internet concepts all

1

Introduction to Computers and the Internet

Outline Introduction History of the Internet Personal Computing History of the World Wide Web

Hardware Trends Key Software Trend: Object Technology JavaScript: Object-Based Scripting for the Web C and C++ Java

2

History of the Internet

• ARPANET– Implemented in late 1960’s by ARPA (Advanced Research

Projects Agency of DOD)

– Networked computer systems of a dozen universities and institutions with 56KB communications lines

– Grandparent of today’s Internet

– Intended to allow computers to be shared

3


• ARPA’s goals– Allow multiple users to send and receive info at same time

– Network operated packet switching technique• Digital data sent in small packages called packets

• Packets contained data, address info, error-control info and sequencing info

• Greatly reduced transmission costs of dedicated communications lines

– Network designed to be operated without centralized control• If portion of network fails, remaining portions still able to route

packets

4


• Transmission Control Protocol (TCP)– Name of protocols for communicating over ARPAnet

– Ensured that messages were properly routed and that they arrived intact

• Organizations implemented own networks– Used both for intra-organization and communication

5


• Huge variety of networking hardware and software appeared– ARPA achieved inter-communication between all platforms with

development of the IP• Internetworking Protocol

• Current architecture of Internet

– Combined set of protocols called TCP/IP

• The Internet– Limited to universities and research institutions

– Military became big user

– Next, government decided to access Internet for commercial purposes

6


• Internet traffic grew– Businesses spent heavily to improve Internet

• Better service their clients

– Fierce competition among communications carriers and hardware and software suppliers

– Result• Bandwidth (info carrying capacity) of Internet increased

tremendously

• Costs plummeted

7

Personal Computing

• Computers today– As powerful as million dollar machines from 20 years ago

– Workstations• Most powerful desktops today

• Provide users with enormous capabilities

– Information easily shared over networks• Networks controlled by servers

– Common programs and data used by client computers

– Popular operating systems• UNIX, Mac OS X, Windows, Windows NT, Linux

8

History of the World Wide Web

• WWW– Allows computer users to locate and view multimedia-based

documents

– Introduced in 1990 by Tim Berners-Lee

• Internet today– Mixes computing and communications technologies

– Makes information constantly and instantly available to anyone with a connection

9

The Key Software Trend: Object Technology

• Objects– Reusable software components that model items in the real

world

– Makes software developers more productive

– Object-oriented programs often easier to understand, correct and modify than older types of programs

10

The Key Software Trend: Object Technology

• Object technology

– C++, developed in 1980s, based on two languages• C – Developed to implement the UNIX OS in early 1970’s

• Simula 67 – Simulation programming language from 1967

11

JavaScript: Object-BasedScripting for the Web

• JavaScript

– Attractive package for advancing level of programming language education

– Object-based language

– Supports proper software engineering techniques

12

C and C++

• History of C and C++– Evolved from B language (developed by Dennis Ritchie)

– C Implemented in 1972 as contemporary of Pascal• C++ developed by Bjarne Stroustrup in 1980s

• C++ Initially used in Unix, today used in virtually all new operating systems

• Advantages of C++– Extends C programming into object orientation

– Older C code may be integrated into C++

13

Java

• History of Java– Project Green (1991): developed C based language (later

called Java) for intelligent consumer electronic devices• Advanced by World Wide Web explosion in 1993: potential to

create Web pages with dynamic content

• Java introduced in May of 1995

• Advantages of Java– Allows Web pages with dynamic and interactive content

– Allows Large-scale enterprise applications

– Enhances Web Servers

– Now one of most widely implemented languages in world

14

Microsoft .NET

• .NET initiative– June 2000

– Use multiple programming languages in same project

– Internet and Web development• ASP.NET allows complex Web-based client-server

applications

• Brings software reuse to Web

15

Dynamic HTML

• DHTML– Two versions

• Microsoft

• Netscape

– Consists of number of technologies freely available for download

– Used for developing high-performance, Web-based applications

• Much of application’s work performed directly on client rather than on server or Internet

16

Microsoft Internet Explorer 6

OutlineIntroduction to the Internet Explorer 6 Web

Browser Connecting to the Internet Internet Explorer 6 Features Searching the Internet Online Help and Tutorials Keeping Track of Favorite Sites File Transfer Protocol (FTP) Electronic Mail Instant Messaging

Other Web Browsers

17

Objectives

• In this tutorial, you will learn:– To become familiar with the Microsoft Internet Explorer 6

(IE6) Web browser’s capabilities.

– To be able to use IE6 to search the “world of information” available on the World Wide Web.

– To be able to use the Internet as an information tool.

– To become familiar with e-mail.

– To learn about instant messaging.

– To become aware of the differences between various browsers.

18

Introduction

• Internet– Medium for communication and interaction

– Web Browsers• Software that allows users to view Web content

– Microsoft Internet Explorer

– Netscape Navigator

– Others

19

Connecting to the Internet

• Computer hardware– Computer hardware

• Modem

– Transmits data over phone lines

• Network card (NIC)

• Internet Service Provider (ISP)– Commercial

• AOL (www.aol.com)

• Microsoft Network (join.msn.com)

• NetZero (www.netzero.com)

20


• Internet Service Provider (ISP), cont.– Considerations

• Cost

• Bandwidth

– Amount of data transferred through communications medium in a fixed amount of time

– Broadband• Constantly connected

• 100’s of kbps (kilo-bits per second)

• DSL (Digital Subscriber Line)

– Uses existing phone lines

– Requires DSL modem

21


• Internet Service Provider (ISP), cont.– Broadband, cont.

• Cable Modem

– Use cable television lines

– Requires cable modem

• ISDN (Integrated Services Digital Network)

– Uses digital or standard telephone lines

– Requires a terminal adaptor

– Dial-up connection• Uses existing phone lines

• Interferes with phone use

• Must dial-up with modem.

• Usually 56 kbps (kilo-bits per second)

22


• Internet Connection Wizard– Use this application to configure computer’s Internet

connection.– Start > Programs > Accessories > Communications >

Internet Connection Wizard

• Tutorial available on Windows 2000

23

Connecting to the InternetFig. 2.1 Internet Connection Wizard helps configure Internet access.

Tutorial button

Specify what type of connection to use by clicking one of the option buttons

24

Internet Explorer 6 Features

• Web browser– Program which displays Internet content

• Microsoft Internet Explorer 6

• Netscape 7.1

– URL (Uniform/Universal Resource Locator)• Web page address

– HTTP (hyper-text transfer protocol)

• Protocol for transferring data over the Internet

• Type in Address field

– Hyperlinks• Graphical or textual elements

– Click to link to another Web page

– Loads new page into browser window

25


• Web browser, cont.– History

• Lists recently visited Web sites

• Forward/Back buttons

• Refresh button

• History button

– Divides window and lists recently-visited sites on left

26

Internet Explorer 6 FeaturesFig. 2.2 Deitel Website.

Back

Recent historyForwardStop Refresh Address bar

Go

Pointer (over a hyperlink)

Scroll bars

27

Internet Explorer 6 FeaturesFig. 2.3 The History menu lists previously visited Web sites.

Interactive History window

History date options

Site from folder

Web site folder

Click and drag here to resize

Content window

28


• Web browser, cont.– Autocomplete

• Completes Web address as it is being typed

• Completes form information as it is being typed

– File options• Save Web page for off-line use

– File > Save As• Save pictures from a Web site

– Right click image

• Choose Save Picture As…

29

Internet Explorer 6 FeaturesFig. 2.4 AutoComplete suggests possible URLs when given a partial address.

Partial address

URLs

30

Internet Explorer 6 FeaturesFig. 2.5 Saving a picture from a Web site.

31

Searching the Internet

• Search engines– Web sites that sort through by keywords and categories

• Google (www.google.com)• Yahoo! (www.yahoo.com)• Lycos (www.lycos.com)• Altavista (www.altavista.com)

– Store information in databases– Returns list of sites as hyperlinks

• Meta-search engines– Do not maintain databases– Aggregate results from multiple search engines– Microsoft Network (www.msn.com)

• Click Search button in toolbar

– MetaCrawler (www.metacrawler.com)

32

Online Help and TutorialsFig. 2.6 Searching the Internet with IE6.

New searchSearch window

Search categories

Search words

Search button

Toolbar

33

Online Help and Tutorials

• IE 6 built-in help feature– Help > Tour

• Overview of IE 6

– Help > Contents and Index• Search for help on specific topic

34

Online Help and TutorialsFig. 2.7 IE6 Help dialog.

Help menu

Categories

35

Keeping Track of Favorite Sites

• Favorites– List organizes frequently-visited sites

– Add sites to list• Favorites > Add to Favorites…

– Organize list• Favorites > Organize Favorites…

36

Keeping Track of Favorite Sites

Fig. 2.8 Favorites menu helps organize frequently visited Web sites.

Add/Organize Favorites

Favorites

Favorites window

Site information

Organize Favorites dialog

37

File Transfer Protocol (FTP)

• Downloading– Transfer files from remote servers over the Internet to a local

computer• Usually applications, browser plug-ins or files

• Plug-ins

– Applications which work with Web browsers to add functionality

• Shockwave (www.shockwave.com)

• Adobe Acrobat (www.adobe.com)

– Use FTP (File Transfer Protocol)• ftp://• FTP site

– May require login and password

– Right click file in FTP directory and copy to hard drive

38

File Transfer Protocol (FTP)Fig. 2.9 FTP site access in IE6.

FTP address

Folders in the FTP directoryFile

Login window

39

Electronic Mail

• E-mail (electronic mail)– Delivers formatted messages over Internet

– E-mail address• username@domainname

– Email Programs• Eudora

• Pegasus

• Outlook Express

– Free email accounts• Hotmail (www.hotmail.com)

• Yahoo! (mail.yahoo.com)

40

Electronic Mail

• E-mail (electronic mail), cont.– Post Office Protocol (POP)

• Remote server

• Download to local client

• E-mail scattered

– Internet Message Access Protocol (IMAP)• Manipulate messages directly on server

• Access all your e-mail from any machine

– Simple Mail Transfer Protocol (SMTP)• Used to send e-mail

41

Instant MessagingFig. 2.11 Outlook Express e-mail main screen..

