Which three things can be restricted by the Class of Service in a traditional PBX？ （）

A. EIGRP can summarize per interface.
B. OSPF router databases remain independent.
C. When they are configured with stubs， EIGRP regularly floods the topology.
D. OSPF topology decisions are made independent of hierarchy or area.

A. close to the servers
B. close to the end users
C. at the Internet edge
D. in front of web server farms