Courtesy of:

1
In the Beginning...

• The Internet grew from a grass-roots society into
  a global community.
• Usenet (Users Network)
• Individual conferences organized by topics of
  interest such as
• World events
• New technology
• National elections
• Privacy issues
• Entertainment
• Computer viruses
• Generates over 100 meg of new text daily
• Does not reside on any one computer

2
Internet Planting the Seed and Growing the Plant

• Early 1960s
• Packet-switching envisioned (Baran and Davies)
• Divide a message into a smaller pieces called
  packets.
• Each packet contains where they came from and the
  address of where they are going.
• Each packet is sent to its destination
  separately.
• Provided the foundation for what became the
  Internet.
• 1966 ARPA (Advanced Research Projects Agency)
• Funded computer network research.

3
Internet Planting the Seed and Growing the Plant

• ARPANET (Advanced Research Projects Agency
  NETwork)
• Funded by ARPA.
• Pooled computer scientists and resources from
  several universities.
• In 1969, linked 4 nodes at UCLA, UC Santa
  Barbara, SRI (Stanford Research Institute) and U
  of Utah.
• By mid-1970s, linked several military sites and
  about 20 universities.
• ARPA intended to sell off the ARPANET.
• Transferred to the Defense Communications Agency
  in 1975.

4
Internet Planting the Seed and Growing the Plant

• NSF (National Science Foundation)
• In 1980, started CSnet.
• Provided a resource sharing network for computer
  science research at all universities.
• Used TCP/IP protocol.
• Linked 5 supercomputing centers with a very fast
  connection called a backbone.
• Each region surrounding the centers developed
  their own community network.
• Each community network had exclusive access to
  the backbone.
• Became known as NSFnet.

5
Internet Planting the Seed and Growing the Plant

• In 1983, ARPANET split.
• Part remained ARPANET universities, research
  institutes.
• Part became Milnet non-classified military
  information.
• Converted from Network protocol to TCP/IP
  protocol.
• In 1989, majority of ARPANET switched to NSFs
  backbone.
• Became what is known as the Internet.
• Early 1995 Information Superhighway.

6
UNIX, Gurus, and Gophers

• With the thousands of computers running the UNIX
  operating system, and freely distributed TCP/IP
  software suite
• Original access to the Internet had UNIX feel.
• Exact addresses were needed to access
  information.
• Addresses were strings of numbers
• Address for UCSD 128.54.16.1
• UNIX gurus ran the net.
• Gopher (University of Minnesota)
• Land of the Golden gophers.
• Introduced first improvement to accessing the
  Internet.
• Menu-driven system gave access to databases of
  information.
• Were once over 5,000 gopher servers.

7
UNIX, Gurus, and Gophers
Internet Gopher Information Client
v2.1.3 Home Gopher server gopher.tc.umn.edu
1. Information About Gopher/ 2. Computer
Information/ 3. Discussion Groups/ 4. Fun
Games/ 5. Internet file server (ftp)
sites/ 6. Libraries/ 7. News/ 8. Other Gopher
and Information Servers/ 9. Phone
books/ 10. Search Gopher Titles at the
University of Minnesota lt?gt 11. Search lots of
places at the university of Minnesota
lt?gt 12. University of Minnesota Campus
Information/ Press ? For Help, q to Quit, u to
go up a menu

8
UNIX, Gurus, and Gophers

• Searching for information on the Internet from
  Gopher
• Veronica
• Very Easy Rodent-Oriented Netwide Index to
  Computerized Archives.
• Indexed the entries of all of the known Gopher
  menus.
• Updated about twice weekly.
• Archie
• Searched ftp archive sites.
• These files were for downloading by using the
  Internet.
• Has more than 1,000,000 filenames today.
• Currently accessible through the WWW.

9
The Internet Growing

• Popular Internet functions illustrate the
  diversity of Internet use
• Information gathering
• University sites provide class and faculty
  information, books, library sources, lists of
  government documents
• Employment offices could provide vacancy notices
• Governmental agencies provide informational
  documents
• Students and academic researchers could use
  online bibliographies

10
The Internet Growing

• MUDs - Multi-User Dungeons
• MOOs - MUDs Object-Oriented
• Both are an outgrowth of Dungeons and Dragons
  role playing games of the 70s and 80s.
• Can play with people all over the world.
• There are more than 500 active MUDs.

11
The Internet Growing

• IRC - Internet Relay Chat
• Real-time online chat facilities
• Communication is accomplished via typing text
  over a channel

12
Communication Basics The Physical Topology

• Types of connection - Physical connection versus
  wireless.
• Network A Collection of computers, display
  terminals, printers, and other devices linked
  either by physical or wireless means.
• Node Any device on a network. Each device has a
  unique address assigned to it by the network.
• Network links Connections between computers and
  other electronic devices.

13
Communication Basics The Physical Topology

• The physical media used to connect the networks
  are Twisted pair, coaxial cable, fiber optic
  cable, and space.
• Three types of wireless communication commonly
  used in networking Infrared, Radio frequency,
  Microwave.

14
Communication Basics The Physical Topology

• Three physical types of links used in networks.

