802.11h

802.11f

Most wireless networks in small offices and home offices have only a single wireless Access Point. With only one access point, a wireless network is called a Basic Service Set (BSS). For networks that must cover areas larger than a single access point can reach, multiple access points may be connected (via cable) to form an Extended Service Set (ESS). Although the concept of an ESS is part of the original 802.11 specification, certain details of how an ESS operates are lacking.

Key among these are the details of roaming. It is often useful to allow a person to carry a laptop or PDA around in a large building or area served by an ESS without losing a connection to the network when moving from the range of one access point into the range of another. In a manner similar to the familiar cellular phone network, the access points must 'hand off ' a connected user to adjacent access points when a user leaves the range of the first access point.

Roaming requires that the access points present in an ESS communicate with one another. Defining what data the access points must share about roaming clients and how the data is shared are the mission of the 802.11f task group. Eventually, 802.11f will define the IAPP (Inter Access Point Protocol) as a new standard. Many of the higher-end access points support roaming today, but lacking this IAPP standard, manufacturers have had to devise their own roaming machinery, and most such proprietary systems do not work well (or at all) with access points from other vendors. (My own experience has been that roaming is a bleeding-edge feature, and sometimes works strangely even when all access points are from the same vendor.)

If you're going to implement an ESS and support roaming, it's almost mandatory to make your network a single-vendor solution. The 802.11f group is still hard at work, and we're unlikely to see a published standard before mid-2003 or products before the end of 2003.