A Brief History
of the Internet
Barry
M. Leiner, Vinton G. Cerf, David
D. Clark,
Robert E. Kahn, Leonard Kleinrock,
Daniel C. Lynch,
Jon Postel, Larry G. Roberts,
Stephen Wolff
Introduction
The Internet has
revolutionized the computer and communications world like nothing before.
The invention of the telegraph, telephone, radio, and computer set the
stage for this unprecedented integration of capabilities. The Internet
is at once a world-wide broadcasting capability, a mechanism for information
dissemination, and a medium for collaboration and interaction between
individuals and their computers without regard for geographic location.
The Internet represents
one of the most successful examples of the benefits of sustained investment
and commitment to research and development of information infrastructure.
Beginning with the early research in packet switching, the government,
industry and academia have been partners in evolving and deploying this
exciting new technology. Today, terms like "bleiner@computer.org"
and "http://www.acm.org" trip lightly off the tongue of the
random person on the street. 1
This is intended
to be a brief, necessarily cursory and incomplete history. Much material
currently exists about the Internet, covering history, technology, and
usage. A trip to almost any bookstore will find shelves of material
written about the Internet. 2
In this paper, 3
several of us involved in the development and evolution of the Internet
share our views of its origins and history. This history revolves around
four distinct aspects. There is the technological evolution that began
with early research on packet switching and the ARPANET (and related
technologies), and where current research continues to expand the horizons
of the infrastructure along several dimensions, such as scale, performance,
and higher level functionality. There is the operations and management
aspect of a global and complex operational infrastructure. There is
the social aspect, which resulted in a broad community of Internauts
working together to create and evolve the technology. And there is the
commercialization aspect, resulting in an extremely effective transition
of research results into a broadly deployed and available information
infrastructure.
The Internet today
is a widespread information infrastructure, the initial prototype of
what is often called the National (or Global or Galactic) Information
Infrastructure. Its history is complex and involves many aspects - technological,
organizational, and community. And its influence reaches not only to
the technical fields of computer communications but throughout society
as we move toward increasing use of online tools to accomplish electronic
commerce, information acquisition, and community operations.
Origins of the
Internet
The first recorded
description of the social interactions that could be enabled through
networking was a series of memos written by J.C.R.
Licklider of MIT in August 1962 discussing his "Galactic Network"
concept. He envisioned a globally interconnected set of computers through
which everyone could quickly access data and programs from any site.
In spirit, the concept was very much like the Internet of today. Licklider
was the first head of the computer research program at DARPA, 4
starting in October 1962. While at DARPA he convinced his successors
at DARPA, Ivan Sutherland, Bob Taylor, and MIT researcher Lawrence G.
Roberts, of the importance of this networking concept.
Leonard Kleinrock
at MIT published the first paper on packet switching
theory in July 1961 and the first book on the subject
in 1964. Kleinrock convinced Roberts of the theoretical feasibility
of communications using packets rather than circuits, which was a major
step along the path towards computer networking. The other key step
was to make the computers talk together. To explore this, in 1965 working
with Thomas Merrill, Roberts connected the TX-2 computer in Mass. to
the Q-32 in California with a low speed dial-up telephone line creating
the first (however small) wide-area computer network
ever built. The result of this experiment was the realization that
the time-shared computers could work well together, running programs
and retrieving data as necessary on the remote machine, but that the
circuit switched telephone system was totally inadequate for the job.
Kleinrock's conviction of the need for packet switching was confirmed.
In late 1966 Roberts
went to DARPA to develop the computer network concept and quickly put
together his plan for the "ARPANET",
publishing it in 1967. At the conference where he presented the paper,
there was also a paper on a packet network concept from the UK by Donald
Davies and Roger Scantlebury of NPL. Scantlebury told Roberts about
the NPL work as well as that of Paul Baran and others at RAND. The RAND
group had written a paper on packet switching networks
for secure voice in the military in 1964. It happened that the work
at MIT (1961-1967), at RAND (1962-1965), and at NPL (1964-1967) had
all proceeded in parallel without any of the researchers knowing about
the other work. The word "packet" was adopted from the work
at NPL and the proposed line speed to be used in the ARPANET design
was upgraded from 2.4 kbps to 50 kbps. 5
In August 1968,
after Roberts and the DARPA funded community had refined the overall
structure and specifications for the ARPANET, an RFQ was released by
DARPA for the development of one of the key components, the packet switches
called Interface Message Processors (IMP's). The RFQ was won in December
1968 by a group headed by Frank Heart at Bolt Beranek and Newman (BBN).
