From owner-freebsd-net Fri Oct 12 9: 2:56 2001 Delivered-To: freebsd-net@freebsd.org Received: from smtp1.sentex.ca (smtp1.sentex.ca [199.212.134.4]) by hub.freebsd.org (Postfix) with ESMTP id 99F7737B403 for ; Fri, 12 Oct 2001 09:02:52 -0700 (PDT) Received: from simoeon.sentex.net (pyroxene.sentex.ca [199.212.134.18]) by smtp1.sentex.ca (8.11.6/8.11.6) with ESMTP id f9CG2kd12103; Fri, 12 Oct 2001 12:02:47 -0400 (EDT) (envelope-from mike@sentex.net) Message-Id: <5.1.0.14.0.20011012114959.0717a2a0@marble.sentex.ca> X-Sender: mdtpop@marble.sentex.ca X-Mailer: QUALCOMM Windows Eudora Version 5.1 Date: Fri, 12 Oct 2001 11:56:32 -0400 To: rizzo@aciri.org From: Mike Tancsa Subject: Re: strange results with increased net.inet.ip.intr_queue_maxlen Cc: freebsd-net@FreeBSD.ORG In-Reply-To: <200110120130.f9C1Ubw15419@iguana.aciri.org> References: <200110120116.f9C1GEv18196@arch20m.dellroad.org> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii"; format=flowed Sender: owner-freebsd-net@FreeBSD.ORG Precedence: bulk List-ID: List-Archive: (Web Archive) List-Help: (List Instructions) List-Subscribe: List-Unsubscribe: X-Loop: FreeBSD.org At 06:30 PM 10/11/01 -0700, Luigi Rizzo wrote: > > > from pinging the other side of the OC-3 or ethernet connection and > > > measuring the response time, how can I see how much latency is added by > > > increasing these buffers ? > >of course the latency increase depends on how full are the buffers, >and the worst case is easier to determine by back-of-the-envelope >calculations: > > queue_slots * max_pkt_size / bottleneck_link_speed > >e.g. if you have 100 slots and an MSS of 1500 and a 10Mbit >bottleneck you are adding (100*1500*8 / 10000000) = 120ms latency. Interesting! In my case, one of the machines is oc-3 and ther other, FastE. I guess now it becomes a choice of what is the best choice for my situation which I guess is not so easy to figure out. Is it better to drop packets when the queue is full and let the various applications behind me figure it out, or is it better to add some latency at the network layer so the apps dont have to deal with it. Forgive me if my questions are simplistic, I am just trying to get as much info to make a more informed decision as how to best configure my network given the resources I have. ---Mike To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-net" in the body of the message