Message list

Address book

Preview pane

Mailboxes

Message toolbar items

42

Instant Messaging

• Instant Messaging– Communicate (“chat”) in real time

– Send audio, video and files

– Several popular services• AOL Instant Messenger (www.aim.com)

• Yahoo! Messenger (messenger.yahoo.com)

• ICQ (web.icq.com)

• MSN Messenger (messenger.msn.com)

– Trillian (www.trillian.cc)• Able to communicate with all of the above

43

Instant Messaging

• Instant Messaging– Communicate (“chat”) in real time

– Send audio, video and files

– Several popular services• AOL Instant Messenger (www.aim.com)

• Yahoo! Messenger (messenger.yahoo.com)

• ICQ (web.icq.com)

• MSN Messenger (messenger.msn.com)

– Trillian (www.trillian.cc)• Able to communicate with all of the above

44

Instant Messaging

• Instant Messaging, cont.– Some instant messaging tools designed for collaboration

• NetMeeting

• Windows Messenger

• Include whiteboard feature to share drawings

– Screen name• Unique identifier

– Buddy List• Maintains list of screen names

45

Instant MessagingFig. 2.12 Buddy list and an instant message.

Buddy list

Instant message

46

Other Browsers

• Alternatives to Internet Explorer and Netscape– Offer new/different features and layout engines

• Mozilla (www.mozilla.org)

– Uses Gecko layout engine, basis for Netscape 7.1

• Opera (www.opera.com)

– Lightweight

• Amaya (www.w3.org/Amaya)

– Browser/editor

– Demonstrates W3C standards

– Each layout engine displays websites differently• Testing on multiple browsers important

47

Other BrowsersFig. 2.13 Mozilla web browser.

48

SMTPandFTP

49

26.1 Electronic Mail26.1 Electronic Mail

Sending/Receiving Mail

Addresses

User Agent

MIME

Mail Transfer Agent

Mail Access Protocols

50Figure 26.2 Email address

51Figure 26.3 User agent

52Figure 26.4 MIME

53Figure 26.5 MIME header

54Table 26.1Table 26.1 Data types and subtypes in MIMEData types and subtypes in MIME

Type Subtype Description

Text Plain Unformatted text

Multiport

Mixed Body contains ordered parts of different data types

Parallel Same as above, but no order

Digest Similar to mixed, but the default is message/RFC822

Alternative Parts are different versions of the same message

Message

RFC822 Body is an encapsulated message

Partial Body is a fragment of a bigger message

Ext. Body Body is a reference to another message

ImageJPEG Image is in JPEG

GIF Video is in GIF format

Video MPEG Video is in MPEG format

Audio Basic Single-channel encoding of voice at 8 KHz

ApplicationPostScript Adobe PostScript

Octet-Stream General binary data (8-bit bytes)

55

Table 26.2 Table 26.2 Content-transfer encodingContent-transfer encoding

Category Description

Type ASCII characters and short lines

7bit Non-ASCII characters and short lines

8bit Non-ASCII characters with unlimited-length lines

Binary 6-bit blocks of data are encoded into 8-bit ASCII characters

Base64 Non-ASCII characters are encoded as an equal sign followed by an ASCII code

56Figure 26. 6 Base64

57

Table 26.3 Table 26.3 Base64 encoding tableBase64 encoding table

Value Code Value Code Value Code Value Code Value Code Value Code

0 A 11 L 22 W 33 h 44 s 55 3

1 B 12 M 23 X 34 i 45 t 56 4

2 C 13 N 24 Y 35 j 46 u 57 5

3 D 14 O 25 Z 36 k 47 v 58 6

4 E 15 P 26 a 37 l 48 w 59 7

5 F 16 Q 27 b 38 m 49 x 60 8

6 G 17 R 28 c 39 n 50 y 61 9

7 H 18 S 29 d 40 o 51 z 62 +

8 I 19 T 30 e 41 p 52 0 63 /

9 J 20 U 31 f 42 q 53 1

10 K 21 V 32 g 43 r 54 2

58Figure 26.7 Quoted-printable

59Figure 26.8 MTA client and server

60Figure 26.9 Commands and responses

61Figure 26.10 Email delivery

62Figure 26.11 POP3

63

26.2 File Transfer 26.2 File Transfer

Connections

Communication

File Transfer

User Interface

Anonymous

64Figure 26.12 FTP

65Figure 26.13 Using the control connection

66Figure 26.14 Using the data connection

67Figure 26.15 File transfer

68

Example 1Example 1

Figure 26.16 (next slide) shows an example of how a file is stored.

1. The control connection is created, and several control commands and responses are exchanged.

2. Data are transferred record by record.

3. A few commands and responses are exchanged to close the connection.

69Figure 26.16 Example 1

70

Table 26.4 Table 26.4 List of FTP commands in UNIXList of FTP commands in UNIX

Commands

!, $, account, append, ascii, bell, binary, bye, case, cd, cdup, close, cr, delete, debug, dir, discount, form, get, glob, hash, help, lcd, ls, macdef, mdelete, mdir, mget, mkdir, mls, mode, mput, nmap, ntrans, open, prompt, proxy, sendport, put, pwd, quit, quote, recv, remotehelp, rename, reset, rmdir, runique, send, status, struct, sunique, tenex, trace, type, user, verbose,?

71

Example 2Example 2

We show some of the user interface commands that accomplish the same task as in Example 1. The user input is shown in boldface. As shown below, some of the commands are provided automatically by the interface. The user receives a prompt and provides only the arguments.

$ ftp challenger.atc.fhda.eduConnected to challenger.atc.fhda.edu220 Server readyName: forouzanPassword: xxxxxxxftp > ls /usr/user/report200 OK150 Opening ASCII mode......................226 transfer completeftp > close221 Goodbyeftp > quit

72

Example 3Example 3

We show an example of using anonymous FTP. We connect to internic.net, where we assume there are some public data available.

$ ftp internic.netConnected to internic.net220 Server readyName: anonymous331 Guest login OK, send "guest" as passwordPassword: guestftp > pwd257 '/' is current directoryftp > ls200 OK150 Opening ASCII modebin...ftp > close221 Goodbyeftp > quit

73

Domain Name System (DNS)

2004 Prentice Hall, Inc.All rights reserved.

Outline81

TCP/IPTransmission Control Protocol / Internet Protocol

82

TCPTransmission Control Protocol

• TCP is an alternative transport layer protocol over IP.

• TCP provides:– Connection-oriented

– Reliable

– Full-duplex

– Byte-Stream

83

Connection-Oriented

• Connection oriented means that a virtual connection is established before any user data is transferred.

• If the connection cannot be established - the user program is notified.

• If the connection is ever interrupted - the user program(s) is notified.

84

Reliable

• Reliable means that every transmission of data is acknowledged by the receiver.

• If the sender does not receive acknowledgement within a specified amount of time, the sender retransmits the data.

85

Byte Stream

• Stream means that the connection is treated as a stream of bytes.

• The user application does not need to package data in individual datagrams (as with UDP).

86

Full Duplex

• TCP provides transfer in both directions.

87

TCP Ports

• Interprocess communication via TCP is achieved with the use of ports (just like UDP).

• UDP ports have no relation to TCP ports (different name spaces).

88

TCP Segments

• The chunk of data that TCP asks IP to deliver is called a TCP segment.

• Each segment contains:– data bytes from the byte stream

– control information that identifies the data bytes

89

TCP Segment Format

Destination Port

Options (if any)

Data

1 byte 1 byte

Source Port

Sequence Number

Acknowledgment Number

1 byte 1 byte

offset Reser. Control Window

Checksum Urgent Pointer

90

TCP Lingo

• When a client requests a connection it sends a “SYN” segment (a special TCP segment) to the server port.

• SYN stands for synchronize. The SYN message includes the client’s ISN.

• ISN is Initial Sequence Number.

91

More...

• Every TCP segment includes a Sequence Number that refers to the first byte of data included in the segment.

• Every TCP segment includes an Acknowledgement Number that indicates the byte number of the next data that is expected to be received.– All bytes up through this number have already been

received.

92

And more...

• There are a bunch of control flags:– URG: urgent data included.

– ACK: this segment is (among other things) an acknowledgement.

– RST: error – connection must be reset.

– SYN: synchronize Sequence Numbers (setup)

– FIN: polite connection termination.

93

TCP Connection Creation

• A server accepts a connection.– Must be looking for new connections!

• A client requests a connection.– Must know where the server is!

94

Client Starts

• A client starts by sending a SYN segment with the following information:– Client’s ISN (generated pseudo-randomly)

– Maximum Receive Window for client.

95

Server Response

• When a waiting server sees a new connection request, the server sends back a SYN segment with:– Server’s ISN (generated pseudo-randomly)

– Request Number is Client ISN+1

96

Finally

• When the Server’s SYN is received, the client sends back an ACK with:– Acknowledgment Number is Server’s ISN+1

97

SYNISN=X

SYNISN=X

Client Server

SYNISN=Y ACK=X+1

SYNISN=Y ACK=X+1

ACK=Y+1ACK=Y+1

1

2

3

98

Why 3-Way?

• Why is the third message necessary?

• HINTS: – TCP is a reliable service.

– IP delivers each TCP segment.

– IP is not reliable.

99

TCP Data and ACK

• Once the connection is established, data can be sent.

• Each data segment includes a sequence number identifying the first byte in the segment.

• Each segment (data or empty) includes a request number indicating what data has been received.

100

TCP Buffers

• Both the client and server allocate buffers to hold incoming and outgoing data– The TCP layer does this.

• Both the client and server announce with every ACK how much buffer space remains (the Window field in a TCP segment).

101

Send Buffers

• The application gives the TCP layer some data to send.

• The data is put in a send buffer, where it stays until the data is ACK’d.

• The TCP layer won’t accept data from the application unless (or until) there is buffer space.

102

ACKs

• A receiver doesn’t have to ACK every segment (it can ACK many segments with a single ACK segment).

• If a sender doesn’t get an ACK after some time limit, it resends the data.

103

Termination

• The TCP layer can send a RST segment that terminates a connection if something is wrong.

• Usually the application tells TCP to terminate the connection politely with a FIN segment.

104

FIN

• Either end of the connection can initiate termination.

• A FIN is sent, which means the application is done sending data.

• The FIN is ACK’d.• The other end must now send a FIN.• That FIN must be ACK’d.

105

FINSN=X

FINSN=X

App1 App2

ACK=X+1ACK=X+1

ACK=Y+1ACK=Y+1

1

2

4

FINSN=Y

FINSN=Y

3...

106

TCP TIME_WAIT

• Once a TCP connection has been terminated (the last ACK sent) there is some unfinished business:– What if the ACK is lost? The last FIN will be resent and it

must be ACK’d.

107

TCP Sockets Programming

• Creating a passive mode (server) socket.• Establishing an application-level connection.• Sending/receiving data.• Terminating a connection.

108

Establishing a passive mode TCP socket

Passive mode:– Address already determined.

– Tell the kernel to accept incoming connection requests directed at the socket address.

