Foundry Networks IronPoint 200, Installation Manual

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Network Planning
April 2007 © 2007 Foundry Networks, Inc. 3-3
Infrastructure Wireless LAN for Roaming Wireless PCs
The Basic Service Set (BSS) defines the communications domain for each access point and its
associated wireless clients. The BSS ID is a 48-bit binary number based on the access point’s
wireless MAC address, and is set automatically and transparently as clients associate with the
access point. The BSS ID is used in frames sent between the access point and its clients to identify
traffic in the service area.
The BSS ID is only set by the access point, never by its clients. The clients only need to set the
Service Set Identifier (SSID) that identifies the service set provided by one or more access points.
The SSID can be manually configured by the clients, can be detected in an access point’s beacon, or
can be obtained by querying for the identity of the nearest access point. For clients that do not need
to roam, set the SSID for the wireless card to that used by the access point to which you want to
connect.
A wireless infrastructure can also support roaming for mobile workers. More than one access point
can be configured to create an Extended Service Set (ESS). By placing the access points so that a
continuous coverage area is created, wireless users within this ESS can roam freely. All wireless
network cards and access points within a specific ESS must be configured with the same SSID.
Figure 3-3. Wireless LAN Roaming
<BSS2>
Seamless Roaming
<ESS>
<BSS1>
Server
Switch
Desktop PC
Access Point
PC with Wireless
PCI Adapter
Notebook with Wireless
PC Card Adapter
Notebook with Wireless
PC Card Adapter
Access Point
Switch