The Internet

CHAPTER 9

TH

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RECAP: COMPUTER NETWORKS

LAN

WAN

HARDWARE

Hub: LAN hardware that transmits data to the

nodes on the LAN “rude”.

Switch: Hardware connectivity through which data

travels. More efficient. keeps a record of the MAC addresses of all the devices connected to it.

TRANSMISSION LINE TYPES, USES, AND SPEED

WHAT IS INTERNET?

A network of networks, joining many government, university and private computers together and providing an infrastructure for the use of E-mail, bulletin boards, file archives, hypertext documents, databases and other computational resources

The vast collection of computer networks which form and act as a single huge network for transport of data and messages across distances which can be anywhere from the same office to anywhere in the world.

Written by William F. Slater, III1996President of the Chicago Chapter of the Internet Society

HISTORY OF THE INTERNET1969 : ARPANET was born. 4 nodes were inter-connected: UCLA,SRI,UCSB, U. of Utah

Charley Kline from UCLA sent 1st packet.

1972 : First computer-to-computer chat program at UCLA.

1975 : First mailing list was created by Steve Walker.

1984 : DNS (Domain Name System) was introduced.

1988 : First Internet Worm.

1990 : AOL, CompuServe provided dial-up service.

1991 : WWW was created by Tim Berners-Lee from CERN

1994 : Commercial network. Shopping mall. Can order pizza online.

1998 : 2M domain names registered. Compaq bought altavista.com for $3.3M. Google founded

2003 : Facebook launched

A global network of computers that communicate using a common language (network of networks)

Internet is composed of two parts: the infrastructure (hardware), and the software (applications and protocols)

Hardware: cables, routers, computers, and servers.

Software: applications, programming languages, databases, and protocols

that make communication

THE INTERNET

INTERNET CHARACTERISTICS

The power of the Internet:

1. Ubiquity2. Low cost3. Global Reach4. Open and Shared ownership5. Richness – complexity and content of the

message 6. Interactivity

WWW The world wide web is a sophisticated system for universal information

capture and delivery The world wide web consortium (W3C) definition of the web: "The

World Wide Web is the universe of network-accessible information, an embodiment of human knowledge"

Provides information access in ways not previously possible– Hyperlinked (Hypertext)– Graphical user interface– Pictorial and non-text information– Information that changes rapidly– Immediate access– Anyone can author a web site– Multi-user access to the same information (try that with a book)– Easily searchable information

The functionality of the WWW is based on 3 main standards:

URL (Universal Resource Locator) HTML (Hypertext Markup Language) HTTP (Hypertext transfer Protocol)

THE UNIVERSAL RESOURCE LOCATOR (URL)

Each page of information on the web has a unique address called the URL at which it can be found

http://faculty.uscupstate.edu/atzacheva/lecture1.html

The document can be obtained

using the Hypertext

Transfer Protocol (HTTP)

Host Name - The Name of Web Server

Path to the Web Page

Denotes that the File is Written in HTMLHyperText Markup

Language

File Name

1 2 3

Protocol Host Name File Name

HTML

HTML is a universal, simple language for formatting text. It also allows embedding of graphics, and linking of documents via ‘hyperlinks’.

‘Hypertext’ documents allow readers to freely move around the document, following links to subjects of interest.

HTML is a language that is used to specify the structure of documents for retrieval across the Internet using browsers.

HTTP

The standard Web transfer protocol is HTTP (HyperText Transfer Protocols). It is used for document exchange between servers and clients (typically browsers) in the WWW.

To retrieve a document, the client first sends a request to the web server and waits for a reply

An HTTP daemon/service (a program that waits for http requests) on the server then handles the request and the document is sent to the client (over a connection established using TCP/IP – Transmission Control Protocol / Internet Protocol)

We recall from previous lectures, that a Protocol is “Agreed upon sets of rules that provide order to a system or situation.” In this case, a set of rules/standards for communicating on the Internet.

Key Digital Networking Technologies

• Packet switching Method of slicing digital messages into parcels (packets),

sending packets along different communication paths as they become available, and then reassembling packets at destination

Packet-Switched Networks and Packet Communications

TCP/IP

TCP = TRANSMISSION CONTROL PROTOCOL(Breaks messages into packets,Checks the integrity of incoming Packets and reassembles them)

IP = INTERNET PROTOCOL(routes packets aroundthe Internet)

WWW: WHAT IS IT?

Is a distributed collection of hypermedia documents that are inter-linked together. Web servers store the information (text, images, sound clips, video clips), and Web clients or browsers access this information.

Domain addresses are governed by the standard Universal Resource Locator (URL) and end in suffixes that indicate the type of domain ownership.

i.e commercial sites end in .com, not-for profit entities use the .org suffix, government (.gov)

• The Domain Name System: Converts IP address to

domain names

Hierarchical structure top is root domain, followed by top-level domains, second-level domains, and third-level domains

Example: Domain name: www.orbitz.com IP: 198.151.61.100 Convert Domain Name to IP ad

dress

INTERNET ADDRESSING AND ARCHITECTURE

The Domain Name System is a hierarchical system with a root domain, top-level domains, second-level domains, and host computers at the third level.

INTERNET ADDRESSING AND ARCHITECTURE

• Internet Architecture and GovernanceThe Internet Corporation for Assigned Names and Numbers (ICANN),

assigns IP addresses

The World Wide Web Consortium (W3C), sets hypertext markup language and other programming standards for the web

CLIENT-SERVER RELATIONSHIP

Client issues HTTP requestsprocess documents

displays documents

Serverresponds to HTTP requests

CLIENT-SERVER ARCHITECTURE

INTERNET

SERVER

Client makes requestsServer responds

Client computers running Web browser and other software can access an array of services on servers over the Internet. These services may all run on a single server or on multiple specialized servers.

Client/Server Computing on the Internet