Internet / Intranet

CIS-536

Class 10

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Class 10 Agenda

Milestone#4 - DiscussionPresentationsCookiesMisc. TopicsWireless Devices: WAP / WMLWrap-Up

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Cookies Revisited

Cookies Are Name Value Pairs Passed in the HTTP HeaderCookies Have Associated Expiration

Session (Default)Date / Time

Associated With a URL Path, Not a Page!Allows Passing Parameters Between Web Pages

Thus Cookies are Used to Provide State Information to a Stateless Protocol

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Cookie Jar

Cookie Storage Internet Explorer c:\windows\cookies Each Has its Own FileNetscape Navigator cookies.txt (all kept in the file)

Limits20 Cookies4K Per Name/Value Pair

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More Cookies Cookies are Traditionally Set By Server

Set-CookieBrowser is Responsible For Maintaining Them

Stored On Client’s ComputerPassed to Server When Web Site is Revisited

HTTP-CookieCookie Attributes

Name – The Name of the CookieSubsequent References to Same Name Overwrites Cookie Attributes

Value – The Value of the Cookie Identified by NameExpiration – When the Cookie Expires

No Date Specified – Cookie Expires at End of SessionPast Date/Time – Delete the CookieFuture Date/Time – Delete the Cookie After This Date

Example

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Cookie Bits

Example CookieSet-Cookie: tollhouse=favorite;expires=Thursday, 16-Mar-2000 00:00:00 GMT;path=“”

Note That Date Must Follow This Format:Weekday, DD-MMM-YYYY HH:MM:SS GMT

RFCs specify GMT as the mechanism for handling time problems on the InternetHTTP-Cookie Only Sends Name/Value Pair

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Cookies - JavaScript

Cookies Can be Set in JavaScriptdocument.cookie = “ “Use Date.toGMTString() to set expiration dateE.g.

document.cookie = “version=1.0; ” + “expires=“ + edate.toGMTString();

To Read a Cookie Value in JavaScriptvar allcookies= document.cookie;var pos = allcookies.indexOf(“version=“);if (pos != -1) {

var start = pos +8; var end = allcookies.indexOf(“;”,start);if (end == -1) end = allcookies.length;var value = allcookies.substring(start,end);vervalue = unescape(value);

}

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Cookie Structure

Path InformationDefault is to Send Cookie to Any URL in the Same Directory or any Subdirectory of the Page Which Set CookiePath Attribute Can Request That Cookie Be Sent to All URLs in Path (and its Subdirectories)

Only Paths That are a Prefix of Current URL are AllowedIf Cookies Overlap, All are Sent.

Ordered by Most Specific to Least Specific MatchDomain Attribute – Allows Cookies to Be Shared Across Sites

Must Be Part of Same DomainE.g. boston.brandeis.edu and lab.brandeis.edu are part of the same domain but may be different servers

Secure – Only Sends Cookie If Secure Protocol is Used (e.g. SSL)

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Security Issues

Protections:Cookie Can Only Store Information Already Known to Server

Can’t Access Hard Disk, etc.

Data Only – Not Executed by Client MachineData Can’t Be Shared Across Sites

Concerns:Of Course This Assumes That Browser Follows the RulesBrowser Can Store Sensitive Information

E.g. If Server Doesn’t Set Secure Tag, a Credit Card # May Be Passed in Clear to Another Page in Same Path

“Invisible” to UsersPaths Are Not Always Obvious

E.g. Multiple Sites Receive Graphics From DoubleClick Server

DoubleClick Can Now Gather “Cross-Site” Information

Zealous privacy folks advocate turning off cookies

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Performance Tuning / Testing

Performance ImprovementsServer Scripting, etc. Degrades Server Performance

Minimize Reliance on Server Scripting“Compile” Frequently Used Documents

Increase CPU, Disk, Caching, Internet PipeMultiple Servers (Basic)

Distribute Pages Across Servers

Multiple Servers (Advanced)Route Requests to Multiple ServersRound Robin DNS

DNS Server Returns a Different IP Address Each Time

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Web Robots

Spiders, Crawlers, and Bots, Oh My!Programmatically Visit and “Analyze” Web Sites

Gather Information From The SiteTypically as Data For Search EnginesValidate Links For Currency

Follow Links

Robot Protocol (Voluntary)robots.txt – In top-level Directory of a Site

User-Agent: Names of Robots or *Disallow: Parts of Hierarchy to Disallow or /

<META Name=“Robots” Content=“NoIndex, NoFollow”>

Or Index, Follow – Tells Robot Whether or Not to Index Site, Follow Links

User-Agent Typically Identifies RobotAccesses to robot.txt

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Building Web Robots

Issues When Building a RobotFollow Web Exclusion RulesParsing

Ability to Parse HTML For Target Info. Identify Links.

IterationSearch Strategies:

Breadth FirstDepth First

Avoid Endless LoopsDon’t Revisit Links Already Visited

Don’t Follow Outside Links?

