Download - Session 1 Web Servers - WikiEducator · 2008-06-27 · zPNG (Portable Network Graphic) ... V0.1 ISA1-3.PPT File Systems (2) zMicrosoft

© Galatea Training Services Limited, 2002

Web Servers - 1

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Internet SystemsAdministration

Session 1Web Servers


Web Servers - 2

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Contents

Client/Server BasicsElectronic PublishingHTTP OverviewOther Web-Related Servers


Web Servers - 3

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Requests

Services

Clients and Servers


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TCP/IP NetworkConnections/Ports

a.b.c.d

Services

e.f.g.h

Port 80


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Servers and Browsers

request

resourcereturned

browser display


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Browsers Plug-Ins

Extends browser capabilityMore than just HTML

RealPlayer live audio and videoShockwave animationsAcrobat Reader view PDF files


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HypertextHyperlink

Hypertextdocument

Target


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File Types

ASCII text files– Letters number and punctuation– View and edit with standard tools– HTMLBinary files– Images– Sound– Programs


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Image File Types (1)

GIF (Graphics Interchange Format)– 256 colours– Lossless compression– Transparency– Can be animated– Good for illustrations– Proprietary (patent)


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Image File Types (2)PNG (Portable Network Graphic)– As GIF, except

more coloursno animationnot proprietary

JPEG (Joint Photographic Experts Group)– Millions of colours– Lossy compression– Good for photographs


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Audio File TypesWAV– WindowsAIFF– MacintoshAU– UNIX

Modern browsers support all these andmore


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MIME TypesApplication– application/excel

Audio– audio/midi

Image– image/jpeg

Message– message/news

Multipart– multipart/digest

Text– text/html

Video– video/mpeg


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HTTP Request

Request Line

Header Section

Entity Body

Request method,resource location,protocol version

Information aboutrequest, client

Data to be passed to theserver


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HTTP Response

Status Line

Header Section

Entity Body

Status code, reasonphrase, protocol version

Information about server,response

Requested resource –often HTML


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Request MethodsGET– Typical way of getting a resource from a server– Can be used to pass data to the server

HEAD– Server returns only header data– Use to verify the existence of a resource

POST– Used to send data to the server– Typically- send HTML form data to the server


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HTTP Status Code CategoriesInformational

Success

Redirection

Client error

Server error


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Proxy Server

Proxysecuritycontent filtercache

Web server


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Streaming

Data transmitted

continuously

Requestresource

Display withoutwaiting forcompletemessage 13

2


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FTPCopies files from onehost to anotherUsed to retrieve filesfrom Internet archivesUseful for binary andtext filesLog in identification– Anonymous ftp


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SSL

Secure Sockets LayerEncrypts data in TCP/IP packets– ordinary HTTP uses clear textCommercial web applicationsWeb server support


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Summary

We have covered:

– Client/Server Basics

– Electronic Publishing

– HTTP Overview

– Other Web-Related Servers


Planning a Server - 1

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Session 2Planning a Server



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Contents

Hosting OptionsUNIX or NT?Sizing a ServerDomain Names



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Hosting

Host – a computer connected to theInternet with an addressA web server is a host– Where can you locate your web server?– How can you connect your web server to

the Internet?



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Hosting Options

Set up your own web serverCo-locationVirtual hostPersonal-Page sites (ISP)Free-Page sites



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Your Own Server - Issues

Cost of server hardware and softwareOperations –– Backup– 24/7– Power supplies

Security– Protecting your server– Protecting other peoples’ resources



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Internet

Co-Located/Dedicated Server

Low costconnection

ISP’sconnection to

Internet

Develop web pages

Monitor server usage

Your office

ISP

Manages set up,maintenance,

accounting, backupsetc



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Co-Located Server Issues

You must supply the serverYou must administerFees to ISP for serviceBut– Good connectivity to Internet– No local floor-space required



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Dedicated Server Issues

Not your own serverFees to ISP for serviceBut– Much easier to set up– 24/7 support– Good connectivity to Internet



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ISP

Internet

Virtual Host

Low costconnection


Internet

Develop web pages

Monitor server usage

Your office

Shared Server

Own domain

Another Co.

Another Co.



