Brocade Mobility RFS7000-GR Controller System Reference Guide (Supporting software release 4.1.0.0-040GR and later) - Manual (Page 26)

12 Brocade Mobility RFS7000-GR Controller System Reference Guide
53-1001944-01
Software overview
1
Interswitch Layer 2 roaming
An associated MU (connected to a switch) can roam to another Access Port connected to a
different switch. Both switches must be on the same Layer 2 domain. Authentication information is
not shared between the switches, nor are buffered packets on one switch transferred to the other.
Pre-authentication between the switch and MU allows faster roaming.
Interswitch Layer 3 roaming
Interswitch Layer 3 roaming allows MUs to roam between switches which are not on the same LAN
or IP subnet without the MUs or the rest of the network noticing. This allows switches to be placed
in different locations on the network without having to extend the MU VLANs to every switch.
Fast roaming
Using 802.11i can speed up the roaming process from one AP to another. Instead of doing a
complete 802.1x authentication each time a MU roams between APs, 802.11i allows a MU to
re-use previous PMK authentication credentials and perform a four-way handshake. This speeds
up the roaming process. In addition to reusing PMKs on previously visited APs, Opportunistic Key
Caching allows multiple APs to share PMKs amongst themselves. This allows an MU to roam to an
AP it has not previously visited and reuse a PMK from another AP to skip the 802.1x authentication.
International roaming
The wireless switch supports international roaming per the 802.11d specification.
MU move command
As a value added proprietary feature between Brocade infrastructure products and Brocade MUs, a
move command has been introduced. The move command permits an MU to roam between ports
connected to the same switch without the need to perform the full association and authentication
defined by the 802.11 standard. The move command is a simple packet up/packet back exchange
with the Access Port. Verification of this feature is dependent on its implementation in one or more
mobile units.
Power save polling
An MU uses Power Save Polling (PSP) to reduce power consumption. When an MU is in PSP mode,
the switch buffers its packets and delivers them using the DTIM interval. The PSP-Poll packet polls
the AP for buffered packets. The PSP null data frame is used by the MU to signal the current PSP
state to the AP.
QoS
QoS provides a data traffic prioritization scheme. QoS reduces congestion from excessive traffic.
If there is enough bandwidth for all users and applications (unlikely because excessive bandwidth
comes at a very high cost), then applying QoS has very little value. QoS provides policy enforcement
for mission-critical applications and/or users that have critical bandwidth requirements when the
switch’s bandwidth is shared by different users and applications.
QoS helps ensure each WLAN on the switch receives a fair share of the overall bandwidth, either
equally or as per the proportion configured. Packets directed towards MUs are classified into
categories such as Management, Voice and Data. Packets within each category are processed
based on the weights defined for each WLAN.
The switch supports the following QoS mechanisms: