NRS-1 Chapter Seven

Given the values MSS=1000 bytes, cwnd value=6, window size=5000, and sender's SN=5000, what will be the ACK number from the receiving station after the sender sends its next set of segments to the receiving station? A. 6000 B. 11001 C. 11000 D. 10000

10000 The sender can never send more than the advertised window size, which is 5000 (even if its congestion window is higher). If the initial sequence number is 5000, then the next sequence number expected by the receiver is always the sequence number (5000) + the number of bytes sent (5000) = 10000.

A TCP sequence or acknowledgment number consists of ______ bits. A. 30 B. 64 C. 24 D. 32

32 There are 32 bits in a sequence number.

Which of the following is least likely to be used as an ephemeral port? A. 1025 B. 53212 C. 1487 D. 65938

65938 This is outside the acceptable range of ephemeral ports, 1024-65535.

Which of the following types of applications would be least likely to use the UDP protocol? A. A "request-response" application B. An application that is sensitive to packet loss C. An application that is sensitive to delay D. A real-time application

An application that is sensitive to packet loss This is because UDP does not guarantee delivery so it would be better to use TCP to avoid packet loss.

Which of the following is not a characteristic of the TCP protocol? A. Reliable data transfer B. Connectionless operation C. Flow control supported D. Full-duplex operation

Connectionless operation TCP always requires the establishment of a connection.

Which of the following are possible mechanisms by which a TCP sending process could recognize that packets it sent to a receiver had been dropped by the network? A. An RSND bit from the receiving TCP process B. Duplicate ACK numbers C. An advertised window size of 0 D. An ICMP source quench message

Duplicate ACK numbers This indicates that the receiver has not received at least one segment and that segment must be re-sent.

Which of the following TCP bits is set to indicate that an application wishes to close an open connection? A. RST B. FIN C. URG D. ACK

FIN FIN indicates that one side of an open connection wishes to initiate a close.

TCP provides many advanced features missing from UDP. Which of the following is an advantage that UDP has over TCP? A. It provides reliable data transfer. B. It can recover gracefully from packet loss. C. It reacts to network congestion. D. It adds little overhead to the data transfer.

It adds little overhead to the data transfer. UDP does not require connection establishment and has a small header, so it adds very little overhead to an application.

Which of the following TCP flags is not matched with the correct definition? A. SYN—Indicates the start of a TCP connection. B. ACK—Acknowledges that a TCP segment has been received. C. FIN—Indicates the closing of a TCP session. D. RST—Re-sets the sequence numbers for a TCP session.

RST—Re-sets the sequence numbers for a TCP session RST indicates that a TCP connection is unavailable, if, for example, an attempt is made to connect to a port that is not available.

Which of the following is not a transport layer protocol? A. TP4 B. TCP C. RTP D. UDP

RTP TCP, UDP, and TP4 are transport protocols.

Which of the following is not a characteristic of the UDP protocol? A. Reliable data transfer B. Connectionless operation C. No flow control D. Appropriate for real-time traffic

Reliable data transfer UDP does not provide reliable data transfer because it does not guarantee delivery.

After a client initiates a connection request to a server with the SYN bit set, the server usually responds with a packet that has the ______ bit set. A. SYN B. ACK C. SYN and ACK D. SYN, ACK, and URG

SYN and ACK Both bit sets are included in the packet.

When operating in slow start mode, which of the following describes the mechanisms to throttle the amount of data sent? A. The receiver's advertised window size B. The sender's congestion window and the sender's advertised window size C. The sender's congestion window and the receiver's advertised window size D. The maximum segment size and the URG pointer

The sender's congestion window and the receiver's advertised window size The sender will send the lower of the two values.

Which of the following statements about transport layer protocols is false? A. Most Internet applications use a transport layer protocol. B. Transport layer protocols can provide both reliable and unreliable services. C. Transport layer protocols provide end-to-end services for applications. D. Transport layer protocols require additional software be added to your operating system.

Transport layer protocols require additional software be added to your operating system. All modern OSes come with a TCP/IP stack that includes the TCP transport protocol.

DNS is a unique protocol in terms of its transport selection because simple name lookups use UDP, while "zone transfers" that transfer a large amount of name resolution information from one DNS server to another use TCP. What is the least likely reason for using this approach? A. Name lookups are simple request-response. B. TCP is a reliable protocol. C. An unreliable zone transfer could result in serious name resolution discrepancies in a network. D. UDP cannot be used for bulk file transfers.

UDP cannot be used for bulk file transfers. While it is usually better not to use UDP for bulk file transfers, it can be done (TFTP uses UDP for bulk file transfers). The other answers are all good reasons for DNS to use both TCP and UDP for different functions.