From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mout.gmx.net (mout.gmx.net [212.227.15.15]) (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 2AE533CB37 for ; Mon, 10 Apr 2023 07:30:17 -0400 (EDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=gmx.de; s=s31663417; t=1681126211; i=moeller0@gmx.de; bh=g+9/zXUV1m9MuHYwKkQEJpM1wqLE/qx+hWl79dAE9jc=; h=X-UI-Sender-Class:Subject:From:In-Reply-To:Date:Cc:References:To; b=XCBuJtl0CgEHtPlLcU7cocdqqdGRt+sLDqr9cWOyTbQUcZ/5LhRNGXSzP8Wh2xNO/ XwwuwO7XPeDPNoilsc0gizqollr2Y6ReH2UyZaMltcI7fHY7xtFQGE8ROhCp50vlA1 9146SDkYf7roEw/ryZ6UlvyXogx+mJ7e7ViJFIo6FH1MA9wNP0laTNOUEprVNM7Ez1 U74UD//FtxHlAhSaB6KCTnVhMgnEijMPDw89qw6pZ5SkL+LL420TE2olqu6UFGPQSt APTsnq1f1N2cE/unNfYczqc9nYEHW8YTSC77rPjH6gkeA8pCA7D5Ldl1m588etIgGs uyDlS2HNNSZtQ== X-UI-Sender-Class: 724b4f7f-cbec-4199-ad4e-598c01a50d3a Received: from smtpclient.apple ([77.0.150.154]) by mail.gmx.net (mrgmx004 [212.227.17.190]) with ESMTPSA (Nemesis) id 1MNbp3-1q0KJE1txz-00P53C; Mon, 10 Apr 2023 13:30:11 +0200 Content-Type: text/plain; charset=us-ascii Mime-Version: 1.0 (Mac OS X Mail 16.0 \(3696.120.41.1.2\)) From: Sebastian Moeller In-Reply-To: <7r2s1po9-5593-0r22-5743-p39544o72716@ynat.uz> Date: Mon, 10 Apr 2023 13:30:09 +0200 Cc: Dave Collier-Brown , bloat@lists.bufferbloat.net Content-Transfer-Encoding: quoted-printable Message-Id: References: <11761.1680979748@localhost> <26343.1681007539@localhost> <84213209-f77e-b59b-4a37-bf54e46e3ddc@indexexchange.com> <7r2s1po9-5593-0r22-5743-p39544o72716@ynat.uz> To: David Lang X-Mailer: Apple Mail (2.3696.120.41.1.2) X-Provags-ID: V03:K1:iYzduT1qABatjiiW2We2tQiPl9JPGZrQjykalfcp0XR47qrlqDF PHjdwHhKjJeZdH7v9LXKbLT8W0vQV93dBldT6OPpZYe4TKJgFFjhcwD1VEkvLNNCtfY/cQm DUaq8QHxOnFGCl2XQYWuHiB03V7W1i53tiVXOm/wXYqcw0gu+ae1Bz6t2sRc9jJAK4tm/f8 dSpVI+XlO9otAv190TrPA== X-Spam-Flag: NO UI-OutboundReport: notjunk:1;M01:P0:a5LmzsHBrhE=;URkpI8goBjVlL0rJMl7GLne+UBR Pm4m1eYdFFDw0Vo4lzQJrsISE8Hsc3hgd82KsaRAtgtYoL5DZuPXwQ1Y9QlDG7zYMg1xGsggR DTPwOxvAXLlZx3U3m17UcpqAm5ptMvYT/lmpH1TatrodN4ZDYf8iL2cWsGmQ2INism66rS+iN lWgPwQ2LkqTnbq/1w+xxnSfhOuhc1LmFa6WLLJtJn3/OlkhecQSlHWubPCha9tzu7Eb6E6HCK NCM5D9lZO45GzmlP37Up+Xq7wtaemEc3eqpXR1Z0b8236JmhXwO7BiqVI6gCL7OG6RDcYtdZd YkeZMo1QxPqI0MTAdCepMMv7uNmZ5UwQXH79cf8NmQzgG0T1sc/nhz9N8EgGpUQn863Q8XWSI ZpfqWS+o6O9oi0V2FyHGgF3LA6+pRBAeP5pkIrW9x8qUaNbocHYA2S1YoEbGlzi84BoCmL3U8 /PmwGgr5c9Rrc0itgA3CP8XnhmWdADOgKkjXDK1Tpdxsv7oacjIkk7L8+PQrPlCPG2bYuR4zj PuwURBXNaRvDFzFP8oM6IoTmcxHqdkifV+UBzMsfDTwz+9d9Sddm9geTq4YCeaXQshtKqbm0t faQdlND4020rEmyIO7gXQoM+AhilIAPc7jd7nXq7Sq4CyOCluc4pdwnbTxItRaKX9cddu7GJf jQ32JyJCieT6ufSdMv4VWx1WdbvP8hqpTiCQIdEODwAl6d12zGTUaV/YQSU79LFZABhW7SCG3 llYCleDudgLSw7L6aQdY8+RN0lrGngV1xnF+wKeX4uB6wg6B5mIpNKvm3aztJCcTmcaM25Mc0 32RnUjw0tX7R1Y+ABSDuiD89jFb3ZF6/djOHjUjsuxmLhHzz+EFBZ8irx6zhhjpdxINj7ASwH SDmzP1puXxkaerj0CnsO8IIf3y7m4/KNj7jyFQ9c8a8cMy+vQQS1TE/JQTkx8bzhPH0UmvdJM ZdctFw== Subject: Re: [Bloat] Hey, all, what about bandlength? 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, 10 Apr 2023 11:30:17 -0000 Hi Dave, > On Apr 10, 2023, at 01:04, David Lang via Bloat = wrote: >=20 > TCP ramps up it's speed fairly slowly, and backs off fairly = drastically when it is told (via ECN or a dropped packet) that it has = hit the limit. [SM] That is the prevailing narrative, yes. However during slow = start most/many TCPs double the congestion window every RTT and since it = takes up to a full RTT for a drop or CE mark to be fed back to the = sender, TCPs can end up with a congestion window that is up to twice as = large as sustainable, so the "classic" halving of the congestion window = when dropping out of slow-start seems not like a bad idea... after that = the congestion window increase rate will be somewhat slower... > As a result, a single TCP session is not going to fully utilize a = connection. [SM] In my experience even single TCP flows can get close to = saturation (but I typically do such tests over short paths...) > There are people who do large, high speed transfers over long = distances on a regular basis (think movie studios sending uncompressed = movie footage around the world for processing). [SM] Yes, that is not me ;) > To fully utilize their bandwidth, they use protocols that involve