Fault Tolerant Computing: A Network Reliability Approach

The provision of fault tolerance to network systems is one which primarily explores the problems of hardware failures and also crashes system. Network reliability refers to the reliability of overall network to provide communication in the event of failure of a component or components in a network. The term fault tolerant is usually used to refer to how reliable a particular component of a network is (e.g. switch or a router). Several software errors that have occurred on various data networks such as the ARPANET, Internet, and SS7 network (the data network that carries the signaling information for the public telephone network) have caused such severe congestion in the network that it cannot be adequately addressed by normal congestions control schemes.Most reliable network designs address the failure of any single component, and some designs tolerate multiple failures. The temporal characteristics of faults vary widely, but can be roughly categorized as permanent, intermittent, or transient. Failures that prevent a component from functioning until repaired or replaced are considered permanent. Failures that allow a component to function properly some of the time are called intermittent. Damaged connectors and electrical components sometimes produce intermittent faults, operating correctly until mechanical vibrations or thermal variations cause a failure, and recovering when conditions change again. The last category, transient faults, is usually the easiest to handle. Transient faults range from changes in the contents of computer memory due to cosmic rays, to bit errors due to thermal noise in a demodulator, and are typically infrequent and unpredictable In this paper we will discuss network faults, software fault tolerance, network Fault detection mechanisms, fault detection and network surveillance, techniques for improving reliability of networks, fault recovery schemes, approaches to fault tolerance in high-speed backbone networks, fault tolerance for packet-switched networks, future challenges.