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CSE 536
SPRING 96
MIDTERM 2
NAME
(33) 1. (24) (a)Show how each of the 6 entries in the table below is derived. You need to name the types of messages and from whom they go to and come from for the first two rows and the conditions which cause each of the four extremes in the last row. The answer for each entry is worth 4 points. (9) (b) Give a reason why each of the algorithms suffers badly in the event of crashes. Each answer is 3 worth points.
CSE 536 MIDTERM 2 SPRING 96
(16) 2. (4) (a) From the figure below list two sets of events which can be ordered by the relation and two events that are concurrent. (12) (b) Use Lamport's algorithm to correct the clocks where necessary in the figure below. Indicate your changes by crossing out times that need to be changed and writing the correct time next to it. Correct all logical clock times that need to be changed. (10) 3. In many layered protocols, each layer has its own header. Surely it would be more efficient to have a single header at the front of each message with all the control information in it rather than all these separate headers. Explain why this is not done. (2) 4. T or F Both sends and receives can be nonblocking. (8) 5. (3) (a) What class of failures that can occur in RPC creates grandorphans? (5) (b) What is a grandorphan? Why is it even harder to deal with grandorphans than orphans?
CSE 536 MIDTERM 2 SPRING 96
(3) (a)Why is multicasting better suited to support group communication than broadcasting? (2) (b) Why isn't multicasting used all the time? (5) (c)Distinguish between an open group and a closed group. In both cases state who can send messages to the group and who can send messages to individual members of the group. (5) (d)One knotty issue in handling group membership is that as soon as a process has left a group, it must not receive any more messages from the group and the group must not receive any more messages from it. Assuming that the process that leaves the group hasn’t left it because it crashed, suggest a way of making sure that a leave is integrated into the message stream at the right place.
- (3 pts. extra credit) Give an example of predicate addressing in group communication.
