During the early 1970s, as data networks became more common, the number of different ways in which to build them increased exponentially. To a number of people, the concept of internetworking (IBM TCP/IP Tutorial and Technical Overview, Martin W. Murhammer, Orcun Atakan, Stefan Bretz, Larry R. Pugh, Kazunari Suzuki, David H. Wood, October 1998, pp3), or connecting multiple networks to each other, became extremely important as connecting together disparate and contrasting networks built around different sets of technology started causing pain.
A protocol, within the context of IT and Computer Science, is generally speaking a common format in which computers interchange data for a certain purpose. In networking, a protocol is best compared to a language—the networking situation in the 1970s was one in which there were many different languages and very few interpreters readily available to translate for people.
The resulting research, and most importantly that carried out and funded by the American Department of Defense's Defense Advanced Research Projects Agency (http://www.darpa.mil), gave birth not only to a range of network protocols designed for interoperability (that is to say, in order to allow easy, platform-neutral communications between a range of devices), but a network, ARPANet, set up for this express purpose. The best comparison for this within language is the development of the language Esperanto—although the proliferation of this international language has been fairly minimal, computers have the advantage of not taking years to learn a particular protocol!
This ARPANet was first experimented with using TCP/IP in 1976, and in January of 1983, its use was mandated for all computers participating in the network. By the late 1970s, many organizations besides the military were granted access to the ARPANet as well, such as NASA, the National Science Foundation (NSF), and eventually universities and other academic entities.
After the military broke away from the ARPANet to form its own, separate network for military use (MILNET), the network became the responsibility of the NSF, which came to create its own high-speed backbone, called NSFNet, for the facilitation of internetworking.
When the Acceptable Usage Policy for NSFNet began to permit non-academic traffic, the NSFNet began, in combination with other (commercial and private) networks (such as those operated via CIX), to form the entity we now know as the Internet. By the NSF's exit from the management of the Internet and the shutdown of the NSFNet in April 1995, the Internet was populated by an ever-growing population of commercial, academic, and private users.
The standards upon which the Internet is based have become the staple of modern networking, and nowadays when anyone says 'networking' they tend to be referring to something built with (and around) TCP/IP, the set of layered protocols originally developed for use on ARPANet, along with other standards upon which TCP/IP is implemented, such as 802.3 or Ethernet, which defines how one of the most popular standards over which TCP/IP runs across in network segments works.
These layered protocols, apart from being interesting to us for historical and anecdotal reasons, have several important implications for us. The most notable implication is that any device built around them is entirely interoperable with any other device. The consequence of this, then, is that we can buy networking components built by any vendor—our Dell laptop running Microsoft Windows can freely communicate, via TCP/IP, over an Ethernet network using a Linksys switch, plugged into a Cisco Router, and view a web page hosted on an IBM server running AIX, also talking TCP/IP.
More standardized protocols, running on top of TCP/IP, such as HTTP, actually carry the information itself, and thanks to the layering of these protocols, we can have a vast and disparate set of networks connected that appear transparent to devices such as web browsers and web servers, that speak protocols such as HTTP. Between our Dell laptop and our IBM server, we may have a dial-up connection, a frame relay network segment, a portion of the internet backbone, and a wireless network link—none of which concern TCP/IP or HTTP, which sit 'above' these layers of the network, and travel freely above them. If only a coach load of children on a school tour could use air travel, ferries, cycle paths, and cable cars, all without stepping from their vehicle or being aware of the changing transport medium beneath them! Layered communication of the type that TCP/IP is capable of in this sense is incredibly powerful and really allows our communications infrastructure to scale.