Way back in the 1970s and early 1980s, it was rare enough to have a computer in the home, classroom, or office. Today it's not at all uncommon to have several computers in the workplace, school, or home.

Back then, networking wasn't an issue. Today, it's something everyone with two or more computers should know about. At the very least, it can be a way to share an Internet connection when you have more than one computer.

Ethernet

Networking protocols and wiring types have come and gone, but the most common type of network these days is ethernet using 8-strand cable. Ethernet of this type comes in three speeds: 10Base-T, 100Base-T, and Gigabit. 10Base-T operates at 10 megabits per second, 100Base-T at 100, and Gigabit at (you guessed it) 1000.

Up through the mid-1990s, 10Base-T was the norm, but since the late-90s 100Base-T has become dominant. Gigabit ethernet is usually found on servers and other high-end machines.

In an ideal world, all the computers on your network would use the same flavor of ethernet, but if you have some newer computers and some older ones, that may not be the case. Fortunately 100Base-T is generally backwards compatible with 10Base-T - it just slows itself down to match.

Hubs

The simplest hardware for connecting three or more devices together (computers, networked printers, cable modems, etc.) is with a hub. Hubs come in several sizes, from small 4-port units to 24-port and beyond monstrosities rarely found outside of big institutions.

What a regular hub does is receive information from any device on the network and transmit it to all the other devices. It doesn't know or care which device the data is going to; it's up to each piece of hardware connected to the hub to know whether it wants to use or ignore the data stream.

Most hubs can handle a mix of 10Base-T and 100Base-T devices automatically, although there are some older computers (especially older Macs with AAUI ethernet connectors) that don't work well on 10/100 hubs or switches. (I learned that the hard way in my IS days....) If you run into this problem, the best solution is two hubs - one for general use and another, connected to the first, specifically for the 10Base-T machines.

The more old 10Base-T hardware on the network, the messier that gets.

Switches

If you've just got a few devices, a regular hub is fine, but as you add more and increase the amount of information being moved over the network, you may approach the saturation point. To avoid that, engineers invented switches, which are intelligent hubs that know which device each data packet is headed for and make sure that the information only follows the path to that machine.

The busier the network, the more helpful switching becomes. There's probably no need to have a 4-port switch, but at the 8-port level and beyond, it can be helpful.

Routers

A router is a device that sits between one network and another, such as a device that sits between a cable modem connected to the Internet and a hub that's part of your local area network (LAN).

Beyond simply connecting two networks, routers can have additional functions such as allowing multiple computers to access the Internet by translating their local network address to one that works on the Internet (NAT, Network Address Translation), assigning network addresses to local machines (using DHCP), and blocking certain ports or types of information from entering or leaving your network (a firewall).

Most of the routers on the market today perform all of these functions.

Simple Networking

You can buy routers with multiple ports, which also makes them hubs. And in some cases these are switched ports, making the router a switch. A lot of routers today will let you connect a modem (cable, DSL, or dialup) as well as 2-4 other devices. If you've only got a few computers, one router and several runs of cable could be all you need to share your Internet connection with each computer.

Wireless Networking

A nice twist on this is wireless networking, which came to prominence when Apple introduced AirPort on the first iBook laptop in July 1999. AirPort uses the 802.11b protocol and is about the same speed as 10Base-T ethernet. Although rated to 100 meters (330'), walls and interference from 2.4 GHz cordless phones generally reduces that distance by at least half.

Another interesting aspect of wireless is that throughput varies with distance. Close to the hub, you'll achieve maximum throughput, which is generally under 5 Mbps in the real world. Further away, the data rate can drop as low as 1 Mbps.

Still, it's plenty of reach in most homes and small offices, so a centrally located 802.11b router can let you connect laptop and desktop computers without the need to run wires. And for sharing an Internet connection, which usually tops out at under 3 Mbps, 802.11b is fast enough.

Of course, if you also want to share files on your local network, the speed of 802.11b is pretty anemic. Two new protocols, 802.11a and 802.11g, have come into existence to address that. Both offer networking speeds of up to 54 Mbps, almost five times the speed of 802.11b.