As the BBN team worked on the IMP's with Bob Kahn playing a major role
in the overall ARPANET architectural design, the network topology and
economics were designed and optimized by Roberts working with Howard
Frank and his team at Network Analysis Corporation, and the network
measurement system was prepared by Kleinrock's team at UCLA. 6
Due to Kleinrock's
early development of packet switching theory and his focus on analysis,
design and measurement, his Network Measurement Center at UCLA was selected
to be the first node on the ARPANET. All this came together in September
1969 when BBN installed the first IMP at UCLA and the first host computer
was connected. Doug Engelbart's project on "Augmentation of Human
Intellect" (which included NLS, an early hypertext system) at Stanford
Research Institute (SRI) provided a second node. SRI supported the Network
Information Center, led by Elizabeth (Jake) Feinler and including functions
such as maintaining tables of host name to address mapping as well as
a directory of the RFC's. One month later, when SRI was connected to
the ARPANET, the first host-to-host message was sent from Kleinrock's
laboratory to SRI. Two more nodes were added at UC Santa Barbara and
University of Utah. These last two nodes incorporated application visualization
projects, with Glen Culler and Burton Fried at UCSB investigating methods
for display of mathematical functions using storage displays to deal
with the problem of refresh over the net, and Robert Taylor and Ivan
Sutherland at Utah investigating methods of 3-D representations over
the net. Thus, by the end of 1969, four host computers were connected
together into the initial ARPANET, and the budding Internet was off
the ground. Even at this early stage, it should be noted that the networking
research incorporated both work on the underlying network and work on
how to utilize the network. This tradition continues to this day.
Computers were added
quickly to the ARPANET during the following years, and work proceeded
on completing a functionally complete Host-to-Host protocol and other
network software. In December 1970 the Network Working Group (NWG) working
under S. Crocker finished the initial ARPANET Host-to-Host protocol,
called the Network Control Protocol (NCP). As the ARPANET sites completed
implementing NCP during the period 1971-1972, the network users finally
could begin to develop applications.
In October 1972
Kahn organized a large, very successful demonstration of the ARPANET
at the International Computer Communication Conference (ICCC). This
was the first public demonstration of this new network technology to
the public. It was also in 1972 that the initial "hot" application,
electronic mail, was introduced. In March Ray Tomlinson at BBN wrote
the basic email message send and read software, motivated by the need
of the ARPANET developers for an easy coordination mechanism. In July,
Roberts expanded its utility by writing the first email utility program
to list, selectively read, file, forward, and respond to messages. From
there email took off as the largest network application for over a decade.
This was a harbinger of the kind of activity we see on the World Wide
Web today, namely, the enormous growth of all kinds of "people-to-people"
traffic.
The Initial Internetting
Concepts
The original ARPANET
grew into the Internet. Internet was based on the idea that there would
be multiple independent networks of rather arbitrary design, beginning
with the ARPANET as the pioneering packet switching network, but soon
to include packet satellite networks, ground-based packet radio networks
and other networks. The Internet as we now know it embodies a key underlying
technical idea, namely that of open architecture networking. In this
approach, the choice of any individual network technology was not dictated
by a particular network architecture but rather could be selected freely
by a provider and made to interwork with the other networks through
a meta-level "Internetworking Architecture". Up until that
time there was only one general method for federating networks. This
was the traditional circuit switching method where networks would interconnect
at the circuit level, passing individual bits on a synchronous basis
along a portion of an end-to-end circuit between a pair of end locations.
Recall that Kleinrock had shown in 1961 that packet switching was a
more efficient switching method. Along with packet switching, special
purpose interconnection arrangements between networks were another possibility.
While there were other limited ways to interconnect different networks,
they required that one be used as a component of the other, rather than
acting as a peer of the other in offering end-to-end service.
In an open-architecture
network, the individual networks may be separately designed and developed
and each may have its own unique interface which it may offer to users
and/or other providers. including other Internet providers. Each network
can be designed in accordance with the specific environment and user
requirements of that network. There are generally no constraints on
the types of network that can be included or on their geographic scope,
although certain pragmatic considerations will dictate what makes sense
to offer.
The idea of open-architecture
networking was first introduced by Kahn shortly after having arrived
at DARPA in 1972. This work was originally part of the packet radio
program, but subsequently became a separate program in its own right.
At the time, the program was called "Internetting". Key to
making the packet radio system work was a reliable end-end protocol
that could maintain effective communication in the face of jamming and
other radio interference, or withstand intermittent blackout such as
caused by being in a tunnel or blocked by the local terrain. Kahn first
contemplated developing a protocol local only to the packet radio network,
since that would avoid having to deal with the multitude of different
operating systems, and continuing to use NCP.
