Interactive end-of-chapter exercises

Reliable Data Transfer: RDT 3.0

Consider the RDT 3.0 protocol, for reliably communicating data from a sender
to receiver over a channel that can lose or corrupt packets in either direction,
and when the maximum delay from sender to receiver and back is not known. The
FSMs for the sender and receiver are shown below, with their transitions labeled
as SX and RY, respectively.

Now let’s consider the sequence of sender and receiver transitions that would
happen when one or more of the following complications occur: a packet
(data or ACK) is lost, a timer times out (prematurely or not), or a message is
corrupted. One or more of these events has occurred to produce the sequence
of transitions below. In the sequence below, one transition has been omitted
and replaced with a “*”.

Transition Sequence: S0, R0, S1, S2, *, S1, S2, R1, S3, S4, S5, R2, S6, S7, R3, S6, S7, R3, S6, S7, R3, S6, S7, R3, S6, S7, R3, S6, S7, R3, S8

Question List

1. What is the missing transition? To indicate the missing transition, enter S or R, followed by an index.

Solution

1. The missing transition is: R1

Transition Sequence: S0, R0, S1, S2, *, S1, S2, R1, S3, S4, S5, R2, S6, S7, R3, S6, S7, R3, S6, S7, R3, S6, S7, R3, S6, S7, R3, S6, S7, R3, S8

That’s incorrect

That’s correct

The answer was: R1

Question 1 of 1

What is the missing transition? To indicate the missing transition, enter S or R, followed by an index.

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