• 3-way handshake

– Tell the kernel to queue incoming connections for us.

109

Accepting an incoming connection.

• Once we start listening on a socket, the O.S. will queue incoming connections– Handles the 3-way handshake

– Queues up multiple connections.

• When our application is ready to handle a new connection, we need to ask the O.S. for the next connection.

110

Terminating a TCP connection

• Either end of the connection can call the close() system call.

• If the other end has closed the connection, and there is no buffered data, reading from a TCP socket returns 0 to indicate EOF.

111

Client Code

• TCP clients can connect to a server, which:– takes care of establishing an endpoint address for the client

socket.

– Attempts to establish a connection to the specified server.• 3-way handshake

112

Reading from a TCP socket

• By default read() will block until data is available.

• Reading from a TCP socket may return less than max bytes (whatever is available).

• You must be prepared to read data 1 byte at a time!

113

Writing to a TCP socket

• write might not be able to write all bytes (on a nonblocking socket).

114

Java Sockets Programming

• The package java.net provides support for sockets programming

• Typically you import everything defined in this package with:

import java.net.*;

115

Classes

InetAddress

Socket

ServerSocket

DatagramSocket

DatagramPacket

UDPUDP

116

Socket class

• Corresponds to active TCP sockets only!– client sockets

– socket returned by accept();

• Passive sockets are supported by a different class: ServerSocket

117

Socket Constructors

• Constructor creates a TCP connection to a named TCP server.– There are a number of constructors:Socket(InetAddress server, int port);

Socket(InetAddress server, int port,

InetAddress local, int localport);

Socket(String hostname, int port);

118

Socket Methods

void close();

InetAddress getInetAddress(); getpeername

InetAddress getLocalAddress(); getsockname

InputStream getInputStream();

OutputStream getOutputStream();

• Lots more (setting/getting socket options, partial close, etc.)

119

Socket I/O

• Socket I/O is based on the Java I/O support (in the package java.io).

• InputStream and OutputStream are abstract classes– common operations defined for all kinds of InputStreams,

OutputStreams…

120

ServerSocket Class(TCP Passive Socket)

• Constructors:

ServerSocket(int port);

ServerSocket(int port, int backlog);

ServerSocket(int port, int backlog,InetAddress bindAddr);

121

ServerSocket Methods

Socket accept();

void close();

InetAddress getInetAddress();

int getLocalPort();

throw IOException, SecurityException


Outline122

123

Newsgroups

• Newsgroups-electronic discussion groups where user reads and post message “posted” by a user can be read by several people

• Usenet-network of news groups• Messages posted on one newsgroup are distributed through Usenet

network• Different topics covered by newsgroups

– Recreational

– Technical

– Social area

– Etc.

124

• To access newsgroups you need– access to a news server– a news reader (client)– You must “subscribe” to the group

• News server must be maintained by a news administrator– Decides which groups will be delivered to a site

Newsgroups

125

Top Level for Names in News

• Groups• rec – Arts, hobbies, etc.• news – Usenet news• comp – Computer topics• soc – Social issues• sci – Scientific topics• misc – Topics don’t fit into any other category• alt – Alternative groups – often specific to the site

126

Format for Posted Articles

• Two parts: header and body

• Header (some common fields)

• Path: list of news servers involved in the transit of the article

• From: Address of person that posted the message

• Newsgroups: List of groups to which article was posted

• Subject or Summary

• Organization: Company or school associated with the person who posted the article


Outline127

UUCP – Unix to Unix copy

Allows remote execution of commands and transfer of files, email and net news between computers

Most commanly used for dial up connections

128

Equipped with modem – so that they can communicate remotly.

Each uucp network has the list of neighbor systems with phone number, login names and passwords.

129

Internet Explorer and the World Wide Web

130

Terminology

• HTTP – HyperText Transfer Protocol is used to transmit Web documents• HTTPS – Secure protocol for confidential transactions• HTML – The language in which all Web documents are displayed

• TCP/IP – A suite of protocols that allows multiple platforms to communicate

• URL – Uniform Resource Locator

• Web Server – Computers that store hypertext and/or hypermedia documents and make them available to other computers

• Web Client – Personal computers that access files held by web servers

• Web Browser – Software application to locate and display web pages

131

Hyperlinks

• The essence of the Web as you click on a link to more to the next document, which may be stored on a different computer

• Hyperlinks may contain text, graphics, sound, or video links– Blue underlined fonts are unexplored

– Magenta links have been previously accessed

www.microsoft.com

www.microsoft.com

132

The Web is always changing

Address bar (address is constant, but the content changes)

Hyperlinks

Print button

133

http://www.annex.com/southwest/museum.htm

Means of access,HyperText Transfer Protocol

Internet Address (Web site)

Document

Path (Directory or Folder)

Uniform Resource Locator (URL)

134

Domain Names

• Original Six:– .edu (education)

– .com (commercial)

– .gov (government)

– .mil (military)

– .net (network administration)

– .org (non-profit)

• New domains:– .biz (business)

– .pro (licensed professional)

– .info (information services)

– .uk (United Kingdom)

– .ca (Canada)

– .au (Australia)

135

Examples of URLs

• My school: www.miami.edu• Exploring Windows: www.prenhall.com/grauer• My favorite site: www.refdesk.com• Anti-virus updates: www.symantec.com• Download software: www.tucows.com

136

A message travels the Internet

All that matters is the beginning and ending address

137

Searching the Web

• Search Engines• Web Directories• Meta Search Engines• Clearinghouse

138

A program that systematically searches the Web for documents on a specific topic

Uses a key word or words as a query Several search engines are available Each search engine has its own database No search engine is best Uses Boolean (logical) operators Returns “hits” or documents once search has

been submitted

Search Engines

139

Popular Web Search Engines

http://www.altavista.com/ http://www.msn.com/

http://www.go.com/ http://www.excite.com/

http://www.lycos.com http://www.askjeeves.com/

http://www.webcrawler.com/ http://www.google.com/

http://www.yahoo.com http://www.search.com/

140

Web Site and Saving an Image

Choose Save Picture As command

Right click picture for context-sensitive menu

141

Security and Privacy

• Secure transactions – https protocol

– Encryption

• Privacy– Cookie is a small file written to your disk each time you visit

a site

– Problem is when one site can read many cookies, e.g., DoubleClick.com

142

Returning to a Previous Site

History folder

Favorites folder

143

Organize Favorites

Move a favorite

Create a new folder

Delete a favorite

Rename a favorite


Outline144

The TELNET Protocol

145

TELNET vs. telnet

• TELNET is a protocol that provides “a general,

bi-directional, eight-bit byte oriented

communications facility”.

• telnet is a program that supports the TELNET

protocol over TCP.

• Many application protocols are built upon the

TELNET protocol.

146

The TELNET Protocol

• TCP connection• data and control over the same connection.• Network Virtual Terminal• negotiated options

147

Network Virtual Terminal

• intermediate representation of a generic terminal.• provides a standard language for communication

of terminal control functions.

148

Network Virtual Terminal

NVTNVT NVTNVT

ServerServerProcessProcess

TCPTCP TCPTCP

149

Negotiated Options

• All NVTs support a minimal set of capabilities.• Some terminals have more capabilities than the

minimal set.• The 2 endpoints negotiate a set of mutually

acceptable options (character set, echo mode, etc).

150

Negotiated Options

• The protocol for requesting optional features is well defined and includes rules for eliminating possible negotiation “loops”.

• The set of options is not part of the TELNET protocol, so that new terminal features can be incorporated without changing the TELNET protocol.

151

Option examples

• Line mode vs. character mode

• echo modes

• character set (EBCDIC vs. ASCII)

152

Control Functions

• TELNET includes support for a series of control functions commonly supported by servers.

• This provides a uniform mechanism for communication of (the supported) control functions.

153

Control Functions

• Interrupt Process (IP)– suspend/abort process.

• Abort Output (AO)– process can complete, but send no more output to user’s

terminal.

• Are You There (AYT)– check to see if system is still running.

154

More Control Functions

• Erase Character (EC)– delete last character sent

– typically used to edit keyboard input.

• Erase Line (EL)– delete all input in current line.

155

Command Structure

• All TELNET commands and data flow through the same TCP connection.

• Commands start with a special character called the Interpret as Command escape character (IAC).

• The IAC code is 255.• If a 255 is sent as data - it must be followed by

another 255.

156

Looking for Commands

• Each receiver must look at each byte that arrives and look for IAC.

• If IAC is found and the next byte is IAC - a single byte is presented to the application/terminal (a 255).

• If IAC is followed by any other code - the TELNET layer interprets this as a command.

157

Command Codes

• IP 243• AO 244• AYT 245• EC 246• EL 247

WILLWILL 251251 WON’TWON’T 252252 DODO 253253 DON’TDON’T 254254 IACIAC 255255

158

Playing with TELNET

• You can use the telnet program to play with the TELNET protocol.

• telnet is a generic TCP client.– Sends whatever you type to the TCP socket.– Prints whatever comes back through the TCP socket.– Useful for testing TCP servers (ASCII based protocols).

159

Some TCP Servers you can play with

• Many Unix systems have these servers running (by default):– echo port 7– discard port 9– daytime port 13– chargen port 19

160

telnet hostname port

> telnet rcs.rpi.edu 7Trying 128.113.113.33...Connected to cortez.sss.rpi.edu (128.113.113.33).

Escape character is '^]'.Hi daveHi davestop itstop it^]telnet> quitConnection closed.

161

telnet vs. TCP

• Not all TCP servers talk TELNET (most don't)

• You can use the telnet program to play with these servers, but the fancy commands won't do anything.– type ^], then "help" for a list of fancy TELNET stuff you can do in telnet.


Outline162

Introduction to HTML

163

Agenda

• Introduction to HTML• Creating and Publishing Web pages• Main HTML elements• Block-Level HTML elements• Text-Level HTML elements• Creating Hyperlinks• Adding Images • Creating Tables, Forms and Frames

164

Hypertext Markup Language

• Language used to design web pages• Text mixed with Markup tags• Markup tags describe

• Appearance

• Layout

• Content

165

HTML Document Template

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 EN"><html><head><title>Title</title> </head><body> : : : : : :</body></html>

166

Main HTML Elements

1. DOCTYPE2. HTML3. HEAD Elements that can be included inside HEAD tag:

• TITLE• BASE• META• SCRIPT,NOSCRIPT• STYLE• LINK

167

Main HTML Elements(Continued)

4. BODY Attributes:

BACKGROUND

BGCOLORTEXTLINK,ALINK,VLINK

5. Elements inside BODY tag<body>

HTML tags</body>

168

Block-Level Elements

• Headings• H1…H6• ALIGN

• Basic Text Sections• P• ALGN• PRE• ADDRESS• BLOCKQUOTE• WIDTH• ADDRESS

• Lists• OL• LI• UL• DL• DT• DD

• Tables , Forms & Frames• Misc.

