H3C Technologies H3C MSR 50 - Manual (Page 6)

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When a client leaves the coverage of an AP, and then needs to re-join the AP, it must re-associate with
the AP.
802.11 Overview
The WLAN-MAC primarily includes the implementation of IEEE 802.11 MAC layer functionality. Various
modes of MAC are:
z Local-MAC Architecture
z Split-MAC Architecture
In local-MAC architecture, most WLAN services are provided by the AP only. Currently, local-MAC
architecture is not supported.
In split-MAC architecture, the AP and the AC manage different services.
CAPWAP Overview
Introduction to CAPWAP
Control And Provisioning of Wireless Access Points (CAPWAP) defines how an AP communicates with
an AC. It provides a generic encapsulation and transport mechanism between AP and AC, as shown in
Figure 1-5 .
Figure 1-5 CAPWAP
CAPWAP runs on an AP and an AC to provide a secured connection in between. It is built on a standard
client/server model and employs UDP.
On an AP, CAPWAP provides a data tunnel to encapsulate data packets to be sent to the AC. These
packets can be raw 802.11 packets or 802.11 to 802.3 translated packets. On an AC, CAPWAP
provides a control tunnel to support remote AP configuration and management, and WLAN and mobile
management.
With CAPWAP, the AC can dynamically configure an AP based on the information provided by the
administrator.
CAPWAP supports both IPv4 and IPv6.
CAPWAP Link Backup
Dual link establishment
To achieve AC backup, an AP can establish two tunnels with two ACs that must have the same AP
configurations. Only the AC which works in master mode provides services to all the APs in the network
and the slave AC acts as the backup AC. If the master AC fails, APs should quickly use the services
provided by the slave AC. A heartbeat mechanism is used between these two ACs, which ensures that
failure of the master will be detected quickly by the backup AC.