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WWW and the Internet Bus Different types of networks LAN (Local Area Network) Connects network devices over a relatively short distance Office Building / University / Home Possible topologies: Different types of networks MAN (Metropolitan Area Network) Connects an area larger than a LAN

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different types of networks

Bus

Different types of networks
  • LAN (Local Area Network)
  • Connects network devices over a relatively short distance
  • Office Building / University / Home
  • Possible topologies:

Copyright © 2005. Exclusive rights by The McGraw-Hill Companies, Inc.

different types of networks3
Different types of networks
  • MAN (Metropolitan Area Network)
  • Connects an area larger than a LAN
  • Connect Cities / States

WAN (Wide Area Network)

  • Spans most of the world
  • Formed by connecting LANs and MANs (with routers)
  • E.g. Internet

Copyright © 2005. Exclusive rights by The McGraw-Hill Companies, Inc.

routers
Routers

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www vs internet
WWW vs. Internet
  • Internet
    • A worldwide system of computer networks
    • Users at any one computer can, if they have permission, get information from any other computer
  • Web
    • Graphical user interface (GUI) on top of the Internet

Copyright © 2005. Exclusive rights by The McGraw-Hill Companies, Inc.

history of internet
History of internet
  • Who owns the internet?
  • Who operates the internet?
  • 1969: U.S. military established the initial computer network (ARPANet)
  • 1991: Tim Berners-Lee created a program for sharing of files
  • Mosaic  Netscape  IE
  • 130 Web sites in 1993, now > 25 million

Copyright © 2005. Exclusive rights by The McGraw-Hill Companies, Inc.

search engine
Search engine
  • Search engine
    • Facility on the Web
  • 2 types
    • Directory search engine
      • Hierarchical organization
    • True search engine
      • Search the web for keywords

Search for: Charles Babbage (father of computing)

Copyright © 2005. Exclusive rights by The McGraw-Hill Companies, Inc.

hardware for communication
Hardware for communication
  • Modem - a device that sends and receives data over telephone lines to and from computers
  • There are two types of modems – internal and external

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hardware for communication9

External Modem

Internal Modem (PCI)

Two connectors, one connected to telephone,

and the other to telephone socket (wall)

Once you’re using modem, the telephone is not usable

Hardware for communication

Some modems have value-added functions:

e.g. FAX, automatic answering machine

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hardware for communication10
Hardware for communication
  • Modem – (Modulator / Demodulator)
  • Copper telephone line is analog in nature
  • Digital Signal would be distorted if it is directly sent via telephone line
  • Modem (sender side) encodes digital signal to analog form and convert it back to digital signal at receiver side
  • Modulation schemes:
    • Amplitude Modulation (AM)
    • Frequency Modulation (FM)
    • Phrase Modulation (PM)
    • Hybrid/Combination Schemes

Copyright © 2005. Exclusive rights by The McGraw-Hill Companies, Inc.

hardware for web surfing
Hardware for web surfing
  • Web computer
    • Scaled down version of computer system
    • Used for web access, email, maybe some simple task

http://www.hitachi.co.jp/Prod/vims/wia/index.html

http://www.mailbug.com/

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slide12
WebTV
    • Cable TV with web access through cable

http://www.sky.com

http://www1.sky.com/skyactive/whatisSkyActive/

  • Web phones
    • Browse the web with microbrowser
    • Limitation
  • PDA

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software for web surfing
Software for web surfing
  • Web browser
    • Main objective is to communicate over the Internet with Web servers using HTTP
    • Interpret hypertext documents and formatted it on screen
    • Types of browser:
      • Text-based

e.g. Lynx

Point-And-Click Graphical User Interface

e.g. Cello, Mosaic, Netscape, Internet Explorer

Copyright © 2005. Exclusive rights by The McGraw-Hill Companies, Inc.

internet connection
Internet connection

Your home computer

Destination computer

Local ISP

Local ISP

Network Access

Point (NAP) at

another place

Network Access

Point (NAP)

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internet service provider isp
Internet Service Provider (ISP)
  • A company that provides access to the Internet
  • How to choose a good ISP?
    • Features

e.g. Speed, Web space, Email account

    • Technical support
    • Installation
    • Privacy
    • Price

Copyright © 2005. Exclusive rights by The McGraw-Hill Companies, Inc.

internet service provider isp16
Internet Service Provider (ISP)
  • More features with commercial ISPs
    • Personalized name for your site
    • More than 30 email accounts
    • Spam email filter
    • Larger storage space
  • Free ISPs

www.netzero.net

www.juno.com

Copyright © 2005. Exclusive rights by The McGraw-Hill Companies, Inc.

major isps in hong kong
Major ISPs in Hong Kong

How to interpret the information ?

