Introduction to web graphics understanding the basics of web graphics

Introduction to Web Graphics Understanding the Basics of Web Graphics 1 WEB SERVERS 2 Objectives In this chapter, you will • Learn about Internet Information Services • Become familiar with the compon[.]

WEB SERVERS

In this chapter, you will:

• Learn about Internet Information Services

• Become familiar with the components of a Web server, and specify the Web server's home

directory and default document

• Create and configure Web server physical

directories, virtual directories, and applications

In this chapter, you will:

• Learn how to organize a Web server

• Learn how to reference files on a Web server

• Understand the factors that impact Web site

performance

Web Servers

• Web servers: computers that are connected to

the Internet and run Web server software

• A personal Web server: allows only a limited

number of user connections

• A production Web server: available to anyone

who connects to the Internet

Internet Information Services

• Internet Information Services (IIS)

– Web server software that comes with Windows NT,

Windows 2000, and Windows XP

– Includes an administration utility to create,

manage, and administer a Web server

• A Web server is also called a Web site

Internet Information Services

• IIS administrative utility: performs Web server

administrative tasks within IIS

• In Windows XP, the administrative utility is part of Internet Information Services

• IIS: the Web server software

• IIS console: the administrative utility within IIS

Internet Information Services

• Console: an environment for administering a

computer resource

• Microsoft Management Console (MMC): an

environment for administering computer

resources

• Snap-ins: Network administrators create custom consoles, which are components for computer management tasks that can be “snapped into” a generic console as needed

Internet Information Services

• IIS console: a custom console containing the Internet

Information Services snap-in, which includes components for administering Web servers

• Figure 5-1 shows the IIS console

Web Server Components

• Home directory: directory on the Web server that

is the starting point for accessing the Web pages, graphic image files, programs, and other files that are available from the Web site

• Console tree: displays the components within a Web server’s home directory as physical

directories, virtual directories, and applications

Web Server Components

• Physical directories: created within the Web

server’s home directory, or within directories that the Web administrator associates with other Web server components

• Virtual directories: may or may not be physically within the Web server’s home directory, but

appear to client browsers as though they are

• Applications: virtual directories that have the

permissions necessary to run server-side

executable programs and scripts

Web Server Components

• To administer a Web server, a Web administrator must

– Designate and configure the Web server’s home

directory and default document

– Create and configure the Web server’s physical

directories, virtual directories, and applications

• Many Web server configuration tasks are

performed using the Web Site Properties dialog box in the IIS console

The Web Site Properties Page

• The Web Site

properties page is used to configure the properties that identify the Web site, such as its IP address, port, connection timeout value, and the active log format

The Home Directory Properties Page

• The home

directory for a Web server is specified on the Home Directory properties page

The Home Directory Properties Page

• The first three option buttons on the Home Directory

properties page specify whether the Web site displays

documents from:

– A directory located on this computer

– A share located on another computer

– A redirection to a URL

• Local Path field: specifies the path to the home directory

• The remaining properties on the Home Directory properties

page specify permissions that the system grants to users who connect to the Web site in the home directory

The Home Directory Properties Page

• Today, most computers are connected to

networks

• Network share:

– makes computer files available to other users on a

network

– a drive or directory that network administrators

configure so that users can view and manipulate its files and subdirectories from other network

computers

The Documents Properties Page

• When a user enters a URL that contains a Web

server domain name or IP address but no HTML Web page filename in the Address field on his or her Web browser, the Web server returns its

default document, if one exists

• The default document filename is specified on the Documents properties page in the Properties

dialog box

The Documents Properties Page

• On this page, the Enable Default Document check box

is used to enable or disable the default document

Creating and Configuring Web Server

Physical Directories

• Physical directories: enable the Web administrator to

– Organize the contents of the local Web site

– Control access privileges for files and applications

• Physical directory exists:

– Within the Web server’s home directory

– Within a directory associated with a virtual directory – Within a directory associated with an application

