At which level of the OSI reference model does a Channel Service Unit/Data Service Unit (CSU/DSU) operate?
A. The physical layer
B. The network layer
C. The application layer
D. The transport layer
Answer:A
At which level of the OSI reference model does a Channel Service Unit/Data Service Unit (CSU/DSU) operate?
A. The physical layer B. The network layer C. The application layer D. The transport layer