However, NCP did
not have the ability to address networks (and machines) further downstream
than a destination IMP on the ARPANET and thus some change to NCP would
also be required. (The assumption was that the ARPANET was not changeable
in this regard). NCP relied on ARPANET to provide end-to-end reliability.
If any packets were lost, the protocol (and presumably any applications
it supported) would come to a grinding halt. In this model NCP had no
end-end host error control, since the ARPANET was to be the only network
in existence and it would be so reliable that no error control would
be required on the part of the hosts.
Thus, Kahn decided
to develop a new version of the protocol which could meet the needs
of an open-architecture network environment. This protocol would eventually
be called the Transmission Control Protocol/Internet Protocol (TCP/IP).
While NCP tended to act like a device driver, the new protocol would
be more like a communications protocol.
Four ground rules
were critical to Kahn's early thinking:
- Each distinct
network would have to stand on its own and no internal changes could
be required to any such network to connect it to the Internet.
- Communications
would be on a best effort basis. If a packet didn't make it to the
final destination, it would shortly be retransmitted from the source.
- Black boxes would
be used to connect the networks; these would later be called gateways
and routers. There would be no information retained by the gateways
about the individual flows of packets passing through them, thereby
keeping them simple and avoiding complicated adaptation and recovery
from various failure modes.
- There would be
no global control at the operations level.
Other key issues
that needed to be addressed were:
- Algorithms to
prevent lost packets from permanently disabling communications and
enabling them to be successfully retransmitted from the source.
- Providing for
host to host "pipelining" so that multiple packets could
be enroute from source to destination at the discretion of the participating
hosts, if the intermediate networks allowed it.
- Gateway functions
to allow it to forward packets appropriately. This included interpreting
IP headers for routing, handling interfaces, breaking packets into
smaller pieces if necessary, etc.
- The need for
end-end checksums, reassembly of packets from fragments and detection
of duplicates, if any.
- The need for
global addressing
- Techniques for
host to host flow control.
- Interfacing with
the various operating systems
- There were also
other concerns, such as implementation efficiency, internetwork performance,
but these were secondary considerations at first.
Kahn began work
on a communications-oriented set of operating system principles while
at BBN and documented some of his early thoughts in an internal BBN
memorandum entitled "Communications Principles
for Operating Systems". At this point he realized it would
be necessary to learn the implementation details of each operating system
to have a chance to embed any new protocols in an efficient way. Thus,
in the spring of 1973, after starting the internetting effort, he asked
Vint Cerf (then at Stanford) to work with him on the detailed design
of the protocol. Cerf had been intimately involved in the original NCP
design and development and already had the knowledge about interfacing
to existing operating systems. So armed with Kahn's architectural approach
to the communications side and with Cerf's NCP experience, they teamed
up to spell out the details of what became TCP/IP.
The give and take
was highly productive and the first written version 7
of the resulting approach was distributed at a special meeting of the
International Network Working Group (INWG) which had been set up at
a conference at Sussex University in September 1973. Cerf had been invited
to chair this group and used the occasion to hold a meeting of INWG
members who were heavily represented at the Sussex Conference.
Some basic approaches
emerged from this collaboration between Kahn and Cerf:
- Communication
between two processes would logically consist of a very long stream
of bytes (they called them octets). The position of any octet in the
stream would be used to identify it.
- Flow control
would be done by using sliding windows and acknowledgments (acks).
The destination could select when to acknowledge and each ack returned
would be cumulative for all packets received to that point.
- It was left open
as to exactly how the source and destination would agree on the parameters
of the windowing to be used. Defaults were used initially.
- Although Ethernet
was under development at Xerox PARC at that time, the proliferation
of LANs were not envisioned at the time, much less PCs and workstations.
The original model was national level networks like ARPANET of which
only a relatively small number were expected to exist. Thus a 32 bit
IP address was used of which the first 8 bits signified the network
and the remaining 24 bits designated the host on that network. This
assumption, that 256 networks would be sufficient for the foreseeable
future, was clearly in need of reconsideration when LANs began to
appear in the late 1970s.
The original Cerf/Kahn
paper on the Internet described one protocol, called TCP, which provided
all the transport and forwarding services in the Internet. Kahn had
intended that the TCP protocol support a range of transport services,
from the totally reliable sequenced delivery of data (virtual circuit
model) to a datagram service in which the application made
direct use of the underlying network service, which might imply occasional
lost, corrupted or reordered packets.