Physical Directories

• To access files that are in a physical directory on the Web server’s home directory, a user can enter the URL for a Web server, a front slash (/), the

name of the physical directory, another front

slash, and the filename

Virtual Directories

• Virtual directory

– Appears to client browsers as a physical directory

within the home directory

– Can be associated with a physical directory that is

located anywhere in the Web server’s file system,

on a network share, or using a redirection to a URL that references a directory on another Web server

Virtual Directories

• Virtual directory:

– Can enable users to access Web pages and other

files stored in directories outside the home

directory and its subdirectories

– Has an associated alias, which is the name that

client browsers use to access the virtual

directory’s contents

• Alias:

– usually shorter than the original directory path

specification

Virtual Directories

• Virtual Directory Creation Wizard:

– Creates a virtual directory in the IIS console

– Presents a series of pages that prompt the

administrator to enter the specifications for the

virtual directory

Virtual Directories

• These pages include:

– A Welcome page

– An Alias page

– A Web Site Content Directory page

– An Access Permissions page

– A Finish page

• Application: a virtual directory with access

permissions that enable users to run server-side executable programs or scripts stored in the

physical directory associated with the virtual

directory

• Create an application: use the Virtual Directory Creation Wizard and specify on the Access

Permissions page that users can execute scripts

or executable files within the virtual directory

• Application: created for every server-side

compiled program or script on a Web server

• A server-side compiled program or script starts a process that runs in the Web server’s memory

and controls the program’s execution

• Process space: memory area where a process

runs

• The location of a program’s process space is

based on the memory model of its associated

• A memory model

specifies how an environment

stores the data for its processes

in the main memory of a computer

Organizing Your Web Server

• Web administrators organize Web server files by placing them in directories that make the files easier to locate and manage

• These directories enable the administrator to control file access permissions and ensure the security of the Web site

• Many Web administrators organize Web server files by creating separate directories for different types of files

Referencing Files on a Web Server

• Current working directory: contains the Web page that currently appears in the user’s browser

• When objects such as graphic images in a Web page are referenced, either

– the object file must be placed in the same directory

as the Web page or

– an absolute or relative file path must be specified

to the object file

Absolute URL Addresses

• Absolute URL address specifies:

– Web server IP address or domain name

– Complete path or virtual directory path to the Web

page file, and

– Name of the Web page file

• Absolute URL address

– can be placed in a browser’s Address field

– in a hyperlink tag to specify the location of a Web

page file or

Absolute URL Addresses

Figure 5-19 shows absolute URL addresses

Relative URL Addresses

• Relative URL address:

– Location of a file relative to the current working

directory

– Can be used to specify files stored in physical

directories on the Web server

• A file that is in a physical directory within the

current working directory is referenced by typing the physical directory name, a front slash (/), and then the filename, using the following syntax:

Relative URL Addresses

• A file that is in the parent directory of the current working directory is referenced by specifying the parent directory using two periods ( ) followed by

a front slash (/), using the following syntax:

/filename

Factors Impacting Web Site

Performance

• Users of Web sites frequently experience delays while waiting for their browsers to display the

pages they request

• Factors in response time include:

– Speed of the Web server’s network connection

– Amount of main memory that the Web server's

administrator allocates to process Web page

requests

– Web server's processor speed

Factors Impacting Web Site

Performance

• Factors in response time include (continued):

– Number of other visitors currently requesting

pages or files from the Web site

– Size of Web page files and their embedded

graphics objects

– Server resources required to execute Web-based

programs and scripts in Web pages

Factors Impacting Web Site

• Web administrators should always assume that visitors will have fairly slow network connections

• Internet Information Services (IIS) includes the IIS console for administering a Web server and the listener process for servicing user requests to a Web server

• A Web server’s home directory is the Web server directory that contains the Web server’s default document

• A physical directory is a folder within the Web server’s file system that is within the home directory, a virtual directory, or an application

• A virtual directory is not necessarily physically within the home directory, but appears to client browsers as though it is

• Applications: virtual directories in which

permissions exist to allow users to run scripts or executable files

• When an object on a Web page is referenced, the referenced object must be in the same physical

or virtual directory as the Web page that currently