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Full Description
IP Telephony has revolutionized many aspects of telecommunications and it continues to be deployed at a rapid pace. The benefits of transporting voice over an IP infrastructure include increased flexibility, better scalability, and a significant cost savings over traditional telephony networks. However, during the deployment of these VoIP solutions, other types of traditional telephony communications that can also realize these same benefits are often overlooked or ignored. Fax, Modem, and Text for IP Telephony is a comprehensive resource that confronts the need for information on transporting alternative, non-voice communications over the IP protocol. Beginning with the basic theory and operation of fax, modem, and text telephony, this book then educates you on all of the current transport options that are available. An extensive design guide then provides the pertinent advice and best practices for making the correct planning decisions and choosing the best transport option for your network.Fax, Modem, and Text for IP Telephony also includes meticulous configuration and troubleshooting guides. The configuration guides in this book include a number of sample configurations and tips to manage any fax, modem, or text deployment. The troubleshooting guides present the essential methodologies, debugs, and analysis tools for quickly resolving both the common and complex issues that may be encountered. This book is the perfect companion to other VoIP resources, and it is the only book that empowers you to successfully handle any fax, modem, or text implementation.David Hanes, CCIE (R) No. 3491, is currently a senior engineer specializing in training, network design assistance, and troubleshooting of fax technologies for the Customer Assurance Engineering (CAE) group at Cisco (R). Since joining Cisco in 1997, David has worked as a TAC engineer for the WAN, WAN Switching, and Multiservice Voice teams, a team lead for the Multiservice Voice team, and an escalation engineer covering a variety of voice and fax technologies. David has troubleshot escalated issues in Cisco customer networks worldwide and remains a technical resource for other Cisco employees and customers.Gonzalo Salgueiro CCIE No. 4541, is a senior escalation engineer supporting voice, fax, and modem technologies for the Cisco TAC. Gonzalo has spent more than 11 years troubleshooting complex issues in large-scale VoIP networks as well as providing technical leadership for some of the most critical worldwide voice and fax deployments. Prior to joining the Escalation Team in 1999 Gonzalo had roles as a TAC engineer for both the Access/Dial and Multiservice Voice teams as well as a team lead for the Access/Dial team. Learn basic and advanced operational theory and practical implementation of fax, modem, and text communications Understand how to implement fax, modem, and text communications using protocols such as H.323, SIP, MGCP, and SCCP. Explore the functionality and advantages of T.38 fax relay, passthrough, modem relay, T.37 Store-and-Forward Fax, and text relay for IP network deployments Employ expert-recommended best practices and design solutions for deploying fax, modem, and text in an IP telephony environment Optimize your network with comprehensive fax, modem, and text configuration and design tips for use with IOS and non-IOS gateways Master the latest fax, modem, and text troubleshooting tools and techniques employed by Cisco engineersCategory: Cisco Press-IP CommunicationCovers: Fax, Modem, and Text Telephony Technologies for Integrated IP Networks
Contents
