This is an excerpt from the book "Voice-Enabling the Data Network" by James Durkin. The book provides a step-by-step
approach to designing a VoIP network and outlines each VoIP technology component with detailed descriptions of possible applications. This chapter focuses on how carriers are using VoIP to bundle voice and data services over a single access link to the customer. For example, traditional T1 circuits that are offered to customers to interconnect their private branch exchange PBX to interexchange carriers can now be used instead for integrated voice and data traffic, eliminating the need for multiple access links between the customer and the service provider.