Internet Architecture
Lecture 1:
What Is the Internet?
Assistant Teacher Samraa Adnan Al-Asadi
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Introduction
One of the most frequently asked questions
about the Internet is "Who runs it?" The truth is
that no centralized management of the Internet
exists. Instead, it is a collection of thousands of
individual networks and organizations, each of
which is run. Each network cooperates with
other networks to direct Internet traffic so that
information can pass among them. Together,
these networks and organizations make up the
world of the Internet.
Assistant Teacher Samraa Adnan Al-Asadi
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Introduction
The Internet isn't a single network; it is a vast network of
networks. No single person, group, or organization runs the Internet.
The Internet was created by the Advanced Research Projects
Agency (ARPA) and the U.S. Department of Defense for scientific
and military communications.
The Internet is a network of interconnected networks. Even
if part of its infrastructure was destroyed, data could flow through
the remaining networks.
The Internet uses high-speed data lines, called backbones, to
carry data. Smaller networks connect to the backbone, enabling any
user on any network to exchange data with any other user.
Internetworking: the process of connecting separate
networks.
Assistant Teacher Samraa Adnan Al-Asadi
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How the Internet Works: TCP/IP
The networks communicate with one another based
on certain protocols, such as the Transmission Control
Protocol (TCP) and the Internet Protocol (IP). More and
more networks and computers are being hooked up to the
Internet every day.
Tens of thousands of these networks exist, ranging
from university networks to corporate local area networks
to large online services such as America Online and MSN.
Every time you tap into the Internet, your own
computer becomes an extension of that network.
Assistant Teacher Samraa Adnan Al-Asadi
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How the Internet Works:
Routing Traffic Across the Internet
Most computers don't connect directly to the Internet.
Instead, they connect to a smaller network that is
connected to the Internet backbone.
The Internet includes thousands of host computers
(servers), which provide data and services as requested by
client systems.
When you use the Internet, your PC (a client) requests
data from a host system. The request and data are broken
into packets and travel across multiple networks before
being reassembled at their destination.
Assistant Teacher Samraa Adnan Al-Asadi
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How the Internet Works:
Routing Traffic Across the Internet
Packets of information flow between machines
governed by common rules (protocols):
- Internet protocol (IP)
- Transport control protocol (TCP)
Internet is a packet-switching network. Messages
are decomposed into packets, containing part of the
message, plus information on the sending and receiving
machines and how the packet relates to the other packets.
Packets travel independently and possibly on different
routes through the Internet. Packets are reassembled into
the message at the receiving machine.
Assistant Teacher Samraa Adnan Al-Asadi
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How the Internet Works:
Routing Traffic Across the Internet
Assistant Teacher Samraa Adnan Al-Asadi
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How the Internet Works: Addressing Schemes
In order to communicate across the Internet, a
computer must have a unique address.
Every computer on the Internet has a unique
numeric identifier, called an Internet Protocol
(IP) address.
Each IP address has four parts – each part a
number between 0 and 255. An IP address might
look like this: 205.46.117.104.
Assistant Teacher Samraa Adnan Al-Asadi
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For networks and computers to cooperate, a
general agreement must take place about things
such as Internet procedures and standards for
protocols. These procedures and standards are
laid out in requests for comment (RFCs) that are
agreed on by Internet users and organizations.
Assistant Teacher Samraa Adnan Al-Asadi
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A variety of groups guide the Internet's growth by
helping to establish standards and by educating people on
the proper way to use the Internet.
Perhaps the most important is the Internet Society,
a private, nonprofit group. The Internet Society supports
the work of the Internet Architecture Board (IAB), which
handles much of the Internet's behind-the-scenes and
architectural issues. The Internet Engineering Task Force
(IETF) is responsible for overseeing how the Internet's
TCP/IP protocols evolve.
Assistant Teacher Samraa Adnan Al-Asadi
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The World Wide Web Consortium (W3C)
develops standards for the evolution of the most
well-known part of the Internet, the World Wide
Web (find it at www.w3.org). The W3C is an
industry consortium run by the Laboratory for
Computer Science at the Massachusetts Institute
of Technology (MIT).
Assistant Teacher Samraa Adnan Al-Asadi
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Private companies oversee the registration of
Internet domains, such as www.zdnet.com or
www.quepublishing.com. These companies, called
registrars, all must cooperate with one another to
ensure that only one person or company can own a
particular domain and that all the domains work
properly. The registrars compete with one another as
well in allowing people and businesses to register
domains. Registering a domain costs money, and the
Registrars compete on cost and on giving extra
services to those who buy domains.
Assistant Teacher Samraa Adnan Al-Asadi
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Although all these types of organizations are
important for holding together the Internet, at the heart of
the Internet are individual local networks. These networks
can be found in private companies, universities,
government agencies, and online services. They are
funded separately from each other and in a variety of
manners, such as fees from users, corporate support,
taxes, and grants. Many Internet service providers (ISPs),
which provide Internet access for individuals, have
networks as well. Individuals who want to access the
Internet pay ISPs a monthly connection rate, so in that
sense, everyone who uses the Internet helps pay for it.
Assistant Teacher Samraa Adnan Al-Asadi
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The networks are connected in a variety of
ways. For efficiency's sake, local networks join
in consortiums known as regional networks. A
variety of leased lines connect regional and local
networks. The leased lines that connect networks
can be as simple as a single telephone line or as
complex as a fiber-optic cable with microwave
links and satellite transmissions.
Assistant Teacher Samraa Adnan Al-Asadi
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Assistant Teacher Samraa Adnan Al-Asadi
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Private companies who make money by
selling access to their lines build backbones,
which are very high-capacity lines that carry
enormous amounts of Internet traffic.
Government agencies, such as NASA, and large
private corporations pay for some of these
backbones. The National Science Foundation
also pays for some backbones.
Assistant Teacher Samraa Adnan Al-Asadi
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Introduction
Assistant Teacher Samraa Adnan Al-Asadi
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Introduction
Assistant Teacher Samraa Adnan Al-Asadi
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Thank you
Assistant Teacher Samraa Adnan Al-Asadi
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