By Michael Adams, Time Warner Cable Advanced Engineering
This paper discusses the notion of fault tolerance in an interactive multi-media delivery system. The various components are reviewed together with strategies for hardware redundancy and the software mechanisms necessary to support the use of hardware redundancy. Traditional telecommunications approaches to fault tolerance are referenced and the cost and complexity of these schemes is shown to be unrealistic for the kinds of full service networks envisioned. The Orlando Full Service Network is described and its expected and actual failure modes are discussed. Fault tolerance mechanisms that are designed to use spare capacity in the delivery system are described and the effectiveness and simplicity of alternative schemes are discussed. The paper proposes a set of network design rules that can be used to build fault-tolerant entertainment-delivery networks without increasing cost dramatically.