The core idea of Ethernet is to use the common transmission channel shared by * *. * * * The idea of sharing data transmission channels comes from the University of Hawaii. In the late 1960s, Norman abrams and his colleagues developed a radio network called ALOHA system. This terrestrial radio broadcasting system was developed to connect the IBM360 mainframe in our school campus on Oahu with the card readers and terminals distributed on other islands and marine ships. The initial speed of the system is 4800 bps, and finally it is upgraded to 96O0 bps. The uniqueness of the system lies in the use of "inbound" and "outbound" radio channels for two-way data transmission. The outbound wireless channel (from the host to the distant island) is quite simple, as long as the destination address is put in the header of the sent message and then decoded by the corresponding receiving station. The inbound wireless channel (from island or ship to host) is complex, but interesting. It adopts a randomized retransmission mode: after the operator presses the enter key, the sub-station (the station on the island) sends its message or packet, and then the station waits for the main station to send back the confirmation message; If no confirmation message is returned on the outbound channel within a certain time limit (200 to 1500 nanoseconds), the remote station (substation) will think that two stations are trying to transmit at the same time, thus colliding and destroying the transmitted data. At this point, the two stations will choose a random time again and try to retransmit their packets. At this time, success will be great.
This competition-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 use this channel, the higher the probability of collision, resulting in an increase in transmission delay and a decrease in information flow.
Norman Abramson published a series of articles on the theory and application of ALOHA system, among which one article in 1970 elaborated the mathematical model for calculating the theoretical capacity of ALOHA system in detail. Now this model is famous for its classic Aloha model. At that time, it was estimated that the theoretical capacity of ALOHA system reached 17% theoretical efficiency. 1972, ALOHA is improved into slotted ALOHA group broadcasting system through synchronous access, and the efficiency is more than doubled.
The research results of Abramson and his colleagues have become the basis of most packet broadcasting systems currently in use, including Ethernet and various satellite transmission systems. 1In March, 1995, Abramson won the Kobayashi Award of IEEE for his pioneering research work in competition-based systems.
Xerox PARC made the first Ethernet.
Ethernet as we know it today was established in 1972 when bob metcalfe came to work in the computer science laboratory of Xerox Palo Alto Research Center (PARC), a world-famous research institution. 1972 PARC researchers invented the world's first laser printer named EARS and the first personal computer named ALTO with a graphical user interface. At that time, Metcalfe was hired by Xerox as a network expert of PARC. His first job was to connect Xerox ALTO computer to ARPANET (ARPANET is the predecessor of the Internet). 1972 In the autumn, Metcalfe visited the project manager of ARPANET who lived in Washington, D.C., and came across abramson's research results on Aloha system in dry season. When reading Abramson's famous paper 1970 on ALOHA model, Metcalfe realized that although Abramson made some questionable assumptions, the efficiency of ALOHA system could be improved to close to 100% through optimization. Finally, Metcalfe received a doctor of science degree from Harvard University for his packet-based transmission theory.
1at the end of 972, Metcalfe and David Boggs designed a network to connect different Alto computers, and then connected the NOVA computer to the EARS laser printer. In the process of development, Metcalfe named his work ALTO ALOHA network, because the network is based on ALOHA system and connected with many ALTO computers. The world's first personal computer local area network-ALTO ALOHA network started its first operation on May 22nd, 1973. On this day, Mctcalfe wrote a memo saying that he renamed the network Ethernet, which was inspired by "the idea that electromagnetic radiation can be transmitted through glowing Ethernet". The initial experimental PARC Ethernet runs at 2.94Mbps (megabits per second), which is a bit fragmented. The reason is that the interface timer of the first Ethernet uses the ALTO system clock, which means that a pulse is sent every 340 nanoseconds, resulting in a transmission rate of 2.94Mbps. Of course, Ethernet is greatly improved over the original ALOHA network, because the characteristic of Ethernet is carrier monitoring. That is, each station must listen to the network before sending its own data stream. Therefore, an improved retransmission scheme can improve the network utilization by nearly 100%. By 1976, PARC's experimental Ethernet had grown to 100 nodes, and had been running on 1000 meter thick coaxial cable. Xerox was eager to turn Ethernet into a product, so it changed its name to Xerox Cable. However, in 1979, when DEC, Intel and Xerox *** standardized this network, the name Ethernet was restored. 1In June, 1976, Metcalfe and Boggs published a famous paper entitled Ethernet: Distributed Packet Switching in LAN. At the end of 1977, Metcalfe and his three collaborators obtained the patent of "Multipoint Data Communication System with Collision Detection", and the multipoint transmission system was called CSMA/ CD (Carrier Sense Multiple Access and Collision Detection). Since then, Ethernet was formally born.
