Transport Layer Protocols and Their Functions

What is the main role of the transport layer in networking?
A) To ensure physical signal transmission
B) To provide logical communication between processes
C) To translate hostnames to IP addresses
D) To handle congestion in the data link layer

To provide logical communication between processes

What are the main services expected by the application layer?
A) Packet segmentation, best-effort delivery, low latency
B) Guaranteed message delivery, ordered delivery, flow control
C) Error correction, packet reordering, checksum calculation
D) Multiplexing, encapsulation, and queue management

Guaranteed message delivery, ordered delivery, flow control

How does demultiplexing work at the transport layer?
A) By combining multiple segments into one
B) By using IP addresses and port numbers to direct segments to the correct socket
C) By forwarding packets to the next hop router
D) By segmenting application data into transport layer packets

By using IP addresses and port numbers to direct segments to the correct socket

What is the main difference between connectionless and connection-oriented multiplexing?
A) Connectionless multiplexing uses a four-tuple for sockets.
B) Connection-oriented multiplexing identifies sockets using IP addresses only.
C) Connection-oriented multiplexing uses a four-tuple, while connectionless uses a two-tuple.
D) Connectionless multiplexing requires handshaking before data exchange.

Connection-oriented multiplexing uses a four-tuple, while connectionless uses a two-tuple.

Which of the following is NOT a characteristic of UDP?
A) Connectionless communication
B) Reliable data transfer
C) Minimal overhead with an 8-byte header
D) No handshaking before transmission

Reliable data transfer

Why is UDP used in real-time applications like video streaming?
A) It guarantees in-order delivery of packets.
B) It can retransmit lost packets quickly.
C) It avoids delays by not waiting for acknowledgments.
D) It has built-in flow control mechanisms.

It avoids delays by not waiting for acknowledgments.

What are the key features of TCP?
A) Full-duplex communication, error correction, and connectionless transmission
B) Reliable delivery, congestion control, and connection-oriented transmission
C) Stateless communication, low latency, and unordered delivery
D) Checksum verification, flow control, and application-level encryption

Reliable delivery, congestion control, and connection-oriented transmission

What does TCP's sliding window protocol enable?
A) Reliable delivery, flow control, and efficient bandwidth use
B) Multiplexing and error detection
C) Packet segmentation and encapsulation
D) Load balancing between multiple network paths

Reliable delivery, flow control, and efficient bandwidth use

Why does TCP use a three-way handshake for connection establishment?
A) To reduce overhead compared to a two-way handshake
B) To initialize and synchronize sequence numbers between the sender and receiver
C) To ensure symmetric connection release
D) To prevent packet reordering during data transfer

To initialize and synchronize sequence numbers between the sender and receiver

What problem does the two-way handshake face that the three-way handshake resolves?
A) It cannot handle variable RTTs.
B) It leaves connections in a "half-open" state if the client crashes.
C) It doesn't provide flow control.
D) It cannot support full-duplex communication.

It leaves connections in a 'half-open' state if the client crashes.

What does TCP's flow control mechanism prevent?
A) Packet loss due to network congestion
B) The sender from overwhelming the receiver's buffer space
C) The reordering of segments at the receiver
D) Packet duplication during retransmissions

The sender from overwhelming the receiver's buffer space

How does TCP determine the size of the sending window?
A) It is fixed for every connection.
B) It is the minimum of the congestion window (cwnd) and the advertised receive window (WIN).
C) It is equal to the receiver's buffer size.
D) It depends solely on the RTT.

It is the minimum of the congestion window (cwnd) and the advertised receive window (WIN).

What is the primary goal of TCP's congestion control?
A) To maximize throughput while avoiding congestion collapse
B) To minimize latency during transmission
C) To provide error-free data transfer
D) To ensure fairness in resource allocation among users

To maximize throughput while avoiding congestion collapse

What is the difference between TCP Tahoe and TCP Reno during packet loss?
A) Tahoe cuts the window in half, while Reno sets it to zero.
B) Tahoe restarts with slow start, while Reno uses fast retransmit and recovery.
C) Tahoe uses additive increase, while Reno uses multiplicative increase.
D) Tahoe handles packet loss using duplicate ACKs, while Reno uses timeouts.

Tahoe restarts with slow start, while Reno uses fast retransmit and recovery.

Which transport protocol provides reliable, in-order delivery of data?
A) UDP
B) TCP
C) IP
D) ARP

B) TCP

What is a segment in the transport layer?
A) A portion of data encapsulated at the physical layer
B) A fixed-size packet at the data link layer
C) A unit of data exchanged between the transport and network layers
D) A complete message transmitted by the application layer

C) A unit of data exchanged between the transport and network layers

What unique identifiers are used by TCP sockets for multiplexing?
A) Source and destination IP addresses
B) Source and destination port numbers
C) Source IP address, destination IP address, and protocol type
D) Source IP address, source port number, destination IP address, and destination port number

D) Source IP address, source port number, destination IP address, and destination port number

In connectionless multiplexing (UDP), how are sockets identified?
A) By the four-tuple (source IP, source port, destination IP, destination port)
B) By the two-tuple (destination IP, destination port)
C) By the protocol field in the segment header
D) By the checksum field in the segment

B) By the two-tuple (destination IP, destination port)

What is the primary error-detection mechanism used in UDP?
A) CRC (Cyclic Redundancy Check)
B) Parity bit
C) Checksum
D) Sequence numbers

C) Checksum

Why does UDP have lower overhead than TCP?
A) It avoids multiplexing and demultiplexing.
B) It does not implement error correction or retransmissions.
C) It uses fixed sequence numbers.
D) It includes flow control in the application layer.

B) It does not implement error correction or retransmissions.

Which field in the TCP segment header is used to detect congestion when ECN (Explicit Congestion Notification) is enabled?
A) SYN
B) PSH
C) ECE
D) FIN

C) ECE

What does the ACK flag in the TCP header indicate?
A) The segment contains urgent data.
B) The segment is acknowledging received data.
C) The segment is initiating a new connection.
D) The segment is requesting connection termination.

B) The segment is acknowledging received data.

What is the purpose of TCP's slow start mechanism?
A) To avoid packet loss by starting with a low congestion window size and increasing it exponentially
B) To recover from packet loss by reducing the congestion window to zero
C) To maintain a fixed send rate during the initial connection
D) To ensure fairness between competing TCP connections

A) To avoid packet loss by starting with a low congestion window size and increasing it exponentially

What does "multiplicative decrease" in congestion control involve?
A) Doubling the congestion window size after each RTT
B) Cutting the congestion window size by half after detecting packet loss
C) Increasing the congestion window linearly until loss occurs
D) Reducing the advertised receive window

B) Cutting the congestion window size by half after detecting packet loss

What advantage does TCP Reno have over TCP Tahoe?
A) It uses a simpler congestion control mechanism.
B) It avoids reducing the congestion window to 1 MSS during packet loss.
C) It uses timeout-based retransmissions exclusively.
D) It eliminates the need for fast retransmissions.

B) It avoids reducing the congestion window to 1 MSS during packet loss.