CSSE4004 -Lecture 7

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Quiz by tb22, updated more than 1 year ago
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CSSE4004 -Lecture 7

Resource summary

Question 1

Question
An agreement on a faulty system cannot be reached in which scenario?
Answer
  • Unbounded, ordered, asynchronous, multicast
  • Unbounded, ordered, syncronous, multicast
  • Unbounded, ordered, asynchronous, unicast
  • Unordered, bounded, asynchronous, multicast

Question 2

Question
retransmission if packet lost is an example of
Answer
  • backward recovery
  • forward recovery
  • retry recovery
  • automated recovery

Question 3

Question
Which of the following is a drawback of using sequence numbers to prevent duplicates when retrying?
Answer
  • Results have to be stored for some time
  • Only works for idempotent requests
  • Sequence number can never reset and therefore eventually gets too big to store
  • Blocks intermediate processes from making calls while the failed call is reissued

Question 4

Question
What does the following describe "construct correct state from error state"
Answer
  • forward recovery
  • backward recovery
  • extrapolation
  • retransmission

Question 5

Question
What type of logging does "roll each process back to state where does not depend on delivery of message some process(es) do not yet have in stable storage" describe?
Answer
  • Optimistic logging
  • Pessimistic logging
  • Reliable logging
  • Transaction logging

Question 6

Question
Which of the following describes "virtual synchronous multicast"
Answer
  • sender crashes, deliver to all rest of processes or none
  • sender sends requests to three receivers and uses triple modular redundancy to detect errors
  • If sender has crashed by the time the receiver responds, the receiver selects a new node to deliver the response to
  • Multiple recievers are guaranteed to receive the message at exactly the same time

Question 7

Question
Which of the following does this describe "requires that an operation is performed by each member of a process group or none at all"?
Answer
  • distributed commit
  • atomic transactions
  • coordinated processing
  • synchronous computation

Question 8

Question
"server fails to receive incoming messages" is what type of failure?
Answer
  • Crash failure
  • Omission failure
  • Response failure
  • Timing failure

Question 9

Question
In which of the following M -> P scenarios will a crash result in a duplicate if calls are always reissued?
Answer
  • MC(P)
  • C(MP)
  • MPC

Question 10

Question
Which of the following does not offer Total-ordered Delivery?
Answer
  • Causal atomic multicast
  • FIFO atomic multicast
  • Atomic multicast
  • Reliable multicast

Question 11

Question
In which of the following P -> M scenarios will be okay if calls are reissued only when ACKed?
Answer
  • PMC
  • PC(M)
  • C(PM)

Question 12

Question
Which of the following is false about RPC?
Answer
  • Communication failures such as lost messages means RPC can't be completely transparent
  • It can be difficult to determine the difference between a failed message and a delayed reply
  • Reissuing RPC calls can have undesirable consequences
  • An RPC call can always be reissued because changes resulting from RPC call must be acknowledged

Question 13

Question
Is a hit counter on a website idempotent?
Answer
  • True
  • False

Question 14

Question
What is the minimum number of nodes required to detect 2 faulty nodes in Byzantine failures?
Answer
  • 5
  • 3
  • 7
  • 4
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