From nobody Tue Oct 19 09:40:32 2021 Return-Path: X-Original-To: ntp@ietfa.amsl.com Delivered-To: ntp@ietfa.amsl.com Received: from localhost (localhost [127.0.0.1]) by ietfa.amsl.com (Postfix) with ESMTP id 908663A0D94 for ; Tue, 19 Oct 2021 09:40:29 -0700 (PDT) X-Virus-Scanned: amavisd-new at amsl.com X-Spam-Flag: NO X-Spam-Score: -1.902 X-Spam-Level: X-Spam-Status: No, score=-1.902 tagged_above=-999 required=5 tests=[BAYES_00=-1.9, NICE_REPLY_A=-0.001, SPF_PASS=-0.001] autolearn=ham autolearn_force=no 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 vXDofkNetobV for ; Tue, 19 Oct 2021 09:40:25 -0700 (PDT) Received: from chessie.everett.org (chessie.everett.org [IPv6:2001:470:1:205::234]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by ietfa.amsl.com (Postfix) with ESMTPS id 049223A0D91 for ; Tue, 19 Oct 2021 09:40:24 -0700 (PDT) Received: from [192.168.1.193] (pool-108-26-179-179.bstnma.fios.verizon.net [108.26.179.179]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by chessie.everett.org (Postfix) with ESMTPSA id 4HYfcL5j4JzMNYM; Tue, 19 Oct 2021 16:40:18 +0000 (UTC) Message-ID: <0d94bb6d-237d-5a8f-52af-b96f2355c6b3@pdmconsulting.net> Date: Tue, 19 Oct 2021 12:40:17 -0400 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.15; rv:91.0) Gecko/20100101 Thunderbird/91.2.0 Content-Language: en-US To: Tony Finch Cc: Hal Murray , NTP WG References: <20211015210250.6330328C0F3@107-137-68-211.lightspeed.sntcca.sbcglobal.net> <2ee63d83-cde0-4665-52e1-5fa0d18325e@dotat.at> <4cfe73c5-baee-db8e-549f-2088067dcaf6@pdmconsulting.net> From: Danny Mayer In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Archived-At: Subject: Re: [Ntp] Smearing X-BeenThere: ntp@ietf.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Network Time Protocol List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Tue, 19 Oct 2021 16:40:30 -0000 On 10/19/21 12:15 PM, Tony Finch wrote: > Danny Mayer wrote: >> It also indicates if there is a leapsmear in progress, the type of smearing >> done (there are a number of different ones) by including a smearing ID. > Are there good reasons for needing more than one kind of smear? > > As I understand it, the most prominent leap smear deployments have > converged on: > > * 24h smear, not too long but long enough that NTP clients will notice > the rate change even with a 1024 second polling interval, and the rate > change is small enough that NTP clients are willing and able to follow it > > * smear from midday to midday around the leap second, to keep the phase > error below 0.5 seconds > > * use a linear smear, because NTP clients are better at following > constant rates (a cosine or other smoothing means the rate changes > continuously during the smear, which NTP does not handle so well) > > Tony. You've just outlined the ones we know about. A client may want to follow one or the other or none. That's a policy decision so let the client make it. That's why embedding a smearing ID in the packet makes sense. Danny