Announcements Networking, URLs, and Due dates extended! Labs 2 and - PDF document

Announcements Networking, URLs, and  Due dates extended!  Labs 2 and 3 due Monday 10pm Pathnames  Continuation of Networking postponed until Monday until Monday Internet and WWW Servers serve Servers  Servers store and serve resources:  One computer can serve many things  Emails—gmail  Windows Vista have server software built in to share  Files—dante and homer  Files, printers, over LAN  Files, printers, over LAN  Web pages—vergil and ovid Web pages vergil and ovid  Other server software  Printing  Windows Server 2008  Databases—available to other computers on the network Servers Server  One computer serves many things—  Servers fit into racks files, printing, email, and database…  One dedicated computer serves one thing thing  One computer serves files  One computer serves Web pages  One computer serves email 1

Servers Server farm  Empty rack Domain Name System DNS  Translates domain name to ip address  Network Solutions tracks top-level domains  Every domain name has to be unique  Any huge company with hundreds of  Network Solutions maintains the list thousands of IP addresses and host thousands of IP addresses and host  Private company names wants to maintain its own domain  Central database is the whois directory name server for their domain.  Several dozen registrars work with  Countries probably wants to administrate Network Solutions to add names to the their top-level domain list DNS The DNS process  Solution:  You click link, sending http request to Web browser for our course Web site.  distributed database  Huge companies own their own DNS  Browser contacts its name server and servers and they are in charge of servers and they are in charge of says "I need for you to convert a domain says, I need for you to convert a domain maintaining them name to an IP address for me."  Microsoft can change the database for its  The name server may already know the domain whenever it wants to because it owns its domain name servers. IP address for our web site if another  Every domain has a domain name server request to resolve it came in recently somewhere that handles its requests. A person (name servers cache IP addresses to maintains the records in that DNS. speed things up). 2

DNS Process (continued) Client/Server Interaction  If not cached For Web pages, the client requests a  Name server contacts first listed root name page, the server returns it servers . The root servers know the IP • Two separate transmissions address for all of the name servers that h handle the top-level domains. Your name dl th t l l d i Y server would ask the root for our Server Client Server Server Client Client courses.washington.edu name, and the root request Server Client Server Client would say (assuming no caching), "I don't reply know the IP address for that, but here's the Server Server Client Client Server Client IP address for the EDU name server."  If unknown, it contacts the next root server D.A. Clements, MLIS, Information Servers serve many clients; clients visit many servers 10/9/2009 School 14 Internet World Wide Web  Internet is all the wires, routers, World Wide Web is the collection of gateways, servers—all using TCP/IP to servers & the Web pages they store and transfer packets serve  Server  Server—the Web site computer the Web site computer  Many different protocols use the Internet  Many different protocols use the Internet  Client—the surfer’s browser  ftp, smtp, chat, IM, Skype, VoIP, http  www—the traditional Web server name  Any name is OK  Often multiple server names map to the same site: MoMA.org and www.MoMA.org D.A. Clements, MLIS, Information 10/9/2009 School 15 16 HTTP HTTP  H yper T ext T ransfer P rotocol  Understands how to interpret URLs  Uniform Resource Locators  Uniform Resource Locators  Divides URL into server and pathname http://faculty.washington.edu/daclem/fit100/sp09/index.html PROTOCOL (Web) 3

HTTP HTTP Read Right to Left http://faculty.washington.edu/daclem/fit100/sp09/index.html http://faculty.washington.edu/daclem/fit100/sp09/index.html PROTOCOL SERVER PROTOCOL PROTOCOL SERVER HTTP HTTP Read Right to Left Read Right to Left http://faculty.washington.edu/daclem/fit100/sp09/index.html http://faculty.washington.edu/daclem/fit100/sp09/index.html PROTOCOL PROTOCOL SERVER SERVER 1. Domain: edu 1. Domain: edu 2. Subdomain: washington HTTP HTTP Read Right to Left http://faculty.washington.edu/daclem/fit100/sp09/index.html http://faculty.washington.edu/daclem/fit100/sp09/index.html PROTOCOL PROTOCOL SERVER SERVER PATHNAME 1. Domain: edu 1. Domain: edu 2. Subdomain: washington 2. Subdomain: washington 3. Server: faculty 3. Server: faculty 4

HTTP HTTP Read Left to Right Read Left to Right http://faculty.washington.edu/daclem/fit100/sp09/index.html http://faculty.washington.edu/daclem/fit100/sp09/index.html PROTOCOL SERVER PROTOCOL SERVER PATHNAME PATHNAME 1. Domain: edu 1. Domain: edu 4. Account: daclem 2. Subdomain: washington 2. Subdomain: washington 3. Server: faculty 3. Server: faculty HTTP HTTP Read Left to Right Read Left to Right http://faculty.washington.edu/daclem/fit100/sp09/index.html http://faculty.washington.edu/daclem/fit100/sp09/index.html PROTOCOL SERVER PROTOCOL SERVER PATHNAME PATHNAME 1. Domain: edu 1. Domain: edu 4. Account: daclem 4. Account: daclem 2. Subdomain: washington 2. Subdomain: washington 5. Folder: fit100/sp09 5. Folder: fit100/sp09 3. Server: faculty 3. Server: faculty 6. File: index.html HTTP Not case sensitive Case Sensitive HTML Read Left to Right • Validating http://faculty.washington.edu/daclem/fit100/sp09/index.html • Paths for images and PROTOCOL SERVER PATHNAME links 1. Domain: edu 4. Account: daclem 2. Subdomain: washington 5. Folder: fit100/sp09 3. Server: faculty 6. File: index.html 30 5

Demonstration Debugging Demo After building a web page, we find it is wrong H o usto n, we have a pro ble m I nte nde d page Paths Paths  Two types of paths  Relative path  Relative  src="huskyTeam.jpg"  To folder where this html page is located  Absolute path  Absolute  Absolute  href="http://courses.washington.edu/fit100/a h f "htt // hi t d /fit100/  Complete URL u09/images/huskyTeam.jpg" 33 34 Paths http  Relative path  http = H yper T ext T ransfer P rotocol  href="huskyPride.html"  https = S ecure http  Absolute path  Starts every link and every Web address  href=" h f "  Sends pages across the Internet to Web S d th I t t t W b http://www.cs.washington.edu/education/co servers urses/cse100/08sp/examples/huskyPride.ht ml " 35 10/9/2009 D.A. Clements, MLIS, UW iSchool 36 6

Hypertext links The Language of Web Pages  A Web page is a collection of hypertext  HTML = H yper T ext M arkup L anguage links, or links  The language that Web browsers understand  Links allow you to jump to another page clear across the Web clear across the Web 10/9/2009 D.A. Clements, MLIS, UW iSchool 37 10/9/2009 D.A. Clements, MLIS, UW iSchool 38 HTML structures the content HTML tags  Tags structure the page The content with HTML tagging <h1>My first Web page!</h1>  Formerly, they also formatted the content; now, that’s done by CSS <p>A new paragraph…</p> The Web page displayed in a Web browser My first Web page! A new paragraph… 10/9/2009 D.A. Clements, MLIS, UW iSchool 10/9/2009 D.A. Clements, MLIS, UW iSchool 39 40 Basic HTML page structure Paired tags All HTML files use the same structure: Tags are paired—opening and closing tags <html> <html> <head> <head> <title>Name of Page Goes Here <title>Name of Page Goes Here <title> <title> </title> </title> </head> </head> <body> <body> </body> </body> </html> </html> 10/9/2009 D.A. Clements, MLIS, UW iSchool 41 10/9/2009 D.A. Clements, MLIS, UW iSchool 42 7