User's Manual

110 Operation
Chapter 4 - System Configuration
 Key Caching: WPA2 provides fast roaming for authenticated clients by
retaining keys and other security information in a cache, so that if a client
roams away from an access point and then returns, re-authentication is not
required. When a WPA2 client is first authenticated, it receives a Pairwise
Master Key (PMK) that is used to generate other keys for unicast data
encryption. This key and other client information form a Security Association
that the access point names and holds in a cache.
 Preauthentication: Each time a client roams to another access point it has to
be fully re-authenticated. This authentication process is time consuming and
can disrupt applications running over the network. WPA2 includes a
mechanism, known as pre-authentication, that allows clients to roam to a new
access point and be quickly associated. The first time a client is authenticated
to a wireless network it has to be fully authenticated. When the client is about
to roam to another access point in the network, the access point sends
pre-authentication messages to the new access point that include the client’s
security association information. Then when the client sends an association
request to the new access point, the client is known to be already
authenticated, so it proceeds directly to key exchange and association.
To configure WPA, click Security, select one of the VAP interfaces by clicking
More. Select one of the WPA options in the Authentication Setup table, and then
configure the parameters displayed beneath the table.