H3C Technologies H3C WX3000E Series Wireless Switches - Manual (Page 456)

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vulnerable to malicious attacks. Therefore, WLAN mesh network security becomes an essential part of
WLAN mesh networks. Security involves encryption algorithms and distribution and management of keys.
A PSK + AES + CCMP combination is used for securing mesh networks.
Mobile link switch protocol
At any given time, an active link must be available between a rail MP and a train MP for data
communication. MLSP was developed to create and break link during train movement.
As shown in
Figure 180 , when the train is moving, it must break the existing active link with rail MP 2 and
create a new active link with another rail MP.
Figure 459 Diagram for MLSP
• Active link—Logical link through which all data communication from/to a train MP happens.
Forward all data sent from or to the rail MP.
• Dormant link—Logical link over which no data transfer happens, but it meets all the criteria for
becoming an active link.
MLSP advantages
• MLSP makes sure the link switch time is less than 30 milliseconds.
• MLSP operates correctly even if the devices get saturated at high power level.
• MLSP achieves zero packet loss during link switch.
MLSP operation
MLSP establishes multiple links at any given time between a train MP and multiple rail MPs to provide link
redundancy, thus ensuring high performance and good robustness for the network.
The following parameters are considered by MLSP for link switch. Based on the deployment, all theses
parameters are tunable to achieve best results.
• Link formation RSSI/link hold RSSI—This is the minimum RSSI to allow a link to be formed and held.
Therefore, the minimum RSSI must be ensured at any given point in the tunnel. Otherwise, the error
rate can be very high.
• Link switch margin—If the RSSI of the new link is greater than that of the current active link by the
link switch margin, active link switch occurs. This mechanism is used to avoid frequent link switch.