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CSSE4004 -Lecture 7

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CSSE4004 -Lecture 7

Question 1 of 14

1

An agreement on a faulty system cannot be reached in which scenario?

Select one of the following:

  • Unbounded, ordered, asynchronous, multicast

  • Unbounded, ordered, syncronous, multicast

  • Unbounded, ordered, asynchronous, unicast

  • Unordered, bounded, asynchronous, multicast

Explanation

Question 2 of 14

1

retransmission if packet lost is an example of

Select one of the following:

  • backward recovery

  • forward recovery

  • retry recovery

  • automated recovery

Explanation

Question 3 of 14

1

Which of the following is a drawback of using sequence numbers to prevent duplicates when retrying?

Select one of the following:

  • 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

Explanation

Question 4 of 14

1

What does the following describe "construct correct state from error state"

Select one of the following:

  • forward recovery

  • backward recovery

  • extrapolation

  • retransmission

Explanation

Question 5 of 14

1

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?

Select one of the following:

  • Optimistic logging

  • Pessimistic logging

  • Reliable logging

  • Transaction logging

Explanation

Question 6 of 14

1

Which of the following describes "virtual synchronous multicast"

Select one of the following:

  • 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

Explanation

Question 7 of 14

1

Which of the following does this describe "requires that an operation is performed by each member of a process group or none at all"?

Select one of the following:

  • distributed commit

  • atomic transactions

  • coordinated processing

  • synchronous computation

Explanation

Question 8 of 14

1

"server fails to receive incoming messages" is what type of failure?

Select one of the following:

  • Crash failure

  • Omission failure

  • Response failure

  • Timing failure

Explanation

Question 9 of 14

1

In which of the following M -> P scenarios will a crash result in a duplicate if calls are always reissued?

Select one of the following:

  • MC(P)

  • C(MP)

  • MPC

Explanation

Question 10 of 14

1

Which of the following does not offer Total-ordered Delivery?

Select one of the following:

  • Causal atomic multicast

  • FIFO atomic multicast

  • Atomic multicast

  • Reliable multicast

Explanation

Question 11 of 14

1

In which of the following P -> M scenarios will be okay if calls are reissued only when ACKed?

Select one of the following:

  • PMC

  • PC(M)

  • C(PM)

Explanation

Question 12 of 14

1

Which of the following is false about RPC?

Select one of the following:

  • 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

Explanation

Question 13 of 14

1

Is a hit counter on a website idempotent?

Select one of the following:

  • True
  • False

Explanation

Question 14 of 14

1

What is the minimum number of nodes required to detect 2 faulty nodes in Byzantine failures?

Select one of the following:

  • 5

  • 3

  • 7

  • 4

Explanation

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