Introduction to Internet

Chapter 1 Objectives 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 Each number between 0 to 255

Domain Name System (DNS) DNS laid on top of IP addressing system Created to be more human friendly = 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) Server Client Application Protocol Web Server Web Browser HTTP (Hypertext Transfer Protocol)

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

/distancelearning/index.htm - 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 Server Client Application Protocol Request 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 Server Client Application Protocol HTTP – Web SMTP – FTP – File Transfer IRC – Chat Companies can, and do, create their own application protocols.

Web Browsers and Servers Web Servers Web Browsers Internet Explorer Netscape Mozilla Opera Microsoft IIS Netscape Internet Server Apache

Web Development Options Web Server Web Browser HTML Scripts Executables Scripts SQL

Web Development Options Web Server Web Browser HTML Scripts Executables Scripts SQL

End of Chapter 1 Origins of the Internet Packets and Routers TCP/IP DNS HTTP URL Client-Server