From mboxrd@z Thu Jan 1 00:00:00 1970 Authentication-Results: mail.toke.dk; spf=pass smtp.mailfrom=; dkim=pass header.d=gmx.de header.i=moeller0@gmx.de; arc=none (Message is not ARC signed); dmarc=pass (Used From Domain Record) header.from=gmx.de policy.dmarc=quarantine Received: from mout.gmx.net (mout.gmx.net [212.227.15.15]) by mail.toke.dk (Postfix) with ESMTPS id AE44C119C095; Mon, 01 Jun 2026 07:54:51 +0200 (CEST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmx.de; s=s31663417; t=1780293290; x=1780898090; i=moeller0@gmx.de; bh=gurPrMEPcv7EeO6tOBconC6eYF8+f7kEf0Qa3aBLB9Q=; h=X-UI-Sender-Class:Content-Type:Mime-Version:Subject:From: In-Reply-To:Date:Cc:Content-Transfer-Encoding:Message-Id: References:To:cc:content-transfer-encoding:content-type:date:from: message-id:mime-version:reply-to:subject:to; b=XonlArPvutcS5ZGk0GY3PF2/uFj+GPpL6UE9KiFZS7b9e7Q4aVLx9tDPL+46+7pE XzBro/3RKNSCXchEL3eIkTAxD09hiRaYcUOEFmDXshSViNUMkkSrgHXntcv5YuLM1 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h9agSC6aK2t7wQWVbTx95PNDwuxjTWC1sZZnLACDP7isU6bsXM6BJkl1l6uFd5D05gEZXc5KC LbjkuVAlYyrLHYqmZ8VF5hzqOqlyVjMmHw5wpe7wlKku4YRTVDwKKC5LInAYe99+KjVcRAlAT gjlJ4Xp3Xz1hSxK/azo2bSB5KIcO+2IlybX9qiawf2CgJ3AnnLeRfeVSAsKurO3jgqDrLG8N9 vNCJ9IWYrMPTBpW96KxOddK5EGCxWksB71DLJqX63mqTFo2Nf5/jDxvMaC03q8Qz/yUicfoZ3 hfVbS+7jgHjnoen6i37vLtLwhXgxNP5lnUoldjNQrSzuZdTM9hVq1Y6KsdKNLBwqaOoGOS4hD Q1kQkQpj9258DoFLl2C+8GBpUgOWr+8sfzQHVzHEYVcvLpeuFgMskUFbn/JkVSUM4Q6RxQr5R PNToRkW/lxZ9JBbx9Yt6DeMaYwSOvVl4HGzUE3ZMVNtLlh5+SBlI01iucOWFDMmm0vWEk5xt8 q6z8KOu5gx5jYPxZYqwXU Message-ID-Hash: 6LJEUWLCYFZR2GQOO7ZQRVE32GFOX6HS X-Message-ID-Hash: 6LJEUWLCYFZR2GQOO7ZQRVE32GFOX6HS X-MailFrom: moeller0@gmx.de X-Mailman-Rule-Misses: dmarc-mitigation; no-senders; approved; loop; banned-address; emergency; member-moderation; nonmember-moderation; administrivia; implicit-dest; max-recipients; max-size; news-moderation; no-subject; digests; suspicious-header X-Mailman-Version: 3.3.10 Precedence: list Subject: [Cake] Re: [ih] Bandwidth v Capacity [Early Internet Report when Vint was at Stanford (and DARPA PI)] List-Id: Cake - FQ_codel the next generation Archived-At: List-Archive: List-Help: List-Owner: List-Post: List-Subscribe: List-Unsubscribe: Mmmh, from the meta-peanut gallery a) The man's name was Heinrich Hertz, and so the unit's name is hertz as = well, not herz. Typically I would just silently correcting this = internally when reading a text and not bother, but when a text is trying = to show how to correctly name things, it should lead by example. b) Just to be contrarian, how about using "data rate" or "information = rate" when talking about what is achieved, capacity being the achievable = limit of said rate and bandwidth being the spectrum allotted (I know, = too easy)? c) That ship has sailed, language is adaptable and typically dies not = ask permission when changing connotations and usage/meaning.=20 d) Not that it matters, I agree that bandwidth and capacity should not = be confused (but see c) ) or we end up with bangers like: "out of a bandwidth of X Hz our modulation and encoding scheme = allows a total bandwidth of Y Bits/second out of which a bandwidth of Z = Bis/seconds were achieved in real world testing." Re > On May 31, 2026, at 13:49, Frantisek Borsik = wrote: >=20 > Forwarding for visibility - a great "rant" on the usage of "bandwidth" = vs > "capacity", from Brian E. Carpenter = https://profiles.auckland.ac.nz/bcar071 >=20 > To read more, from people like Vint Cerf or John Day, on this topic, = take a > look into the archive: > = https://elists.isoc.org/pipermail/internet-history/2026-May/thread.html#st= art >=20 > All the best, >=20 > Frank >=20 > Frantisek (Frank) Borsik >=20 >=20 > *In loving memory of Dave T=C3=A4ht: *1965-2025 >=20 > https://libreqos.io/2025/04/01/in-loving-memory-of-dave/ >=20 >=20 > https://www.linkedin.com/in/frantisekborsik >=20 > Signal, Telegram, WhatsApp: +421919416714 >=20 > iMessage, mobile: +420775230885 >=20 > Skype: casioa5302ca >=20 > frantisek.borsik@gmail.com >=20 >=20 > ---------- Forwarded message --------- > From: Brian E Carpenter via Internet-history < > internet-history@elists.isoc.org> > Date: Sat, May 30, 2026 at 11:55=E2=80=AFPM > Subject: [ih] Bandwidth v Capacity [Early Internet Report when Vint = was at > Stanford (and DARPA PI)] > To: