(a) (i) Identify the names of Protocol Data Units PDU2, PDU3, and PDU4 below.
(ii) Name the process that is used to place one message inside another message.
(iii) State the layer names for OSI layer 1 and layer 2.
(iv) Which OSI layer (number or name) is responsible for end-to-end connections and reliability?
(v) Which TCP/IP layer is responsible for control of hardware devices and media?
(b) Consider the network topology below.
(i) How many broadcast domains (networks) are there in the topology?
(ii) Complete the routing information in R1 and R3:
Destination network R1 exit interface R3 exit interface
(iii) Write down the IP configuration for PC-03 (IP address, subnet mask, default gateway).
(iv) Write down the default gateways for PC-04, and PC-05 respectively.
(a) Three major types of copper media used for computer networks are shown below. Identify each of them as
Coaxial, UTP, or STP cable respectively.
(b) Consider the figure below.
(i) Identify the types of cables (straight-through, crossover or rollover) that should be used for
Cable 1, Cable 2, Cable 3, Cable 4 and Cable 5 respectively. The annotation “N” stands for the
cable connected to a network interface card and “R” stands for the cable connected to an RS232
(ii) What is the name of the network device labelled A that provide wireless connection to the wired
(iii) What is the use of a wireless NIC adapter added to the computer labelled B?
(c) The Data Link Layer is divided into 2 sublayers abbreviated as LLC and MAC.
(i) Write out the full name of sublayer that communicates with the network layer.
(ii) Write out the full name of sublayer that defines the media access processes performed by the
(iii) What is the main difference between half-duplex communication mode and full-duplex
(d) The following diagram shows two typical physical LAN topologies. Name the two topologies.
(e) The generic frame contains Header, Packet, and Trailer:
Identify whether each of the following fields belongs to the Header or the Trailer: Addressing,
Control, Error Detection, and Type.
Refer to the Ethernet network below.
The routers interface settings are:
Logical Address Physical Address
RouterY-Fa0/1 192.168.20.1 3333.1111.1111
RouterY-Fa0/2 192.168.30.1 3333.1111.2222
RouterY-Fa0/3 192.168.0.1 3333.1111.3333
RouterZ-Fa0/1 192.168.30.2 44FF.FF11.1111
RouterZ-Fa0/2 192.168.40.1 44FF.FF11.2222
RouterZ-Fa0/3 192.168.50.1 44FF.FF11.3333
(a) Suppose that the ARP cache of PC4 is empty. Write down the contents of the cache after PC4 has sent
packets to PC1 and PC2 using the following format:
Internet Address Physical Address
(b) PC1 is sending a request to Server through the routers.
(i) What are the addresses labelled A1, A2, P1, and P2 in the diagram below that shows the Ethernet
frame reaching RouterY?
A1 A2 P1 P2 Data Trailer
(ii) What are the addresses labelled A3, A4, P3, and P4 in the diagram below that shows the Ethernet
frame between the routers?
A3 A4 P3 P4 Data Trailer
(iii) What are the addresses labelled A5, A6, P5, and P6 in the diagram below that shows the Ethernet
frame leaving RouterZ?
A5 A6 P5 P6 Data Trailer
(c) Suppose that the switching table in the Switch contains the following contents:
Fa1 Fa2 Fa3 Fa4
Open Open Open ------
Fa5 Fa6 Fa7 Fa8
BBBB.BBBB.BBBB ------ Open Open
(i) If a frame with source MAC address 3333.1111.3333 and destination MAC address
BBBB.BBBB.BBBB is received at the switch. At which port does the frame arrive? At which
port(s) will the frame go out?
(ii) If a frame with source MAC address BBBB.BBBB.BBBB and destination MAC address
AAAA.AAAA.AAAA is received at the switch. At which port does the frame arrive? At which
port(s) will the frame go out?
(a) Common protocols that we often use include DNS, DHCP, FTP, HTTP, SMTP, SNMP, TFTP,
Telnet, VoIP, and IPTV.
• Identify the protocol that translates a domain name into an IP address.
• Identify the protocol that dynamically assigns an IP address, subnet mask, default gateway and
DNS server to client stations at start-up.
• Identify 2 protocols that uses Transmission control Protocol (TCP).
• Identify 2 protocols that uses User Datagram Protocol (UDP).
(b) The following diagram shows the TCP connection establishment by using 3-way hand-shaking. Write
down the controls (C1, C2), and the values (V1, V2) in your answer book.
PC Web Server
SEQ = 105 C1 Received
Send SYN, ACK
SEQ = _V1_
SYN, ACK Received ACK = _V2_
SEQ = 106
ACK = 271
(c) (i) State the port numbers for HTTP and HTTPS.
