Unit 5' Network Systems

1
Unit 5. Network Systems
2
Network Systems

• Reading Sequence
• 5.1 Internet Basics
• 5.2 Local and Wide Area Networks
• 5.3 Communication Strategies
• 5.4 Data Transfer Technologies
• 5.5 Internet Architecture

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Network Internet

• A communications network is the combination of
  hardware, software, and connecting links that
  transport data.
• The Internet refers to a global, public network
  that uses TCP/IP protocol and includes servers
  that handle e-mail, Web sites, file downloads,
  and so on.

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Network Topology
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5.1 Internet Basics

• In a short period of time, the Internet has
  become essential to how people and businesses
  communicate with each other around the world.
  Using a browser and email are important skills
  today. This section provides some general
  background on the Internet and helps you become
  more familiar with the features of your browser
  and email programs.

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The World Wide Web

• Introduce the World Wide Web and its workings.
• Using the Web
• What's in the Web?
• Introduction to HTML Forms and Servlets

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Using the Web

• Surfing the Web
• Your Web Pages
• Clients, Servers, and URLs
• Searching the Web
• Commerce on the Web
• Some Ethical Considerations

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Surfing the Web

• Internet
• World Wide Web
• Surfing
• Internet Service Provider ( ISP )

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Internet

• Internet is a computer network that connects
  millions of computers across a number of
  countries.
• There is no central authority that controls the
  Internet different organizations own different
  pieces of it.
• The Internet was originally conceived of by the
  Advanced Research Project Agency (ARPA) of the
  U.S. government in the 1960s.

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Word Wide Web

• the Web, WWW or W3
• Portion of the computers on the Internet that can
  communicate with each other using a
  computer-network protocol called HTTP (Hypertext
  Transfer Protocol ).
• All browsers use HTTP to request and receive Web
  pages from other computers.

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Surfing

• Browse on the Web
• page, place, site, web site
• Locations on the Web that you can visit and view
  through a browser
• homepage
• No one can certify that information presented on
  the Web is accurate, correct, and up-to-date.

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Internet Service Provider ( ISP )

• An ISP is any one of a number of companies that
  enable people not only to connect to the Internet
  and surf the Web but also to publish Web pages.
• All Web sites must have unique names or
  addressesone per machine

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Browse Sample
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(No Transcript)
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Clients, Servers

• Clients, Servers
• A client application requests information from a
  server application or asks the server to perform
  some task.
• Client asks for service.
• Server provides the service.

The site that supplies the information is
considered a server.
The browser is considered a client.
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Clients, Servers

• Server applications are typically run on powerful
  computers, since they need to be able to service
  concurrent requests from a number of clients.
• Client applications are typically run on less
  powerful computers, such as PCs or workstations.

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(No Transcript)
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URLs

• Uniform Resource Locator naming scheme
• Provides user with a way to access Web resources
  using a uniform means for addressing resources.

protocol//name of machinename of resource
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URLs (Cont)

• protocol//name of machinename of resource
• ex http // www.icarnegie.com/courses.html

• ftp // www.icarnegie.com/index.htm
• http//202.114.35.66

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Basic Work Model

• Client sends a request for a resource
• A protocol (How do I get the resource?).
• The server (What server has this resource?).
• The resource itself (What resource
  specifically?).
• Server
• Locates the resource requested.
• Transmits a copy of the resource back to the
  client using the specified protocol.

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Browse Sample
Dynamic Web Content extend the basic
client-server model
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Searching the Web

• Browsing and searching
• Search engine is a program that allows one to
  search for keywords in files at one or more
  Internet sites.
• Excite www.excite.com
• AltaVista www.altavista.com
• Lycos www.lycos.com
• Google www.google.com

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How to search

• Use a search site
• Type key words of your search into the search
  engine
• Search.
• Use the help information offered by each search
  engine.

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A search Sample
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(No Transcript)
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Searching the Web (Cont)

• Tow types of Search Sites
• Sites that feature a search engine
• Sites of this type maintain indexes or databases
  of the addresses of virtually all of the pages
  and documents on the Web. These indexes and
  databases are updated regularly and automatically
  by programs known as "spiders, crawler

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Searching the Web (Cont)

• Tow types of Search Sites
• Sites that feature a Web directory
• it organizes information available on the Web
  into different categories and subcategories.

