In non-technical language, ad hoc refers to something created (such as an ad hoc committee) for a temporary period of time and without concern for its broader or more long-lasting implications. In computer networking language, an ad hoc wireless network is put together for a specific and usually temporary purpose, much like any ad hoc gathering.
You start an ad hoc network by enabling a wireless network adapter on one PC, and you add PCs as you like by enabling wireless adapters in each of them and configuring all the adapters to the same wireless channel.
Turn the PCs off, and the network disappears, hence its ad hoc nature. In simpler terms, ad hoc wireless networks have one primary characteristic: They operate without access points (APs).
The lack of an AP means that the computers can connect to one another, but they can’t work in conjunction with a wired network. As a result, they have significantly less capability as a network, but they can still be quite useful.
In particular, they operate well in a small home network or as an independent small network in an office where connecting to the larger network is difficult in certain situations. Think of ad hoc networks as their name suggests—temporary networks created for a specific purpose—and the possibilities multiply.
Ad Hoc Topology
In computer networking terms, each network has a specific topology, or shape. Each computer or other device on the network is a node on that network, and the connections between the nodes are known as links.
The topology describes the manner in which the nodes and the links interconnect. Although numerous topologies are possible, you’ll find the following most frequently:
- Bus: All nodes on the network connect to a single central cable, called a bus (or backbone). The bus handles all traffic to and from the nodes.
- Star: A central computer (hub) controls all network traffic, with nodes communicating with each other through this hub.
- Ring: The network has the shape of a ring or circle, with each node connected to the two nodes on either side. Traffic moves around the ring to its appropriate destination.
- Tree: The core of the network is a bus topology, to which one or more star networks are attached.
- Mesh: All nodes are connected directly to all other nodes. In some meshes, not all interconnections exist, but the principle remains the same.
Ad hoc networks operate with a mesh topology. All PCs on the network connect to each other directly. All appear in the Network Neighborhood or My Network Places folders on each PC, and anyone can send data to—and receive data from—any node at any time.
Looked at another way, ad hoc networks are peer-to-peer networks, so named in computer circles because all nodes are peers, all on the same hierarchical level with one another. No central computer (hub or server) controls the network and the traffic; each machine is as important as the next.
Setup an Ad Hoc Network
Getting an ad hoc network up and running requires three main steps: installing the wireless LAN adapters in your computers, configuring the adapters so they can find and connect to one another, and establishing the network on your PCs so they can share resources.
With all three steps completed, your ad hoc network is ready for use. Before going any further, however, let us warn you that wireless networks, for all their advances over the past few years, can still provide some of the most frustrating moments in computing.
Actually, that statement applies to computer networking in general, which can be filled with problem after problem, but wireless networking seems especially susceptible to difficulties in configuration and sustained connectivity.
Despite the best efforts of Microsoft, the Linux initiative, and all the network equipment vendors, it remains safe to say, as it did ten years ago, that networking is the black hole of computing.
Nor should this come as much of a surprise: given the trouble many people have keeping one computer working properly, it makes sense that getting two or more computers talking to each other is simply asking for problems.
That said, Windows helps, especially Windows XP, the most network-savvy version of Windows yet released. Its Network Setup Wizard, can create a functioning network quickly and, for the most part, reliably. The problem with setting up networks is this: What do you do if it doesn’t work?
And that’s where the frustrations lie. Here’s an example. While writing this, we needed to set up our own ad hoc network and connect the entire thing to the Internet. We don’t usually work with ad hoc networks because infrastructure networks are both more common and more useful.
But we’ve installed and configured numerous ad hoc networks in the past, so this should have been the proverbial piece of cake. Take apart the infrastructure network, install the WLAN adapters in all the PCs, tell everybody where to find each other, and presto. Instant network.
Well, not so much. After many frustrating hours, we discovered that one of the USB adapters was slightly malfunctioning. Slightly, not fully. If something doesn’t work at all, it’s easy to deal with.
But when something almost works, it simply frustrates, because you don’t know where to look. The adapter appeared to be working, so we spent a great deal of time digging through Properties dialog boxes, reconnecting and reconfiguring adapters, and generally rebuilding the entire network structure.
By the time we eventually discovered the true culprit, we had reconfigured everything on all the PCs so completely that we essentially had to start over. Why are we telling you this?
Simply to demonstrate that although setting up a network can be quick, easy, and painless, don’t be surprised, upset, or discouraged if it proves otherwise. Networking problems can happen to anyone, no matter how experienced. Just ask any IT professional.
