4.1. Understanding the Internet

The Internet was originally created and implemented by DARPA (Defense Advanced Research Projects Agency; often referred to as just ARPA) in response to a U.S. Department of Defense (DoD) request. At the time, the DoD was concerned about its centralized communications network. Most communications were relayed through a central computing system or hub, and damage to that system could stop computer communication. To avoid this problem, the DoD gave ARPA the responsibility of devising a new system.

The first thing that ARPA had to do was to create communication protocols that would allow computers to talk to each other in a new and nonstandard, decentralized manner, and ARPA needed a small network on which it could test and develop the new protocols. It eventually interconnected four hosts, which formed the start of the ARPANET.

ARPANET (and the now the Internet) was defined by a series of standards that are currently being put forth by the Internet Architecture Board (IAB), which represents the governing body of the Internet. These Internet standards are defined by IAB but are discussed in RFC (Request for Comments) documents. The first RFC defined how the initial hosts on the ARPANET would send to and receive data from each other.

All RFCs — currently, more than 5,500 — are available from www.ietf.org. Technologies in RFCs sometimes make it into STD ...

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