Chapter 10, Problem 1RQ

Program Description Answer

At the Application layer of the OSI model, the proxy servers manage security.

Hence, the correct answer is option “C”.

Explanation of Solution

OSI model:

Network is the collection of two or more computers linked together.

• OSI (Open System Interconnection) is a reference model for the communication network.
• Communication network is the process of allowing nodes to communicate or exchange the data between the nodes through the link.
• It provides seven-layer architecture for the OSI model.

Seven layers of OSI model:

• Physical layer
• Data link layer
• Network layer
• Transport
• Session
• Presentation
• Application

Layer 7: Application layer:

• It interacts with the software application program and provides semantic of data.
• It is the highest layer in the OSI model and close to the end user.
• At the Application layer of the OSI model, the proxy servers manage security.

Explanation for incorrect options:

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.

Hence, the option “A” is wrong.

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 “B” 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 “D” is wrong.