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![Page 1: World Wide Web Aaditya Bhatia CS 147. Agenda History OSI model Hardware IP address DNS Server - Client Peer-to-peer Web-Sites Web programming Search engines.](https://reader036.fdocuments.us/reader036/viewer/2022081603/56649ea05503460f94ba37da/html5/thumbnails/1.jpg)
World Wide Web
Aaditya BhatiaCS 147
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Agenda
• History• OSI model • Hardware • IP address• DNS• Server - Client• Peer-to-peer• Web-Sites • Web programming• Search engines • Questions?
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History
• 1960'so US DoD develops the world's first packet-switched
network, ARPAnet, for resistance against nuclear attack.o First Universities gain access and inter-connections.
• 1970'so NSFNet developedo More Universities added to the network
• 1980'so The first commercial and private ISPs gain access to the
network• 1990's to Present
o Technological advances increase individual access and perpetuates the internet's exponential growth.
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OSI Model
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TCP/IP vs OSI
• Not exactly the same
• Only 4 layers in TCP
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Hardware
• Network Adapter • Hub
• Switch
• Router
• Gateway
• Modem
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Hardware - Network Adapter
• Connects a computer to another device
• Deals with OSI layers 1 and 2 • Ethernet Wired
o 10 Mbpso 100 Mbpso 1 Gbps
• 802.11 Wireless
o ao bo go n
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Hardware - Hub
• Connects multiple devices
• Doesn’t manage packets • Packet Collision
• Relatively slower
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Hardware - Switch
• Layer 2 device
• Routes packets • Packets don't collide
• Much faster
• Telephone exchange
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Hardware - Router
• Creates an internal LAN • Outer network - single IP
• Layer 3 device • NAT - Masks the internal
machines • Routing table
• Wired or wireless
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Hardware - Gateway
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Hardware - Modem
• Modulator – Demodulator
• OSI layer 1
• Relatively Slow • Economical
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IP Address
• Unique identifier
• 4 octets
• Assigned by o ISPo DHCP servero Network admin
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DNS
• Domain Name System • Address resolution
• Analogous to an phone book
• hostname => IP address
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DNS - IP lookup
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DNS - Address resolution
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Server-client mode
• Request • Response
• e.g. a website
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Server
• Dedicated machine • Serves multiple clients
• Handles incoming requests
• Provides services
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Client
• Invokes remote services • Generates request
• A workstation
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Peer-to-peer
• Peers - equal • Act as a server and a client
• Invoke and provide services
• e.g. BitTorrent
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Web-Sites
• Web servero Apache
• Web browser
o Firefox • HTTP Protocol
o Stateless connection o Simulated statefulness
Cookie Server-side session
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HTTP Protocol
• Stateless connection
• Simulated statefulnesso Cookie o Server-side session
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Web Programming
• HTML • CSS
• Server • Client
• AJAX
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Web Programming - HTML
• HyperText Markup Language • Content of websites
• Server response
• Understood by Browser
• Static content
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Web Programming - CSS
Cascading Style Sheet • Defines style of a page
• Easily changeable or replaceable
• "Themes"
• CSS sample:
p{ color: red; font-size: 18px; }
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Web Programming - Server
• Server side scriptingo PHPo Perlo Python
• Programs that execute on server
• Access
o Databaseo Internal systems
• Efficiency
o Servers are faster
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Web Programming - Client
• Client side scriptingo DHTML o JavaScript
• Make changes to page after it has loaded
o periodically o based on user input
• JavaScript sample:
document.write( "<h1>Hello World</h1>" );for( i = 0; i < 10; i++ ) alert( "Hello again " + i );
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Web Programming - AJAX
Asynchronous JavaScript And XML
• Update only a part of page with server's response • Avoid multiple refreshes
• Lesser network traffic
• Example: Yahoo! Mail
• Counter example: SJSU eCampus
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Search Engines
• Help find information• Web pages• Locations• News• Images etc.
• Crawl throughout the Internet
• Gather information continuously
• Key role in advertising market
o Context-based ads
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References
• http://en.wikipedia.org/
• http://www.comptechdoc.org/
• http://www.isoc.org/internet-history/
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for your patience
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Questions?