Ethernet: The Definitive Guide

Chapter 11. Gigabit Ethernet Twisted-PairMedia System (1000BASE-T)

The specifications for the 1000BASE-T media system were developed in the 802.3ab supplement to the IEEE standard, which was formally adopted in July 1999. Supporting 1 billion bits per second over unshielded twisted-pair (UTP) cable is a remarkable achievement. To make it happen, the 1000BASE-T media system uses a mix of signaling and encoding techniques that were originally developed for the 100BASE-TX, 100BASE-T2 and 100BASE-T4 media standards. While 100BASE-T2 and 100BASE-T4 were not widely adopted in the marketplace, their technology was used in developing the 1000BASE-T standard.

The 100BASE-T2 Fast Ethernet standard is based on a complex signal encoding system used to send 100 Mbps signals over two pairs of Category 3 cable. These techniques were adopted and extended by the 1000BASE-T standard for use over four pairs of Category 5 cable. From the 100BASE-T4 system, the 1000BASE-T standard adopted the technique of simultaneously sending and receiving signals over the same wire pairs. The 1000BASE-T system also adopted the line signaling rate of the very popular 100BASE-TX Fast Ethernet system. Maintaining the same line signaling rate makes it possible for 1000BASE-T to work over the same widely used Category 5 cabling that supports a 100BASE-TX link.

This chapter describes the signaling and media components used in the 1000BASE-T system. We also show how a station is connected to a 1000BASE-T segment, and provide ...