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Chapter 6 Wireless
EMG5324-D10A User’s Guide
116
6.8.5.3 How WPS Works
When two WPS-enabled devices connect, each device must assume a specific role. One device acts
as the registrar (the device that supplies network and security settings) and the other device acts
as the enrollee (the device that receives network and security settings. The registrar creates a
secure EAP (Extensible Authentication Protocol) tunnel and sends the network name (SSID) and the
WPA-PSK or WPA2-PSK pre-shared key to the enrollee. Whether WPA-PSK or WPA2-PSK is used
depends on the standards supported by the devices. If the registrar is already part of a network, it
sends the existing information. If not, it generates the SSID and WPA(2)-PSK randomly.
The following figure shows a WPS-enabled client (installed in a notebook computer) connecting to a
WPS-enabled access point.
Figure 33 How WPS works
The roles of registrar and enrollee last only as long as the WPS setup process is active (two
minutes). The next time you use WPS, a different device can be the registrar if necessary.
The WPS connection process is like a handshake; only two devices participate in each WPS
transaction. If you want to add more devices you should repeat the process with one of the existing
networked devices and the new device.
Note that the access point (AP) is not always the registrar, and the wireless client is not always the
enrollee. All WPS-certified APs can be a registrar, and so can some WPS-enabled wireless clients.
By default, a WPS devices is “unconfigured”. This means that it is not part of an existing network
and can act as either enrollee or registrar (if it supports both functions). If the registrar is
unconfigured, the security settings it transmits to the enrollee are randomly-generated. Once a
WPS-enabled device has connected to another device using WPS, it becomes “configured”. A
configured wireless client can still act as enrollee or registrar in subsequent WPS connections, but a
configured access point can no longer act as enrollee. It will be the registrar in all subsequent WPS
SECURE TUNNEL
SECURITY INFO
WITHIN 2 MINUTES
COMMUNICATION
ACTIVATE
WPS
ACTIVATE
WPS
WPS HANDSHAKE
REGISTRARENROLLEE