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Voice Over IP, 2nd Edition

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Voice Over IP, 2nd Edition


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  • Copyright 2002
  • Dimensions: K
  • Pages: 352
  • Edition: 2nd
  • Book
  • ISBN-10: 0-13-065204-0
  • ISBN-13: 978-0-13-065204-1

  • The #1 VoIP bestseller for technical professionals (now completely updated!
  • All-new chapters on gateways, call processing, and traffic engineering
  • IP and the PSTN: advanced interoperability solutions
  • TRIP: the breakthrough protocol for voice message delivery
  • Cisco Voice QoS: traffic prioritization, congestion control, signaling, policies, and more

The authoritative guide to Internet voice communications (now completely updated!

Voice Over IP, Second Edition is the essential guide for telecommunications professionals who must understand or deploy VoIP. Leading network consultant Uyless Black carefully evaluates VoIP's challenges and compelling advantages, and then reviews every technical standard and platform. This thoroughly updated Second Edition reflects dramatic improvements in VoIP standards and practice, adding completely new chapters on gateways, RSVP and DiffServ call processing, and traffic engineering.

  • Reviews key technical obstacles to successful VoIP deployment, including packet loss and variable delay
  • Covers emerging approaches to interoperability between IP networks and the public switched telephone network
  • Introduces Telephony Routing Over IP (TRIP), the breakthrough protocol for voice message delivery
  • Covers Cisco Voice QoS network optimization in detail: traffic prioritization, congestion control, signaling, QoS management, and policy control
  • Shows how to establish paths to service providers through the local loop via ISDN, xDSL, and HFC
  • Contains concise, to-the-point introductions to H.322, Megaco, MGCP, and SIP

Voice Over IP, Second Edition is everything you need to know about running voice over IP networks today(from technical fundamentals to next-generation protocols and beyond.

Sample Content

Table of Contents



1. Introduction.

Internet Telephony and Packetized Voice. Why Internet Telephony? The Business Case. Universal Presence of IP. Maturation of Technologies. The Shift to Data Networks. Why Use IP for Telephony Traffic? Barriers to Successful Deployment of IP Telephony. Reliability of the Telephone Network. VoIP in the Internet and in Private Internets. The Question: Not If, But How? Configuration Options. Problems with the Configurations. Using a LAN Connection into the Telephone Network. Private VoIP Networks: The VPN. Private Internet and Public Internet Configurations. The Next Step. E-com and IP-Based Call Centers. Configuration and Topology Choices. Basic Terms and Concepts. Attributes of the Internet. Internet Attributes with Respect to Voice Traffic. The Internet Layered Architecture. Evaluating the Factors in Packetized Voice. Accommodating the Voice and Data Requirements in a Network. Tolerance for Errors. Tolerance for Delay. Tolerance for Variable Bit Rates and Constant Bit Rates. Examples of Voice, Video, and Data Applications Requirements. Making the Internet Look Like the Telephone Network. Summary.

2. Characteristics of the Internet and IP.

Architecture of the Internet. ISPs and the Telephone Network. Attributes of the Internet. Round-Trip Time (RTT). Packet Lossææ38 Order of Arrival of Packets. Hop Distance. Need for Fixed Routing? Size of Packets and Kinds of Traffic IP Supports. Overview of IP. The IP Datagram. Transmission Control Protocol and User Datagram Protocol. The Port Conceptææ51 TCP Traffic Management Operations. UDP. Summary.

3. The VoIP Model.

The VoIP Protocol Suite. Voice Over IP, Voice Over UDP, or Voice Over RTP? Voice Directly Over IP. Voice Directly Over UDP. Voice Directly Over RTP. Not Voice Over TCP. The Call Processing (Signaling) Protocols. Other Support for VoIP. Data in a VoIP Session. How the Web Fits In. Grouping the VoIP Protocols into Planes. Summary.

4. Digital Signal Processors (DSPs).

Role of DSPs in Packet-Voice Operations. DSP Voice Packet Moduleææ63 DSP Cores. DSP vs. Customized Hardware. Fixed- and Floating-Point Processorsææ65 Memory Architectures. Software Differences. Fast Fourier Transform Operations. Signal Filters and the Finite Impulse Response (FIR) Filter. Predictability of Performance. Another Example of DSP Code. Summary.

