2. 20-751 ECOMMERCE TECHNOLOGY FALL 2003 COPYRIGHT © 2003 MICHAEL I. SHAMOS eCommerce Technology 20-751 Lecture 4: Web Architecture

3. 20-751 ECOMMERCE TECHNOLOGY FALL 2003 COPYRIGHT © 2003 MICHAEL I. SHAMOS Client-Server Model INTERNET CLIENT (Often a Web browser) SERVER Client makes requests Server responds

4. 20-751 ECOMMERCE TECHNOLOGY FALL 2003 COPYRIGHT © 2003 MICHAEL I. SHAMOS Two-Tier Architecture SOURCE: FOURNIER TIER 1: CLIENT TIER 2: SERVER Server performs all processing Web Server Application Server Database Server This architecture is obsolete. Server does too much work.

5. 20-751 ECOMMERCE TECHNOLOGY FALL 2003 COPYRIGHT © 2003 MICHAEL I. SHAMOS Three-Tier Architecture TIER 1: CLIENT TIER 2: SERVER TIER 3: BACKEND Application server offloads processing to tier 3 SOURCE: FOURNIER Web Server + Application Server Note: Using 2 computers instead of 1 can result in a huge increase in simultaneous clients. Depends on % of CPU time spent on database access.

6. 20-751 ECOMMERCE TECHNOLOGY FALL 2003 COPYRIGHT © 2003 MICHAEL I. SHAMOS N-Tier Architecture SOURCE: FOURNIER Achieves full separation of function and administration Huge number of simultaneous clients Managed and tuned by DBA Optimized for web page delivery Coded for specific application

7. 20-751 ECOMMERCE TECHNOLOGY FALL 2003 COPYRIGHT © 2003 MICHAEL I. SHAMOS InterShop Architecture SOURCE: INTERSHOP

8. 20-751 ECOMMERCE TECHNOLOGY FALL 2003 COPYRIGHT © 2003 MICHAEL I. SHAMOS Connecting to Legacy Systems by “Wrapping” Web App Web Server Legacy App MAINFRAME “WRAPPER” Wrapper Middleware

9. 20-751 ECOMMERCE TECHNOLOGY FALL 2003 COPYRIGHT © 2003 MICHAEL I. SHAMOS Connecting to Legacy Systems The “screen scraper” Client Web server Legacy database Terminal screen data Screen scraper Existing application HTML data Legacy system (mainframe) SOURCE: WIM GEVERS

10. 20-751 ECOMMERCE TECHNOLOGY FALL 2003 COPYRIGHT © 2003 MICHAEL I. SHAMOS Screen Scraping Some systems produce as their only output commands to 80 x 24 display terminals Sequences of characters telling the terminal to move its cursor and display data, e.g. ^M0238Jan. ^M024416, ^M02482000 displays “Jan. 16, 2000” in row 2, starting at col. 38 Screen scraping involves virtual simulation of the display terminal to retrieve the data Vendors –Intelligent EnvironmentsIntelligent Environments

11. 20-751 ECOMMERCE TECHNOLOGY FALL 2003 COPYRIGHT © 2003 MICHAEL I. SHAMOS Document Repository Office Tool Internet & Web Web Browser Data Warehouse Query Tool Enterprise System ERP Client Information System CRM Client Groupware Database Groupware Client E N T E R P R I S E P O R T A L Content Directory TextMetadata Embedded Services Web ToolsApplications Portal Architecture PartnersEmployees Customers SOURCE: PLUMTREE

12. Portal Architecture SOURCE: MIKE CRANDALL, GATES FOUNDATIONMIKE CRANDALL, GATES FOUNDATION LOB = “LINE OF BUSINESS”

13. 20-751 ECOMMERCE TECHNOLOGY FALL 2003 COPYRIGHT © 2003 MICHAEL I. SHAMOS Server Farms Web Servers App Servers DB Servers Router Intranet Firewall Network Switch Router Internet Firewall Network Switch SOURCE: ATESTO To serve many clients, one server is not enough How do multiple servers cooperate?

14. 20-751 ECOMMERCE TECHNOLOGY FALL 2003 COPYRIGHT © 2003 MICHAEL I. SHAMOS Communication Request Routing Server Cluster (Server Farm) Internet Clients Server farm HTTP request System Management Router SOURCE: CHU-SING YANGCHU-SING YANG

15. 20-751 ECOMMERCE TECHNOLOGY FALL 2003 COPYRIGHT © 2003 MICHAEL I. SHAMOS Server Selection Problem Which network site? Which server? “Contact the weather service.” Server Farm A Server Farm B Avoid scalability problems of central servers by distributing load SOURCE: JEFF CHASE

16. Load Balancing Switch ‧ ‧‧‧‧ ‧ ‧‧‧ ‧‧‧ Internet Web Switch Router Server Farm subnet http://pds.cse.nsysu.edu.tw/job/ SVR.1 SVR.2 SVR.n client Internet subnet Virtual IP address SOURCE: CHU-SING YANGCHU-SING YANG

