From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-wr1-x436.google.com (mail-wr1-x436.google.com [IPv6:2a00:1450:4864:20::436]) (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 3F5043B29E; Mon, 13 Mar 2023 12:04:15 -0400 (EDT) Received: by mail-wr1-x436.google.com with SMTP id i9so2811403wrp.3; Mon, 13 Mar 2023 09:04:15 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20210112; t=1678723454; h=content-transfer-encoding:cc:to:subject:message-id:date:from :in-reply-to:references:mime-version:from:to:cc:subject:date :message-id:reply-to; bh=vZ40HiouRrAakLvy7WH3uzjWOvHAdvSNeLXmmxBZDIs=; b=Mx4vmF+WWgzPeBtcVMvvZh697ZdNUCjl2rLa6ra7S4E+gOceLq6hjmuV+a5YsEI1a9 ao5oX4B4x+rjKp5QDbwv+fsxdxCXNkUh7ZFGHTBkPvOhLLXtlAm9PbOKai9hAOkVXVbO uWhK2GGP4zX9NiR87hxasPkfHPUfnpwqA9m6WNaOtOJ40lj2qCbNaJuB5cpb+cANj4fL U6dBGZ2vcz5JzqkRBpLVJqDSMPNnAgnnAEBl8fmWPWRO3WAAfJWsz0Ts9Can4A0OCIT+ IsO5mI0zHnjiJBPr3W3UcQoV5Q3NXH5YJhZ+PgTM3aYM6N++l7pt5moZ6y/aeCkc3zbB EFgQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; t=1678723454; h=content-transfer-encoding:cc:to:subject:message-id:date:from :in-reply-to:references:mime-version:x-gm-message-state:from:to:cc :subject:date:message-id:reply-to; bh=vZ40HiouRrAakLvy7WH3uzjWOvHAdvSNeLXmmxBZDIs=; b=I1GFvkFXXbEUzONsvQEvsYB64gjgIwZ84Zc9wuk5ZNZP4N48vsY/MZbqCcQ0h0ItKN +481FY/w//93SEQ2guy8cPmBKmoRtCAEHWoxso+0g0GvGh6nGg4G6sO5wvh7z+U4qLaq cBun2NGrY4aovW/9PIReZB2j2h81dbOfvgSLBSEgXuy3V6Xz0PjMFLkXKi2e+exNvCT/ 5WDP0EBWAOJy5OUx9D9aH3j+psJoJdm/CE4FFCVK31yH8BILhceQ6Ga0egcIhX3COPfY iu3MNWDQ/V7wMmUJSzTy/l+643urn0KenMDneSU2jxQf/kpxOhOD9Ojpe+gv0cqYw4q5 n3UA== X-Gm-Message-State: AO0yUKXCp6kG49IAySe7ih89jHSX2yTQ789Ls5PeUTZGIi1CcTfR1/NF eEOXlO96uqLPlNJOsY7U0foSosbfZu/a5IE7beU= X-Google-Smtp-Source: AK7set/Yq1kM4uEaNEeqNJ0Cu92LlnuEn7YqJReMZaRbFPC4Iq/WtbR0bkto8uqEmslDmIUvM175iqjJSnkyyqXs0t0= X-Received: by 2002:a5d:4347:0:b0:2c7:1ce2:6c77 with SMTP id u7-20020a5d4347000000b002c71ce26c77mr7249253wrr.13.1678723453885; Mon, 13 Mar 2023 09:04:13 -0700 (PDT) MIME-Version: 1.0 References: <1672786712.106922180@apps.rackspace.com> <77CCAD19-07E0-4F9E-88C1-D207CF7BF376@cable.comcast.com> <83ffc0dad19e3343e49271889369cefc@rjmcmahon.com> In-Reply-To: From: Dave Taht Date: Mon, 13 Mar 2023 09:04:01 -0700 Message-ID: To: Jeremy Austin Cc: Sebastian Moeller , Dave Taht via Starlink , dan , libreqos , Rpm , bloat Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable Subject: [Rpm] UnderBloat on fiber and wisps X-BeenThere: rpm@lists.bufferbloat.net X-Mailman-Version: 2.1.20 Precedence: list List-Id: revolutions per minute - a new metric for measuring responsiveness List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Mon, 13 Mar 2023 16:04:15 -0000 On Mon, Mar 13, 2023 at 8:08=E2=80=AFAM Jeremy Austin via Rpm wrote: > > > > On Mon, Mar 13, 2023 at 3:02=E2=80=AFAM Sebastian Moeller via Starlink wrote: >> >> Hi Dan, >> >> >> > On Jan 9, 2023, at 20:56, dan via Rpm wrot= e: >> > >> > You don't need to generate the traffic on a link to measure how >> > much traffic a link can handle. >> >> [SM] OK, I will bite, how do you measure achievable throughput w= ithout actually generating it? Packet-pair techniques are notoriously impre= cise and have funny failure modes. > > > I am also looking forward to the full answer to this question. While one = can infer when a link is saturated by mapping network topology onto latency= sampling, it can have on the order of 30% error, given that there are mult= iple causes of increased latency beyond proximal congestion. > > A question I commonly ask network engineers or academics is "How can I ac= curately distinguish a constraint in supply from a reduction in demand?" This is an insanely good point. In looking over the wisp configurations I have to date, many are using SFQ which has a default packet limit of 128 packets. Many are using SFQ with a *even shorter* packet limit, which looks good on speedtests which open many flows (keown's sqrt(flows) for bdp), but is *lousy* for allowing a single flow to achieve full rate (the more common case for end-user QoE). I have in general tried to get mikrotik folk at least, to switch away from fifos, red, and sfq to wards fq_codel or cake at the defaults (good to 10Gbit) in part, due to this. I think SFQ 128 really starts tapping out on most networks at around the 200Mbit level, and above 400, really, really does not have enough queue, so the net result is that wisps attempting to provide higher levels of service are not actually providing it in the real world, an accidental constraint in supply. I have a blog piece, long in draft, called "underbloat", talking to this. Also I have no seen multiple fiber installs that had had a reasonable 50ms FIFO buffer for 100Mbit, but when upgraded to 1gbit, left it at 5ms, which has bad sideffects for all traffic. To me it looks also that at least some ubnt radios are FQd and underbuffere= d. > -- > -- > Jeremy Austin > Sr. Product Manager > Preseem | Aterlo Networks > preseem.com > > Book a Call: https://app.hubspot.com/meetings/jeremy548 > Phone: 1-833-733-7336 x718 > Email: jeremy@preseem.com > > Stay Connected with Newsletters & More: https://preseem.com/stay-connecte= d/ > _______________________________________________ > Rpm mailing list > Rpm@lists.bufferbloat.net > https://lists.bufferbloat.net/listinfo/rpm --=20 Come Heckle Mar 6-9 at: https://www.understandinglatency.com/ Dave T=C3=A4ht CEO, TekLibre, LLC