Question $4(2$ marks$)$: Student id $(1065450)$

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 $.$ Using the chart provided in the Annex, 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 of 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 $7$ ms $?$

c$)(0\mathrm{.}25$ mark$)$ What will happen if the sender uses a shorter timeout duration, let say $3$ ms $?$