Brocade Communications Systems RFS6000 System Reference Manual page 29

WMM-unscheduled APSD
This feature is also known as WMM Power Save or WMM-UPSD (Unscheduled Power Save
Delivery). WMM-UPSD defines an unscheduled service period, which are contiguous periods of
time during which the controller is expected to be awake. If the controller establishes a downlink
flow and specifies UPSD power management, it requests (and the AP delivers) buffered frames
associated with that flow during an unscheduled service period. The controller initiates an
unscheduled service period by transmitting a trigger frame. A trigger frame is defined as a data
frame (e.g. an uplink voice frame) associated with an uplink flow with UPSD enabled. After the AP
acknowledges the trigger frame, it transmits the frames in its UPSD power save buffer addressed
to the triggering controller.
UPSD is well suited to support bi-directional frame exchanges between a voice STA and its AP.
Multiple VLANs per WLAN
The controller permits the mapping of a WLAN to more than one VLAN. When a Client associates
with a WLAN, the Client is assigned a VLAN by means of load balance distribution. The VLAN is
picked from a pool assigned to the WLAN. The controller tracks the number of Clients per VLAN,
and assigns the least used/loaded VLAN to the Client. This number is tracked on a per-WLAN basis.
A broadcast key, unique to the VLAN, encrypts packets coming from the VLAN. If two or more
Clients are on two different VLANs, they both hear the broadcast packet, but only one can decrypt
it. The controller provides each Client a unique VLAN broadcast key as part of the WPA2 handshake
or group key update message of a WPA handshake.
Limiting users per VLAN
Not all VLANs within a single WLAN must have the same DHCP pool size. Assign a user limit to each
VLAN to allow the mapping of different pool sizes.
Specify the VLAN user limit. This specifies the maximum number of Clients associated with a VLAN
(for a particular WLAN). When the maximum Client limit is reached, no more Clients can be
assigned to that VLAN.
Packet flows
There are four packet flows supported when the controller is configured to operate with multiple
VLAN per WLAN:
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Brocade Mobility RFS6000 and RFS7000 System Reference Guide
53-1001858-01
Unicast From Wireless Client – Frames are decrypted, converted from 802.11 to 802.3 and
sent to the wired side of the VLAN dynamically assigned to the mobile device. If the destination
is another mobile device on the wireless side, the frame is encrypted and sent over the air.
Unicast To Wireless Client – The frame is checked to ensure the VLAN is same as that
assigned to the mobile device. It is then converted to an 802.11 frame, encrypted, and sent
over the air.
Multicast/Broadcast From Wireless Client – The frame is treated as a unicast frame from the
Client, with the exception that it is encrypted with the per-VLAN broadcast key and then
transmitted over the air.
Multicast/Broadcast from Wired Side – If the frame comes from a VLAN mapped to the WLAN,
it's encrypted using a per-VLAN broadcast key and transmitted over the air. Only Clients on that
VLAN have a broadcast key that can decrypt this frame. Other Clients receive it, but discard it.
Software overview
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