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Virtual Host Issues

Shared serverLimited or no server programmingaccessStandard solutionsBut– Inexpensive– Good connectivity to Internet



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Personal and Free Pages

ISP standard offeringVery limited storageNot for commercial useMay be free with some ISPs



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ISP

Connecting Your Server

InternetIP address

Domain name

Your office

ISDNCableDSL

T1/E1



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IP Addressing

Static IP address– needed for a web server– never changes– allows other domains to connect to your server

Dynamic IP address– different on each dial-up– acceptable for dial-up Internet access– inappropriate for running web based services



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ISP

Internet

Router


Internet

RouterDirects packets to different

networks or to Internetdepending on address



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Servers - UNIX or NT? (1)

Unix– Built for TCP/IP networking– Scaleable– Many hardware platforms– Robust– Command Language Interface– X Windows GUI– Requires longer learning curve



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Servers - UNIX or NT? (2)

NT/XP/Win 2000– Closed - proprietary– Limited hardware platform choice– GUI oriented– Easy to learn– Getting more robust



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Servers- UNIX or NT? (3)

Linux– Open – Free version of UNIX– Works well on limited hardware– Robust– Very versatile– Requires investment in learning– Becoming extremely popular for web

servers



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Sizing Your Server

Bandwidth and network capacity– Moving data from and to your server– Buy a bigger pipeWeb server processor– Serving out web pages fast enough to

keep up with demand– Buy a faster CPU– Add RAM



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Domain Names

www.vortexwidgets.com

Host name Domain Top leveldomain



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Top Level Domains

.com business

.org non-profit

.net ISPs

.edu university

.gov government

.mil military

.us United States

.au Australia

.uk United Kingdom

.jp Japan

.sw Sweden



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Summary

We have covered:

– Hosting Options

– UNIX or NT?

– Sizing a Server

– Domain Names


Users and Documents - 1

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Session 3Users and Documents



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Contents

Server Users and DirectoriesServer AdministratorsDocument HierarchyDirectory IndexingFile and Directory NamesTransferring Files



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Web Servers and Directories

htdocs

usr home bin dev

/

Web server



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Users and Accounts

Web site visitors do not need accountsUser accounts define server privilegesUsers have a home directoryUser name and password



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System Administration Duties (1)

Install and configure server OSSet up daemons/services (UNIX/NT)Install and configure web serverKeep server software up to date– Patches (UNIX)– Service packs (NT)



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System Administration Duties (2)

Backup and recovery– To disk or tape– Full and incremental backups

Accounts and quotas– Maintain users and their accounts– Decide level of resources for users

Network software configurationMonitoring security



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File Systems (1)

usr home bin dev lib etc var

/



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File Systems (2)

Microsoft– FAT/FAT16/FAT32– NTFS

Apple– HFS

UNIX– UFS– EXT2– Reiserfs

– NFS



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Directories

Absolute Pathname/usr/local/httpd/htdocs

Relative pathnamecd /usr/local/httpdcd htdocs

Dot and Dot Dot. = current directory.. = parent directory



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Uniform Resource LocatorsDescribe how to find a web resourcehttp://www.vortexwidgets.com/support/industrial.ht

mlServername: www.vortexwidgets.comPath: supportFilename: industrial.html

Use relative URLs in your own web pages– Make it easy to move to another directory

Dot and Dot Dot. = current directory.. = parent directory



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Directory Indexing

If no file name in a URL:– Directory browsing enabled

If index document, return default documentOtherwise return list of files

– Directory browsing disabledIf index document, return default documentOtherwise return nothing



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Good Filename Practice (1)

Don’t use spaces in names– Use underscores (_) or dash (-) insteadDon’t use special characters& + ?Keep filenames shortUse a standard naming convention



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Good Filename Practice (2)

Use consistent filename extensions.html.gif

Don’t use extensions with directory namesUse lowercase letters in all filenames– UNIX is case sensitive– Windows is (mostly) not case sensitive



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Transferring Files

Development PC

Web Server

HTML editorProgramming tools

Graphics tools

FTPHTTP PUT

FrontPage extensions



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FTP

File Transfer ProtocolUse a GUI FTP client, ORFTP CLI CommandsOpen hostnamePut filenameGet filenameCD directory

LS (list directory)MKDIR dirnameMPUTMGET



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FrontPage

An easy to use HTML editorSynchronisation between developmentPC and web serverBUT– Not all ISPs support this type of usage– Works best with Microsoft web server– Proprietary



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Summary

We have covered:– Server Users and Directories– Server Administrators– Document Hierarchy– Directory Indexing– File and Directory Names– Transferring Files


Server Configuration - 1

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Session 4Server Configuration



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Contents

Choosing web server softwareCustomising your web serverControlling accessSecure Socket Layer configurationVirtual hosts



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Popular Web ServersApache

Microsoft IIS

NetscapeEnterpriseServerOthers



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Apache

Open SourceMultiple platforms (UNIX and Microsoft)Very powerful and configurableUses configuration fileshttpd.conf



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Microsoft IIS

Easy to use, GUI orientedClosed - proprietaryMicrosoft Management ConsoleExtendable through ISAPI– DLL– ASPSupport for FrontPage extensions



