The Domain Name System
the authors created an architecture for interconnecting independent networks that could then be federated into a seamless whole without changing any of the underlying networks. This was the genesis of the Internet as we know it today.
In order to work properly, the architecture required a global addressing mechanism (or Internet address) to enable computers on any network to reference and communicate with computers on any other network in the federation. Internet addresses fill essentially the same role as telephone numbers do in telephone networks. The design of the Internet assumed first that the individual networks could not be changed to accommodate new architectural requirements; but this was largely a pragmatic assumption to facilitate progress. The networks also had varying degrees of reliability and speed. Host computers would have to be able to put disordered packets back into the correct order and discard duplicate packets that had been generated along the way. This was a major change from the virtual circuit-like service provided by ARPANET and by then contemporary commercial data networking services such as Tymnet and Telenet. In these networks, the underlying network took responsibility for keeping all information in order and for re-sending any data that might have been lost. The Internet design made the computers responsible for tending to these network problems.
A key architectural construct was the introduction of gateways (now called routers) between the networks to handle the disparities such as different data rates, packet sizes, error conditions, and interface specifications. The gateways would also check the destination Internet addresses of each packet to determine the gateway to which it should be forwarded. These functions would be combined with certain end-end functions to produce the reliable communication from source to destination. A draft paper by the authors describing this approach was given at a meeting of the International Network Working Group in 1973 in Sussex, England and the final paper was subsequently published by the Institute for Electrical and Electronics Engineers, the leading professional society for the electrical engineering profession, in its Transactions on Communications in May, 1974 . The paper described the TCP/IP protocol.
DARPA contracted with Cerf's group at Stanford to carry out the initial detailed design of the TCP software and, shortly thereafter, with BBN and University College London to build independent implementations of the TCP protocol (as it was then called – it was later split into TCP and IP) for different machines. BBN also had a contract to build a prototype version of the gateway. These three sites collaborated in the development and testing of the initial protocols on different machines. Cerf, then a professor at Stanford, provided the day-to-day leadership in the initial TCP software design and testing. BBN deployed the gateways between the ARPANET and the PRNET and also with SATNET. During this period, under Kahn's overall leadership at DARPA, the initial feasibility of the Internet Architecture was demonstrated.
The TCP/IP protocol suite was developed and refined over a period of four more years and, in 1980, it was adopted as a standard by the U.S. Department of Defense. On January 1, 1983 the ARPANET converted to TCP/IP as its standard host protocol. Gateways (or routers) were used to pass packets to and from host computers on “local area networks.” Refinement and extension of these protocols and many others associated with them continues to this day by way of the Internet Engineering Task Force .
GOVERNMENT’S HISTORICAL ROLE
Other political and social dimensions that enabled the Internet to come into existence and flourish are just as important as the technology upon which it is based. The federal government played a large role in creating the Internet, as did the private sector interests that made it available to the general public. The development of the personal computer industry and significant changes in the telecommunications industry also contributed to the Internet’s growth in the 1980s. In particular, the development of workstations, the Unix operating system, and local area networking (especially the Ethernet) contributed to the spread of the Internet within the research community from which the Internet industry eventually emerged.
The National Science Foundation and others
In the late 1970s, the National Science Foundation (NSF) became interested in the impact of the ARPANET on computer science and engineering. NSF funded the Computer Science Network (CSNET), which was a logical design for interconnecting universities that were already on the ARPANET and those that were not. Telenet was used for sites not connected directly to the ARPANET and a gateway was provided to link the two. Independent of NSF, another initiative called BITNET ("Because it's there" Net) provided campus computers with email connections to the growing ARPANET. Finally, AT&T Bell Laboratories development of the Unix operating system led to the creation of a grass-roots network called USENET , which rapidly became home to thousands of “newsgroups” where Internet users discussed everything from aerobics to politics and zoology.
