The legend of network protocols (Part 2): TCP emerges

This section will formally enter the content of network protocols. However, with thousands of network protocols today, it is obviously impossible to trace their development in detail one by one, so this section takes the most widely used network protocol family TCP/IP as an example to give a glimpse into the history of network protocol technology.

The "Tower of Babel" in the Bible, Old Testament, Genesis, tells the story of how language diversity erodes human productivity. The Internet, from its birth to its subsequent continuous improvement, is actually a process of continuously eliminating the "Tower of Babel" problem.

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(Photo source: Baotu.com)

Network Protocol Original Version

The founders of the ARPANET faced a reality: different models of computers launched by different companies all had a unique set of control languages ​​and file organization methods, and these structural differences made it impossible for any two machines of different models to cooperate, which is now called interconnection. If you want to form a computer network, how can you connect different models of computers together? Initially, they solved this problem through a device developed by BBN and named Interface Signal Processor (IMP) - IMP was installed between the mainframe and the network to act as an intermediary, and its tasks were two: receiving information from the remote network and converting it into the format used by the local host; responsible for line scheduling. In this way, the incompatibility problem between computer systems was circumvented. On November 21, 1969, the ARPANET with 4 nodes was built and officially put into operation.

On November 21, 1969, the four-node ARPANET was completed and officially put into operation.

However, new problems followed. At that time, the ARPANET consisted of four large machines distributed in different areas on the west coast of the United States. The four mainframes were connected to each other through special IMPs and special communication lines. After the ARPANET was put into operation, it was found that when each IMP was connected, it was necessary to consider using a signal recognized by various types of computers to open the communication channel, and the channel had to be closed after the data passed. Otherwise, these IMPs would not know when to receive the signal and when to end it. This is what we call the concept of "communication protocol".

In December 1970, a protocol called "Network Control Protocol" (NCP) was used in the ARPANET. The protocol was completed by the Network Working Group (NWG) led by Steve Crocker. However, as the number of ARPANET users increased, NCP gradually exposed some defects, such as: it could not interconnect different operating systems, did not set a unique address for each computer in the network, lacked error correction functions, etc., resulting in the network being unable to stop running if an error occurred during data transmission. These problems greatly reduced the practicality of the network.

TCP/IP is born

In the 1970s, a large number of new networks began to emerge, including the Computer Science Research Network (CSNET), the Canadian Network (CDnet), the Because It's Time Network (BITNET), and the National Science Foundation Network (NSFnet). However, the ARPANET could not communicate with other computer networks, and subsequent experiments also verified that the existing ARPANET protocol was not suitable for running across multiple networks. This result triggered more research on the protocol, and eventually the "Transmission Control Protocol" (TCP) and "Internet Protocol" (IP), namely the TCP/IP model and protocol, were invented.

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Bob Kahn Vinton Cerf

The TCP/IP protocol was jointly developed by Bob Kahn, who worked at DARPA, and Vinton G. Cerf, an associate professor at Stanford University. In December 1974, their first detailed description of the TCP protocol was officially published. TCP/IP is one of the earliest network protocols and also the earliest Internet protocol.

In fact, the TCP/IP protocol solves another "Tower of Babel" problem. Previously, we encountered that different models of computers could not connect and cooperate due to different control languages ​​and file organization methods. Now we are facing the connection and communication barriers caused by different network structures and data transmission rules between different local area networks. If these local area networks are connected, data must be transmitted between the networks according to corresponding rules. The TCP/IP protocol solves this big problem very well. Its milestone significance lies in establishing an open interconnection model between the Internet and unifying the communication language between the Internet, thus laying the technical foundation for the birth of the real Internet.

The TCP/IP protocol first focuses on assigning a unique address to each computer, just like the house number of a house. Only with it can the courier deliver the package accurately - this is IP. TCP is responsible for supervising the transmission process, and sends a signal to request retransmission when a problem occurs, until all data is safely and correctly transmitted to the destination - this idea also directly led to the emergence of routers. Cisco should thank these two technology pioneers because it started with routers and then became synonymous with network infrastructure. Subsequent history has also proved that the invention and use of TCP/IP protocol and routers have greatly accelerated the popularization of the Internet.

The role of government: financier, nanny, salesman and dictator

At that time, in order to encourage the adoption of new protocols, the Defense Advanced Research Projects Agency of the United States Department of Defense awarded a contract to Stanford University, BBN and University College London to develop operating versions of the TCP/IP protocol on different hardware platforms, including IBM, DEC and HP systems. As a result, the Stanford University team led by Vinton Cerf took the lead and first developed a detailed definition of the TCP/IP protocol standard, and in about a year, implemented three independent TCPs that could interoperate (the first two versions of the TCP/IP protocol were named TCP, and from the third version onwards, TCP/IP was named).

