There was a time when home networks were the province of the irredeemably nerdy, but in these days of enlightenment (or at least, since the new PC arrived and the old one was given to the kids) the possession of more than one computer in the home has become commonplace.

Of course, this raises immediate problems regarding Internet access. The arguments over long phone calls with boyfriend/girlfriend pale into insignificance compared with the ructions which can be caused by huge Internet phone bills and who gets to use the phone line at any one time.

The simple solution is a home network. Today's technological advances mean it's not difficult to set up, and it's also fairly cheap. If you want to be able to use the Internet from two machines at once in your house, read on.

Warning: this article uses technical terms. Definitions are listed at the bottom, but for a more comprehensive reference you could try Imperial College's Free Online Dictionary Of Computing. The products and technologies discussed here are widely available at surprisingly low prices from high street computer specialists. This is not rocket science.

The Basics

In the old days, PC users could use a serial cable and a piece of software called LapLink to connect two computers. With Windows 95, it became possible to use a serial or parallel cable and no additional software. Mac users never needed any software; the Mac has supported networking using its Appletalk feature from a very early stage, and a printer cable was usually all that was required.

These days, however, this is not generally adequate. File sizes are much bigger, and people are less prepared to wait. So the starting point is generally an Ethernet connection. This gives you several benefits including:

• Internet connection sharing
• File sharing
• Printer sharing
• Ability to back up all computers onto a tape installed in one computer

Ethernet

Ethernet has been around for some time now, so is well supported by almost every operating system and computer, unless it's really very old.

Twisted Pair Cable

The most common form of Ethernet these days is 10baseT, which carries data over unshielded twisted pair (UTP) cables, generally referred to as Category 5, or Cat 5 for short. Category 3 is all that's required for most installations, but the cost and inconvenience of cabling is such that few people bother, and most put in the higher-specification cabling which is more future-proof.

The advantage of using twisted pair is that it's very widely available, it will carry other traffic (eg, ISDN) and network cards are extraordinarily cheap. The downside is that you almost invariably need a hub (see below). Although you can use a crossover cable to connect two computers, if you want to add another computer or device you must have a hub, so you might as well plan for it at the start.

Coaxial Cable

Another fairly common form of Ethernet is 10base2, or thin Ethernet (also thinnet). This is a coaxial cable somewhat thinner than that used for TV aerials, with a bayonet connector (BNC) crimped on to the end. To attach this to a card you need a T-piece and a terminator. Although connecting straight to the BNC connector on the network card might work, it's fairly unlikely, and the specification calls for the additional bits.

The big advantage of thinnet is its simplicity. It requires no hubs - you just start with a terminator at one end of the cable, connect as many PCs as you like along its length, and finish with a terminator at the other end. Easy. The downsides are that the cable is relatively expensive, you can't use 100 megabit (which is probably irrelevant in a home context), the cable is more susceptible to damage, you need terminators and T pieces, and the cards are slightly less common. This sounds like a big deal, but in practice thinnet is still very cheap and easy enough for the complete novice to use.

Wireless Ethernet

Wireless Ethernet has been around for some time, but used to be prohibitively expensive for home use. Recently, though, wireless networking solutions like Apple's AirDock have become more affordable. Although bandwidth is lower than wired Ethernet (typically 11Mbps or less) this is, as has been discussed elsewhere, not generally an issue in a home setting. Cabling is an issue, however, and the fact that wireless Ethernet requires no cabling, as its name suggests, must make it a strong contender where budgets permit.

What You Need

Let's assume you've decided that Ethernet is the most practical and cost-effective solution. Each computer that is going to be connected to your network needs to have Ethernet hardware. There are a few things you need to check before buying an Ethernet card:

• Have you already got on-board Ethernet? Most newer Macs and some PCs have Ethernet built into the motherboard. Older Macs need a thing called a transceiver to connect to the proprietary (AAUI) socket; later ones have a standard RJ45 socket.

• Have you got a spare expansion slot, and if so what type? New PCs and Macs usually have PCI slots, older PCs will have larger ISA, MCA or EISA slots, and older Macs may have either an LC expansion slot, or a NuBus slot. If in doubt, take the computer to a proper computer shop and have them specify the card required.

• Are the computers within the specified cable run length¹?. Unless you have an unusually large house, you'll be okay here - 100m for twisted pair, 200m for thinnet.

• Which type of cable will you use? You might start with thinnet, but preserve your options for later upgrade to twisted pair, in which case you buy a tri-media card (not actually that much dearer, but rarely supports 100 Mbit/s).

• Does your operating system support the type of card? Make sure the card comes with drivers certified by Microsoft (or Apple, or whoever) for your operating system. If you're still running Windows 3.x, this is particularly important.

Choosing and Laying Cable

Thinnet is a very easy option: it's trivial to lay down, and simple to maintain. Give serious consideration to using this if you have a small number of devices - say, two or three computers - and are unlikely to add complicated things like routers (ADSL or ISDN). It's marginally less versatile than UTP, but definitely still a good choice for most home users.

If, on the other hand, you are already considering things like multi-user ADSL, networked games (which have notoriously high bandwidth requirements) or you already have RJ-45 sockets on your computers, then 10baseT or 100baseTX is for you (for all intents and purposes, the cabling is the same for both).

Measure the distances the cables must run, and take account of obstacles, furniture, etc. No cable likes being run under carpets and walked over, but you can tuck it down the edge of a carpet to get it out of sight. Surface trunking (which sticks on the wall) is commonly used, but ugly. If you have suspended wooden floors you are lucky - a small hole and the cable is out of sight.

