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1. (1 pt) Under what conditions would an open-loop protocol
such as an error-correcting Hamming code be preferable to the feedback type
protocols discussed throughout this chapter?
2. (1 pt) Suppose that a stop-and-wait protocol was used on
a channel is 1 second propagation delay and sender frames of 10 seconds. The
receiver must fully receive the frame before sending an acknowledgment. The size
of the acknowledgment can be ignored. What is the channel utilization?
3. (1 pt) A channel has a propagation delay of 1
second. The receiver must fully receive the frame before sending an
acknowledgment. The size of the acknowledgment can be ignored. For what range of
frame sizes (in seconds) does stop-and-wait utilize at least 50% of the channel?
4. (4 pt) Using the below diagram, starting at 1 for each list the sender and receiver state numbers that would be entered given that:
Sender Receiver
5. (6 pt) The following diagram is based on the sender having a large number of buffers and the assumption that one error is not generally followed by another.
a) What is the cost in frames using this assumption when frames 1 and 2 in error and only 4 buffers are used by the sender?
b) Assume the sender has only 4 buffers. Make changes to the diagram to reflect where frame 1 is in error under the more conservative sender assumption that frames 1, 2, ... must be resent until an appropriate acknowledgment is received, that is resend 1, 2, 3, 4. What is the cost in frames of the error using the more conservative assumption?
c) Assume the sender has four buffers. What would be the effect of having 3 buffers (i.e. 2 for buffering and 1 for receive) on the receiver rather than 4? Make changes to the diagram.
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