However, the initial
effort to implement TCP resulted in a version that only allowed for
virtual circuits. This model worked fine for file transfer and remote
login applications, but some of the early work on advanced network applications,
in particular packet voice in the 1970s, made clear that in some cases
packet losses should not be corrected by TCP, but should be left to
the application to deal with. This led to a reorganization of the original
TCP into two protocols, the simple IP which provided only for addressing
and forwarding of individual packets, and the separate TCP, which was
concerned with service features such as flow control and recovery from
lost packets. For those applications that did not want the services
of TCP, an alternative called the User Datagram Protocol (UDP) was added
in order to provide direct access to the basic service of IP.
A major initial
motivation for both the ARPANET and the Internet was resource sharing
- for example allowing users on the packet radio networks to access
the time sharing systems attached to the ARPANET. Connecting the two
together was far more economical that duplicating these very expensive
computers. However, while file transfer and remote login (Telnet) were
very important applications, electronic mail has probably had the most
significant impact of the innovations from that era. Email provided
a new model of how people could communicate with each other, and changed
the nature of collaboration, first in the building of the Internet itself
(as is discussed below) and later for much of society.
There were other
applications proposed in the early days of the Internet, including packet
based voice communication (the precursor of Internet telephony), various
models of file and disk sharing, and early "worm" programs
that showed the concept of agents (and, of course, viruses). A key concept
of the Internet is that it was not designed for just one application,
but as a general infrastructure on which new applications could be conceived,
as illustrated later by the emergence of the World Wide Web. It is the
general purpose nature of the service provided by TCP and IP that makes
this possible.
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.
Transition to Widespread
Infrastructure
At the same time
that the Internet technology was being experimentally validated and
widely used amongst a subset of computer science researchers, other
networks and networking technologies were being pursued. The usefulness
of computer networking - especially electronic mail - demonstrated by
DARPA and Department of Defense contractors on the ARPANET was not lost
on other communities and disciplines, so that by the mid-1970s computer
networks had begun to spring up wherever funding could be found for
the purpose. The U.S. Department of Energy (DoE) established MFENet
for its researchers in Magnetic Fusion Energy, whereupon DoE's High
Energy Physicists responded by building HEPNet. NASA Space Physicists
followed with SPAN, and Rick Adrion, David Farber, and Larry Landweber
established CSNET for the (academic and industrial) Computer Science
community with an initial grant from the U.S. National Science Foundation
(NSF). AT&T's free-wheeling dissemination of the UNIX computer operating
system spawned USENET, based on UNIX' built-in UUCP communication protocols,
and in 1981 Ira Fuchs and Greydon Freeman devised BITNET, which linked
academic mainframe computers in an "email as card images"
paradigm.
With the exception
of BITNET and USENET, these early networks (including ARPANET) were
purpose-built - i.e., they were intended for, and largely restricted
to, closed communities of scholars; there was hence little pressure
for the individual networks to be compatible and, indeed, they largely
were not. In addition, alternate technologies were being pursued in
the commercial sector, including XNS from Xerox, DECNet, and IBM's SNA.
8 It remained for the British JANET
(1984) and U.S. NSFNET (1985) programs to explicitly announce their
intent to serve the entire higher education community, regardless of
discipline. Indeed, a condition for a U.S. university to receive NSF
funding for an Internet connection was that "... the connection
must be made available to ALL qualified users on campus."
In 1985, Dennis
Jennings came from Ireland to spend a year at NSF leading the NSFNET
program. He worked with the community to help NSF make a critical decision
- that TCP/IP would be mandatory for the NSFNET program. When Steve
Wolff took over the NSFNET program in 1986, he recognized the need for
a wide area networking infrastructure to support the general academic
and research community, along with the need to develop a strategy for
establishing such infrastructure on a basis ultimately independent of
direct federal funding. Policies and strategies were adopted (see below)
to achieve that end.
NSF also elected
to support DARPA's existing Internet organizational infrastructure,
hierarchically arranged under the (then) Internet Activities Board (IAB).
The public declaration of this choice was the joint authorship by the
IAB's Internet Engineering and Architecture Task Forces and by NSF's
Network Technical Advisory Group of RFC 985 (Requirements for Internet
Gateways ), which formally ensured interoperability of DARPA's and NSF's
pieces of the Internet.
In addition to the
selection of TCP/IP for the NSFNET program, Federal agencies made and
implemented several other policy decisions which shaped the Internet
of today.
- Federal agencies
shared the cost of common infrastructure, such as trans-oceanic circuits.
They also jointly supported "managed interconnection points"
for interagency traffic; the Federal Internet Exchanges (FIX-E and
FIX-W) built for this purpose served as models for the Network Access
Points and "*IX" facilities that are prominent features
of today's Internet architecture.
