Failure Models

List of failure models in order of increasing difficulty to deal with it.

• Fail-stop

• Crash

• Omission

• Temporal

• Byzantine

Fail-stop

A node in the distributed systems halts permanently. However, the other nodes can still detect that node by communicating with it.

Crash

In this type of failure, a node in the distributed system halts silently, and the other nodes can't detect that the node has stopped working.

Omission Failures

In omission failures, the node fails to send or receive messages.

• Send Omission Failures: The node fails to respond to the incoming request.

• Receive Omission Failure: The nod fails to receive the request and thus can't acknowledge it.

Temporal Failures

The node generates correct results, but is too late to be useful. The failure could be due to bad algorithms, a bad design strategy or a loss of synchronization between the processor clocks.

Byzantine Failures

The node exhibits random behaviour like transmitting arbitrary messages at arbitrary times, producing wrong results, or stopping midway. This mostly happens due to an attack by a malicious entity or a software bug.