TerminationDepth, Sites Visited, Time, High Proportion of Duplicate Links

Tools For Bulding RobotsJavaScriptVB 6 – Internet Transfer Control and Web Browser ControlOthers

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Trends toward smaller devices

Moore’s lawHistory of Computers

trend toward smaller devicestrend toward cheaper devices

processors in more and more devicesTCP/IP can expand well beyond PCs5 year time frame ( Gartner Group )

a billion mobile phones ( US lags behind Europe and Asia )over half of Internet access through non-PCsM-Commerce replaces E-Commerce

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Wireless Internet

HDML - 1995Handheld Device Markup Languagesubset of HTML

I-mode - Japanuses a tag language based on HTMLcHTML7 million users

WAP/ WMLcurrently at 1.3 ( 1.1 widely supported )protocol extends Internet to Phonesspecialized for smaller screens

GPRS general packet radio switching

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Wireless ‘Non-Internet’

continued investment - limited commercial successBluetooth

develop a wireless standard for all devices

low earth orbit satellites must be in low orbitbig time failures (Iridium, Globalstar) - Teledisic ?? ( Bill Gates and Craig McCaw )

Many premature predictions about wireless1993 was supposed to be the year of wirelessissues of latency, reliability, security, processing power

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WAP Application Architecture

WAP Gatewaysconnect Wireless Messages with Internet

Leverage the Internet plumbing Wireless requested converted to HTTP

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WAP Gateways

Implement WAP protocol stack layersaccount for security and sessions

convert WSP -> HTTPEncodes HTTP heads as binary tokens

Domain Name ResolutionHTML to WML conversion

limited success so far

encode WML contentSecurityCache frequently accessed content

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WAP Gateways

offered by all major vendorsNoikaMotorolaEricsson

Kannel ( Open-Source WAP Gateway )

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WAP Protocol Stack

derived from the OSI Reference ModelApplication Layer ( WAE )Session Layer ( WSP )Transaction Layer ( WTP )Security Layer ( WTLS )Transport Layer ( WDP )Bearers (SMS, CSD, USSD, CDMA, CDPD .. Others )

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Phone emulators

Simulate phone usage ( see example )not perfect approximation

used to develop wireless applicationsNoika WAP Toolkit

image support

Phone.Com ( UP.Simulator )EricsonMotorola

VoxML ( precedes VoiceXML )

host of other toolsMicrosoft Mobile Explorer

provide a useful tool for test/debug cyclesstill at the early stages

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WAP Devices

limited processing powerlimited RAMembedded Browsers

do not behave the samecache requests

emulators simulate ( do not forget to clear )lots of latency

currently 9600 bits per secondversus 56 kilo bits per second wired

Deja-vu for programmersback to 64K barriersmachine code

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Configuring Servers for Wireless

add MIME types (.htaccess in Apache, IIS Registry)

wml - text/vnd.wap.wmlwlmc - application/vnd.wap.wmlc.wmls - text/vnd.wap.wmlscriptwmlsc - application/vnd.wap.wmlscriptcwbmp - image/vnd.wap.wbmp

Shore.net Apache server supports wmlCall server scripts within documents same as before

support for CGI/PerlCold FusionJSP/ASP

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WML

designed for small displaysdeck of cards metaphor

replaces <BODY> concept

XMLall docs need an XML declaration and DTDall documents must be well formedText Formating

<p> </p> used for all text<br/> breaks textsupport for styles

Bold <b></b>Italitic <I></I>

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WML

anchor tags wrap links same as HTML<go> tag indicates action when link is selected# used to select other cards in the deckWML Input<input name =“var” > tagvariables then displayed with ‘$’ delimiter

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More WML

<prev> tag sends the user back to the previous document<do> associates an action with a given element<do type=“prev” label=“Previous”>

<prev/>

</do>Creates a Previous operation for a softkey<select> element

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Wireless Scripting

WMLScript - based on ECMAscriptuseful for validation

WML tags support eventstimerscard supports three main events

onenterforwardonenterbackwardonTimer

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WML GET/POST request

WML supports HTTP Get & PostGET Request

append data as parameter to the URLuse WMLScript

POST Requestspecify as an attribute in the <go> tag<go method=“post” href=“somescript.pl”>

<postfield name=“product” value=“$(product)”/>

</go>

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WML Images

wireless bitmaps (WBMP)monochromeinitially needed to convert bits in GIF and JPG filestools are emerging

Nokia toolkit supportsplug-ins exist for most major tools ( Photoshop, Paintshop)

watch out for latency !!!Large bitmaps

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Usability

Terse documentsWML apps need to deliver bullet pointsshort text labelsminimize data entrysites need high personalization

NOT the Internet on a cell-phoneNew applications will be createdStill significant browser differences

tags do not work in a uniform waysignificant differences in screen size

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WAP Resources

WAP FAQ http://www.wap.comWAP forum http://www.wapforum.orgProfessional WAP ( Wrox Press )

ISDN 1-861004-04-4

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Presentations

Mirrors Real Life SituationsCoWorkers, Audience Have Different BackgroundsRelevance to Audience Varies

Some With Lots of Experience – Want DetailsManagement vs. Technical PersonnelStrategy:

Give Enough Background to Identify Key IssueMost Will File it Away for Future Reference

Identify Target AudienceGive “Meaty” Info

Be Judicious With TimeCan’t Cover Everything

Provide Reference MaterialThose Who Want to Learn More CanMost Will Want Info at Some Point in Future

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Career AdviceSoftware Engineering Growth Paths

Require Ability to Bridge Gap Between Management and Technical

Management Concerned With Practical Implications, Not Technical Details

TechnicalKnowledge and Ability to Implement Task

“Political”Different Personalities Have Different Expectations

Valuable SkillsTechnical KnowledgeCustomer RequirementsDevelopment Schedule / Quality / Maintenance / Cost MentorshipCommunication

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Wrap-Up

Ongoing Resource: evan@mkat.comGeneral QuestionsJobs, etc.

Grading

ShoreNet AccountsClass Web SiteEnjoy Your Break!