Multiple-Choice Questions

Transcription

1 King Saud University College of Computer and Information Sciences Information Technology Department First Semester 1436/1437 IT224: Networks 1 Sheet# 5 (chapter 20-21) Multiple-Choice Questions 1. is a dynamic mapping protocol in which a physical address is found for a given IP address. a. ARP b. RARP c. ICMP d. None of the above 2. A router reads the address on a packet to determine the next hop. a. IP b. MAC c. Source d. ARP 3. An ARP replay is to a. Broadcast; all hosts b. Multicast; one host c. Unicast; all hosts d. Unicast; one host 4. An ARP request is to a. Broadcast; all hosts b. Multicast; one host c. Unicast; all hosts d. Unicast; one host 5. When the hop-count field reaches zero and the destination has not been reached, a error message is sent. a. Destination unreachable b. Time-exceeded c. Parameter-problem d. Redirection 6. When not all fragments of a message have been received within the designated amount of time, a error message is sent. a. Source-quench b. Time-exceeded c. Parameter-problem d. Time-stamp-request 1

2 7. Errors in the header or option fields of an IP datagram require a error message. a. Parameter-problem b. Source-quench c. Router-solicitation d. Redirection 8. One method to alert a source host of congestion is the message. a. Redirection b. Echo-request c. Source-quench d. Destination-unreachable 9. In, each packet of a message need not to follow the same path from sender to receiver. a. Message switching b. the virtual approach to packet switching c. the datagram approach to packet switching d. none of the above 10. A best-effort delivery service such as IP does not include a. Error checking b. Error correction c. Datagram acknowledgment d. All the above 11. An HLEN value of decimal 10 means. a. There is 10 bytes of options b. There is 40 bytes of options c. There is 10 bytes in the header d. There is 40 bytes in the header 12. In IPv4, what is the value of the total length field in bytes if the header is 28 bytes and the data field is 400 bytes? a. 428 b. 407 c. 107 d A datagram is fragmented into three smaller datagrams. Which of the following is true? a. The do not fragment bit is set to 1 for all three datagrams. b. the more fragment bit is set to 0 for all three datagrams. c. The identification field is the same for all three datagrams. d. The offset field is the same for all three datagrams. 14. If the fragment offset has a value of 100, it means that a. The datagram has not been fragmented b. The datagram is 100 bytes in size c. The first byte of the datagram is byte 100 2

3 d. The first byte of the datagram is byte What is needed to determine the number of the last byte of a fragment? a. Identification number b. Offset number c. Total data length d. (b) and (c) 3

4 Exercises: 1. Which fields of the IPv4 header change from router to router? 2. Calculate the HLEN (in IPv4) value if the total length is 1152 bytes, 1100 of value is data from the upper layer. 3. The value of HLEN in an IPv4 datagram is 15. How many option bytes are present? 4. The size of the option field of an IPv4 datagram is 20 bytes. What is the value of HLEN? What is the value in binary? 5. An lpv4 datagram is carrying 540 bytes of data. If there is no option information. What is the value of the header length field? What is the value of the total length field? 6. An lpv4 fragment has arrived with an offset value of 480. How many bytes of data were originally sent by the source before this fragment data? 7. In an lpv4 datagram, the M bit is 1; the value of HLEN is 5. The value of total length is 250, and the offset value is 240. What is the number of the first byte and number of the last byte in this datagram? Is this the last fragment, the first fragment, or a middle fragment? 8. An IPv4 datagram has arrived with the following information in the header ( in hexadecimal): 0x F6 EB 7B 4E A4 0E x4 0x5 0x00 0x x x x17 0x11 F6EB 0x7B 4E xA4 0E a) Are there any options? b) Is the packet fragmented? c) What is the size of the data? d) How many more routers can the packet travel to? e) What is the identification number of the packet? 4

5 9. Suppose a router receives an IP packet containing 4180 bytes of data and ID 2231; it has to forward the packet to a network with maximum transmission unit of 1500 bytes. Assume that the IP header is 20 byte long. Show the fragments that router creates and specify the values in each fragment header. 5