Introduction to Wireless Networking

On October 26, 2005, in How-To, by David Cohen


In my previous article, I gave you an overview of Ethernet networking from the point of view of cabled connections, and a discussion of the basics of network protocols and addressing.

Cabled connections are all well and good, but in the home setting they are rarely overly useful. Broadband connections will terminate at their point of entry to your home – typically the main phone jack or your cable modem box, where as most people will want their Macintosh in a study, kitchen or bedroom. You can run long cables round your house if you like, but unless cabling is built into the walls like an office this is not an attractive solution.

The rise of wireless networking is a perfect solution to this dilemma, and recognizing this, Apple was one of the earliest adopters of the technology right across the Macintosh range. They branded the technology Airport, and made it available as an option on all machines – though nowadays, the vast majority of the range come with it as standard.


So is it magic?

It’s not quite magic, but the first time you sit with a laptop on your sofa or in the garden browsing the Internet, you might think it is! What makes wireless a bit confusing is there is a lot of jargon and acronyms, which is why Apple have applied simple names to the topic.

The basic principle behind wireless networking uses a radio to send digital signals between two points. The radio operates at the 2.4GHz microwave frequency, which is far away from audio radio frequencies. However, 2.4GHz is a frequency that is open for general use, so you may have other wireless devices that will interfere with your wireless network signal – more on that later.

The original standard that was widely adopted became known by the engineering number applied to the standard – 802.11b. Snappy, eh? They also created the term Wi-Fi, but this has become an umbrella term for the whole technology, and doesn’t define the various types of wireless. 802.11b is what Apple adopted as Airport, and it is characterized by a maximum speed of 11Mbit per second and a maximum range of around 150 feet.

Now, these statistics are theoretical maximums – in practice, you will get less speed and range. This is because in the real world, building construction will soak up some of the signal, and other devices such as microwave ovens and cordless phones will interfere. The 802.11b standard is designed to cope with this, and is good at maintaining a connection, but the radio gymnastics all reduce the overall throughput – 5Mbit per second average is typical.

That’s good enough for sharing a Broadband connection (even the fastest rarely exceed that figure), but it is not so good for streaming video or audio, and large file transfers will take a while.

As such, a faster standard was duly defined and ratified as 802.11g. This is backwardly compatible with 802.11b, but operates at a maximum of 54Mbit per second. This is the standard that Apple is currently using, and is dubbed Airport Extreme on the Macintosh. Airport Extreme is more interference and structure resistant than the slower Airport, due to the higher speed, and you will typically get around 20 Mbit per second on the throughput. Video and audio streaming works well, while still leaving enough bandwidth to browse the Internet or copy files at the same time.

These are the main standards in use today. There is a competing high-speed standard (802.11a) that has not been widely adopted as it is incompatible with Wi-Fi, and also a wireless Broadband standard known as Wi-Max (802.11n) that is in its infancy at present. However, for the Mac Airport and Airport Extreme are where it is at.


Sounds good – where do I sign up?

OK, so how do you get talking over wireless? Well, you are going to need some gear first. Obviously, a wireless device is required for your Macintosh – either an internal card or some sort of external device.

All Macintoshes currently on the market will take an internal Airport Extreme card, and with the latest round of updates virtually every model include one as standard. Most older Macs from the last five years will have a slot for either an Airport or Airport Extreme card. Original Airport cards are not available from Apple anymore, though of course Airport Extreme cards are. Either can be fitted by a dealer or an Apple Store Genius Bar. Failing that, look to eBay for older Airport cards. If you have a laptop with a PC Card slot, then many common PC Card wireless cards have OS X drivers (I use a Cisco Aironet 350 in my TiBook), or for desktops, try a USB wireless adapter (Belkin has an OS X compatible device).

You will also need a Wireless Router – these are the wireless equivalent of an Ethernet hub or switch, and will link a cabled network to a wireless network. In the home, you will use this to share your Broadband connection wirelessly, and allow different wireless computers to see each other. Apple makes two wireless routers, the Airport Extreme Base Station and the Airport Express. The Airport Extreme Base is a conventional wireless router, and the Airport Express is a smaller device that can also receive and play iTunes music wirelessly. Both have a USB port to allow you to share a printer wirelessly as well. Airport Express is a particularly cool piece of kit that I will focus on specifically in a future article.

Like all things Apple, Airport equipment is fairly expensive, and cheaper equipment might perform better. However, for the money you do get guaranteed Macintosh compatibility and the best design. I recommend using Apple Airport equipment if you can – because the Airport software integrates so well with OS X, and so you should have fewer problems with Airport gear. However, there is one caveat about that – those cool metal cases that PowerBooks and Power Macs wear are very good at blocking 2.4Ghz signals, so you might want to use an external device if you think you will be at the edge of the range envelope.


Don’t steal my bandwidth!

The security (or lack thereof) of wireless networks has received a lot of coverage in the media over the last two years. This has been sensationalized to the point that “urban wi-fi guerrillas” armed with Linux laptops and coffee can antennas are painted as being on every street corner, looking to steal your hard-earned bandwidth!

The simple fact is that wireless networks were never that insecure – it’s just that a lot of companies never turned the security on! While it’s true that the first Wi-Fi security standard can be breached, you have to be a fairly hard-core hacker to do it, and you have to work quite hard at it – it takes time, patience and luck to breach a single wireless access point.

As such, a few basic precautions will render a wireless network relatively secure from casual breaches – and this is a good thing. While I admire the ideal of deliberately leaving a wireless network open for the passer-by, in practice free Broadband access runs a high risk of being abused by users of peer-to-peer networks like BitTorrent. You might have plenty of download bandwidth to share, but your upload bandwidth will be considerably less. If your upload pipe is congested by outgoing P2P traffic, your Internet experience will begin to resemble dial-up!

Fiercely, users should change the user name and password used to administer their wireless router, to something personal to them. This will prevent anyone reconfiguring your router to allow themselves access.

Next, the wireless router should be set so that it has a unique identifier (known as the SSID), and configured so that this SSID is not broadcast to all. Too many wireless routers are left as they come from the factory – there is one near my office that regularly is picked up by my laptop, and appears as LINKSYS on my desktop every day!

Finally, a level of access control should be applied to the wireless connections. The wireless router can be configured with the MAC addresses of your wireless devices, and it will only accept connections from those devices. This will stop anyone else from using your wireless connection.

What about encryption? There are two standards of encryption that can be used for wireless links – Wired Equivalent Privacy (WEP) and Wi-Fi Protected Access (WPA). WEP is the one that can be breached by the determined, though it takes a few days of packet sniffing and a powerful computer to do it. WPA is the gold standard in encryption nowadays.

However, in the home I don’t recommend encryption – it reduces range and throughput, and it can be the source of real problems when troubleshooting connections. My advice is stick with a hidden SSID and MAC filtering – if anyone manages to overcome that and get access to your network, they probably deserve free access as a reward for effort!

My next article will discuss the nuts and bolts of setting up an Airport network, together with how you can use an Airport Express to wirelessly send music and extend your network’s range.

 

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