From nobody Fri Mar 12 10:09:10 2021 Return-Path: X-Original-To: quic@ietfa.amsl.com Delivered-To: quic@ietfa.amsl.com Received: from localhost (localhost [127.0.0.1]) by ietfa.amsl.com (Postfix) with ESMTP id A1B373A1958 for ; Fri, 12 Mar 2021 10:09:08 -0800 (PST) X-Virus-Scanned: amavisd-new at amsl.com X-Spam-Flag: NO X-Spam-Score: -2.097 X-Spam-Level: X-Spam-Status: No, score=-2.097 tagged_above=-999 required=5 tests=[BAYES_00=-1.9, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, FREEMAIL_FROM=0.001, HTML_MESSAGE=0.001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001, URIBL_BLOCKED=0.001] autolearn=ham autolearn_force=no Authentication-Results: ietfa.amsl.com (amavisd-new); dkim=pass (2048-bit key) header.d=gmail.com Received: from mail.ietf.org ([4.31.198.44]) by localhost (ietfa.amsl.com [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id QzPJgPFgXXBQ for ; Fri, 12 Mar 2021 10:09:06 -0800 (PST) Received: from mail-lj1-x235.google.com (mail-lj1-x235.google.com [IPv6:2a00:1450:4864:20::235]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by ietfa.amsl.com (Postfix) with ESMTPS id 2050D3A195D for ; Fri, 12 Mar 2021 10:09:06 -0800 (PST) Received: by mail-lj1-x235.google.com with SMTP id 9so7902953ljd.7 for ; Fri, 12 Mar 2021 10:09:06 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=from:message-id:mime-version:subject:date:in-reply-to:cc:to :references; bh=WWe0e3VezES7YwB1HZK3f+F7Kia42+xa4LZr+1UCkjY=; b=g46aSK3kILg3lyeCeacpEzkMSkPDPr+CXWCOUNf90uPdcqwizQjGXOfHI2a5GANnJR iv8nuq3OABo6yOSBM7pwTongLPSk1I6DUSDn6vzPAKIZ7c+9hw/cxlhSMjfDTmeyMaNN kosYTje5cFLFm+5FnnwCbOtaIl2RNivmH4aUayYUdGraTTEcDmTBfaQWPUhhhbb6ga76 dpbYC3aB9xqJDMEmXFmEj2K/hw/orgS/Z17JRx5ajrz7Is0RvUFLJBlJZ8YxIdyPp09O PBjjjHmNiyotuWLE0fYkclpp0/X1GpGFwWQKF10x92xEGK73iM2n6XeI4OIdvl2rLO7i XIJw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:from:message-id:mime-version:subject:date :in-reply-to:cc:to:references; bh=WWe0e3VezES7YwB1HZK3f+F7Kia42+xa4LZr+1UCkjY=; b=UNzboufcYiJY13YGDVxUuzh4/f+WOAEHGhw4CRIjk7l/CgP+ve374rrJP1gE0FC7Ar gKQq3Pri6IUcrWIZAZ7v9D3WmNAqyVlnkE8dlIhm+JsQFsjteTtx+0uuXMiMjXwdQz57 ypiQ0Ns0gjo99gOEkiw2oE6Gw066exzd/JhcOsRUY3So++RNGw+vx0/sib6AqChFRu9t kOygjfutVVdMSTlIPQ2yh2Tgv8gPBcqJRxwommJzNy/DM0eDcfDhLyVt0715MQSwBhbw uBkUZf0+y947wjb9f6NkLDu94xSPRx5xJF9Gwo/aGIJe1vdhNl838tpTgOWXxMAM6ZjR RtuQ== X-Gm-Message-State: AOAM530MtPK1moBrOAKIJmZxC4qSMLvphfRuP21VvxLdHS8e45w1fFcQ 4lc49nUyUmSLv5f8TkCSakA= X-Google-Smtp-Source: ABdhPJxyP7VFUwToRyeUkCIAEvkXatNz9rR/kedHTVYCHc54/vhFCWT2SraycS6CaJKvSyTKt7yiLQ== X-Received: by 2002:a2e:b601:: with SMTP id r1mr3166881ljn.271.1615572539055; Fri, 12 Mar 2021 10:08:59 -0800 (PST) Received: from [192.168.1.4] ([87.72.40.193]) by smtp.gmail.com with ESMTPSA id u22sm2061296ljk.6.2021.03.12.10.08.58 (version=TLS1_2 cipher=ECDHE-ECDSA-AES128-GCM-SHA256 bits=128/128); Fri, 12 Mar 2021 10:08:58 -0800 (PST) From: =?utf-8?Q?Mikkel_Fahn=C3=B8e_J=C3=B8rgensen?= Message-Id: <1B7BEBA6-FF98-45AD-A5AB-F9EE702359C6@gmail.com> Content-Type: multipart/alternative; boundary="Apple-Mail=_B60C845C-C948-4369-83A6-64E6548BCE2B" Mime-Version: 1.0 (Mac OS X Mail 13.4 \(3608.120.23.2.4\)) Subject: Re: Some late comments on draft-ietf-quic-load-balancers Date: Fri, 12 Mar 2021 19:08:57 +0100 In-Reply-To: Cc: IETF QUIC WG To: Watson Ladd References: X-Mailer: Apple Mail (2.3608.120.23.2.4) Archived-At: X-BeenThere: quic@ietf.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Main mailing list of the IETF QUIC working group List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Fri, 12 Mar 2021 18:09:09 -0000 --Apple-Mail=_B60C845C-C948-4369-83A6-64E6548BCE2B Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset=us-ascii Just to add some background. UTC is Universal Time Coordinated. Universal Time is more genereal. Disregarding timezones, we have UTC as a single point of reference. = Predictably there is an adjustment every fourth year, except every 100th = year, unless it is every 400th year. Also an adjustment is needed about = every 4000 years or so, but that is not part of UTC so far. The problem is that this is not enough because earth wobbles = unpredictably. So we have unpredictable leap seconds that are added or = subtracted or left unchanged at predictable intervals based on short = term observations. Leap seconds are relevant in some areas because the = earth can move a fair bit in one second. This is where UT1 time comes in = as one of several ways to accommodate the imprecision of UTC. Most computer systems opt to define time as a monotonically increasing = offset in seconds and fractions of seconds since midnight, January 1st, = 1970 as observed from Greenwich, London. This is also known as Unix = Time. Unix Time maps cleanly to UTC time to the extent that Unix Time = can be seen as a UTC representation. This avoids any abrupt jumps in = time, or slowly accelerated time up to leap second changes. UT1 cannot = be mapped cleanly from Unix Time because it needs an earth wobble table = to perform the translation, and that table needs to be kept up to date = (literally). However, even accounting for earths wobbling is not enough if you want = to be really exact. In this case you cannot really tell the order of = events any more: = https://www.quantamagazine.org/quantum-mischief-rewrites-the-laws-of-cause= -and-effect-20210311/ = Trivia: the Romans made the (to my knowledge) first recorded fence post = error around year 1 by introducing leap years every 3 years instead of = every 4 years. After about 30 years the error became apparent and was = fixed. Mikkel > On 11 Mar 2021, at 23.48, Watson Ladd wrote: >=20 > Dear QUIC WG, >=20 > First a moment of unforgivable pedantry. Universal time is > unfortunately not the right name for UTC, which is slightly different. > It could also mean UT1 or some other variations It's also not clear > what the future of computer timekeeping is and I know several places > don't synchronize to UTC internally. I think the best way to handle > this is to say something like "synchronized" and leave open as to > exactly how that is done. >=20 > I agree with the comments that there are too many options and should > be fewer. Other then that I didn't see any problems but I'm probably > too sleepy right now to spot them. >=20 > Sincerely, > Watson Ladd > --=20 > Astra mortemque praestare gradatim >=20 --Apple-Mail=_B60C845C-C948-4369-83A6-64E6548BCE2B Content-Transfer-Encoding: quoted-printable Content-Type: text/html; charset=us-ascii Just = to add some background.

