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802.3 vs Ethernet

joshuaflinn
Level 1
Level 1

I was asked this morning what the difference is between 802.3 and Ethernet. I said there wasn't a difference and I was told I was wrong. Is there a difference and what is it?

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dnewell24
Level 1
Level 1

Frame wise there is a difference. DIX (Dec, Intel, and Xerox) created the first published Ethernet standard the name of the frame was Ethernet V1. This frame consisted of Preamble-DST MAC-SRC MAC-16 bit length field. Today's version Ethernet version today replaces the length field with an EtherType value.

Shortly after DIX published their standard IEEE published the IEEE 802.3 CSMA/CD based on DIX's Ethernet adding in CSMA/CD. Being that IEEE was an open standards committee they didn't want to use a commercial name (Ethernet) which might imply that they were indorsing a company. This frame type uses the length instead type. It adds LLC or LLC w/SNAP to identify the upper layer protocol.

Another difference is that IEEE 802.3 divides the preamble into two sections. 56 bit preamble and 8 bit start-frame sequence that has a 10101011 pattern. Ethernet V2 calls the entire 64 bits preamble.

You should read The Definitive Guide to Ethernet by Charles E. Spurgeon and Troubleshooting Campus Networks by Priscilla Oppenheimer and Joseph Bardwell. They are good books. I pulled most of the info from these books.

HTH

Ryan

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