20 YearsOne Standard:
The Story of TCP/IP
Jonathan B. Spira
published: 4 April 2003
[Note: This commentary was first published
in the January 1, 2003, issue of the Basex: TechWatch
The story of
TCP/IP grew out of the experiences Robert Kahn had with the
Interface Message Processor (IMP). Kahn had joined DARPA after
helping Bolt Beranek Newman build a new government/research
network, the ARPANET. He had the idea that ultimately led
to a new protocol, and in 1973 joined forces with Vinton Cerf,
then a faculty member at Stanford. Cerf had been working with
the Network Control Protocol (NCP) at UCLA; this experience
made them the perfect team to collaborate on the development
of what was to become TCP/IP.
Kahn and Cerf were acutely aware of the difficulties of making
computer communication more widespread; heterogeneous computers
with differing operating systems needed to communicate freely.
Their eventual design was prescient, as todays Internet
is a decentralized system; each node (regardless of its function,
e.g. as a Web server, a Web browser, a mail server) is a peer
and this aspect is perhaps the greatest reason for the Internets
Kahn and Cerf, in the summer of 1973, prepared a paper entitled
A Protocol for Packet Network Intercommunication.
The document described a new protocol that acted like an envelope,
carrying parts of a letter inside; the broken up letter pieces
were called segments. This new protocol was called
the Transmission Control Protocol (TCP). The paper was published
the following May in the IEEE Transactions on Communications.
[V.G. Cerf and R.E. Kahn, A Protocol for Packet Network
Interconnection, IEEE Transactions on Communications
COM-22 (May 1974): 637-48.]
In 1977, BBN used TCP for the very first time on a UNIX system.
In 1978, Cerf, Jon Postel (1948-1998), then Director of the
University of Southern Californias Information Sciences
Institute (ISI), Computer Networks Division, and Danny Cohen,
in a meeting at ISI, decided to split TCP into two separate
protocols. [end of page 1] The result was TCP and the Internet
Protocol (IP). TCP retained the responsibility for breaking
up the segments and messages and reassembling the packets
at the destination. IP was responsible for transmitting the
individual segments across the network. IP essentially addressed
the envelope and ensured it reached its proper
In November of 1981, Postel posted Request for Comment (RFC)
801, the NCP/TCP Transition Plan. The RFC outlined a migration
path from the ARPANETs Network Computer Protocol, or
NCP, to TCP/IP. The installation of the ARPANET itself had
begun in September 1969, and it was operational by 1971. When
Postel penned RFC 801, the ARPANET had been in operational
service for over ten years. In the years leading up to 1981,
ARPA had sponsored research to evolve the ARPANET. There was
great interest in digital packet broadcast radio and satellite
networks. There was also much interest in local networks.
Although the Network Control Protocol, or NCP, had run ARPANET
since its inception, it was inadequate as a foundation for
future network growth. NCP was designed to guarantee delivery
of every data packet a user might transmit. However, as ARPANET
grew more complex and its volume of usage increased, this
built-in failsafe made the network less scalable. In addition,
other networks were beginning to develop but were unable to
communicate with each other.
TCP, on the other hand, allowed the network to lose a packet
occasionallywithout compromising the integrity of the
transmissionin order to improve the efficiency of the
flow and reduce the networks vulnerability to any disruptions
(such as the link between sender and receiver).
Postel, in the RFC, noted that the Department of Defense
had recently adopted the internet concept and
the IP and TCP were now DoD standards for all DoD packet networks.
Computerworld, in February 1982, proclaimed that [T]wo
communications protocols [are] expected to appear this year
in commercial DP products . . . [and will] allow major reductions
in data communications costs.
By then, vendors such as Xerox and 3Com were getting on the
TCP/IP bandwagon, although some experts were cautioning that
mainframe operating systems from IBM and other major vendors
were too complex for TCP/IP to be added in a cost-effective
In writing what was to be a kind of network independence
manifesto (declaration of network independence?), Postel took
care to proclaim this sea change with a caveat, one that is
very revealing of the collaborative culture of the nascent
Internet of the day: As with all new systems, there
will be some aspects which are not as robust and efficient
as we would like (just as with the initial ARPANET). But with
your help, these problems can be solved and we can move into
an environment with significantly broader communication services.
[end of page 2]
Postel outlined a schedule, which called for Full Internet
Service on January 1, 1983. This was specifically defined
All hosts are TCP-capable and use TCP-based
services. NCP is removed from service, relay services end,
all services are TCP-based.
Postel had a very long-term outlook for the new
ARPANET. He also knew that many developers might be tempted
to advance short-term goals at the cost of long-term growth.
His caution still rings true today:
There are some very tempting shortcuts
in the implementation of IP and TCP. DO NOT BE TEMPTED!
Others have and they have been caught!
The close of the last century was perhaps marked by a new
way of telling time, famously called Internet time by many.
Surely the Internet has speeded up processes, relationships,
and given an entirely new meaning to instant gratification.
However, to its credit, the Internet itself changes on what
might best be described as the antithesis of Internet time.
The Internet actually took the first twenty years, from 1973
to 1993, of its existence to gain a foothold. In the past
ten years, 1993-2003, the Internet assumed a place of mammoth
importance in the worlds of commerce, government, and society
so much so that it would be difficult to imagine a world sans
The secret of the Internets success was its adherence
to standards, a philosophy which forward thinking computer
scientists such as Kahn and Cerf instilled in it. In fact,
the history of TCP is a textbook example of why standards
are of paramount importance: they should never be underestimated.
In a universe without TCP/IP, the computer world would still
be searching for its lingua franca, possibly even paralyzed
by a babel of strange and unintelligible languages. [end of
Jonathan B. Spira, 20 Years-One Standard:
The Story of TCP/IP, Iterations: An Inter-disciplinary
Journal of Software History 2 (April 4, 2003): 1-3.
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