234 lines
10 KiB
Plaintext
234 lines
10 KiB
Plaintext
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!@#$%^&*!@#$%^&*!@#$%^&*!@#$%^&*!@#$%^&*!@#$%^&*!@#$%^
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@ &
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# General Information on LANs (Topologies, Etc.) *
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$ !
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% An Official THUG Production. @
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^ Written by Laughing Gas For Solsbury Hill BBS. #
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& $
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* (Please keep the name THUGLAN2.TXT where possible) %
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!@#$%^&*!@#$%^&*!@#$%^&*!@#$%^&*!@#$%^&*!@#$%^&*!@#$%^
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Released: 7-31-91
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:: Foreward ::
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Well, in the previous file on LANs, I said that the next one (*this one*) would
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have a complete list of all the programs availible a Novell LAN system, and
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description of each. Well, that was at the end of the school year, and I
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didn't have access to a Novell LAN over the summer. However, I do have a
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LANtastic lan set up here at home.. So I'll probably release a file on that
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soon.. However, since I've been doing work with this LAN, and research and so
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on, I started to write a file about topologies, etc, and since someone else
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mention it on a local BBS, I figured I'd release this file, which is basically
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an introductory guide to topologies and network access methods. This file is
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basically released to the computer underground, however, it might be found more
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interesting by a LAN manager than a hacker. It doesn't really have anything on
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breaking in, or security. Oh well. Here it is. Oh, by the way, when school
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starts up in about a month, I'll get back to the Novell information.
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The basic subjects of this file (as mentioned above) are:
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LAN Topologies
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Network Access Methods
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General Wiring Information
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(I threw in the wiring information, because it doesn't really have anything to
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do with hacking, and neither does the rest of the file.. and it might be
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interesting to anyone interested in the rest of the file..)
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:: LAN Topologies ::
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What is a topology? It's the way a LAN is set up, _physically_.
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Before we get into the different types, you have to know a couple of vocabulary
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terms here.
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Workstation - A Workstation is a single computer on the LAN, which uses the
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LAN's server's resources.
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Server - A Server is a computer on the LAN which allows it's resources (disk
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drives, printers, modems, etc) to be accessed by a workstation. There are a
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couple of basic types of servers:
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Network Server: This is a computer usually with a large hard drive,
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which acts as the main "HUB" of the network, and all
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of the workstations have access to it. The majority
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of shared files are on this machine, and the majority
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of resources are attached to this machine.
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Print Server: This is a machine attached to one or more printers with
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the job of handling all print spooling requests.
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(Although the print queues can often be controlled by a
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superuser from another machine)
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Communications Server: This is the machine or machines with the modem
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or modems in it, and is responsible for handling
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all of the outside communication.
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File Server: This is just a machine with a hard drive dedicated to the
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network.
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Non-dedicated Server: This is a server that is also a workstation. (Ie, you
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can sit down at the server and log into the network..)
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Dedicated Server: This is a server which is dedicated to the network. (You can
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log in FROM it)
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Node - A Node is ANY computer, OR device on the LAN. Any workstation, or
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server is a node, as well as any printer, modem, etc.
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Well, thats about it for terms to know.
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There are three basic LAN topologies. BUS, RING and STAR.
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* BUS
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If a LAN is set up with a BUS topology, there is one long cable, the ends of
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which are NOT connected to ANYTHING. Each Node is connected directly to
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this cable.
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(Check out this lame ascii diagram..)
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Node 1 --- Node 3 ---
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*-----------------------------------------------------------*
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--- Node 2 --- Node 4
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Get the idea?
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A bus topology is a reliable method of setting up a network. If a node on
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the network goes down, all the other nodes can still communicate.
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* RING
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A ring topology is just what it sounds like, the nodes are connected in a
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circular or ring fashion. Node 1 connected to Node 2 connected to Node 3
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connected to node 1 again.
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Lame diagram:
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.-- Node 2 --.
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/ \
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Node 1 Node 3
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\ /
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`-- Node 4 --'
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Got it?
