Assignment No. 1, Dcc.docx

ASSIGNMENT NO. 01 CHAPTER 01

“INTRODUCTION TO DATA COMMUNICATION”

EXERCISE: Question no. 16. Assume six devices are connected in a mesh topology. How many cables are needed? How many ports are needed for each device? Answer: Given that six devices are connected in mesh topology so:

D2 D3

D1

D4 D6 D5

Cables: Links = n(n-1)/2 = 6(6-1)/2 = 30/2 = 15 cables Ports: Ports = n – 1 =6–1 = 5 ports Six devices connected in mesh topology will need 15 cables and 5 ports.

Question no. 17: For each of the following four networks, discuss the consequence if a connection fails. a) Five devices are arranged in mesh topology. Ans: Every device has a dedicated point-to-point link to every other device in mesh topology. If a connection fails in mesh topology, it does not incapacitate the entire system. Thus in five devices if a connection fails then the other four cannot be affected or disturbed. b) Five devices are arranged in star topology. Ans: Every device has a dedicated point-to-point link only to a central controller in star topology. If a connection fails in star topology only that connection is affected. All other links(connections) remains active. Thus in five devices if a connection fails then the other four remains active. c) Five devices are arranged in bus topology. Ans: As in bus topology one long cable acts as a backbone to link all the devices in a network. If backbone connection fails in bus topology stops all transmission, even between devices on the same side of the problem. The damaged area reflects signals back in the direction of origin, creating noise in both direction. Therefore, five of the five devices will get damage, if backbone connection fails. d) Five devices are arranged in ring topology. Ans: In ring topology, each device has a dedicated point-to-point connection with only two devices on either side of it. If five devices are arranged in a ring topology and a connection fails then it can disable the entire network.

Question no. 18: You have two computers connected by an Ethernet at home. Is this a LAN, a MAN or a WAN? Explain your reason. Ans: This network is a local area network i.e. LAN because the LAN is usually privately owned and we have two computers are connected by an Ethernet and single house, office or building. LAN are designed to allow resources to be shared between personal computers or work stations. Question no. 19: In the ring topology in Fig 1.8, what happens if one of the station is unplugged ?

Ans: There are two types of unplugging in ring topology. If one station is unplugged without bypassing the link then the whole system would be disabled. Secondly if we bypass the link to the unplugged station the system will work but the number of devices will become five. Question no. 20: In the bus topology in Fig 1.7, what happens if one of the station is unplugged ? Ans: If a connection of the station is unplugged then the connection two only that station will be affected. It won’t affect the whole system. Question no. 21: Draw a hybrid topology with a star backbone and three ring networks.

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Question no. 22 : Draw a hybrid topology with a ring backbone and two bus network.

end

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station

station Repeater

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station

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Question no. 23 : Performance is inversely related to delay. When you use the internet which of the following applications are most sensitive to delay? a) Sending an E-mail. Ans. Sending an E-mail is not highly sensitive to delay, once a message is sent, it remains in the inbox for a while. b) Copying a file. Ans. Copying a file is not very sensitive to delay and it is less sensitive to delay then surfing the web and sending an email. c) Surfing the internet. Ans. Surfing the internet is the application very sensitive to delay. Because it is very sensitive to interactive application and users demand immediate results. Question no. 24: When a party makes a local telephone call to another party, is this a pointto-point or multipoint connection? Explain your answer. Ans. This is a point-to-point connection because it provides a dedicated link between two devices. In our condition a party makes a local call to another party, so this is point-to-point

connection and there is no other connection between these two calls so it is point-to-point connection. Question no. 25 : Compare the telephone network and the internet. Ans. Following are the differences and the similarities of telephone network and the internet.

Differences: 1. Telephone has only voice sharing, it can only enables voice communication while internet has file sharing system, voice and video chat. 2. Telephone –circuit switched network, while internet-packet switched network.

Similarities: 1. Both are the source of communication. 2. Both are the two-way communication. 3. Both has wired/wireless capabilities.