practice
Doi: 10.1145/1924421.1924438
Article development led by
queue.acm.org
Knowing where to begin is half the battle.
By thomas a. LimonCeLLi,
With an intRoDuCtion By Vinton G. CeRF
successful
strategies for
iPv6 Rollouts.
Really.
ThE dESIGn of TCP/IP began in 1973 when Robert
Kahn and I started to explore the ramifications of
interconnecting different kinds of packet-switched
networks. We published a concept paper in May
1974,
2 and a fairly complete specification for TCP was
published in December 1974.1 By the end of 1975,
several implementations had been completed and
many problems were identified. Iteration began,
and by 1977 it was concluded that TCP (by now
called Transmission Control Protocol) should be
split into two protocols: a simple Internet Protocol
that carried datagrams end to end through packet
networks interconnected through gateways; and a
TCP that managed the flow and sequencing of packets
exchanged between hosts on the contemplated
Internet. This split allowed for the possibility of real
time but possibly lossy and unsequenced packet delivery to support
packet voice, video, radar, and other
real-time streams.
By 1977, I was serving as program
manager for what was then called the
Internetting research program at DARPA (U.S. Defense Advanced Research
Projects Agency) and was confronted
with the question, “How much address
space is needed for the Internet?”
Every host on every network was assumed to need an address consisting
of a “network part” and a “host part”
that could uniquely identify a particular computer on a particular network.
Gateways connecting the networks of
the Internet would understand these
addresses and would know how to
route Internet packets from network
to network until they reached the destination network, at which point the
final gateway would direct the Internet
packet to the correct host on that network.
A debate among the engineers and
scientists working on the Internet ran
for nearly a year without a firm conclusion. Some suggested 32-bit addresses
( 8 bits of network, 24 bits of host),
some said 128 bits, and others wanted
variable-length addresses. The last
choice was rejected by programmers
who didn’t want to fiddle around finding the fields of an Internet packet. The
128-bit choice seemed excessive for an
experiment that involved only a few
networks to begin with. By this time,
the research effort had reached its
fourth iteration (the IP layer protocol
was called IPv4), and as program manager, I felt a need to get on with live
testing and final design of TCP and IP.
In lieu of consensus, I chose 32 bits of
address. I thought 4. 3 billion potential
addresses would be adequate for conducting the experiments to prove the
technology. If it worked, then we could
go back and design the production version. Of course, it is now 2011, and the
experiment never exactly ended.
The Internet Corporation for Assigned Names and Numbers (ICANN)
succeeded Jonathan Postel as the op-