15
Communication Basics The Physical Topology

• Wireless communication.

16
Communication Basics The Physical Topology

• Properties of Transmission
• Each link has common attributes
• 1. Type of signal communicated (analog or
  digital)
• 2. The speed at which the signal is transmitted.
• 3. The type of data movement allowed on the
  channel.
• Simplex transmission - One way transmission.
• Half-duplex transmission - Can flow only one way
  at a time.
• Full-duplex transmission - Two-way at the same
  time.
• 4. The method used to transport the data
  Asynchronous, synchronous.
• 5. Single channel and multichannel transmission.

17
Communication Basics The Physical Topology

• Type of signal communicated.
• Analog - A continuously changing signal similar
  to that found on the speaker wires of a
  high-fidelity stereo system.
• Digital - Signals consist of pulses of electrical
  energy that represent 0s or 1s.

18
Communication Basics The Physical Topology

• Speed of signal.
• In digital systems Speed is measured in...
• Bits per second (bps).
• The number of bits (0s and 1s) that travel down
  the channel per second.
• Baud rate
• The number of bits that travel down the channel
  in a given interval.
• The number is given in signal changes per second,
  not necessarily bits per second.

19
Communication Basics The Physical Topology

• MODEM - MOdulator DEModulator
• Outgoing Converts binary data from computer
  (digital) into telephone compatible signals
  (analog).
• Incoming Converts telephone signal (analog) into
  binary data for the computer (digital).
• Can be an external or internal device (usually a
  card).

20
Communication Basics The Physical Topology

• Speed of Signal Sample bps and baud rate speeds.

300 bps (300 baud) Painfully slow to the
college-level reader 1200 bps (1200 baud) Good
reader can keep up 2400 bps (2400 baud) A speed
reader would get the general idea 9600 bps
(9600 baud) Impossible to read 14.4 K bps (not
measured in baud) 14,400 bps 28.8 K bps Minimum
desired for WWW (needed for receiving images
and sound) 33.6 K bps 56 K bps Download speed
is 56 K bps. Sending speed is much
less. These speeds are restricted to the maximum
speed of the modem at the other end of the
connection. If the Internet connection modem is
limited to 28.8 K, then even if your modem is 56
K, it is limited to the 28.8 K speed!
21
Communication Basics The Physical Topology

• Linking Computers Together -
• Network - 2 or more devices are linked together.
• Node - Individual devices on the network.
• Direct link networks - One whose nodes have
  direct connections through either physical or
  wireless links.
• Point to point link - Simplest of networks where
  a connection is made between computer systems.
• Ways to link the nodes of a network
• bus, ring, star, tree, and the fully connected
  topology networks.

22
Communication Basics The Physical Topology

• Networks not directly linked
• Internetworking - (Hybrid networks)
• Linking any type of direct linked networks
  together.
• Can be as small as connecting two computers
  together to as large as the largest of all, the
  Internet.
• Demand special software to allow information to
  be exchanged between them.

23
Communication Basics The Physical Topology

• Categorizing networks according to size
• DAN (Desk Area Network)
• LAN (Local Area Network)
• MAN (Metropolitan Area Network)
• WAN (Wide Area Network)

24
The Software Architecture of the Network

• Problem
• Connect several different machines running
  different operating systems (Windows, OS/2,
  MacOS, UNIX, VMS..)
• Now, try to send email, data or files between
  them.
• Solution
• Create a set of rules, or protocols, that, when
  followed, will allow an exchange of information.
• Sometimes in a collection of programs called a
  protocol suite.
• Network Architecture The overall organization of
  the rules of the network and is implemented in a
  set of programs called the protocol suite.

25
The Software Architecture of the Network

• The Internet Architecture is based on a
  four-layer protocol.

FTP
HTTP
NV
TFTP
TCP
UDP
IP
Network 1
Network 2
Network N
26
The Software Architecture of the Network

• The Internet is referred to as a packet-switching
  network.
• Packet - The Internet chunks information into
  packets.
• Once a file is requested, it is split into
  packets.
• Contains information regarding content, where it
  came from, where it is supposed to go.
• Each packet is assigned a number.
• As the packet travels through the Internet from
  network to network
• Each packet may not travel through the same path
  through the Internet to its destination.
• Each network has its own packet-limiting size.
• Packets are often packaged and repackaged.
• They are reconstructed in order when they reach
  the destination.

27
The Software Architecture of the Network

• Problem If someone wants his own WWW site, he
  must find a home for it.
• Solution
• Server -
• A dedicated computer that is part of a network.
• The hard drive contains files that are served
  to whatever requests them.
• Could be data, programs, or home pages for the
  WWW.
• The server normally runs the networking software.

28
The Software Architecture of the Network

• Types of nodes important to networks.

Hub A device that repeats or broadcasts the
network stream of information to individual nodes
( usually personal computers) Switch A device
that receives packets from its input link, and
then sorts them and transmits them over the
proper link that connects to the node addressed.
Bridge A link between two networks that have
identical rules of communication. Gateway A
link between two different networks that have
different rules of communication. Router A node
that sends network packets in one of many
possible directions to get them to their
destination.