Protocol Data Units at each layer in Computer Networks - Practice Problems & Coding Challenges

Challenge - 5 Problems

📋 Factual

intermediate

Identify the PDU at the Network Layer

Which of the following is the correct Protocol Data Unit (PDU) name used at the Network layer in the OSI model?

A Segment

B Packet

C Frame

D Bit

💡 Hint

Think about the layer responsible for routing data between devices.

The Network layer uses packets as its PDU. Packets contain logical addressing information to route data across networks.

🧠 Conceptual

intermediate

Match the PDU to the OSI Layer

Match the following PDUs to their correct OSI model layers:
1. Frame
2. Segment
3. Packet
4. Bit

A 1 - Data Link, 2 - Transport, 3 - Network, 4 - Physical

B 1 - Network, 2 - Data Link, 3 - Transport, 4 - Physical

C 1 - Transport, 2 - Network, 3 - Data Link, 4 - Physical

D 1 - Physical, 2 - Network, 3 - Transport, 4 - Data Link

💡 Hint

Recall the order of OSI layers from bottom to top.

The Data Link layer uses frames, Transport uses segments, Network uses packets, and Physical uses bits.

🔍 Analysis

advanced

Analyze PDU Transformation Across Layers

When data is sent from an application on one device to another, which sequence correctly shows how the Protocol Data Unit (PDU) changes as it moves down the OSI layers?

A Data → Segment → Packet → Frame → Bit

B Bit → Frame → Packet → Segment → Data

C Frame → Packet → Segment → Data → Bit

D Data → Packet → Segment → Frame → Bit

💡 Hint

Consider the encapsulation process from top to bottom layers.

Data starts at the Application layer as data, then becomes a segment at Transport, a packet at Network, a frame at Data Link, and finally bits at Physical.

❓ Comparison

advanced

Compare PDUs of Transport and Data Link Layers

Which statement correctly compares the Protocol Data Units (PDUs) of the Transport and Data Link layers?

A Transport layer uses bits; Data Link layer uses packets.

B Transport layer uses packets; Data Link layer uses bits.

C Transport layer uses frames; Data Link layer uses segments.

D Transport layer uses segments; Data Link layer uses frames.

💡 Hint

Think about which layer handles error checking and flow control.

The Transport layer's PDU is called a segment, which manages data flow and reliability. The Data Link layer uses frames to handle physical addressing and error detection.

❓ Reasoning

expert

Determine the PDU Size Impact on Network Performance

If the Protocol Data Unit (PDU) size at the Data Link layer is increased significantly, what is the most likely impact on network performance?

A Increased PDU size always decreases throughput due to longer transmission times.

B Increased PDU size has no effect on network performance because only bits matter at the Physical layer.

C Increased PDU size reduces overhead, improving throughput but may increase error retransmission if errors occur.

D Increased PDU size reduces error rates because larger frames are easier to detect.

💡 Hint

Consider the trade-off between overhead and error impact.

Larger PDUs reduce the relative overhead of headers, improving throughput. However, if an error occurs, more data must be retransmitted, potentially reducing efficiency.