Chapter 12, Problem 1RQ

Program Description Answer

LANs and WANs supports same protocol at the “Layer 3” of OSI model.

Hence, the correct answer is option “B”.

Explanation of Solution

Layer 3: Network layer

• It is the third level of the Open System Interconnection Model (OSI Model).
• Network layer performs the routing of packet from source to destination.
• For routing, it converts the data into packets, and after reaching the destination, it converts back to the data.
• The primary responsibilities of this layer is to set up a logical connection, data forwarding, routing and error reporting.
• Both LANs and WANs use the same protocol of layer 3 and other higher of OSI model.

Explanation for incorrect options:

Layer 2: Data link layer

• It makes the transmission of data reliable, which is provided by the physical layer.
• For reliable transfer, it divides the data into data frames and transmits through the communication channel.
• At the destination, it checks for the transmission error and sends the acknowledgement to the source.

Hence, the option “A” is wrong.

Layer 4: Transport layer

• Its purpose is to provide the reliable transfer of data between two processes in the computer.
• This layer ensures the error-free delivery, no loss of data, and duplication.

Hence, the option “C” is wrong.

Layer 5: Session layer

• Session layer deals with how two devices establish a connection, access, and control the connection in the network.
  • It controls the data transfer between two processes in the communicating host.
  • It establishes the logical connection between the source and destination.

Hence, the option “D” is wrong.