Proving the Ideas...
DARPA let three contracts to Stanford (Cerf), BBN (Ray Tomlinson) and UCL (Peter
Kirstein) to implement TCP/IP (it was simply called TCP in the Cerf/Kahn paper but
contained both components). The Stanford team, led by Cerf, produced the detailed
specification and within about a year there were three independent implementations of TCP
that could interoperate.
This was the beginning of long term experimentation and development to evolve and mature
the Internet concepts and technology. Beginning with the first three networks (ARPANET,
Packet Radio, and Packet Satellite) and their initial research communities, the experimental
environment has grown to incorporate essentially every form of network and a very
broad-based research and development community. [REK78] With each expansion has
come new challenges.
The early implementations of TCP were done for large time sharing systems such as Tenex
and TOPS 20. When desktop computers first appeared, it was thought by some that TCP
was too big and complex to run on a personal computer. David Clark and his research
group at MIT set out to show that a compact and simple implementation of TCP was
possible. They produced an implementation, first for the Xerox Alto (the early personal
workstation developed at Xerox PARC) and then for the IBM PC. That implementation was
fully interoperable with other TCPs, but was tailored to the application suite and
performance objectives of the personal computer, and showed that workstations, as well as
large time-sharing systems, could be a part of the Internet. In 1976, Kleinrock published the
first book on the ARPANET. It included an emphasis on the complexity of protocols and
the pitfalls they often introduce. This book was influential in spreading the lore of packet
switching networks to a very wide community.
 Widespread development of LANS, PCs and workstations in the 1980s allowed the nascent
Internet to flourish. Ethernet technology, developed by Bob Metcalfe at Xerox PARC in
1973, is now probably the dominant network technology in the Internet and PCs and
workstations the dominant computers. This change from having a few networks with a
modest number of time-shared hosts (the original ARPANET model) to having many
networks has resulted in a number of new concepts and changes to the underlying
technology. First, it resulted in the definition of three network classes (A, B, and C) to
accommodate the range of networks. Class A represented large national scale networks
(small number of networks with large numbers of hosts); Class B represented regional scale
networks; and Class C represented local area networks (large number of networks with
relatively few hosts).
A major shift occurred as a result of the increase in scale of the Internet and its associated
management issues. To make it easy for people to use the network, hosts were assigned
names, so that it was not necessary to remember the numeric addresses. Originally, there
were a fairly limited number of hosts, so it was feasible to maintain a single table of all the
hosts and their associated names and addresses. The shift to having a large number of
independently managed networks (e.g., LANs) meant that having a single table of hosts was
no longer feasible, and the Domain Name System (DNS) was invented by Paul Mockapetris
of USC/ISI. The DNS permitted a scalable distributed mechanism for resolving hierarchical
host names (e.g. www.acm.org) into an Internet address.
The increase in the size of the Internet also challenged the capabilities of the routers.
Originally, there was a single distributed algorithm for routing that was implemented
uniformly by all the routers in the Internet. As the number of networks in the Internet
exploded, this initial design could not expand as necessary, so it was replaced by a
hierarchical model of routing, with an Interior Gateway Protocol (IGP) used inside each
region of the Internet, and an Exterior Gateway Protocol (EGP) used to tie the regions
together. This design permitted different regions to use a different IGP, so that different
requirements for cost, rapid reconfiguration, robustness and scale could be accommodated.
Not only the routing algorithm, but the size of the addressing tables, stressed the capacity of
the routers. New approaches for address aggregation, in particular classless inter-domain
routing (CIDR), have recently been introduced to control the size of router tables.
As the Internet evolved, one of the major challenges was how to propagate the changes to
the software, particularly the host software. DARPA supported UC Berkeley to investigate
modifications to the Unix operating system, including incorporating TCP/IP developed at
BBN. Although Berkeley later rewrote the BBN code to more efficiently fit into the Unix
system and kernel, the incorporation of TCP/IP into the Unix BSD system releases proved
to be a critical element in dispersion of the protocols to the research community. Much of
the CS research community began to use Unix BSD for their day-to-day computing
environment. Looking back, the strategy of incorporating Internet protocols into a
supported operating system for the research community was one of the key elements in the
successful widespread adoption of the Internet.
One of the more interesting challenges was the transition of the ARPANET host protocol
from NCP to TCP/IP as of January 1, 1983. This was a "flag-day" style transition, requiring
all hosts to convert simultaneously or be left having to communicate via rather ad-hoc
mechanisms. This transition was carefully planned within the community over several years
before it actually took place and went surprisingly smoothly (but resulted in a distribution of
buttons saying "I survived the TCP/IP transition").
