What is Logical clock in distributed system?

How clock synchronization occurs in a distributed system?

Clock synchronization in a distributed system is achieved by using algorithms like NTP (Network Time Protocol) or PTP (Precision Time Protocol) to ensure that all clocks in the system are adjusted to a common time reference. This helps in maintaining consistency and coordination among different nodes in the distributed system. By periodically updating and correcting the local clocks based on a reliable time source, synchronization is maintained across the system.

How does the vector clock mechanism in a distributed system ensure accurate ordering of events across multiple nodes?

The vector clock mechanism in a distributed system assigns a unique timestamp to each event based on the state of all nodes. By comparing these timestamps, the system can accurately order events across multiple nodes, ensuring that events are processed in the correct sequence.

Why round robin algorithm not applicable for distributed environment?

distributed system doesn't have any global clock time. It uses some special schedule technique such as lampart's cycle and other algorithm.

What logical topology uses distributed authentication?

Peer-to-Peer

Difference between Bus Clock and System Clock in Microcontrollers?

Bus Clock is based on the System Clock. In other terms Bus Clock is derived from system Clock. Bus Clock is usually half System Clock. (Busy Clock = System Clock / 2)

Drawbacks of Lamport logical clock?

Lamport's clock does'nt ensure that if L(e1)<L(e2) e1->e2

What is meant by distributed cache?

A distributed cache is when a cache is distributed across an array of ISA server computers. It is set up as a single logical entity which prevents duplication and also increases efficiency.

Difference between distributed system and multiprocessor system?

The difference between distributed system and multiprocessor system is whether the processing units in the system share the main memory. If yes, then the system is multiprocessor system; otherwise, it's a distributed system.

What is the difference between physical and logical clock in synchronisation?

For many appls:  it is sufficient that all machines agree on the same time.  it is not essential that this time also agree with the real time E.g. make example - it is adequate that all machines agree that it is 10:00 even if it is really 10:02. Meaning: it is the internal consistency of the clocks that matters, not whether they are particularly close to the real time. For these algorithms it is conventional to speak of the clocks as logical clocks.  Counter-ex: when the additional constraint is present that the clocks  must not only be the same,  but also must not deviate from the real time by more than a certain amount, the clocks are called physical clocks.

Is computer network and distributed system is similar?

distributed system is a special case of computer network.ofcourse distributed system is a network but a network may or may not be distributed.In general,a computer network is a very general term but distributed system is more specific..

When was Distributed Concurrent Versions System created?

Distributed Concurrent Versions System was created in 2002.

Lamport's logical clock?

Leslie Lamport proposed this scheme to provide ordering of events in a distributed environment using logical clocks. Because it is impossible to have perfectly synchronized clocks and global time in a distributed system, it is often necessary to use logical clocks instead. Definitions:Happened Before Relation (->). This relation captures causal dependencies between events, that is, whether or not events have a cause and effect relation. This relation (->) is defined as follows: * a -> b, if a and b are in the same process and a occurred before b. * a -> b, if a is the event of sending a message and b is the receipt of that message by another process. * If a -> b and b -> c, then a -> c - that is, the relation has the property of transitivity. Causally Related Events: If event a -> event b, then a causally affects b. Concurrent Events: Two distinct events a and b are concurrent (a b) if (not) a -> b and (not) b -> a. That is, the events have no causal relationship. This is equivalent to b a. For any two events a and b in a system, only one of the following is true: a -> b, b -> a, or a b. Lamport introduced a system of logical clocks in order to make the -> relation possible. It works like this: Each process Pi in the system has its own clock Ci. Ci can be looked at as a function that assigns a number, Ci(a) to an event a. This is the timestamp of the event a in process Pi. These numbers are not in any way related to physical time -- that is why they are called logical clocks. These are generally implemented using counters, which increase each time an event occurs. Generally, an event's timestamp is the value of the clock at that time it occurs. Conditions Satisfied by the Logical Clock system:For any events a and b, if a -> b, then C(a) < C(b). This is true if two conditions are met: * If a occurs before b, then Ci(a) < Ci(b). * If a is a message sent from Pi and b is the recept of that same message in Pj, then Ci(a) < Cj(b). Implementation Rules Required* Clock Ci is incremented for each event: Ci := Ci + d (d > 0) * if a is the event of sending a message from one process to another, then the receiver sets its clock to the max of its current clock and the sender's clock - that is, Cj := max(Cj, tm + d) (d > 0) .