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Faculty of Information Technology
Department of Computer Science
Philadelphia University
Lecturer : Dr. Hasan Al-Refai
Coordinator : Dr. Hasan Al-Refai
Internal Examiner:
Examination Paper
Fundamentals of Computer Networks
3rd Semester of academic year 2010/2011
Section :-1
Date: Aug, 16, 2011
Final Exam
Time: 120 minutes
Information for Candidates
1. This examination paper contains Five questions, totaling 50 marks.
2. The marks for parts of questions are shown in round brackets.
Advice to Candidates
1. You should attempt all questions.
2. You should write your answers clearly.
Basic Notions
Part I:
Objectives: Objectives: The aim of the question in this part is to evaluate your required minimal knowledge about the
computer networks in general.
Question 1: Choose the most appropriate answer of the following:
( 30 Marks, 1 M each 2 M Bonus)
1) Messages that are intended for all computers on a network are sent as:
a) Loopback
b) Broadcast
c) Broadband
d) Multicast
2) The topology that each device has a dedicated point–to–point line configuration only with the two
devices on either side of it is called:
a) Bus Topology
b) Mesh Topology
c) Star Topology
d) Ring Topology
3) An IP address is a___________ binary number usually represented as 4 decimal values
a) 34 bits
b) 48bits
c) 32 bits
d) 44 bits
4) What is the class of the IP-address 200.200.10.30?
a) Class A.
b) Class B.
c) Class C.
d) Class D.
5) Which network device is used to connect two network segments on the data link layer level?
A. Router
B. Gateway
D. Hub
C. Switch
6) The four numbers in an IP address are called:
A) subnet
C) hosted
B) netid
D) octets
7) Which of the following is a valid IP address:
A. 191.0.0.1.0
C. 262.101.10.21
B. 253.0.0.244
D. 167.10.269.10
8) The main difference between a hub and a switch is
A. switch does routing while a hub does not
B. switch increases traffic on the network while a hub
C. a switch forwards packets to the correct port while hub transmit packets to all ports
D. a switch amplifies the signal while hub does not
9) The most valuable function a bridge performs is frame filtering, that’s it , a bridge dose not forward a
frame unless necessary.
A) True
B) False
10) What is a broadcast IP address?
A. IP address with all hosts bits set to zero
C. IP address with all network bits set to 1
B. IP address with last byte set to 255
D. IP address with all host bits set to 1
11) Which of the following assumed as a rule that govern the use of repeaters which applied only to
Ethernet in a bus topology.
A) Half-duplex rules
C) IEEE rules
B) Full-duplex rules
D) 3-4-5 rule
12) Which of the following is correct regarding a ring LAN?
a) If any link is cut, then the NW fails.
c) It can be used only within a building.
b) Collision is possible.
d) It is highly secured.
13) What is the class of the IP-address 10001000110011001111110011110000?
a) Class A.
b) Class B.
c) Class C.
d) Class D.
14) The physical layout of a network is called its:
A) Segmentation
B) Structure
C) Topology
D) Network architecture
15) Which of the following network topologies don't have transmission media?
A) Bus
B) Star
C) Mesh
D) All of them
16) The default subnet mask of class C is:
A) 255.255.255.0 B) 255.255.255.255
C) 255.255.0.24
D) None of the above (Specify:______)
17) A ____enables the separation of a local network into distinct segments while retaining the broadcast domain.
A) Active hub
B) Switch
C) Bridge
D) Repeater
18) Central facility in star-shaped network and operates like a set of bridged segments.
A) Hub
B) Switch
C) Bridge
19) If the number of hosts in class C is 14, then the block size is:
A) 8
B) 16
C) 12
D) 32
D) Repeater
20) Multiplexing used to extracts data from shared channel and sends to correct destination.
A) True
B) False
21) In frequency division multiplexing, Guard bands prevent interference between channels.
A. True
B) False
22) In case of baseband, the transmission uses single frequency so no modulation needed.
A. True
B) False
23) The IP address 255.255.255.255 is reserved to be used for broadcasts.
A) True
B) False
24) By using VLSM design, we save address space.
A) True
B) False
25) Hubs operate using a broadcast model and switches operate using a multicast model.
A) True
B) False
26) In frequency division multiplexing, the pairs converse in turns which sharing the same medium and
have time in which to say something and give others a chance to converse, too.
A) True
B) False
27) ________ is a single piece of cable that forms a bus network.
A) Repeater
C) Router
B) Segment
D) Hub
28) A ________ is a multiport repeater that propagates each incoming signal to all connections, low cost
than repeater.
A) Hub
C) Bridge
B) Switch
D) None of the above
29) A repeater can be used to decrease a network’s size, it can, at the same time increase the network’s
performance.
A) True
B) False
30)________ can be interconnected in a daisy chain that operate as one giant hub which called stacking.
A) Repeater
C) Demultiplexing
B) Bridge
D) Multi-hub
31) Which of the following IP addresses is used as the loopback address.
A) 255.255.0.0
C) 191.0.1.1
B) 127.0.0.1
D) 0.0.0.0
32) Bridge operates at which layer of OSI reference model:
A) Transport layer
C) Physical Layer
B) Network layer
D) Data link layer
Question 2:
How can a bridge know which computers are attached with which segments?
Ans.:
•
Most bridges are called adaptive or learning bridges because they learn the locations of computers
automatically.
•
To do so, a bridge uses source address information in the frames that arrive.
•
When a frame arrives, the bridge extracts the physical source address from the frame header, and
adds the address to a list of computers attached to the segment.
•
Of course, the bridge must then extract the physical destination address from the frame, and use the
address to determine whether to forward the frame.
Question 3:
Discuss the three types of satellite, give example for each.
(6 Marks)
Answer:
Geostationary Earth Orbit (GEO): Thousand miles (36000km) above the earth. The speed of satellite rotation
around the earth is same as that of the earth. Thus its location seems fixed with respect to earth.
Low Earth Orbit (LEO): A few miles (200 to 400 miles) above the earth. The speed of satellite rotation around the
earth is lesser or higher than that of the earth. Because of this, more than one LEO satellites are required.
Medium Earth Orbit (MEO): These satellites are at an altitude of 18000 km above the earth. The speed of
satellite rotation around the earth is less than that of the earth. These are generally not used for communication
purpose.
Question 4:
The octets serve a purpose other than simply separating the numbers, Explain?
Ans.:
They are used to create classes of IP addresses that can be assigned to a particular business,
government or other entity based on size and need. The octets are split into two sections: Net and
Host. The Net section always contains the first octet. It is used to identify the network that a
computer belongs to. Host (sometimes referred to as Node) identifies the actual computer on the
network.
Unfamiliar Questions:
Objectives: Objectives: The aim of the question in this part is to evaluate your required knowledge about the
computer networks in depth for routing mechanizes and subneting mask..
Question 5:
( 10 Marks)
By using VLSM design, if you know that the number of subnets is 11, do the following:
A- Construct a suitable network design with a minimum number of routers in case of both subnet mask for
networks and routers are the same, assume that the IP address is 192.68.12.8.
B- Construct a suitable network design with a minimum number of routers in case of both subnet mask for
networks and routers are different, assume that the IP address of subnets is 192.68.12.8 and routers is
192.68.12.6