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CONTENTS:
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Where "The Internet" came from:
- The Internet was born in early 1969 as a U.S. Defense Department network
called the ARPAnet.
- The ARPAnet was an experimental network designed to support military
research about how to build networks that could withstand partial outages and
still function.
- The ARPAnet grew from four computers [University of Utah, UC Santa
Barbara, UCLA, Stanford Research Institute (SRI) International] to 50
universities and research facilities (all involved in military technology
projects) by 1972.
- ARPAnet evolved into DARPAnet--ARAPnet plus Milnet, an unclassified DOD
network connected to ARPAnet by a gateway. The DARPAnet eventually became known
as just the Internet.
- NSFnet was developed in the late 1980s to connect its five
supercomputer centers. NSFnet used the Internet (DARPAnet) as its model,
using the same TCP/IP protocol suite. Eventually, all publicly and privately
funded networks joined the regional NSFnet network. ARPAnet was dismantled in
1990. Thus NSFnet became "The Internet."
How The Internet is managed:
- Internet Society, or ISOC, is a voluntary membership organization whose
purpose is to promote global information exchange thorough Internet technology.
It appoints a council (the Internet Architecture Board or the IAB), which has
responsibility for the technical management and direction of the Internet.
- Another volunteer group, the Internet Engineering Task Force (IETF),
meets regularly to discuss operational and near-term technical problems of the
Internet and form working groups to investigate important enough problems.
- The Internet is paid for by the users. That is, each person or group
pays for their part of the Internet--the hardware, the connections, etc.
Therefore, the Internet is not a network itself, but a collection of networks.
When there is a problem, the separate networks are responsible for fixing
problems on their own parts of the Internet.
How the Internet works:
- Modern networking is built around the concept of layers of service. The
lowest level consists of wires and hardware, has some problems. A layer of
basic software handles the problems of hardware. Another layer of software
gives the basic software some desirable features. You continue to add
functionality to the network, one layer at a time.
- The internet works on a packet switch network (like the postal service
versus a circuit switched network of the phone company).
- All Internet communications--whether it's files, WWW pages, or
e-mail--is divided into small chunks called packets that are sent individually
and reassembled when they reach their destination. Packets are usually 1-1500
characters. (This way no one user can monopolize the net.)
- The different pieces of the Internet are connected by a set of
computers called routers, which connect networks together. Each router does
not have a connection to every other router, so message must hop from one
router to another until it reaches its destination.
- The Internet Protocol (IP) takes care of addressing or making sure that
the routers know what to do with your data when it arrives.
- Message are broken into packets before sending and each packet is
addressed to its destination. There is no guarantee the different packets of
the same message will travel the same routes or that the first packet sent
will bethe first packet received at the destination.
- The Transmission Control Protocol (TCP) takes the information you want
to transmit and breaks it into pieces. It numbers each piece so receipt can be
verified and the data can be put back in the proper order.
- TCP has an envelop of its own. A message part is placed inside a TCP
packet and the TCP packet inside an IP packet, which can then be transmitted by
the network. On the receiving side, a TCP software package collects the
envelopes, extracts the data, and puts it in the proper order. If some are
missing, it asks the sender to retransmit them. Once it has all the information
in the proper order, it passes the data to whatever application program is
using its services.
- The User Datagram Protocol (USP) is simpler than TCP. It doesnUt care
about guaranteeing delivery, missing packets, keeping data in the right order,
etc. It is for short messages that can be contained in one packet. USP sends a
message and then resends it if a response does not come in a short time.
- IP addresses are made up of four number, each less than 256, separated
by periods; for example, 128.234.7.9. IP addresses are fine for machines
communicating with machines, but humans prefer names. Therefore computers on
the Internet were given names for the convenience of their human users.
- The Domain Name System (DNS) is a method to administer names by giving
different groups responsibility for subsets of the names. Each level in this
system is called a domain. The domains are separated by periods:
scsu.ctstateu.edu, yahoo.com, etc. There are a variable number of domains
within the name but practically there are usually five or less. Each domain
group can create or change whatever lies within it.
- There are six original highest level domains: com (for businesses); edu
(for education organizations; gov (for non-military government organizations);
mil (for the military); org (for other organizations); and net (for network
resources). These names correspond to the highest level domains for
organizations.
- Top level domains also divide responsibilities for names among foreign
countires. Countires have a two letter domain name which correspond to the
highest level domains for countries, eg. CA (for Canada), IT (for Italy), UK
(for the United Kingdom). The U.S. has its own country code (US), although it
isn't used too often, and geographical domains, such as VA (for Virginia) and
IL (for Illinois).
- Both organizational and geographical names are used. There is no way to
convert between organizational names and geographical names. Some computers will
have both names.
- When you send a message addressed to a domain name, your local server
automatically converts it to an IP address and sends it on its way. (Note: you
could choose to address your message with an IP address.)
- The pieces of a domain-style name tell you who is responsible for
maintaining the name. It may tell you nothing about who is responsible for
maintaining the computer corresponding to that IP address, where the machine is
located, or what network it is located on.
- A machine can have multiple names, for example a name for each of the
services it offers. When a service moves to another machine , the name follows
the service to a new machine and the IP address for the name is changed to
point to the new location.
In summary:
- The Internet is communication.
- The most important aspect of the Internet is information it contains.
- On the whole, the Internet is self-governing and what it is about is
cooperation.
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