From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-ig0-x22d.google.com (mail-ig0-x22d.google.com [IPv6:2607:f8b0:4001:c05::22d]) (using TLSv1 with cipher RC4-SHA (128/128 bits)) (Client CN "smtp.gmail.com", Issuer "Google Internet Authority G2" (verified OK)) by huchra.bufferbloat.net (Postfix) with ESMTPS id B0D6621F359 for ; Wed, 22 Apr 2015 23:48:41 -0700 (PDT) Received: by igbyr2 with SMTP id yr2so16482602igb.0 for ; Wed, 22 Apr 2015 23:48:40 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20120113; h=message-id:subject:from:to:cc:date:in-reply-to:references :content-type:mime-version:content-transfer-encoding; bh=NkSFHUG6Krd8NbJ89Sf5cK1MRZzp0w+NwTvhLF3tYLE=; b=vDkNtbYqOstRrEvB86zH/XfiKMQkR4s0OSjJqCo0l8oIY8ZRxc+LI16s6zFAywlyvx c1gB3suMmYqiZZnhfCNS8wolPZ6zTTALfvE90fWpRqdHyMsbZa/YDmyzU3XLBU2g9xpv EtAn6uTQD7B0OPk2ZM6cCBoEiWMIPU7tNl/5DN08C6XltqcM35B0i7GJIjaUf6poGKOQ MTwJHaMZn6b+p0apCrQ2gPyzK60I6Wf5dkMbmbAnXAtnRzr1onD7z8qTXvRJZrK0KAgX Ip3vBjgLrNqvuQwWj9ve/m1veD2YvUj4yZyXtFyH9OsdzD3VNhZSnxzknORjFUqpobPh pr/A== X-Received: by 10.107.149.196 with SMTP id x187mr1785318iod.4.1429771720567; Wed, 22 Apr 2015 23:48:40 -0700 (PDT) Received: from [172.26.55.207] ([172.26.55.207]) by mx.google.com with ESMTPSA id lp7sm11738727igb.20.2015.04.22.23.48.38 (version=TLSv1.2 cipher=AES128-GCM-SHA256 bits=128/128); Wed, 22 Apr 2015 23:48:39 -0700 (PDT) Message-ID: <1429771718.22254.32.camel@edumazet-glaptop2.roam.corp.google.com> From: Eric Dumazet To: MUSCARIELLO Luca IMT/OLN Date: Wed, 22 Apr 2015 23:48:38 -0700 In-Reply-To: <553882D7.4020301@orange.com> References: <2C987A4B-7459-43C1-A49C-72F600776B00@gmail.com> <14cd9e74e48.27f7.e972a4f4d859b00521b2b659602cb2f9@superduper.net> <20150422040453.GB36239@sesse.net> ,<1429676935.18561.42.camel@edumazet-glaptop2.roam.corp.google.com> <12383_1429692679_55376107_12383_9099_1_p7gmr0psut68sen0sao8o4lp.1429692550899@email.android.com> ,<1429710657.18561.68.camel@edumazet-glaptop2.roam.corp.google.com> <25065_1429716388_5537BDA4_25065_2328_1_63pyislbvtjf653k3qt8gw2c.1429715929544@email.android.com> <1429717468.18561.90.camel@edumazet-glaptop2.roam.corp.google.com> <5537CDB7.60301@orange.com> <1429722979.18561.112.camel@edumazet-glaptop2.roam.corp.google.com> <5537DA20.1090008@orange.com> <5537DE4D.8090100@orange.com> <553882D7.4020301@orange.com> Content-Type: text/plain; charset="UTF-8" X-Mailer: Evolution 3.10.4-0ubuntu2 Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Cc: bloat Subject: Re: [Bloat] DSLReports Speed Test has latency measurement built-in X-BeenThere: bloat@lists.bufferbloat.net X-Mailman-Version: 2.1.13 Precedence: list List-Id: General list for discussing Bufferbloat List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Thu, 23 Apr 2015 06:49:10 -0000 Wait, this is a 15 years old experiment using Reno and a single test bed, using ns simulator. Naive TCP pacing implementations were tried, and probably failed. Pacing individual packet is quite bad, this is the first lesson one learns when implementing TCP pacing, especially if you try to drive a 40Gbps NIC. https://lwn.net/Articles/564978/ Also note we use usec based rtt samples, and nanosec high resolution timers in fq. I suspect the ns simulator experiment had sync issues because of using low resolution timers or simulation artifact, without any jitter source. Billions of flows are now 'paced', but keep in mind most packets are not paced. We do not pace in slow start, and we do not pace when tcp is ACK clocked. Only when someones sets SO_MAX_PACING_RATE below the TCP rate, we can eventually have all packets being paced, using TSO 'clusters' for TCP. On Thu, 2015-04-23 at 07:27 +0200, MUSCARIELLO Luca IMT/OLN wrote: > one reference with pdf publicly available. On the website there are > various papers > on this topic. Others might me more relevant but I did not check all of > them. > Understanding the Performance of TCP Pacing, > Amit Aggarwal, Stefan Savage, and Tom Anderson, > IEEE INFOCOM 2000 Tel-Aviv, Israel, March 2000, pages 1157-1165. > > http://www.cs.ucsd.edu/~savage/papers/Infocom2000pacing.pdf