Date: Tue, 30 Apr 1996 01:02:16 -0600 From: russ@ism.net (Russ Pagenkopf) To: Thomas J Balfe <tbalfe@tioga.com>, freebsd-hardware@FreeBSD.org Subject: Re: ethernet question Message-ID: <v01530500adab33e0445c@[205.199.12.48]>
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At 10:51 AM 4/30/96, Thomas J Balfe wrote: >At what point do you need switched ethernet in terms of nodes? This is >the situation, a building with 7 floors, 40 units per floor, each with >one 10baseT port in it. Would two or three switched ports per floor be a >smart option? I'm not exactly certain that this belongs here, but what the heck... :-) This isn't an easy question to answer as there are a number of questions that need to be answered so consider this qualified and a general outline. The first thing to remember about networking is that there are no hard and fast rules. Every situation is unique and should be evaluated as such. When I'm evaluating a site for setting up an initial network the first thing I look for are natural "zones" in a site. These zones may be seperate buildings, individual floors, concrete firewalls that break up a building horizontally, or even individual rooms (but don't let this list limit your imagination). Next evaluate your users; are they high-bandwidth (graphics intensive), medium-bandwidth (some graphics but some text) or low-bandwidth (mainly text). This will help determine your actual needs (vs. wants :). Evaluate potential growth. Are there only four people on a floor that might hold 20? Or have you filled the space? What about bandwidth needs? In a month, year or three years? Answering some these questions will help you lay out the groundwork for your networking. Next backbones. Remember the "zones" mentioned above? Those zones help define where to put hubs (and maybe routers) and how to link them. In these days of growing bandwidth needs I always take a serious look at running fiber or 100baseT between the hubs/routers to form a backbone. This backbone must be very carfully placed. One, to allow for further expansion. Two, to minimize or eliminate the possibility of either inadvertant (oops, so that's what that wire's for) or intentional (gee, we're tearing out that wall now) breakage. Taking one user down is a whole lot less traumatic then cutting the accounting department off from the main server on payday. :-) Next, equipment choices. Twisted pair or coax? Do I use hubs or routers? Do I switch or not? Fiber or copper? Each of these is very dependent on the above. Here's my general thinking though. Twisted pair or coax? For me the choice is almost always TP. Why? Never give a user the chance to take down your network if you can avoid it. With twisted pair they can nuke themselves. With coax they can nuke everyone. Think about it. Coax does have its uses, but very seldom will I recomend it. Hubs vs. routers. Never use a router where a hub will do. Routers are more expensive (generally) and easier to screw up (probably). Unless the client has someone on staff who has a clue or they're contracting out to someone who does, hubs are simply safer. BUT, routers do have their place. One, you really need to segregate a group and keep their high-bandwidth traffic within their subnet or... Two, you need one for security (minimal firewalling) (if you want a real firewall, go get one. *that* is not the place to scrimp). Switch or no? First question, do you *really* need it? Switching hubs are much more expensive and unless you really need it, you may be spending money in the wrong place. Switching hubs do have their place though and you should not hesitate to use one if the need is there as they can make a tremendous difference. Fiber or copper? Fiber is wonderful. Fiber is sexy. Fiber *is* EXPENSIVE :-). Everything about fiber is more expensive than copper except upgrading when you realize you've run out of bandwidth on your copper plant :-(. The difference in bandwidth possibilities between fiber and copper should make the decision easier if you need it now or think you will in the future. Besides, the penny pinchers I've met like it when you say, "Gee, it'll be X to install it now, or X*10 later because we'll have to tear out the walls later." Last, but most certainly not least, get and use SNMP equipment. The ability to monitor traffic statistics alone will more than justify the cost (besides making it easier to get more money when you need it :). The ability to track and pinpoint problems will make you look like Scotty (ah captain, but my wee 'bairns) (pardon ;). >Additionally, what are people's recommendations in terms of equipment? Hoo boy, religious war coming. Get and use what you're comfortable with. Personally I prefer 3Com, but use the tool that fits the job, it'll make life simpler later. >Also, is Ora TCP/IP the best place to learn more about arp? Sorry, can't answer that. rus Russ Pagenkopf (russ@ism.net) Join the revolution! <http://www.ism.net/~russ/dic.html>;
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