问题：

[多选] What are two reasons to implement H·323 gatekeepers？（）

A .  to eliminate the need for VoIP gateways
B .  to scale a VoIP installation with multiple gateways
C .  to provide call admission control and limit the number of simultaneous calls on the network 
D .  to meet the requirement to control H·323 gateways on a LAN
E .  to accept call requests and reduce the load on the gateway