Homework Assignment $1$: $($Flow Control and Error Detection$)$

Due: $5$:$00$pm$,$ Friday, $8/30/24.$

Instructions: Print this, write your answers by hand in the space provided, then scan and submit an electronic copy in Canvas. Late submissions may not be accepted. The credit for all questions and parts are indicated on the right.

With respect the functions of different layers in the TCP$/$IP protocol stack, briefly answer the following:

a$)$ What is meant by segmentation? State two benefits of segmentation.

b$)$ In which layers do the following functions performed:

IP addressing:

Wifi access:

Does the link utilization in stop$-$and$-$wait flow control increase or decrease with increasing values of each of the following:

$5$

a$)$ Frame length $($L$)$

b$)$ Link distance $($d$)$:

Provide technical explanations for the above based on the analysis done in class.

Assume that the maximum link utilization using the stop and wait flow control scheme in a certain link is $50\%.$ If the frame size $(L)$ is doubled keeping all other parameters same, how will the link utilization change?

$4$

Use a sketch to explain why the sliding window flow control method can achieve higher link utilization in comparison to stop$-$and$-$wait flow control.

$[5]$

Consider that a frame consists of one character of $4$ bits. Assume that the probability of bit error is ${10}^{-2}$ and that it is independent in each bit.

$2+5$

a$)$ What is the probability that the received frame contains at least one error?

b$)$ Now assume that one parity bit is added, making the total bits in the frame to be increased to $75.$ What is the probability that the frame is received with errors that are not detected?

A CRC is constructed to generate a $4-$bit FCS for an $11-$bit message using a generator pattern $P=11001$

$5+3+2+5$

a$)$ Find the frame$-$check sequence $($FCS$)$ for the data bit sequence $10010011011.$

b$)$ Determine the transmitted codeword. Clearly state which is your LSB$.$

c$)$ Sketch the shift$-$register circuit for the encoder

d$)$ Now assume that the channel introduces an error pattern $100010000000000($i$.$e$.$ positions $1$ and $5$ are flipped in the received frame$).$ What is received? Can the errors be detected?