• HR• BR• CENTER

169

P: The Basic Paragraph

• Attributes–ALIGN

•LEFT (Default), RIGHT,CENTER•White Space is ignored•Consecutive <P>s don’t yield multiple lines•End tag is optional

<body><p> Paragraph 1</p><p> Paragraph 2</p></body>

170

LISTS

•Ordered Lists (OL)<OL>

<LI>

<LI>

:

</OL>

–Attributes : TYPE, START, COMPACTList Entries (LI)

–End Tag optional

–Attributes: VALUE, TYPE

171

LISTS (Continued)

•Unordered Lists (Bulleted Lists)<UL><LI><LI>….</UL>

–Attributes: TYPE, COMPACTTYPE can be DISC, CIRCLE, SQUARE

Ordered & Unordered lists can be nested.

172

Text-Level Elements

• Physical Character Styles– B, I, TT, U, SUB, SUP, BIG, SMALL, STRIKE, S, BLINK

– FONT• SIZE

• COLOR

• FACE

– BASEFONT

– SIZE

• Logical Character Styles– EM, STRONG, CODE, SAMP, KBD, DFN, VAR, CITE

173

Text – Level Elements (Continued)

• Hypertext links– A

• Attributes: HREF, TARGET, NAME,….

• Images– IMG

• Attributes: SRC (required), ALT, ALIGN, WIDTH, HEIGHT, VSPACE, HSPACE, BORDER, USEMAP, ISMAP

• Misc.– BR (Explicit line break)– AREA (Client side image maps)– APPLET (Java)– HR ( Horizontal Line)

174

Hypertext Links

• Links can contain images and other text level elements– <A HREF=…..>………</A>

• Link to absolute URL– Use a complete URL starting with http://

• Link to relative URL– Use a filename or relative path to filename

• Interpreted with respect to current file

175

Hypertext Links (Continued)

• Link to a section– Use a section name preceded by #– <A HREF=“#Section2”>Section 2</A>

• Link to a section in a URL– Use absolute or relative URL, then #, then section name

• Naming a section– Use <A NAME=“…..”>and do not include # sign– <A NAME=“Section2”>Images</A>

176

IMG – Embedding Images

• Example– <IMG SRC=“SomeFile.gif” ALT=“My Page” WIDTH=400

HEIGHT=300>

• Attributes– SRC (Required)– ALT (Technically Required)– ALIGN– WIDTH, HEIGHT– HSPACE, VSPACE– BORDER– USEMAP, ISMAP

177

Tables

• Template<TABLE BORDER=1>

<CAPTION>Table Caption</CAPTION><TR><TH>Heading 1</TH><TH>Heading 2</TH></TR><TR><TD>Row 1 Col 1 </TD><TD>Row 1 Col 2</TD></TR><TR><TD>Row 2 Col 1 </TD><TD>Row 2 Col 2</TD></TR>

</TABLE>

• TABLE Element Attributes– ALIGN : Horizontal alignment of the table .Values can be LEFT (default), RIGHT, CENTER.– BORDER : Specifies the width in pixels around the table .Default 0– CELLSPACING : Gives the space in pixels between adjacent cells. Default 3– CELLPADDING : Determines the empty space between the cell’s border and table element. Default is 1.– WIDTH : Specifies the width of the table in pixel or as percentage of the browser window.– BGCOLOR : Specifies the background color of the table

178

Tables (Continued)

• Table CAPTION

Attribute : ALIGN (Values: TOP, BOTTOM)

• Table Row (TR)– Used to define each row in the table

– Each row will contain <TH> & <TD>

– Attributes:• ALIGN, VALIGN, BGCOLOR

179

Tables (Continued)

• Table Cells TH & TD• Attributes :

– COLSPAN defines a heading or a cell data that spans more than one column.

– ROWSPAN defines a heading or a cell data that spans more than one row.

– ALIGN– VALIGN– WIDTH, HEIGHT

180

Frames

• Frame Template<html>

<head><title>DocumentTitle</title></head><frameset …>

<!– Frame and nested Frameset entries here --><noframes><body>

</body></noframes>

</frameset><html>

181

Frames (Continued)

• Attributes – COLS, ROWS

• A comma separated list of pixel values, percentages and weighted remainders.

• Frameset entries should always specify atleast two rows or columns.

• Examples

<frameset rows=“50,10%,*,2*”>…</frameset>

<frameset cols=“25,*,*”>….</frameset>

182

Frames (Continued)

• Frame Attributes (Continued)– FRAMEBORDER

• Indicates whether borders will be drawn between frame cells.• Yes or 1 specifies border & No or 0 specifies no border.

– BORDER (Netscape), FRAMESPACING (IE)• Specifies the border between frame cells.

– BORDERCOLOR• Sets the color of the border between cells.

183

Frames (Continued)

• Specifying contents of frame cells.– SRC

• URL of the document to place in the frame cell.– NAME

• Supplies destination for TARGET attribute for hypertext links.– BORDERCOLOR, FRAMEBORDER– MARGINWIDTH, MARGINHEIGHT

• Sets left/right & top/bottom cell margins.– SCROLLING

• Indicates whether cells should have margins.– NORESIZE

• Disables the ability to resize the frame cells.

184

Targeting Frame Cells

• Specify the cell in which place a page referenced by a hyperlink.

• The NAME attribute of the <FRAME>– <FRAME SRC=“” NAME=“Cell name”>

• The TARGET attribute of the <A HREF>– <A HREF=“ “ TARGET=“Cell name”>

185

Forms

• Adds interactivity to the html pages.• Template

<form action=“url” method=“get/post”>…form elements</form>

• Attributes– ACTION

• Specifies the location of a script or program that will process the data sent by the browser via the selections in the form.

– METHOD• define one of two ways the data from the form is sent to the program

that will process the data.

186

Forms (Continued)

• Basic Form Elements– Text fields

– Password fields

– Textarea fields

– Radio buttons

– Checkboxes

– Menu selections

– Buttons

187

Forms (Continued)

• Text input elements– Creates a textbox.

– Type attribute of input set to “text”.

– Attributes: name, size, value, maxlength

• Password input elements– Creates a textbox to enter password.

– Type attribute of input set to “password”.

– Attributes: name, size, value, maxlength

188

Forms (Continued)

• Check Boxes– Adds check boxes to the web page.– Type attribute of input set to “checkbox”.– Attributes: name, value, checked.– More than one can be selected.– Each has different value for name attribute.

• Radio Buttons– Adds radio buttons to the web page.– Type attribute of input set to “radio”.– Attributes: name, value, checked.– Only one button can be selected.– Same name for all radio buttons in the group.

189

Forms (Continued)

• Menu Selection– Provides drop-down menus.

– Here type=“select”

– <OPTION>..</OPTION> tag defines the text displayed in the menu.

– Attributes for OPTION: selected

• Submit & Reset Buttons– For submit, type=“submit”

– For reset, type=“reset”

– Both have attribute : value

190

Summary

• HTML document should be enclosed in the HTML,HEAD & BODY tags.

• Documents are composed of block-level and text-level elements.

• Hypertext links can be absolute or relative.• Tables are built using TABLE, TR, TH & TD tags.• Frames are created by FRAMESET & FRAME tags with

attributes like ROWS, COLS, SRC..• Forms contain elements like textboxes, radio buttons,

checkboxes, drop-down menu & buttons for submit and reset.

191

Dynamic HTML: Object Model and Collections

Outline Introduction Object Referencing Collections all and children Dynamic Styles Dynamic Positioning Using the frames Collection navigator Object Summary of the DHTML Object Model

192

Objectives

• In this lesson, you will learn:– To use the Dynamic HTML Object Model and scripting to

create dynamic Web pages.

– To understand the Dynamic HTML object hierarchy.

– To use the all and children collections to enumerate all of the XHTML elements of a Web page.

– To use dynamic styles and dynamic positioning.

– To use the frames collection to access objects in a separate frame on your Web page.

– To use the navigator object to determine which browser is being used to access your page.

193

Introduction

• Dynamic HTML Object Model– Allows Web authors to control the presentation of their pages– Gives them access to all the elements on their pages

• Web page– Elements, forms, frames, tables– Represented in an object hierarchy

• Scripting– Retrieve and modify properties and attributes

194

Object Referencing

• The simplest way to reference an element is by using the element’s id attribute.

• The element is represented as an object– XHTML attributes become properties that can be manipulated by

scripting

1951 <?xml version = "1.0"?>

2 <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN"

3 "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">

4

5 

6 

7

8 <html xmlns = "http://www.w3.org/1999/xhtml">

9 <head>

10 <title>Object Model</title>

11

12 <script type = "text/javascript">

13 

20 </script>

21

22 </head>

Outline

reference.html(1 of 2)

19623

24 <body onload = "start()">

25 <p id = "pText">Welcome to our Web page!</p>

26 </body>

27 </html>

Outline

reference.html(2 of 2)

197

Collections all and children

• Collections– Arrays of related objects on a page

– all• all the XHTML elements in a document

– children• Specific element contains that element’s child elements

1981 <?xml version = "1.0"?>



4

5 

6 

7


9 <head>


11


13 

Outline

all.html(1 of 2)

19925 </script>

26 </head>

27


29 <p id = "pText">Elements on this Web page:</p>

30 </body>

31 </html>

Outline

all.html(2 of 2)

200Outline

children.html(1 of 3)

1 <?xml version = "1.0"?>



4

5 

6 

7


9 <head>


11


13 <!--

14 var elements = "<ul>";

15

16 function child( object )

17 {

18 var loop = 0;

19

20 elements += "<li>" + object.tagName + "<ul>";

21

201Outline


22 for ( loop = 0; loop < object.children.length; loop++ )

23 {

24 if ( object.children[ loop ].children.length )

25 child( object.children[ loop ] );

26 else

27 elements += "<li>" +

28 object.children[ loop ].tagName +

29 "</li>";

30 }

31

32 elements += "</ul>" + "</li>";

33 }

34 // -->

35 </script>

36 </head>

37

20238 <body onload = "child( document.all[ 4 ] );

39 myDisplay.outerHTML += elements;

40 myDisplay.outerHTML += ‘</ul>’;">

41

42 <p>Welcome to our <strong>Web</strong> page!</p>

43

44 <p id = "myDisplay">

45 Elements on this Web page:

46 </p>

47

48 </body>

49 </html>

Outline


204

Dynamic Styles

• Element’s style can be changed dynamically

• Dynamic HTML Object Model also allows you to change the class attribute

2051 <?xml version = "1.0"?>



4

5 

6 

7


9 <head>


11


13 

22 </script>

23 </head>

Outline

dynamicstyle.html(1 of 2)

