Unit 5: Transport layer - Practice Quiz

1 What does a port address identify at the transport layer?

2 How many bits are used for a port number in TCP and UDP?

3 Which range contains the well-known port numbers?

4 Which two components form a socket address?

5 What does the socket address 192.168.1.10:80 represent?

6 Which type of transport protocol is UDP?

7 Which feature is normally associated with UDP?

8 Which application commonly uses UDP because timely delivery is important?

9 Which type of transport protocol is TCP?

10 Which TCP feature helps place received data in the correct order?

11 What does TCP do when data is lost during transmission?

12 What is the main purpose of TCP's 3-way handshake?

13 What is the correct order of messages in TCP's 3-way handshake?

14 Which TCP flag is sent first when a client starts a connection?

15 What is network congestion?

16 Which TCP mechanism begins transmission with a small congestion window?

17 What is a common effect of severe network congestion?

18 What does QoS stand for in computer networking?

19 Which QoS characteristic measures the variation in packet delay?

20 Which technique improves QoS by giving important traffic earlier access to transmission?

21 A client sends an HTTP request from ephemeral port 49160 to a web server. Which source and destination port pair will normally appear in the request segment?

22 Two browser tabs on one computer connect to the same web server and destination port. How can the transport layer distinguish their connections?

23 A server has IP address 192.0.2.15 and listens for HTTPS traffic on port 443. Which value represents its socket address?

24 Which set of values uniquely identifies a TCP connection between two hosts?

25 A live voice application prefers timely delivery and can tolerate occasional packet loss. Why is UDP often selected?

26 A UDP datagram has a total length of 508 bytes. How many bytes belong to application data?

27 A UDP receiver detects a checksum mismatch in an arriving datagram. What is the normal transport-layer response?

28 A TCP sender transmits 600 bytes beginning with sequence number 2400. If all bytes arrive correctly, what acknowledgment number should the receiver send?

29 A TCP receiver advertises a window of 4000 bytes, and 1500 transmitted bytes remain unacknowledged. How much additional data may the sender transmit?

30 A TCP segment is lost, but later segments reach the receiver. Which TCP behavior most directly helps the sender infer this loss before a timeout?

31 A client begins a TCP connection with sequence number 700 and sends SYN. The server chooses sequence number 3000. What should the server send next?

32 After receiving a server's SYN + ACK with sequence number 500 and acknowledgment number 101, what final handshake segment should the client send?

33 Why does TCP use a three-way handshake rather than only exchanging a client request and a server acknowledgment?

34 A TCP sender has a congestion window of 2 MSS at the start of slow start. Assuming every segment is acknowledged and no loss occurs, what is the window after two RTTs?

35 A TCP sender detects segment loss through three duplicate acknowledgments rather than a timeout. Which action is most appropriate?

36 A TCP flow has a receiver window of 12 KB and a congestion window of 8 KB. What is the maximum amount of unacknowledged data the sender may have in transit?

37 A video conference has enough average bandwidth but experiences irregular packet arrival times, causing choppy playback. Which QoS characteristic is the main problem?

38 Which application generally has the strictest requirement for low end-to-end delay?

39 A router must give voice packets faster service than bulk file-transfer packets during congestion. Which technique best supports this goal?

40 A network operator wants to limit a customer's traffic to an agreed rate while allowing short bursts to use accumulated credits. Which mechanism is most suitable?

41 A host has a TCP server bound to port 5000 and a UDP application bound to port 5000 on the same local IP address. Which statement best describes this configuration?

42 A TCP server accepts connections from three clients. All established connections use the server's IP address and port 443. Why can the operating system still demultiplex their segments correctly?

43 An IPv4 UDP sender computes a checksum whose one's-complement result is numerically zero. What value is placed in the UDP checksum field?

44 An IPv4 packet carries a UDP datagram whose UDP Length field is smaller than the IP payload length but is at least 8 bytes. Assuming the datagram is otherwise valid, how is the excess IP payload treated by UDP?

45 A TCP endpoint chooses initial sequence number 4000, sends a SYN, transmits 1200 data bytes, and then sends a FIN. No other data is sent. What acknowledgment number should confirm receipt of everything?

46 A TCP receiver advertises acknowledgment number 7001 and a receive window of zero. Which sender behavior remains permitted by TCP persist processing?

47 A server receives an old duplicate SYN for a connection that no longer exists and replies with a SYN-ACK. The original client currently has no matching connection state. Under normal TCP behavior, what prevents the obsolete connection from becoming established?

48 Two TCP hosts simultaneously perform active opens to each other using matching endpoint pairs. Each is initially in SYN-SENT. Which transition correctly describes a valid simultaneous open?

49 Why does the endpoint performing the active TCP close normally remain in TIME-WAIT for approximately twice the maximum segment lifetime?

50 TCP Reno detects loss through three duplicate ACKs while , with 20 MSS outstanding. Immediately after entering fast recovery, what are the usual values of and ?

51 During TCP NewReno fast recovery, an ACK acknowledges some but not all data that was outstanding when recovery began. How is this partial ACK normally handled?

52 A TCP sender has and receives an advertised window of . It currently has of unacknowledged data in flight. Ignoring segmentation limits, how much additional data may it send?

53 A 12,000-bit packet crosses three store-and-forward links, each operating at 6 Mbps with 4 ms propagation delay. The two routers each add 3 ms of queueing delay. Ignoring processing time, what is the end-to-end delay?

54 A token bucket initially contains 12 KB of tokens and replenishes at 2 KB/s. A source transmits continuously at 10 KB/s whenever tokens permit. What is the maximum initial duration for which 10 KB/s can be sustained?

55 A byte-oriented leaky-bucket shaper has a constant output rate of 3 Mbps and is initially empty. Bursts totaling 12 Mb arrive instantaneously. Ignoring packetization, when does the final bit leave the shaper?

56 A 60 Mbps link uses work-conserving weighted fair scheduling for three flows with weights . All are backlogged, but the third flow can use at most 18 Mbps. What rate is allocated to the second flow?

57 An Integrated Services flow requests a strict end-to-end delay bound using RSVP. Which additional condition is essential for the bound to be credible?

58 In a Differentiated Services domain, which statement most accurately describes how scalable QoS treatment is provided?

59 What is the principal congestion-control advantage of Random Early Detection over tail-drop queue management?

60 A real-time application receives all packets with average one-way delay below its limit, yet playback repeatedly stalls because successive packet delays vary widely. Which QoS characteristic is primarily inadequate?