From owner-freebsd-net@FreeBSD.ORG Thu Dec 7 02:03:10 2006 Return-Path: X-Original-To: freebsd-net@freebsd.org Delivered-To: freebsd-net@freebsd.org Received: from mx1.FreeBSD.org (mx1.freebsd.org [69.147.83.52]) by hub.freebsd.org (Postfix) with ESMTP id 9126D16A412 for ; Thu, 7 Dec 2006 02:03:10 +0000 (UTC) (envelope-from gnn@neville-neil.com) Received: from mrout2.yahoo.com (mrout2.yahoo.com [216.145.54.172]) by mx1.FreeBSD.org (Postfix) with ESMTP id 26C3F43CB1 for ; Thu, 7 Dec 2006 02:02:20 +0000 (GMT) (envelope-from gnn@neville-neil.com) Received: from minion.local.neville-neil.com (proxy8.corp.yahoo.com [216.145.48.13]) by mrout2.yahoo.com (8.13.6/8.13.6/y.out) with ESMTP id kB721T51010673; Wed, 6 Dec 2006 18:01:32 -0800 (PST) Date: Thu, 07 Dec 2006 10:35:32 +0900 Message-ID: From: gnn@freebsd.org To: "maillist ifiaas" In-Reply-To: <161d69110612060709n3bf99bd4y47d94b021b8f1d02@mail.gmail.com> References: <161d69110612060709n3bf99bd4y47d94b021b8f1d02@mail.gmail.com> User-Agent: Wanderlust/2.14.0 (Africa) SEMI/1.14.6 (Maruoka) FLIM/1.14.8 (=?ISO-8859-4?Q?Shij=F2?=) APEL/10.6 Emacs/22.0.90 (i386-apple-darwin8.8.1) MULE/5.0 (SAKAKI) MIME-Version: 1.0 (generated by SEMI 1.14.6 - "Maruoka") Content-Type: text/plain; charset=US-ASCII Cc: freebsd-net@freebsd.org Subject: Re: Urel, a TCP option for Unreliable Streaming. Need your help. 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: Thu, 07 Dec 2006 02:03:10 -0000 At Wed, 6 Dec 2006 23:09:39 +0800, maillist ifiaas wrote: > > Hi friends, > > This is one of my research project. Our purpose is to modify TCP to > support unreliable but congestion controlled streaming. The > motivation is pretty similar to the one of DCCP CCID2. We have > implemented a prototype on FreeBSD 5.4, and the the modifications > are limited mostly in tcp_input.c and tcp_output.c. Source code, a > paper about the design (under submission), and an Iperf modification > to test out TCP Urel, is provided on the following page: > www.comp.nus.edu.sg/~malin/ > > Our current stage is changing Urel into a single directional > streaming protocol, so taht it could be abosolutely fair with > default TCP Sack, in FreeBSD. But we found after all the > modifications (on single directional streaming), Urel generates less > ACK than normal Sack, making it under utilized when competing to TCP > Sack. About only 3 out of 10 tries, Urel take the same throughput as > Sack. The reason seems to lying in the Delay ACK code, in > tcp_input.c. Because, when we turn off the Delay ACK option, using > sysctl command, Urel and Sack play fairly. However after days of > looking at the code, we failed to find the secret... Therefore, I > turn to you, the specialists of the TCP code in FreeBSD. Hope you > can help us to find the bug of our code. Any suggesion, comments, is > appreciated. > > For details of how the code is implemented, how our experiment is > conducted, you may need to spend one or two hours to browse through > our paper, and the source code. How is this different from the recently integrated SCTP? Best, George