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Internet / Intranet Fall 2000

Internet / Intranet Fall 2000. Class 10. Class 10 Agenda. Milestone#4 - Discussion Presentations Cookies Misc. Topics Wireless Devices: WAP / WML Wrap-Up. Cookies Revisited. Cookies Are Name Value Pairs Passed in the HTTP Header Cookies Have Associated Expiration Session (Default)

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Internet / Intranet Fall 2000

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  1. Internet / IntranetFall 2000 Class 10

  2. Class 10 Agenda • Milestone#4 - Discussion • Presentations • Cookies • Misc. Topics • Wireless Devices: WAP / WML • Wrap-Up Brandeis University Internet/Intranet Spring 2000

  3. Cookies Revisited • Cookies Are Name Value Pairs • Passed in the HTTP Header • Cookies 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 Brandeis University Internet/Intranet Spring 2000

  4. Cookie Jar • Cookie Storage Internet Explorer c:\windows\cookies Each Has its Own FileNetscape Navigator cookies.txt (all kept in the file) • Limits • 20 Cookies • 4K Per Name/Value Pair Brandeis University Internet/Intranet Spring 2000

  5. More Cookies • Cookies are Traditionally Set By Server • Set-Cookie • Browser is Responsible For Maintaining Them • Stored On Client’s Computer • Passed to Server When Web Site is Revisited • HTTP-Cookie • Cookie Attributes • Name – The Name of the Cookie • Subsequent References to Same Name Overwrites Cookie Attributes • Value – The Value of the Cookie Identified by Name • Expiration – When the Cookie Expires • No Date Specified – Cookie Expires at End of Session • Past Date/Time – Delete the Cookie • Future Date/Time – Delete the Cookie After This Date Example Brandeis University Internet/Intranet Spring 2000

  6. Cookie Bits • Example Cookie • Set-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 Internet • HTTP-Cookie Only Sends Name/Value Pair Brandeis University Internet/Intranet Spring 2000

  7. Cookies - JavaScript • Cookies Can be Set in JavaScript • document.cookie = “ “ • Use Date.toGMTString() to set expiration date • E.g. document.cookie = “version=1.0; ” + “expires=“ + edate.toGMTString(); • To Read a Cookie Value in JavaScript var 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); } Brandeis University Internet/Intranet Spring 2000

  8. Cookie Structure • Path Information • Default is to Send Cookie to Any URL in the Same Directory or any Subdirectory of the Page Which Set Cookie • Path 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 Allowed • If Cookies Overlap, All are Sent. • Ordered by Most Specific to Least Specific Match • Domain Attribute – Allows Cookies to Be Shared Across Sites • Must Be Part of Same Domain • E.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) Brandeis University Internet/Intranet Spring 2000

  9. Security Issues • Protections: • Cookie Can Only Store Information Already Known to Server • Can’t Access Hard Disk, etc. • Data Only – Not Executed by Client Machine • Data Can’t Be Shared Across Sites • Concerns: • Of Course This Assumes That Browser Follows the Rules • Browser 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 Users • Paths 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 Brandeis University Internet/Intranet Spring 2000

  10. Performance Tuning / Testing • Performance Improvements • Server Scripting, etc. Degrades Server Performance • Minimize Reliance on Server Scripting • “Compile” Frequently Used Documents • Increase CPU, Disk, Caching, Internet Pipe • Multiple Servers (Basic) • Distribute Pages Across Servers • Multiple Servers (Advanced) • Route Requests to Multiple Servers • Round Robin DNS • DNS Server Returns a Different IP Address Each Time Brandeis University Internet/Intranet Spring 2000

  11. Web Robots • Spiders, Crawlers, and Bots, Oh My! • Programmatically Visit and “Analyze” Web Sites • Gather Information From The Site • Typically as Data For Search Engines • Validate 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 Robot • Accesses to robot.txt Brandeis University Internet/Intranet Spring 2000

  12. Building Web Robots • Issues When Building a Robot • Follow Web Exclusion Rules • Parsing • Ability to Parse HTML For Target Info. Identify Links. • Iteration • Search Strategies: • Breadth First • Depth First • Avoid Endless Loops • Don’t Revisit Links Already Visited • Don’t Follow Outside Links? • Termination • Depth, Sites Visited, Time, High Proportion of Duplicate Links • Tools For Bulding Robots • JavaScript • VB 6 – Internet Transfer Control and Web Browser Control • Others Brandeis University Internet/Intranet Spring 2000

  13. Trends toward smaller devices • Moore’s law • History of Computers • trend toward smaller devices • trend toward cheaper devices • processors in more and more devices • TCP/IP can expand well beyond PCs • 5 year time frame ( Gartner Group ) • a billion mobile phones ( US lags behind Europe and Asia ) • over half of Internet access through non-PCs • M-Commerce replaces E-Commerce Brandeis University Internet/Intranet Spring 2000

  14. Wireless Internet • HDML - 1995 • Handheld Device Markup Language • subset of HTML • I-mode - Japan • uses a tag language based on HTML • cHTML • 7 million users • WAP/ WML • currently at 1.3 ( 1.1 widely supported ) • protocol extends Internet to Phones • specialized for smaller screens • GPRS general packet radio switching Brandeis University Internet/Intranet Spring 2000

  15. Wireless ‘Non-Internet’ • continued investment - limited commercial success • Bluetooth • develop a wireless standard for all devices • low earth orbit satellites • must be in low orbit • big time failures (Iridium, Globalstar) - • Teledisic ?? ( Bill Gates and Craig McCaw ) • Many premature predictions about wireless • 1993 was supposed to be the year of wireless • issues of latency, reliability, security, processing power Brandeis University Internet/Intranet Spring 2000

