A.S. 1/4/2014

The Internet

Prof. Dr. M. H. Assal

Introduction to Computer

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What is Network? A network is a collection of computers or other

hardware devices that are connected together, using special hardware and software, to allow them to exchange information and cooperate.

Switch

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Uses for Computer Networks

Sharing an Internet connection among several users. Sharing application software, printers, and other

resources. Facilitating Voice over IP (VoIP), e-mail, video

conferencing, messaging, and other communications applications.

Working collaboratively, such as sharing a company database.

Exchanging files among network users and over the Internet.

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Network Characteristics

Networks can be identified by a variety of characteristics: Wired or Wireless access Topology Architecture Size or Coverage area

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Wired vs. Wireless Networks

Wired network: A network in which computers and other devices are connected to the network via physical cables.

Wired networks include:o Conventional Telephone Networkso Cable TV Networks

The wired networks commonly found in:o Schoolso Businesseso Government Facilities

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Wired vs. Wireless Networks

Wireless network: A network in which computers and other devices are connected to the network without physical cables; data is typically sent via radio waves.

Wireless networks include:o Conventional television and radio networkso Cellular telephone networks, o Satellite TV networks

The wireless networks commonly found in:o Homeso Schoolso Businesses

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Wired vs. Wireless Networks

Wired Wireless

Advantages

• Inexpensive Equipment

• Extremely Reliable

• Superior Performance

• Greater Mobility

• Relatively Easy to Setup

• Much less cabling

Disadvantages

• Need to run cables n difficult environments (walls, floors & ceilings)

• Cables needed for device to device communication

• Not very much Reliable

• Suitable for mobile devices only

• Slower than Wired

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Network Topologies Topology is how the devices in the network (called

nodes) are arranged. Bus networks: A network consisting of a central

cable to which all network devices are attached

Bus

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Network Topologies Ring networks: Network devices are connected in a

circular chain, with the channel beginning and ending at the same computer.

Flow of message

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Network Topologies Star networks: A network in which any device is

connected directly to several other devices

Switch

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Network Topologies Mesh networks: A network in which there are

multiple connections between the devices on the network so that messages can take any one of several paths.

Some networks use a combination of topologies

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Network Architectures Architecture is the way Networks are designed

to communicate. The two most common network architectures are:

o Client-servero Peer-to-Peer (P2P).

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Network Architectures Client-Server Networks include both clients (computers

and other devices on the network that request and utilize network resources) and servers (computers that are dedicated to processing client requests).

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Network Architectures With a peer-to-peer (P2P) network, a central server is

not used. Instead, all the computers on the network work at the same functional level, and users have direct access to the computers and other devices attached to the network.

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Network Size and Coverage Area

Networks are classified is by the size of their coverage area. This also impacts the types of users the network is designed to service.

The most common categories of networks:o Personal Area Networks (PANs): A network that connects an

individual’s personal devices that are located close together.o Local Area Networks (LANs): A network that connects

devices located in a small geographical area, such as within a building.

o Wide Area Networks (WANs): A network that connects devices located in a large geographical area.

o Intranets: is a private network (such as a company LAN) that is designed to be used by employees and is set up similar to the Internet and is accessed via a Web browser.

o A company network that is accessible to authorized outsiders is called an extranet.

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Networking devices

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Network Applications Telephone Service Global Positioning System (GPS) Applications The Internet Television and Radio Broadcasting Monitoring Systems Videoconferencing, Collaborative Computing Telemedicine

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Network Applications The Internet

o The Internet is the largest and most well-known computer network in the world.

o It is technically a network of networks, since it consists of thousands of networks that can access each other via the internet backbone.

o Many networking applications today (such as information retrieval, shopping, entertainment, and e-mail) take place via the Internet.

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What is the Internet? The Internet is a worldwide collection of separate,

but interconnected, networks accessed daily by millions of people using a variety of devices to obtain information, access entertainment, or communicate with others.

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What is the Internet? The Internet we know today is the result of the

evolution of ARPANET and the creation of the World Wide Web (WWW).

ARPANET Project:o created by The U.S. Department of Defense

Advanced Research Projects Agency (ARPA) in 1969o small network of supercomputero allow researchers located in different places to

communicate with each other

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What is the Internet? The World Wide Web: The collection of Web

pages available through the Interneto Proposed by Tim Berners-Lee in 1989o Originally only text-based Pages linked together through

text or images (today’s hyperlinks)o Wide variety of content available via Web pages today

(social networking, podcasts, blogs and wikis)

Internet2: Researches advanced Internet applications and technologies

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The Internet Community Today

Most members of the Internet community fall into one or more of the following groups:o Users: People who use the Interneto Internet service providers (ISPs): Provide access to the

Internet, typically for a feeo Internet content providers: Provide Internet content