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Evaluating Web Servers

Performance Benchmarks– SPECweb96/99– WebStone

CostEase of use or installationScalabilitySecuritySupport of industry standards



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Apache Configuration

All configuration through configuration filesDirectives define optionsDirectives are organised into sections:– Directory– DirectoryMatch– Files– FilesMatch– Location– LocationMatch



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IIS ConfigurationIP addressTCP portHome directoryExecuteVirtual directoryDefault documentDirectory browsingAuthentication controlApplication mappingsRedirect to URL



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Controlling Access

UNIX modelFile permissions– User, Group, Other– Read, Write, Execute

In any combination per file– and directory



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HTTP Authentication

Protect specific files and directoriesRequire User Name and PasswordHTTP1.1– Basic authentication

no encryption across network– Digest authentication

uses MD5 encryption



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Server

Secure Socket Layer

Port443

?

HTTPS

HTTP using SSL



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Certificates

Supplies information about your siteCertificate Authority issues–Verisign–ThawteHelps user trust a transaction withyour serverCosts?



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Virtual Hosts (1)

Name1

Name 2

Name 3



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Virtual Hosts (2)

Name based– One IP address, multiple names– Web server distinguishes using hostnameIP address based– Multiple IP addresses (and names)– Not all servers support this



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Summary

We have covered:

– Choosing web server software

– Customising your web server

– Controlling access

– Secure Socket Layer configuration

– Virtual hosts


Server-Side Programming - 1

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Session 5Server-Side Programming



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Contents

Dynamic DocumentsCGI and FormsServer-Side IncludesActive Server PagesServlets and Java Server Pages



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Normal HTML is static– only changes when you edit it

Some web sites need to present informationthat changes rapidlySome web sites need to process datareceived from visitorsServer-Side Programming meets thisrequirement

WHY Server-Side Programming?



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The CGI Process

user program

user requests a form

field parameters passed

HTML results returned

g a t e w a y

server sends HTML

browser

browser requests URL

form display

form filled browser sends fields

server HTML response response displayed

web server



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CGI Scripting - Perl



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CGI Form



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CGI Form HTML



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Server-Side Includes

Not all web sites need CGIA small amount of data needs to bedynamicGet the server to fill this inUse special tags in HTML– Directives– Interpreted and replaced with data by the

server



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Server-Side Includes



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Typical Server-Side Includes

INCLUDE– Includes a file or a URL at this position– Useful for maintaining a common look and feel

EXEC– Execute a program and insert output at this

positionECHO– Insert the value of a variable at this position



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Active Server Pages

Microsoft proprietary scriptinglanguageEmbed scripts into documentsServer process scripts– issues ‘pure’ HTMLUse any language that supports COM– VBScript, Jscript, C++, Perl, Java



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ASP Example

generates



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Servlets and Java Server Pages

Sun Microsystems Java Language– a well designed language– suitable for both client and server side

programmingServlets – Java programs executed bythe serverJava Virtual Machine (JVM)– Interprets Java code



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Typical Java Code



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Java Server Pages

Simpler than a full servletSimilar to SSIExample:

<HTML>Today’s date is <%= new Date() %></HTML>

Code between <% %> is executed by server



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Java Beans

A component modelWritten in JavaBuilding block for an applicationCan be used to provide commonfunctionality wherever requiredSimilar in principle to MicrosoftActiveX controls



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Summary

We have covered:

– Dynamic Documents

– CGI and Forms

– Server-Side Includes

– Active Server Pages

– Servlets and Java Server Pages


Log Files - 1

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Session 6Log Files


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Contents

Log File FormatsReferrersBeing ProactiveStatistics


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Provide a lot of informationabout the usage of your website

You can log any transaction

Debug server-side programs

Help you tune your web site

Log Files


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Logging Transactions

One line per transactionNot computationally expensiveCan grow very large– Store on a separate partition– Rotate log filesTwo main logging formats– Common Logfile Format (CLF)– Extended Logfile Format (ELF)


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Common Logfile Formatremotehost rfc1413 authuser [date] “request” status bytes

remotehost – client hostname or IP addressrfc1413 – the identity of the remote user (usually -)authuser – users own name (may be -)[date] – date and time of requestrequest – the HTTP request as it came from clientstatus – the HTTP status code returned by the serverbytes – the content length of the returned document


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Combined Logfile Format

referrer – the URL that brought the user to thisresourceuser-agent – the client that made the request– i.e Netscape 4.5)

remotehost rfc1413 authuser [date] “request” status bytes referer user-agent


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Extendible Logfile FormatAllows the administrator to specify thefields to be loggedExample:


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ReferrersHow did visitors reach your web site?What web page were they previouslyviewing?Understanding referrers helps you tomake your web site more accessible


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ReferrersVisitor uses a search engine to look for“vortex widgets”The referrer field might contain:


