Voice over IP Book

Contents.

Preface.

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.

Acronyms.

References.

Index.