Fault Tolerant Broadcast

Motivation

Goal of Distributed Agreement

Reliable Atomic Broadcast

Setting the stage

Process Failures

Communication Failures

The Problem

Reliable Broadcast

More formally

What if a process fails during its broadcast of m?

Realizing Reliable Broadcast

Efficiency Concerns

Ordering Issues

FIFO Broadcast

Realizing FIFO

Causal Broadcast

Event Ordering

Realizing Causal Broadcast

Atomic Broadcast

Total Ordering

The Bad News

What is Consensus?

Impossibility Result

Consensus and TORAB

It can’t REALLY be impossible?

Failure Detector

Distributed Failure Detection

Realizing Atomic Broadcast

Summary

Delivering one message everywhere

Delivering two messages in same order everywhere

Conclusions