Voice over IP Fundamentals, Second Edition

Chapter 5. PSTN Services

Today’s Public Switched Telephone Network (PSTN) offers many different services, each with a desirable suite of features and functionality. Service providers (SPs) can offer competitive services, differentiate themselves, and generate revenue from these offerings. Many of these services are not currently available in packet voice networks. However, much work is being done to determine the best and most scalable way to add these and many new services and functions to packet voice networks.

From an external point of view—or in terms of what the end user can use—the current generation of digital switching systems offers similar, if not identical, functionality. This makes it difficult for SPs to differentiate among the offerings. ...