Computer Networking Past Paper C Part A: Multiple Choice Questions (10 marks) 1. A network administrator has received the IPv6 prefix 2001:DB8::/48 for subnetting. Assuming the administrator does not subnet into the interface ID portion of the address space, how many subnets can the administrator create from the /48 prefix? a) 16 b) 256 c) 4096 d) 65536 2. Which type of IPv6 address is not routable and used only for communication on a single subnet? a) global unicast address b) link-local address c) loopback address d) unique local address e) unspecified address 3. Which of these devices are not considered to be an end device in a network? a) VoIP phone b) security camera c) access point d) TelePresence endpoint 4. Which network migration technique encapsulates IPv6 packets inside IPv4 packets to carry them over IPv4 network infrastructures? a) encapsulation b) translation c) dual-stack d) tunneling 5. What method is used to manage contention-based access on a wireless network? a) CSMA/CD b) priority ordering c) CSMA/CA d) token passing 6. Which is a function of the Logical Link Control (LLC) sublayer? a) to define the media access processes that are performed by the hardware b) to provide data link layer addressing c) to identify which network layer protocol is being used d) to accept segments and package them into data units that are called packets 7. Which statement correctly describes frame encoding? a) It uses the characteristic of one wave to modify another wave. b) It transmits data signals along with a clock signal which occurs at evenly spaced time durations. c) It generates the electrical, optical, or wireless signals that represent the binary numbers of the frame. d) It converts bits into a predefined code in order to provide a predictable pattern to help distinguish data bits from control bits. 8. Which of the following are not a responsibility of the transport layer? a) meeting the reliability requirements of applications, if any b) multiplexing multiple communication streams from many users or applications on the same network c) identifying the applications and services on the client and server that should handle transmitted data d) formatting data into a compatible form for receipt by the destination devices 9. Which action is taken by a Layer 2 switch when it receives a Layer 2 broadcast frame? a) It drops the frame. b) It sends the frame to all ports except the port on which it received the frame. c) It sends the frame to all ports that are registered to forward broadcasts. d) It sends the frame to all ports. 10. When the store-and-forward method of switching is in use, what part of the Ethernet frame is used to perform an error check? a) CRC in the trailer b) source MAC address in the header c) destination MAC address in the header d) protocol type in the header 11. What is the purpose of using a source port number in a TCP communication? a) to notify the remote device that the conversation is over b) to assemble the segments that arrived out of order c) to keep track of multiple conversations between devices d) to inquire for a non-received segment 12. What is the primary purpose of ARP? a) translate URLs to IP addresses b) resolve IPv4 addresses to MAC addresses c) provide dynamic IP configuration to network devices d) convert internal private addresses to external public addresses Part B: Subnetting Questions (30 marks) 1. Given the host address 42.35.35.111 and the broadcast address 42.35.35.255: a) Find the network address of the network. b) What is the 37th usable host address in this network? 2. Advanced Digital Computer Company needs to subnet their allocated network address 192.168.64.0/20 for their corporate network, given in the diagram below (Figure 1). Figure 1 Complete the table below according to the following requirements using the original network address 192.168.64.0/20: (a) Use VLSM addressing, ie the minimum number of bits to include all required hosts. (b) The gateways are the last usable host address(es) of each subnet. (c) The printer is the 5th usable host address of each subnet, except for the WANs. Network (670 hosts) Yellow Network (20 hosts) Cyan network address network address subnet mask subnet mask broadcast address broadcast address gateway address gateway address printer address printer address Network (560 hosts) Grey Network (290 hosts) Purple network address network address subnet mask subnet mask broadcast address broadcast address gateway address gateway address printer address printer address Network (460 hosts) Gold Network (50 hosts) Orange network address network address subnet mask subnet mask broadcast address broadcast address gateway address gateway address printer address printer address Network (150 hosts) Silver Network (200 hosts) Blue network address network address subnet mask subnet mask broadcast address broadcast address gateway address gateway address printer address printer address Network (WAN) Red Network (WAN) Green network address network address subnet mask subnet mask broadcast address broadcast address gateway addresses gateway addresses Network (WAN) Aqua network address gateway addresses subnet mask broadcast address Part C: Short Answer Questions (60 marks) Question 1. IP addresses are used to communicate over the Internet. a) IPv6 addresses are most commonly written using the hexadecimal number system. Explain the hexadecimal number system. b) What are the main features of IPv4 private addresses? c) Which IPv4 addresses are private? d) EUI‐64 is a particular addressing process using IPv6. Explain the process of obtaining an EUI‐ 64 address, and explain its purpose. e) What are the addresses in each of the IPv4 classful address blocks A,B,C,D and E? Question 2. a) What is the purpose of Application Layer Protocols? b) How do the following Client--Server applications function in a networked environment? a. SMTP b. IMAP and POP3 Question3. a) What are the reasons and benefits of segmenting data? b) In our modern reliable networks wouldn’t it be more efficient to send all traffic using UDP? c) What is the purpose of the ‘sliding window’ concept? When should acknowledgements be sent? Question 4. Networks are an important part of modern society. a) What is the difference between a packet-switched and a circuit-switched network? b) What is the difference between an internet and extranet? Question 5. a) What is the difference between bandwidth, throughput and latency? b) How does network traffic travel across the medium? c) How is the data signal changed when travelling on different media? Question 6. a) What is the difference between a unicast, broadcast and multicast address? b) Give an example of when a unicast, broadcast and multicast address is used. Question 7. a) IP is connectionless. Discuss the implications for this when sending data from a source to a destination. b) Packet delivery using IP uses the “best effort” approach. Discuss the implications for this when sending data from a source to a destination. c) What are some of the reasons that packets can be lost between a source and destination IP address? Question 8. a) Carefully detail what each figure shows. b) Is this a TCP or UDP type connection? Explain the difference between each Transport later protocol. c) For UDP traffic, state fully what occurs when packets are received ‘out of order’?
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