Communication methods are essential to enable the continual expansion of the technological society in which we live. They enable people to exchange ideas, opinions and synchronise all interactions between themselves and others. Telephony is still the predominant method of communication although new techniques, such as electronic mail and mobile communications are becoming more and more popular. Network users are requesting increasingly complex services which cannot be effectively supported by existing network architectures. Also, there is a desire to share data, distribute application processing among network elements and an increasing demand for more sophisticated telecommunications services. All of these factors have led to the evolution of new networking architectures.