June 01, 2004, 9:13 AM — Today's wireless LAN (WLAN) network infrastructure is constructed from access points (APs), each implemented as a distinct appliance. These are the bridges between the wireless side (primarily mobile computers equipped with Wi-Fi adapters) and the wired side (the rest of the network and IT infrastructure). In the past two years, we've seen an increasing emphasis on moving much (if not all) of the intelligence embodied in APs into elements closer to the core of the network. The best example here is the so-called switched (I prefer the term centralized) wireless LANs. In this model, APs are thin and may in fact be little more than a pure bridge: wireless on one side and wired on the other, all they do is allow mobile users to move data to and from the switch, which functions very much like an Ethernet switch in relation to the rest of the network. Note that WLAN switches also act as controllers, implementing security and other management functions centrally via a box that can also be physically secured.
We can, of course, argue back and forth as to whether more or less intelligence is a good thing in APs. Cisco is the most prominent proponent of fat APs, but is also moving significant functionality into the switch (quite literally into a Catalyst 6500 switch, in fact) and a related management appliance, the Wireless LAN Solution Engine (WLSE). Cisco makes an excellent case for running components of their Internetwork Operating System (IOS) in the AP. I personally think, however, that future APs are likely to be very thin indeed, because we'll need to quite literally deploy millions of them over the next decade or so. These will be installed in both public-access and enterprise networks, and they'll need to be cheap in order to provide some assurance that their buyer's business plans will work.
This brings us to what might be called the ultimate thin AP - one where almost no new hardware is required. Such a creature is available today, in the form of a Soft AP that's little more than an application running on a PC. One still needs the wireless card, of course, but no additional hardware other than the PC is needed. The PC runs software that emulates an AP - hence the term Soft AP. On the one hand, this makes a lot of sense, especially for residential users and ad-hoc, quick-and-dirty, on-the-road APs. Why use a separate AP for light-duty residential access? Many people are already using the Internet-connection-sharing and firewall features in Windows XP, so, indeed, why not? And who wants to carry yet another piece of equipment while on the road?