lots = of connections operating in parallel [SM] Or stick to TCP but run a few connections in parallel, if = these are not synchronized the aggregate ends up saturating a path = pretty well (within reason, over long RTT paths the control loop simply = is not as "tight" as over short RTT paths...) Regards Sebastian >=20 > David Lang >=20 > On Sun, 9 Apr 2023, Dave Collier-Brown via Bloat wrote: >=20 >> Date: Sun, 9 Apr 2023 16:06:54 -0400 >> From: Dave Collier-Brown via Bloat >> Reply-To: Dave Collier-Brown >> To: bloat@lists.bufferbloat.net >> Subject: Re: [Bloat] Hey, all, what about bandlength? >> Consider a connection to my ISP as being an empty water-pipe, and I = only want to measure the flow from the waterworks to me. In this case = the waterworks is Rogers in Toronto, and the numbers come from me = measuring the link with the Waveform bufferbloat tool. >>=20 >> The ISP promises me 1 Gbit/s of water. OK, there is no such thing, = but you get the idea (;-)) >>=20 >> Let's consider the no-latency case. >>=20 >> * The ISP turns on the tap, and it takes half an RTT to get to me, = one way. Let that be 1 millisecond, 0.001s of delay. >> * Once the delay is over, I get (1.0s - 0.001s) * 1 Gbit/s =3D = 0.999 Gb/s. The 0.999 seconds is transfer time, and that transfer is at = full speed of the pipe, so it adds up to 0.999 Gb/s >> * That's pretty good. >>=20 >> Now let's consider the best possible case where there is latency, but = only one delay of 0.456s. That basically means that only one transfer = happens in the second, so there is only once change for latency to hurt = me. >>=20 >> * the one-way delay is still 0.001s, but there is also 0.231s of = latency, for a delay of 0.232s >> * (1.0s - (0.001s + 0.231s) ) * 1 Gbit/s =3D >> * 1.0s - 0.232s =3D 0.549s * 1 Gbit/s =3D 0.768 GB/s >> * Cut by a quarter, by one packet's delay >>=20 >> What about the worst case? >>=20 >> * It's not worst, but a pretty common case is a busy link with = 1500-byte packets >> * One packet is 12,000 bits >> * In one second we can transfer 1,000,000,000 bits / = 12,000bits/packet =3D 83,333.3 packets >> * Maybe that many delays, too? >> * Fortunately, no >>=20 >> I personally observed 456.2 Mbit/s, about 54% of a gigabit at home, = so it's more like the latency cut my bandwidth in half >>=20 >> --dave >>=20 >>=20 >> On 4/8/23 22:32, Michael Richardson via Bloat wrote: >>=20 >>=20 >> Dave Collier-Brown = wrote: >> >> Dave Collier-Brown via = Bloat = wrote:=20 >>>=20 >> >> They he said "bandlength" >> >> >> >> > That sounded like an odd name, but the idea was cool: >> >> >> >> > If I have a bandwidth of 1 Mbit/S, but it takes 2 seconds to = deliver >> >> 1 > Mbit, do I have a bandlength of only 1/2 Mbit/S? >> >> >> >> Is that because there is 2seconds of delay? >>=20 >> > Well, 2 seconds elapsed time, 1 of which is delay. >>=20 >> Ah, would that include the delay to ask for the data? >> (A DNS request, or an HTTP GET) >>=20 >>=20 >>=20 >>=20 >> CONFIDENTIALITY NOTICE AND DISCLAIMER : This telecommunication, = including any and all attachments, contains confidential information = intended only for the person(s) to whom it is addressed. Any = dissemination, distribution, copying or disclosure is strictly = prohibited and is not a waiver of confidentiality. If you have received = this telecommunication in error, please notify the sender immediately by = return electronic mail and delete the message from your inbox and = deleted items folders. This telecommunication does not constitute an = express or implied agreement to conduct transactions by electronic = means, nor does it constitute a contract offer, a contract amendment or = an acceptance of a contract offer. Contract terms contained in this = telecommunication are subject to legal review and the completion of = formal documentation and are not binding until same is confirmed in = writing and has been signed by an authorized signatory. > _______________________________________________ > Bloat mailing list > Bloat@lists.bufferbloat.net > https://lists.bufferbloat.net/listinfo/bloat > _______________________________________________ > Bloat mailing list > Bloat@lists.bufferbloat.net > https://lists.bufferbloat.net/listinfo/bloat