T1: A Survival Guide

If you haven't worked with T1 before, you could be in for an unpleasant surprise. 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.

The T1 line and its predecessors were developed as long-distance voice trunks, but now they're used almost exclusively as data connections for large and mid-sized organizations. In part because they've been adapted to fill a new role, T1 lines make use of complicated signaling and linking protocols. What's more, T1 technology has a lot to do with the public telephone network, which means most router jockeys and other "data people" lack the background they need to speak intelligently with engineers at T1 providers. T1: A Survival Guide explains leased T1 data circuits for the benefit of the lessee--in other words, for the telephone company's customer. The book is also useful for telco people who want to understand where their clients are coming from when they ask "elementary" questions.

The truth be told, this book probably won't enable organizational network administrators to fix any but the most basic problems with their T1 lines and the Customer Premises Equipment (CPE) associated with them. It is nonetheless a worthwhile read. Matthew Gast, who works on the ever-blurring border between voice and data as an engineer at Nokia, explains how a Channel Service Unit/Data Service Unit (CSU/DSU) works and provides a ton of information about the protocols that communicate data over T1 links (including HDLC, Cisco-enhanced HDLC, PPP, and Frame Relay). Lots and lots of bit diagrams, signal tables, and pictorial representations of networks clarify T1 as much as possible. --David Wall

Topics covered: The T1 line as a high-capacity carrier of digital data, with coverage of multiplexing and other aspects of T1 architecture, as well as High Level Data Link Control Protocol (HDLC), Point-to-Point Protocol (PPP), and Frame Relay. There's excellent coverage of how to order a T1 from a telephone company (as well as how to figure out if you need more than one), and a guide to working with telco engineers during install and troubleshooting.