From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from c.mail.sonic.net (c.mail.sonic.net [64.142.111.80]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by lists.bufferbloat.net (Postfix) with ESMTPS id 0491D3B2A4 for ; Mon, 12 Dec 2022 23:32:17 -0500 (EST) Received: from 107-137-68-211.lightspeed.sntcca.sbcglobal.net (104-182-38-69.lightspeed.sntcca.sbcglobal.net [104.182.38.69]) (authenticated bits=0) by c.mail.sonic.net (8.16.1/8.16.1) with ESMTPSA id 2BD4WFwK006595 (version=TLSv1.2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128 verify=NOT); Mon, 12 Dec 2022 20:32:15 -0800 Received: from hgm (localhost [IPv6:::1]) by 107-137-68-211.lightspeed.sntcca.sbcglobal.net (Postfix) with ESMTP id 7EBB728C206; Mon, 12 Dec 2022 20:32:15 -0800 (PST) X-Mailer: exmh version 2.9.0 11/07/2018 with nmh-1.7.1 To: bloat@lists.bufferbloat.net cc: Hal Murray From: Hal Murray Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Date: Mon, 12 Dec 2022 20:32:15 -0800 Message-Id: <20221213043215.7EBB728C206@107-137-68-211.lightspeed.sntcca.sbcglobal.net> X-Sonic-CAuth: UmFuZG9tSVaeIRB8GVQ5Rd7aUjCqoL2ov7DLuX0xXQg91TGHn9RAGM1DBed5+hGwnLqRRYzO56oD5FtS/k8y9dU2dRFb6mmIMTR/wXeA9bA= X-Sonic-ID: C;bvr2Hp967RGFQRxnR+6Zsg== M;xNIJH5967RGFQRxnR+6Zsg== X-Spam-Flag: No X-Sonic-Spam-Details: -1.5/5.0 by cerberusd Subject: [Bloat] Servers, time 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: Tue, 13 Dec 2022 04:32:18 -0000 [I work on NTP software so I'm interested in network delays.] > I've been holding off on iperf 2 public servers until I found an additional > value add and a way to pay for them. AT&T ran fiber down my street. I can get a gigabit link, symmetric, no data caps, for $80/month. I'll be happy to setup a server if that will help. I'm in Silicon Valley. > Much of the iperf 2 work has been > around one way delay (OWD) or latency. Doing this well requires GPS clock > sync on both the data center servers and the end host devices How accurate do you need the time? > I checked into this a few years ago and found that this level of clock sync > wasn't available via rented servers (e.g. linode or Hurricane Electric) so I > put on hold any further investigation of public servers for iperf 2 as being > redundant with iperf 3. Those that need true e2e latency (vs RTTs) have to > build their own so-to-speak. I can see 2 approaches. One is to find good local NTP servers. HE has NTP servers. https://www.he.net/adm/ntp.html NIST has servers in Gaithersburg MD and Boulder and Fort Colins in Colorado. https://tf.nist.gov/tf-cgi/servers.cgi Google and Cloudflare have good servers and they probably have good connectivity. https://developers.google.com/time https://www.cloudflare.com/time/ In Germany, PTB has good servers: https://www.ptb.de/cms/en/ptb/fachabteilungen/abtq/gruppe-q4/ref-q42/time-syn chronization-of-computers-using-the-network-time-protocol-ntp.html ..... The other approach would be to do your own NTP like time sync with the server before and after a test run. This assumes you can find a quiet time to get a good measurement. NTP assumes that the routing delays are symmetric. Unless something wild is going on, that's a reasonable assumption. Less so on longer paths. I'll be glad to help set something up and/or run some tests. -- These are my opinions. I hate spam.