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- Inside the Internet
and the Web
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- The Internet is an interconnected network of thousands of networks
linking academic, research, government, and commercial institutions.
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- The Internet provides scientists, engineers, educators, students,
business people, and others with a variety of services such as:
- Electronic mail (send/receive mail messages)
- Remote login (Telnet - access to other computers)
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- Transferring files (FTP - accessing archives of data)
- Newsgroups (Usenet - on-line public discussions)
- World Wide Web (a collection of multimedia documents)
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- Today, the Internet connects computers to about every country in the
world. However, the Internet is:
- growing too fast to measure its growth
- too decentralized to quantify
- a network with no hard boundaries
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- The language at the heart of the Internet is TCP/IP…
- Transmission Control
Protocol/Internet Protocol
- Allows cross-network
communication
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- TCP breaks messages into packets
- Each packet has all the information needed to travel from network to
network
- Host systems called Routers determine how to route transmissions
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- IP is the address for the packets
- Each Internet host computer has a unique IP Address
- Each address is comprised of four sets of numbers separated by periods,
such as 123.23.168.22
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- Direct (dedicated) Connection
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- Dialup Connections
- limited connection using a modem
- Full access dial up uses SLIP or PPP via modem
- Broadband Connections
- DSL service is newer, faster, and
cheaper than ISDN
- Can share phone line with voice
traffic
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- Cable Modem Connection
- allow Internet connections using shared TV cables
- can exceed DSL speeds
- Carry increased privacy and security risks
- Satellite Connections
- provides connections using DirecTV satellite dishes
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- Internet Service Providers
(ISPs)
- local ISPs provide connections through
local telephone lines
- national ISPs offer connections on a nationwide scale
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- Intranets - self-contained intra-organizational networks designed using
the same technology as the Internet
- Firewalls - used to prevent unauthorized communication and secure
sensitive internal data
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- A typical Intranets include:
- E-mail
- Newsgroups
- File transfer
- Web publishing
- Other services
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- Extranets: designed for outside use by customers, clients, and business
partners
- Electronic Commerce: business transactions through electronic networks
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- Electronic data interchange (EDI): a decade-old set of specifications
for ordering, billing, and paying for parts and services over private
networks.
- Virtual private networks: not subject to the traffic and security
problems.
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- The user interface varies depending on which client/server application
is being used.
- UNIX - developed by Bell Labs, allows a timesharing computer to
communicate with several other computers or terminals at once.
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- E-mail addresses are made up
of two parts separated by an
at(@) sign:
- User name@host name
- Example: johnsmith@mindspring.com
- The host is named using DNS (domain name system), which translates IP
addresses into a string of names.
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- An Internet address includes: username@hostname.sub.dom
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- Top level domains include:
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- What appears on the screen depends on the type of Internet connection
and
mail program you use
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- Why are free e-mail accounts
made available?
- often offered to attract Web site visitors
- available for users of public computers
- sensible for those wanting multiple e-mail addresses not associated
with a workplace
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- E-mail Formats include:
- ASCII text so they can be viewed with any client program
- MIME that can be used to send and receive text with enriched text or HTML
(displays text formatting, graphics, and links to Web pages)
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- Mailing lists allow you to participate in email discussion groups on
special-interest topics.
- Network News are public discussions that you can go in and out as you
please.
- Messages are posted on virtual bulletin boards (for everyone to read).
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- Internet relay chat (IRC) allows several users to chat simultaneously
- Internet Telephony turns the Internet into a toll-free long-distance
telephone service
- Video teleconferences allow multi-person videoconferences via the Web
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- Information gathering
- Telnet - makes remote login possible
- FTP (file transfer protocol) - allows
files to be uploaded and downloaded from remote computers
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- Web browsers locate and transfer files without typing commands
- When you click a Web link to download a file, you’re probably using FTP
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- WWW is a distributed browsing and searching system developed at CERN
- System was designed to give Internet documents unique addresses
- HTML language was created for encoding and displaying documents
- Browser software was built for viewing documents from remote locations
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- Web pages are made up of text and images
- A Web site is a collection of web pages
- A Home page is the main entry to a Web site
- A Web browser like Netscape Communicator or Internet Explorer allows you
to explore the Web by clicking links
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- Search engines
- produce a list of pages that match a keyword
- they are built around a database that catalogs
Web locations based on content
- Directory or Subject Tree
- A hierarchical catalog of Web sites
- Natural Language Search Engines
- Allows users to ask for what they want
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- Search engines help find
information when you
type a query using
keywords.
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- Directory/subject tree
engines offer a menu
of
subject choices
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- Ask questions in a Natural
Language Search Engine
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- Portals offer quick and easy
access to a variety
of services such as e-mail, chat,maps,
news,
shopping, etc.
- Examples of consumer portals
include
- Yahoo!, Excite, Lycos, Alta Vista, Netscape Netcenter, Snap
- Specialized portals target specific industries and economic sectors
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- Tables
- Frames
- Forms
- Downloadable
audio and video
- Streaming audio and video
- Real-time live
audio or video
- 3-D environments
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- Plug-Ins are software extensions that add new features. Examples
include…
- QuickTime
- Shockwave/Flash
- RealPlayer
- Acrobat
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- Client computers pull information
- Browsers initiate a request for information
- Push technology delivers information automatically to the client
computer
- Up to the minute weather reports
- News headlines
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- An HTML document includes codes that determines the format, layout, and
structure of a Web document
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- This text coded as HTML …
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- Dynamic HTML:
- adds more programming power to HTML by allowing code to automatically
modify itself under certain circumstances
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- provides faster network communications for universities and research
institutions
- virtual laboratories, digital libraries, and distance learning
applications are being built on Internet 2
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- Filtering software can prevent unwanted and inappropriate content
- Encryption prevents credit card and e-mail forgery
- Digital cash makes on-line transactions safer
- Universal access is a problem
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- A blurring of Web and interpersonal communication applications
- Internet appliances connected to the Web
- Continued computer crime and security issues
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Notes