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Search Engine

• Full Text Search Engine
• Google, Fast/AllTheWeb, AltaVista, Inktomi,
  WiseNut, Teoma, Baidu, Lycos
• Search index/Directory
• Yahoo, LookSmart, ??, ??, ??
• Meta Search Engine
• InforSpace, Dogpile, Vivisimo, ??

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Commerce on the Web

• Web-based Internet commerce
• Internet Service Providers (ISPs)
• sell you access to the Internet
• Advertising
• Commercial Transactions

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(No Transcript)
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Some Ethical Considerations

• Can you go to your favorite sports team's Web
  page, make a copy of the .jpeg or .gif file that
  is their logo and put that logo on your Web page?
  
• Can you put a link on your page to the home page
  of your favorite sports team?

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Internet Languages

• HTML
• XML
• JavaScript
• Java

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HTML

• HTML stands for Hyper Text Markup Language. An
  HTML file is a text file containing a set of
  predefined tags that are used to specify how data
  should be displayed in a browser or another
  application program. For example, inserting the
  built-in tag "ltigt" and "lt/igt" around a phrase
  would italicized the phrase displayed. Because
  HTML is composed of text, you can create an HTML
  file using a text editor. To enable the Web
  browser to interpret how you want the page to be
  displayed, you must save the file with an "htm"
  or "html" file extension. Note that "lt" and "gt"
  indicates the beginning and end of a tag,
  respectively.

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HTML example

• 1. Open a text editor application such as
  Notepad.exe.
• 2. Copy the following text and paste it into the
  text editor program
• lthtmlgtltheadgtlttitlegtPage titlelt/titlegtlt/headgtltb
  odygtThis is an example of a Web page. ltbgtA tag
  is used to make this text appear
  bold.lt/bgtlt/bodygtlt/htmlgt
• 3. Save the file on Desktop as "sample.html".
• 4. Open a Web browser application.

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XML

• XML (eXtensible Markup Language).
• Differences between HTML and XML
• HTML tags are primarily concerned with how text
  should be displayed, XML tags can be used to
  describe what a piece of text means.
• There are no predefined tags in XML. Users have
  the freedom to define their own tags.
• For example, ltphonegt4125551212lt/phonegt

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JavaScript

• JavaScript is a "scripting language," which means
  the instructions the programmer writes are not
  compiled in advance. Instead, they are
  interpreted by an application when the script is
  run by the computer.

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JavaScript example

• lthtmlgt  ltheadgt    lttitlegtJavaScript
  Demonstrationlt/titlegt    ltscript
  type"text/javascript" language"JavaScript1.2"gt 
       function display()         document.body.bg
  Color "black"        var ln1 "Hello
  World!"        var ln2 "This is the "
  document.title " page."        var str
  ln1.fontcolor("lime") "ltbr /gt"
  ln2.fontcolor("red")        document.writeln(st
  r)          lt/scriptgt  lt/headgt  ltbodygt    lt
  script type"text/javascript" language"JavaScript
  1.2"gt      display()    lt/scriptgt  lt/bodygtlt/h
  tmlgt

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Java

• Java is a high-level programming language that
  was developed by Sun Microsystems and has become
  a popular programming tool for web-based
  projects. Small Java applications are called Java
  applets.

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Java example

• import java.applet.Appletimport
  java.awt.Graphicspublic class Demonstration
  extends Applet   public void paint(Graphics g)
      g.drawRoundRect(5, 5, 100, 50, 10,
  10)    g.drawString("Hello World!", 23,
  35)  

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5.2 Local and Wide Area Networks

• Reading Sequence
• Textbook, Subsection "Internet Resources" in
  Section 1B.
• Textbook, Section 5B.
• Textbook, Section 5D.

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Network Classifications

• An internetwork, or internet, is a network that
  is composed of many smaller networks.

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Network Classifications

• Intranet Intra???????,????????,????????????
  ?????,????????????????,Intranet?????????,???????
  ?,?Intranet?????Internet?????????,??WWW???????????
  ???????,??????Internet?????

