T1: A Survival Guide

Physical Layer Standards

Much of this book is about physical networks. Several standards apply to the physical-transmission medium, many of which were originally derived from AT&T technical publications.

DS0 (DDS)

Although 56/64-kbps leased lines, also known as DDS leased lines, were not a major component of this book, much of the information presented about T1 can be applied to them. These two standards define the DS0:

AT&T Technical Publication 62310

Offering low-speed (56/64 kbps) leased lines was one of AT&T’s original data services and is defined in this publication.

ANSI T1.410

Carrier to Customer Metallic Interface—Digital Data at 64 kbit/s and Subrates”

ANSI followed up the previous publication with its own additions to the initial AT&T engineering work.

DS1 Standards

AT&T laid the foundations for T1 networking. As a result, two AT&T technical publications lay the foundation for subsequent engineering standards:

AT&T Technical Publication 62411

This publication defines the SF (D4) format and T1 line characteristics.

AT&T Technical Publication 54016

This publication extended T1 technology by defining ESF framing and the first use of the FDL. The FDL specification in T1.403 is more useful because it is based on periodic messaging rather than this publication’s command/response system.

ANSI T1.403

“Network and Customer Installation Interfaces—DS1 Electrical Interface”

This is the modern T1 line specification. In addition to including the technical details from the previous ...