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Example Error Diagnosis (1)

Error is inline 7

As a resultthe form did

not work


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Example Error Diagnosis (2)Error is in

line 7Web serveris deniedaccess

Userdeniedaccess


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Statistics

Getting information from dataUnderstand usage patterns for yourweb siteObtain “hit counts”Tune your web site to attract moreusers


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Log File Analysis

Most requested pagesTop entry pagesMost used browsersBandwidth utilisationMost active domainsInformation about search enginesTop referring sites and URLsError counts


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StatisticsYou need tools to extract statisticsfrom logsWebalizer– http://www.mrunix.net/webalizerWebTrends– http://www.webtrends.comWusage– http://www.boutell.com/wusage


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Using Webalizer (1)Usage Statistics for www.mrunix.netSummary Period: Last 12 MonthsGenerated 23-Oct-2000 02:17 EDT


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Using Webalizer (2)

Summary by Month

MonthDaily Avg Monthly Totals

Hits Files Pages Visits Sites KBytes Visits Pages Files HitsMay 1999 6377 5570 903 455 10484 884568 14119 28004 172671 197696Apr 1999 6216 5394 858 419 10087 821968 12594 25758 161844 186504Mar 1999 7530 6582 1046 499 12128 1052978 15480 32432 204059 233445Feb 1999 4712 4128 656 321 6629 511793 8048 16419 103203 117816Jan 1999 4470 3934 607 284 8079 605694 8808 18844 121980 138571Dec 1998 2998 2673 411 197 6524 410110 6120 12769 82875 92951Nov 1998 2910 2567 400 192 4260 346705 5588 11627 74468 84403Oct 1998 3052 2668 457 202 2203 189253 2839 6399 37360 42738Sep 1998 2072 1826 345 169 3475 314492 5075 10376 54807 62165Aug 1998 1014 901 211 125 2693 196560 3890 6571 27958 31455Jul 1998 1484 1325 302 184 4041 298225 5716 9383 41102 46019Jun 1998 1707 1502 322 222 4809 251502 6675 9687 45077 51227Totals 5883848 94952 188269 1127404 1284990


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Summary

We have covered:– Log File Formats

– Referrers

– Being Proactive

– Statistics


Search Engines, Robots & Automation - 1

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Session 7Search Engines, Robots and

Automation



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Contents

Search EnginesPublicising your siteRobots and SpidersAutomation



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Objectives

How to increase usage of your siteHow to enhance itHow to publicise itHow your site interacts with searchengines



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Search Engines

How can users find content within your site?Navigation bar or table of contents– simple but slow

A web site based search engine– greatly increases usefulness of your web site– easy to install– offers other useful features



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Search EnginesExcite for Web Servers (EWS)– http://www.excite.com/navigate/

SWISH-E (Simple Web Indexing System forHumans –Enhanced)– http://sunsite.berkeley.edu/SWISH-E/

AltaVista search Intranet– http://www.altavista-software.com/

Microsoft Index Server– http://www.microsoft.com/NTServer/fileprint/exec/feature

/Indexfaq.asp



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Example – SWISH



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Virtual Search Engine

Use an existing high capacity search engine– Infoseek

Filter out all hits except those for your websiteNo cost, no disk space, minimal effortBUT– Only if your site is properly indexed by the

search engine



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Installing a Search Engine

Indexing your site

Search Form

Search Engine



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Publicising Your Site

Use tags well<META>

– Use keywords to describeyour site and capture hits

<TITLE>,<H1>,<H2>– Search engines look at these



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Publicity Tips

Register with the major search engines anddirectories– Search engines match key words– Directories match topics– Metasearch engines use other search engines

Content needs to be useful/interestingAdvertise your siteFind sites that will link to yours



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Controlling the Robotsand Spiders

By default robots visit everypage of your siteThis may be what you want,but:– what about dynamic content?– what if you have too many

matching keywords?Use a robot exclusion protocol



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Robots.txt

Specify whichrobots arecontrolled

Specify whichdirectories are

not allowed



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AutomationSystem administratorshave a lot ofresponsibility– managing disk space– checking for errors in the

logs– generating reports– performing backups

Scripts can automatemost of these



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UNIX Tools (1)UNIX has strong tools andscripting languagesCRON– Daemon that starts programs

according to a schedule– Crontab creates list of tasks

AT– Run a command at a future

time– Windows NT has a version of

AT



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UNIX Tools (2)Perl, Tcl– very powerful, easy to use

scripting languagesShell scripts– csh, ksh, etc– files containing OS commands and

programming featuresExpect– automation of command-line tasks

where there is user interaction inresponse to system prompts



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Summary

We have covered:

– Search Engines

– Publicising your site

– Robots and Spiders

– Automation