IEEE 802.3

The Ethernet Data Link

IEEE 802.3 is a combination of standards and protocols defined by the Institute of Electrical and Electronics Engineers (IEEE). IEEE 802.3 is also known as the Ethernet standard and defines the physical and media access control (MAC) of the data link layer for wired Ethernet networks.

“Ethernet” is the term that is casually applied to a number of very different data link implementations. You will hear people refer to “Ethernet” and they might be referring to the original DEC, Intel, and Xerox implementation of Version 1 or Version 2 Ethernet. This, in a sense, is the “true” definition of “Ethernet”. When the IEEE built the 802.3 standards in 1984 the term “Ethernet” was broadly applied to them as well. Today we talk about “Fast Ethernet” and, although this technology bears many similarities to its predecessors, the engineering technology has changed dramatically.

Whatever you call it, this is a Data Link technology – responsible for delivering a frame of bits from one network interface to another – perhaps through a repeater, switch, or bridge.

Topics In This Discussion

• Frame Formats
  The four ways that frames may be structured
• Media Access
  Taking turns accessing the cable using the rules of Carrier Sense Multiple Access with Collision Detection (CSMA/CD)
• Collisions
  The results of simultaneous transmissions on the media: Fragments, Runts, CRC errors
• Propagation Delay
  The relationship between maximum cable length and minimum frame size is based on the propagation delay of the signal
• Frame Corruption
  Troubleshooting coaxial Ethernet networks by examining the types of corruption patterns that result from specific events
• Interframe Gap
  The 9.6 microsecond interframe gap and an understanding of its purpose
• Signal Encoding
  Manchester Encoding for the electrical Ethernet signal