The Internet CSCI 101

What is the Internet? The largest computer network in the world A giant network of networks. Connecting billions of users.

Internet History Concept of the internet was made in late 1950s During the cold war they had two goals in mind for the internet Secure communication Enable all computers to communicate

ARPANET The original internet was called the Advanced Research Projects Agency Network (ARPANET) Began with university research institution attempting to communicate with each other Vinton Cerf and Robert Kahn are considered the “fathers” of the internet as they developed the first communication protocols. First message was sent from the University of California to the Stanford Research Institute

ARPANET

Web is not the Internet The world wide web is a subset of the internet which is responsible for rendering information via html pages through browsers.

Communication Protocols Computer network protocols are just like conversations, with requests and responses. Hi Network connection req Well Hello there! Network connection response Got the time? It’s 2:00 Get http://www.winthrop.edu time <file>

Internet Protocol (IP) Address When you connect to the internet you are given a unique identification number (IP address) A set of four groups of numbers separated by periods, e.g. 123.45.245.91 Each website has it’s own Unique IP address For example Amazon’s website is 72.21.211.176 we give it the user friendly name www.amazon.com so it’s easier for us to remember.

Sending Data over the internet Data is broken into smaller chunks called packets Packets are sent via various routes when the packets get to their destination to message is reassembled

Why Break into Packets Sending large chunks of data ties up the line and slows communication. It’s easier to recover form error with packets, as you simply resubmit the packet rather than the entire message. The packets can take different routes to balance the load.

What does each Data Packet Contain? Senders IP Address Receivers IP address Reassembly instructions (How many packets are in message, and which packet this is) Data begin sent Max size 64Kb

Sending a Message Cidney is sending a message to her parents back home. Rock Hill Seattle Cidney Mom and Dad I miss you both Breaks up into packets I mis s you both

Sending a Message Cidney is sending a message to her parents back home. Rock Hill Seattle both I mis Cidney s you Mom and Dad I miss you both

Sending a Message Cidney is sending a message to her parents back home. Rock Hill Seattle Cidney Mom and Dad I miss you both Message received and put back together

Firewalls Designed to block unauthorized access into and out of the network. Packet screening: examine incoming data packets to ensure they are properly authorized before letting them through.. Firewall

How it all works http://www.youtube.com/watch?v=PBWhzz_Gn10 This video is a good illustration of how message are sent over the internet http://www.youtube.com/watch?v=PBWhzz_Gn10

World Wide Web Servers scattered all throughout the world, that communicate with each other. Communicate through internet protocols

TCP/IP The main protocols used throughout the internet are TCP/IP Named after Transmission Control Protocol / Internet Protocol TCP prepares the data for transmission, and provides error checking and resending lost data. The IP is the protocol that sends the packets from router to router

Ping A program used to test the reachability of network designations. (CSI). Computers running IP software send out ping requests, which can be sued to test who is on the NTWK. Ping was the name used when submarines send out a sonar pulse and wait for a response. (CSI)

HTTP (Hypertext Transfer Protocol) Transfer html data (web pages) from the server to the client (your computer) http request e.g. Enter www.amazon.com in browser url http response sends Amazon webpage to browser

URL (Uniform Resource Locator) The address of a webpage. Most websites have multiple webpages each with their own unique URL, just like every house on a block has it’s own address http://recipes.com/breads/bananabread.html Protocol domain Path or subdirectory File

DNS (Domain Name System) Phone book for the internet. Just like people can be uniquely identified by their SSNs, computers, and websites can be identified by their IP address, or the user friendly version, domain name)

Domain Names The number of top level domains keeps increasing. ICANN is responsible for organizing the top level domains.

How To Get Your Own Domain Name Buy a server, or server space Buy a domain name that is freely available on ICANN Associate your domain name with your server