Introduction xxiiiPart I Laying the Groundwork 3Chapter 1 How Modems Work 5A Brief History of Modems 5Modem Architecture 8Modem Types 10External Versus Internal Modems 10Hardware Versus Software Modems 10Fax Modems 12Terminal-to-Modem Communication 14DTE and DCE 15RS-232 Signaling 15Asynchronous Framing 19User Interface 20Modem-to-Modem Communication 26Modulation 26Frequency Shift Keying (FSK) 28Phase Shift Keying (PSK) 29Amplitude Modulation (AM) 30Quadrature Amplitude Modulation (QAM) 31Trellis Coded Modulation (TCM) 32Modulation Standards 33Modem Call Analysis 34Call Setup 35Phase I: Network Interaction 36Phase II: Probing/Ranging 38Phase III: Equalizer and Echo Canceller Training 40Phase IV: Final Training 41Data Mode 42Retrains and Speedshifts 42Error Control 45Data Compression 48Call Disconnect 49Summary 51Chapter 2 How Fax Works 53A Brief History of Fax 54Fax Components 56Group Classifications 57Specifications and Standards 58Fax Modulations 59Fax Messaging 61Phases of a Fax Call 62Message Format Overview 63Analyzing a Basic Fax Call 65CNG Tone 66CED Tone 67DIS, NSF, and CSI Messages 68DCS and TSI Messages 71TCF, CFR, and FTT Messages 73MPS, EOP, EOM, MCF, RTP, RTN, and DCN Messages 75Other T.30 Messages 77Understanding Error Correction Mode 81ECM Call Analysis 82PPS and PPR 84Important G3 Timers 86Super G3 Faxing 88Comparison of SG3 and G3 89Super G3 Call Analysis 89Page Encoding 91Modified Huffman 92Modified READ 97Modified Modified READ 103Summary 105Chapter 3 How Text Telephony Works 107A Brief History of Text Telephony 107Text Telephone Terminology 110Standards and Specifications 110Carrier Based Versus Carrierless Protocols 111ITU-T Recommendation V.18 112Text Telephone Operation 112Acoustic Coupling Versus Direct Connections 113Originating and Receiving Text Telephone Calls 114Conversation Conventions 116Text Telephone Relay Services 118HCO (Hearing Carry Over) 119VCO (Voice Carry Over) 120Baudot Protocol 121Baudot Character Set 121Baudot Modulation Details 123Summary 124Part II IP Solutions and Design 127Chapter 4 Passthrough 129Passthrough Fundamentals 130NSE-Based Passthrough 137Fax Passthrough with NSE 139Modem Passthrough with NSE 141Protocol-Based Pass-Through for Fax 143Fax Pass-Through with H.323 Signaling 144Fax Pass-Through with SIP Signaling 145Text over G.711 146A Future Look at ITU-T V.152 147Summary 148Chapter 5 Relay 151Relay Fundamentals 151Fax Relay 154T.38 Fax Relay 155NSE-Based Switchover for T.38 167Protocol-Based Switchover for T.38 169Cisco Fax Relay 173Modem Relay 175Cisco Text Relay 181A Future Look at ITU-T T.38, V.150.1, and V.151 185Summary 185Chapter 6 T.37 Store-and-Forward Fax 189Overview of T.37 Store-and-Forward Fax 189SMTP Overview 191SMTP Commands and Sample Sessions 192DSN and MDN 195T.37 Onramp 201T.37 Offramp 203Summary 204Chapter 7 Design Guide for Fax, Modem, and Text 207General Passthrough and Relay Design Considerations 208Bandwidth 209Call Control Protocol 214QoS 215Redundancy 221Resource Utilization 224Secure RTP 227Timing and Synchronization 229Fax Design Considerations 231Gateway Interoperability Considerations 231Error Correction Mode 233Super G3 235Hairpin Calls 237Fallback 239T.37 Store-and-Forward Fax 241Fax Detect Script 243Unified CM Integration 245Comparing Fax Passthrough and Fax Relay 249Modem Design Considerations 251Comparing Modem Passthrough and Cisco Modem Relay 252Secure Modem Relay 254Text Design Considerations 256Summary and Best Practices 258Chapter 8 Fax Servers 263Fax Server Basics 264Fax Server Integration Solutions 269Fax Server TDM Integration with a Cisco Voice Gateway 269Fax Server T.38 Integration with a Cisco Voice Gateway 272Fax Server T.38 Integration with Unified CM 276Fax Server Redundancy and Failover 281Summary 283Part III Configuration 285Chapter 9 Configuring Passthrough 287IOS Gateway Passthrough Configuration 288IOS Gateway NSE-Based Passthrough Configuration 289IOS Gateway NSE-Based Passthrough Configuration for H.323, SIP, and SCCP 289IOS Gateway NSE-Based Passthrough Configuration for MGCP 292IOS Gateway Protocol-Based Pass-Through Configuration 293IOS Gateway Text over G.711 Configuration 