- To coordinate
this sharing, the Federal Networking Council 9
was formed. The FNC also cooperated with other international organizations,
such as RARE in Europe, through the Coordinating Committee on Intercontinental
Research Networking, CCIRN, to coordinate Internet support of the
research community worldwide.
- This sharing
and cooperation between agencies on Internet-related issues had a
long history. An unprecedented 1981 agreement between Farber, acting
for CSNET and the NSF, and DARPA's Kahn, permitted CSNET traffic to
share ARPANET infrastructure on a statistical and no-metered-settlements
basis.
- Subsequently,
in a similar mode, the NSF encouraged its regional (initially academic)
networks of the NSFNET to seek commercial, non-academic customers,
expand their facilities to serve them, and exploit the resulting economies
of scale to lower subscription costs for all.
- On the NSFNET
Backbone - the national-scale segment of the NSFNET - NSF enforced
an "Acceptable Use Policy" (AUP) which prohibited Backbone
usage for purposes "not in support of Research and Education."
The predictable (and intended) result of encouraging commercial network
traffic at the local and regional level, while denying its access
to national-scale transport, was to stimulate the emergence and/or
growth of "private", competitive, long-haul networks such
as PSI, UUNET, ANS CO+RE, and (later) others. This process of privately-financed
augmentation for commercial uses was thrashed out starting in 1988
in a series of NSF-initiated conferences at Harvard's Kennedy School
of Government on "The Commercialization and Privatization of
the Internet" - and on the "com-priv" list on the net
itself.
- In 1988, a National
Research Council committee, chaired by Kleinrock and with Kahn and
Clark as members, produced a report commissioned by NSF titled "Towards
a National Research Network". This report was influential on
then Senator Al Gore, and ushered in high speed networks that laid
the networking foundation for the future information superhighway.
- In 1994, a National
Research Council report, again chaired by Kleinrock (and with Kahn
and Clark as members again), Entitled "Realizing The Information
Future: The Internet and Beyond" was released. This report, commissioned
by NSF, was the document in which a blueprint for the evolution of
the information superhighway was articulated and which has had a lasting
affect on the way to think about its evolution. It anticipated the
critical issues of intellectual property rights, ethics, pricing,
education, architecture and regulation for the Internet.
- NSF's privatization
policy culminated in April, 1995, with the defunding of the NSFNET
Backbone. The funds thereby recovered were (competitively) redistributed
to regional networks to buy national-scale Internet connectivity from
the now numerous, private, long-haul networks.
The backbone had
made the transition from a network built from routers out of the research
community (the "Fuzzball" routers from David Mills) to commercial
equipment. In its 8 1/2 year lifetime, the Backbone had grown from six
nodes with 56 kbps links to 21 nodes with multiple 45 Mbps links. It
had seen the Internet grow to over 50,000 networks on all seven continents
and outer space, with approximately 29,000 networks in the United States.
Such was the weight
of the NSFNET program's ecumenism and funding ($200 million from 1986
to 1995) - and the quality of the protocols themselves - that by 1990
when the ARPANET itself was finally decommissioned10,
TCP/IP had supplanted or marginalized most other wide-area computer
network protocols worldwide, and IP was well on its way to becoming
THE bearer service for the Global Information Infrastructure.
The Role of Documentation
A key to the rapid
growth of the Internet has been the free and open access to the basic
documents, especially the specifications of the protocols.
The beginnings of
the ARPANET and the Internet in the university research community promoted
the academic tradition of open publication of ideas and results. However,
the normal cycle of traditional academic publication was too formal
and too slow for the dynamic exchange of ideas essential to creating
networks.
In 1969 a key step
was taken by S. Crocker (then at UCLA) in establishing the Request
for Comments (or RFC) series of notes. These memos were intended
to be an informal fast distribution way to share ideas with other network
researchers. At first the RFCs were printed on paper and distributed
via snail mail. As the File Transfer Protocol (FTP) came into use, the
RFCs were prepared as online files and accessed via FTP. Now, of course,
the RFCs are easily accessed via the World Wide Web at dozens of sites
around the world. SRI, in its role as Network Information Center, maintained
the online directories. Jon Postel acted as RFC Editor as well as managing the centralized
administration of required protocol number assignments,
roles that he continued to play until his death, October 16, 1998
The effect of the
RFCs was to create a positive feedback loop, with ideas or proposals
presented in one RFC triggering another RFC with additional ideas, and
so on. When some consensus (or a least a consistent set of ideas) had
come together a specification document would be prepared. Such a specification
would then be used as the base for implementations by the various research
teams.
