ASSIGNMENT # 1
Data Communication
Fall 2004
Assignment No. 1
Total Marks: 100
Each question carries 10 Marks
Do your own work. If two solutions are found similar, no credit will be allocated to any
of the students.
Q. 1: Give two reasons for using Layered Protocols?
Q. 2: Protocol defines three Questions:
What is communicated?
How it is communicated?
When it is communicated?
Relate these questions with key elements of protocol and explain them?
The Key elements of Protocol are:
Syntax
what is communicated?
It refers to the structure of data It includes data format, coding and signal levels
Semantics
how it is communicated?
It refers to the meaning of each section of bits. It includes control information for
coordination and error handling
Timing
when it is communicated?
It refers to the time that when data should be sent. It includes speed matching and
sequencing.
ASSIGNMENT # 1
Q.3: List two advantages and disadvantages of having international standards for
network protocols?
Q. 4: When a system has a permanent part and a removable part (such as a CDRom drive and a CD-Rom), it is important that the system be standardized, so that
different companies can make both the permanent and removable parts and every
thing still works together.
Give three examples outside the computer industry where such international
standards exist. Now give three areas outside the computer industry where they do
not exist.
Q. 5: Make a list of activities that you do every day in which computer networks are
used. How would your life be altered if these networks were suddenly switched off?
ASSIGNMENT # 1
Ever student will have a different approach.
Q. 6: The Internet is made up of a large number of networks. Their arrangements
determine the Topology of the Internet. A considerable amount of information
about the Internet Topology is available on-line. Use a search engine to find out
more about the Internet Topology and write a short report summarizing your
findings?
Ever student will have a different approach.
Q. 7: Discuss the importance of Timeliness in Data Communication with the help of
an example?
(Better NEVER than LATE)
Timeliness is the most important in Data Communication. The data should be delivered
within a specific time. Failing to deliver the data at the right time will make the data
useless for the receiver.
For example if one person is some important documents from Karachi to Islamabad that
require to be received within two days. If the documents are received after one week then
the delivery of the mail becomes unimportant to the receiver.
In Data Communication especially in case of video, audio and voice data the delivery
should me in same order within specific time.
Q8. Write the correct Transmission Mode for each way of communication?
Key boards, Monitors, Walkie-Talkies, Telephones, CB radio is half duplex
Key boards
Simplex
Monitors
Simplex
Walkie-Talkies
Half Duplex
Telephones
Full Duplex
ASSIGNMENT # 1
CB radio
Half duplex
Q. 9: Identify the topology in the following diagram and justify your answer?
A
A
A
A
A
It is a Mesh Topology because every computer is connected to every other computer
(point to point).
Q10. Assume six devices arranged in a mesh topology. How many cables are
Needed .How many ports are needed for each device?
A fully connected mesh network has n (n-1)/2 physical channels to link n devices. Every
device on the network must have n-1 input/output ports
Number of cable= n (n-1)/2 = 6(6-1)/2= 15
Number of ports per device = n-1= 6-1= 5
So15 cables and 5 ports per device are needed to arrange six devices in mesh Topology
NOTE: Don’t worry about Q8.