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| 1-3. |
Suppose that A is connected to B through an intermediate
router R. The A-R and R-B links each accept and transmit
only one frame per second in each direction (so two
packets take two seconds). The two directions transmit
independently. Assume A sends to B using the sliding
window protocol with send window size (SWS) equal to
4.
- For Time t=0,1,2,3,4,5, state what packets arrive
at and leave from each node and label them on a
timeline.
- What happens if the links have a propagation delay
of 1.0 seconds, but accept immediately as many packets
as are offered (i.e., latency= 1 second and bandwidth
is infinte)?
- What happens when A-R link is instantaneous, but
the R-B link transmits only one packet each second,
one at a time (so two packets take 2 seconds). Assume
A sends to Busing the sliding window protocol with SWS=4.
For time = 0 1, 2, 3, 4, state what packets arrive
at and are sent from A and B. How large does the
queue at R grow?
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| 4. |
Suppose that you design a sliding window protocol for 1
Mbps point-to-point link to the moon, which has one-way latency
of 1.25 seconds. Assuming that each frame carries 1KB of data,
what is the minimum number of bits you need for the sequence
number? |
| 5-7. |
Frames of 1000 bits are sent over 1 Mbps channel using a
geostationary satellite whose propagation time from the earth
is 270msec. Acknowledgements are always piggybacked onto data
frames. The headers are very short. Three bit sequence numbers
are used. What is the maximum achievable channel utilization
(a) the stop-and-wait protocol, (b) the go back N
protocol and (c) the selective repeat protocol. |
| 8. |
Consider an error-free 64-kbps satellite channel used to
send 512-byte data frames in one direction, with very short
acknowledgements coming back the other way. What is the maximum
throughput for window sizes of 1, 7, 15, and 127? The earth-satellite
propagation delay is 270 msec. |
| 9-10. |
Describe the Finite State Machine that captures the behavior of the Stop-and-Wait protocol. The state definition has been given in the class. |
| 11-12. |
Describe the Petri Net model that captures the behavior of the Stop-and-Wait protocol. The state definition has been given in the class. |
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