20624


26 <p>Welcome to our Web site!</p>

27 </body>

28 </html>

Outline

dynamicstyle.html(2 of 2)

2071 <?xml version = "1.0"?>



4

5 

6 

7


9 <head>


11

12 <style type = "text/css">

13

14 .bigText { font-size: 3em;

15 font-weight: bold }

16

17 .smallText { font-size: .75em }

18

19 </style>

20

Outline

dynamicstyle2.html(1 of 2)

22 

31 </script>

32 </head>

33


35 <p id = "pText">Welcome to our Web site!</p>

36 </body>

37 </html>

Outline

dynamicstyle2.html(2 of 2)

210

Dynamic Positioning

• XHTML elements can be positioned with scripting– Declare an element’s CSS position property to be either absolute

or relative– Move the element by manipulating any of the top, left, right or bottom CSS properties

2111 <?xml version = "1.0"?>



4

5 

6 

7


9 <head>

10 <title>Dynamic Positioning</title>

11


13 <!--

14 var speed = 5;

15 var count = 10;

16 var direction = 1;

17 var firstLine = "Text growing";

18 var fontStyle = [ "serif", "sans-serif", "monospace" ];

19 var fontStylecount = 0;

20

21 function start()

22 {

23 window.setInterval( "run()", 100 );

24 }

25

Outline

dynamicposition.html(1 of 3)

21226 function run()

27 {

28 count += speed;

29

30 if ( ( count % 200 ) == 0 ) {

31 speed *= -1;

32 direction = !direction;

33

34 pText.style.color =

35 ( speed < 0 ) ? "red" : "blue" ;

36 firstLine =

37 ( speed < 0 ) ? "Text shrinking" : "Text growing";

38 pText.style.fontFamily =

39 fontStyle[ ++fontStylecount % 3 ];

40 }

41

42 pText.style.fontSize = count / 3;

43 pText.style.left = count;

44 pText.innerHTML = firstLine + "<br /> Font size: " +

45 count + "px";

46 }

47 // -->

48 </script>

49 </head>

50

Outline



52 <p id = "pText" style = "position: absolute; left: 0;

53 font-family: serif; color: blue">

54 Welcome!</p>

55 </body>

56 </html>

Outline


215

Using the frames Collection

• Referencing elements and objects in different frames by using the frames collection

2161 <?xml version = "1.0"?>

2 <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Frameset//EN"

3 "http://www.w3.org/TR/xhtml1/DTD/xhtml1-frameset.dtd">

4

5 

6 

7


9 <head>

10 <title>Frames collection</title>

11 </head>

12

13 <frameset rows = "100, *">

14 <frame src = "top.html" name = "upper" />

15 <frame src = "" name = "lower" />

16 </frameset>

17

18 </html>

Outline

index.html(1 of 1)

2171 <?xml version = "1.0"?>



4

5 

6 

7


9 <head>

10 <title>The frames collection</title>

11


13 

21 </script>

22 </head>

23

Outline

top.html(1 of 2)


25 <h1>Cross-frame scripting!</h1>

26 </body>

27 </html>

Outline

top.html(2 of 2)

220

navigator Object

• Netscape, Mozilla, Microsoft’s Internet Explorer– Others as well

• Contains information about the Web browser

• Allows Web authors to determine what browser the user is using

2211 <?xml version = "1.0"?>



4

5 

6 

7


9 <head>

10 <title>The navigator Object</title>

11


13 <!--

14 function start()

15 {

16 if (navigator.appName=="Microsoft Internet Explorer")

17 {

18 if ( navigator.appVersion.substring( 1, 0 ) >= "4" )

19 document.location = "newIEversion.html";

20 else

21 document.location = "oldIEversion.html";

22 }

23 else

24 document.location = "NSversion.html";

25 }

Outline

navigator.html(1 of 2)

22226 // -->

27 </script>

28 </head>

29


31 <p>Redirecting your browser to the appropriate page,

32 please wait...</p>

33 </body>

34 </html>

Outline

navigator.html(2 of 2)

223

Summary of the DHTML Object Model

applets

all

anchors

embeds

forms

filters

images

links

plugins

styleSheets

scripts

frames

plugins

collection

body

screen

document

history

navigator

location

event

document

document

object

window

Key

Fig. 13.10 DHTML Object Model.

224


Object or collection Description Objects

window Represents the browser window and provides access to the document object contained in the window. If the window contains frames a separate window object is created automatically for each frame, to provide access to the document rendered in the frame. Frames are considered to be subwindows in the browser.

document Represents the XHTML document rendered in a window. The document object provides access to every element in the XHTML document and allows dynamic modification of the XHTML document.

body Provides access to the body element of an XHTML document. history Keeps track of the sites visited by the browser user. The object provides a script

programmer with the ability to move forward and backward through the visited sites, but for security reasons does not allow the actual site URLs to be manipulated.

navigator Contains information about the Web browser, such as the name of the browser, the version of the browser, the operating system on which the browser is running and other information that can help a script writer customize the user’s browsing experience.

location Contains the URL of the rendered document. When this object is set to a new URL, the browser immediately switches (navigates) to the new location.

event Can be used in an event handler to obtain information about the event that occurred (e.g., the mouse x-y coordinates during a mouse event).

screen Contains information about the computer screen for the computer on which the browser is running. Information such as the width and height of the screen in pixels can be used to determine the size at which elements should be rendered in a Web page.

Fig. 13.11 Objects in the Internet Explorer 6 Object Model.

225


Object or collection Description Collections

all Many objects have an all collection that provides access to every element contained in the object. For example, the body object’s all collection provides access to every element in the body element of an XHTML document.

anchors Collection contains all the anchor elements (a) that have a name or id attribute. The elements appear in the collection in the order they were defined in the XHTML document.

applets Contains all the applet elements in the XHTML document. Currently, the most common applet elements are Java applets.

embeds Contains all the embed elements in the XHTML document.

forms Contains all the form elements in the XHTML document. The elements appear in the collection in the order they were defined in the XHTML document.

frames Contains window objects that represent each frame in the browser window. Each frame is treated as its own subwindow.

images Contains all the img elements in the XHTML document. The elements appear in the collection in the order they were defined in the XHTML document.

links Contains all the anchor elements (a) with an href property. This collection also contains all the area elements that represent links in an image map.


226


Object or collection Description plugins Like the embeds collection, this collection contains all the embed elements in the

XHTML document. scripts Contains all the script elements in the XHTML document.

styleSheets Contains styleSheet objects that represent each style element in the XHTML document and each style sheet included in the XHTML document via link.


227

Cascading Style Sheets™ (CSS)

Outline Introduction Inline Styles Embedded Style Sheets Conflicting Styles Linking External Style Sheets

W3C CSS Validation Service Positioning Elements Backgrounds Element Dimensions Text Flow and the Box Model User Style Sheets Web Resources

228

Objectives

• In this lesson, you will learn:– To control the appearance of a Web site by creating style

sheets.

– To use a style sheet to give all the pages of a Web site the same look and feel.

– To use the class attribute to apply styles.

– To specify the precise font, size, color and other properties of displayed text.

– To specify element backgrounds and colors.

– To understand the box model and how to control the margins, borders and padding.

– To use style sheets to separate presentation from content.

229

Introduction

• Cascading Style Sheets (CSS)– Separation of structure from presentation

230

Inline Styles

• Declare an individual element’s format– Attribute style

– CSS property• Followed by a colon and a value

Outline231

inline.html(1 of 2)


2 <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.1//EN"

3 "http://www.w3.org/TR/xhtml11/DTD/xhtml11.dtd">

4

5 

6 

7


9 <head>

10 <title>Inline Styles</title>

11 </head>

12

13 <body>

14

15 <p>This text does not have any style applied to it.</p>

16

17 

18 

19 

20 <p style = "font-size: 20pt">This text has the

21 <em>font-size</em> style applied to it, making it 20pt.

22 </p>

23


Outline232

inline.html(2 of 2)

24 <p style = "font-size: 20pt; color: #0000ff">

25 This text has the <em>font-size</em> and

26 <em>color</em> styles applied to it, making it

27 20pt. and blue.</p>

28

29 </body>

30 </html>

233

Embedded Style Sheets

• Embed an entire CSS document in an XHTML document’s head section– Multipurpose Internet Mail Extensions (MIME) type

• Describes a file’s content

– Property background-color• Specifies the background color

– Property font-family• Specifies the name of the font to use

– Property font-size• Specifies a 14-point font

Outline234

declared.html(1 of 3)




4

5 

6 

7


9 <head>

10 <title>Style Sheets</title>

11

12 


14

15 em { background-color: #8000ff;

16 color: white }

17

18 h1 { font-family: arial, sans-serif }

19

20 p { font-size: 14pt }

21

22 .special { color: blue }

23

24 </style>

25 </head>

Outline235


26

27 <body>

28

29 

30 <h1 class = "special">Deitel & Associates, Inc.</h1>

31

32 <p>Deitel & Associates, Inc. is an internationally

33 recognized corporate training and publishing organization

34 specializing in programming languages, Internet/World

35 Wide Web technology and object technology education.

36 Deitel & Associates, Inc. is a member of the World Wide

37 Web Consortium. The company provides courses on Java,

38 C++, Visual Basic, C, Internet and World Wide Web

39 programming, and Object Technology.</p>

40

41 <h1>Clients</h1>

42 <p class = "special"> The company's clients include many

43 <em>Fortune 1000 companies</em>, government agencies,

44 branches of the military and business organizations.