(Businesses, organizations, educational institutions, Individuals)o Application service providers (ASPs): Companies that

manage and distribute software-based services over the Internet• Web service: Added to a Web page to provide specific services for

end userso Infrastructure companies: Own or operating the physical

structure of the Internet (Conventional/Mobile phone companies, & satellite Internet providers)

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Possible devices include:o Personal Computerso Mobile Phoneso Gaming devices

Connections can be:o Dial-up

• Uses standard phone lines & modem to dial-up ISP• Inconvenient• Slower, but cheaper• Ties up telephone lines

Connecting to the Internet

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Connecting to the Internet

o Direct (always on)• Device is continually connected to the Internet• typically broadband; fast speeds needed for many Web

activities today• Because you are always connected, it is important to protect

your computer from hackers

• DSL: Broadband delivered over telephone lines• Transmits over telephone lines but does not tie up the

line• Satellite: Broadband option for rural areas

• Requires satellite modem, and transceiver dish• Fixed wireless: Uses radio transmission towers rather than

satellites• Mobile wireless: Access via mobile phone or device• Hotspot: Public wireless networks (Wi-Fi)

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TCP/IP TCP/IP is a set of protocols developed to allow

cooperating computers to share resources across a network

TCP stands for “Transmission Control Protocol” IP stands for “Internet Protocol” Every host on the Internet must have a unique IP

address The IP (version 4) or IPv4 address is a 32-bit number

written in dotted 4 decimal parts. Each part range from 0 to 255 (Single Byte). A maximum of 4.3 billion possible addresses

Ex: 192.252.12.1410.1.1.10

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TCP/IP While 4.3 billion addresses might seem enough, The

world run out of addresses by the end of 2012.

Because most every Computer, Smart Phone, Printer, Game Console, … require IP addresses, IPv4 was insufficient.

Good news! a new internet addressing system has been rolled out, and it fills our need for more addresses. It called IPv6 or IP Version 6.

IPv6 uses 128 bits instead of 32 bits for its addresses, creating 3.4 x 10^38 possible addresses (a trillion-trillion-trillion)

Ex: 21DA:D3:0:2F3B:2AA:FF:FE28:9C5A

3ffe:1900:4545:3:200:f8ff:fe21:67cf

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Domain Name System (DNS)

IP addresses are used to identify hosts on a TCP/IP network

Example: 134.220.1.9 Numbers are not ‘friendly’ – people prefer names DNS is a protocol used to map IP addresses to

textual names e.g. www.mti.edu.eg maps to 184.168.193.49

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Domain Name System (DNS)

DNS names have a hierarchical structure Example: www.mti.edu.eg

Top Level Domain (LTDs)

.

com

Microsoft

net gov eg

com

edu

mti

apps

intro

eLearning…

cu

asu

net …

uk …

Root Level

2nd Level Domain

Subdomains

Domain Name System (DNS)

How a DNS query is resolved When you type mti.edu.eg into your computer’s

web browser i.e. Firefox, Chrome, IE, Spartan, …

1. Type mti.edu.eg in your Browser

2. Query DNS server for mti.edu.eg

Root Server eg Server edu

Server

mti.edu.eg184.168.193.49

3

45

6 7

8

9

10

211

11. Open (connect) 184.168.193.49

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Internet Applications World Wide Web E-mail: E-mail is the most popular form of

business communication-surpassing conventional mail

Instant Messaging (Chatting) FTP: Protocol for copying files between client and

an FTP server E-commerce: Online financial transactions

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Social Networking Social networking site: A site that enables a

community of individuals to communicate and share informationo Facebook, Twitter etc. allow people to post information

about themselveso Video and photo sharing (YouTube, Flickr, etc.)o Used in politics and business (LinkedIn, etc.)

Users should be careful not to reveal too much about themselves for safety reasons

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Net Etiquettes Netiquette is a set of rules for properly behaving online. These

rules are intended to enhance the quality of discussion. Adhere to the same standards of behaviors online that you

follow in real life. Treat e-mail that you receive as confidential unless the sender

specifically gives you permission to share it with others. Respect the copyright and license agreements of material

written by others. If you quote something from a book or magazine, mention your source.

Typing messages in all caps is as bad as shouting Do not assume any Internet communication to be completely

secure Use abbreviations sparingly; overuse can make your message

difficult to understand.

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Myths About the Internet

Myth 1: The Internet is freeo Most people and businesses pay for Internet accesso Businesses & schools lease internet lines from phone companieso Fee-based content is growing at a rapid pace

• Music/movie downloads• Donation based sites

Myth 2: Someone controls the Interneto No single group or organization controls the Interneto Governments can regulate Internet use within its country, but

difficult to enforce

Myth 3: The Internet and World Wide Web are identicalo Internet = physical networko WWW = one resource (Web pages) available via the Internet

THANK YOU