# Frequent question: What is Lamport logical clock in distributed system?

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The Lamport timestamp algorithm is a simple logical clock algorithm used to determine the order of events in a distributed computer system. … Conceptually, this logical clock can be thought of as a clock that only has meaning in relation to messages moving between processes.

## What is logical clock in distributed system?

A logical clock is a mechanism for capturing chronological and causal relationships in a distributed system. … Moreover, in these applications, it suffices for the processes to agree on the event ordering (i.e., logical clock) rather than the wall-clock time.

## What is Lamport clock Why is it important in distributed systems?

Lamport Timestamps are used to (partially) order events in a distributed system. The algorithm is based on causal ordening of events and is the foundation of more advanced clocks such as Vector Clocks and Interval Tree Clocks (ITC).

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## What is Lamport algorithm in distributed system?

Lamport’s Distributed Mutual Exclusion Algorithm is a permission based algorithm proposed by Lamport as an illustration of his synchronization scheme for distributed systems. In permission based timestamp is used to order critical section requests and to resolve any conflict between requests.

## What is a Lamport clock and how are values assigned?

Lamport Clocks. Each process maintains a single Lamport timestamp counter. Each event in the process is tagged with a value from this counter. The counter is incremented before the event timestamp is assigned. … If an event is the sending of a message then the timestamp of that event is sent along with the message.

## What is difference between logical clock and vector clock?

Most of the physical clocks are based on cyclic processes such as a celestial rotation. … In such systems a logical clock allows global ordering on events from different processes. Vector clock. It is an algorithm for generating a partial ordering of events in a distributed system.

## What is a logic clock Why are logic clocks required in distributed systems?

Logical clock:

Is a mechanism for capturing chronological and causal relationships in a distributed system. Distributed systems may have no physically synchronous global clock, so a logical clock allows global ordering on events from different processes in such systems.

## What are the advantages of vector clock over Lamport clock?

Vector Clocks represent an extension of Lamport Timestamps in that they guarantee the strong clock consistency condition which (additionally to the clock consistency condition) dictates that if one event’s clock comes before another’s, then that event comes before the other, i.e., it is a two-way condition.

## What is the necessity of logical clock explain working principle of Lamport’s logical clock?

Lamport’s Logical Clock was created by Leslie Lamport. It is a procedure to determine the order of events occurring. It provides a basis for the more advanced Vector Clock Algorithm. Due to the absence of a Global Clock in a Distributed Operating System Lamport Logical Clock is needed.

## What are the limitations of Lampert’s logical clock?

Lamport’s clock has the advantage of requiring no changes in the behavior of the underlying protocol, but has the disadvantage that clocks are entirely under the control of the logical-clock protocol and may as a result make huge jumps when a message is received.

## What is the message complexity of Lamport algorithm?

This algorithm has several disadvantages. They are: It is very unreliable as failure of any one of the processes will halt progress. It has a high message complexity of 3(N − 1) messages per entry/exit into the critical section.

## What is the relation of the Lamport timestamps of the two events?

With Lamport timestamps, we are assured that two causally-related events will have timestamps that reflect the order of events. For example, event h happened before event m in the Lamport causal sense. The chain of causal events is h→c, c→d, and d→m.

## In which year Lamport showed that clock synchronization is possible and presented an algorithm for achieving it?

Lamport’s Logical Clocks

An important paper to read – “Time, clocks, and the ordering of events in a distributed system” by Lamport (1978). The important contribution of Lamport is that in a distributed system, clocks need not be synchronized absolutely.

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