45 Through its publishing partnership with Prentice Hall,

46 Deitel & Associates, Inc. publishes leading-edge

47 programming textbooks, professional books, interactive

48 CD-ROM-based multimedia Cyber Classrooms, satellite

49 courses and World Wide Web courses.</p>

50


Outline236


51 </body>

52 </html>

237

Conflicting Styles

• Inheritance– Descendant’s properties have greater specificity than

ancestor’s properties

Outline238

advance.html(1 of 3)




4

5 

6 

7


9 <head>

10 <title>More Styles</title>

11


13

14 a.nodec { text-decoration: none }

15

16 a:hover { text-decoration: underline;

17 color: red;

18 background-color: #ccffcc }

19

20 li em { color: red;

21 font-weight: bold }

22

23 ul { margin-left: 75px }

24


Outline239


25 ul ul { text-decoration: underline;

26 margin-left: 15px }

27

28 </style>

29 </head>

30

31 <body>

32

33 <h1>Shopping list for <em>Monday</em>:</h1>

34

35 <ul>

36 <li>Milk</li>

37 <li>Bread

38 <ul>

39 <li>White bread</li>

40 <li>Rye bread</li>

41 <li>Whole wheat bread</li>

42 </ul>

43 </li>

44 <li>Rice</li>

45 <li>Potatoes</li>

46 <li>Pizza <em>with mushrooms</em></li>

47 </ul>

48


Outline240


49 <p><a class = "nodec" href = "http://www.food.com">

50 Go to the Grocery store</a></p>

51

52 </body>

53 </html>

241

Linking External Style Sheets

• External style sheets– Can provide uniform look and feel to entire site


Outline242

styles.css(1 of 1)

1 /* Fig. 6.4: styles.css */

2 /* An external stylesheet */

3

4 a { text-decoration: none }

5

6 a:hover { text-decoration: underline;

7 color: red;

8 background-color: #ccffcc }

9

10 li em { color: red;

11 font-weight: bold;

12 background-color: #ffffff }

13

14 ul { margin-left: 2cm }

15

16 ul ul { text-decoration: underline;

17 margin-left: .5cm }

Outline243

external.html(1 of 2)




4

5 

6 

7


9 <head>

10 <title>Linking External Style Sheets</title>

11 <link rel = "stylesheet" type = "text/css"

12 href = "styles.css" />

13 </head>

14

15 <body>

16

17 <h1>Shopping list for <em>Monday</em>:</h1>

18 <ul>

19 <li>Milk</li>

20 <li>Bread

21 <ul>

22 <li>White bread</li>

23 <li>Rye bread</li>

24 <li>Whole wheat bread</li>

25 </ul>


Outline244

external.html(2 of 2)

26 </li>

27 <li>Rice</li>

28 <li>Potatoes</li>

29 <li>Pizza <em>with mushrooms</em></li>

30 </ul>

31

32 <p>

33 <a href = "http://www.food.com">Go to the Grocery store</a>

34 </p>

35

36 </body>

37 </html>

245

W3C CSS Validation Service

• Validates external CSS documents• Ensures that style sheets are syntactically correct

246


Fig. 6.6 Validating a CSS document. (Courtesy of World Wide Web Consortium (W3C).)

247


Fig. 6.7 CSS validation results. (Courtesy of World Wide Web Consortium (W3C).)

248

Positioning Elements

• Absolute positioning– z-index attribute

• Layer overlapping elements properly

• Relative positioning– Elements are positioned relative to other elements

Outline249

positioning.html(1 of 1)




4

5 

6 

7


9 <head>

10 <title>Absolute Positioning</title>

11 </head>

12

13 <body>

14

15 <p><img src = "i.gif" style = "position: absolute;

16 top: 0px; left: 0px; z-index: 1"

17 alt = "First positioned image" /></p>

18 <p style = "position: absolute; top: 50px; left: 50px;

19 z-index: 3; font-size: 20pt">Positioned Text</p>

20 <p><img src = "circle.gif" style = "position: absolute;

21 top: 25px; left: 100px; z-index: 2" alt =

22 "Second positioned image" /></p>

23

24 </body>

25 </html>

Outline251

positioning2.html(1 of 2)




4

5 

6 

7


9 <head>

10 <title>Relative Positioning</title>

11


13

14 p { font-size: 1.3em;

15 font-family: verdana, arial, sans-serif }

16

17 span { color: red;

18 font-size: .6em;

19 height: 1em }

20

21 .super { position: relative;

22 top: -1ex }

23

24 .sub { position: relative;

25 bottom: -1ex }

26


Outline252

positioning2.html2 of 2

27 .shiftleft { position: relative;

28 left: -1ex }

29

30 .shiftright { position: relative;

31 right: -1ex }

32

33 </style>

34 </head>

35

36 <body>

37

38 <p>The text at the end of this sentence

39 <span class = "super">is in superscript</span>.</p>

40


42 <span class = "sub">is in subscript</span>.</p>

43


45 <span class = "shiftleft">is shifted left</span>.</p>

46


48 <span class = "shiftright">is shifted right</span>.</p>

49

50 </body>

51 </html>

254

Backgrounds

• background-image– Specifies the image URL

• background-position– Places the image on the page

• background-repeat– Controls the tiling of the background image

• background-attachment– fixed– scroll

• font-weight– Specify the “boldness” of text

Outline255

background.html(1 of 2)




4

5 

6 

7

8 <html xmlns = "http://www.w3 .org/1999/xhtml">

9 <head>

10 <title>Background Images</title>

11


13

14 body { background-image: url(logo.gif);

15 background-position: bottom right;

16 background-repeat: no-repeat;

17 background-attachment: fixed; }

18

19 p { font-size: 18pt;

20 color: #aa5588;

21 text-indent: 1em;

22 font-family: arial, sans-serif; }

23

24 .dark { font-weight: bold; }

25


Outline256

background.html(2 of 2)

26 </style>

27 </head>

28

29 <body>

30

31 <p>

32 This example uses the background-image,

33 background-position and background-attachment

34 styles to place the <span class = "dark">Deitel

35 & Associates, Inc.</span> logo in the bottom,

36 right corner of the page. Notice how the logo

37 stays in the proper position when you resize the

38 browser window.

39 </p>

40

41 </body>

42 </html>

258

Element Dimensions

• CSS rules can specify the actual dimensions of each page element

Outline259

width.html(1 of 2)




4

5 

6 

7


9 <head>

10 <title>Box Dimensions</title>

11


13

14 div { background-color: #ffccff;

15 margin-bottom: .5em }

16 </style>

17

18 </head>

19

20 <body>

21

22 <div style = "width: 20%">Here is some

23 text that goes in a box which is

24 set to stretch across twenty percent

25 of the width of the screen.</div>


Outline260

width.html(2 of 2)

26

27 <div style = "width: 80%; text-align: center">

28 Here is some CENTERED text that goes in a box

29 which is set to stretch across eighty percent of

30 the width of the screen.</div>

31

32 <div style = "width: 20%; height: 30%; overflow: scroll">

33 This box is only twenty percent of

34 the width and thirty percent of the height.

35 What do we do if it overflows? Set the

36 overflow property to scroll!</div>

37

38 </body>

39 </html>

261

Text Flow and the Box Model

• Floating– Move an element to one side of the screen

• Box model– Margins

• margin-top, margin-right, margin-left, margin-bottom

– Padding• padding-top, padding-right, padding-left, and padding-bottom

– Border• border-width

– thin, medium, thick• border-color

– Sets the color• border-style

– none, hidden, dotted, dashed, solid, double, groove, ridge, inset and outset

Outline262

floating.html(1 of 3)




4

5 

6 

7


9 <head>

10 <title>Flowing Text Around Floating Elements</title>

11


13

14 div { background-color: #ffccff;

15 margin-bottom: .5em;

16 font-size: 1.5em;

17 width: 50% }

18

19 p { text-align: justify }

20

21 </style>

22

23 </head>

24


Outline263


25 <body>

26

27 <div style = "text-align: center">

28 Deitel & Associates, Inc.</div>

29

30 <div style = "float: right; margin: .5em;

31 text-align: right">

32 Corporate Training and Publishing</div>

33

34 <p>Deitel & Associates, Inc. is an internationally

35 recognized corporate training and publishing organization

36 specializing in programming languages, Internet/World

37 Wide Web technology and object technology education.

38 The company provides courses on Java, C++, Visual Basic, C,

39 Internet and World Wide Web programming, and Object Technology.</p>

40

41 <div style = "float: right; padding: .5em;

42 text-align: right">

43 Leading-Edge Programming Textbooks</div>

44

45 <p>The company's clients include many Fortune 1000

46 companies, government agencies, branches of the military

47 and business organizations.</p>

48


Outline264

49 <p style = "clear: right">Through its publishing

50 partnership with Prentice Hall, Deitel & Associates,

51 Inc. publishes leading-edge programming textbooks,

52 professional books, interactive CD-ROM-based multimedia

53 Cyber Classrooms, satellite courses and World Wide Web

54 courses.</p>

55

56 </body>

57 </html>


265

Text Flow and the Box Model

Content

Margin

Border

Padding

Fig. 6.13 Box model for block-level elements.

Outline266

borders.html(1 of 2)




4

5 

6 

7


9 <head>

10 <title>Borders</title>

11


13

14 body { background-color: #ccffcc }

15

16 div { text-align: center;

17 margin-bottom: 1em;

18 padding: .5em }

19

20 .thick { border-width: thick }

21

22 .medium { border-width: medium }

23

24 .thin { border-width: thin }

25


Outline267

borders.html(2 of 2)

26 .groove { border-style: groove }

27

28 .inset { border-style: inset }

29

30 .outset { border-style: outset }

31

32 .red { border-color: red }

33

34 .blue { border-color: blue }

35

36 </style>

37 </head>

38

39 <body>

40

41 <div class = "thick groove">This text has a border</div>

42 <div class = "medium groove">This text has a border</div>

43 <div class = "thin groove">This text has a border</div>

44

45 <p class = "thin red inset">A thin red line...</p>

46 <p class = "medium blue outset">

47 And a thicker blue line</p>

48

49 </body>

50 </html>

Outline269

borders2.html(1 of 2)




4

5 

6 

7


9 <head>

10 <title>Borders</title>

11


13

14 body { background-color: #ccffcc }

15

16 div { text-align: center;

17 margin-bottom: .3em;

18 width: 50%;

19 position: relative;

20 left: 25%;

21 padding: .3em }

22 </style>

23 </head>

24

25 <body>


Outline270

borders2.html(2 of 2)

26

27 <div style = "border-style: solid">Solid border</div>

28 <div style = "border-style: double">Double border</div>

29 <div style = "border-style: groove">Groove border</div>

30 <div style = "border-style: ridge">Ridge border</div>

31 <div style = "border-style: inset">Inset border</div>

32 <div style = "border-style: outset">Outset border</div>

33

34 </body>

35 </html>

271

User Style Sheets

• Format pages based on preferences

Outline272

User_absolute.html(1 of 2)




4

5 

6 

7


9 <head>

10 <title>User Styles</title>

11


13

14 .note { font-size: 9pt }

15

16 </style>

17 </head>

18

19 <body>

20

21 <p>Thanks for visiting my Web site. I hope you enjoy it.

22 </p><p class = "note">Please Note: This site will be

23 moving soon. Please check periodically for updates.</p>


Outline273

User_absolute.html(2 of 2)

24

25 </body>

26 </html>


Outline274

userstyles.css1 of 1

1 /* Fig. 6.17: userstyles.css */

2 /* A user stylesheet */

3

4 body { font-size: 20pt;

5 color: yellow;

6 background-color: #000080 }

275

User Style Sheets

Fig. 6.18 User style sheet in Internet Explorer 6.

