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The Internet: How it Works

Management of the Internet

Who owns the internet?o Individualso Universitieso Government agencieso Private companieso Nonprofit organizationso User groups

Who pays for the internet?o U.S. taxpayerso Businesseso Universitieso Other countries

Connecting to the Internet

Internet backboneo Collection of large national and international networkso

T lines initially used for backbone ISP connections Carried digital data over twisted pair wires

o Optical carrier line (OC) todays most common backboneISP connection

High-speed, fiber-optic lines designed to provide highthroughput

OC Line Speeds

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In the pasto Points of connection between ISPs

Once known as network access points (NAPs) Designed to move large amounts of data among

networks

Nowo Private sector companies make up the internet system

Exchange data via internet exchange points (IXPs) Typical IXP is made up of one or more network switches

Points of Presence (POPs)

Banks of modems where individual users connect to an ISP

The Network Model of the Internet

Internet communications follow the client/server network model

Clients request services Servers respond to client requests Types of servers

o Web servers Host web pages

o Commerce servers Enable the purchase of goods and services over the web

o File servers

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Provide remote storage space for files that users candownload

uTorrent

Data Transmission and Protocols

Computer protocols are rules for electronic information exchange Open system protocols

o Any computer can communicate with other computers usingthe same protocols

Circuit Switching

Dedicated connection between two points Remains active until the transmission is terminated Used in telephone communications Inefficient for computers

Packet Switching

Data is broken into small units (packets) Packets are sent over various routes to their destination Packets are reassembled by the receiving computer Packets contain:

o Destination/source addresseso Reassembling instructionso Data

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TCIP/IP Transmission Control Protocol (TCP)

o Prepares data for transmissiono Provides error checkingo Enables resending lost data

Internet Protocol (IP)o Responsible for sending data from one computer to another

Suite of interrelated protocols

Protocols

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IP Address Unique number that identifies each device connected to the internet Typical IP address

o 197.24.72.157 Static address

o address never changes Dynamic address

o Temporary addressHaving Enough IP Addresses

IPv4 addressing scheme didnt foresee explosive growth Classless Interdomain Routing (CIDR)

o Allows a single IP address to represent several uniqueaddresses

o Uses a network prefix (slash and number)

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o Identifies how many bits in the IP address are uniqueidentifiers

Internet Protocol version 6 (IPv6)o Longer IP addresseso Many companies and government agencies are starting to

switch to IPv6

Domain Names

Names that take the place of an IP addresso Sample domain name:www.mydomain.com

Top-level domain (TLD)o Portion of the domain name that follows the doto Includes .com, .org, .gov, .edu, and .net

Second-level domaino Unique name within a top-level domaino Yahoo.com, whitehouse.gov, unesco.org

Domain Name System Servers Internet servers that translate domain names into IP addresses ISPs go first to a default DNS to resolve a name Name queries work up the hierarchy to the root DNS servers if

required

http://www.mydomain.com/http://www.mydomain.com/http://www.mydomain.com/http://www.mydomain.com/

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Other Protocols

File Transfer Protocol (FTP)o File-sharing protocolo Files are downloaded and uploaded using the internet

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HTTP and SSL

HyperText Transfer Protocol (HTTP)o Protocol for transferring hypertext documentso Hypertext documents are linked to other documents through

hyperlinks

HyperText Transfer Prtocotol Secure (HTTPS) Transport Layer Security (TLS) and Secure Sockets Layer (SSL)

o Protect the integrity of data and security of transmissionsover the internet

HTML/XHTML

HyperText Markup Language (HTML)o Tags that describe the formatting and layout of a web page

Xtensible HyperText Markup Language (XHTML)o Successor to HTMLo Much more stringent rules regarding tagging

Not programming languages, but sets of rules for specifying how abrowser should display text

Extensible Markup Language (XML)

Designed for information exchange Can be used to create your own markup language Used in e-commerce transactions Custom packages for specific communities

o MathML, Wireless Markup Language (WML)

Common Gateway Interface (CGI)

Browsers request that a program file executes (runs) CGI files are often called CGI scripts Adds Web page interaction

o Adding names to guest books/mailing lists

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o Completing forms

Dynamic HTML

A combination of technologieso HTML/XHTMLo Cascading style sheetso JavaScript

Allows a web page to change in response to user action Brings special effects to otherwise static web pages

AJAX and JavaScript AJAX (Asynchronous JavaScript and XML)

o Newer technologyo Facilitates creation of web applications that update a page

without requiring a page refresh or leaving the page

o Does not require JavaScript or XML JavaScript

o Most commonly used scripting language for creating DHTMLeffects

Cascading Style Sheets

Statements that define in a single location how to displayHTML/XHTML elements

Enable a web developer to define a style for each HTML/XHTMLelement

o The rule may be applied to as many elements on as manyweb pages as needed

o Speeds up global changes

Document Object Model

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Organizes the objects and elements of a web page Defines every item on a web page as an object Developers can easily change the properties of these objects

Client-Side Applications

Programs that run on a client computer with no interaction with theserver

Types includeo HTML/XHTML document embedded with JavaScript codeo Applet: small program that resides on the server

Communications Over the Internet

Email

Simple Mail Transfer Protocol (SMTP) Multipurpose Internet Mail Extensions (MIME) Email Security

o Encryption Private-key encryption Public-key encryption

o Secure data transmission software SafeMessage

Instant Messaging (IM)

Client/server program for real-time, text-based conversations Popular IM programs

o AOL Instant Messengero ICQo Yahoo! Messengero Windows Live Messenger

Increasing security threatso Should not be used for sensitive data

Voice over Internet Protocol (VoIP)

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Allows inexpensive or free long-distance phone calls over theinternet

Some cell phones are VoIP enabledo Customers must be able to connect to a Wi-Fi signal

uses packet switching

Looking Ahead (a bit)

Broadband over power lines (BPL)

Already deployed in Australia and Europe Not as fast as cable or DSL Prospect of sending exobits per second (1017)

WiMax the next generation of Wi-Fi

Wi-Fi has approximately 300 feet of connectivity WiMax would offer up to 31 miles at 72 Mbps (faster than current

cable or DSL connections)

Currently 400 WiMax networks deployed in 130 countries Bell and Rogers offering a limited service now and other companies

are beginning to offer it

Looking Ahead (not too far)

As HTML5 is being developed, developers are looking again atpackets and circuits switching

o Faster processing might mean a return to circuit switching Websockets provide a continuous connection so requiring less data

to be transferred with each transaction (bits vs. Kbits)

o Send and receive data at the same time

Do you believe what you read?

Man in the Middle proxy servers

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o Intercept traffic going to and from particular sites likeFacebook and Google

o Change the text to make the message m ore governmentfriendly or to disrupt the site to make it look like a site

problemo China is accused of using them as well as Tunisiao Fake security certificates encountered

Your Personal Cloud

Google Chrome OS and HPs WebOS are positioning for the personalcloud revolution

o Your device need to have no apps installedo Access apps, data, and devices anywhere