(ii) How does HTTPS secure data?
(iii) List TWO common HTTP message types.
(d) In the start-up operation of Dynamic Host Configuration Protocol (DHCP), initial messages exchanged
between client and server include DHCP Offer, DHCP Acknowledge, DHCP Discover and DHCP
Request. Arrange these messages in the correct order.
NF0, NF7, NF8
(a) The network 22.214.171.124/24 is used to create 20 subnets for a company.
(i) What is the minimum number of bits that need to be borrowed for subnetting?
(ii) How many subnets are available?
(iii) What is the subnet mask in dotted decimal format?
(iv) What is the number of usable hosts in each subnet?
(b) A company with network topology below is using subnets with a subnet mask of /27 obtained from
(i) The subnets are listed in the table below, write down the value for entries A1 to A5.
Subnet Subnet address Usable IP address range Broadcast address
0 126.96.36.199 A1
Last A5 188.8.131.52
(ii) LAN F uses subnet 6, the last usable IP address is assigned to the LAN’s router interface. Suggest
an IP address configuration (IP address, subnet mask, default gateway) for a PC in LAN F.
(c) (i) Give a reason to explain why 184.108.40.206/28 not a valid host address.
(ii) Give a reason to explain why 220.127.116.11/28 not a valid host address.
(iii) For the host 18.104.22.168/21, write down the subnet address it belongs to and the broadcast
address of the subnet.
(d) An IPv6 address is written as a string of hexadecimal values.
(i) For the IPv6 address FE80:123::AB:245, how many hexadecimal zeros are represented by the
doubnle colon (::)? Determine the number of binary zeros represented by the double colon.
(ii) Given the IPv6 address 3F34:0000:0000:0000:0234:0000:1234:0055, abbreviate it to the shortest
(e) IPv6 unicast address types include global unicast, link-local, loopback, unspecified address, unique
local, IPv4 embedded. Identify the address type for each of the following addresses:
Solution to Exam Revision 2019 January
(i) PDU2 segment / PDU3 packet / PDU4 frame
(iii) physical, data link
(iv) 4 / transport
(v) network access
(ii) S0/0/0 Fa0/0
(iii) 22.214.171.124 / 255.255.255.0 /126.96.36.199
(iv) 188.8.131.52, 184.108.40.206
(a) STP / UTP / Coaxial
(i) crossover / straight-through / crossover / rollover / straight-through
(ii) Wireless Access Point
(iii) Provides wireless connection (to device A via Wi-Fi)
(i) Logical Link Control
(ii) Media Access Control
(iii) The devices can either transmit or receive on the media at one time in half-duplex.
The devices can transmit and receive on the media simultaneously in full-duplex.
(d) Star / Ring
(e) Header / Header / Trailer / Header
Internet Address Physical Address
(i) A1 3333.1111.3333 / A2 BBBB.BBBB.BBBB / P1 192.168.0.3 / P2 192.168.40.3
(ii) A3 44FF.FF11.1111 / A4 3333.1111.2222 / P3 192.168.0.3 / P4 192.168.40.3
(iii) A5 EEEE.EEEE.EEEE / A6 44FF.FF11.2222 / P5 192.168.0.3 / P6 192.168.40.3
(i) Frame arrive: Fa4 / Frame go out: Fa5
(ii) Frame arrive: Fa5 / Frame go out: Fa4/Fa6
(iii) Any 2: HTTP/FTP/SMTP/Telnet/DNS/SNMP
(iv) Any 2: DHCP/TFTP/VoIP/IPTV/DNS/SNMP
(b) C1=SYN / C2=ACK / V1=270 / V2=106
(i) 80, 443
(ii) HTTPS uses encryption and authentication to secure data
(iii) Any 2: GET/POST/PUT
(d) DHCP Discover / DHCP Offer / DHCP Request / DHCP Acknowledge
NF0, NF7, NF8
(a) 5 / 32 / 255.255.255.248 / 6
(i) A1 - 220.127.116.11 / A2 - 18.104.22.168 ~ 94 / A3 - 22.214.171.124 / A4 - 126.96.36.199 / A5 - 188.8.131.52
(ii) IP address : any address in range 184.108.40.206 ~ 221
Subnet mask : 255.255.255.224
Default gateway : 220.127.116.11
(i) 18.104.22.168/28 is a subnet address (16010 = 1010 00002)
(ii) 22.214.171.124/28 is a broadcast address (16010 = 1010 11112)
(iii) 16410 = 1010 01002
Subnet address is 126.96.36.199, broadcast address is 188.8.131.52
(d) 16 hexadecimal zeros = 64 binary zeros / 3F34::234:0:1234:55
(e) Loopback / Global unicast