2956608 Catalyst Blade Passthrough Configuration 295VG248 Passthrough Configuration 298ATA Passthrough Configuration 303Summary 308Chapter 10 Configuring Relay 311IOS Gateway Relay Configuration 311Fax Relay 312IOS Gateway Fax Relay Configuration for H.323, SIP, and SCCP 313IOS Gateway Fax Relay Configuration for MGCP 320Modem Relay 325IOS Gateway Cisco Modem Relay Configuration for H.323, SIP, and SCCP 326IOS Gateway Cisco Modem Relay Configuration for MGCP 329Cisco Text Relay 332IOS Example Configurations for Relay 334Default Fax Relay Configuration for H.323 and SIP 334Cisco Fax Relay and Modem Passthrough Configuration for H.323 and SIP 336T.38 Fax Relay, Cisco Modem Relay, and Cisco Text Relay Configuration for H.323andSIP 337T.38 Fax Relay and Cisco Text Relay Configuration for SCCP 339T.38 Fax Relay and Modem Passthrough Configuration for MGCP 3406608 Catalyst Blade Fax Relay Configuration 342VG248 Fax Relay Configuration 344Summary 347Chapter 11 Configuring T.37 StoreandForward Fax 351Enabling T.37 Store-and-Forward Fax 351Loading the TCL Scripts 352Configuring T.37 Onramp Fax 354Dial-Peer Configuration for Onramp Fax 355Fax Receive Configuration Command for Onramp Fax 360MTA Configuration Commands for Onramp Fax 361Sample Onramp Configuration 365Configuring T.37 Offramp Fax 367Dial-Peer Configuration for Offramp Fax 367Fax Send Configuration Commands for Offramp Fax 369MTA Configuration Commands for Offramp Fax 372Sample Offramp Configuration 373Summary 375Part IV Troubleshooting 377Chapter 12 Troubleshooting Passthrough and Relay 379Attacking the Problem 380Fundamental Troubleshooting 382Checking the Condition of Originating and Terminating Devices 383Testing with Voice Calls 384Testing with PSTN Calls 385Confirming the Configuration 386Debugging Best Practices 387Telephony and IP Troubleshooting 391Call Legs in IOS Gateways 392Viewing Call Legs 394Modem Passthrough Call Legs 394Fax Pass-Through Call Legs 399Fax Relay Call Legs 400Cisco Modem Relay Call Legs 402Text Telephony Call Legs 404Call Leg Troubleshooting Techniques 405Telephony Troubleshooting 407IP Troubleshooting 414IP Troubleshooting for IOS Gateways 416IP Troubleshooting for Non-IOS Gateways 419IP Troubleshooting Using Packet Captures 424Troubleshooting the Switchover Signaling 428Troubleshooting NSE-Based Switchovers 430NSE-Based Switchover for Modem Passthrough 430NSE-Based Switchover for Cisco Modem Relay 434NSE-Based Switchover for T.38 Fax Relay 436Validating NSE Switchover Support 438Troubleshooting Protocol-Based Switchovers 445Protocol-Based Fax Pass-Through and T.38 Switchovers for H.323 446Protocol-Based Fax Pass-Through and T.38 Switchovers for SIP 451Protocol-Based T.38 Switchover for MGCP 455Protocol-Based Switchovers and Unified CM 459Troubleshooting the Cisco Fax Relay Switchover 461Passthrough and Relay Troubleshooting 464Troubleshooting DSP Functions 464DSP HPI Troubleshooting 465Loss Planning 478Advanced Troubleshooting for Passthrough 485Advanced Troubleshooting for Fax Relay 487Fax Relay Data Rate 487Dealing with Packet Loss 488SG3 490Debugging T.30 Fax Messaging 491Analyzing T.38 Fax Relay Packet Captures 497NSF/NSS 499Handling High Delay 500Advanced Troubleshooting for Modem Relay 503Checking the Modem Endpoints 503Debugging Modem Relay 505Advanced Troubleshooting for Cisco Text Relay 506PCM Traces for Fax and Modem 510Capturing PCM Traces 511Analyzing PCM Traces 515Summary 523Chapter 13 Troubleshooting T.37 StoreandForward Fax 525Checking the Basics 525T.37 Onramp Troubleshooting 527Troubleshooting the Onramp Telephony Interface 532Troubleshooting the TIFF Image Creation 537Troubleshooting the Onramp SMTP Connection 540T.37 Offramp Troubleshooting 545Troubleshooting the Offramp SMTP Connection 549Troubleshooting the Creation of the Fax Page Image 553Troubleshooting the Offramp Telephony Interface 556Summary 559TOC, 1587052695, 5/20/2008
