From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mout.gmx.net (mout.gmx.net [212.227.17.22]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by lists.bufferbloat.net (Postfix) with ESMTPS id F2BAE3B2A4 for ; Sun, 4 Jun 2023 14:56:14 -0400 (EDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=gmx.de; s=s31663417; t=1685904973; x=1686509773; i=moeller0@gmx.de; bh=Wg9ccMEvq6r7ceNoy3kY8wSS4BYeURNAOjhscW/CqOw=; h=X-UI-Sender-Class:Subject:From:In-Reply-To:Date:Cc:References:To; b=nQmqpn+VEv0pv2cANnyY7FFcfmXFe6fSXG2nRIwu78sswHCsOzOoK7WBK3f8mZMsDPZHMSD a/UQAKqIgHxh5w0dYINkgowfp45XkTpTnH8THEXg9y55UYpKFPduBxcIu2W6/2LNsJJG+fxkn CU7VC0ByHtJkhaEaaj5fCkWMSyymxcYlPQ6ADOiAAS50AQHQXBTXhYU0sE9tPUc5ywYj9XhK4 r18HepVzU4DFlwZduilLegnlYB0Cct5CABhpV9K+hclzhNuiNyU0lAX1iQzXUptzffWCVNBoq fWepSyXp0dmQveUqW/Pu3GSFo7Xm1SbcVoXyvDVwUTFGvYZdTr3w== X-UI-Sender-Class: 724b4f7f-cbec-4199-ad4e-598c01a50d3a Received: from smtpclient.apple ([80.187.108.116]) by mail.gmx.net (mrgmx105 [212.227.17.168]) with ESMTPSA (Nemesis) id 1N7iCg-1qAdx90NRC-014hul; Sun, 04 Jun 2023 20:56:13 +0200 Content-Type: text/plain; charset=utf-8 Mime-Version: 1.0 (Mac OS X Mail 16.0 \(3696.120.41.1.3\)) From: Sebastian Moeller In-Reply-To: Date: Sun, 4 Jun 2023 20:56:12 +0200 Cc: bloat@lists.bufferbloat.net Content-Transfer-Encoding: quoted-printable Message-Id: <724593C4-0427-45EB-A12B-D1C372CFE780@gmx.de> References: <39DED14A-AACF-4C45-9834-C295F92E8800@gmail.com> To: John D X-Mailer: Apple Mail (2.3696.120.41.1.3) X-Provags-ID: V03:K1:v+qaL2SV0wbiNCJTnRryehViqvnk7ylCGiXAsA0z/Vng7JRuk0S HHqIKMMtgbqxRGL3gomq6gVPYjekp/ilFkrMp/SUxcFUQVje6gYn7P807jiu5utmuZ6WQnX EletTbISmxFRh9iu5+zSKfQ61BZIQNtmEYDkh9AfOmKCTxsHJp5HGJrk8uOc96gHFTpMUBS 4VjKrdo5Q13t0zXbtB2lg== X-Spam-Flag: NO UI-OutboundReport: notjunk:1;M01:P0:szAxUrRZNkQ=;Rrh1RejeHnhkKjV5xyv9eBzRJSl MvqI7PaPWa/FUq+EwhRT5B/KhAFxuV21BcaLecQASR44nWgWZyxSpvaZsI1YGykzC0wwbEHKD qb/ebOa2MXi9eqAOCn3vMrZiEubL0XNHpXS93QV404iu0h1/kUcNUC33MNHI3ROvEXerNL6kJ UmIc4BX4QuNMUPXJS1KLN2FccYGx1Cgcy3fbQ6cgRZUrBkIAlFF73hbcUrekrQBO6zYSdzTA6 lXzh3zW8lSEn9CcIEDMJaCN2cPUIl4vVaAuAR+yhdUVuqrNQcb0oHTNv+x9nuQZyZlmLZ9OGL DKNEOWrOBm6yjbwLxefXU36yLAcd32xD0430FZqJyqqmJ22JQUa/s0pXgrYH29HtXb4KOYu3A ydzs9e4Ku4z+F9IAJB37JL1SYBD8tdfTjqxQERF81JpvZeJ8PA7tBeGHKu5MpcSfxGEHlYALv x4ccVmO6BP1glb9pKCBmZRmlk2KdjQcF7hJgO0CrbWVIiTA6l3c3uFaxcEwEZ/aPaaf/MLHg5 jfGCxznuM+brTM/FYaZioItXZ8/sJCyaR17JQGNv2tgca2bumI65KZAr5p+E+bja1a9E0elKf my3ZsoTqKoXOb029Hc56L5q1YZAyrOw7Upx9L+qwqFYpd8cfkPaD3sL/DVX+8lXKmrkjpZoHt rSHkIPI8JJtw6C+bWlRNYWV4yktaYQ3xoiTlqUn6MEcp4W/z2bza+QJsg1nhsM3Yux8yYvOIY rxP3weuSStJ+3aLEjFJUc6gZIbbnOPTu9/xrUl1IrBhjgT0yqnnHrKDhH5mJW5JAGz4vpBObg KCfquxbs7QutAhwJiPiZAHstUoVxVRhwXr3KtDW2g8Q1WGUz1RrIPBW1ew3Lcki/Y/kXfbu7B a1l/Glw7LF+YJxd/94nN/JBtdvmOWTbiQFtVdwTbp3s8Yh4TiVyzuCu8wahijDMkGwlciP6kn 8DN7CT0TthL9ZbzrKf1phUmFbb4= Subject: Re: [Bloat] SQM tuning question 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: Sun, 04 Jun 2023 18:56:15 -0000 Hi John, > On Jun 3, 2023, at 19:17, John D via Bloat = wrote: >=20 > Thanks for the detail. It makes sense but it kind of feels like in = some (maybe many) cases the router could know the internet link = performance. Sometimes they do, sometimes they do not, and sometimes the = number the router might now is well above the contractual limit, e.g. my = ISP for some time configured my VDSL2 link to sync at ~100/40 Mbps and = restrict my capacity at an upstream device (BNG) to my contracted ~50/10 = Mbps, so knowing the link speed will only give you an upper bound for = some link technologies. > Particularly home router-modems often monitor this already. Maybe = that's just not exposed in any standardised way? Yes and no, all the link technologies I looked at = (DSL/DOCSIS/PON) have some channel between the ISP side equipment = (DSLAM/CMTS/OLT) and the equipment on the user