Connectivity and Data Protection
FIGURE 3.7
Reassociation Response frame
There are proprietary methods of managing this “handoff” process
(such as Cisco’s Fast Secure Roaming), and there are industry-standard
methods such as the IEEE 802.11f Recommended Practice. 802.11f
calls for a protocol called the Inter Access Point Protocol (IAPP).
Functionality of this protocol is beyond the scope of this book.
Additionally, wireless LAN switches are becoming prevalent in the
industry. Handoff mechanisms are proprietary and handled internally
in the switch’s firmware.
A station may only be associated with one access point at a time. The
process of authenticating to multiple access points simultaneously is
common and is called preauthentication. Although preauthentication is
specifically allowed by the standard, it has less relevance when used
with the relatively fast Open System authentication.
Consider that, during the roaming process, a situation could arise where
the new access point does not properly notify the old access point of a
mobile station’s reassociation. This lack of notification could be due to
