H3C Technologies H3C WX3000E Series Wireless Switches - Manual (Page 743)

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The master AC and BAS ACs exchange information through tunnels.
MAC-BAC operates as follows:
1. The master AC establishes tunnels with BAS ACs.
2. An AP obtains the IP address of the master AC from the Option field in the reply sent by the DHCP
server (recommended).
An AP can also obtain an IP address in other ways.
3. The AP unicasts a discovery request to the master AC.
4. The master AC returns a discovery response that contains the CAPWAP IP address of the BAS AC
with the lowest workload.
5. The AC establishes a tunnel with the specified BAS AC.
6. The BAS AC reports the AP information to the master AC so that the master AC can manage the
BAS ACs.
Figure 751 Network diagram
NOTE:
H3C recommends that you use Option to obtain the IP address of the master AC.
VLAN pool
A VLAN pool contains a group of VLANs. It can assign VLAN IDs only to wireless clients.
Multicast optimization
Support for this feature depends on the device model. For more information, see " About the H3C Access
Controllers Web-Based Configuration Guide ."
WLAN selects the lowest transmit rate for multicast packets and provides no multicast retransmission
mechanism. Therefore, WLAN cannot meet the requirements of some multicast applications that are not
delay-sensitive but are data-integrity sensitive, such as HD VoD. The multicast optimization feature can
solve these problems by enabling APs to convert multicast packets to unicast packets, so WLAN can
provide retransmission service and higher transmit rates for the converted unicast packets.
Unless otherwise specified, the unicast packets in this chapter refer to the wireless unicast packets that
have the priority of video.