T1 - A Survival Guide

If you haven't worked with T1 before, you could be in for an unpleasantsurprise. If you have, you'll already know that T1, the current network standard for business and professional Internet access, is neither efficient, easy to use, nor particularly well-suited to data transmission. T1: A Survival Guide, a practical, applied reference on T1 data transport, is a life raft for navigating the shoals of a 40-year-old technology originally designed for AT&T's voice network.

Throughout T1's long life, network administrators have mainly learned it by apprenticeship, stumbling on troubleshooting tidbits and filing them away until they were needed again. This book brings together in one reference the information you need to set up, test, and troubleshoot T1. T1: A Survival Guide covers the following broad topics:

• What components are needed to build a T1 line, and how those components interact to transmit data effectively
• How to use standardized link layer protocols to adapt the T1 physical layer to work with data networks
• How to troubleshoot problems and work with the telephone company, equipment manufacturers, and Internet service providers

In spite of its limitations, T1 is a proven, reliable technology that currently meets the need for medium-speed, high reliability Internet access by institutions of many sizes, and it's likely to be around for a while. T1: A Survival Guide will take the guesswork out of using T1 as a data transport.

Contents

Preface

1: History of the U.S. Telephone Network

1876-1950: Analog Beginnings

1951-1970: The Birth of T-carrier

1970-Present: The Modern Telephone Network

2: T1 Architectural Overview

Telecommunications Puzzle Pieces

3: Basic Digital Transmission on Telephone Networks

Introduction to DS0

Alternate Mark Inversion

B8ZS and Clear Channel Capability

4: Multiplexing and the T-carrier Hierarchy

Building the T-carrier Hierarchy with Multiplexing

The Original Superframe

The Extended Superframe (ESF)

Telephone Signaling on T1 Links

5: Timing, Clocking, and Synchronizationin the T-carrier System

A Timing Taxonomy

T1 Circuit Timing

Slips: When Timing Goes Bad

6: Mysteries of the CSU/DSU

Line Build Out: Moving Between Theory and Practice

T1 CSU/DSUs

CSU/DSU Configuration

Summary of Settings

7: Connecting the Umbilicus: Getting T1 Connectivity

Ordering

T1 Installation and Termination

Pre-Connection Tasks

Trading Packets

Post-Connection

8: High-Level Data Link Control Protocol (HDLC)

Introduction to HDLC

HDLC Framing

Cisco HDLC

9: PPP

Introduction to PPP

PPP Logical Link States and State Machines

PPP Encapsulation and Framing

Link Control Protocol (LCP)

PPP Network Control and the IP Control Protocol

Configuring PPP

10: Frame Relay

Frame Relay Network Overview

The Frame Relay Link Layer

Multiprotocol Encapsulation with RFC 1490

The Local Management Interface

Configuring Frame Relay

11: T1 Troubleshooting

Basic Troubleshooting Tools and Techniques

Troubleshooting Outline

Physical Layer Problems

Link Layer Problems

A: Access Aggregation with cT1 and ISDN PRI

B: Multilink PPP

C: T1 Performance Monitoring

D: SNMP

E: Cable Pinouts and Serial Information

F: Reference

Glossary

Index