Over time, the RFCs
have become more focused on protocol standards (the "official"
specifications), though there are still informational RFCs that describe
alternate approaches, or provide background information on protocols
and engineering issues. The RFCs are now viewed as the "documents
of record" in the Internet engineering and standards community.
The open access
to the RFCs (for free, if you have any kind of a connection to the Internet)
promotes the growth of the Internet because it allows the actual specifications
to be used for examples in college classes and by entrepreneurs developing
new systems.
Email has been a
significant factor in all areas of the Internet, and that is certainly
true in the development of protocol specifications, technical standards,
and Internet engineering. The very early RFCs often presented a set
of ideas developed by the researchers at one location to the rest of
the community. After email came into use, the authorship pattern changed
- RFCs were presented by joint authors with common view independent
of their locations.
The use of specialized
email mailing lists has been long used in the development of protocol
specifications, and continues to be an important tool. The IETF now
has in excess of 75 working groups, each working on a different aspect
of Internet engineering. Each of these working groups has a mailing
list to discuss one or more draft documents under development. When
consensus is reached on a draft document it may be distributed as an
RFC.
As the current rapid
expansion of the Internet is fueled by the realization of its capability
to promote information sharing, we should understand that the network's
first role in information sharing was sharing the information about
it's own design and operation through the RFC documents. This unique
method for evolving new capabilities in the network will continue to
be critical to future evolution of the Internet.
Formation of the
Broad Community
The Internet is
as much a collection of communities as a collection of technologies,
and its success is largely attributable to both satisfying basic community
needs as well as utilizing the community in an effective way to push
the infrastructure forward. This community spirit has a long history
beginning with the early ARPANET. The early ARPANET researchers worked
as a close-knit community to accomplish the initial demonstrations of
packet switching technology described earlier. Likewise, the Packet
Satellite, Packet Radio and several other DARPA computer science research
programs were multi-contractor collaborative activities that heavily
used whatever available mechanisms there were to coordinate their efforts,
starting with electronic mail and adding file sharing, remote access,
and eventually World Wide Web capabilities. Each of these programs formed
a working group, starting with the ARPANET Network Working Group. Because
of the unique role that ARPANET played as an infrastructure supporting
the various research programs, as the Internet started to evolve, the
Network Working Group evolved into Internet Working Group.
In the late 1970's,
recognizing that the growth of the Internet was accompanied by a growth
in the size of the interested research community and therefore an increased
need for coordination mechanisms, Vint Cerf, then manager of the Internet
Program at DARPA, formed several coordination bodies - an International
Cooperation Board (ICB), chaired by Peter Kirstein of UCL, to coordinate
activities with some cooperating European countries centered on Packet
Satellite research, an Internet Research Group which was an inclusive
group providing an environment for general exchange of information,
and an Internet Configuration Control Board (ICCB), chaired by Clark.
The ICCB was an invitational body to assist Cerf in managing the burgeoning
Internet activity.
In 1983, when Barry
Leiner took over management of the Internet research program at DARPA,
he and Clark recognized that the continuing growth of the Internet community
demanded a restructuring of the coordination mechanisms. The ICCB was
disbanded and in its place a structure of Task Forces was formed, each
focused on a particular area of the technology (e.g. routers, end-to-end
protocols, etc.). The Internet Activities Board (IAB) was formed from
the chairs of the Task Forces. It of course was only a coincidence that
the chairs of the Task Forces were the same people as the members of
the old ICCB, and Dave Clark continued to act as chair.
After some changing
membership on the IAB, Phill Gross became chair of a revitalized Internet
Engineering Task Force (IETF), at the time merely one of the IAB Task
Forces. As we saw above, by 1985 there was a tremendous growth in the
more practical/engineering side of the Internet. This growth resulted
in an explosion in the attendance at the IETF meetings, and Gross was
compelled to create substructure to the IETF in the form of working
groups.
This growth was
complemented by a major expansion in the community. No longer was DARPA
the only major player in the funding of the Internet. In addition to
NSFNet and the various US and international government-funded activities,
interest in the commercial sector was beginning to grow. Also in 1985,
both Kahn and Leiner left DARPA and there was a significant decrease
in Internet activity at DARPA. As a result, the IAB was left without
a primary sponsor and increasingly assumed the mantle of leadership.
The growth continued,
resulting in even further substructure within both the IAB and IETF.
The IETF combined Working Groups into Areas, and designated Area Directors.
An Internet Engineering Steering Group (IESG) was formed of the Area
Directors. The IAB recognized the increasing importance of the IETF,
and restructured the standards process to explicitly recognize the IESG
as the major review body for standards. The IAB also restructured so
that the rest of the Task Forces (other than the IETF) were combined
into an Internet Research Task Force (IRTF) chaired by Postel, with
the old task forces renamed as research groups.
