Choose the statements below that are TRUE:

(I) Berkeleys algorithm for time synchronization obtains an average for all partici- pating computers.

(J) The 1st stratum in NTP servers is directly connected to accurate time sources.

(K) Messages in NTP bear timestamps of recent events.

(L) Logical clocks encode causality relationships.

(M) Two events a and b are concurrent if a does not happen before b, and b happens before a.

(N) If a total order is needed for logical clocks, we can tie breaks using ids. Page 2 of 3

(O) Logical clocks are total ordered.

(P) Happens Before relationship is total ordered.

(Q) An implementation of vector clocks requires vectors of length n, equal to the number of processors.

(R) Matrix clock tells me what I know about what other people know.

(S) The Centralized Algorithm for Mutual Exclusion satisfies ME1 and ME3, but not ME2.

(T) The Token Ring Algorithm for Mutual Exclusion satisfies ME1, and ME2, but not ME3.

(U) Ricart and Agrawala Algorithm assumes that all processors have distinct numeric IDs and maintain logical clocks.

(V) In Maekawa Algorithm, processes need only obtain permission to enter from sub- sets of their peers.

(W) Deadlocks are possible in Maekawa Algorithm.

(X) In the Bully Algorithm for Leader Election, a process sends and election message to all processes with higher IDs.

(Y) In the Chang and Roberts Algorithm, if a process sends a message, it marks its state as a participant.

(Z) In Paxos, Acceptors are processes that remember the state of the protocol.

(AA) In Phase 1a of Paxos, a Proposer (leader) creates a proposal number N where N is greater than any previous proposal number used by this proposer.

(AB) In Phase 2a of Paxos, if proposer receives enough promises it set a value v to the proposal, where v can be max(previous values).

(AC) Zookeper is a highly available, scalable, multi-dimensional, distributed system.

(AD) Zookeper provides consensus, group membership, leader election and naming.

(AE) Zookeper provides a file API without partial reads/writes.

(AF) The hierarchical namespace in Zookeper contains znodes.

(AG) A znode in Zookeper has data and no children. Page