JUNOS Enterprise Switching

Ethernet Technologies

Ethernet has been around for so long, and is now so widely used, that a complete overview would easily fill its own book. The goal here is to stay concise and to convey only key points to clear up areas that are known to cause confusion.

A Brief Look Back

The philosopher George Santayana one stated, “Those who do not remember their past are condemned to repeat their mistakes.” It is to him that we dedicate this section. Well, him and everyone else who fell prey to buying into now-obsolete market failures such as ATM, Token Ring, FDDI, Token Bus, ARCnet, TCNS, or SMDS. All sought to solve the needs of high-speed communications over a shared medium, and all are now only footnotes in history—a history that is penned by the victorious Ethernet.

Ethernet v2 is a de facto standard first published by the Digital, Intel, and Xerox vendor alliance. It was based on a prototype satellite communications network called ALOHAnet. When Bob Metcalf later adapted the technology to run over coaxial cable in the early 1970s, the term Ether was used to pay homage to its original use of electromagnetic radiation through the vacuum of space, whereby the alleged media was the mythical luminiferous ether, a substance that the ancient Greeks believed conducted the planets through their orbits.

When used for minicomputers, LANs were a novelty. Enter the IBM PC in the early 1980s, and suddenly LANs are a hot commodity. The official standards bodies could not stand by and watch a vendor consortium ...