276

User Style Sheets

Fig. 6.19 User style sheet applied with pt measurement.

Outline277

User_relative.html(1 of 2)




4

5 

6 

7


9 <head>

10 <title>User Styles</title>

11


13

14 .note { font-size: .75em }

15

16 </style>

17 </head>

18

19 <body>

20

21 <p>Thanks for visiting my Web site. I hope you enjoy it.

22 </p><p class = "note">Please Note: This site will be

23 moving soon. Please check periodically for updates.</p>


Outline278

User_relative.html(2 of 2)

24

25 </body>

26 </html>

279

User Style Sheets

Fig. 6.21 User style sheet applied with em measurement.

280

Introduction to XHTML

Outline Introduction Editing XHTML First XHTML Example W3C XHTML Validation Service Headers Linking Images Special Characters and More Line Breaks Unordered Lists Nested and Ordered Lists Web Resources

281

Objectives

• In this chapter, you will learn:– To understand important components of XHTML

documents.

– To use XHTML to create Web pages.

– To be able to add images to Web pages.

– To understand how to create and use hyperlinks to navigate Web pages.

– To be able to mark up lists of information.

282

Introduction

• Extensible HyperText Markup Language– XHTML

– A markup language

– Separation of the presentation of a document from the structure of the document’s information

– Based on HTML• Technology of the World Wide Web Consortium (W3C)

283

Editing XHTML

• XHTML documents– Source-code form

– Text editor (e.g. Notepad, Wordpad, emacs, etc.)– .html or .htm file-name extension

– Web server• Stores XHTML documents

– Web browser• Requests XHTML documents

284

First XHTML Example

• XHTML comments– Start with – html element

• head element– Head section

• Title of the document• Style sheets and scripts

• body element– Body section

• Page’s content the browser displays

– Start tag• attributes (provide additional information about an

element)– name and value (separated by an equal sign)

– End tag

Outline285

main.html(1 of 1)




4

5 

6 

7


9 <head>

10 <title>Internet and WWW How to Program - Welcome</title>

11 </head>

12

13 <body>

14 <p>Welcome to XHTML!</p>

15 </body>

16 </html>

286

W3C XHTML Validation Service

• Validation service ( validator.w3.org )– Checking a document’s syntax

• URL that specifies the location of the file• Uploading a file to the site validator.w3.org/file-upload.html

287


288


289

Headers

• Six headers ( header elements)– h1 through h6

Outline290

header.html(1 of 1)




4

5 

6 

7


9 <head>

10 <title>Internet and WWW How to Program - Headers</title>

11 </head>

12

13 <body>

14

15 <h1>Level 1 Header</h1>

16 <h2>Level 2 header</h2>





21

22 </body>

23 </html>

292

Linking

• Hyperlink– References other sources such as XHTML documents and

images

– Both text and images can act as hyperlinks

– Created using the a (anchor) element• Attribute href

– Specifies the location of a linked resource

• Link to e-mail addresses using mailto: URL

• <strong> tag– Bold

Outline293

links.html(1 of 2)




4

5 

6 

7


9 <head>

10 <title>Internet and WWW How to Program - Links</title>

11 </head>

12

13 <body>

14

15 <h1>Here are my favorite sites</h1>

16

17 <p><strong>Click a name to go to that page.</strong></p>

18

19 

20 <p><a href = "http://www.deitel.com">Deitel</a></p>

21

22 <p><a href = "http://www.prenhall.com">Prentice Hall</a></p>

23

24 <p><a href = "http://www.yahoo.com">Yahoo!</a></p>

25


Outline294

links.html(2 of 2)

26 <p><a href = "http://www.usatoday.com">USA Today</a></p>

27

28 </body>

29 </html>

Outline295

contact.html(1 of 1)




4

5 

6 

7


9 <head>

10 <title>Internet and WWW How to Program - Contact Page</title>

11 </head>

12

13 <body>

14

15 <p>

16 My email address is

17 <a href = "mailto:[email protected]">

18 [email protected]

19 </a>

20 . Click the address and your browser will

21 open an e-mail message and address it to me.

22 </p>

23 </body>

24 </html>

297

Images

• Three most popular formats– Graphics Interchange Format (GIF)

– Joint Photographic Experts Group (JPEG)

– Portable Network Graphics (PNG)

– img element• src attribute

– Specifies the location of the image file

• width and height

• Pixels (“picture elements”)

• Empty elements– Terminated by character / inside the closing right angle bracket

(>), or by explicitly including the end tag

• br element– Line break

Outline298

picture.html(1 of 1)




4

5 

6 

7


9 <head>

10 <title>Internet and WWW How to Program - Welcome</title>

11 </head>

12

13 <body>

14

15 <p>

16 <img src = "xmlhtp.jpg" height = "238" width = "183"

17 alt = "XML How to Program book cover" />

18 <img src = "jhtp.jpg" height = "238" width = "183"

19 alt = "Java How to Program book cover" />

20 </p>

21 </body>

22 </html>

Outline300

nav.html(1 of 2)




4

5 

6 

7


9 <head>

10 <title>Internet and WWW How to Program - Navigation Bar

11 </title>

12 </head>

13

14 <body>

15

16 <p>

17 <a href = "links.html">

18 <img src = "buttons/links.jpg" width = "65"

19 height = "50" alt = "Links Page" />

20 </a><br />

21

22 <a href = "list.html">

23 <img src = "buttons/list.jpg" width = "65"

24 height = "50" alt = "List Example Page" />

25 </a><br />


Outline301

nav.html(2 of 2)

26

27 <a href = "contact.html">

28 <img src = "buttons/contact.jpg" width = "65"

29 height = "50" alt = "Contact Page" />

30 </a><br />

31

32 <a href = "header.html">

33 <img src = "buttons/header.jpg" width = "65"

34 height = "50" alt = "Header Page" />

35 </a><br />

36

37 <a href = "table1.html">

38 <img src = "buttons/table.jpg" width = "65"

39 height = "50" alt = "Table Page" />

40 </a><br />

41

42 <a href = "form.html">

43 <img src = "buttons/form.jpg" width = "65"

44 height = "50" alt = "Feedback Form" />

45 </a><br />

46 </p>

47

48 </body>

49 </html>

303

Special Characters and More Line Breaks

• Character entity references (in the form &code;)• Numeric character references (e.g. &)

• del– Strike-out text

• sup– Superscript text

• sub– Subscript text

• <hr />– Horizontal rule (horizontal line)

Outline304

contact2.html(1 of 2)




4

5 

6 

7


9 <head>

10 <title>Internet and WWW How to Program - Contact Page

11 </title>

12 </head>

13

14 <body>

15

16 

17 

18 <p>

19 Click

20 <a href = "mailto:[email protected]">here

21 </a> to open an e-mail message addressed to

22 [email protected].

23 </p>

24

25 <hr />

Outline305

contact2.html(2 of 2)

26

27 <p>All information on this site is <strong>©</strong>

28 Deitel <strong>&</strong> Associates, Inc. 2002.</p>

29

30 

31 

32 

33 

34 <p><del>You may download 3.14 x 10<sup>2</sup>

35 characters worth of information from this site.</del>

36 Only <sub>one</sub> download per hour is permitted.</p>

37

38 <p>Note: <strong>< ¼</strong> of the information

39 presented here is updated daily.</p>

40

41 </body>

42 </html>

307

Unordered Lists

• Unordered list element ul– Creates a list in which each item begins with a bullet symbol

(called a disc)– li (list item)

• Entry in an unordered list

Outline308

links2.html(1 of 2)




4

5 

6 

7


9 <head>

10 <title>Internet and WWW How to Program - Links</title>

11 </head>

12

13 <body>

14

15 <h1>Here are my favorite sites</h1>

16

17 <p><strong>Click on a name to go to that page.</strong></p>

18

19 

20 <ul>

21

22 

23 <li><a href = "http://www.deitel.com">Deitel</a></li>

24

25 <li><a href = "http://www.w3.org">W3C</a></li>


Outline309

links2.html(2 of 2)

26

27 <li><a href = "http://www.yahoo.com">Yahoo!</a></li>

28

29 <li><a href = "http://www.cnn.com">CNN</a></li>

30 </ul>

31 </body>

32 </html>

310

Nested and Ordered Lists

• Represent hierarchical relationships• Ordered lists (ol)

– Creates a list in which each item begins with a number

Outline311

list.html(1 of 3)




4

5 

6 

7


9 <head>

10 <title>Internet and WWW How to Program - Lists</title>

11 </head>

12

13 <body>

14

15 <h1>The Best Features of the Internet</h1>

16

17 

18 <ul>

19 <li>You can meet new people from countries around

20 the world.</li>

21 <li>

22 You have access to new media as it becomes public:

23

Outline312

list.html(2 of 3)

24 

25 

26 

27 <ul>

28 <li>New games</li>

29 <li>

30 New applications

31

32 

33 <ol>

34 <li>For business</li>

35 <li>For pleasure</li>

36 </ol>

37 </li>

38

39 <li>Around the clock news</li>

40 <li>Search engines</li>

41 <li>Shopping</li>

42 <li>

43 Programming

44

45 

46 <ol>

47 <li>XML</li>

48 <li>Java</li>

Outline313

list.html(3 of 3)

49 <li>XHTML</li>

50 <li>Scripts</li>

51 <li>New languages</li>

52 </ol>

53

54 </li>

55

56 </ul> 

57 </li>

58

59 <li>Links</li>

60 <li>Keeping in touch with old friends</li>

61 <li>It is the technology of the future!</li>

62

63 </ul> 

64

65 </body>

66 </html>

315

Domain NameSystem(DNS)

316

Overview

• Introduction to the DNS• DNS Components• DNS Structure and Hierarchy• The DNS in Context

317

Overview

• Introduction to the DNS• DNS Components

– The name space

– The servers

– The resolvers

• DNS Structure and Hierarchy• The DNS in Context

318

The Name Space

• The name space is the structure of the DNS database– An inverted tree with the root node at the top

• Each node has a label– The root node has a null label, written as “”

th ird -le ve l n o de

se co n d-le ve l no de se co n d-le ve l no de

to p -le ve l no de

th ird -le ve l n o de th ird -le ve l n o de

se co n d-le ve l no de

to p -le ve l no de

se co n d-le ve l no de se co n d-le ve l no de

to p -le ve l no de

T h e roo t no de""

319

Domain namesand labels

320

FQDN and PQDN

321

Domain Names

• A domain name is the sequence of labels from a node to the root, separated by dots (“.”s), read left to right