TCP/IP was adopted as a defense standard three years earlier in 1980. This enabled defense
to begin sharing in the DARPA Internet technology base and led directly to the eventual
partitioning of the military and non- military communities. By 1983, ARPANET was being
used by a significant number of defense R&D and operational organizations. The transition
of ARPANET from NCP to TCP/IP permitted it to be split into a MILNET supporting
operational requirements and an ARPANET supporting research needs.
Thus, by 1985, Internet was already well established as a technology supporting a broad
community of researchers and developers, and was beginning to be used by other
communities for daily computer communications. Electronic mail was being used broadly
across several communities, often with different systems, but interconnection between
different mail systems was demonstrating the utility of broad based electronic
communications between people.
History of the Future...On October 24, 1995, the FNC unanimously passed a resolution defining the term Internet.
This definition was developed in consultation with members of the internet and intellectual
property rights communities. RESOLUTION: The Federal Networking Council (FNC)
agrees that the following language reflects our definition of the term "Internet". "Internet"
refers to the global information system that -- (i) is logically linked together by a globally
unique address space based on the Internet Protocol (IP) or its subsequent
extensions/follow-ons; (ii) is able to support communications using the Transmission
Control Protocol/Internet Protocol (TCP/IP) suite or its subsequent extensions/follow-ons,
and/or other IP-compatible protocols; and (iii) provides, uses or makes accessible, either
publicly or privately, high level services layered on the communications and related
infrastructure described herein.
The Internet has changed much in the two decades since it came into existence. It was
conceived in the era of time-sharing, but has survived into the era of personal computers,
client-server and peer-to-peer computing, and the network computer. It was designed before
LANs existed, but has accommodated that new network technology, as well as the more
recent ATM and frame switched services. It was envisioned as supporting a range of
functions from file sharing and remote login to resource sharing and collaboration, and has
spawned electronic mail and more recently the World Wide Web. But most important, it
started as the creation of a small band of dedicated researchers, and has grown to be a
commercial success with billions of dollars of annual investment.
One should not conclude that the Internet has now finished changing. The Internet, although
a network in name and geography, is a creature of the computer, not the traditional network
of the telephone or television industry. It will, indeed it must, continue to change and evolve
at the speed of the computer industry if it is to remain relevant. It is now changing to
provide such new services as real time transport, in order to support, for example, audio
and video streams. The availability of pervasive networking (i.e., the Internet) along with
powerful affordable computing and communications in portable form (i.e., laptop
computers, two-way pagers, PDAs, cellular phones), is making possible a new paradigm of
nomadic computing and communications.
This evolution will bring us new applications - Internet telephone and, slightly further out,
Internet television. It is evolving to permit more sophisticated forms of pricing and cost
recovery, a perhaps painful requirement in this commercial world. It is changing to
accommodate yet another generation of underlying network technologies with different
characteristics and requirements, from broadband residential access to satellites. New
modes of access and new forms of service will spawn new applications, which in turn will
drive further evolution of the net itself.
 The most pressing question for the future of the Internet is not how the technology will
change, but how the process of change and evolution itself will be managed. As this paper
describes, the architecture of the Internet has always been driven by a core group of
designers, but the form of that group has changed as the number of interested parties has
grown. With the success of the Internet has come a proliferation of stakeholders -
stakeholders now with an economic as well as an intellectual investment in the network. We
now see, in the debates over control of the domain name space and the form of the next
generation IP addresses, a struggle to find the next social structure that will guide the
Internet in the future. The form of that structure will be harder to find, given the large
number of concerned stake-holders. At the same time, the industry struggles to find the
economic rationale for the large investment needed for the future growth, for example to
upgrade residential access to a more suitable technology. If the Internet stumbles, it will not
be because we lack for technology, vision, or motivation. It will be because we cannot set a
direction and march collectively into the future.
References...
P. Baran, "On Distributed Communications Networks", IEEE Trans. Comm. Systems,
March 1964.
V. G. Cerf and R. E. Kahn, "A protocol for packet network interconnection", IEEE Trans.
Comm. Tech., vol. COM-22, V 5, pp. 627-641, May 1974.
S. Crocker, RFC001 Host software, Apr-07-1969.
R. Kahn, Communications Principles for Operating Systems. Internal BBN memorandum,
Jan. 1972.
Proceedings of the IEEE, Special Issue on Packet Communication Networks, Volume 66,
No. 11, November, 1978. (Guest editor: Robert Kahn, associate guest editors: Keith
Uncapher and Harry van Trees)
L. Kleinrock, "Information Flow in Large Communication Nets", RLE Quarterly Progress
Report, July 1961.
L. Kleinrock, Communication Nets: Stochastic Message Flow and Delay, Mcgraw-Hill
(New York), 1964.
L. Kleinrock, Queueing Systems: Vol II, Computer Applications, John Wiley and Sons
(New York), 1976.
J.C.R. Licklider & W. Clark, "On-Line Man .
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