H3C Technologies H3C WX3000E Series Wireless Switches - Manual (Page 324)

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Figure 326 Subway deployment of mesh
The subway WLAN mesh deployment is based on the Mobile Link Switch Protocol (MLSP), which is used
for high-speed link switch with zero packet loss during train movement. New IEEE standard 802.11s is
adopted as the underlying protocol for link formation and communication between mobile radio (MR)
and wayside AP. Train MPs are not required to act as authenticators.
WLAN mesh security
A WLAN network uses air as the communication medium, so it is vulnerable to malicious attacks. In a
mesh network, a wireless connection passes through multiple hops, and thus a mesh network is more
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.
Currently, PSK + CCMP combination is used for securing mesh networks.
Mobile link switch protocol
At any given time, an active link should be available between a rail MP and a train MP for data
communication. MLSP was developed to create and break links during train movement.
As shown in
Figure 327 , 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.