The hardest part is getting cables long enough to run between rooms or floors. Check your local specialist computer shop and see if they'll make them up specially. One 50m Cat 5 certified cable is probably all you'll need to connect to the bedroom upstairs; other devices will be clustered around the hub so you can use shorter, standard patch cables.

Finally, decide whether or not to buy a hub. The general guideline here is that if you use twisted pair, you should almost certainly buy one. You can get away with a crossover cable, but then you can't add any additional devices to your network. (Make sure your hub speed matches the speed of your network!) If you don't buy a hub, remember to get your special long cable made up as a crossover - and remember that it won't work with a hub if you buy one later: crossover cables are for directly connecting two computers together, but hubs-computer connections require the non-crossover type.

Structured Cabling

Some modern houses have structured cabling fitted, like in offices, and some people actually install this in older houses as well. Structured cabling is a system where RJ45 wall sockets are placed around the house, and cabled behind the walls to a patch panel (an array of sockets to connect everything together), commonly using Cat 5 or Cat 6 cable. This cabling will carry Ethernet, telephone, ISDN and various other sorts of traffic.

There are a couple of desirable advantages to structured cabling: you can connect a phone or computer almost anywhere in the house, and you can plug your PC into the wall and connect the associated port on the patch panel into the hub, so your hubs and other bulky equipment can be placed conveniently out of sight under the stairs. The downside is that it's fairly expensive (budget around £300 for an average house, plus the cost of hiring a cable tester), it requires special tools, and it's disruptive while the work's being carried out.

Installing network cards

Installing network cards is usually simple. Newer operating systems (and virtually all Macs) offer 'plug-and-play' detection of new hardware. Plug the card in, and the drivers install themselves². For non-plug-and-play operating systems, you will need to follow the manufacturer's instructions with the card and install the drivers (usually from a floppy disk).

Before you start, ensure that your card will be protected against static discharge, which can permanently damage the electronics. Get an anti-static wrist-strap and connect it to the metal chassis of the PC. Leave the PC plugged into the mains, as the earth pin grounds the chassis and reduces the risk of a spark grounding through the equipment, but ensure that the PC is switched off before opening the lid or inserting cards or you risk mains electrocution, which can kill you instantly.

Some PC manufacturers will try to persuade you that you will invalidate the warranty if you open the case of a PC. This is almost certainly legally unenforceable, as adding a component is a normal part of owning a PC, but if you have a fairly new PC or one with an extended warranty, then it makes sense to contact the manufacturer and probably buy the network card from them.

And if the idea of opening the lid of your cherished piece of technology sounds daunting, most decent PC shops will fit network cards for you. This has the additional advantage that if they supply and fit the card, they are responsible if it doesn't work, which can save hours of argument later.

Using Your New Network

So, you've installed the network cards, plugged them into the cabling (and maybe the hub), and turned the PC on. It will probably work straight off, but if it doesn't, check that the green lights on the network cards are on. Most network cards and hubs have a green LED which lights up when a connection is correctly made. If the lights are out, try swapping the cables. Note that on a tri-media card, the green light is commonly attached only to the UTP interface, so if you're using BNC you will probably not have a connection light even if the card has one fitted.

The precise details of troubleshooting network connections are well beyond the scope of this discussion, but suffice it to say that normally it does work the first time.

IP Addresses

Every computer connected to the Internet has a unique Internet Protocol (IP) address. You may have bought a unique (or 'persistent') IP address, but what usually happens is that your Internet Service Provider (ISP) will assign one to you when you dial up to connect. In order for your computers to talk to one other, they will need unique addresses of their own. You will need to use the networking controls to assign addresses (and more importantly, you need to assign addresses which won't cause problems!).

First, if you buy something like an ISDN router to connect to the Net, it will usually do this for you automatically using something called Dynamic Host Configuration Protocol (DHCP). If not, then you need to choose one of the 'private' IP address ranges. The most common is probably 192.168.0.x (where x is any number from 1 to 254, or more accurately 0 to 255, but 0 and 255 have special meaning, and so are not used), so your computers could have the addresses 192.168.0.1, 192.168.0.2, 192.168.0.3 and so on. The subnet mask to use would be 255.255.255.0. A discussion of exactly why is well beyond the scope of this discussion, but it's all to do with binary arithmetic.

So, how do you share the Internet connection? One way is to use Windows' Internet Connection Sharing, set up through the dial-up networking control. Another is to get a thing called a proxy server which will manage your network connections for you. Both will use something called Network Address Translation (NAT) to manage the traffic from several internal IP addresses to one external address, assigned by your ISP. If you have a router, it will probably do the same.

Alternatively, if you don't mind getting your hands slightly dirtier, and you have a spare PC with a couple of network cards³, it is possible to create your own network router using GNU/Linux. When properly configured, this can be used to assign internal addresses to your home network using DHCP, connect to your ISP automatically when required, and act as a firewall, proxy server and cache, all for free.

One way or another, one device (router or computer) will connect to the Internet and provides services to the others. One good reason for using a proxy server is that it can cache some traffic and reduce connection times; it also allows you to define the access levels for individual members of your household. Most proxy server software includes some basic content filtering.

Safety First!

Whatever you do, it is very strongly advised that you have firewall software on your PCs if they are connected to the Internet to stop people or viruses from gaining illegal access and control of your computers.

Glossary