1. What is the primary role of the Transport Layer in the OSI model?
Correct Answer: b) Providing end-to-end communication between applications
Explanation: The Transport Layer (Layer 4) provides logical communication between application processes running on different hosts.
2. Which of the following is NOT a function of the Transport Layer?
Correct Answer: c) Logical addressing
Explanation: Logical addressing is handled by the Network Layer (IP addresses), not the Transport Layer.
3. Which Transport Layer protocol provides connection-oriented communication?
Correct Answer: b) TCP
Explanation: TCP provides reliable, connection-oriented communication with features like sequencing, acknowledgments, and flow control.
4. What is multiplexing in the Transport Layer?
Correct Answer: a) Combining multiple data streams into one connection
Explanation: Multiplexing allows multiple application processes to share a single transport connection using port numbers.
5. Which layer ensures reliable data transfer between two hosts?
Correct Answer: c) Transport Layer
Explanation: The Transport Layer (specifically TCP) provides reliability through acknowledgments, retransmissions, and sequencing.
6. How many bytes is the minimum TCP header size?
Correct Answer: b) 20 bytes
Explanation: The TCP header is 20 bytes minimum (without options) and can expand to 60 bytes with options.
7. Which TCP flag is used to initiate a connection?
Correct Answer: b) SYN
Explanation: The SYN (Synchronize) flag is set in the first segment of the TCP three-way handshake to initiate a connection.
8. What is the purpose of the three-way handshake in TCP?
Correct Answer: b) To establish a connection and synchronize sequence numbers
Explanation: The three-way handshake (SYN, SYN-ACK, ACK) establishes the connection and synchronizes Initial Sequence Numbers (ISNs).
9. Which field in the TCP header ensures data integrity?
Correct Answer: c) Checksum
Explanation: The 16-bit checksum field allows the receiver to verify the integrity of both the header and payload data.
10. What happens if an ACK is lost during TCP communication?
Correct Answer: a) The sender retransmits the packet after timeout
Explanation: TCP uses retransmission timers - if an ACK isn't received within the timeout period, the sender retransmits the unacknowledged segment.
11. Which TCP feature prevents buffer overflow at the receiver?
Correct Answer: a) Flow Control
Explanation: Flow control uses the window size field to inform the sender how much data the receiver can accept, preventing buffer overflow.
12. What is the purpose of the Window Size field in the TCP header?
Correct Answer: b) To control the amount of unacknowledged data
Explanation: The window size indicates how many bytes the receiver is willing to accept, implementing flow control.
13. Which TCP flag is used to terminate a connection?
Correct Answer: c) FIN
Explanation: The FIN (Finish) flag is used to initiate connection termination, indicating the sender has no more data to transmit.
14. What is TCP Fast Retransmit triggered by?
Correct Answer: b) Three duplicate ACKs
Explanation: Fast Retransmit detects packet loss through three duplicate ACKs (indicating a gap in received data) and retransmits without waiting for timeout.