How to... get started with a basic WLAN for SMEs

Wireless networking is, in its most basic form, not a difficult concept to master. Although enterprise-level installations will need to consider signal coverage, roaming between locations, subnetting for traffic minimisation and so on, the main issues for the average SME installation revolve around: "What kit do I need?" and "How do I connect it all up?". In fact, these are two questions that I've been asked twice in the last week.

What kit do I need?
In order for your computers to talk wirelessly to your network, you need a couple of basic things. First, you'll need a Wireless Access Point (AP), which is the gizmo that sits between the radio waves and the cabled network. Second, you'll need wireless adaptors for each of the workstations you're going to use wirelessly. Note that you probably don't want to have your servers connected using wireless – they don't move and since they're a concentration point for the traffic there's a danger they wouild eat all the bandwidth. For stuff that's easy to connect with cables, stick with cables.

The most basic AP is a simple wireless-to-Ethernet box, which has an antenna on one side and a 10/100M bit/s Ethernet connector the other. Think of it like an Ethernet hub with an uplink port – the uplink port connects to the switch "above" it in the network, but instead of having a bunch of ports on the front, they're invisible radio channels. Something like the NetGear HE102 (54Mbit/sec IEEE802.11a), ME102 (802.11b) or WG603 (802.11b/g) would be examples here. Incidentally, if you have anything but the smallest installation, you will probably go with 802.11g, as it runs at 54Mbit/sec, while 802.11b is restricted to 11Mbit/sec. If your workstations are not going to be used on other wireless networks, such as public hotspots, consider 802.11a, which is just as fast but operates on a different wavelength to the 802.11b in use at hotspots. Dual-purpose devices that do both "a" and "g", are worth thinking about but will cost you a bit more.

Many people buying wireless kit for new installations also have wide-area links to think about. If you're a cable modem or DSL user, it's also possible to get a combined AP and router, which talks to your PCs over the airwaves and links directly into the broadband port. NetGear's options are the DG834G and DG824M, though there are plenty of manufacturers (D-Link, for instance) with similarly-priced equivalents.

On the other side of the equation, you'll need a wireless adaptor in each of your workstations in order for them to talk to the AP. Because the standards are just that – standards – you don't have to have the same brand of AP and adaptor but it often helps to do so. The diagnostic capabilities of the associated software may be a bit better if you have just one vendor's kit. Some, such as NetGear and D-Link, offer proprietary speed boosts if you stick to one vendor.

The key consideration is that your PC adaptors need to be compatible with the AP you're going to buy – 802.11b adaptors won't work with an 802.11a AP, for instance, though they probably will be happy to talk to an 802.11g AP.

How do I connect it all up?
Assuming you have an Ethernet-connected AP, it connects to your network just as if it were a workstation, via an Ethernet cable into the hub or switch. Don't do something daft like connecting it to a 10 Mbit/s port, because you're killing the performance (why bother with 54 Mbit/s wireless if you're constricting it down 10 Mbit/s bits of wire) – make sure you have a 100 Mbit/s switch between your AP and your server(s).

To connect things up, that's all you need to do. But there are a few things to do before you can get going. First, you need to set the WEP key on the AP. The more advanced APS may be available - the shortcomings of WEP are well known - but its security is good enough to keep out casual hackers. WEP is the basic, generic way of securing wireles LANs.

There'll be a configuration tool on a CD with the AP, so run it up and select a hard-to-guess key. It is crucial that the session key is not a dictionary word or other easily guessable string. The SSID, or "service name" that you ask for, is for human-readability and has no technical bearing, so just call it something sensible. Although you can work without WEP, you really shouldn't do so – it's insecure to work without it and WEP is so easy to set up.

Once you've set up the AP, you need to tell the workstations the WEP key – so they can authenticate to the AP and communicate securely. You'll generally find that modern operating systems such as Windows XP will automatically prompt you to enter the WEP key the first time you connect to the WLAN, in which case you can simply enter the key and you're away. If you're not prompted, check the WLAN adaptor's icon in the taskbar – you'll find that alongside basic stuff like a signal strength meter there's a little utility that lets you define the WEP key for your network. Most modern adaptors' associated software has the ability to remember a number of WEP keys for a number of different SSIDs (so if you have a WLAN at each of two offices, you don't have to keep changing the WEP key on your laptop), but if you only have a single office you don't care about that.

Keeping an eye out
This is all you need to do to get a basic WLAN up and running. Once it's all set up, the main thing you need to do is keep an eye on the loading of the network, because as you add more workstations the average performance will tend to drop. There are remedies to this, such as adding more APs or considering moving static users to cable-connected links, but the best way is to spot performance degradation before it becomes an issue.

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