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Peer to Peer Networking
This page is a simple guide to peer to peer networking, written with beginners in mind. I will explain how to network two computers together. Most information on this page is based on the network that I hooked up in my house.
To configure your computer, follow the instructions in the first section. If you want to be able to share files also, then when you are done with the first section, follow the instructions in the second section also.
The following section will describe how to set up your computer as a client.
The following section will describe how to share files from your computer.
Make a Network Boot Disk
This page describes how to make a bootup disk that will enable you to access a Microsoft Network.
You will need a formatted High Density (1.44 MB) or higher disk.
Connecting two machines to each other
Ethernet has two pairs of wires in a twisted pair setup: one pair for transmit and one for recieve.
When you connect a bunch of machines together using a hub, the hub relays all the information from all the Transmit pairs to all the Receive pairs. That is, each machine sees on its receive pairs the information sent on every machine's Transmit pairs. The hub logically connects all the Transmit pairs to all the Receive pairs. I say "logically" because this represents the information flow. You can't physically connect all these wires together because all the electrical signals would get messed up.
N.B.: If you're trailer-trash, think of it like the thingie you have to put between your truck's turn signals and the trailer wires, so it don't flash too fast. You do got a truck, don't you?Now, if all you want to do is connect your trusty 386 to your friend's Powerbook, then you don't need to deal with all this crap. All you need, assuming both machines have an Ethernet RJ-45 connection, is a cross-over cable. The cross-over cable works only between two machines to connect one's transmit to the other's receive. It's like a hub with only two ports.
A is fairly easy. The hard part is remembering that it's not a conventional ethernet cable.
B isn't hard. Here's the connection diagram:
C is maybe best. You just take two RJ-45 sockets and wire them back to back, crossing over the orange and green pairs. Then you can use conventional, non-cross-over ethernet cables to connect each machine to the cross-over sockets.
Once the machines are connected, you still need to set up TCP/IP addresses, using the methods on the regular wiring page.
Wiring: Color Codes, Terms, and ToolsColor codes and connectors are described below. Here's a glossary of terms and descriptions of some common tools, also.
In the beginning, Ethernet was round and yellow. And really expensive. Cables with twisty little wires were used only by the phone company, the thermostat, and lawn sprinkers. Oh - and AppleTalk.
Ethernet is yet another one of the wonderful things that came from Xerox research, but that Xerox never particularly profited from. You should also thank them for the graphical user interface, the mouse, and the laser printer.
The original Ethernet ran in special coaxial cables (with a center conductor and a shield, like cable TV cables.) Today, that's called "thicknet" and it is virtually non-existent. Next came a cheaper coax called "thinnet" or "10base2". There's still some of this around, but it is rarely used for new installations because it is a total pain to maintain. Instead, Ethernet now nearly always runs over twisted pair cables, just like phone lines, generally called "10baseT", for 10 MHz on twisted pairs, or 100baseT for 100 MHz. Data cables and telephone hookup cables are all data communications cables, and they follow the same or related standards. It also runs on wireless connections using radio signals (Apple's AirPort) or Infrared, and in your house over your existing telephone lines using Intel's Home Network system.
Bandwidth - why wires matterIt started with Morse Code. -- Long and short pulses over a pair of wires that made a clicker clack at the other end. That pair of wires was strung on poles for hundreds of miles, and the clicker at one end just had to make the clacker at the other end clack.
Then came voice. Voice is a fairly low frequency (up to about 3K hertz) signal that is easily carried for fairly long distances by a pair of wires. Phone companies strung billions of pairs of wires, marring the view from almost every window in America, and then hired really smart geeks who realized they could carry more than this one low frequency signal over a pair of wires, so eventually they found ways to multiplex several voice lines onto a single pair of wires. While this saved money and made it economical to keep the rat's nest of wires hanging in the sky, it ultimately limited the bandwidth available on ordinary phone lines to voice frequencies, as higher frequencies couldn't be wedged into the multiplexing system. See "Why My Phone Company Won't Give Me ADSL", later in this web site.
