8.1 Introduction

The patterns of telephony traffic in the networks run by public network operators (PNOs) have changed drastically over the last five years. Communications methods have changed and the demand for access to the Internet seemingly grows daily. Throughout the year 2000 many PNOs have reported that the Internet and related IP traffic has surpassed, in simple bandwidth, the demand for traditional telephony traffic.

It is easy to forget, however, that the volume of non-Internet telephony traffic also continues to grow. Better marketing information enabling personalised direct telesales, and the enormous growth in mobile telephone sales both contribute to the demand for telephony-type services. The telephony growth, however, is small (about 3 5% per annum, depending on statistics and network operator) compared to the phenomenal growth in Internet and IP-related traffic (anything from 100% to wildly imaginative figures exceeding the world's production capabilities).

Recently, PNOs have faced a choice in the development of networks to continue the development of existing, regulated switched-circuit networks (SCNs), also known as time-division multiplex (TDM) networks, or to leave the existing infrastructure frozen in its current state, and start to deploy a new network, better suited to IP-based terminals, outside the constraints of regulation and offering the potential of new services with faster deployment, and at lower costs. If the demand for telephony was not also growing, this strategy might be extremely attractive; however, many TDM networks are running out of switching...