Wireless networking

Overview

What is it? Durr, it's networking without wires. It works by sending data over radio waves, rather than through cables.

It seems to be all the rage at the moment. Wireless networking allows us to be more mobile. It allows us to easily connect to a network on an ad-hoc basis, with minimal configuration.

Ad-hoc mode

We see examples of wireless networking wherever we go... Supermarkets allow shoppers to roam around with wireless devices, scanning their own items. Fast food chains are now beginning to use handheld devices on wireless LANs to capture customer orders. All very dull.

To me, the major benefit is to get your money's worth out of broadband providers. Alternatively, this is known as screwing them. Imagine that you live in a house divided into several flats. Most of those flats have their own broadband connection via a dedicated cable. That's what it's like where I live. Completely pointless. Instead of every flat owner paying their monthly subscription, I have a better idea:

Why not have one fat link (say a 1MB connection) in one flat only. That connection would go into a wireless router. That router can be connected to by any nearby PC with a wireless network card. So all my neighbours could connect to my network with wireless. Now we all get a fast connection with only one broadband subscription. I know many people who've done this. Be warned: it may not, strictly, be legal! You may also want to check your security settings since you don't want casual passers by to be able to join your network.

How do you set one up?

The simplest way is ad-hoc mode, shown above. This is a peer-to-peer network in which each machine is connected by virtue of its wireless network interface card (NIC).

A more complicated approach, called infrastructure mode, makes use of a wireless access point which acts like a hub and connects the wireless devices to the wired network. It is also possible to buy wireless routers and other wireless network hardware.

Wireless networking using an access point

Some basic definitions

The original and most prolific standard of wireless network out there today is the one called 802.11b. This is a standard that defines a wireless network using a wireless frequency of 2.4GHz and running at up to 11Mbit/sec. By the way, this is the same frequency that's used by microwave ovens and cordless phones, so interference is sometimes an issue!

Next comes 802.11a. (Stupid, innit?) These networks operate at 5GHz and are thus incompatible with 802.11b devices (although dual-band equipment is available.) The major advantage is the speed, which can reach 54Mbit/sec.

Most recent is 802.11g. This operates at the same speed as 802.11a, but has the additional advantage of being backwards compatible with 802.11b devices, since it too runs at 2.4GHz.

Another term you might here a lot of is Wi-Fi. This pun on hi-fi originally stood for Wireless Fidelity. The Wi-Fi alliance has undertaken the job certifying wireless hardware. Hardware that is Wi-Fi certified is, in theory, guaranteed to run with other Wi-Fi hardware (of the same type, such as 802.11b). This takes much the pain away from choosing your hardware.

Security considerations

As I mentioned early, security considerations are more important in wireless LANs than they are in conventional ones. Why? Because with a fixed wire-based LAN, only people who are physically attached to the LAN have access to your network. This is a major security restriction in itself. However, with a wireless network, all you need to gain access is to have a wireless network card and be within a certain distance of a wireless access point. In the early days, hackers exploited this weakness by sitting in retail car parks. They would sit there picking up credit card numbers flying over the retailer's wireless network.

One way to protect your wireless network is to enable WEP (Wired Equivalent Privacy) which encrypts data at the Data Link/Physical layer of the TCP/IP stack. However, WEP is not very difficult to hack, so will only deter casual hackers. A better way is set up your wireless devices to use MAC-address based packet filtering, so that only 'friendly' devices are allowed on to the network. However, this method can also be fooled, in a process known as packet spoofing. However, the combination of dynamic WEP and MAC-addressed based filtering should be enough for most purposes.