Communication Networks - Individual Assignment

This assignment covers topics such as line encoding, cyclic redundancy code, character overhead, Dijkstra's algorithm, and Bellman-Ford algorithm. It includes answers to questions and calculations with references from various books.

Running Head: COMMUNICATION NETWORKS 0
Communication Networks
Individual Assignment
Student name

Communication Networks 1
Table of Contents
A Answers.......................................................................................................................................1
Answer-1......................................................................................................................................1
Answer 2-(a)................................................................................................................................2
Answer 2-(b)................................................................................................................................2
Answer-3......................................................................................................................................3
Answer 4-(a)................................................................................................................................4
Answer 4-(b)................................................................................................................................5

Communication Networks 2
Communications Networks
Assignment 2
A Answers
Answer-1
Line encoding is use for secure data.1 Line coding scheme have five types according to different
levels, such as unipolar, polar, bipolar, multilevel, and multitransition. In this question, Non-
return to zero is a type of unipolar, Manchester encoding is considered in polar coding. Bipolar
line encoding has alternate mark invert and pseuddoternary coding. In this given bit stream
01001110, we applied different line encoding. In below figure, I sketch the waveform for the
following codecs:
 NRZ-L
 NRZ-I
 Bipolar AMI
 Pseudo ternary
 Manchester
I take positive voltage for zero and zero voltage for signal 1.2
1 William Stallings, Data and Computer Communication (Pearson Education, 8th ed, 2007).
2 Forouzan A. Behrouz, Data Communications and Networking (Tata McGraw-Hill Education,
2006).

Communication Networks 3
Answer 2-(a)
Cyclic Redundancy Code is an error detection scheme, in which we take a pattern for sending
data with some edition bits. Given pattern is P(x) = X4 + X + 1.
We used that pattern for dividing polynomial.
A message bit is this 10010011011, and it is our dataset.
We have to find Frame Check Sequence bits to be added in the end of dataset to make the
message complete for transmission of message in the channel.
Cyclic Redundancy Code is an error detection scheme3.
For finding added bit divide X10 + X7 + X4 + X3 + X + 1 by X4 + X + 1.
The remainder is X3 + X2.
Additional bits are 1100.
So finally, after the attachment of 1100 into 10010011011 final dataset will be send in the
channel is 100100110111100.4
Answer 2-(b)
When we transmit the signal over the channel then because of attenuation, distortion, and noise,
some bits are changed and that was an erroneous signal. As per question, we received a bit
stream that is 000110110111100.
According to received bits X11 + X10 + X8 + X7 +X5 + X4 + X3 + X2.
We divide this polynomial by X4 + X + 1.
The remainder after division is X3 + X2 + X.
Reminder is not zero. Therefore, it means error is detected in the received dataset.5
3 David Salomon, Coding for Data and Computer Communications, (Springer Science &
Business Media, 2006)
4 Jiw Wang, Computer Network Security, (Springer, 2009)
5 Douglas Comer, and Ralph E. Droms, Computer Networks and Internets (Prentice-Hall, 2003)

Communication Networks 4
Answer-3
Each character has 2 bits extra for start and stop bit as an overhead.
Given character, type is 7-bit IRA. For transferring 10,000 IRA characters, we need more bits.
There are 20,000 extra bits are used for data transfer6.
It takes extra time to transfer a frame, according to extra bits,
20000/2400 = 8.33 seconds.
It means more 8.33 seconds required for transfer the message.
For transmission of additional bit it required extra time, so additional bits are divided by speed of
data transfer.
480/2400 = 0.2 seconds
Total overhead bits are remaining same as previous but time would be changed by factor of four.
9600/2400=4.7
6 Wayne Tomasi, Introduction to Data Communications and Networking, (Pearson Prentice Hall,
2005)
7 William Stallings, Data and Computer Communication (Pearson Education, 8th ed, 2007).

Communication Networks 5
Answer 4-(a)
Consider the network in below Figure
Dijkstra’s algorithm is a Greedy algorithm and it is used for negative weight. 8.
Iteration T L(2) Path L(3) Path L(4) Path L(5) Path L(6) Path
1 {1} 1 1-2 ∞ - 4 1-4 ∞ - ∞ -
2 {1, 2} 1 1-2 4 1-2-3 4 1-4 2 1-2-5 ∞ -
3 {1, 2, 5} 1 1-2 3 1-2-5-3 3 1-2-5-4 2 1-2-5 6 1-2-5-6
4 {1, 2, 5.,3} 1 1-2 3 1-2-5-3 3 1-2-5-4 2 1-2-5 5 1-2-5-3-6
5 {1, 2, 5, 3, 4} 1 1-2 3 1-2-5-3 3 1-2-5-4 2 1-2-5 5 1-2-5-3-6
6 {1, 2, 5, 3, 4, 6} 1 1-2 3 1-2-5-3 3 1-2-5-4 2 1-2-5 5 1-2-5-3-6
8 Andrew S Tanenbaum, Structured Computer Organization, (Pearson Education India, 2016)

Communication Networks 6
Answer 4-(b)
Consider the network in below Figure and calculate systematic cost change according to
bellman-ford algorithm.
Table shows least-cost paths of given graph.9
h Lh(2) Path Lh(3) Path Lh(4) Path Lh(5) Path Lh(6) Path
0 ∞ - ∞ - ∞ - ∞ - ∞ -
1 1 1-2 ∞ - 4 1-4 ∞ - ∞ -
2 1 1-2 4 1-2-3 4 1-4 2 1-2-5 ∞ -
3 1 1-2 3 1-2-5-3 3 1-2-5-4 2 1-2-5 6 1-2-3-6
4 1 1-2 3 1-2-5-3 3 1-2-5-4 2 1-2-5 5 1-2-5-3-6
Bellman-ford algorithm is used for finding shortest path from a vertex to all other vertices of a
weighted graph.10
9 Oliver C Ibe, Fundamentals of Data Communication Networks, (John Wiley & Sons, 2017)
10 William Stallings, Data and Computer Communication (Pearson Education, 8th ed, 2007).

Communication Networks 7
BIBLIOGRAPHY
A Book
Comer, Douglas, and Ralph E. Droms, Computer Networks and Internets (Prentice-Hall, 2003)
Forouzan A. Behrouz, Data Communications and Networking (Tata McGraw-Hill Education,
2006)
Oliver C Ibe, Fundamentals of Data Communication Networks (John Wiley & Sons, 2017)
Salomon, David, Coding for Data and Computer Communications (Springer Science & Business
Media, 2006)
Stallings, William, Data and Computer Communication (Pearson Education, 8th ed, 2007)
Tanenbaum, Andrew, Structured Computer Organization (Pearson Education India, 2016)
Tomasi, Wayne, Introduction to Data Communications and Networking, (Pearson Prentice Hall,
2005)
Wang, Jie, Computer network security, (Springer, 2009)