The growth in the
commercial sector brought with it increased concern regarding the standards
process itself. Starting in the early 1980's and continuing to this
day, the Internet grew beyond its primarily research roots to include
both a broad user community and increased commercial activity. Increased
attention was paid to making the process open and fair. This coupled
with a recognized need for community support of the Internet eventually
led to the formation of the Internet Society in 1991, under the auspices
of Kahn's Corporation for National Research Initiatives (CNRI) and the
leadership of Cerf, then with CNRI.
In 1992, yet another
reorganization took place. In 1992, the Internet Activities Board was
re-organized and re-named the Internet Architecture Board operating
under the auspices of the Internet Society. A more "peer"
relationship was defined between the new IAB and IESG, with the IETF
and IESG taking a larger responsibility for the approval of standards.
Ultimately, a cooperative and mutually supportive relationship was formed
between the IAB, IETF, and Internet Society, with the Internet Society
taking on as a goal the provision of service and other measures which
would facilitate the work of the IETF.
The recent development
and widespread deployment of the World Wide Web has brought with it
a new community, as many of the people working on the WWW have not thought
of themselves as primarily network researchers and developers. A new
coordination organization was formed, the World Wide Web Consortium
(W3C). Initially led from MIT's Laboratory for Computer Science by Tim
Berners-Lee (the inventor of the WWW) and Al Vezza, W3C has taken on
the responsibility for evolving the various protocols and standards
associated with the Web.
Thus, through the
over two decades of Internet activity, we have seen a steady evolution
of organizational structures designed to support and facilitate an ever-increasing
community working collaboratively on Internet issues.
Commercialization
of the Technology
Commercialization
of the Internet involved not only the development of competitive, private
network services, but also the development of commercial products implementing
the Internet technology. In the early 1980s, dozens of vendors were
incorporating TCP/IP into their products because they saw buyers for
that approach to networking. Unfortunately they lacked both real information
about how the technology was supposed to work and how the customers
planned on using this approach to networking. Many saw it as a nuisance
add-on that had to be glued on to their own proprietary networking solutions:
SNA, DECNet, Netware, NetBios. The DoD had mandated the use of TCP/IP
in many of its purchases but gave little help to the vendors regarding
how to build useful TCP/IP products.
In 1985, recognizing
this lack of information availability and appropriate training, Dan
Lynch in cooperation with the IAB arranged to hold a three day workshop
for ALL vendors to come learn about how TCP/IP worked and what it still
could not do well. The speakers came mostly from the DARPA research
community who had both developed these protocols and used them in day
to day work. About 250 vendor personnel came to listen to 50 inventors
and experimenters. The results were surprises on both sides: the vendors
were amazed to find that the inventors were so open about the way things
worked (and what still did not work) and the inventors were pleased
to listen to new problems they had not considered, but were being discovered
by the vendors in the field. Thus a two way discussion was formed that
has lasted for over a decade.
After two years
of conferences, tutorials, design meetings and workshops, a special
event was organized that invited those vendors whose products ran TCP/IP
well enough to come together in one room for three days to show off
how well they all worked together and also ran over the Internet. In
September of 1988 the first Interop trade show was born. 50 companies
made the cut. 5,000 engineers from potential customer organizations
came to see if it all did work as was promised. It did. Why? Because
the vendors worked extremely hard to ensure that everyone's products
interoperated with all of the other products - even with those of their
competitors. The Interop trade show has grown immensely since then and
today it is held in 7 locations around the world each year to an audience
of over 250,000 people who come to learn which products work with each
other in a seamless manner, learn about the latest products, and discuss
the latest technology.
In parallel with
the commercialization efforts that were highlighted by the Interop activities,
the vendors began to attend the IETF meetings that were held 3 or 4
times a year to discuss new ideas for extensions of the TCP/IP protocol
suite. Starting with a few hundred attendees mostly from academia and
paid for by the government, these meetings now often exceeds a thousand
attendees, mostly from the vendor community and paid for by the attendees
themselves. This self-selected group evolves the TCP/IP suite in a mutually
cooperative manner. The reason it is so useful is that it is comprised
of all stakeholders: researchers, end users and vendors.
