Fax, Modem, and Text for IP Telephony

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® 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®. 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 engineers

Category: Cisco Press

List of contents

    Introduction xxiii
Part I  Laying the Groundwork 3
Chapter 1  How Modems Work 5
    A Brief History of Modems 5
    Modem Architecture 8
    Modem Types 10
        External Versus Internal Modems 10
        Hardware Versus Software Modems 10
        Fax Modems 12
    Terminal-to-Modem Communication 14
        DTE and DCE 15
        RS-232 Signaling 15
        Asynchronous Framing 19
        User Interface 20
    Modem-to-Modem Communication 26
        Modulation 26
            Frequency Shift Keying (FSK) 28
            Phase Shift Keying (PSK) 29
            Amplitude Modulation (AM) 30
            Quadrature Amplitude Modulation (QAM) 31
            Trellis Coded Modulation (TCM) 32
        Modulation Standards 33
    Modem Call Analysis 34
        Call Setup 35
            Phase I: Network Interaction 36
            Phase II: Probing/Ranging 38
            Phase III: Equalizer and Echo Canceller Training 40
            Phase IV: Final Training 41
        Data Mode 42
            Retrains and Speedshifts 42
            Error Control 45
            Data Compression 48
        Call Disconnect 49
    Summary 51
Chapter 2  How Fax Works 53
    A Brief History of Fax 54
    Fax Components 56
    Group Classifications 57
    Specifications and Standards 58
    Fax Modulations 59
    Fax Messaging 61
        Phases of a Fax Call 62
        Message Format Overview 63
        Analyzing a Basic Fax Call 65
            CNG Tone 66
            CED Tone 67
            DIS, NSF, and CSI Messages 68
            DCS and TSI Messages 71
            TCF, CFR, and FTT Messages 73
            MPS, EOP, EOM, MCF, RTP, RTN, and DCN Messages 75
            Other T.30 Messages 77
        Understanding Error Correction Mode 81
            ECM Call Analysis 82
            PPS and PPR 84
        Important G3 Timers 86
        Super G3 Faxing 88
            Comparison of SG3 and G3 89
            Super G3 Call Analysis 89
        Page Encoding 91
            Modified Huffman 92
            Modified READ 97
            Modified Modified READ 103
    Summary 105
Chapter 3  How Text Telephony Works 107
    A Brief History of Text Telephony 107
    Text Telephone Terminology 110
    Standards and Specifications 110
        Carrier Based Versus Carrierless Protocols 111
        ITU-T Recommendation V.18 112
    Text Telephone Operation 112
        Acoustic Coupling Versus Direct Connections 113
        Originating and Receiving Text Telephone Calls 114
        Conversation Conventions 116
        Text Telephone Relay Services 118
        HCO (Hearing Carry Over) 119
        VCO (Voice Carry Over) 120
    Baudot Protocol 121
        Baudot Character Set 121
        Baudot Modulation Details 123
    Summary 124
Part II  IP Solutions and Design 127
Chapter 4  Passthrough 129
    Passthrough Fundamentals 130
    NSE-Based Passthrough 137
        Fax Passthrough with NSE 139
        Modem Passthrough with NSE 141
    Protocol-Based Pass-Through for Fax 143
        Fax Pass-Through with H.323 Signaling 144
        Fax Pass-Through with SIP Signaling 145
    Text over G.711 146
    A Future Look at ITU-T V.152 147
    Summary 148
Chapter 5  Relay 151
    Relay Fundamentals 151
    Fax Relay 154
        T.38 Fax Relay 155
            NSE-Based Switchover for T.38 167
            Protocol-Based Switchover for T.38 169
        Cisco Fax Relay 173
    Modem Relay 175
    Cisco Text Relay 181
    A Future Look at ITU-T T.38, V.150.1, and V.151 185
    Summary 185
Chapter 6  T.37 Store-and-Forward Fax 189
    Overview of T.37 Store-and-Forward Fax 189
    SMTP Overview 191
        SMTP Commands and Sample Sessions 192
        DSN and MDN 195
    T.37 Onramp 201
    T.37 Offramp 203
    Summary 204
Chapter 7  Design Guide for Fax, Modem, and Text 207
    General Passthrough and Relay Design Considerations 208
        Bandwidth 209
        Call Control Protocol 214
        QoS 215
        Redundancy 221
        Resource Utilization 224
        Secure RTP 227
        Timing and Synchronization 229
    Fax Design Considerations 231
        Gateway Interoperability Considerations 231
        Error Correction Mode 233
        Super G3 235
        Hairpin Calls 237
        Fallback 239
        T.37 Store-and-Forward Fax 241
        Fax Detect Script 243
        Unified CM Integration 245
        Comparing Fax Passthrough and Fax Relay 249
    Modem Design Considerations 251
        Comparing Modem Passthrough and Cisco Modem Relay 252
        Secure Modem Relay 254
    Text Design Considerations 256
    Summary and Best Practices 258
Chapter 8  Fax Servers 263
    Fax Server Basics 264
    Fax Server Integration Solutions 269
        Fax Server TDM Integration with a Cisco Voice Gateway 269
        Fax Server T.38 Integration with a Cisco Voice Gateway 272
        Fax Server T.38 Integration with Unified CM 276
    Fax Server Redundancy and Failover 281
    Summary 283
Part III  Configuration 285
Chapter 9  Configuring Passthrough 287