UTC is Universal Time Coordinated. Universal Time is more = genereal.

Disregarding timezones, we have UTC as a single point of = reference. Predictably there is an adjustment every fourth year, except = every 100th year, unless it is every 400th year. Also an adjustment is = needed about every 4000 years or so, but that is not part of UTC so = far.

The = problem is that this is not enough because earth wobbles unpredictably. = So we have unpredictable leap seconds that are added or subtracted or = left unchanged at predictable intervals based on short term = observations. Leap seconds are relevant in some areas because the earth = can move a fair bit in one second. This is where UT1 time comes in as = one of several ways to accommodate the imprecision  of = UTC.

Most = computer systems opt to define time as a monotonically increasing offset = in seconds and fractions of seconds since midnight, January 1st, 1970 as = observed from Greenwich, London. This is also known as Unix Time. Unix = Time maps cleanly to UTC time to the extent that Unix Time can be seen = as a UTC representation. This avoids any abrupt jumps in time, or slowly = accelerated time up to leap second changes. UT1 cannot be mapped cleanly = from Unix Time because it needs an earth wobble table to perform the = translation, and that table needs to be kept up to date = (literally).

However, even accounting for earths wobbling is not enough if = you want to be really exact. In this case you cannot really tell the = order of events any more:
https://www.quantamagazine.org/quantum-mischief-rewrites-the-la= ws-of-cause-and-effect-20210311/

Trivia: the Romans made the (to my = knowledge) first recorded fence post error around year 1 by introducing = leap years every 3 years instead of every 4 years. After about 30 years = the error became apparent and was fixed.

Mikkel

On 11 = Mar 2021, at 23.48, Watson Ladd <watsonbladd@gmail.com> wrote:

Dear = QUIC WG,

First a moment of unforgivable = pedantry. Universal time is
unfortunately not the right = name for UTC, which is slightly different.
It could also = mean UT1 or some other variations  It's also not clear
what the future of computer timekeeping is and I know several = places
don't synchronize to UTC internally. I think the = best way to handle
this is to say something like = "synchronized" and leave open as to
exactly how that is = done.

I agree with the comments that there = are too many options and should
be fewer. Other then that = I didn't see any problems but I'm probably
too sleepy = right now to spot them.

Sincerely,
Watson Ladd
--
Astra mortemque = praestare gradatim


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