Transcript Introduction to Internet

Introduction to Internet
Chapter 1 Objectives
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Origins of the Internet
Packets and Routers
TCP/IP
DNS
HTTP
URL
Client-Server
Origins of Internet
• Internet is a network of computer networks
• Hub concept – 1966 ARPANET
• Distributed network – no hub, flow around
disabled units
Routers
• Routers replaces the central hub, the
connectors
• Routers run special-purpose software for
connecting networks
• Routers are the traffic cops of the Internet,
they direct and route the network traffic
Packets
• The network traffic is the packets
• When sending a file, it is broken up into
packets
• Packet size ranges from 100 bytes to 1500
bytes
• Packet has a header (filename, origin &
destination, order number of packet 5 of
22)
Packet-switching
• Packets are sent over the network
• Nearest router receives, checks
destination, sends to another router closer
to destination
• Once all packets arrive, file is
reconstructed by putting the packets back
together again
TCP/IP
• IP Internet Protocal – router software
• TCP Transmission Control Protocol –
software manages creating packets on
both sending and receiving routers
IP address
• Destination addressing scheme
• Four numbers 192.56.215.131
• Each number between 0 to 255
Domain Name System (DNS)
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DNS laid on top of IP addressing system
Created to be more human friendly
192.56.215.131 = www.highpoint.edu
Hostname.organizationname.countryname
/type of organization
• .us United States / .com company
• ICANN manages domain names
Hypertext
• Answer to problem of various file formats
• Imagine newspaper article with a foot note
-> go to library and look up
or-> click to electronically retrieve
HTML
• HTML Hypertext markup language –
document format
• HTTP Hypertext transfer protocal –
transmission protocal
• Browser – software to read the HTML
Internet Applications (i.e., Web Application)
Application
Protocol
Client
Server
Web
Browser
HTTP
(Hypertext Transfer Protocol)
Web Server
URL’s
• Uniform resource locator – used to tell
where to find a document and how to
retrieve it
• The IP/DNS locates the computer
• And specific document on computer to
retrieve
http://universityextension.ucdavis.edu
/distancelearning/index.htm
• http://
- protocal
• universityextension.ucdavis.edu
- combo host/domain name
• distancelearning/index.htm
- the index.htm document
stored in the distancelearning folder
Client-Server Computing
• PC is the client
• Server is the computer that the Web page
document resides
• Server comes from it’s task to serve
documents to other computers on network
• Source document contains HTML
instructions to tell browser how to display
Client/Server Application
Request
Application
Protocol
Client
Server
Response
Client-Server Computing
• Visit to a web page – you don’t actually go
there. The page is sent to your computer.
• After the page arrives the connection is
broken. Unlike the phone network that
keeps the connection until the call is
ended.
Common Internet Application Protocols
Application
Protocol
Client
HTTP – Web
SMTP – E-mail
FTP – File Transfer
IRC – Chat
Companies can, and do,
create their own application protocols.
Server
Web Browsers and Servers
Web
Browsers
Internet Explorer
Netscape
Mozilla
Opera
Web Servers
Apache
Microsoft IIS
Netscape Internet Server
Web Development Options
Web
Browser
Web Server
HTML
Executables
Scripts
Scripts
Executables
SQL
Web Development Options
Web
Browser
Web Server
HTML
Executables
Scripts
Scripts
Executables
SQL
End of Chapter 1
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Origins of the Internet
Packets and Routers
TCP/IP
DNS
HTTP
URL
Client-Server