Then came modems. They put digital data onto ordinary voice phone lines by using sounds to represent the 1's and 0's in the data transmission. The earliest modems only did 110 Baud - about 10 characters per second - because that's as fast a teletype machine could print. Later came 300 baud, 1200 baud, 2400 baud, 9600 baud, 28.8 Kbaud, and finally 56 Kbaud. All these modems use sounds within the audible voice spectrum to transmit digital data. The higher data rates are obtained by encoding multiple bits into a single sound, plus using sophisticated digital signal processing to recover the information at the other end. But it's still going over lines designed to only carry voice traffic.
Then came digital transmissions. Digital data can be sent over a pair of wires, but there are some problems to deal with. A digital signal is a step function: an instantaneous rise from one voltage to another. But on a long wire, various electrical effects will cause the step to get stretched out into a more gradual transition. There are also potential problems with reflections: when a pulse goes down a wire and hits the other end, there is a new pulse that bounces back down the wire, just like when a wave hits the wall of a swimming pool. Also, when you transmit digital information down a wire, you lose signal strength as the wire gets longer. You are also susceptible to noise getting into the wire, like from fluorescent lights or motors. All of these effects can make it hard to correctly interpret the 0's and 1's at the receiving end of the line.
To combat these problems in digital transmissions, wiring standards were created. They define the electrical characteristics of the signals transmitted, the data rate and length of the wires that carry the signals, and the electrical characteristics of all the connectors. This doesn't make problems go away, but it makes them predictable, so systems can be tuned for good performance. The standards that are important today are simply called "Category 3" and "Category 5" for 10MBit/second and 100MBit/second data, respectively. These standards define the quality of the wire and its insulation and the number of twists per inch an how different pairs are interleaved. There are also standards for all the interconnections like plugs, jacks, and punchdown panels.
TelephonesPhone wiring in the home generally contains two pairs of wires, for two phone lines. The first pair is green and red; the second is black and yellow. The way you remember this is that there are two holidays: Christmas and Halloween. (I apologize if this is a US-centric mnemonic. I encourage everyone around the world to celebrate Halloween.) This set of colors is standardized for stranded wires (where each "wire" consists of about 20 little tiny wires that hurt like hell if you get one stuck in you.) For solid wires, the color system defined below for Ethernet is used; pairs consist of a colored wire and a white wire with a stripe of the same color. Pair 1 is White/Blue and Blue; pair 2 is White/Orange and Orange. Sometimes home wiring also uses this color scheme, especially if there are more than two pairs.
Telephone wiring also uses a kind of cable called "Silver Satin". This is the relatively flat cable usually used from the wall to the phone itself. This kind of cable should not be used for data, as it does not have the twists in it that are essential to reducing electrical noise that will cause data errors.
Most communications cable today consists of twisted pairs. The twists are put in by thousands of prisoners in China who were laid off when Americans stopped buying tennis shoes with the laces already in them and started putting in their own shoelaces instead. The purpose of the twists is to prevent electrical noise from disrupting the data signals. The two wires are used in a differential mode; that is, the signal is the electrical difference between the two wires. If they are tightly twisted together, then any electrical interference that gets into one wire will also get into the other one, so there is no net difference. This is the secret to reliably high-speed data communications over twisted pairs of wires.
The standard connector for telephone equipment in the US and for data connections everywhere is the modular connector. For voice service, the 4-pin or 6-pin connector, called "RJ-11" is used. For data, an 8-pin version, called "RJ-45" is used.
Note that the connector on the other end
of an RJ-11 connector is wired in reverse order. That is, if
you stretch the cable out flat, the Black wire stays on the left all the way to
the other end, including through the connector with the hook oriented down also.
Also note that the RJ-11 connector has six potential terminals on it. Only the
middle 4 are normally used, and sometimes only the middle two. Line 1 is the
center pair: red and green, as in Christmas.
T-568 4-pair WiringEthernet is generally carried in 8-conductor cables with 8-pin modular plugs and jacks. The connector standard is called "RJ-45", and is just like a standard RJ-11 modular telephone connector, except it is a bit wider to carry more pins.
Eight-conductor data cable contains 4 pairs of wires. Each pair consists of a solid (or predominantly) colored wire and a white wire with a stripe of the same color. The pairs are twisted together. To maintain reliability on Ethernet, you should not untwist them any more than necessary (like about 1 cm). The pairs designated for 10 and 100 Mbit Ethernet are Orange and Green. The other two pairs, Brown and Blue, can be used for a second Ethernet line or for phone connections.