– The name space has a maximum depth of 127 levels

– Domain names are limited to 255 characters in length

• A node’s domain name identifies its position in the name space

d a ko ta

w e s t

to rna do

e a st w w w

n o m in um m e ta in fo

com

b e rke ley n w u

e du g ov

n a to

in t

a rm y

m il

uu

n e t o rg

""

322

Hierarchy of name servers

323

DNS in the Internet

324

Generic domains

325

Country domains

326

Inverse domain

327

Name Servers

• Name servers store information about the name space in units called “zones”– The name servers that load a complete zone are said to “have

authority for” or “be authoritative for” the zone

• Also, a single name server may be authoritative for many zones

328

Types of Name Servers

• Two main types of servers– Authoritative – maintains the data

• Master – where the data is edited

• Slave – where data is replicated to

– Caching – stores data obtained from an authoritative server

– The most common name server implementation (BIND) combines these two into a single process

329

Name Server Architecture

• You can think of a name server as part:– database server, answering queries about the parts of the

name space it knows about (i.e., is authoritative for),

– cache, temporarily storing data it learns from other name servers, and

– agent, helping resolvers and other name servers find data that other name servers know about

330

Name Server Architecture

Master

serverZone transfer

Zone

data

file

From

diskAuthoritative Data

(primary master and

slave zones)

Agent

(looks up queries

on behalf of resolvers)

Cache Data

(responses from

other name servers)

Name Server Process

331

Authoritative Data

ResolverQuery

Response

Authoritative Data

(primary master and

slave zones)

Agent

(looks up queries


Cache Data

(responses from

other name servers)

Name Server Process

332

Using Other Name Servers

Arbitrary

name

server

Response

ResolverQuery

Query

Authoritative Data

(primary master and

slave zones)

Agent

(looks up queries


Cache Data

(responses from

other name servers)

Name Server Process

Response

333

Cached Data

Query

Response

Authoritative Data

(primary master and

slave zones)

Agent

(looks up queries


Cache Data

(responses from

other name servers)

Name Server Process

Resolver

334

Overview

• Introduction to the DNS• DNS Components

– The name space

– The servers

– The resolvers

• DNS Structure and Hierarchy• The DNS in Context

335

Name Resolution

• Name resolution is the process by which resolvers and name servers cooperate to find data in the name space

• To find information anywhere in the name space, a name server only needs the names and IP addresses of the name servers for the root zone (the “root name servers”)– The root name servers know about the top-level zones and can tell

name servers whom to contact for all TLDs

336

Name Resolution

• A DNS query has three parameters:– A domain name (e.g., www.nominum.com),

• Remember, every node has a domain name!

– A class (e.g., IN), and

– A type (e.g., A)

• A name server receiving a query from a resolver looks for the answer in its authoritative data and its cache– If the answer isn’t in the cache and the server isn’t authoritative

for the answer, the answer must be looked up

337

ping www.nominum.com.

The Resolution Process

• Let’s look at the resolution process step-by-step:

annie.west.sprockets.com

338

What’s the IP address of

www.nominum.com?


• The workstation annie asks its configured name server, dakota, for www.nominum.com’s address

ping www.nominum.com.annie.west.sprockets.com

dakota.west.sprockets.com

339


• The name server dakota asks a root name server, m, for www.nominum.com’s address


m.root-servers.net



www.nominum.com?

340


• The root server m refers dakota to the com name servers

• This type of response is called a “referral”


m.root-servers.net

dakota.west.sprockets.com Here’s a list of the com name servers.

Ask one of them.

341


• The name server dakota asks a com name server, f, for www.nominum.com’s address


m.root-servers.net



www.nominum.com?

f.gtld-servers.net

342


• The com name server f refers dakota to the nominum.com name servers


f.gtld-servers.net

m.root-servers.net


Here’s a list of the nominum.com name servers.

Ask one of them.

343


• The name server dakota asks an nominum.com name server, ns1.sanjose, for www.nominum.com’s address


f.gtld-servers.net

m.root-servers.net


ns1.sanjose.nominum.net


www.nominum.com?

344


• The nominum.com name server ns1.sanjose responds with www.nominum.com’s address


f.gtld-servers.net

m.root-servers.net


ns1.sanjose.nominum.netHere’s the IP address for

www.nominum.com

345

Here’s the IP address for

www.nominum.com


• The name server dakota responds to annie with www.nominum.com’s address


f.gtld-servers.net

m.root-servers.net



346

ping ftp.nominum.com.

Resolution Process (Caching)

• After the previous query, the name server dakota now knows:

– The names and IP addresses of the com name servers

– The names and IP addresses of the nominum.com name servers

– The IP address of www.nominum.com

• Let’s look at the resolution process again


347


What’s the IP address of ftp.nominum.com?


• The workstation annie asks its configured name server, dakota, for ftp.nominum.com’s address


f.gtld-servers.net

m.root-servers.net



348


What’s the IP address of ftp.nominum.com?


• dakota has cached an NS record indicating ns1.sanjose is an nominum.com name server, so it asks it for ftp.nominum.com’s address


f.gtld-servers.net

m.root-servers.net



349



ftp.nominum.com


• The nominum.com name server ns1.sanjose responds with ftp.nominum.com’s address


f.gtld-servers.net

m.root-servers.net



350



ftp.nominum.com


• The name server dakota responds to annie with ftp.nominum.com’s address


f.gtld-servers.net

m.root-servers.net



351

Overview

• Introduction to the DNS• DNS Components• DNS Structure and Hierarchy• The DNS in Context

352

The Current TLDs

C O MC o m m e rc ia l O rg a n iza tio ns

N E TN e tw o rk In fra stru c tu re

O R GO th er O rga n iza tio ns

G e n e ric T L D s(g T L D s)

A FA fg ha n is tan

A LA lba n ia

D ZA lg e ria

...

Y UY u g os la v ia

Z MZ a m b ia

Z WZ im ba b we

C o u n try C o de T L D s(ccT L D s )

IN TIn te rna tion a l Tre a ty O rga n iza tio ns

A R P A(T ra n s it ion D e v ice)

In te rn a tion a l T L D s(iT L D s )

G O VG o vern m e n ta l O rga n iza tio ns

M ILM ilita ry O rga n iza tio ns

E D UE d uca tio n a l In stitu tio ns

U S L e g acy T L D s(u sT L D s)

"."

353

Registries, Registrars, and Registrants

Registry Zone DB

RegistrantsRegistrants

End user requests add/modify/delete

Registrar submits add/modify/delete to registry

Registrar RegistrarRegistrar

Masterupdated

Registry updateszone

Slaves updated

354

The “Generic” Top-Level Domains (gTLDs)

• .COM, .NET, and .ORG– By far the largest top level domains on the Internet today

• .COM has approx. 20,000,000 names

– Essentially no restriction on what can be registered

• Network Solutions (now Verisign) received the contract for the registry for .COM, .NET, and .ORG– also a registrar for these TLDs

355

New Top Level Domains

• Recently, ICANN created 7 new top level domains:– .aero, .biz, .coop, .info, .museum, .name, .pro

• Some are chartered (.aero, .coop, .museum, .name, .pro)• Some are generic (.biz, .info)

– Expect these new TLDs to show up around 2Q01

• Many people unhappy with the process by which these new TLDs were created– Expect continued “discussion”

356

ccTLD Organization

• How each country top-level domain is organized is up to the country– Some, like Australia’s au, follow the functional definitions

• com.au, edu.au, etc.– Others, like Great Britain’s uk and Japan’s jp, divide the domain

functionally but use their own abbreviations• ac.uk, co.uk, ne.jp, ad.jp, etc.

– A few, like the United State’s us, are largely geographical• co.us, md.us, etc.

– Canada uses organizational scope• bnr.ca has national scope, risq.qc.ca has Quebec scope

– Some are flat, that is, no hierarchy• nlnet.nl, univ-st-etienne.fr

– Considered a question of national sovereignty

357

.arpa

• Now, Address and Routing Parameter Area– Was Advanced Research Projects Administration

• Used for infrastructure domains– IPv4 reverse (address to name) lookups– IPv6 reverse lookups– E.164

358

Other TLDs

• .GOV – used by US Governmental organizations– E.g., state.gov, doj.gov, whitehouse.gov, etc.

• .MIL – used by the US Military– E.g., af.mil, army.mil, etc.

• .EDU – used for Educational institutions– Higher learning, not only US-based ones

– E.g., harvard.edu, unu.edu, utoronto.edu

• .INT – international treaty organizations– E.g., itu.int, nato.int, wipo.int

359Figure 18-11

Recursive resolution

360Figure 18-12Iterative resolution

361

Questions?

362

TELNET

363

CONTENTSCONTENTS• CONCEPT• NETWORK VIRTUAL TERMINAL (NVT)• NVT CHARACTER SET• EMBEDDING• OPTIONS• OPTION NEGOTIATION• SUBOPTION NEGOTIATION• CONTROLLING THE SERVER• OUT-OF-BAND SIGNALING

364

CONTENTS CONTENTS (Continued)(Continued)

• ESCAPE CHARACTER• MODE OF OPERATION• EXAMPLES• USER INTERFACE• RLOGIN (REMOTE LOGIN)• SECURITY ISSUE

365

TELNET and Rlogin are TELNET and Rlogin are general-purpose general-purpose

client-server application programs.client-server application programs.

366

CONCEPT

367

Local login

368

Remote login

369

NETWORKVIRTUAL

TERMINAL

370Figure 19-3

NVT

371

NVTCHARACTER

SET

372Figure 19-4

Format of data characters

373Figure 19-5

Format of control characters

374

EMBEDDING

375Figure 19-6

Embedding

376

OPTIONS

377

OPTIONNEGOTIATION

378

Offer to enable

379

Request to enable

380

Offer to disable

381

Request to disable

382

Echo option example

383

SUBOPTIONNEGOTIATION

384

Example of suboption negotiation

385

CONTROLLINGTHE

SERVER

386

Example of interrupting an application program

387

OUT-OF-BANDSIGNALING

388

Out-of-band signaling

389

ESCAPECHARACTER

390

Two different interruptions

391

MODEOF

OPERATION

392

EXAMPLES

393

Example 1Example 1

In this example, we use the default mode to show the concept and its deficiencies even though it is almost obsolete today. The client and the server negotiate the terminal type and terminal speed and then the server checks the login and password of the user. See Figure 19.16.

394Example1

395

Example 2Example 2

In this example, we show how the client switches to the character mode. This requires that the client request the server to enable the SUPPRESS GO AHEAD and ECHO options.

396Figure 19-17

Example 2