ing, or worse, obtaining a new Internet protocol (IP) address; ideally, data transfers could 5.1.3.1 802.11 Architecture continue seamlessly as the user moved. A distribution system is assigned responsibility for keeping track of The 802.11 standard allows both infrastructure net- which stations are in which BSSs and routing their works, which are connected to a wired network (typically packets appropriately. However, the original and en- Ethernet) using an access point, and independent net- hanced 802.11 standards did not specify how such works connecting peer computers wirelessly with no roaming ought to be conducted; only with the release wired network present. Most installations are of the in- of the 802.11f Inter-Access Point Protocol (IAPP) frastructure variety, and we focus on them. From the standard in 2003 did the operation of the distribution point of view of the Ethernet network, which is usually system receive a nonproprietary specification. The connected to both ends of an 802.11 link, the wireless IAPP protocol uses the nearly universal internet pro- link is just another way of moving an Ethernet packet, tocol (TCP/IP) combined with RADIUS servers to formally known as a frame (Figure 5.1-2), from one sta- provide secure communication between access points, tion to another (Figure 5.1-3). SO that moving clients can reassociate and expect to However, the possibility (well, likelihood) that some receive forwarded packets from the distribution or most wireless stations are mobile stations means that system. In the future, local roaming on 802.11 net- the architecture of a wired Ethernet network with works should be (hopefully) transparent to the user, if wireless stations is likely to be fundamentally different compliant access points and network configurations from a conventional wired network. The stations asso- become widely established. ciated to a particular access point constitute a basic service set (BSS). The collection of BSSs connected to a single wired 5.1.3.2 MAC and CSMA/CA network forms an