    IOS Gateway Passthrough Configuration 288
        IOS Gateway NSE-Based Passthrough Configuration 289
        IOS Gateway NSE-Based Passthrough Configuration for H.323, SIP, and SCCP 289
            IOS Gateway NSE-Based Passthrough Configuration for MGCP 292
        IOS Gateway Protocol-Based Pass-Through Configuration 293
        IOS Gateway Text over G.711 Configuration 295
    6608 Catalyst Blade Passthrough Configuration 295
    VG248 Passthrough Configuration 298
    ATA Passthrough Configuration 303
    Summary 308
Chapter 10  Configuring Relay 311
    IOS Gateway Relay Configuration 311
        Fax Relay 312
            IOS Gateway Fax Relay Configuration for H.323, SIP, and SCCP 313
            IOS Gateway Fax Relay Configuration for MGCP 320
        Modem Relay 325
            IOS Gateway Cisco Modem Relay Configuration for H.323, SIP, and SCCP 326
            IOS Gateway Cisco Modem Relay Configuration for MGCP 329
        Cisco Text Relay 332
        IOS Example Configurations for Relay 334
            Default Fax Relay Configuration for H.323 and SIP 334
            Cisco Fax Relay and Modem Passthrough Configuration for H.323 and SIP 336
            T.38 Fax Relay, Cisco Modem Relay, and Cisco Text Relay Configuration for H.323‡and‡SIP 337
            T.38 Fax Relay and Cisco Text Relay Configuration for SCCP 339
            T.38 Fax Relay and Modem Passthrough Configuration for MGCP 340
    6608 Catalyst Blade Fax Relay Configuration 342
    VG248 Fax Relay Configuration 344
    Summary 347
Chapter 11  Configuring T.37 StoreandForward Fax 351
    Enabling T.37 Store-and-Forward Fax 351
    Loading the TCL Scripts 352
    Configuring T.37 Onramp Fax 354
        Dial-Peer Configuration for Onramp Fax 355
        Fax Receive Configuration Command for Onramp Fax 360
        MTA Configuration Commands for Onramp Fax 361
        Sample Onramp Configuration 365
    Configuring T.37 Offramp Fax 367
        Dial-Peer Configuration for Offramp Fax 367
        Fax Send Configuration Commands for Offramp Fax 369
        MTA Configuration Commands for Offramp Fax 372
        Sample Offramp Configuration 373
    Summary 375
Part IV  Troubleshooting 377
Chapter 12  Troubleshooting Passthrough and Relay 379
    Attacking the Problem 380
    Fundamental Troubleshooting 382
        Checking the Condition of Originating and Terminating Devices 383
        Testing with Voice Calls 384
        Testing with PSTN Calls 385
        Confirming the Configuration 386
        Debugging Best Practices 387
    Telephony and IP Troubleshooting 391
        Call Legs in IOS Gateways 392
        Viewing Call Legs 394
            Modem Passthrough Call Legs 394
            Fax Pass-Through Call Legs 399
            Fax Relay Call Legs 400
            Cisco Modem Relay Call Legs 402
            Text Telephony Call Legs 404
            Call Leg Troubleshooting Techniques 405
        Telephony Troubleshooting 407
        IP Troubleshooting 414
            IP Troubleshooting for IOS Gateways 416
            IP Troubleshooting for Non-IOS Gateways 419
            IP Troubleshooting Using Packet Captures 424
    Troubleshooting the Switchover Signaling 428
        Troubleshooting NSE-Based Switchovers 430
            NSE-Based Switchover for Modem Passthrough 430
            NSE-Based Switchover for Cisco Modem Relay 434
            NSE-Based Switchover for T.38 Fax Relay 436
            Validating NSE Switchover Support 438
        Troubleshooting Protocol-Based Switchovers 445
            Protocol-Based Fax Pass-Through and T.38 Switchovers for H.323 446
            Protocol-Based Fax Pass-Through and T.38 Switchovers for SIP 451
            Protocol-Based T.38 Switchover for MGCP 455
            Protocol-Based Switchovers and Unified CM 459
        Troubleshooting the Cisco Fax Relay Switchover 461
    Passthrough and Relay Troubleshooting 464
        Troubleshooting DSP Functions 464
            DSP HPI Troubleshooting 465
            Loss Planning 478
        Advanced Troubleshooting for Passthrough 485
        Advanced Troubleshooting for Fax Relay 487
            Fax Relay Data Rate 487
            Dealing with Packet Loss 488
            SG3 490
            Debugging T.30 Fax Messaging 491
            Analyzing T.38 Fax Relay Packet Captures 497
            NSF/NSS 499
            Handling High Delay 500
        Advanced Troubleshooting for Modem Relay 503
            Checking the Modem Endpoints 503
            Debugging Modem Relay 505
        Advanced Troubleshooting for Cisco Text Relay 506
        PCM Traces for Fax and Modem 510
            Capturing PCM Traces 511
            Analyzing PCM Traces 515
    Summary 523
Chapter 13  Troubleshooting T.37 StoreandForward Fax 525
    Checking the Basics 525
    T.37 Onramp Troubleshooting 527
        Troubleshooting the Onramp Telephony Interface 532
        Troubleshooting the TIFF Image Creation 537
        Troubleshooting the Onramp SMTP Connection 540
    T.37 Offramp Troubleshooting 545
        Troubleshooting the Offramp SMTP Connection 549
        Troubleshooting the Creation of the Fax Page Image 553
        Troubleshooting the Offramp Telephony Interface 556
    Summary 559
TOC, 1587052695, 5/20/2008
 