DEC, InteI and Xerox standardize Ethernet.
At the end of 1970s, dozens of LAN technologies appeared, and Ethernet was one of them. Besides Ethernet, the most famous networks at that time were MCA of Data General Company, Hyperchannel of Network Systems Company, ARCnet of Data' Point Company and Omninet of Corvus Company. It is not her technical advantages and speed that make Ethernet finally sit on the throne of LAN, but the Ethernet version of Metcalfe has become the industry standard.
1979 At the beginning of this year, Metcalfe, who returned to PARC Xerox after leaving for two years, received a phone call from Gordon Bell who worked at DEC. Bell wanted to discuss the idea of establishing an Ethernet LAN with DEC and Xerox. Metcalfe thinks it's a good idea to develop Ethernet with different manufacturers, but there is nothing Metcalfe can do at this time, because Xerox wants to protect its own patents and restrict Metcalfe from working for DEC, so Metcalfe suggested that DEC directly discuss with Xerox executives the plan to turn Ethernet into an industry standard, and Xerox finally took this step. ?
One of the obstacles to the cooperation between DEC and Xerox in industrial standards is the anti-monopoly law. Howard Charney, a lawyer who is Metcalfe's friend at MIT, suggested that he transfer the real Ethernet technology to the standardization organization (Charney soon became one of the founders of 3Com). ?
While visiting NBS in Washington, D.C., Metaclfe met an Intel engineer working in NBS, who was looking for new applications for his advanced 25MHz VLSI NMOS integrated circuit processing technology. The advantages of this Julien Bihe company are obvious: Xerox provides technology, DEC has strong technical force, and it is a strong supplier of Ethernet hardware. Intel provides Ethernet chip components. Metcalfe soon left Xerox to become an entrepreneur and broker. 1July, 1979, DEC, Intel and Xerox prepared to hold a tripartite meeting, and the first tripartite meeting was formally held in 1979. 19801On February 30th, Intel and Xerox published the third draft of "Ethernet, a local area network: data link layer and physical layer specifications, version 1.0", which is now the famous blue book of Ethernet, that is, DIX (composed of the initials of three companies) version/kloc. As mentioned above, the initial experimental Ethernet worked at 2.94Mbps, while DIX started working at 20Mbps and finally dropped to 10Mbps. In the next two years, DIX redefined the standard and published the Ethernet version 2.0 specification in 1982 as the end. ?
While DIX is standardizing Ethernet, IEEE, a global professional organization, has set up a committee to define and promote industrial LAN standards, with office environment as the main goal. This committee is called Project 802. Although DIX Group has published the Ethernet specification, it is still not an internationally recognized standard. Therefore, in June of 198 1, the IEEE802 project decided to set up an 802.3 sub-committee to produce an internationally recognized standard based on the work results of DIX. A year and a half later, it was 1982 19. 1983 The draft was finally published as IEEE 10 BASE5. (The abbreviation 10BASE5 is chosen because the standard stipulates that the transmission rate using baseband is 10MbpS and the distance between nodes is 50m. There is a technical difference between 802.3 and DIX Ethernet 2.0, but this difference is very small. Today's Ethernet and 802.3 can be regarded as synonyms. During this period, Xerox has transferred four of them to IEEE under the patent of Ethernet, so now anyone can get an Ethernet license from IEEE at the price of $65,438+$0,000. In 1984, the American federal government adopted the 802.3 standard in the name of FIPS Public 107. 1989 ISO adopts the 802.3 Ethernet standard with the standard number IS88023. So far, IEEE standard 8O2.3 has been officially recognized internationally.
