About TCPIP Data communication questions Question 4 (10 marks) Data

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about TCP/IP Data communication questions Question 4

(10 marks) Data Link Layer a) (2 marks Senders and

receivers have agreed to use even parity. Acting as a

sender, add a parity bit to the following bit sequences. 010

01100 011010 01100100 b) (2 marks) Senders and

receivers have agreed to use odd parity. Are the following

received bit sequences correct? 1001 010101 0110110

011101101 c) (3 marks) An ASCII transmission scheme

uses DLE STX control characters to start a frame and DLE

ETX to end a frame. Using character stuffing (hint: only

DLE needs to be escaped), what are the ASCII sequences

to transmit the following data streams? ABCD AB DLE STX

CD ABC ETX DLEDETX d) (3 marks) A bit-oriented

protocol uses the flag bits 011lli10 to start and end the

frame. What will be the transmitted frames for the following

streams of bits? 01010111000 01111110

00001110111110000111111111111110000

Solution

Odd parity

The total number of ones = odd

One single parity bit is appended to each block of data

Hamming distance for the parity bit = 2

(a)

010 will become 111

01100 will become 11100

011010 will become 111110

01100100 will become 11110100

(b)

1001 is not correct as the total number of ones are not

odd

010101 is correct as there are 3 ones - an odd number of

ones

0110110 is not correct as the total number of ones are not

odd

011101101 is not correct as the total number of ones are

not odd

(c)

Data Link Escape Start of TeXt = DLE STX

Data Link Escape End of TeXt = DLE ETX

We will use some reserved characters that will indicate the

begining and completion of

a data frame

DLE STX Frame begins Frame ends DLE ETX

As our data stream itself contains some DLE, we need to

replace each occurence of DLE with double DLE DLE

At the receiver end he/she will reverse the process of

converting the double DLE to a single DLE

Example: If the frame contained ``A B DLE D E DLE\'\',

the characters transmitted over the channel would

be ``DLE STX A B DLE DLE D E DLE DLE DLE ETX\'\'.

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about TCP/IP Data communication questions Question 4 (10 marks) Data Link Layer a) (2 marks Senders and receivers have agreed to use even parity. Acting as a sender, add a parity bit to the following bit sequences. 010 01100 011010 01100100 b) (2 marks) Se nders and receivers have agreed to use odd parity. Are the following received bit sequences correct? 1001 010101 0110110 011101101 c) (3 marks) An ASCII transmission scheme uses DLE STX control characters to start a frame and DLE ETX to end a frame. Using character stuffing (hint: only DLE needs to be escaped), what are the ASCII sequences to transmit the following data streams? ABCD AB DLE STX CD ABC ETX DLEDETX d) (3 marks) A bit -oriented protocol uses the flag bits 011lli10 to start and end the frame. What will be the transmitted frames for the following streams of bits? 01010111000 01111110 00001110111110000111111111111110000 Sol ...
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