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Network Classifications

• LAN (Local Area Network???)?????????????,???PC???
  ???????????????????
• WAN (Wide Area Network???)?????????????,?????????
  ?????????????????????????????????????????????,????
  ???,????,??????,?????????????

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Network Classifications

• MAN (Metropolitan Area Network,???)
  ???????????????????,???80km???80???,?LAN??????????
  
• Wireless network????,??????????????????????,?????
  ???????,???????????????

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5.3 Communication Strategies

• Read
• 5.3.1 Client-Server Framework. Learning Goal
  Understanding thin and thick clients.
• 5.3.2 Peer-to-Peer Connectivity. Learning Goal
  Understanding how each machine is both a client
  and a server, and what impact this has on
  computing.

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client-server systems

• Many network applications are organized as
  client-server systems. The client runs on the
  user's computer and interacts with both the user
  and the server.
• The server can accept requests from any number of
  clients. It performs some service for them and
  returns the results.

47
Clients, Servers

• Clients, Servers
• A client application requests information from a
  server application or asks the server to perform
  some task.
• Client asks for service.
• Server provides the service.

The site that supplies the information is
considered a server.
The browser is considered a client.
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Example

• World Wide Web The client is the Web browser
  program. For a machine to host a Web site, it
  must run a Web server program that clients can
  talk to.
• Email Microsoft Outlook, is the client. The
  server is a program that accepts and stores
  incoming mail for users, and delivers the mail to
  them when their client requests it. Servers can
  also forward mail to other servers if necessary.

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Clients, Servers

• Server applications are typically run on powerful
  computers, since they need to be able to service
  concurrent requests from a number of clients.
• Client applications are typically run on less
  powerful computers, such as PCs or workstations.

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client-server systems

• thick clients thin clients.
• based on how much work is done on the client
  side a thin client does relatively little work.
  A thick client carries out a substantial portion
  of the overall work of the system.
• Web surfing use, the browser acts as a thin
  client, while the work of searching a database
  and organizing the results is carried out by
  servers.
• a system might download a Java applet to the
  browser, and that applet might act as a thick
  client.

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Peer-to-Peer Connectivity

• Peer-to-peer (P2P). Instead of having a central
  server that all clients communicate with, every
  member of a peer-to-peer network can communicate
  with any other member.
• E.g.a multi-player network game Napster,
  emule

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Client/server Peer-to-peer
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5.4 Data Transfer Technologies

• Reading Sequence
• Textbook, Section 5A.
• Textbook, Section 5C.
• Domain Name Service URL
• OSI Layers
• TCP/IP Protocols

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55
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What is a URL?

• Every Web page has a unique address called a URL
  (Uniform resource locator??????? ).
• Most URLs begin with http//

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????????????(OSI/RM)

• ???????(International Standards
  Organization--ISO)???????,??????????(?DNA?SNA?)???
  ?,?????????????(Open Systems Interconnection
  Reference ModelOSI/RM)????????
• ???????
• ???????
• ???????
• ?,??????
• ????????
• ????????
• ???????

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IP??? IP??
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protocol??

• ???????,??(protocol,????)?????????????????????????
  ?????????????????????????????????????????
• ??????????????????????????????????????????
• ???????????????????

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????????

• ??????
• (1)???????????????
• (2)?????????????,??????????????
• (3)???????????????

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IP/TCP

• ??????????,???????????? IP ? TCP?
• ???????????? IP ??????????????? TCP ??????
• ??? TCP/IP ???????? TCP ? IP ????????

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????????IP ? TCP
???
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IP Protocol

• ???? IP ?????,???????????????????????????
• IP ? Internet Protocol ???,????????????
• ?? IP ??????????
• IP ???IP ??
• ? IP ??????????
• IP ???IP ??? (IP datagram)?

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TCP Protocol

• TCP ? Transmission Control Protocol
  ???,????????????
• TCP ???????????,??????????????????????

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TCP Protocol

• TCP ???????????????????
• ??????????????????????
• ????????????????????,?????????
• ???????????,TCP ??????????????????????

