CS301 Page 1

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Basic WWW Systems
Web Server Hosting web pages
Retrieving web pages using HTTP protocol
Web Authoring System create web pages
Internet
Publish web pages
Scanner
Video capture
Sound card
Web page document written in HTML,JSP,ASP,PHP
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What is Unique in WWW?

• Hyperlink Use Hypertext Markup Language HTML to
  describe the document in ASCII text (extended to
  iso-8859-1)
• Naming scheme Name object in the web with
  Universal Resource Locator (URL) with
  syntaxprotocol//domain_nameportno/lturi or
  path namegt
• HTTP HyperText Transfer Protocola simple
  request-response protocol for transferring HTML
  documents
• ASCII text based (not binary, therefore easy to
  debug)
• With tags describing the formatting of content.

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Web Page Authoring System

• Text Editor type in HTML lttaggt and content
• HTML Editor like normal word processor, user did
  not have know a lot about HTML syntax, e.g.,
• Dreamweaver, Homesite, Netscape Page Composer, MS
  Front Page
• Dreamweaver, Homesite, and Front Page take
  further step by providing templates and web site
  management functions (upload to multiple servers,
  check/verify links)
• Most desktop publishing software and word
  processor have built-in converters to convert
  from their internal format to HTML format. For
  example
• OfficeXP, FrameMaker,

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3-tier Enterprise Web Systems

• Web Server
• Hosting web pages
• Run Server Side Script
• Access Database/Enterprise Application Server

Database Server
SQL/TCP
Application Server
HTTP protocol
HTTP SOAPWeb Service
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Web Programming

• Basic Web Application Development
• Develop Client Side Javascript/VB Script
• Develop Server Side CGI Script (Perl/PHP/DBI)
• Advanced Web Application Development
• Develop Web Service (J2EE/.NET), document them
  using WSDL, publish them to UDDI portal
• Develop web portal (J2EE uPortal PHP based
  portal)Customized user access with XML/XSL/DB
  profile
• Advanced IDE such IBM Rational Software
  Architecture help develop enterprise advanced web
  application.

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Simple Web Access Example Step1

• Someone requests a document using a browser (Web
  Client) on a computer connected to Internet
• Type in a URL, http//www.netcraft.co.uk/Survey/
• The browser parses the URL,
• obtains domain name of url, www.netcraft.co.uk
• asks Domain Name Server (DNS) for translating the
  domain name to the IP adddress
• with IP address the client computer set up a HTTP
  connection to the server

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Computer Network

• Local Area Network (LAN) a private-owned network
  within a single building or campus of up to a few
  kilometer in size.
• Wide Area Network (WAN) a network that spans a
  large geographical area, often a country or
  continent, and connects LANs or MANs. It consists
  of transmission line (called circuits, channels,
  or trunks) and switching elements (called
  switching nodes, data switching exchanges or
  router).

DNS server
web client
DNS server
web server
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Protocol and Protocol Layer

• A set of rules for achieving a global objective
  exercised by geographically distributed nodes.
  (Robert Gallager, Prof. EE MIT)

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Protocol Data Encapsulation
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Internet Protocol Layer Interface
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Simple Web Access Example Step2

• Browser sends ASCII characters string to
  serverGET /survey/ HTTP/1.0User-agent Mosaic
  for X windows/2.4Accept text/plainAccept
  text/htmlAccept image/
• httpd server parses the request according to
  HTTPinterpret rest of the metainfo for browser
  capabilitiesretrieve c/InetPub/wwwroot/survey/de
  fault.htm send information back using HTTP/1.0
  format

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Simple Web Access Example Step3

• Server replies information using HTTP/1.0 format
• HTTP/1.0 200 OK
• Server Microsoft-IIS/2.0
• Date Thu, 22 Jan 1998 175415 GMT
• Content-Type text/html
• Accept-Ranges bytes
• Last-Modified Mon, 18 Nov 1996 083810 GMT
• Content-Length 4051
• lt!doctype html public "-//IETF//DTD HTML//EN"gt
• ltHTMLgt
• Server close file, network connection, wait for
  next request

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Homework 1 Exercise2

• Go to any CS Unix machine with telnet software
• Execute telnet blanca.uccs.edu 80
• Type GET /chow/index.html HTTP/1.0ltCRgtltCRgt
• You can try telnet viva.uccs.edu 80 gt outType
  the above 3 lines of HTTP request
• See the return web page saved in the file named
  out
• Try GET /chow/ HTTP/1.0 and see what happens

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Simple Web Access Example Step3a

• Browser send GET /sample.htm HTTP/1.0
• Server replies
• HTTP/1.0 404 Object Not Found
• Content-Type text/html
• ltbodygtlth1gtHTTP/1.0 404 Object Not Found
• lt/h1gtlt/bodygt
• Server close file, network connection, wait for
  next request