side (CPE: = DSL-/cable-/pon-modem) by which the ISP gear can query information from = the CPE; but these three seem to be using three different approaches, = and more importantly, just because the head-end can query these, does = not mean that devices in the home network can do so as well... Plus, as mentioned above, the reported "sync" capacity might not = be the capacity required to configure sqm's traffic shaper. > I'm guessing if I was into openwrt I could maybe do something, but I = prefer just to find something off the shelf with half decent SQM... If = "auto configuration" isn't a feature then that answers my question and I = can get on choosing the best option. There are the work-in-progress *-autorate approaches mentioned = in my earlier post... Kind Regards Sebastian >=20 > On Sat, Jun 3, 2023, 16:44 Jonathan Morton = wrote: > > On 3 Jun, 2023, at 4:56 pm, John D via Bloat = wrote: > >=20 > > On the website it says the following: > >=20 > > CoDel is a novel =E2=80=9Cno knobs=E2=80=9D, =E2=80=9Cjust works=E2=80= =9D, =E2=80=9Chandles variable bandwidth and RTT=E2=80=9D, and simple = AQM algorithm. > >=20 > > =E2=80=A2 It is parameterless =E2=80=94 no knobs are required = for operators, users, or implementers to adjust. > > =E2=80=A2 It treats good queue and bad queue differently - = that is, it keeps the delays low while permitting bursts of traffic. > > =E2=80=A2 It controls delay, while insensitive to round-trip = delays, link rates, and traffic loads. > > =E2=80=A2 It adapts to dynamically changing link rates with no = negative impact on utilization. > >=20 > > But everywhere I have read about about hardware which implements SQM = (including the bufferbloat website) it describes the need to tune based = on actual internet connection speed. > > These seem to conflict especially that "handles variable bandwidth" = bit. Have I misunderstood or do the algorithms used in modern hardware = just not provide this part typically? My connection performance is quite = variable and I'm worried about crippling SQM to the lowest speed seen. >=20 > SQM in practice requires three components: >=20 > 1: Flow isolation, so that different flows don't affect each others' = latency and are delivered fairly; >=20 > 2: Active Queue Management (AQM) to signal flows to slow down = transmissions when link capacity is exceeded; >=20 > 3: Bandwidth shaping to match the queue to the available capacity. >=20 > CoDel is, in itself, only the AQM component. It does indeed work = pretty well with no additional tuning - but only in combination with the = other two components, or when applied directly to the actual bottleneck. = Unfortunately in most consumer internet links, the actual bottleneck is = inaccessible for this purpose. Thus an artificial bottleneck must be = introduced, at which SQM is applied. >=20 > The most convenient tool for applying all three SQM components at once = is Cake. This includes implementations of advanced flow isolation, = CoDel AQM, and a deficit-mode bandwidth shaper. All you really need to = do is to tell it how much bandwidth you have in each direction, minus a = small margin to ensure it becomes the actual bottleneck and can exert = the necessary control. >=20 > When your available bandwidth varies over time, that can be = inconvenient. There are methods, however, of observing how available = capacity tends to change over time (typically on diurnal and weekly = patterns, if the variations are due to congestion in the ISP backhaul or = peering) and scheduling adjustments on that basis. If you have more = information on your situation, we might be able to give more detailed = advice. >=20 > - Jonathan Morton > _______________________________________________ > Bloat mailing list > Bloat@lists.bufferbloat.net > https://lists.bufferbloat.net/listinfo/bloat