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CS601 - Data Communication Assignment No. 1 Solution And Discussion Fall 2013 Due Date: November 26, 2013

Assignment No. 01

(Non Graded)
Semester: Fall 2013

CS601-Data Communication

 

Total Marks: 20

 

Due Date: 26/11/2013

 

Uploading instructions:

 

  • Your assignment must be in Microsoft Word format. (Any other formats like scan images, PDF, Zip, rar, bmp, etc will not be accepted).
  • Save your assignment with your ID (e.g. bc020200786.doc).
  • No assignment will be accepted through email.

 

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It should be clear that your assignment will not get any credit if:

 

·         The assignment is submitted after due date.

·         The submitted assignment does not open or file is corrupted.

·         Your assignment is copied from internet, handouts or from any other student

      (Strict disciplinary action will be taken in this case).

Assignment

 

 

Question 1:   (10 Marks)

 

Which of the layer(s) of the OSI model perform(s) the following functions?

 

Sr. No.

Functions

OSI Layer(s)

1

Route determination

 

2

Reliable process to process delivery

 

3

Provides user services such as email and file transfer

 

4

Error correction and retransmission

 

5

Establishes, manages and terminates session

 

6

Defines frames

 

7

Transmission of bits across medium

 

8

Format and code conversion services

 

9

Ensures reliable transmission of data

 

10

Communicates directly with user’s application program

 

 
 

 

 

 

Question 2:   (10 Marks)

 

Discuss the consequences if a connection fails in each of the following five network topologies having four devices.

 

  1. Devices arranged in a mesh topology
  2. Devices arranged in a star topology (not including the hub)
  3. Devices arranged in a bus topology
  4. Devices arranged in a ring topology
  5. Devices arranged in a dual ring topology

 

 

NOTE: Every student should provide his/her own work, exact copying of the assignment (or some portion of the assignment) from the internet or other students will lead to copy case and zero marks will be awarded. Do not put any query on MDB about this assignment, if you have any query then email at cs601@vu.edu.pk.

 

 

 

Deadline: Your assignment must be uploaded/submitted on or before 26th November 2013.

 

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Discuss the consequences if a connection fails in each of the following five network topologies having four devices.

 

  1. 1.     Devices arranged in a mesh topology
  2. 2.     Devices arranged in a star topology (not including the hub)
  3. 3.     Devices arranged in a bus topology
  4. 4.     Devices arranged in a ring topology
  5. 5.     Devices arranged in a dual ring topology

 

 

 

 

a) Mesh Topology

If five devices arranged in a mesh topology so we will have 10 links and 4 I/O ports in each hardware device. If any link create problem so it will be easy to find out which one is affected and it does not effect on other links. But a bulk of wires can create problem in re-installation and re-configuration.

b) Star Topology

In Star topology each device has a point-to-point link to a Hub. In star topology the sending computer send the data to the hub. The hub sends the data to the receiving computer. Each computer in star network communicates with a central hub.

If a central hub fails the entire network breaks down. It’s required a large length of cable to connect the computer and is very expensive.

 

c) Bus Topology

In Bus topology, a backbone wire is connected with device and further taps and drop lines link the clients. If any link goes down so signals won’t pass on and get back to origin which will create noise on both sides. And if backbone wire is broken so the whole communication will be disabled. Its reconfiguration and modification is difficult than others. In bus topology a drawback is also that if number of computer increases network speed will slow down.

d) Ring Topology

In this topology each computer is connected to the next computer with the last one to the first computer. Thus a ring of computer is formed.

In ring topology each computer receives a message from a previous computer and translates it to the next computer. The message flow in one direction.  In ring topology failure of one computer affect the whole computer. It is difficult to troubleshoot. Adding and removing computer effect the the whole network.

Sr. No.

Functions

OSI Layer(s)

1

Route determination

Network

2

Reliable process to process delivery

Transport

3

Provides user services such as email and file transfer

Application

4

Error correction and retransmission

Transport

5

Establishes, manages and terminates session

Session

6

Defines frames

Datalink

7

Transmission of bits across medium

Physical

8

Format and code conversion services

Presentation

9

Ensures reliable transmission of data

Transport

10

Communicates directly with user’s application program

Note:

Datalink layer has the feature of error detection but it has no mechanism of error recovery. Error recovery in case of lost data is the responsibility of Transport layer. Transport Layer has many protocols but the two most widely used protocols are TCP and UDP. TCP is a connection oriented reliable transport layer protocol but UDP is a connectionless protocol.

Q1

1 - Route determination (page 48 - Function of Network Layer - Routing last point)
2 - Reliable process to process delivery (page 49 - Functions of Transport Layer - point 2)
3 - Provides user services such as email and file transfer (page 53 - Application layer - point 2)
4 - Error correction and retransmission (page 49 - Functions of Transport Layer )

do not get confused by error correction and error detection
error correction TL , errror correction DL

5 - Establishes, manages and terminates session (page 50 - session layer function - point 1and 2)
6 - Defines frames (page 46 - Physical Addressing framing (for concept) physical addressing - point 1)
7 - Transmission of bits across medium (page 45 - Function of physical layer - first heading point 3 and second heading point 1
8 - Format and code conversion services ( page 51 - diagram also for ref defination in book )
9 - Ensures reliable transmission of data (page 42 - organization of layers - point 1 (layer 4 that is Transport Layer)
10 - Communicates directly with user’s application program ( page 53 - application layer -


Session layer Determines how two devices establish, maintain and manage a connection – how they talk to each other.
while
Provides network services to user applications. Provides network services to the end-users. Mail, ftp, telnet, DNS, NIS, NFS are examples of some of the network applications it uses.

here teacher asked about user apps communication not devices communication

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