About the author

David Hanes, CCIE No. 3491, currently works as an engineer for the Cisco Customer Assurance Engineering (CAE) group based out of Research Triangle Park, North Carolina supporting various emerging technologies through product testing and field trials. In addition, David is a technical expert for Cisco in the area of fax over IP technologies and assists with network design and troubleshooting for critical fax over IP deployments. Since joining Cisco in 1997, he has worked as a Technical Assistance Center (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. Before working at Cisco, David was a Systems Engineer for Sprint, where he gained his first computer networking experience working on the Frame Relay and X.25 protocols. He holds a bachelor of science degree in electrical engineering from North Carolina State University.
 
Gonzalo Salgueiro, CCIE No. 4541, is a senior engineer for the Unified Communications Infrastructure Escalation team of the Technical Assistance Center (TAC) in Research Triangle Park, North Carolina. In his current role, he is a technical leader for fax and voice over IP technologies working directly with Cisco development engineering, TAC support teams, and product serviceability organization, providing support for various Unified Communications products and technologies. Over the past 12 years at Cisco, he has specialized in troubleshooting complex issues for some of the largest VoIP networks and has provided technical leadership for some of the most critical worldwide voice and fax deployments. Before joining the Escalation team in 1999, Gonzalo had roles as a TAC engineer for both the Access/Dial and Multiservice Voice teams and as a team lead for the Access/Dial team. Gonzalo has developed and delivered all levels of training and documentation on these technologies both internally to Cisco technical teams and externally to Cisco customers worldwide. He holds a bachelor of science degree in physics from Jacksonville University and a master of science degree in physics from the University of Miami.
 

Summary

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® 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®. 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 engineers

 
Category: Cisco Press-IP Communication
Covers: Fax, Modem, and Text Telephony Technologies for Integrated IP Networks
 

Product details

• Authors: David Hanes, Gonzalo Salgueiro
• Publisher: Macmillan Technical Publishing
• Languages: English
• Product format: Paperback / Softback
• Released: 25.06.2008
• EAN: 9781587052699
• ISBN: 978-1-58705-269-9
• No. of pages: 600
• Dimensions: 190 mm x 230 mm x 30 mm
• Weight: 960 g
• Series: Cisco Press; IP Communications (Paperback); Cisco Press
• Subject: Natural sciences, medicine, IT, technology > IT, data processing > Data communication, networks