Transcript No Slide Title

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
Courtesy of:
The Computer Continuum
Internet: Planting the Seed
and Growing the Plant
 Early 1960’s
 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.
Courtesy of:
The Computer Continuum
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-1970’s, linked several military sites and about 20
universities.
 ARPA intended to sell off the ARPANET.
 Transferred to the Defense Communications Agency in 1975.
Courtesy of:
The Computer Continuum
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.
Courtesy of:
The Computer Continuum
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 NSF’s backbone.
 Became what is known as the Internet.
 Early 1995: “Information Superhighway.”
Courtesy of:
The Computer Continuum
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.
Courtesy of:
The Computer Continuum
UNIX, Gurus, and Gophers
Internet Gopher Information Client v2.1.3

Home Gopher server: gopher.tc.umn.edu
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
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Information About Gopher/
Computer Information/
Discussion Groups/
Fun & Games/
Internet file server (ftp) sites/
Libraries/
News/
Other Gopher and Information Servers/
Phone books/
Search Gopher Titles at the University of Minnesota <?>
Search lots of places at the university of Minnesota <?>
University of Minnesota Campus Information/
Press ? For Help, q to Quit, u to go up a menu
Courtesy of:
The Computer Continuum
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:
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


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.
Courtesy of:
The Computer Continuum
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
Courtesy of:
The Computer Continuum
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.
Courtesy of:
The Computer Continuum
The Internet Growing
 IRC - Internet Relay Chat
 “Real-time” online chat facilities
 Communication is accomplished via typing text over a “channel”
Courtesy of:
The Computer Continuum
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.
Courtesy of:
The Computer Continuum
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.
Courtesy of:
The Computer Continuum
Communication Basics: The
Physical Topology
 Three physical types of links used in networks.
Courtesy of:
The Computer Continuum
Communication Basics: The
Physical Topology
 Wireless communication.
Courtesy of:
The Computer Continuum
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.
Courtesy of:
The Computer Continuum
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 0’s or 1’s.
Courtesy of:
The Computer Continuum
Communication Basics: The
Physical Topology
 Speed of signal.
 In digital systems: Speed is measured in...
 Bits per second (bps).
• The number of bits (0’s and 1’s) 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.
Courtesy of:
The Computer Continuum
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”).
Courtesy of:
The Computer Continuum
Communication Basics: The
Physical Topology
 Speed of Signal: Sample bps and baud rate speeds.
300 bps
1200 bps
2400 bps
9600 bps
14.4 K bps
28.8 K bps
33.6 K bps
56 K bps
(=300 baud)
(=1200 baud)
(=2400 baud)
(=9600 baud)
(not measured in baud)
Painfully slow to the college-level reader
Good reader can keep up
A speed reader would get the general idea
Impossible to read
14,400 bps
Minimum desired for WWW
(needed for receiving images and sound)
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!
Courtesy of:
The Computer Continuum
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.
Courtesy of:
The Computer Continuum
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.
Courtesy of:
The Computer Continuum
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)
Courtesy of:
The Computer Continuum
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.
Courtesy of:
The Computer Continuum
The Software Architecture of
the Network
 The Internet Architecture is based on a four-layer protocol.
FTP
HTTP
NV
TCP
TFTP
UDP
IP
Network #1
Network #2
Courtesy of:
The Computer Continuum
Network N
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.
Courtesy of:
The Computer Continuum
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.
Courtesy of:
The Computer Continuum
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.
Courtesy of:
The Computer Continuum