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HTTP

• HTTP1.1 http//www.w3.org/Protocols/rfc2068/rfc206
  8
• A HTTP request consists of
• method GET, HEAD, POST, PUT, DELETE,
• Universal Resource Identifier (URI)
• Protocol version
• other info to modify or supplement the request
• If-Modified-Since (only return object if it is
  newer the date
• authorization (user password or other
  authenticaiton as required)
• accept application/postscript

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HTTP Response

• consists of
• status line (success or failure)
• HTTP/1.1 400 Bad Request200 (Document Follow),
  301 (Move Permanently), 302 (Move Temporarily),
  304 (Not Modified), 401 (Unauthorized), 402
  (payment required), 403 (Forbidden), 404 (Not
  Found), 500 (server error)
• description of the infnormation (metainfo)
• Server, Date, Content-Length, Content-Type,
  Content-Encoded, Last Modified
• actual info requested

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Content-Type MIME Type

• text/plain
• text/html
• application/postscript
• image/gif
• image/jpeg
• audio/basic
• audio/midi
• video/mpeg
• x-world/x-vrml

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Improving WWW Delivery Systems

• Currently network is bottleneck.
• The retrieval of web pages can be improved by
• increasing network bandwidth, e.g., ADSL link
• reducing round trip, e.g., use client side
  programming to check data with Java/Javascript
• caching (both at client and proxy cache server)
• increase and processing power of web servers
• load balancing by partitioning client-server
  requests

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Content Delivery Networks
Fast Response
Clients
_at_Home
PSINet
Client Cache
MindSpring
Edge Network Cache Server
Client Side Cache Server
Clients
Clients
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Large Web Sites

• Mapping the request, e.g., ftp.netscape.com,
  evenly across a set of server, e.g.,
  ftp1-28.netscape.com

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CISCO Distributed Director

• Distributed Director uses, the Director Response
  Protocol (DRP), a UDP-based application for
  querying DRP server agent for BGP and IGP routing
  table metrics between distributed servers and
  clients, and perform load distribution.

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Internet Caching

• Harvest/SQUID Cache hierarchical, 42 ftp bw
  reduction
• Client/Proxy Cache. Local Small, 65 bw reduction
• Server Push Cache Gwertzman and Seltzer
  (cornell)
• Distributed Internet Cache Povey and Harrison
  (uq) hierarchical index on tree top, content on
  the leave
• Cachemesh Wong and Crowcroft (ucl)cache routing
  table for reducing search overhead
• WebWave Heddaya and Mirdad (bu)Cache on Route,
  Tree Load Balancing Load Diffusion
• Adaptive Web Caching Zhang, Floyd,
  JacobsonSelf-configuration Cache Group,
  Multicast.

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Dynamic Server Selection One candidate
architecture
Server push load status
Client probe response time
client
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WAN Load Balancing Architecture-3
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Important Web Sites

• http//www.w3c.org/
• http//developer.netscape.com/
• http//java.sun.com/
• http//www.microsoft.com/workshop/default.asp
• http//www.apache.org/
• http//www.netcraft.co.uk/Survey/
• http//web.mit.edu/afs/athena/user/w/s/wsmart/WEB/
  HTMLtutor.html
• ...

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Useful References

• Links will be added in our class web page
• Internet World Wide Web How to Program 2nd
  Edition, by Deitel, Deitel, Nieto, Prentice Hall,
  2002. Generic, Coverage very broad.
• Core Web Programming, 2nd Edition, by Marty Hall
  and Larry Brown, PH/PTR, 2001. focus on
  Java/Servlet/JSP.
• Programming the World Wide Web, by Sebesta,
  Adddison Wesley, 2002. Concise.
• Oreilys Web series
• HTML, CGI, Dynamic HTML, Programming Perl
• Web Server Technologies by Nancy J. Yeager and
  Robert E. McGrath, Morgan Kaufmann 1996.
• HTMLCGI
• World Wide Web Beyond the Basics, edit by Marc
  Abrams, Prentice Hall, 1998
• ...

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Homework1

• Part 1
• Read Wade Martinson's HTML tutorials
• Create a web page ltyour logingt.html with
• your recent photo with face big enough (scan it
  and save in JPEG as ltyour logingt.jpg put it in
  ltlogingt/public_html/cs301/image directory on CS
  Unix machine.
• short vita with at least email address
• your interests in CS301
• See examples in http//cs.uccs.edu/cs522/CS522F20
  01Photo.html
• Put this web page in ltyour logingt/public_html/cs3
  01 directory on CS Unix machine.
• Part 2
• Exercise 1 as discussed in Page 11.
• Part 3
• Discuss how to improve web system performance.