), Frame Relay, from Internet Protocol (IP) to competition, which in turn drives innovation, SO visionary Multiservice Network Architectures. network equipment makers are looking to feature and Converged network supports all of the user's traffic function development partners who adhere to open types with packet-based protocols such as ATM, Frame standards for leading-edge technology development. Relay, or IP. Of these, the dominant protocol in the Before discussing TDM, ATM, Frame Relay, IP and access, edge, and core of the network is the IP. The how a company can migrate voice over IP (VoIP), we concept of a managed IP infrastructure for voice, video, need to understand the basic rules of traditional voice and data transmission has begun to revolutionize the in- communications. dustry. It leverages the Internet SO that enhanced services can be offered at lower costs and it is motivating the development of a family of dynamic, next-generation, Voice networking real-time applications. For traditional carriers, the im- portance of the co-existence of existing and newer Basic voice technology has been available for more than technologies and equipment is an important reality. 100 years. During that time, the technology has matured Next-generation multiservice networks, based on to the point at which it has become ubiquitous and packetized technologies, will not entirely push out largely invisible to most users. This legacy of slow Communications Engineering Desk Reference; ISBN: 9780123746481 Copyright © 2003 Elsevier Inc. All rights reserved CHAPTER 3.2 Network infrastructure evolution continues to affect today's advanced voice sensing current flow, then knows that the receiver is networks in many ways, SO it is important to understand off-hook and applies a dial tone. The switch also checks the fundamentals of traditional voice technology before to be sure that the receiver is on-hook before sending emulating it on data networks. a ringing signal. This system works well for simple tele- Traditional analog telepho