IEEE802.3 - Ethernet

There is a lot of confusion about Ethernet and the many different versions of it. This page hopes to clear up some fundamental misunderstandings about it. First some history: the IEEE-802.3 Protocol was based on the Xerox Network Standard (XNS) called Ethernet developed over in Hawaii for the Aloha network. The XNS version of Ethernet is obsolete and hasn't been used since the 1980s. So if you read about Ethernet with references to Xerox and the Aloha network then you know that you are reading historical documentation. Take a quick look at Wikipedia's IEEE 802.3 wiki page to see the incredible confusing list of Ethernet standards - then come back to find out what is really used.

There's a clear dividing line with the different flavours of Ethernet that make it easy to learn and understand the operation. The moment of truth was when 100BaseT came out or as it is more commonly known now: FastEthernet. FastEthernet was one major breakthrough not only because of the higher throughput of 100 Mbps but because it was a full duplex protocol. You could receive and transmit data at the same time - equivalent to 200 Mbps! Earlier versions of Ethernet were only half duplex running at 10 Mbps in one direction at a time. But there was another major breakthrough that played a very important part: Ethernet Switching technology.

FastEthernet gave us the speed and Ethernet switches provided a collision free network connection. Ethernet switches made the bus arbitration method of CSMA/CD (Carrier Sense, Multiple Access/Collision Detect) obsolete and solved a lot of problems along the way. With the introduction of these two milestones, all of the earlier Ethernet standards were made obsolete.

The IEEE802.3 - Ethernet section is divided into the following pages:

Circuit Switched - This page talks about the latest LAN technologies: 100BaseT (FastEthernet), 1000BaseT (GigaEthernet) and 10GBaseT (10 Gbps Ethernet). There's faster versions of Ethernet called Carrier Ethernet (40 Gbps and 100 Gbps) used by telcos and service providers that are used for Wide Area Networks (WANs) but that is out of the scope of this site for now.

Media Access Control (MAC) layer - This is the layer that deals with MAC addressing, building the Ethernet frame, populating the fields, putting the bits in order and deciding who's turn it is to talk (bus arbitration).

Legacy Ethernet - This section discusses the obsolete and scientific research Ethernet standards that just confuse the issue. It also explains the CSMA/CD bus arbitration made obsolete by circuit switching Ethernet.

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Copyright July 2013 Eugene Blanchard