There are two wiring standards for these cables, called "T568A" (also called "EIA") and "T568B" (also called "AT&T" and "258A"). They differ only in connection sequence - that is, which color is on which pin, not in the definition of what electrical signal is on a particular color.
T-568A is supposed to be the standard for new installations, while T-568B is an acceptable alternative. However, most off-the-shelf data equipment and cables seem to be wired to T568B. T568B is also the AT&T standard. In fact, I have never seen anything use T568A. It's important not to mix systems, as both you and your equipment will become hopelessly confused.
Pin Number Designations for T568B
Note that the odd pin numbers are always the
white with stripe color. The wires connect to RJ-45 8-pin connectors as shown
RJ-45 wiring for
Ethernet (T568B standard)
Note that the blue pair is on the center pins;
this pair translates to the red/green pair for ordinary telephone lines, which
is also in the center pair of an RJ-11. (green=wh/blu; red=blu)
Pin Number Designations for T568A
And to end the discussion of wire colors, here's
a translation table from the BRGY used for two-pair lines to the more colorful
combinations used in larger lines:
Straight-Through vs Cross-Over
The only time you cross connections in 10BaseT is when you connect two Ethernet devices directly together without a hub. Then you need a "cross-over" patch cable, which crosses the transmit and receive pairs, the orange and green pairs in normal wiring. See the local networking for more details on doing this, along with some setup info for the sorry excuse for an OS called "windoze".
The primary colors are white, red, black, yellow, violet, and the secondary colors are blue, orange, green, brown, slate, in that order. Pairing runs through all primaries with the first secondary, then all primaries with the next secondary, and so on. (For more than 25 pairs in a cable, 25 pair groups have a loose wrap of nylon thread, where the thread colors follow the same sequence.) Anyway, by this standard, the pairs become:
1) white,blue 2) white,orange 3) white,green 4) white,brown 5) white,slate 6) red,blue 7) red,orange ...and so onNote: An artist friend told me that "slate" is what us Crayola types call "grey". Or is it "gray"? Or is it just Netscape without a colored background?
RS-232This ancient standard is used for basic serial communications between two machines, like a computer and a modem or printer. As I recall, it's what teletype machines used. If you remember paper tape, raise your hand.
RS-232 is a definition of signal names, functions, and voltages. Some systems use an updated standard, called RS-422 instead. For many years it used a standard "D"-shaped connector with many more pins than the protocol needed. Today you see it in little round DIN-8 connectors a lot.
A side-note on those DIN-8 connectors:
Anyway, here's the description of a cable I made to hook up an older router to my Mac. The router needed an RS-232 connection for control, so I had to identify the pins and figure out how to make a cable. For your RS-232ing pleasure, here's the results.
ConnectorsThe significant connectors for Ethernet networks are called "RJ-45" connectors. These are modular connectors, just like the ones used for telephones in the US, but with 8 pins on them.
It is possible to put an RJ-45 connector onto a 4 to 8 conductor cable if you're a masochist. Or if you build ships in bottles for fun. For everyone else I strongly recommend going to your nearest CompUSA, or Fry's if your up to it, and just buy cables with RJ-45s on them off the shelf. I think they make these with machines, as it is almost impossible for a human to get all the wires stuck into the right spot on the connector. I'm a human and I know. If you insist on doing this yourself, get a good crimping tool.
RJ-45 sockets on the other hand are pretty easy. Just make sure you get one that's rated for Cat 3 or Cat 5. If you do, it will have the color codes for the wires (orange, white/or, green, white/gr) marked on it.
I highly recommend the Leviton products for wall mounts. They have faceplates that accept up to 4 different sockets, and they have sockets that snap into the faceplates for RJ-45, RJ-11 (telephone), speakers, cable TV. They aren't expensive relative to the alternatives, and may be available at your local Home Depot.
For some real good advice about bundling and bending the wiring, check out this site: http://www.levitontelcom.com/education/ These guys are pros who have built a very nice reference site. (I'm a bit jealous, but I'll get over it.)
6 Sept 2000