CS$2$IDS

Answer ALL Questions

Question $1$:

$(25$ marks$)$

a$.$ A master node is synchronising its clock with three slaves employing Berkeley's algorithm. The master's clock reads $14$:$26$:$44$ when it sends the request, and three slaves' clocks read their current time $14$:$26$:$19,14$:$26$:$30$ and $14$:$26$:$55$ respectively, when they reply to the master. Calculate the Average Time Difference$/$Offset$,$ Correct Time at master, and Time Correction for all the slaves to synchronize their clocks using Berkeley's Algorithm.

$(10$ marks$)$

b$.$ A client is employing NTP protocol to synchronize its clock. The client sends an NTP request packet to the time server at $17$:$43$:$12.$ This request packet is received by the time server at $17$:$43$:$20.$ Subsequently, the time server sends a response packet back to the client at $17$:$43$:$26.$ Finally, the client receives the response packet from the server at $17$:$43$:$24.$ Calculate the RTT$,$ Clock Skew$/$Offset Time and Synchronised Time on the client using NTP protocol. $(10$ marks$)$

c$.$ A client is employing Cristian's algorithm to synchronize its clock. The client's clock reads $11$:$54$:$36$ when it sends the request, the server's clock reads current time $11$:$54$:$44$ and sends this time to the client, the client receives the reply at $11$:$54$:$46$ based on its clock. Calculate the time on the client after synchronizing the clock using Cristian's Algorithm. $(5$ marks$)$ Note: No marks will be awarded for only writing the final answers. $q,$

Question $2$:

$(25$ marks$)$

a$.$ Using the given Lamport's clock diagram, determine the Lamport's clock value $($Counter$/$TS$)$ of each event on the process $P$ and $Q,$ when:

Counter$/$TS for each internal$/$local event on the $P$ and $Q$ is incremented by the value $4.$

Counter$/$TS for each external event$/$received message event on the $P$ and $Q$ is incremented by local$\_$counter, received$\_$counter$)+1.$

$(8$ marks$)$

Note: All the calculated values should be written using the same diagram.

Page $1$ of $3$

May $2024$

This assessment is subject to the University Assessment Regulations for Candidates

CS$2$IDS

b$.$ Using the given Vector clock diagram, determine the Vector clock value $($Counter$/$TS$)$ of each event on the process $P,Q$ and $R,$ when:

Counter$/$TS for each internal$/$local event on the $P,Q$ and $R$ is incremented by $1,$ and other counters are unaffected in the vector.

Counter$/$TS for each external$/$received message event is incremented by $1$ on the process where the message is received. All other counters will be updated on that process based on the max value $=$ max$($local$\_$counter, received$\_$counter$)$ in the vector. $(12$ marks$)$

Figure: Vector clock diagram

c$.$ Draw and explain ordering of events with a suitable example with minimum five events using both physical clock and logical clock.

$(5$ marks$)$

Note: All the calculated values should be written using the same diagram.