Generally speaking, download speed is more

Important than upload speed

(e.g. when requesting a homepage/image)

However, there are exceptions

(e.g. using video conferencing / BT)

Upload:

Sending information from your machine to others

Download:

Receiving information from the others to your machine

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major isps in hong kong18

‘M’ means 220, which is roughly equals to 1,000,000

‘k’ means 210 (=1024), which is roughly equals to 1,000

“bps”: bits per second

The unit specifying transmission speed.

(a bit is either a “0” or “1”)

Note that “bps” is in lower case.

If it is written as “Bps” (capital B),

It means bytes per second

1 byte = 8 bits, which can be though of as a single character

Major ISPs in Hong Kong

Copyright © 2005. Exclusive rights by The McGraw-Hill Companies, Inc.

major isps in hong kong19

Also need to consider whether it is “10Mbps for each client”, or

“10Mbps for the whole building”

Major ISPs in Hong Kong

Transmission speed of some ISP may be affected by geographical location

Copyright © 2005. Exclusive rights by The McGraw-Hill Companies, Inc.

internet structure network of networks
Roughly Hierarchical

At center:“tier-1” ISPs

For Example: UUNet, BBN/Genuity, Sprint, AT&T

National/international coverage

Treat each other as equals

NAP

Tier-1 providers also interconnect at public network access points (NAPs)

Tier-1 providers interconnect (peer) privately

Tier 1 ISP

Tier 1 ISP

Tier 1 ISP

Internet structure: network of networks

Ref: Computer Networking: A Top Down Approach Featuring the Internet, 3rd edition.Jim Kurose, Keith Ross Addison-Wesley, July 2004.

Copyright © 2005. Exclusive rights by The McGraw-Hill Companies, Inc.

tier 1 isp e g sprint
Tier-1 ISP: e.g., Sprint

Sprint US backbone network

Copyright © 2005. Exclusive rights by The McGraw-Hill Companies, Inc.

internet structure network of networks22
“Tier-2” ISPs: smaller (often regional) ISPs

Connect to one or more tier-1 ISPs, possibly other tier-2 ISPs

NAP

Tier-2 ISPs also peer privately with each other, interconnect at NAP

  • Tier-2 ISP pays tier-1 ISP for connectivity to rest of Internet
  • tier-2 ISP is customer of

tier-1 provider

Tier-2 ISP

Tier-2 ISP

Tier-2 ISP

Tier-2 ISP

Tier-2 ISP

Internet structure: network of networks

Tier 1 ISP

Tier 1 ISP

Tier 1 ISP

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internet structure network of networks23
“Tier-3” ISPs and local ISPs

last hop (“access”) network (closest to end systems)

Tier 3

ISP

local

ISP

local

ISP

local

ISP

local

ISP

local

ISP

local

ISP

local

ISP

local

ISP

NAP

Local and tier- 3 ISPs are customers of

higher tier ISPs

connecting them to rest of Internet

Tier-2 ISP

Tier-2 ISP

Tier-2 ISP

Tier-2 ISP

Tier-2 ISP

Internet structure: network of networks

Tier 1 ISP

Tier 1 ISP

Tier 1 ISP

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internet structure network of networks24
a packet passes through many networks!

Tier 3

ISP

local

ISP

local

ISP

local

ISP

local

ISP

local

ISP

local

ISP

local

ISP

local

ISP

NAP

Tier-2 ISP

Tier-2 ISP

Tier-2 ISP

Tier-2 ISP

Tier-2 ISP

Internet structure: network of networks

Tier 1 ISP

Tier 1 ISP

Tier 1 ISP

Copyright © 2005. Exclusive rights by The McGraw-Hill Companies, Inc.

voice over internet
Voice over internet
  • Apart from data file, internet can also be used for transmitting voice information
  • PC-to-phone
  • Phone-to-internet-to-phone
  • Advantages:
    • Lower cost for long-distance telephone service
    • Other services such as Group-Communication,
    • Caller filtering
    • It’s possible to transmit video information also

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references
References
  • S. Haag, M. Cummings and A. Rea Jr., Computing Concepts, McGraw-Hill, 2002, Ch. 2
  • Williams . Sawyer, “Using Information Technology”, 6th edition, McGraw-Hill, 2005, Ch. 2
  • James F. Kurose, Keith W. Ross, “Computer Networking”, 3rd edition, Addison Wesley, 2004, Ch 1.5

Copyright © 2005. Exclusive rights by The McGraw-Hill Companies, Inc.