5. Voice Coders.

Functions of the Voice Coder. Classification of Speech Coders. Vector Quantization and Code-Excited Linear Prediction. Linear Prediction Analysis-by-Synthesis Coders. Forward-Adaptive LPAS Coders. Backward-Adaptive LPAS Coding [16-kbit/s G.728 Low-Delay Code Book Excitation Linear Prediction (LD-CELP)]. Parameter Speech Coders: 2.4-kbit/s Mixed-Excitation LPC (MELP). G.723.1 Scalable Coding for Wireless Applications. Evaluating Coders. Comparison of Speech Coders. Conservation of Bandwidth with Voice Activity Detectionææ83 Bandwidth Consumption of the Codec and Supporting Protocols. Summary.

6. Modems, LAPM, PPP, and the V.100 Series.

Another Look at the Layered Architecture for VoIP. Prevalent Modems. Role of DSPs in Modem Operations. Typical Link Layout. The V.24 Interfac Standard. The EIA-232 Interface. Typical Modem Layout. Role of the Point-to-Point Protocol. The Protocol Data Unit on the Link Between the User and the ISP. V Series Modems. The V.34 Operations. The 56-kbit/s V.90 Modem. V.100, V.110, and V.120 Recommendations for ISDN Interfaces, The V.100 Recommendationææ103 The V.110 Recommendation. RA Frame. V.110 Handshaking. The V.120 Recommendation. Summary.

7. Connecting to Service Providers Through the Local Loop.

Path Between an Internet User and the Internet. The Bandwidth Problem at the Local Loop. Termination of the Modem Analog Signal. Alternatives to the Modem-based Local Loop Access. The Integrated Services Digital Network (ISDN). ISDN Bearer Services. Role of Digital Subscriber Line (DSL) Technologies. The Evolving ADSL Technology. The Hybrid Fiber Coax (HFC) Approach. A High-Speed Proprietary Solution. Bypassing the Circuit-Switched Technology to Reach the Internet. Summary.

8. Performance Considerations and Traffic Engineering.

Traffic Engineering Defined. Packet Size, Queue Size, Loss, and Latency. Interarrival Jitter. Goals of Traffic Engineering. The Committed Access Rate. CAR Data Rates. Setting Up CAR Subrate Services. Access Lists. Supporting Traffic Engineering with Queuing. Examples of Queuing Methods. Weighted Fair Queuing. Comparison of Use and Nonuse of WFQ. Custom Queuing. Priority Queuing. Congestion-Avoidance Procedures. Tail Drop, RED, and WRED. Policy-Based Routing. Constrained Routing with MPLS and OSPF. Explicit Routing. LDP and Constraint-Based Routing. Preemption. Example of Constrained Routing to Support VoIP. A Guaranteed Rate for Voice Traffic. Performance of VoIP in the Internet. Summary.

9. RSVP, DiffServ, and Other Supporting Procedures in VoIP Networks.

Reserving Resources for Voice Traffic. QOS Models: IntServ and DiffServ. RSVP. RSVP Operation Entities. Sessions. The Key RSVP Messages. Admission Control and Policy Control. The Flow Descriptor. The Reservation Style. RSVP Set Up in the Router. RSVP Scaling. IP RTP Reserve. DiffServ. The Codepoint and Per-Hop Behavior. The DS Domain. Metering, Marking, Shaping, and Policing Operations. Traffic Classification and Conditioning. Relationships of the DS Functions. DiffServ in the Router. The Real-Time Protocol (RTP). Clocking Protocols with Network Time Protocol (NTP). Role of Multicasting. Basic Concepts. Multicast Trees. Key Protocols. The Session Description Protocol (SDP).Summary.

10. VoIP Gateways and IP Call Processing Protocols.

Tasks of the VoIP Gateway. The Gateway/Gatekeeper Model. IP Call Processing Protocols. H.323 General Description. Architecture of H.323. Major Operations of H.323. Megaco General Description. Architecture of Megaco. Major Operations. MGCP General Description. Architecture of MGCP. Major Operations. SIP General Description. Architecture of SIP. Major Operations. Summary.

11. Internetworking SS7 and Internet Call Processing Reasons to Combine IP and SS7.

Possible Configurations. Vital Telephony Databases at the Service Control Point. The SS7-IP Architectural Framework. The IP/SS7 Internetworking Model (RFC 2719). Implementations of the IP/SS7 Functions. Interworking H.323 and SS7. SIP Internetworking Specifications. SIP QOS Model. SIP QOS Elements. SIP Extensions for SS7 Internetworking. SIP Codes. Typical Call Setupææ233 Call Failure and Playing an Error Tone/Announcement. Termination at the Other End. SIP Redirection. Caller or Callee Hangs Up. Into the Future with TRIP. The Problem. The Proposed Solution. Future of TRIP. Summary.