Network management
provides an example of the interplay between the research and commercial
communities. In the beginning of the Internet, the emphasis was on defining
and implementing protocols that achieved interoperation. As the network
grew larger, it became clear that the sometime ad hoc procedures used
to manage the network would not scale. Manual configuration of tables
was replaced by distributed automated algorithms, and better tools were
devised to isolate faults. In 1987 it became clear that a protocol was
needed that would permit the elements of the network, such as the routers,
to be remotely managed in a uniform way. Several protocols for this
purpose were proposed, including Simple Network Management Protocol
or SNMP (designed, as its name would suggest, for simplicity, and derived
from an earlier proposal called SGMP) , HEMS (a more complex design
from the research community) and CMIP (from the OSI community). A series
of meeting led to the decisions that HEMS would be withdrawn as a candidate
for standardization, in order to help resolve the contention, but that
work on both SNMP and CMIP would go forward, with the idea that the
SNMP could be a more near-term solution and CMIP a longer-term approach.
The market could choose the one it found more suitable. SNMP is now
used almost universally for network based management.
In the last few
years, we have seen a new phase of commercialization. Originally, commercial
efforts mainly comprised vendors providing the basic networking products,
and service providers offering the connectivity and basic Internet services.
The Internet has now become almost a "commodity" service,
and much of the latest attention has been on the use of this global
information infrastructure for support of other commercial services.
This has been tremendously accelerated by the widespread and rapid adoption
of browsers and the World Wide Web technology, allowing users easy access
to information linked throughout the globe. Products are available to
facilitate the provisioning of that information and many of the latest
developments in technology have been aimed at providing increasingly
sophisticated information services on top of the basic Internet data
communications.
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.
Timeline
Footnotes
1
Perhaps this is an exaggeration based on the lead author's residence
in Silicon Valley.
2
On a recent trip to a Tokyo bookstore, one of the authors counted 14
English language magazines devoted to the Internet.
3
An abbreviated version of this article appears in the 50th anniversary
issue of the CACM, Feb. 97. The authors would like to express
their appreciation to Andy Rosenbloom, CACM Senior Editor, for both
instigating the writing of this article and his invaluable assistance
in editing both this and the abbreviated version.
4
The Advanced Research Projects Agency (ARPA) changed its name to Defense
Advanced Research Projects Agency (DARPA) in 1971, then back to ARPA
in 1993, and back to DARPA in 1996. We refer throughout to DARPA, the
current name.
5
It was from the RAND study that the false rumor started claiming that
the ARPANET was somehow related to building a network resistant to nuclear
war. This was never true of the ARPANET, only the unrelated RAND study
on secure voice considered nuclear war. However, the later work on Internetting
did emphasize robustness and survivability, including the capability
to withstand losses of large portions of the underlying networks.
6
Including amongst others Vint Cerf, Steve Crocker, and Jon Postel. Joining
them later were David Crocker who was to play an important role in documentation
of electronic mail protocols, and Robert Braden, who developed the first
NCP and then TCP for IBM mainframes and also was to play a long term
role in the ICCB and IAB.
7
This was subsequently published as 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.
8
The desirability of email interchange, however, led to one of the first
"Internet books": !%@:: A Directory of Electronic Mail
Addressing and Networks, by Frey and Adams, on email address translation
and forwarding.
9
Originally named Federal Research Internet Coordinating Committee, FRICC.
The FRICC was originally formed to coordinate U.S. research network
activities in support of the international coordination provided by
the CCIRN.
10
The decommisioning of the ARPANET was commemorated on its 20th anniversary
by a UCLA symposium in 1989.
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 Computer Communication",
August 1962.
L.
Roberts & T. Merrill, "Toward a Cooperative Network of Time-Shared
Computers", Fall AFIPS Conf., Oct. 1966.
L.
Roberts, "Multiple Computer Networks and Intercomputer Communication",
ACM Gatlinburg Conf., October 1967.
Authors
Barry
M. Leiner was Director of the Research
Institute for Advanced Computer Science. He passed away in April,
2003.
Vinton
G. Cerf is Senior Vice President, Technology Strategy, MCI.
David
D. Clark is Senior Research Scientist at the MIT
Laboratory for Computer Science.
Robert
E. Kahn is President of the Corporation
for National Research Initiatives.
Leonard
Kleinrock is Professor of Computer Science at the University
of California, Los Angeles, and is Chairman and Founder of Nomadix.
Daniel
C. Lynch is a founder of CyberCash
Inc. and of the Interop networking trade show and conferences.
Jon
Postel served as Director of the Computer Networks Division of the
Information Sciences Institute of
the University of Southern California until his untimely death October
16, 1998.
Lawrence
G. Roberts is Chairman and CTO of Caspian
Networks
Stephen
Wolff is with Cisco Systems, Inc.
A Brief History of the Internet, version 3.32
Last revised 10 Dec 2003
Send any comments to Vint Cerf
or any of the authors