Path: utzoo!utgpu!news-server.csri.toronto.edu!rpi!zaphod.mps.ohio-state.edu!mips!spool.mu.edu!snorkelwacker.mit.edu!stanford.edu!leland.Stanford.EDU!Panther.Stanford.EDU!morgan From: morgan@Panther.Stanford.EDU (RL "Bob" Morgan) Newsgroups: comp.dcom.lans Subject: Re: 10Base-T hubs Message-ID: <1991Apr10.035143.15862@leland.Stanford.EDU> Date: 10 Apr 91 03:51:43 GMT References: <1582@vtserf.cc.vt.edu> <1991Apr9.181721.15560@leland.Stanford.EDU> Sender: news@leland.Stanford.EDU (Mr News) Distribution: usa Organization: Networking Systems, Stanford University Lines: 61 > Perhaps I'm being too stupid here, but why do you need a repeater > for an 8-station network? Why not hook them all up to the same > cable? Well, if you've been reading comp.dcom.lans, the benefits of structured wiring have been explained at length. But this is indeed just the sort of question that those of us who install these things for a living have to answer on a daily basis. You're right, it isn't obvious. So here are the answers in easy-to-understand terms. 1. I didn't say so in my previous note, but the main point of putting in a network around here (and at almost any large institution these days, I'll bet) isn't to hook the machines to themselves, it's to hook them to the campus net (that is, to the Internet). So your proposed single run of thinnet has to connect to the building backbone in any case, which means a repeater. I'll admit I can't explain it, but I can get a 12-port 10Base-T repeater these days for about the same price as a traditional 2-port AUI-only repeater. 2. Where are these 8 stations anyway? As I said before, if they're in one room, sure, use thinnet. But if, as is the usual case, they're scattered around the floor of your medium-to-large building, then the "single cable" ends up hopping from room to room, crossing the hall, going around the corner, and doubling back to catch the one at the end of the hall. Maybe you're lucky and it's still only 450 feet. Then they get two more computers in two different offices (and yes, they *always* get more computers eventually). Someone looks up in the ceiling and finds where the cable runs kind of near the one office, cuts it and adds a loop. The other one is sort of near the end of the daisy-chain, so they just add to the end. How long is the cable now? Where are its connectors that will fail over time? Who bought the new cable that was spliced in, and why didn't they notice that it was 53 ohms, not 50 (they're lucky it wasn't 75)? So eventually the thing breaks down, and after weeks of cursing and head-scratching, they call in the network guys, who look around, shake their heads, and say: what you should do is buy a MPR and install some home runs to it. That way you'll have a manageable cable plant that is relatively immune to the weird things that people do to nets, and that provides an obvious growth path for future installers. 3. If those 8 stations are typical office PCs these days, they're probably worth a total of $20,000 or so. If they're fancy Unix boxes, the total may be over $100,000. If the people using them are getting paid for their time, the total may be a couple of hundred dollars an hour (of course, if they're just grad students ... 8^). Isn't it worth spending a extra few hundred dollars, adding at most 3 or 4 percent to the total cost of this networked computer system, to make the network as reliable as it can possibly be? So, the point is: no matter whether you're installing thinnet or twisted-pair or fishing line, it's almost always worth it to install a structured wiring plant. And once you've decided to do that, *if* you can use your existing structured telephone cable plant, then 10Base-T is cheaper by a long shot. No hype. - RL "Bob" Morgan Networking Systems Stanford