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HTTP (HyperText Transfer Protocol)

• HTTP (hypertext Transfer Protocol??????? ) is the
  communications standard thats instrumental in
  ferrying Web documents to all corners of the
  Internet.
• ??????????????????????????? HTTP

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Email

• ???????????????
• ?????????????????????
• ??????????????????????

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????????????????? SMTP (Simple Mail Transfer
Protocol)
???????????????3 POP3 (Post Office Protocol
version 3)
sina.com
mail.cctv.com
??? ISP
??? ISP
???
?? SMTP ??
?? POP3 ??
???
?? SMTP ??
???
????
????
?????
?????
?????xyz5678_at_sina.com
?????ab30_at_mail.cctv.com
?????????? IP ? TCP ??
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MIME Types

• It is possible to attach images and other types
  of documents to an email message. This raises a
  problem how is the mail client supposed to know
  what to do with these documents?
• The solution is to give each attachment a label
  explaining what kind of document it is. The
  labels are called MIME types (the acronym for
  Multipurpose Internet Mail Extension??????????).

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??????????

• ??
• ??
• ??
• ??????????
• ??
• ???????????
• ???????????

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Exercise 5

• Question1. XML and HTML
• One necessary component to facilitate electronic
  commerce is the capability to exchange data over
  varying systems. In this section, you will
  strengthen your knowledge of XML as a portable
  language that enables data to be handled by any
  computer system.
• a. What does the term XML stand for? What is
  the function of XML tags, and how does the
  function of XML tags differ from the function of
  HTML tags?
• b. Contrast the flexibility of using XML tags and
  HTML tags.

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Exercise 5

• c. What is one reason why storing data in XML may
  be preferred to enable multiple systems to
  exchange data?
• Download and save Movies100EX.xml and
  display.html on your Desktop.
• Open Movies100EX.xml using Notepad.exe to see the
  content of the XML file.

73
Exercise 5

• f. For the movie titled, Top Gun, list the
  followingYear Score
• Open display.html using Notepad.exe to see the
  content of the HTML file. Note that the
  references used to embed the xml file are
  highlighted in bold font below
• lthtmlgtltbodygtltxml id"movies" src"Movies100EX.xm
  l"gtlt/xmlgtThis is a nice use of non-standard
  HTML. Do we really want to use IE only items.
  Also, since it is non-standard will the students
  have gained the knowledge necessary to answer
  this question?lttable border"1"
  datasrc"movies"gtlttrgtlttdgtltspan
  datafld"Title"gtlt/spangtlt/tdgtlttdgtltspan
  datafld"Year"gtlt/spangtlt/tdgtlttdgtltspan
  datafld"Score"gtlt/spangtlt/tdgtlt/trgtlt/tablegtlt/body
  gtlt/htmlgt

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Exercise 5

• Drag and drop display.html into an Internet
  Explorer window to see how it is displayed.
• g. Generate another HTML file that displays
  additional data fields from the XML file, listing
  Movie_id, Title, Year, Score, and Votes. Save the
  HTML file as, myXML.html. Copy and paste your
  HTML code.
• h. Use Internet Explorer to display myXML.html.
  Copy the screen shot of this file showing 20
  movie entries and paste the screen shot into your
  assignment submission.
• Delete Movies100EX.xml, display.html, and
  myXML.html from Desktop.

75
Exercise 5

• Question 2 Network Failure
• In addition to Tracert, other network tools such
  as IPconfig and Ping can be used to troubleshoot
  network issues.
• You can use ipconfig command to see whether your
  computer is connected to the Internet.
• Pull up the command console. Type ipconfig
  /all.

76
Exercise 5

• a. Are you connected to the Internet? Paste the
  screenshot showing the result of the command,
  ipconfig.
• b. What is your IP address?
• c. What are the IP addresses of your DNS servers?
  
• You can use Ping to test the response of the
  destination server.
• d. First, launch the Windows Command Console.
  Type, ping www.yahoo.com. Copy and paste the
  screenshot of the Ping command.
• e. Did you get a response from the target server?
  
• f. List two possible explanation(s) for the
  result of the Ping command below

77
Exercise 5

• Figure 2 Ping Result