Transcript Chapter 7:

Chapter 7:
The Internet, Intranets, and Extranets
Agenda
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What is the Internet
IP Addresses
How the Internet Works
The Domain Name System (DNS)
How E-mail Finds its Way
Internet Communication Protocols
How to Connect to the Internet
Internet Services
Basic Internet Software
Telnet Software
FTP Software
The World Wide Web
Intranets and Extranets
Virtual Private Networks
Privacy and Security
What is the Internet
 The Internet is a collection of interconnected networks, all
freely exchanging information.
 The Internet is actually a network of networks: tens of
thousands of computers connected in a web, talking to one
another through a common communications protocol.
IP Addresses
 Every node on the Internet has a unique Internet number
called an IP address. IP addresses are 32 bits long and
consist of four parts (called dotted-quads) that are
separated by the period. For example: 129.34.139.30
 The octets are numbers in each quad and are used to
identify a particular network and a host node on that
network. In general, the leading portion of each IP address
identifies the network number and the last number
identifies the specific computer.
How the Internet Works
 On this "highway" of network connections, routers provide
Internet traffic control. The primary purpose of routers is to
find the best path among available alternatives by which to
send data.
 The Internet transmits a message from one computer to
another either directly (in the same network) or through a
router till the message reaches its destination.
 Messages are passed around in chunks, called packets,
each of which carries the address of the sender and the
receiver.
 The set of conventions used to pass packets from one
computer to another is the combination of the Transport
Control Protocol (TCP) and the Internet Protocol (IP).
The Domain Name System (DNS)
 Because the IP addresses are hard to remember, the Internet supports
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the use of a text name that can be substituted for the IP address. The
text version of the IP address is called a domain name. Each domain
name is mapped to a particular numeric address.
To translate and track domain names, we use the Domain Name
System (DNS), which is a set of distributed databases containing IP
addresses and their corresponding domain names. DNS servers
perform the translation back and forth between names and numbers
(i.e., saclink.CSUS.edu).
The top-level domain indicates the class of institution to which the
server belongs to the Internet (i.e., edu).
The second-level domain is registered by an organization (i.e., CSUS).
The first item is the name of the host computer, or the hostname (i.e.,
saclink).
How E-mail Finds its Way
The e-mail address consists of several segments that
combine geographical and conceptual information. For
example:
[email protected]
 The sytsai element identifies the user or organization
(who)
 The @ symbol connects the (who) with (where)
 The saclink.CSUS is the sub-domain and the domain
(where)
 The edu identifies the type of the organization (what)
Internet Communication Protocols
 TCP/IP is the Internet’s suite of network protocols that allow different
computers to communicate.
 The Transmission Control Protocol (TCP) is responsible of end-to-end
message delivery in terms of priority, error free, in sequence, no loss or
duplication.
 The Internet Protocol (IP) operates at the network layer, breaks the
message into packets called datagrams, and provides addresses for
each datagram.
 Underneath TCP/IP sit various media protocols that help move the data
over various networks on the Internet.
– HTTP (Hypertext Transport Protocol) is used by WWW applications
– NNTP (Network News Transport Protocol) is used by Usenet news
applications
– SMTP (Simple Mail Transport Protocol) is used by E-mail applications
How to Connect to the Internet
 On-Line service connection requires using a communications software
and modem to connect to an on-line information service company that
provides internet services. An example would be connecting to the
Internet through America On-Line.
 SLIP/PPP connection requires using a modem and several types of
software like TCP/IP, Serial Line Internet Protocol (SLIP) or Point to
Point Protocol (PPP) to connect to an Internet host. An example would
be connecting to the CSUS server from home.
 Network connection is the highest and most expensive level of
connectivity. This approach requires using a network adapter card and
a communications stack directly connected to an Internet server. An
example would be connecting to the Internet when you use a PC in the
computer labs at CSUS.
Internet Services - I
 E-mail: sends text, sound, and images to others.
 Telnet: logs on to another computer and access its public
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files.
FTP: copies a file between two computers.
Usenet and newsgroup: an on-line discussion group of a
specific topic.
Chat rooms: enables tow or more person to carry on online text conversation in real time.
Internet phone: enables voice communication between two
person with proper hardware and software.
Internet video conferencing: supports simultaneous voice
and visual communications.
Internet Services - II
 Content streaming: continuously transfers and plays
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multimedia files over the Internet between two locations.
Instant messaging: allows two or more person to
communicates instantly on the Internet,
Shopping on the Web: allows people to purchase products
and services over the Internet.
Web auctions: lets people bid on products and services.
Music, radio, and video on the Internet: lets user play or
download music, radio, and video.
Office on the Web: allows people to access files and
information through a Web site.
Internet sites in 3-D: views products and images at a
different angles.
Internet Services - III
 Free software and services: allows people to obtain free
software, advice, and information on the Internet.
Basic Internet Software
Servers over the Internet that offer different services like email and web services. Several types of software are
needed to access those services. The most significant types
of software that you need are:
– Web Browsing Software
– Telnet Software
– FTP Software
Telnet Software
 Telnet is a user command used to access a remote
computer. Telnet software enables the user to log on to
another computer and access any applications and data to
which the user has been granted access.
FTP Software
 A file transfer protocol (FTP) program is used to download
a file from the host computer to the PC or vice versa. FTP
clients with graphical interfaces allow you to drag and drop
files from an FTP site to a local computer.
The World Wide Web
 The World Wide Web, uses the client/server model, to organize Internet
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resources into a series of menu pages (screens) that appear on your
computer.
Data can exist on the Web in any computer file like word processing
files, graphic images, video and audio files.
Hypertext Markup Language (HTML) is the standard page description
language for Web pages. HTML documents contain Uniform Resource
Locators (URLs) which is a standard way of coding the hypertext links
to other documents on the Web.
Web browsers, like Netscape Communicator and Internet Explorer, are
software applications that request a page from the Web server and
display it on the user’s local computer. They receive HTML documents
by using a Uniform Resource Locator (URL), which is the address of
the file accessible on the WWW.
Browsers must be able to understand and interpret hypertext markup
language (HTML) codes in the HTML documents.
Intranets and Extranets
 An Intranet is an internal corporate network built using the
Internet and W3 standards and products. One of the
intranet’s most obvious virtues is its ability to slash the
need of paper. Any employee can view the same electronic
information.
 An Extranet is a network based on Web technologies that
links selected resources of the intranet of a company with
its customers, suppliers, or other business partners
Privacy and Security
 Cookie and fraud
 Cryptography is the process of converting a message into a secret code
and changing the encoded message back to regular text.
 Encryption is the original conversion of a message into a secret code.
Decryption is the encrypted message conversion back to regular text.
 Digital Signature is an encryption technique used to meet the critical
need for processing on-line financial transactions.
 Firewalls are devices that sit between the internal network and the
outside Internet and limit access into and out of the internal network.
Virtual Private Network (VPN)
A secure connection between two computers across the Internet
Points to Remember
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What is the Internet
IP Addresses
How the Internet Works
The Domain Name System (DNS)
How E-mail Finds its Way
Internet Communication Protocols
How to Connect to the Internet
Internet Services
Basic Internet Software
Telnet Software
FTP Software
The World Wide Web
Intranets and Extranets
Virtual Private Networks
Privacy and Security