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A ring topology is not usually a good idea. If one node goes down, other nodes
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may not be able to communication with nodes that are connected through the down
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node. In the case above, it's fairly simple, but for arguments sake, if node 1
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went down, node 2 could communicate with node 3, and node 3 could communicate
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with nodes 2 and 4, and node 4 could communicate with node 3, but node 2 and 4
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could not communicate... Well, technically they could, but in a larger network,
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two or more nodes could go down, one on either side of a node, blocking it from
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the other nodes, or if the system was designed to find the shortest path, it
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might find that one of the nodes in that direction was down. Unless it was
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designed to find alternate routes, it might be stuck.
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* STAR
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In a star topology there is a main network server, and each node is wired
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directly to the server.
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Something like this:
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Node 1
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Node 4 -- Server -- Node 2
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Node 3
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A star topology is better than a ring topology, but not as good as a bus
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topology. In a star topology, any one of the nodes could go down, and the rest
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of the lan would still be able to function, but if the server goes down, NONE
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of the rest of the lan would function.
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:: Network Access Methods ::
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There are two major network access methods that I know of, however I suspect
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there are more that I don't know about. (hey, I never said I knew everything.)
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First of all, what is a network access method? It's the method used to send
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data around the network. Network Access Methods are meant to keep data from
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colliding with other data.
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The two major types I know of are Token Ring Passing, and Contention.
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* TOKEN RING PASSING
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Token Ring Passing is used primarily with (you guessed it..) Token Ring
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Networks. Token Ring Networks are usually set up with a ring topology,
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although I would assume that token ring passing could occur not matter what
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your topology.
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When token ring passing is in use, an electronic signal, called a token signal
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is continously sent around the network. When a node wants to send a packet of
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data, it must attach it to this token. The data then rides the token around
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the network until it gets to the node it was intended for.
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* CONTENTION
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Contention is used most often with CSMA/CD (Carrier Sensing Multiple Access
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with Collision Detection) set ups. I like to call it the "waiting" method.
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Basically, a node sends a packet of data out, if another packet of data is at
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the same point, whichever one got there first keeps going, the other one
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bounces back to the node it originated from, waits for a second (well, not
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literally, but just for the tinyest microsecond) then bounces back to see if
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the way is clear.
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:: General Wiring Information ::
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There are three main types of wiring for LANs. Twisted Pair, Coaxial Cable,
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and Fiber Optic wiring.
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Twisted Pair wiring consists of two insulated copper wires twisted around
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each other. It's basically just phone wire. This is a common easy way to set
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up a LAN, also very inexpensive (just buy phone wire..) However, it is the
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least efficent method, and can't handle the load or speed that other types of
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wire can handle.
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Coaxial Wiring or Fiber Optik lines are better, they can hold a larger capacity
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of data, and transmit much faster with no errors. However, these types of wire
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are much more expensive, and often need to be wired into the walls, or floor,
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and that makes them even MORE expensive.
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There is one other way of setting up a LAN, which is what I've done here at
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home... That's using serial or parralell ports, or even modems, to connect the
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computers. In my case, it's not much of a LAN, an IBM XT w/ 40 megs and an IBM
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386SX w/ 80 megs hooked together through the serial ports with a null modem. A
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serial/parralell/modem connection is going to be MUCH MUCH MUCH slower than a
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direct connection. Not only is the data transfered slower, but when you use
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other types of cable, the cable has to connect through a NIC, or Network
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Interface card. Not only does the NIC connect the wires together, but it also
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has the extra power to allow your computer to access the network with no slow
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downs. Of course, this method is much cheaper.. $5 or less for a null modem
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cable, and the price of the LAN software (LANtastic is the only one I know of
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that works with serial/parralell/modem connections, with it's E-Z-LAN software,
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which is what I use..), although that only applies if you pay for the software.
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:: Conclusion ::
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Oh well, not a very underground file... Feel free to distribute it to whomever
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you like.. although I'd apprieciate it if you left it entirely intact, or at
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least left my name on it. Feel free to publish this in any electronic or
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non-electronic form of publication, just leave it intact. If you find any
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errors or whatever, contact me on my board, Solsbury Hill, in the 301 area
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code.
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As the warez dudez say, Greetz to ......
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Elk, and Insight.. You're learning fast..
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Phusionman.. Sorry your friend didn't get served at Maggies (snicker)
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Weapons, TRG, Gentry.. Good to see you again (at Maggies)
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Tuc.. where are you?
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Laughing Gas, 7-31-91.
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