On Fri, 19 Apr 2002 23:54:49 -0500 Timm Murray <hardburn at runbox.com> writes:
> If it seems like they are always receiving data, that is because > they are. > Below is a quick introduction to how networking works. > > There are two layers we are concerned with here: (1) Physical and > (2) Data > Link (there are five others in the most common networking model > (OSI), but > these are the important ones for our discussion). > > The Physical layer is basicaly a wire (or fiber or radio waves or > whatever) > and the bits that travel over it. Nothing particularly > inteligent--it just > provides a way to make electrons (or photons) from one place to > another. > Repeaters and hubs are layer 1 devices, as well. This part is done > purely in > hardware (usually). > > The Data Link layer creates some logical orginization to a network. > You have > some sort of address (for Ethernet, this is a MAC address), but no Hehe, if not for my class at school I would have thought you were talking about Apple Macintosh and my head would be spinning in confusion. :) But, I know what you mean. :) Our system is setup to take the MAChine addresses (ie 17204a) and give them IP addresses and such through DHCP. Very nice of it to do that. :) Yesterday I had to put my removable lab hard drive in a different computer than I was useing when I installed win98, winnt4, and win2kpro so it bombed, sort of, because a computer with that exact address was already on the network. So I said "forget this" and I named my machine "Krepta" on all three OSes, cause I KNOW no other machine will EVER have that address. :) > actual > routing takes place. The addresses are just there to provide some > way to > make each computer unique on the network. NICs, bridges, and > switches are > layer 2 devices. This part is partialy done in software, but is > done mostly > in hardware. Ah, ok. :) > > So why are your computer's constantly receiving data? Well, think > of the > situation where you need to run Ethernet beyond it's 100 meter > limit. You > get a repeater (a layer 1 device), which has the sole job of taking > the > signal in one end, strengthening it, and spewing it out the other > end. The > two end points on the system might as well be on the same wire. Makes sense, all broadcast systems use signal repeaters to keep the signals from degrading too much. > > To get a hub, you basically stick a bunch of repeaters together; in > other > words, hubs are just multiport repeaters. So, all computers > connected to a > hub might as well be connected to a single wire. Yeah. That makes sense too. :) > > Now you ask "since they are all on the same 'wire', what happens > when two > machines try to talk at once?" Answer: You get a collision. In a > collision, the signal is destroyed bit-by-bit. All devices on that > "wire" > notice this and stop sending data for a random ammount of time and > then start > resending. In general, the more devices you have on that hub (or > "collision > domain"), the more likely collisions will happen, thus reducing your > total > throughput (because the collisions stop everyone from sending > stuff). So thats why the network sometimes just goes down, or parts of it anyway. Signal collisions!!! Jeeze. :( > > (To the gurus: Yes, I know I'm ignoring Token Ring networks. > Nobody cares > about Token Ring anymore, so just shut up :) Is Token Ring better? If so, why aren't people useing it? > > Taking our example further, let's say you have two hubs that you > want to > connect together. You are worried, however, that this will make > your > collision domain much too large. No problem, just use a bridge. A > bridge, > being a layer two device, knows something about the addresses being > used on > each side. If machine A sends something to machine B, and they are > both on > the same hub, the bridge knows that it shouldn't forward the traffic > onto the > second hub. Thus, the bridge has split your collision domain, > otherwise > known as "segmenting". Ah yes, switches, thats what I was trying to think about to reduce traffic over all the lines. > > Remeber how hubs are really just multiport repeaters? What happens > when you > create a multiport bridge? You get a switch. Switches basicaly > saved > Ethernet, because without them, collision domains can quickly get > too large > to handle. Yes, I see, very very good idea to use bridges(switches). > > Like a bridge, a switch will remember what MAC addresses are on each > port, and > are thus able to make forwarding decisions. Switches are usually > more > expensive than hubs, and create slightly higher latenices (since What is a latinice? Do you mean Latency? I've noticed that word being used on Network Games like X-wing Vs. Tie Fighter, but I didn't know what it meant, other than signal speed or something. > they > actually have to do some work), but throughput is increased to > near-maximum > for each switch port. How about hooking in some kind of RAM that can be used as a buffer inside a switch so that it will forward the data when a machine is ready to recieve it? > > The usual network configuration is to use hubs on the workstations, > then > connect those hubs into switches (servers are often, but not always, > directly > connected to switches). If the orginization can afford it, it will > get the > Nirvana of Networking . . . that is, having a network which has no > hubs at > all. This is called a "microsegmented" network. Yahoooo!!!! I would love to hook up a massive network of nothing but switches, no hubs!!! But it still seems to me like there would be WAY too many "Shared Resources" on a serverless network, even a "microsegmented" one, to be any real use to any large organization. I would still really like to put Freenet nodes into every PC to make the entire network act like one massive server. Of course, a serverless network might still need to be created in a kind of higharchy or something. Hmmm. :( Would DHCP automatic IP addressing be able to work on a "microsegmented" network just like on a HUB network? > > There is probably a lot more information up there then you really > wanted to > know, but I hope I answered your question somewhere in there :) Oh don't say that, I want to know as much as possible, thats why I'm in the "Computer Networking and Information Technology" program at High Tech Institute. :) ________________________________________________________________ GET INTERNET ACCESS FROM JUNO! Juno offers FREE or PREMIUM Internet access for less! Join Juno today! For your FREE software, visit: http://dl.www.juno.com/get/web/. _______________________________________________ Chat mailing list Chat at freenetproject.org http://lists.freenetproject.org/mailman/listinfo/chat
