Fixed/Mobile Convergence and Beyond

Chapter 7. VoIP - Layers 3 and 4, the IP Infrastructure

7.1. VoIP: An Introduction

From the time Alexander Graham Bell patented the telephone through the latter part of the 20^th century, all telephony products were built around a circuit-switched design. Whether analog or digital, this meant that to set up a call between two points, a physical metallic circuit had to be established and was dedicated for the length of the call. Because such technology has matured over the past 100 years, we have become accustomed to the reliability of this infrastructure; we know that when we pick up a receiver (going off hook), we'll get a dial tone.

Inherent in such an architecture was an upper capacity limit of the number of simultaneous circuits that could ...