3Com productized Ethernet
While engineers from DEC, Intel and Xerox were still completing the Ethernet specification, Metcalfe was already seeking other commercial interests, and Jing rejected Steve Jobs' suggestion to join Apple in developing the network. From June 65438 to June 0979, bob metcalfe, Howard Chaney, Ron Crane, Greg Shaw and Bill Krause formed a computer communication and compatibility company, which is now the famous 3Com company.
1980 In August, 3 Com Company announced its first product, namely the commercial version of TCP/IP for Unix. This product was officially listed in February of 1980, and a grand business plan was made in February of 198 1. 3 Com has obtained a lot of venture capital. In 198 1, that is, 18 months before the official standard was officially announced, 3Com has put its first batch of products (3C 100 transceivers) conforming to the 802 standard on the market. 198 1 At the end of the year, the company began to sell transceivers and cards of DECPD/11+0 series and VAX series, as well as transceivers and cards of Intet Multibus and Sun Microsystems.
Metcalfe's original business plan is to invest 1980 venture capital to develop Ethernet adapters for new personal computers, because new personal computers have just sprung up all over the world. In 198 1 year, Metcalfe negotiated with all major PC companies (including IBM and Apple) to establish Ethernet adapters. Steve Jobs, who works at Apple, immediately agreed. A year later, the first Ethernet products configured by 3Com for Apple computers were put on the market. This Ethernet device named Apple Boxes is a clumsy chassis connected to Apple II parallel port, which ended in failure in the market. IBM, which has always been famous for creating history, also announced the original IBM PC at that time, but because IBM was busy inventing its own token ring network, it did not cooperate with 3Com. However, 3Com decided to push ahead with its plan without IBM's cooperation, and began to develop EtherLink ISA adapters. 18 months later, that is,1September 29, 982, the first EtherLink went on the market, and the corresponding DOS driver software was randomly configured.
The first Ethernet link made technical breakthroughs in many aspects:
Ethernet network card can be realized by silicon semiconductor integration process. 1983, 3Com became a partner of the newly established Seeq technology company. Seeq company promises to make a silicon chip contain most discrete controller functions in its VLSI technology, thus reducing the number of components on the printed board and its cost, and leaving enough space for the assembly of transceivers on the printed board. In the middle of 1982, EtherLink became the first network interface card (NIC)-seeq8001containing the silicon chip of Ethernet VLSI controller.
More importantly, EtherLink became the first Ethernet ISA bus adapter of IBM PC, which was a milestone in the development history of Ethernet. Because of the low price of Seeq silicon chip, 3Com can sell EtherLink for $950, which is much cheaper than other cards and transceivers sold before.
Before the introduction of EtherLink adapters, all Ethernet devices were characterized by an external MAU transceiver, which was connected to the thin coaxial cable of Ethernet. Because VLSI chip saves a lot of space, the transceiver can be integrated on the card. Because of the shortcomings of traditional thick coaxial cable, 3Com Company also adopted a new thin cable routing method.
Ron Crane, the designer of Ethernet, invented a basic concept called thin cable Ethernet, which soon became the de facto standard. This thin cable Ethernet has many advantages: it does not need additional transceiver and transceiver cable, and it is cheap. Because thin coaxial cable is easy to install and use, it makes the network more user-friendly. ?