17. 20-751 ECOMMERCE TECHNOLOGY FALL 2003 COPYRIGHT © 2003 MICHAEL I. SHAMOS Domain Names IP addresses are inconvenient to remember 128.2.218.2 v. euro.ecom.cmu.edu (fully qualified) Domain names are alphanumeric aliases for IP addresses. They form a tree structure of FQDNs: ROOT.GOV.COM.MIL.NET.EDU.ORG.IT CMU PITT MIT AMAZON MCKINSEY YAHOO GSIA CS ECOM HEINZ WWW YEN EURO DOLLAR PESO 207.237.113.94 128.2.218.2 208.216.182.15 128.2.218.4 128.2.16.175

18. 20-751 ECOMMERCE TECHNOLOGY FALL 2003 COPYRIGHT © 2003 MICHAEL I. SHAMOS Domain Name System What is the IP address of abc.foo.com? SOURCE: CISCO SYSTEMS client Local DNS Resolver Try.com Root DNS.com DNS Try foo.com foo.com DNS abc.foo.com is 202.168.14.12 + Cache 202.168.14.12 Large, distributed, worldwide database Maps domain names to IP addresses

19. URL-Based Load Balancing Substring matching for: “images” “.gif” “.jpg” GET/www.foo.com/event/reg.bin GET /www.foo.com/images/abc.gif GET /www.foo.com/product/abc.html Load distributed within group via any standard metric or URL hashing Substring matching for: “.cgi” “.bin” “.exe” Substring matching for: “.html” Servers optimized for specific content-types Substring match on URL directs HTTP requests to designated server farm –Load balancing using configured algorithm or, –URL Hashing forwards requests for each unique URL to same server to take advantage of server memory caching SOURCE: SUN

20. 20-751 ECOMMERCE TECHNOLOGY FALL 2003 COPYRIGHT © 2003 MICHAEL I. SHAMOS DNS Round Robin Balancing “lookup www.nhc.noaa.gov” a DNS server for nhc.noaa.gov bcd client network DNS server “www.nhc.noaa.gov is IP address a” (or {b,c,d}) Idea: When an IP address is requested for nhc.noaa.gov, return a different IP address each time SOURCE: JEFF CHASE SERVER CLIENT

21. Web Data Center SOURCE: SUN

22. 20-751 ECOMMERCE TECHNOLOGY FALL 2003 COPYRIGHT © 2003 MICHAEL I. SHAMOS Global WAN Architecture BIG-IP Server Array Webmaster Site I newyork.domain.com Site III tokyo.domain.com Site II losangeles.domain.com User london.domain.com Local DNS DNS GLOBAL-SITE Router BIG-IP Internet SOURCE: EDWARD CHOWEDWARD CHOW

23. 20-751 ECOMMERCE TECHNOLOGY FALL 2003 COPYRIGHT © 2003 MICHAEL I. SHAMOS Client- and Server Side Programming Client Internet Server HTML Dynamic HTML Applets ActiveX Controls JavaScript CGI/Perl, C XML ASP Servlet JSP SOURCE: IITIIT

24. 20-751 ECOMMERCE TECHNOLOGY FALL 2003 COPYRIGHT © 2003 MICHAEL I. SHAMOS Tiers and URLs Web Server DB Web app http: // 10.0.0.1 / catalog / display.asp ? pg = 1 & product = 7 SOURCE: NTOBJECTIVES.COMNTOBJECTIVES.COM URLs can be used for application routing

25. 20-751 ECOMMERCE TECHNOLOGY FALL 2003 COPYRIGHT © 2003 MICHAEL I. SHAMOS PHP Process Flow Web Server PHP Pre- processor.php source file Browser Internet Request for.php file Raw.php source HTML is substituted for PHP code HTML SOURCE: M. HAMILLM. HAMILL PHP originally mean “Personal Home Page”

26. 20-751 ECOMMERCE TECHNOLOGY FALL 2003 COPYRIGHT © 2003 MICHAEL I. SHAMOS Website Components Web Server DB Web app Web Client Web app HTTP request (cleartext or SSL) HTTP reply (HTML, Javascript, VBscript, etc) Plugins: Perl C/C++ JSP, etc Database connection: ADO, ODBC, etc. SQL Database Apache IIS Netscape etc… Firewall SOURCE: NTOBJECTIVES.COMNTOBJECTIVES.COM

27. 20-751 ECOMMERCE TECHNOLOGY FALL 2003 COPYRIGHT © 2003 MICHAEL I. SHAMOS Major Ideas Client-server model Three-tiered (n-tiered) architecture Legacy connections Portals Server Farms Web development tools Client- and server-side tools

28. 20-751 ECOMMERCE TECHNOLOGY FALL 2003 COPYRIGHT © 2003 MICHAEL I. SHAMOS Q A &