From owner-freebsd-isp Fri Jul 11 08:37:21 1997 Return-Path: Received: (from root@localhost) by hub.freebsd.org (8.8.5/8.8.5) id IAA15716 for isp-outgoing; Fri, 11 Jul 1997 08:37:21 -0700 (PDT) Received: from mail.id.net (mail.id.net [199.125.1.6]) by hub.freebsd.org (8.8.5/8.8.5) with ESMTP id IAA15708 for ; Fri, 11 Jul 1997 08:37:18 -0700 (PDT) Received: from server.id.net (server.id.net [199.125.2.20]) by mail.id.net (8.8.6/8.8.6) with ESMTP id LAA21547; Fri, 11 Jul 1997 11:37:31 -0400 (EDT) From: Robert Shady Received: (from rls@localhost) by server.id.net (8.8.5/8.7.3) id LAA22297; Fri, 11 Jul 1997 11:37:26 -0400 (EDT) Message-Id: <199707111537.LAA22297@server.id.net> Subject: Re: T1/T3 Upgrade Options? In-Reply-To: <3.0.32.19970711111025.00c96100@etinc.com> from dennis at "Jul 11, 97 11:10:28 am" To: dennis@etinc.com (dennis) Date: Fri, 11 Jul 1997 11:37:26 -0400 (EDT) Cc: rls@mail.id.net, isp@freebsd.org X-Mailer: ELM [version 2.4ME+ PL31H (25)] MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: owner-isp@freebsd.org X-Loop: FreeBSD.org Precedence: bulk >>> A major factor to consider is that its very difficult to do 86Mbs (T3 is >>> full duplex) with an addon card on the PCI bus because the sustained >>> throughput rate is often pretty low. Other bus masters (ethernets, for >>> example) will futhur reduce the burst capability. While PCI bursts to >>> 128MB/s, very few PC products have sustained throughput rates over 100Mb/s. >>> If you have a 100Mbs ethernet card on the same bus (you'd have to) the >>> number is cut in half. plus bus masters can't be controlled so you have >>> contention issues. >> >> Contention issues I'll agree with for the most part, however.. My >> calculations are (correct me if I'm wrong): >> >> T3 Card = ~12Mbytes/sec [ 90Mbits/sec] >> Ether = ~25Mbytes/sec [100Mbits/sec] >> ============= >> ~37Mbytes/sec >> >> 132 Mbytes/sec - PCI bus >> - 37 Mbytes/sec - Interfaces >> ================ >> 95 Mbytes/sec - Left to play with. > > Because you have no clue how the PCI bus really works (and that burst > rates are not sustainable), your Math is totally invalid. > Remember that ISA is a 64Mb/s medium and if you get 30Mb/s you > are lucky....the numbers are even more dramaticly worse when you add > bursts to the formula as with PCI. Invalid? I doubt it... In "real-life", how often do *MOST* T3 connections "sustain" 45Mbit/sec throughput in each direction? In "real-life", how often do ethernet cards "sustain" 100Mbit/sec throughput in each direction? I think my figures are right on the money, however.. Let's assume for a minute that you can only achieve 50% throughput on the PCI bus for whatever reason.. Assuming that the ethernet and the T3 card were running full tilt (Very, very unlikely in most situations) then with 1 ethernet and 1 T3 port you still have ((132Mbytes/2)-37Mbytes) = 29 Mbytes left over just for lolly-gagging around... > Ah, if life was only as easy as your trivial account of the world! This sounds a little bit sarcastic Dennis... This would *really* encourage me to purchase your products. A "Your a dumb-ass, we're not" attitude. -- Rob === _/_/_/_/_/ _/_/_/_/ _/_/ _/ _/_/_/_/_/ _/_/_/_/_/ _/ _/ _/ _/_/_/ _/ _/ _/ _/_/_/_/ _/ _/_/_/_/_/ _/_/_/_/ _/ _/ _/_/_/_/_/ _/ Innovative Data Services Serving South-Eastern Michigan Internet Service Provider / Hardware Sales / Consulting Services Voice: (810)855-0404 / Fax: (810)855-3268 / Web: http://www.id.net