Most of the discussion in this blog centers on what is called infrastructure mode wireless networking. In this mode, for example, an access point transmits and receives signals from wireless clients in much the same way that a network hub can accept Ethernet cables being plugged into its open ports.

Infrastructure networks force users to authenticate themselves and impose other restrictions to limit who can connect to a network, as well as provide fast direction for packets bound to one system or another. Also, when a wireless device such as an access point fails, most infrastructure networks lose their coverage for that particular area.

Depending upon your purpose, there are different types of community networks to consider:

• An ad hoc network for fast client-based peer-to-peer networking.
• A portal WLAN with authentication, management, and restrictions to specific content.
• An extended WLAN with users who have managed domain accounts.
• A hotspot or an open WLAN where anyone who can receive the signal can connect.

All of these different types of networks can serve as network neighborhoods, and each is useful in specific types of situations. Let’s take a look at when you might want to use each one.

Ad Hoc Wireless Networks

For situations where there are transitory communities that need to wirelessly network, such as a class or lab session, a convention hall, or some such thing, users can create a wireless network in the ad hoc mode using their network cards as nodes in a temporary network.

Ad hoc networking, sometimes called peer-to-peer networking, shares the same wireless bandwidth and only requires that a user connect up to the open network, usually without any authentication. When one user streams a large multimedia file over an ad hoc network the impact is felt by all users, as the bandwidth is used up.

Ad hoc networks aren’t meant to be performance champions; they are meant to provide substantial ease of use to the users. Peer-to-peer networks is what Windows for Workgroups offered in the early 1990s, and is made available to developers for Windows as a Microsoft SDK (software development kit).

The peer-to-peer model was probably made famous to everyone by the now defunct music sharing software Napster. You can find numerous examples of peer-to-peer networking applications that you can use on your own ad hoc network including LANster, Grokster, Blubster, BearShare, a variety of applications that run on a Gnutella network, and others.

If you want to set up an ad hoc network that provides Internet access to users, you can set up a mode on nearly all access points called “ad hoc” and that will allow connections.

You might use an ad hoc network when you have a group of family members come to your house to swap digital picture albums, or to create a picture album from everybody’s photos for a commemorative CD-ROM for your grandparents’ fiftieth wedding anniversary.

With everyone connected, you might share your My Pictures folder, allowing each person in the group to access and edit that folder, adding their photos as required.

If you had thousands of pictures, you might want to let everyone view the photos of interest and add them to the final photo folder. An ad hoc wireless network would work well for this situation.

To set up an ad hoc network, do the following:

1. Check that you are all using the same networking standard: 802.11a, b, or g.
2. Have your clients set their network adapters to the ad hoc mode and set the network SSID to the same value.
3. Set all client adapters to the same channel.
4. Disable WEP for easier connection.
5. Save these settings as a specific network connection in case you want to apply them sometime in the future.
6. Setup your network shares.
7. Make sure that everyone has their personal firewalls either turned off or set to allow certain kinds of file sharing.

Once your settings are correct, joining an ad hoc network means just showing up; your wireless NIC should connect automatically. You’ll find instances where establishing an ad hoc network doesn’t work.

Sometimes this problem is hardware related; ad hoc networking is part of the 802.11 standard but few manufacturers test their cards for compatibility. More often you will find that there is some problem with the IP address.

We recommend that you use static IP addresses for small ad hoc networks, so you want to make sure that the correct address ranges are assigned and that there are no IP address duplicate pair (address conflicts). If you are using DHCP for an address provider, you should check to see that your DHCP service has actually given out a valid IP address.