Standards Overview

Like most protocols, Ethernet began life inside a corporation that was looking to solve a specific problem. Xerox needed an effective way to allow a new invention, called the personal computer, to be connected in its offices. From that, Ethernet was born. (Look at inventors.about.com/library/weekly/aa111598.htm for an interesting story on the history of Ethernet.) Eventually, Xerox teamed with Intel and Digital Equipment Corp. (DEC) to further develop Ethernet, so the original Ethernet became known as DIX Ethernet, meaning DEC, Intel, and Xerox.

The IEEE began creating a standardized version of Ethernet in February 1980, building on the work performed by DEC, Intel, and Xerox. The IEEE Ethernet specifications that match OSI Layer 2 were divided into two parts: the Media Access Control (MAC) and Logical Link Control (LLC) sublayers. The IEEE formed a committee to work on each part—the 802.3 committee to work on the MAC sublayer, and the 802.2 committee to work on the LLC sublayer.

Table 3-3 lists the various protocol specifications for the original three IEEE LAN standards, plus the original prestandard version of Ethernet.

Table 3-3 MAC and LLC Standards for Three Types of LANs

Name

MAC Sublayer Spec

LLC Sublayer Spec

Ethernet Version 2 (DIX Ethernet)

Ethernet

IEEE Ethernet

IEEE 802.3

IEEE 802.2

IEEE Token Ring

IEEE 802.5

IEEE 802.2

ANSI FDDI

ANSI X3T9.5

IEEE 802.2

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