The Internet: a world wide combination of WANs and LANs involving millions of machines• U.S. Department of Defense research initiative

– drive was partially military…• secure connections between major military sites (MILNET)

– …partially economic• get most economical use out of scarce computer resources

– December 1969: startup of 4-node ‘ARPANET’– 1980s: evolved into ‘The Internet’

• consisting of thousands of hosts and millions of users– 1990: ARPANET replaced by NSFnet

• NSFnet still major internet backbone in the USA1

2

Connecting to the Internet

• Many home and small business users connect to the Internet via high-speed broadband Internet service

Discovering Computers 2012: Chapter 2Page 76

DSLFiber to the Premises (FTTP)

Fixed wireless

Cellular Radio

Network

Wi-Fi (wireless fidelity)

Satellite Internet Service

Evolution of the Internet

• Each organization is responsible only for maintaining its own network– The World Wide Web Consortium (W3C) oversees

research and sets guidelines and standards• Internet2

– A not-for-profit research– To develop and test advanced network technologies

require that will benefit Internet users in the short-term future

– connect more than 200 universities and 115 companies via a high-speed private network

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Internet Protocol Address (IP Address)

• An IP address is a number that uniquely identifies each computer or device connected to the Internet

• A domain name is the text version of an IP address– Top-level domain (TLD)

• A DNS server translates the domain name into its associated IP address

74.125.230.210

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• http://en.utrace.de/?query=www.psu.ac.th• http://www.whois.net/• http://whatismyipaddress.com/

Internet Architecture

• Domain names must be registered (at ICANN)– so everybody knows where each domain resides

• Hierarchical structure of networks of networks…

• Internet service provider (ISP) provides Internet access for you

Internet Corporation for

Assigned Names and Numbers

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The Internet: Addressing

• Machines in the Internet have unique addresses:– IP-address (32 bits (4 groups)) consisting of two parts

• Domain name: ‘network address’ (given by ICANN)• Machine name: ‘host address’ (given by network operator)

– In dotted decimal form, example: 74.125.95.103– As registered domain name: google.co.th

– Top-Level Domain (TLD): domain’s classification– In each domain list of IP-addresses is maintained

• publicly accessible through name server

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010000011

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• Generic top-level domains• USA top-level domains• Country code top-level domains• Internationalized country • code top-level domains

List of Internet top-level domains

The Internet: Killer Applications

• The internet originally intended for:– remote login & file transfer (does work)– distributed computing (still a promise only)

• However:– 1980s: e-mail– 1990s: web-browsing– 2000s: search engines– 2010s: Grid computing?

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The World Wide Web

• Software infrastructure on top of the Internet• Developed at CERN High-Energy Physics

laboratories in Geneva, Switzerland (1991)• Hypertext (HTML):

– ‘mouse-clickable’ access to files on other computers

• Requires special software:– web browser (client)– web server

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The World Wide Web

• The World Wide Web, or Web, consists of a worldwide collection of electronic documents (Web pages)

• A Web site is a collection of related Web pages and associated items

• A Web server is a computer that delivers requested Web pages to your computer

• Web 2.0 refers to Web sites that provide a means for users to interact

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The World Wide Web

• A Web browser, or browser, allows users to access Web pages and Web 2.0 programs

Internet Explorer Firefox Opera

Safari Google Chrome

To find documents on the World Wide Web

• Each document has unique address:– URL (uniform resource locator)

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protocol

domain name

path

Web page name

HyperText Transfer Protocol: HTTP) คือโพรโทคอลในระดับชัน้โปรแกรมประยุกต์เพื่อการแจกจา่ยและการทำางานรว่มกันกับสารสนเทศ

ของสื่อผสม ใชส้ำาหรบัการรบัทรพัยากรท่ี เชื่อมโยงกับภายนอก ซึ่งนำาไปสูก่ารจดัตัง้

 เวลิด์ไวด์เวบ็

Homework (What is it?)FTP (File Transfer Protocol) เป็นโปรโตคอล

มาตรฐานในอินเตอรเ์น็ต ซึ่งเป็นวธิทีี่ง่ายที่สดุใน การแลกเปล่ียนไฟล์ ระหวา่งคอมพวิเตอรบ์น

อินเตอรเ์น็ตHypertext Transfer Protocol (HTTP) ท่ีใชใ้นการสง่

เวบ็เพจ็และไฟล์ที่เก่ียวขอ้งSimple Mail Transfer Protocol (SMPT) ท่ีใชส้ง่

ผ่าน e-mailPOP3 (Post Office Protocol version 3) IMAP (Internet Mail Access Protocol)MIME (Multipurpose Internet Mail Extensions)• VoIP (Voice over Internet Protocol)

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HTML – HyperText Markup Language

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HTML is the main markup language for web pages. HTML elements are the basic building-blocks of webpages.

• XML is a markup language that defines a set of rules for encoding documents in a format that is both human-readable and machine-readable. 

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XML – Extensible Markup Language

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jass.xml

jw.css

Linking to jw.css style sheet

jass.xml document formatted with jw.css style sheet

the cascading style sheet stored in the jw.css file

How messages are transferred over the Internet.

• This transfer process requires – the cooperation of all the computers in the system,

and – software for controlling this process (resides on

every computer in the Internet).

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Networking Software

• Provide the infrastructure required for transferring messages from one machine to another.

• In the Internet, this message-passing activity is accomplished by means of a hierarchy of software units, which perform tasks analogous to those that would be performed if you were to send a gift in a package from the South to a friend on the North.

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Gift Package-Shipping Example

• You are not concerned with the details of the shipping company, and the

• shipping company is not concerned with the internal operations of the airline.)

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You are not concerned with the details of the shipping company, and the shipping company is not concerned with the internal operations of the airline.

The Internet Software Layers

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Network Protocols

• Define details of all network activities, a.o.:– encoding of messages– addressing of messages– splitting and merging of (large) messages– deciding who has the right to send messages, etc…

• In other words, protocols ensure that messages:– arrive at the right place– in the right order– without errors– and are understood by the receiver as well

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Following a Message Through the Internet

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Network Protocol Summary

• Interaction between four software layers– Application:

• deals with messages and addressing– Transport:

• deals with message ↔ packets conversion– Network:

• deals with ‘hopping’ packets through the internet– Link:

• deals with the transmission of packets as bit streams

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Multiple Implementations: TCP versus UDP

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Towards ‘The Grid’

• The Internet:– a network with static compute and data resources in which

information flows from the producer to the consumer (and sometimes back).

– user personally decides what data to access and what servers to use

• The Grid:– dynamic computing utility over a distributed set of compute

and data resources– automatic resource detection, automatic error recovery,

automatic performance optimization, etc…27

The Grid: Large Scale Problem Solving

• Utilize (a) large number or (b) very high-end, specialized resources over large distances

Identifying brain disorders

California: earthquake simulations

Telescope data analysis

Finding E.T.???28

Cloud Computing

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Cloud computing is Internet- ("cloud-") based development and use of computer technology ("computing").

Cloud computing is about hardware-based services (involving computing, network and storage capacities), where:• Services are provided on-demand; customers can pay for them as

they go, without the need to invest into a datacenter.• Hardware management is abstracted from the customers.• Infrastructure capacities are elastic and can easily scale up and

down.

Web 2.0

• The term "Web 2.0" is commonly associated with web applications that facilitate interactive information sharing, interoperability, user-centered design and collaboration on the World Wide Web.

• Examples of Web 2.0 include – web-based communities - hosted services– web applications - social-networking sites– video-sharing sites - wikis – blogs - mashups – folksonomies 30

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