Date: Sun, 15 Dec 2002 11:55:45 +1030 From: Greg 'groggy' Lehey <grog@FreeBSD.org> To: Bsd Neophyte <bsdneophyte@yahoo.com> Cc: FreeBSD Questions <questions@FreeBSD.org> Subject: Re: Hubs and switches (was: uninformed qstn...) Message-ID: <20021215012545.GB144@wantadilla.lemis.com> In-Reply-To: <20021214134354.62672.qmail@web20105.mail.yahoo.com> References: <20021214034131.GH503@wantadilla.lemis.com> <20021214134354.62672.qmail@web20105.mail.yahoo.com>
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On Saturday, 14 December 2002 at 5:43:54 -0800, Bsd Neophyte wrote: > > --- Greg 'groggy' Lehey <grog@FreeBSD.org> wrote: >> I've seen little difference. But DON"T BUY A HUB! Buy a switch >> instead. They'll give you better performance, and they hardly cost >> any more. > > i have to be the voice of dissent here... this is not always true. i've > come from the school of thought that states a switch is always better than > a hub. however, there was a CCIE who ran a test to see performance > difference betwene switches and hubs. > > as it turns out fast ethernet hubs edge switches when you are dealing with > a a lower number of systems. generic switches generally rely upon store > and forward and not cut-through, which adds latency some latency. > switches on the other hand do not. however, most times this latency isn't > an issue. I'm not sure you meant to write what you did, but I'm not 100% I understand. But yes, latency isn't an issue. Even if it is, switches still win. I tried a test here between two machines on my network. In each case, the data went via the Cisco 2900 switch and then either via a hub or a second switch. The remote machine has a 10 Mb/s interface. Here are the results (average ping time): Switch, normal ping: 0.756 ms Hub, normal ping: 0.744 ms Switch, 1500 bytes: 4.251 ms Hub, 1500 bytes: 4.004 ms Switch, 1500 bytes, load: 4.244 ms Hub, 1500 bytes, load: 4.513 ms The "load" was a single concurrent tar over the network. I must say I'm impressed how little degradation there was, but it's clear that the latency savings on a hub are more than offset by its performance under load. > again, this holds true for a lower number of machines, such as a > typical home environment, not when dealing with larger networks > where you will start running into collision problems. As I say, there were three machines involved in this test. The collision light was on almost continually: Name Mtu Network Address Ipkts Ierrs Opkts Oerrs Coll rl0 1500 <Link#1> 00:00:21:ca:6e:f1 194268 0 243421 0 44188 The Opkts does not relate to Coll: the system had been up for some time before. Greg -- When replying to this message, please copy the original recipients. If you don't, I may ignore the reply or reply to the original recipients. For more information, see http://www.lemis.com/questions.html See complete headers for address and phone numbers To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-questions" in the body of the message
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