IAPP, or Inter-Access Point Protocol, is a set of standards designed to make it easier for users to move from one wireless access point to another without losing their connection. The idea of the standards was to overcome the inherent technical barriers that can make it difficult for this to work. IAPP didn't really catch on, though, and is no longer formally recommended.
Aims & Objectives
IAPP is an attempt to make it easier for Wi-Fi users to replicate the way cell phone users access service. When you're on a cell phone call, you can move about with your phone and it will automatically switch to the nearest available cell phone tower, even in the middle of a call, without loss of service. IAPP is designed for Layer 2 setups, meaning switching between different access points that are ultimately part of the same network. The problem here is not in the user's device finding and switching to the nearest access point. Instead the problem is how to make sure the network keeps track when the user switches from point to point, such that the network can keep a continuous flow of data through the various access points between the user and the Internet.
IAPP works in a relatively simple way. When the user's device connects to a new access point (for example, when the user changes physical location), the access point broadcasts two pieces of information across the network, somewhat like sending out a memo. The first piece of information identifies the user's device and allows the network to know where the device is. The second piece of information identifies the access point and allows the network to know how to route data to reach the user's device. These "memos" are timestamped so the network knows that each new set of information overrides the previous instructions.
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IAPP is formally known as IEEE 802.11F and is a set of optional add-on rules to IEEE 802.11, which is the basic framework of Wi-Fi. In 2003, the IEEE published IAPP as a recommendation for trial use. In practice, though, IAPP didn't do enough to deal with the problems of keeping track of a device moving between access points that used equipment from different manufacturers. It also didn't do enough to address the security issues related to such a setup, or the problem of maintaining fast data connections. In 2006, the IEEE withdrew its recommendation, meaning it's no longer a part of the official Wi-Fi standards.
In some circumstances, references to "IAPP" and networking may not relate directly to Inter-Access Point Protocol. Instead the speaker or writer may be referring to the International Association of Privacy Professionals. While this IAPP deals with the entire field of information and privacy, it does occasionally publish reports or host presentations that relate to the implications for privacy of particular types of networking, including Wi-Fi setups.