From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mailout-de.gmx.net (mailout-de.gmx.net [213.165.64.22]) by huchra.bufferbloat.net (Postfix) with SMTP id 7CEC920191A for ; Sun, 8 May 2011 05:55:09 -0700 (PDT) Received: (qmail invoked by alias); 08 May 2011 13:01:00 -0000 Received: from unknown (EHLO srichardlxp2) [213.143.107.142] by mail.gmx.net (mp040) with SMTP; 08 May 2011 15:01:00 +0200 X-Authenticated: #20720068 X-Provags-ID: V01U2FsdGVkX1//2gs/W6T/woaFZKDz65WF4+Iz3t/t+43SdrKSDR ykH9UXByv7FLt4 Message-ID: From: "Richard Scheffenegger" To: "Fred Baker" , "richard" References: <4DB70FDA.6000507@mti-systems.com><4DC2C9D2.8040703@freedesktop.org><1EA9A6B3-F1D0-435C-8029-43756D53D8FD@gmail.com><1304694852.29492.16.camel@amd.pacdat.net> Date: Sun, 8 May 2011 15:00:32 +0200 MIME-Version: 1.0 Content-Type: text/plain; format=flowed; charset="iso-8859-1"; reply-type=original Content-Transfer-Encoding: 7bit X-Priority: 3 X-MSMail-Priority: Normal X-Mailer: Microsoft Outlook Express 6.00.2900.5931 X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2900.6090 X-Y-GMX-Trusted: 0 Cc: bloat@lists.bufferbloat.net Subject: Re: [Bloat] Goodput fraction w/ AQM vs bufferbloat 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: Sun, 08 May 2011 12:55:10 -0000 Note that this will only give you a lower bound; the true losses that were addressed by the sender (ie. RTO retransmissions that got lost again) can by principle not be discovered by a receiver side trace, only a (reliable) sender side trace will allow that. To the second point: Only for simple Reno/NewReno there exists a closed formular for estimating throughput based on random, non-markow distributed losses; and more modern congestion control / loss recovery scheme will permit (more or less slightly) higher thoughput, thus the formulas (ie. RFC 3448 states the one for Reno) will only serve as a (good) lower bound estimate. Again, increasing throughput at the cost of goodput is a bad proposition, if you get charged by traffic volume (because what you really want is data delivered to the receiver, not dumped into the network for no good reason). Regards, Richard ----- Original Message ----- From: "Fred Baker" To: "richard" Cc: Sent: Friday, May 06, 2011 11:56 PM Subject: Re: [Bloat] Goodput fraction w/ AQM vs bufferbloat > > On May 6, 2011, at 8:14 AM, richard wrote: >> If every packet takes two attempts then the ratio will be 1/2 - 1 unit >> of googput for two units of throughput (at least up to the choke-point). >> This is worst-case, so the ratio is likely to be something better than >> that 3/4, 5/6, 99/100 ??? > > I have a suggestion. turn on tcpdump on your laptop. Download a web page > with lots of imagines, such as a google images web page, and then download > a humongous file. Scan through the output file for SACK messages; that > will give you the places where the receiver (you) saw losses and tried to > recover from them. > >> Putting a number to this will also help those of us trying to get ISPs >> to understand that their Usage Based Bilking (UBB) won't address the >> real problem which is hidden in this ratio. The fact is, the choke point >> for much of this is the home router/firewall - and so that 1/2 ratio >> tells me the consumer is getting hosed for a technical problem. > > I think you need to do some research there. A TCP session with 1% loss > (your ratio being 1/100) has difficulty maintaining throughput; usual TCP > loss rates are on the order of tenths to hundredths of a percent. > _______________________________________________ > Bloat mailing list > Bloat@lists.bufferbloat.net > https://lists.bufferbloat.net/listinfo/bloat