802.11a was designed to avoid the interference from cordless phones and microwaves. It uses the 5 GHz spectrum, which also cuts its range to about half that of 802.11b. Cnet estimates the maximum data rate for 802.11a in the real world "should be around 22-26 Mbps."

And because higher frequency signals are more attenuated by obstacles, 802.11a range will be reduced more by wall and partitions than the lower frequency 802.11b and 802.11g signals.

802.11g is just coming into its own. It is backwards compatible with 802.11b, so people with AirPort, WaveLAN, and other wireless cards can still use their older equipment on the new network, although they won't see an boost in throughput.

Like 802.11a, real world throughput is estimated at roughly 24 Mbps. And like 802.11b, 802.11g is rated to 100 m (330') indoors and 400 m (1,300') outdoors.

The following is adapted from a table on the Buffalo Technology website and represents ideal throughput. Real world results may be less:

Speed	Outdoors	Indoors
54 Mbps	165'/50 m	6'/20 m
18 Mbps	490'/150 m	195'/60 m
11 Mbps	590'/180 m	245'/75 m
1 Mbps	1870'/570 m	410'/125 m

For the most part, 802.11g routers include 4 ethernet ports (sometimes switched ones) for your local devices plus an additional port for connecting a cable or DSL modem and sell for US$150 or so. This makes the router useful for both wired and wireless devices. 802.11g PCI cards for desktops and PC Cards for portables are generally available for under US$100.

Complex Networks

There's really nothing terribly complex about complex networks - they just have more hubs. It's very easy to daisy-chain ethernet hubs, and hubs and switches often have one high speed port especially for connecting one to another.

Why build a complex network? The most obvious reason is that you've outgrown your current hub and would rather add a second one than replace the whole thing. Another reason, noted above, is to keep 10Base-T traffic off a 100Base-T hub, because the older devices are sometime problematic with 10/100 hardware.

Another reason is wiring. Rather than run a few more (or a lot more) wires from your main networking center to a location, you can use a single cable, connect it to a hub in the second location, and network devices in that area to the nearby hub. Considering the cost of running wire, this can be a very economical solution.

You should never have more than five hubs between any two devices on your network. Except for the biggest, most complex networks, that's not likely to happen, but if you do end up with several hubs, the best approach is to wire them to a single central hub when possible.

However, ethernet is rated to 100 meters (330'), and if you need to go beyond that, you'll want a hub to act as a repeater between your central hub and the distant one. In a really really large building, it's conceivable that you could have a need to have hubs two steps removed from the network center.

Connecting Hubs

Many ethernet hubs have a special port, called an uplink port, that's used for connecting one hub to another. The uplink port (sometimes marked LAN) has some pins in different locations and eliminates the need to have a crossover cable between hubs. When connecting hubs, make sure only one of the two is using a LAN port.

If neither of your hubs has a LAN port or you've already used the link ports, you will need to run a crossover cable between your hubs.

Note that on some hubs, especially smaller and less expensive ones, one of the regular ports may do double duty as a link port. In this case there will be two ports that share the same port number, and one will usually be marked link or LAN. Although there are two plugs, these two connections are a single port, and you should never plug devices into both connectors on a LAN port.

The new 802.11g wireless networking equipment can also be used as a bridge to share a wireless network in multiple locations. By deploying several 802.11g access points throughout a building, coverage can be improved without the need to run wires between the wireless hubs.

Simple Internet Sharing

All of this may be overkill if all you want to do is share a simple Internet connection between two computers. Windows Internet Connection Sharing has been available since Windows 98SE. For just two users, you don't really need a hub or router. You do need an ethernet port on each computer, and NICs (Network Interface Cards) are cheap, and a crossover cable between them.

Beyond two computers, you will want a hub, but small hubs are also cheap these days.

Conclusion

There's really nothing mysterious about networking computers. For the most part, it's just plug-and-play. You'll generally be able to program a router using a browser by copying the cable/DSL modem settings from your personal computer to the router. From there on, you'll be transparently sharing files and printers locally while also accessing the Internet as necessary.