Call the Cable Guy: Wireless just won't cut it

Corporate types need to rethink

Poster for the movie Cable Guy. Copyright:  Columbia Pictures Corporation,

Wireless networking is regarded by many as the way to go for corporate networking. No need for expensive structured cabling, no need to re-patch stuff when someone moves desk, and sufficiently secure to make it suitable for corporate use.

I am inclined to agree with that last point: rank up the encryption to WPA2-AES and use 802.1x for admission control and you'll do OK. As for the rest... it's just tosh. Wireless sucks for general networking.

Those of us old enough to remember Ethernet before the switch was invented will be familiar with how a shared-media Ethernet LAN degraded as you connected more and more devices. And for those who aren't old enough to remember: performance dropped like an anvil thrown off a skyscraper.

This was nothing to be surprised about: in a shared-media setup the devices have to deal with the possibility of two endpoints trying to talk at once (a "collision").

I remember running PERFORM3 in the test lab of the publications I wrote for in the 1990s and watching with awe as throughput vanished down the toilet more and more as I introduced more endpoints. Wireless networking is a shared-media network. So if you connect more and more machines, it's going to run appallingly – just like Ethernet used to.

Oh, and wireless networks run in unlicensed frequency bands. That means bands that aren't assigned to one specific company in a region, but instead are available to be shared by many.

As one reference puts it: "unlicensed operation typically needs to be tolerant of interference from other devices"; and we're not just talking about other Wi-Fi networks. Ever fired up the ancient office microwave and watched what happens to the wireless LAN?

That's because the 2.4GHz band is used by loads of stuff including microwave ovens and traditional Wi-Fi networks (802.11b and 802.11g, plus many 802.11n and 802.11ac LANs). (Incidentally, if ever there was a good reason to select the 5GHz option on your wireless kit, that is it.)

Then there's the cost. Yes, you can pick up the access point devices pretty cheaply, but that's just part of the battle. In a corporate network you need the ability to roam seamlessly around the building, with the network happily handing off connectivity as you move between coverage areas. This generally means using "thin" access points and a pair of central controllers (you'll want a pair for resilience, of course).

Something like a Cisco 2504 will cost you around £1,700 per unit if you have 15 access points or fewer. Not bank-breaking, but add more access points and ramp up the licence and you'll be spending real money (£5,300, say, for a device that can run 50 access points).

Finally, before we start talking about bits of network string, let's mention one last thing about wireless networking: although it looks easy, it isn't. Anyone who's ever sat in a classroom learning about wireless LANs (I did Cisco's Implementing Cisco Unified Wireless Networking Essentials a few years back, for instance) will have come out with their head spinning – it's a pretty complex area and aside from knowing how things work and how to configure them, you also need to be conscious of how to place your access points to ensure coverage within the building but minimise leakage out of the walls and windows. Again, not trivial.

We've established that there are some drawbacks with wireless, then. But aren't there some problems with cabled networking too?

Yes, of course there are – the main ones being cost and inconvenience. LAN switches cost money and decent LAN switches cost quite a lot of money.

Structured cabling also does not come cheap; flood-wiring even a medium-sized office can cost you a hefty five-figure sum. And once you've paid for the cabling and the kit, you then have the faff of re-patching stuff when people change desks (nobody with any sense will go to the expense of having enough LAN ports to patch every floor port, after all).

However, the benefits vastly outweigh these drawbacks.

The main advantage is the obvious one: if you have a Gigabit network, each endpoint gets 1Gbit/s of bandwidth. The network is no longer the bottleneck – if you have device A talking to device B while device C talks to device D, both pairs of endpoints will get the full network speed, as there's no need for collision detection or avoidance in a switched network.

An increasingly big deal these days is the security of cabled networks. Even if you've designed your wireless network very well, you're unlikely to completely avoid leakage through walls and windows. If you use shared-key authentication at all (which is common for guest wireless networks), you'll need to be sure to change the key frequently or, preferably, use a hotel-style system whereby visitors get a one-time key that's valid only for the time they're with you.

(And if you think "Oh, that's obvious, of course I'll change the key frequently": my phone still connects to a local company's guest Wi-Fi when I'm driving past, using the key I entered several years ago). With a cabled network, people have to get into the building physically to connect up, you can shut down unused switch ports, and you still have admission control functionality available should you want to be doubly sure that a device appearing on a port is legitimate and welcome.

And having said all of this, if you still try to argue that wireless is the way to go, answer me this: if you love wireless so much, why not fit 802.11ac adaptors in all your servers the next time your data centre LAN kit is due for replacement?

Don't get me wrong, wireless networking is great ... but only where its advantages are actually advantages. When you're sitting at your desk, a bit of wire is your friend: it gives your computer high-speed access to your data and applications. Where you're wandering around the building with your smartphone, tablet or laptop, the wireless network is fantastic because it gives you mobility at the times when you don't need super-fast performance.

But remember: the reason the wireless LAN is usable when you're bashing on your laptop in a meeting room is that most of your colleagues are sitting at their desks throwing electrons down bits of wire. ®


Biting the hand that feeds IT © 1998–2017