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Fax, Modem, and Text for IP Telephony

Book 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® 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

    Table of Contents

    1. Copyright
      1. Dedications
    2. About the Authors
    3. About the Technical Reviewers
    4. Acknowledgments
    5. Icons Used in This Book
    6. Command Syntax Conventions
    7. Introduction
      1. Target Release: Cisco IOS Software Version 12.4(9)T1
      2. Goals and Methods
      3. Who Should Read This Book?
    8. How This Book Is Organized
      1. Comments for the Authors
      2. Further Reading
        1. Cisco.com
          1. Voice over IP Fundamentals, Second Edition
          2. Troubleshooting Cisco IP Telephony
    9. I. Laying the Groundwork
      1. 1. How Modems Work
        1. A Brief History of Modems
        2. Modem Architecture
        3. Modem Types
          1. External Versus Internal Modems
          2. Hardware Versus Software Modems
          3. Fax Modems
        4. Terminal-to-Modem Communication
          1. DTE and DCE
          2. RS-232 Signaling
          3. Asynchronous Framing
          4. User Interface
        5. Modem-to-Modem Communication
          1. Modulation
            1. Frequency Shift Keying (FSK)
            2. Phase Shift Keying (PSK)
            3. Amplitude Modulation (AM)
            4. Quadrature Amplitude Modulation (QAM)
            5. Trellis Coded Modulation (TCM)
          2. Modulation Standards
        6. Modem Call Analysis
          1. Call Setup
            1. Phase I: Network Interaction
            2. Phase II: Probing/Ranging
            3. Phase III: Equalizer and Echo Canceller Training
            4. Phase IV: Final Training
          2. Data Mode
            1. Retrains and Speedshifts
            2. Error Control
            3. Data Compression
          3. Call Disconnect
        7. Summary
      2. 2. How Fax Works
        1. A Brief History of Fax
        2. Fax Components
        3. Group Classifications
        4. Specifications and Standards
        5. Fax Modulations
        6. Fax Messaging
          1. Phases of a Fax Call
          2. Message Format Overview
          3. Analyzing a Basic Fax Call
            1. CNG Tone
            2. CED Tone
            3. DIS, NSF, and CSI Messages
            4. DCS and TSI Messages
            5. TCF, CFR, and FTT Messages
            6. MPS, EOP, EOM, MCF, RTP, RTN, and DCN Messages
            7. Other T.30 Messages
          4. Understanding Error Correction Mode
            1. ECM Call Analysis
            2. PPS and PPR
          5. Important G3 Timers
          6. Super G3 Faxing
            1. Comparison of SG3 and G3
            2. Super G3 Call Analysis
        7. Page Encoding
          1. Modified Huffman
          2. Modified READ
          3. Modified Modified READ
        8. Summary
      3. 3. How Text Telephony Works
        1. A Brief History of Text Telephony
        2. Text Telephone Terminology
        3. Standards and Specifications
          1. Carrier Based Versus Carrierless Protocols
          2. ITU-T Recommendation V.18
        4. Text Telephone Operation
          1. Acoustic Coupling Versus Direct Connections
          2. Originating and Receiving Text Telephone Calls
          3. Conversation Conventions
          4. Text Telephone Relay Services
          5. HCO (Hearing Carry Over)
          6. VCO (Voice Carry Over)
        5. Baudot Protocol
          1. Baudot Character Set
          2. Baudot Modulation Details
        6. Summary
    10. II. IP Solutions and Design
      1. 4. Passthrough
        1. Passthrough Fundamentals
        2. NSE-Based Passthrough
          1. Fax Passthrough with NSE
          2. Modem Passthrough with NSE
        3. Protocol-Based Pass-Through for Fax