On November 22, 1977, a van with a wireless transmitter was driving along a highway somewhere south of San Francisco, sending out a data packet signal that would travel between the wireless network and the ARPANET, and also on a satellite network that connected the ARPANET to Europe. The signal jumped from California to Boston, then to Norway and the UK, then back to a small town in West Virginia, and finally back to California. This experiment enabled the TCP/IP protocol to complete the signal transmission between three independent computer networks for the first time, traveling 94,000 miles without losing a single bit! The technical capabilities of the TCP/IP protocol were proven. "That was real Internet activity," Cerf later recalled.

In order to promote the TCP/IP protocol, the Defense Advanced Research Projects Agency of the United States Department of Defense sold the TCP/IP method at a low price and funded BBN and the University of California, Berkeley to promote the inclusion of TCP/IP developed by BBN into the BSD UNIX operating system. BSD (Berkeley Software Distribution) is a derivative system of Unix. BSD UNIX was popular in most universities at the time. It was developed and released by the University of California, Berkeley. The purpose of the agency was simple, which was to make TCP/IP enter the mainstream.

Bill Joy (formerly Sun's chief scientist) led the development of the earliest version of BSD when he was a student at Berkeley. In early 1980, when the U.S. Department of Defense's Advanced Research Projects Agency put forward the above requirements to BBN and Berkeley, Bill Joy, who was still a graduate student, flatly refused to add BBN TCP/IP to BSD because he thought BBN's TCP/IP was not well written. As a result, Bill Joy started from scratch and soon wrote a high-performance Berkeley version of TCP/IP, which enabled TCP/IP to be more efficiently integrated into the Unix system and kernel. The two sides met at a later meeting, and the BBN people asked: How did you write it? Bill Joy replied: It's simple, you just read the protocol and then program it. It is indeed embarrassing that BBN, which once built the ARPANET, lost to a graduate student. However, it turns out that the combination of TCP/IP and the popular operating system Unix is ​​a major source of its success, which is also another brilliant move made by the U.S. Department of Defense.

In 1983, Berkeley launched the first BDS UNIX with TCP/IP built in. The project team rewrote TCP/IP using a new programming interface, the famous socket released with Berkeley UNIX 4.2BSD. They also wrote many applications, tools, and management programs to show how easy it is to use the network through sockets.

By chance, at that time, many universities had just gotten their second or third DEC VAX computers and the LANs that connected them, but they had no networking software. When 4.2BSD came out, the entire package of TCP/IP, socket programming interfaces, and many network tools was immediately adopted. Moreover, it was very easy to connect a LAN to the ARPANET via TCP/IP, and many LANs did so. As a result, TCP/IP gradually became the mainstream network protocol.

Next, the moment of unification finally arrived! According to the "order" from the Office of the Secretary of Defense of the United States, all computers connected to the remote network on January 1, 1983 must use TCP/IP, and NCP will be discontinued. Just like the leader shouting the command "march in step", on January 1, 1983, all hosts must switch at the same time, otherwise they will have to communicate through temporary mechanisms. Of course, this arrangement has been carefully planned a few years ago, so the conversion process was very smooth. So far, this Internet with ARPANET as the backbone network has been called the Internet, and the TCP/IP protocol has officially started its legendary journey.

In 1986, another important promoter of the Internet appeared. It was still a US government agency - the National Science Foundation (NSF). That year, NSF established six supercomputer centers. In order to enable scientists and engineers across the country to share these supercomputer facilities, NSF established its own computer network NSFNET based on the TCP/IP protocol suite. Needless to say, in June 1990, NSFNET completely replaced ARPANET and became the backbone of the Internet.

In the 1990s, the US government realized that it was difficult to meet the development needs of Internet applications with government funding alone, so it began to encourage the commercial sector to intervene. In 1992, IBM, MCI, and MERIT jointly established an Advanced Network Services Company (ANS) to build a T3 (44.746M) backbone network ANSNET covering the entire United States, which became another Internet backbone network after NSFNET. Subsequently, the Advanced Research Projects Agency of the US Department of Defense and the National Science Foundation of the United States withdrew their funding for ARPANET and NSFNET, and the Internet began to enter commercial use.

This is like a relay race of unprecedented scale. Looking back at the first 20 years of the development of the Internet, the US government not only chose the right track, but also bet on the right players. All the decisions and changes during this period have substantially promoted the development of the Internet. For the early Internet, the US government agencies undoubtedly played the role of incubators, with substantial financial support, precise promotion and popularization strategies, mandatory "command" behavior, timely introduction of commercial resources, and finally timely retirement. Careful during the growth period, decisively let go after growing up, and there is a sense of progress and retreat. During this period, the US government has played many different roles. It is a nanny, a financier, a salesman, a partner, and even a "dictator". It can be said to be a combination of hardness and softness, and a multi-pronged approach, but with only one purpose - to guide the Internet in the right direction. We can even imagine what would happen to the Internet if the government role was absent?

References:

• Uncovering the family history of data center network protocols
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• Baidu Encyclopedia TCP/IP Protocol
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• Looking back at the predecessor of the Internet - "ARPANET"
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• Technology History: TCP/IP Protocol That Changed the World
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