12. Other Packet Voice Alternatives.

Use of Other Alternatives.Functions of Voice over Frame Relay. PVC Fragmentation. Fragmentation Operations. Service Multiplexing. Component of the VoFR Specification. Subchannels and the DLCIs. Operations of Voice over Frame Relay. Servicing the Dialed Digits. Fax Transmission. VoFR Encapsulation. Voice over ATM with AAL 1. Voice over ATM with AAL 2. VoFR and VoATM: Partners with or Competitors to VoIP? What Resides in the User Workstation? Here Comes MPLS. For the Future?

Appendix A. Telephony Signaling.

Appendix B. ISDN and SS7.

Appendix C. Tutorial on the V.34 and V.90 Modems.






This book is one in a series of books called "Advanced Communications Technologies." As the name of the book implies, the focus is on the Internet and the Internet Protocol (IP) in relation to the support of voice traffic.

The subject matter of this book is vast and my approach is to provide an introduction to the topic. In consonance with the intent of this series, this survey also has considerable detail but not to the level needed to design a system. For that, I leave you to your project team and the various specifications that establish the standards for Internet telephony.

This book is considered to be at an intermediate to advanced level. As such, it assumes the reader has a background in voice and data communications and the IP suite. Notwithstanding, for the new reader, I have provided several tutorials and guide you to them in the appropriate parts of the book. I also guide the more experienced reader away from them.

I hope you find this book a valuable addition to your library.


In writing multiple books about data and voice communications systems, the author is faced with a question: How much overlap (redundancy of material) should there be among the books in the series? If the overlap is too little, the reader must buy other books in the series to fill the gaps. If the overlap is too great, the reader who has purchased other books in the series may feel cheated by spending additional money to obtain the same information.

My approach is to try to strike a compromise between the two extremes. If another book in the series contains information on a topic that is relevant to the topic of the current book, yet is not a required subject in order to read the current book, I make reference to the book. However, that is not always possible. In a few cases, it is necessary to include material from other books in the series. Otherwise, the book in question becomes a fragmented reference to other books. I have taken this approach with this book. I trust you find this an efficient and useful way to deal with this matter.

To help strike this compromise, I have included appendices that are extracted from some of my other books. A basic knowledge of telephony signaling, the V.34 modem, ISDN, and SS7 will be very helpful as you read some of these chapters about VoIP, and I have included tutorials on these subjects in the appendices at the back of this book.


This book is a survey (albeit a detailed one) of the VoIP technology. A wide variety of VoIP control messages and protocols are used to support VoIP, and the standards bodies and the Internet task forces are defining hundreds of messages and scores of protocol flows between VoIP gateways, call agents, and user machines. It is not the intent of this book to explain the contents of each message and each protocol flow, which would simply duplicate the VoIP specifications. Instead, I provide tutorial explanations of these messages and flows, as well as selected examples of each. In each case, I provide you with references to the original specifications. In this manner, the book should provide you with a handy reference tool and act as a pointer toward more information if you so desire.


A considerable portion this book is devoted to explaining many Internet-based specifications pertaining to packet telephony.

Keep in mind that the Internet drafts are works in progress, and should be viewed as such. You should not use the drafts with the expectation that they will not change. Notwithstanding, if used as general tutorials, the drafts discussed in this book are "final enough" to warrant their explanations. Indeed, many of my clients use these drafts in their product planning and design.

For all the Internet standards and drafts the following applies:

Copyright (c) The Internet Society (1998). All Rights Reserved.

This document and translations of it may be copied and furnished to others, and derivative works that comment on or otherwise explain it or assist in its implementation may be prepared, copied, published and distributed, in whole or in part, without restriction of any kind, provided that the above copyright notice and this paragraph are included on all such copies and derivative works. However, this document itself may not be modified in any way, such as by removing the copyright notice or references to the Internet Society or other Internet organizations, except as needed for the purpose of developing Internet standards in which case the procedures for copyrights defined in the Internet Standards process must be followed, or as required to translate it into languages other than English.

The limited permissions granted above are perpetual and will not be revoked by the Internet Society or its successors or assigns.


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