Brocade Mobility 5181 Access Point Product Reference Guide (Supporting software release 4.4.0.0) - Manual (Page 34)

20 Brocade Mobility 5181 Access Point Product Reference Guide
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Theory of operations
1
An Client can roam within a coverage area by switching Mobility 5181 Access Points. Roaming
occurs when:
• Unassociated Client attempts to associate or reassociate with an available Mobility 5181
Access Point
• Supported rate changes or the Client finds a better transmit rate with another Mobility 5181
Access Point
• RSSI (received signal strength indicator) of a potential Mobility 5181 Access Point exceeds the
current Mobility 5181 Access Point
• Ratio of good-transmitted packets to attempted-transmitted packets falls below a threshold.
An Client selects the best available Mobility 5181 Access Point and adjusts itself to the Mobility
5181 Access Point direct-sequence channel to begin association. Once associated, the Mobility
5181 Access Point begins forwarding frames addressed to the target Client. Each frame contains
fields for the current direct-sequence channel. The Client uses these fields to resynchronize to the
Mobility 5181 Access Point.
The scanning and association process continues for active Clients. This process allows the Clients
to find new Mobility 5181 Access Points and discard out-of-range or deactivated Mobility 5181
Access Points. By testing the airwaves, the Clients can choose the best network connection
available.
Operating modes
The Mobility 5181 Access Point can operate in a couple of configurations.
• Access Point - As an Access Point, the Mobility 5181 Access Point functions as a layer 2 bridge.
The wired uplink can operate as a trunk and support multiple VLANs. Up to 16 WLANs can be
defined and mapped to Mobility 5181 Access Point XX WLANs. Each WLAN can be configured
to be broadcast by one or both Mobility 5181 Access Point radios. A Mobility 5181 Access Point
can operate in both an Access Point mode and Wireless Gateway/Router mode simultaneously.
The network architecture and access point configuration define how the Access Point and
Wireless Gateway/Router mode are negotiated.
• Wireless Gateway/Router - If operating as a Wireless Gateway/Router, the access point
functions as a router between two layer 2 networks: the WAN uplink (the ethernet port) and the
Wireless side. The following options are available providing a solution for single-cell
deployment:
• PPPoE - The WAN interface can terminate a PPPoE connection, thus enabling the Mobility
5181 Access Point to operate in conjunction with a DSL or Cable modem to provide WAN
connectivity.
• NAT - (Network Address Translation) on the Wireless interface. Using NAT, the Mobility
5181 Access Point router is able to manage a private IP scheme. NAT allows translation of
private addresses to the WAN IP address.
• DHCP - On the wireless and LAN side, the Mobility 5181 Access Point can assign private IP
addresses.
• Firewall - A Firewall protects against a number of known attacks.