Transcript C o n t e n t s

Unit Four
Internet
1.Passage One.
A Short Introduction
Training target:
In this part，our target is to train your
reading comprehension. We have made the
flexible sentences strong black and marked
the subject，predicate and object of them.
Try to grasp the main idea of these
sentences.
Text
. Internet is a giant global and open computer
network，which is a collection of
interconnected networks. It is also a way to
realize world-wide information exchanging
and resource sharing between international
computers.
The original Internet was ARPANET（Advanced
Research Projects Agency Network），which was
established by U.S. Department of Defense
in1969.The ARPANET was used to share data
between some separated military institutes and
universities in region. By 1972 the network had
expanded to incorporate 40 nodes. ARPANET soon
became a forum for the exchange of information
and ideas among scientists and academics，and
within a few years the number of computers
connected to the network increased to more
than100.
By the mid-1970s，many U.S. government
agency networks had been linked by ARPANET
and，because the networks were of a disparate
nature，a common network protocol called
TCP/IP（Transmission Control Protocol. Internet
Protocol）was developed and became the
standard for internetworking military computers.
So U.S. Department of Defense Advanced
Research Program Management Bureau ① asked
all hosts connected with ARPANET to adapt
TCP.IP to be their protocol in1983. In1985，
the U.S.NSF ① established a specially
used net which connected six super
computing centers—NSFNET. This is the
basic of Internet. With the network
developing in all society，a lot of institutes
and universities established their LANs，and
connected them to NSFNET. In1989，the
ARPANET had been dismissed and the
NSFNET had been opened to the public and
became the most important backbone of
Internet.
When the U.S. developing their national net，the
other countries were developing too. At the end
of1980s，interlinkage of different countries’ computer
net appears. After that there were countries joining in
every year and getting to form the present Internet.
The word “Internet” became the common term for
referring to the worldwide network of military，
research and academic computers. Now，there
are86countries directly connected with Internet
and150countries can access it by E-mail. It is growing
so quickly that nobody can say exactly how many
users are “On the Net”.
First，let us see how to access the Internet.
Access to the Internet falls into two broad
categories: dedicated access and dial-up
access. With dedicated access，a computer
is directly connected to the Internet via a
router，or the computer is part of a network
linked to the Internet. With dial-up access，
a computer is connected to the Internet with
a telephone line using a modem.
Internet makes all kinds of physical net
connection to be a whole one. All
computers that adapt TCP/IP protocol can
communicate with any computer of
Internet and can be looked as a part of
Internet. Host is the computer that directly
connects with Internet. All the hosts are in
equal class in Internet，no matter they
belong to LAN，MAN or WAN. They are
all in equal class in communicating data
and sharing resources.
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The End