Failure semantics

Types of errors

• An omission error is when one or more responses fails.
• A crash error is when nothing happens. A crash is a special case of omission when all responses fail.
• A Timing error is when one or more responses arrive outside the time interval specified. Timing errors can be early or late. An omission error is a timing error when a response has infinite timing error.
• An arbitrary error is any error,.
• When a client uses a server it can cope with different type errors from the server.
• * If it can manage a crash at the server it is said to assume the server to have crash failure semantics.
• * If it can manage a service omission it is said to assume the server to have omission failure semantics.
• ** Failure semantics are the type of errors that are expected to appear.
• Should another type of error appear it will lead to a service failure because it cannot be managed.