am, Michael Richardson <<a href="mailto:mcr@sandelman.ca" target="_blank">mcr@sandelman.ca</a>> wrote:<br><br>But, I'm looking for terminology that I can use with my mother-in-law.<br></blockquote><br><div>Here's a slide I used a while ago, which seems to be relevant here:</div><div><br></div><div><img id="gmail-m_8504732090038545641gmail-m_-502672024805840460082596856-8953-4F2D-B4E0-0D3E5E9C786F" src="cid:1797c1ed86cdb94463a1"></div><div><br></div><div>The important thing about the term "quick" in this context is that throughput capacity can contribute to it in some circumstances, but is mostly irrelevant in others. For small requests, throughput is irrelevant and quickness is a direct result of low latency.</div><div><br></div><div>For a grandmother-friendly analogy, consider what you'd do if you wanted milk for your breakfast cereal, but found the fridge was empty. The ideal solution to this problem would be to walk down the road to the village shop and buy a bottle of milk, then walk back home. That might take about ten minutes - reasonably "quick". It might take twice that long if you have to wait for someone who wants to scratch off a dozen lottery tickets right at the counter while paying by cheque; it's politer for such people to step out of the way.</div><div><br></div><div>My village doesn't have a shop, so that's not an option. But I've seen dairy tankers going along the main road, so I could consider flagging one of them down. Most of them ignore the lunatic trying to do that, and the one that does (five hours later) decides to offload a thousand gallons of milk instead of the pint I actually wanted, to make it worth his while. That made rather a mess of my kitchen and was quite expensive. Dairy tankers are set up for "fast" transport of milk - high throughput, not optimised for latency.</div><div><br></div><div>The non-lunatic alternative would be to get on my bicycle and go to the supermarket in town. That takes about two hours, there and back. It takes me basically the same amount of time to fetch that one bottle of milk as it would to conduct a full shopping trip, and I can't reduce that time at all without upgrading to something faster than a bicycle, or moving house to somewhere closer to town. That's latency for you.</div><div><br></div><div> - Jonathan Morton</div></div>_______________________________________________<br>
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