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CSC358 Tutorial 4 Notes

Below are some notes and sample solutions to the tutorial questions. These
notes are only meant to provide the necessary amount of information for you to
verify your own work and to help you recall the discussions in the tutorial.
Simply reading these solutions does NOT convey the same learning experience as
attending a tutorial (not even close). The tutorial materials are a mandatory
and important component of this course, so don't miss any of them!
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Question 1:

Review lecture slides for answers.

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Question 2

The receiver in protocol rdt2.2 will also work as the receiver in protocol rdt
3.0.

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Question 3

This problem is a variation on the simple stop and wait protocol (rdt3.0).
Because the channel may lose messages and because the sender may resend a
message that one of the receivers has already received (either because of a
premature timeout or because the other receiver has yet to receive the data
correctly), sequence numbers are needed. As in rdt3.0, a 1-bit sequence number
will suffice here.

In this problem, the sender state indicates whether the sender has received an
ACK from B (only), from C (only) or from neither C nor B. The receiver state
indicates which sequence number the receiver is waiting for.