          1. Fax Pass-Through with H.323 Signaling
          2. Fax Pass-Through with SIP Signaling
        4. Text over G.711
        5. A Future Look at ITU-T V.152
        6. Summary
      2. 5. Relay
        1. Relay Fundamentals
        2. Fax Relay
          1. T.38 Fax Relay
            1. NSE-Based Switchover for T.38
            2. Protocol-Based Switchover for T.38
          2. Cisco Fax Relay
        3. Modem Relay
        4. Cisco Text Relay
        5. A Future Look at ITU-T T.38, V.150.1, and V.151
        6. Summary
      3. 6. T.37 Store-and-Forward Fax
        1. Overview of T.37 Store-and-Forward Fax
        2. SMTP Overview
          1. SMTP Commands and Sample Sessions
          2. DSN and MDN
        3. T.37 Onramp
        4. T.37 Offramp
        5. Summary
      4. 7. Design Guide for Fax, Modem, and Text
        1. General Passthrough and Relay Design Considerations
          1. Bandwidth
          2. Call Control Protocol
          3. QoS
          4. Redundancy
          5. Resource Utilization
          6. Secure RTP
          7. Timing and Synchronization
        2. Fax Design Considerations
          1. Gateway Interoperability Considerations
          2. Error Correction Mode
          3. Super G3
          4. Hairpin Calls
          5. Fallback
          6. T.37 Store-and-Forward Fax
          7. Fax Detect Script
          8. Unified CM Integration
          9. Comparing Fax Passthrough and Fax Relay
        3. Modem Design Considerations
          1. Comparing Modem Passthrough and Cisco Modem Relay
          2. Secure Modem Relay
        4. Text Design Considerations
        5. Summary and Best Practices
      5. 8. Fax Servers
        1. Fax Server Basics
        2. Fax Server Integration Solutions
          1. Fax Server TDM Integration with a Cisco Voice Gateway
          2. Fax Server T.38 Integration with a Cisco Voice Gateway
          3. Fax Server T.38 Integration with Unified CM
        3. Fax Server Redundancy and Failover
        4. Summary
    11. III. Configuration
      1. 9. Configuring Passthrough
        1. IOS Gateway Passthrough Configuration
          1. IOS Gateway NSE-Based Passthrough Configuration
            1. IOS Gateway NSE-Based Passthrough Configuration for H.323, SIP, and SCCP
            2. IOS Gateway NSE-Based Passthrough Configuration for MGCP
          2. IOS Gateway Protocol-Based Pass-Through Configuration
          3. IOS Gateway Text over G.711 Configuration
        2. 6608 Catalyst Blade Passthrough Configuration
        3. VG248 Passthrough Configuration
        4. ATA Passthrough Configuration
        5. Summary
      2. 10. Configuring Relay
        1. IOS Gateway Relay Configuration
          1. Fax Relay
            1. IOS Gateway Fax Relay Configuration for H.323, SIP, and SCCP
            2. IOS Gateway Fax Relay Configuration for MGCP
          2. Modem Relay
            1. IOS Gateway Cisco Modem Relay Configuration for H.323, SIP, and SCCP
            2. IOS Gateway Cisco Modem Relay Configuration for MGCP
          3. Cisco Text Relay
          4. IOS Example Configurations for Relay
            1. Default Fax Relay Configuration for H.323 and SIP
            2. Cisco Fax Relay and Modem Passthrough Configuration for H.323 and SIP
            3. T.38 Fax Relay, Cisco Modem Relay, and Cisco Text Relay Configuration for H.323 and SIP
            4. T.38 Fax Relay and Cisco Text Relay Configuration for SCCP
            5. T.38 Fax Relay and Modem Passthrough Configuration for MGCP
        2. 6608 Catalyst Blade Fax Relay Configuration
        3. VG248 Fax Relay Configuration
        4. Summary
      3. 11. Configuring T.37 Store-and-Forward Fax
        1. Enabling T.37 Store-and-Forward Fax
        2. Loading the TCL Scripts
        3. Configuring T.37 Onramp Fax
          1. Dial-Peer Configuration for Onramp Fax
