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.
IntroductionIntroduction
The advent of VoIP has led to revolutionary changes in the world of telecommunications. Information that was transported on traditional telephony infrastructures such as voice, video, and modulated data is transitioning to IP backbones. However, in this transition process, modulated data such as fax, modem, and text is often overlooked. Fax, modem, and text are treated like regular voice communications in many cases when in fact they have different transport requirements and usually need unique transport protocols for communication to be reliable.
We, the authors of this book, have about 25 years of combined networking experience with the majority of it focusing on faxes, modems, and VoIP. We have seen and experienced firsthand as Cisco TAC engineers the problems that are encountered with fax and modem communications. While one of the most common problems we encounter is the failure to take into account the unique transport requirements of fax, modem, and text, we also have seen problems with the configuration of the multitude of fax-, modem-, and text-related commands in Cisco voice gateways. In addition, we have realized that many times there is just a lack in understanding of basic passthrough and relay fundamentals as they are implemented on Cisco voice products. Addressing these problems and how to troubleshoot them were our main focus while writing this book.
Therefore, you will notice that this book includes a comprehensive design guide for getting fax, modem, and text deployments working successfully from the start, a commonsense configuration section, and a thorough troubleshooting guide. Equally as important, we devoted a whole section to the fundamentals of passthrough and relay and how they are implemented on Cisco voice products. In this book, we address all the main difficulties that we have seen with the implementation of fax and modems in IP environments.
We have written this book to be the definitive resource for understanding, designing, configuring, and troubleshooting fax, modem, and text in today's IP networks. Whether you are a network designer, voice engineer, or simply someone who must support fax, modem, and text communications over IP networks, this book is practically a necessity. If you understand basic VoIP, this book will just build upon that core knowledge.
Many books and other resources are available that discuss VoIP, and some even have a casual mention of transporting fax or modem communications. However, this book is the only one that provides a comprehensive, one-stop reference for addressing all aspects of fax, modem, and text communication.
Target Release: Cisco IOS Software Version 12.4(9)T1
The examples and features explained throughout this book for Cisco IOS voice gateways target Cisco IOS Software Release 12.4(9)T1. However, other IOS versions should be applicable to the majority of this book, too. Be aware, however, that features and implementations might differ somewhat in other IOS versions. Other software versions for devices such as Cisco Unified Communications Manager, 6608, and the VG248 are noted in the text when applicable.
Goals and Methods
This book is designed to be the only resource you will ever need for handling fax, modem, and text communications in IP telephony environments. From basic theory to design solutions to configuration to troubleshooting, all aspects are covered in a clear, concise manner.
Who Should Read This Book?
Just about every IP telephony (IPT) installation has at least one fax machine, and larger installations often include modems and text telephony devices, too. If you work with IPT, your job has already required or more than likely will require in the future that you handle fax, modem, and text communications in your network. For this reason, this book is an indispensable resource that should reside beside your other books dealing with IPT.
In some areas, this book expects you to have basic IPT knowledge. You should be familiar with the Internet Protocol, possess a good grasp of voice fundamentals, and be familiar with at least one of the various call control protocols. If you work with IPT on a consistent basis, you probably already have this knowledge.
Because of this book's comprehensive coverage of fax, modem, and text, it contains relevant information for a wide variety of readers who work with IPT. For anyone who works in IPT network design, such as design engineers, network architects, or systems engineers, this book features a comprehensive design and planning section. If you deploy and install IPT networks, an easy-to-understand configuration section provides the pertinent commands and sample configurations necessary for successfully transporting fax, modem, and text communications. Lastly, for those who support IPT networks, such as customer support engineers, field engineers, network administrators, and escalation engineers, a detailed troubleshooting section equips you with the knowledge and techniques to handle any issue that arises.
If you work with IPT, you will encounter fax, modem, and text devices if you have not already. These devices have special requirements and protocols that must be addressed for successful IP integration and deployment. When it comes time to handle fax, modem, and text communications as part of your job in IPT, this is the one resource that you want by your side.
How This Book Is Organized
This book is logically laid out with critical, fundamental concepts defined at the beginning in Chapters 1 to 6. Later chapters build upon these concepts to assist you with network design, configuration, and troubleshooting. Once the initial fundamental chapters are covered in the first two sections, the remaining chapters do not have to be read in any particular order even though the listed chapter sequence is what we believe to be the most beneficial for learning the subject matter.
The chapters in this book are divided into the following sections and cover the following topics:
Part I: Laying the Groundwork
Provides the fundamentals of how faxes, modems, and text telephony devices work.
Chapter 1, "How Modems Work"—Discusses modem architecture, different modem types, and the methods and modulations used by modems for communication. In addition, a basic modem call is analyzed, including the negotiation phases and data mode.
Chapter 2, "How Fax Works"—Covers the core elements of fax technology, including the common group classifications and standards, an in-depth section on fax messaging, and page encoding.
Chapter 3, "How Text Telephony Works"—Provides an introductory look at text telephony and its fundamantals. Basic text telephony operation and concepts are covered along with a technical discussion of the Baudot text telephone protocol.
Part II: IP Solutions and Design
Describes the various switchover methods and transport options that are used to handle fax, modem, and text communications. Design chapters then help you determine the best solution for transporting your fax, modem, and text traffic.
Chapter 4, "Passthrough"—Shows you the fundamental methods and principles necessary for using a voice codec for transporting fax, modem, and text. The different passthrough methods on Cisco voice gateways and their various switchovers are also discussed.
Chapter 5, "Relay"—Details the intricacies of relay operation and its various transport methods and switchover types for fax, modem, and text.
Chapter 6, "T.37 Store-and-Forward Fax"—Demonstrates the workings and fundamentals of fax and e-mail integration using onramp and offramp faxing.
Chapter 7, "Design Guide for Fax, Modem, and Text"—Provides pertinent design information and best practices for integrating fax, modem, and text telephony into your IP network.
Chapter 8, "Fax Servers"—Concentrates on the design and planning aspects of integrating fax servers into your network. In addition to fax server benefits and integration models, fax server–specific configuration and troubleshooting information is also provided.
Part III: Configuration
Details the configuration tasks for a variety of Cisco products that are essential for transporting fax, modem, and text successfully.
Chapter 9, "Configuring Passthrough"—Provides the configuration commands for enabling passthrough and its various features on Cisco products.
Chapter 10, "Configuring Relay"—Illustrates the numerous commands for successfully configuring the different relay transport methods and features on Cisco products. Also included are IOS voice gateways sample configurations of common deployment scenarios.
Chapter 11, "Configuring T.37 Store-and-Forward Fax"—Breaks down the somewhat confusing T.37 store-and-forward fax configuration process for onramp and offramp into simplified steps. Within each configuration step, the applicable commands are shown.
Part IV: Troubleshooting
Discusses the troubleshooting techniques and procedures used by Cisco TAC engineers for resolving fax, modem, and text issues.
Chapter 12, "Troubleshooting Passthrough and Relay"—Details a fax, modem, and text troubleshooting methodology that efficiently resolves passthrough and relay problems. Each step of this troubleshooting methodology correlates directly to a section within the chapter that shows you the key commands, debugs, and troubleshooting steps to execute for rapidly resolving issues from the most basic to the complex.
Chapter 13, "Troubleshooting T.37 Store-and-Forward Fax"—Highlights graphica...
