From owner-freebsd-net@FreeBSD.ORG Mon May 22 16:11:53 2006 Return-Path: X-Original-To: freebsd-net@freebsd.org Delivered-To: freebsd-net@freebsd.org Received: from mx1.FreeBSD.org (mx1.freebsd.org [216.136.204.125]) by hub.freebsd.org (Postfix) with ESMTP id 5DF1116B6AA for ; Mon, 22 May 2006 16:11:53 +0000 (UTC) (envelope-from nitro@263.net) Received: from smtp.263.net (smtp.x263.net [211.150.96.21]) by mx1.FreeBSD.org (Postfix) with ESMTP id DA56443D66 for ; Mon, 22 May 2006 16:11:49 +0000 (GMT) (envelope-from nitro@263.net) Received: from intron.ac (unknown [127.0.0.1]) by smtp.263.net (Postfix) with SMTP id E974AF134C for ; Tue, 23 May 2006 00:11:47 +0800 (CST) X-KSVirus-check: 0 References: <20060522115722.15918F1590@smtp.263.net> <20060522135542.GC22140@mauser.ipx.ath.cx> <20060522152402.GD22140@mauser.ipx.ath.cx> In-Reply-To: <20060522152402.GD22140@mauser.ipx.ath.cx> From: mag@intron.ac To: Joshua Blanton Date: Tue, 23 May 2006 00:10:26 +0800 Mime-Version: 1.0 Content-Type: text/plain; charset="gb2312"; format=flowed Content-Transfer-Encoding: 7bit Message-Id: <20060522161147.E974AF134C@smtp.263.net> Cc: freebsd-net@freebsd.org Subject: Re: How to Quicken TCP Re-transmission? X-BeenThere: freebsd-net@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: Networking and TCP/IP with FreeBSD List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Mon, 22 May 2006 16:12:00 -0000 Joshua Blanton wrote: > mag@intron.ac wrote: >> Actually, I want to configure APACHE to distribute files (several >> mega bytes large each) to any Internet visitor. >> >> My server (host A) is served by a non-profitable Internet operator >> in China. But most of Chinese Internet users (host B) are served by two >> commercial Internet operators. >> Between the non-profitable Internet operator and each commercial >> Internet operator there is an about 2 Gbps interconnection. But China >> has a large population, and those interconnections are heavily loaded. > > Unfortunately, if your loss is caused by congestion, there really > isn't anything you can do (ethically) to make it run faster. Any > changes that you would make to your TCP stack would result in > reducing usable bandwidth for every other user of the network. It > really isn't fair to make any changes at all... You are quite right. It would be unfair. > >> I obtained the result "packet loss 30% and return delay 60 ms" >> just by "ping -c 100 -s 1472 xxx.xxx.xxx.xxx". If an IP packet is >> smaller as 20+64=84 bytes (PING's default), it will has much higher >> possibility to pass the interconnections between Internet operators. > > Now, it is possible that your loss isn't really 30% - if these links > are as overloaded as you say, I'm sure ICMP Echo packets are dropped > with much more frequency than other packets, to help reduce > congestion. Your judgement should be right. > >> It seems that FreeBSD 6.1 kernel enables SACK (RFC 2018) by default >> (net.inet.tcp.sack.enable: 1). And I keep it untouched. >> >> Since I want configure general WWW service, probably I could not >> request visitors to configure SCPS. It is really robust against lossy >> data link such as communication between satellites and planets. >> But above all, most of Internet users haven't enough computer skills. >> >> I would like to understand how FreeBSD runs the TCP re-transmission >> timer, especially its dynamic self-tuning mechanism. I am trying to >> read /usr/src/sys/netinet/tcp* . >> Should I really modify the value of "TCPTV_REXMTMAX" defined in >> "/usr/src/sys/netinet/tcp_timer.h" ? > > I think perhaps the only solution is to learn to live with the slow > upload times, or find a provider that can guarantee better service. > > --jtb In China, it is the only solution to set up multi mirrors served by multi operators. But I'm so poor. ------------------------------------------------------------------------ From Beijing, China