Metcalfe decided to target IBM PC, which benefited 3Com a lot. At that time, IBM designed IBM PC mainly as a home computer; However, it was companies, not home users, that started buying PCs in large quantities. 1982, the demand for PC exceeded the forecast. IBM sold 200,000 PCs in a month, twice the company's initial forecast, which made IBM's factory work overtime, and it took two and a half years to meet the market demand in one year. 198 1 at the beginning of the year, IBM XT went public. At this time, IBM has occupied 75% of the PC business market. Unfortunately, IBM didn't realize that the company wanted to connect their personal computers to the Internet. By 1983, the business of Ethernet was booming, and 3Com's stock was listed on 1984. In the same year, 3Com, ICL (International Computer Co., Ltd.) and Hewlett-Packard submitted the concept of thin cable Ethernet to IEEE, and soon IEEE recognized it as the official standard together with l0BASE2. Because the distance from node to node is shortened to 200 meters, the standard is called10base2; ; In addition, it is also called Cheapernet because it uses cheap thin coaxial cable.
Good idea, but too slow?
Thin cable Ethernet is superior to traditional Ethernet in many aspects. Thin cable Ethernet replaces expensive yellow thick coaxial cable with cheap and flexible thin coaxial cable. In addition, most thin cable Ethernet interface cards (NICs) have built-in transceivers, which makes them easy to install and reduce costs.
However, thin cable Ethernet still has some main shortcomings, such as the coaxial cable breaking due to accidents or some carelessness of users (which often happens), which leads to the paralysis of the whole network. In addition, both ends of the network need to be terminated correctly, and network reconfiguration is a problem-if users move physically, they must rewire the network cables accordingly, which is often inconvenient and prone to accidents.
At the end of 1983, Bob Garin of Intel Corporation began to cooperate with AT&T and NCR to study the operation of Ethernet on unshielded twisted pair (UTP) telephone lines. NCR suggests adopting a bus structure similar to thin cable Ethernet, while AT&T Telephone Company is keen on a house structure similar to the current telephone wiring structure. The advantages of UTP star configuration are manifold: simple installation, configuration, management and fault finding, low cost; This star layout is a breakthrough, because it allows the use of a structured cabling system, connecting each node to the central hub with a single line, which is obviously an obvious advantage for installation, fault finding and reconfiguration, and can greatly reduce the cost of the whole network.
At the beginning of 1984, 14 company participated in the research activities of UTP Ethernet, and discussed a lot, mainly focusing on how to make fast Ethernet run on UTP line. They confirmed that low-speed Ethernet (l-2Mbps) can run on Category 3 lines and can meet the electromagnetic interference regulations and crosstalk restrictions. However, some dealers strongly opposed to reducing the speed to 10% of the normal Ethernet speed, which soon made many people lose interest, including 3Com and DEC, the two leaders of Ethernet, while other participants thought that 1Mbps was fast enough for IBM PC and XT PC networks. After intense technical discussion, the group voted to restore Ethernet to 1Mbps.
10 company decided to implement lMbps Ethernet and discussed with IEEE. The IEEE802 team entrusted the StarLAN task force headed by Garin to carry out standardization work. 1956, as a new standard of IEEE802.3, 1BASE5 was approved for implementation (StarIAN can support the distance from hub to node as long as 250 meters, and 5 in 1BASE5 means the distance from node to node is 500 meters). ?
Starland is dying.
1984, the distributors led by HP and AT&T introduced the StarLAN hub network card to the market. In 1980s, StarIAN completed millions of connections, but many distributors, including 3Com and DBC, have decided that 1Mbps is too slow-there has been a tradition of doubling the performance every two years in the computer industry, and some customers and distributors regard lMbFs Ethernet as a backward behavior. (1984, IBM announced the PC AT based on Intel80286 microprocessor. Two years later, in the year when the StarLAN 1BASE5 standard was approved, Intel introduced the 80386 microprocessor. This 32-bit CPU is many times more powerful than the previous generation 80286. Therefore, it is impossible for Xinglan to take off again with the support of the industry and the market. Finally, it entered a decline at 1987. At that time, SynOPtics introduced LATTISNET, and submitted the products that realized full-speed 10Mbps Ethernet performance on conventional telephone lines. Soon, LAT TISNET was standardized by IEEE according to twisted-pair Ethernet and named as10base-T. As a result, StarLAN and Galin have only a handful of dead days, but as pioneers of unshielded double-buckle and star Ethernet, their achievements are indelible.