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Fax, Modem, and Text for IP Telephony
- By David Hanes, Gonzalo Salgueiro
- Published Jun 6, 2008 by Cisco Press.
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Description
- Copyright 2008
- Edition: 1st
- eBook
- ISBN-10: 1-58705-758-1
- ISBN-13: 978-1-58705-758-8
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
Sample Content
Table 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