          2. Fax Receive Configuration Command for Onramp Fax
          3. MTA Configuration Commands for Onramp Fax
          4. Sample Onramp Configuration
        4. Configuring T.37 Offramp Fax
          1. Dial-Peer Configuration for Offramp Fax
          2. Fax Send Configuration Commands for Offramp Fax
          3. MTA Configuration Commands for Offramp Fax
          4. Sample Offramp Configuration
        5. Summary
    12. IV. Troubleshooting
      1. 12. Troubleshooting Passthrough and Relay
        1. Attacking the Problem
        2. Fundamental Troubleshooting
          1. Checking the Condition of Originating and Terminating Devices
          2. Testing with Voice Calls
          3. Testing with PSTN Calls
          4. Confirming the Configuration
          5. Debugging Best Practices
        3. Telephony and IP Troubleshooting
          1. Call Legs in IOS Gateways
          2. Viewing Call Legs
            1. Modem Passthrough Call Legs
            2. Fax Pass-Through Call Legs
            3. Fax Relay Call Legs
            4. Cisco Modem Relay Call Legs
            5. Text Telephony Call Legs
            6. Call Leg Troubleshooting Techniques
          3. Telephony Troubleshooting
          4. IP Troubleshooting
            1. IP Troubleshooting for IOS Gateways
            2. IP Troubleshooting for Non-IOS Gateways
            3. IP Troubleshooting Using Packet Captures
        4. Troubleshooting the Switchover Signaling
          1. Troubleshooting NSE-Based Switchovers
            1. NSE-Based Switchover for Modem Passthrough
            2. NSE-Based Switchover for Cisco Modem Relay
            3. NSE-Based Switchover for T.38 Fax Relay
            4. Validating NSE Switchover Support
          2. Troubleshooting Protocol-Based Switchovers
            1. Protocol-Based Fax Pass-Through and T.38 Switchovers for H.323
            2. Protocol-Based Fax Pass-Through and T.38 Switchovers for SIP
            3. Protocol-Based T.38 Switchover for MGCP
            4. Protocol-Based Switchovers and Unified CM
          3. Troubleshooting the Cisco Fax Relay Switchover
        5. Passthrough and Relay Troubleshooting
          1. Troubleshooting DSP Functions
            1. DSP HPI Troubleshooting
              1. HPI Debugs for Fax Relay
              2. HPI Debugs for Cisco Modem Relay
              3. HPI Debugs for Passthrough
            2. Loss Planning
          2. Advanced Troubleshooting for Passthrough
          3. Advanced Troubleshooting for Fax Relay
            1. Fax Relay Data Rate
            2. Dealing with Packet Loss
            3. SG3
            4. Debugging T.30 Fax Messaging
            5. Analyzing T.38 Fax Relay Packet Captures
            6. NSF/NSS
            7. Handling High Delay
          4. Advanced Troubleshooting for Modem Relay
            1. Checking the Modem Endpoints
            2. Debugging Modem Relay
          5. Advanced Troubleshooting for Cisco Text Relay
          6. PCM Traces for Fax and Modem
            1. Capturing PCM Traces
              1. Cisco PCM Capture Tool
              2. Packet Capture PCM Extraction
              3. Third-Party Test Tools
            2. Analyzing PCM Traces
              1. Fax Call PCM Trace Analysis
              2. Modem Call PCM Trace Analysis
        6. Summary
      2. 13. Troubleshooting T.37 Store-and-Forward Fax
        1. Checking the Basics
        2. T.37 Onramp Troubleshooting
          1. Troubleshooting the Onramp Telephony Interface
          2. Troubleshooting the TIFF Image Creation
          3. Troubleshooting the Onramp SMTP Connection
        3. T.37 Offramp Troubleshooting
          1. Troubleshooting the Offramp SMTP Connection
          2. Troubleshooting the Creation of the Fax Page Image
          3. Troubleshooting the Offramp Telephony Interface
        4. Summary