Question $4(2$ marks$)$:

My student id:$1082079$

The Trivial File Transfer Protocol $($TFTP$,$ RFC $1350)$ is an application layer protocol that

uses the Stop$-$and$-$Wait protocol. To transfer a file from a server to a client, the server

breaks the file into blocks of $512$ bytes and sends these blocks to the client using Stop$-$

and$-$Wait ARQ. Assume that the transmission time of one block is $1$ ms $,$ and that of an

acknowledgment is $1$ ms $.$ Assume also that the sender uses a timeout value of $4$ ms $.$ Show

the pattern of transmissions and associated state transitions for the following sequence

of events:

the server transmits $7$ blocks.

If your student ID is EVEN the $2^("$nd $")$ block is lost and the acknowledgment of the $3^("$rd $")$

block $($not counting any resubmission$)$ is lost.

If your student ID is ODD the $3^("$rd $")$ block is lost, and the acknowledgment of the $4^("$th $")$

block $($not counting any resubmission$)$ is lost.

a$)(1$ mark$)$ Draw the flow control in the chart provided in the following page. Describe

in detail how the sender and the receiver will behave. Your graphs must show the

sliding windows, the sequence number of the frames, and any special action

performed by the sender and the receiver $($e$.$g$.,$ Discard the frame, initiate a timer,

timeouts $...)$ as we have shown in the slides.

b$)(0\mathrm{.}25$ mark$)$ What will happen if the sender uses a longer timeout duration, let say

$6$ ms $?$

c$)(0\mathrm{.}25$ mark$)$ What will happen if the sender uses a shorter timeout duration, let say

$2$ms$?$

$2$

$13.$

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$116.$

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$26.$

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$24.$

$29.$