  16. WAP Application Architecture • WAP Gateways • connect Wireless Messages with Internet • Leverage the Internet plumbing • Wireless requested converted to HTTP Brandeis University Internet/Intranet Spring 2000

  17. WAP Gateways • Implement WAP protocol stack layers • account for security and sessions • convert WSP -> HTTP • Encodes HTTP heads as binary tokens • Domain Name Resolution • HTML to WML conversion • limited success so far • encode WML content • Security • Cache frequently accessed content Brandeis University Internet/Intranet Spring 2000

  18. WAP Gateways • offered by all major vendors • Noika • Motorola • Ericsson • Kannel ( Open-Source WAP Gateway ) Brandeis University Internet/Intranet Spring 2000

  19. WAP Protocol Stack • derived from the OSI Reference Model • Application Layer ( WAE ) • Session Layer ( WSP ) • Transaction Layer ( WTP ) • Security Layer ( WTLS ) • Transport Layer ( WDP ) • Bearers (SMS, CSD, USSD, CDMA, CDPD .. Others ) Brandeis University Internet/Intranet Spring 2000

  20. Phone emulators • Simulate phone usage ( see example ) • not perfect approximation • used to develop wireless applications • Noika WAP Toolkit • image support • Phone.Com ( UP.Simulator ) • Ericson • Motorola • VoxML ( precedes VoiceXML ) • host of other tools • Microsoft Mobile Explorer • provide a useful tool for test/debug cycles • still at the early stages Brandeis University Internet/Intranet Spring 2000

  21. WAP Devices • limited processing power • limited RAM • embedded Browsers • do not behave the same • cache requests • emulators simulate ( do not forget to clear ) • lots of latency • currently 9600 bits per second • versus 56 kilo bits per second wired • Deja-vu for programmers • back to 64K barriers • machine code Brandeis University Internet/Intranet Spring 2000

  22. Configuring Servers for Wireless • add MIME types (.htaccess in Apache, IIS Registry) • wml - text/vnd.wap.wml • wlmc - application/vnd.wap.wmlc. • wmls - text/vnd.wap.wmlscript • wmlsc - application/vnd.wap.wmlscriptc • wbmp - image/vnd.wap.wbmp • Shore.net Apache server supports wml • Call server scripts within documents same as before • support for CGI/Perl • Cold Fusion • JSP/ASP Brandeis University Internet/Intranet Spring 2000

  23. WML • designed for small displays • deck of cards metaphor • replaces <BODY> concept • XML • all docs need an XML declaration and DTD • all documents must be well formed • Text Formating • <p> </p> used for all text • <br/> breaks text • support for styles • Bold <b></b> • Italitic <I></I> Brandeis University Internet/Intranet Spring 2000

  24. WML • anchor tags wrap links same as HTML • <go> tag indicates action when link is selected • # used to select other cards in the deck • WML Input • <input name =“var” > tag • variables then displayed with ‘$’ delimiter Brandeis University Internet/Intranet Spring 2000

  25. 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 Brandeis University Internet/Intranet Spring 2000

  26. Wireless Scripting • WMLScript - based on ECMAscript • useful for validation • WML tags support events • timers • card supports three main events • onenterforward • onenterbackward • onTimer Brandeis University Internet/Intranet Spring 2000

  27. WML GET/POST request • WML supports HTTP Get & Post • GET Request • append data as parameter to the URL • use WMLScript • POST Request • specify as an attribute in the <go> tag • <go method=“post” href=“somescript.pl”> • <postfield name=“product” value=“$(product)”/> • </go> Brandeis University Internet/Intranet Spring 2000

  28. WML Images • wireless bitmaps (WBMP) • monochrome • initially needed to convert bits in GIF and JPG files • tools are emerging • Nokia toolkit supports • plug-ins exist for most major tools ( Photoshop, Paintshop) • watch out for latency !!! • Large bitmaps Brandeis University Internet/Intranet Spring 2000

  29. Usability • Terse documents • WML apps need to deliver bullet points • short text labels • minimize data entry • sites need high personalization • NOT the Internet on a cell-phone • New applications will be created • Still significant browser differences • tags do not work in a uniform way • significant differences in screen size Brandeis University Internet/Intranet Spring 2000

  30. WAP Resources • WAP FAQ http://www.wap.com • WAP forum http://www.wapforum.org • Professional WAP ( Wrox Press ) • ISDN 1-861004-04-4 Brandeis University Internet/Intranet Spring 2000

  31. Presentations • Mirrors Real Life Situations • CoWorkers, Audience Have Different Backgrounds • Relevance to Audience Varies • Some With Lots of Experience – Want Details • Management vs. Technical Personnel • Strategy: • Give Enough Background to Identify Key Issue • Most Will File it Away for Future Reference • Identify Target Audience • Give “Meaty” Info • Be Judicious With Time • Can’t Cover Everything • Provide Reference Material • Those Who Want to Learn More Can • Most Will Want Info at Some Point in Future Brandeis University Internet/Intranet Spring 2000

  32. Career Advice • Software Engineering Growth Paths • Require Ability to Bridge Gap Between Management and Technical • Management • Concerned With Practical Implications, Not Technical Details • Technical • Knowledge and Ability to Implement Task • “Political” • Different Personalities Have Different Expectations • Valuable Skills • Technical Knowledge • Customer Requirements • Development Schedule / Quality / Maintenance / Cost • Mentorship • Communication Brandeis University Internet/Intranet Spring 2000

  33. Wrap-Up • Ongoing Resource: evan@mkat.com • General Questions • Jobs, etc. • Grading • ShoreNet Accounts • Class Web Site • Enjoy Your Break! Brandeis University Internet/Intranet Spring 2000

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