In the mid 1980s, NSF decided to build a network called NSFNET to provide better computer connections for the science and education communities. The NSFNET made possible the involvement of a large segment of the education and research community in the use of high speed networks. A consortium consisting of MERIT (a University of Michigan non-profit network services organization), IBM and MCI Communications won a 1987 competition for the contract to handle the network’s construction. Within two years, the newly expanded NSFNET had become the primary backbone component of the Internet, augmenting the ARPANET until it was decommissioned in 1990.At about the same time, other parts of the U.S. government had moved ahead to build and deploy networks of their own, including NASA and the Department of Energy. While these groups originally adopted independent approaches for their networks, they eventually decided to support the use of TCP/IP.
The developers of the NSFNET, led by Steve Wolff who had the direct responsibility for the NSFNET program, also decided to create intermediate level networks to serve research and education institutions and, more importantly, to allow networks that were not commissioned by the U.S. government to connect to the NSFNET. This strategy reduced the overall load on the backbone network operators and spawned a new industry: Internet Service Provision. Nearly a dozen intermediate level networks were created, most with NSF support, some, such as UUNET, with Defense support, and some without any government support. The NSF contribution to the evolution of the Internet was essential in two respects. It opened the Internet to many new users and, drawing on the properties of TCP/IP, structured it so as to allow many more network service providers to participate.
For a long time, the federal government did not allow organizations to connect to the Internet to carry out commercial activities. By 1988, it was becoming apparent, however, that the Internet's growth and use in the business sector might be seriously inhibited by this restriction. That year, CNRI requested permission from the Federal Networking Council to interconnect the commercial MCI Mail electronic mail system to the Internet as part of a general electronic mail interconnection experiment. Permission was given and the interconnection was completed by CNRI, under Cerf’s direction, in the summer of 1989. Shortly thereafter, two of the then non-profit Internet Service Providers (UUNET and NYSERNET) produced new for-profit companies (UUNET and PSINET respectively). In 1991, they were interconnected with each other and CERFNET . Commercial pressure to alleviate restrictions on interconnections with the NSFNET began to mount.
In response, Congress passed legislation allowing NSF to open the NSFNET to commercial usage. Shortly thereafter, NSF determined that its support for NSFNET might not be required in the longer term and, in April 1995, NSF ceased its support for the NSFNET. By that time, many commercial networks were in operation and provided alternatives to NSFNET for national level network services. Today, approximately 10,000 Internet Service Providers (ISPs) are in operation. Roughly half the world's ISPs currently are based in North America and the rest are distributed throughout the world.
A DEFINITION FOR THE INTERNET
The authors feel strongly that efforts should be made at top policy levels to define the Internet. It is tempting to view it merely as a collection of networks and computers. However, as indicated earlier, the authors designed the Internet as an architecture that provided for both communications capabilities and information services. Governments are passing legislation pertaining to the Internet without ever specifying to what the law applies and to what it does not apply. In U.S. telecommunications law, distinctions are made between cable, satellite broadcast and common carrier services. These and many other distinctions all blur in the backdrop of the Internet. Should broadcast stations be viewed as Internet Service Providers when their programming is made available in the Internet environment? Is use of cellular telephones considered part of the Internet and if so under what conditions? This area is badly in need of clarification.
The authors believe the best definition currently in existence is that approved by the Federal Networking Council in 1995, and which is reproduced in the footnote below for ready reference. Of particular note is that it defines the Internet as a global information system, and included in the definition, is not only the underlying communications technology, but also higher-level protocols and end-user applications, the associated data structures and the means by which the information may be processed, manifested, or otherwise used. In many ways, this definition supports the characterization of the Internet as an “information superhighway.” Like the federal highway system, whose underpinnings include not only concrete lanes and on/off ramps, but also a supporting infrastructure both physical and informational, including signs, maps, regulations, and such related services and products as filling stations and gasoline, the Internet has its own layers of ingress and egress, and its own multi-tiered levels of service.
The FNC definition makes it clear that the Internet is a dynamic organism that can be looked at in myriad ways. It is a framework for numerous services and a medium for creativity and innovation. Most importantly, it can be expected to evolve.
No comments:
Post a Comment