Origin of Ethernet: ALOHA Radio System The core idea of ??Ethernet is to use a shared public transmission channel.

The idea of ??sharing data transmission channels originated from the University of Hawaii.

In the late 1960s, Norman Abramson and his colleagues at the school developed a radio network called the ALOHA system.

The terrestrial radio system was developed to connect the school's IBM 360 mainframe on the island of Oahu to card readers and terminals located on other islands and on ocean vessels.

The system's initial speed was 4800 bps and was eventually upgraded to 96O0 bps.

The unique feature of this system is that it uses "inbound" and "outbound" radio channels for two-way data transmission.

The outbound radio channel (from the host computer to the distant island) is fairly simple and straightforward, just put the destination address in the header of the transmitted message and it is then decoded by the corresponding receiving station.

The inbound radio channel (from the island or ship to the host) is complex, but interesting, and uses a randomized retransmission method: the secondary station (the one on the island) sends it out after the operator hits the Return key

message or information packet, and then the station waits for the main station to send back a confirmation message; if no confirmation message is returned on the outbound channel within a certain time limit (200 to 1500 nanoseconds), the remote station (secondary station)

) will think that two stations are trying to transmit at the same time, so a collision occurs, causing the transmission data to be destroyed. At this time, both stations will choose a random time again and try to resend their information packets. At this time, the certainty of success is very

This type of network is called a contention network because different stations are competing for the same channel.

This contention-based network has two meanings: This mode allows multiple nodes to transmit accurately on the same channel in a simple and flexible way.

The more stations using the channel, the higher the chance of collisions, resulting in increased transmission delays and reduced information throughput.

Norman Abramson published a series of articles on the theory and application of the ALOHA system. One of the articles in 1970 elaborated on the mathematical model for calculating the theoretical capacity of the ALOHA system.

This model is now known as the classic ALOHA model, which estimated that the theoretical capacity of the ALOHA system reached a theoretical efficiency of 17%.

In 1972, ALOHA was improved into the slotted ALOHA group broadcast system through simultaneous access, more than doubling the efficiency.

The work developed by Abramson and colleagues has become the basis for most packet broadcast systems in use today, including Ethernet and various satellite transmission systems.

In March 1995, Abramson received the IEEE's Kobaya Shi Award for his pioneering research work on contention-based systems.

Xerox PARC Creates the First Ethernet Ethernet as we know it today was pioneered in 1972, when Bob Metcalfe came to work in the computer science laboratory of Xerox Palo Alto Research Center (PARC), a well-known research institution in the world.

In 1972, PARC researchers had invented the world's first laser printer named EARS and the first PC with a graphical user interface named ALTO.

At that time, Metcalfe had been hired by Xerox as a network expert at PARC. His first job was to connect the Xerox ALTO computer to Arpanet (Arpanet was the predecessor of the Internet).

In the fall of 1972, Metcalfe was visiting Arpanet program administrators living in Washington, D.C., and came across Abramson's dry-phase research on the ALOHA system.

While reading Abramson's famous 1970 paper on the ALOHA model, Metcalfe realized that although Abramson had made certain questionable assumptions, the efficiency of the ALOHA system could be increased to nearly 100% through optimization.

Finally, Metcalfe received a PhD in science from Harvard University for his theory of packet-based transmission.

In late 1972, Metcalfe and David Boggs designed a network to connect different ALTO computers, and then connected the NOVA computer to the EARS laser printer.

During the development process, Metcalfe named his project the ALTO ALOHA network because the network was based on the ALOHA system and connected numerous ALTO computers.

The world's first personal computer local area network, the ALTO ALOHA network, first started operating on May 22, 1973.

On this day, McCalfe wrote a memo stating that he had renamed the network Ethernet, inspired by "the idea that electromagnetic radiation can be spread through the luminous ether."