Internet History >=20 >=20 > Hi, >=20 > Yes, that's a very nice slice of history. It leads me to one of my = hobby > horses: when did the solecism of using "bandwidth" to mean "capacity" = first > arise? This is something that should annoy every physicist, or anyone = who > has read Shannon's foundational paper [1]. Unfortunately, it's become > firmly established in the Internet community and beyond. And it = matters > because it quite often creates confusion, particularly in media = reports. >=20 > * Bandwidth is measured in herz (cycles per second) and is the = frequency > range that a communication channel can transmit. >=20 > * Capacity is measured in bits per second and is the amount of binary > information that a communication channel can transmit. >=20 > There is no fixed relationship between the two (which is more or less = the > main point of Shannon's paper). Anyone who ever heard the startup = screeches > of a modem should know this. >=20 > To illustrate the issue, page 1 of Vint's report says: >=20 > "During the months of December (1975) and January (1976), we undertook > extensive and detailed timing measurements of the ELF VDH behavior to > ascertain the degree to which VDH performance affected total TCP > bandwidth and delay." >=20 > That (and the other 14 occurrences of "bandwidth") should be = "capacity." >=20 > Page 8 says: >=20 > "The actual > line utilization is about 20% in each direction, assuming a nominal 50 > kbits/second available full-duplex capacity between ELF and the IMP." >=20 > That's correct usage. >=20 > My favourite sentence is on page 45: >=20 > "Many of the experiments have been > frustrating, owing to a bug of some kind in UCL's buffer allocation = scheme > causing them to crash irrevocably when attempting to achieve high > bandwidth." >=20 > If only they had tried to achieve high capacity! >=20 > So, my question is: when did this inaccurate use of "bandwidth" to = mean > "capacity" first arise? It was clearly well established by 1975. >=20 > I looked in Donald Davies's book [2], and it only uses "capacity" (I = would > expect no less of him). Baran in 1964 [3] used "capacity" correctly = many > times. He also used "bandwidth" correctly once [5] and debatably a = second > time [6]. >=20 > Pierce [4] in 1961 was completely clear on the difference between = bandwidth > and capacity (and he learned directly from Shannon). >=20 > Regards/Ng=C4=81 mihi > Brian Carpenter >=20 > [1] C. E. Shannon, "Communication in the Presence of Noise," = Proceedings of > the IRE, vol. 37, no. 1, pp. 10-21, Jan. 1949 > [2] D. W. Davies, D. L. A. Barber, W. L. Price & C. M. Solomonides, > "Computer Networks and their Protocols," Wiley, 1979 > [3] P. Baran, "On Distributed Communications Networks," IEEE = Transactions > on Communication Systems, Vol. 12 No. 1, 1964, pp. 1-9 > [4] J. R. Pierce, "Symbols, Signals and Noise," Harper, 1961 >=20 > [5] "In a conventional circuit-switched system each of the > tandem links requires matched transmission bandwidths. > In order to make fullest use of a digital link, the post- > error-removal data rate would have to vary, as it is a > function of noise level." >=20 > [6] "Most importantly, standardized data blocks permit > many simultaneous users, each with widely different band- > width requirements to economically share a broad-band > network made up of varied data rate links." >=20 > On 30-May-26 15:13, Barbara Denny via Internet-history wrote: >> While poking around on DTIC, I found this interesting early report = on > the Internet while Vint was still at Stanford and Jon Postel was still = at > SRI (How many of you knew that? :-))The period of performance is Nov > 15,1975 to Feb 15 1976. >> https://apps.dtic.mil/sti/tr/pdf/ADA024823.pdf >> You can find a little bit more info by using the contract number in = dtic. >> Happy Reading,barbara > --=20 > Internet-history mailing list > Internet-history@elists.isoc.org > https://elists.isoc.org/mailman/listinfo/internet-history > - > Unsubscribe: > = https://app.smartsheet.com/b/form/9b6ef0621638436ab0a9b23cb0668b0b?The%20l= ist%20to%20be%20unsubscribed%20from=3DInternet-history > _______________________________________________ > Cake mailing list -- cake@lists.bufferbloat.net > To unsubscribe send an email to cake-leave@lists.bufferbloat.net