Show that the FIFO-ordered multicast algorithm does not work for overlapping groups, by
considering two messages sent from the same source to two overlapping groups, and considering
a process in the intersection of those groups. Adapt the protocol to work for this case. Hint:
processes should include with their messages the latest sequence numbers of messages sent to all
groups.
What will be an ideal response?
Let p send a message m1 with group-specific sequence number 1 to group g1 and a message m2 with group
specific sequence number 1 to group g2. (The sequence numbers are independent, hence it is possible for two
messages to have the same sequence number.) Now consider process q in the intersection of g1 and g2. How
is q to order m1 and m2? It has no information to determine which should be delivered first.
The solution is for the sender p to include with its message the latest sequence numbers for each group that it
sends to. Thus if p sent m1 before m2, m1 would include
had missed a message if it received m2 first.
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In terms of the queuing model, __________ is the total time that the item spends in the system (waiting time plus service time).
Fill in the blank(s) with the appropriate word(s).
Can you think of techniques other than chaining to handle bucket overflow in external hashing?
What will be an ideal response?