CS450 SAMPLE TEST/REVIEW
(1) (15 pts) Apply Dijkstra’s Algorithm to find the shortest paths from vertex 4 to every other vertex of
the following graph. Show all your work including the final Distance Vector!
(2) (10 pts) Describe the step-by-step process of UDP programming in Java.
(3) (5 pts) Briefly describe how CSMA/CA work.
(4) (5 pts) Differentiate slotted ALOHA from pure ALOHA. Describe why channel utilization efficiency
is better in slotted ALOHA than that in pure ALOHA.
(5) (8 pts) What is the main argument against static channel allocations? Give two examples of static
channel allocation.
(6) (7 pts) A new protocol similar to Ethernet is being proposed. Given that the maximum cable length
is 2 km and the minimum frame size is 32 Kbits, calculate the allowable propagation delay (in
nanosec/m) that is required by this protocol at a data rate of 10Mbps.
(7) (10 pts) Describe each of the following CSMA protocols: 1-persistent, non-persistent, and p-
persistent. Which of these protocols provides the best throughput? Why?
(8) (5 pts) In the Basic Bit-map Protocol, the efficiency for low load is d/(N + d), where d is the
number of data bits and N is number of bit contention slots. Describe how the measure of efficiency
came about, i.e. explain the meaning of the mathematical expression.
(9) (5 pts) Describe how the Adaptive Tree Walk protocol works.
(10) (5 pts) Describe the Binary Exponential Backoff algorithm.
(11) (7 pts) Describe why the transmission range of a 802.11b signal is larger than that of 802.11a.
Describe why 802.11a have a higher data rate than that of 802.11b.
(12) (8 pts) Differentiate the two modes of 802.11 operations: Distributed Coordination Function
(DCF) and Point Coordination Function (PCF).
(13) (10 pts) Describe each of the following 802.11 modulation techniques: FHSS, DSSS, OFDM.
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