Copyright © Curt Hill The Internet An Introduction

What is it? A series of interconnected computers Outgrowth of Defense Advanced Research Projects Agency (DARPA) in the 60s –Original was called ARPANet –Other large networks included BITNET and CSNET National Science Foundation started NSFnet in 1986 –This took over the non-military functions of DARPANet and became the internet Copyright © Curt Hill

Connections A computer is not directly connected to all the others Instead a computer is in a local area network This local area network then connects to one or more other local area networks The Internet is a network of networks Copyright © Curt Hill

How do they communicate? TCP/IP –Transmission Control Protocol –Internet Protocol This is the low level protocol that allows any communication Standardized in 1982 Any computer, printer, cell phone or PDA that can handle TCP/IP can be on the Internet Copyright © Curt Hill

IP Addresses In order to be a node that uses TCP/IP the device must have an IP address The current standard is for this address to be four integers separated by dots –Each number is in the range is for exampleWWW.vcsu.edu IPV6 is partially adopted and coming Copyright © Curt Hill

Domain Names Numbers like IP addresses are very computer friendly but not very people friendly Domain names are names equivalent to an IP number A domain name is two or more words separated by dots For example: –edu is the domain for education –vcsu is unique to Valley City State University –www identifies a single computer in the VCSU domain Copyright © Curt Hill

Specialized nodes A Domain Name Server –Takes a request to convert a domain name into an IP number Router –The gate between two subnets – it broadcasts messages within its network Switch –A better gate between two subnets –Enables better security Copyright © Curt Hill

Internet Again Supports many formats of communication File transfers World Wide Web –Just a part of the Internet –The most common –Based on HTML, web servers and web browsers Copyright © Curt Hill

HTML Hyper Text Markup Language (HTML) was originally designed to display technical papers –Usual formatting –Graphics –Hyperlinks were intended for references Eventually used to display anything Copyright © Curt Hill

URL Universal Resource Locator Has the following format: Protocol :// Machine The protocol is one of several: –http – hyper text transfer protocol –https – http secure –ftp – file transfer protocol The machine is a computer with possibly other stuff Copyright © Curt Hill

URL again The protocol we are most interested in is http –https as well This is the way web pages are communicated The machine may be referenced by a: –Domain name –IP number It may also be followed by a disk path and file name Copyright © Curt Hill

Example URLs ftp://sourceforge.org file://temp.htm Copyright © Curt Hill

Ports Each TCP/IP connection attaches to a port number By default HTTP uses port 80 If the default is not used then it is specified by a port number followed by a colon: Copyright © Curt Hill

HTTP There are two pieces to the communication A server and a client One server will be connected to many clients The connection between the two is very short lived The web is typically anonymous Copyright © Curt Hill

Communication Language HTTP passes requests to the server –This is usually an URL It returns the requested data –Usually a file of HTML The returned data may be anything but a web page is most common This web page is usually in HTML or XHTML Consider HTML next Copyright © Curt Hill

Purpose HTML is designed to display material It has no control over margins –This is a function of browser Other than that it has many of the same functions as a word processor or text processor A word processor may store its documents in a file using any characters The markup of HTML must be plain text Copyright © Curt Hill