2008 springc.-s. shieh, ec, kuas, taiwan1 chapter 0 computers and the internet chin-shiuh shieh (...

2008 Spring C.-S. Shieh, EC, KUAS, Taiwan 1

Chapter 0Computers and the Internet

Chin-Shiuh Shieh (謝欽旭 )http://bit.kuas.edu.tw/~csshieh

Department of Electronic Engineering

National Kaohsiung University of Applied Sciences, Taiwan


Outline

• What are computers?

• Why computer networks?

• What are computer networks?

• The Internet

• Evolution of connections

• Applications


What Are Computers?

• Computers are powerful tools for (generalized) computation– Numerical analysis, database, document

processing, control, gaming, …• Computers are fast, precise, and highly flexible.• Complementary roles between man and

machine– Human being: Thinking, innovating, …– Machine: Data processing, computation, …


Why Computer Networks?

• A single computer, however powerful, is an isolated island.

• A computer can increase its power by communicating with others:– More information, more computing power,

more reliable service, …

• Computer networks allow for information exchange at the speed of light.


What Are Computer Networks?

• Computer networks consist of– Physical connections:

• Cable, optical fiber, radio channel, …

– Communication protocols:• Defining the format, timing of signals/packets at

different layers.• Different protocols make different network

systems.

– Applications:• Client/server programs for different services.


What Are Computer Networks? (cont)

• Directions of the evolvement of computer networks– Local Area Network (LAN) for file/printer shari

ng, such as Microsoft Network Neighborhood.– Wide Area Network (WAN) for global commun

ications, such as the Internet.– The boundary is getting blurred.


The Internet

• The Internet– A global network with the interconnection of h

osts/networks running TCP/IP.– TCP/IP is a free/open standard. Any manufact

ures can incorporate it into their products.– Cross-platform with global coverage.


The Internet (cont)


The Internet (cont)

• Typical applications– E-mail, remote login, file transfer, world-wide-

web, remote control, instant message, voice over IP, video conference, blog, …

– Possible applications are limited only by one’s imagination.

– All node on Internet are born to be equal. To be a client or a server depends on your decision.


The Internet (cont)

• Service paradigms– Client-server architecture– Peer-to-peer architecture– Hybrid architecture


The Internet (cont)

Internet

1. Server machine is powered on and

connected to Internet all the time.

2. HTTP server (web server), such as

apache, is running on server machine.

3. Web pages to be served are placed on

server.

4. Client machine is powered on and

connected to Internet when necessary.

5. HTTP client (browser), such as Internet Explorer,

is invoked.

6. Request for a particular web page.

7. Response with requested web page.

8. HTTP client parses and displays web pages on screen.

• Client-server architecture


Evolution of Connections

• Core– Frame-relay– ATM– …

• Edge (last mile)– Modem– ADSL– Cable-TV– Ethernet– 802.11– 3G/UMTS– WiMAX– …

Cited from James F. Kurose and Keith W. Ross, Computer Networking: A Top-Down Approach Featuring the Internet, 2nd Ed., Addison Wesley


Evolution of Connections (cont)

• Modem– Using voice band (<4K Hz)– V.92 at 56Kbps– Free for now

PSTN

Internet

Public Switching Telephone Network

Internet Service Provider

modem modem



• ADSL (Asymmetric Digital Subscriber Line )– Using band beyond voice (>4K Hz)– ADSL modem, Ethernet card– 1M/64K, 2M/256K, 8M/640K, …– 2M/256K at NT$840 per month (Hinet)



• Cable-TV– Using channels not for casting– Cable modem– 1.5M/64K, 3M/256K, 6M/256K, …– 3M/256K at NT$850 per month (Giga.net)



• Ethernet– Ethernet card, hub, switching hub– 10Mbps, 100Mbps, 1000Mbps– Carrier Sense Multiple Access with Collision

Detection (CSMA/CD)



Internet

hub hubswitching hub

router

Ethernet LANEthernet LAN

Ethernet LAN


Evolution of Connections (cont

• IEEE 802.11– Wireless LAN, Wi-Fi– 802.11 wireless network card, access point– 11Mbps (802.11b), 55Mbps (802.11g)– Tens of meters or next two doors– Wireless extension to Ethernet



Internet

hub hubswitching hub

router

access point



Internet

Gateway

GSM/GPRS

Gateway

UMTS

• Networking via Mobile Phone Systems



• Networking via Mobile Phone Systems– 1G: Advanced Mobile Phone System– 2G: GSM (Global System for Mobile

Communication)• Circuit-switched• 14.4 Kbps

– 2.5G: GPRS (General packet Radio Service)• Packet-switched• 160Kbps (30-80 Kbps in practice)



– 3G: UMTS (Universal Mobile Telecommunication System)

• 1920 Kbps (384 Kbps in practice)

– 3.5G: HSDPA (High Speed downlink Packet Access)

• 14.4 Mbps



• WiMAX– Worldwide Interoperability for Microwave Access, 中文譯名為「無線都會區域網路」

– IEEE 802.16-2004 (WiMAX), IEEE 802.16e (Mobile WiMAX)

– Up to 75Mbps, 50Km, Wireless MAN (Metropolitan Area Network)

– Last mile alternative to cable and DSL– Scheduling MAC (Media Access Control), OFDM (Ort

hogonal Frequency Division Modulation)– 行政院經濟部「台灣WiMAX 發展藍圖」 , 「 WiMAX加速計畫」


Network Topology in My House

ADSL Modem

IEEE 802.11Access Point

1Gbps


Applications

• Classical applications– E-mail, file transfer, remote login, bullet board

system, gopher, archie, netnews, IRC (Internet Relay Chat, exchange text messages interactively with other people all over the world) , …

– Attachments in E-mails allow for the transfer of files of any types.

– Web-based E-mail client is convenient when you are out.


Applications (cont)

• The raise of world-wide-web– Hyper-Text Markup Language– Presentation with multimedia, including text,

graph, audio, video, animation, …– Hyperlinks for cross-reference– Integration of other services, such as E-mail,

file downloading, telnet, …– Excellent platform for promotion for both

enterprises and individuals.


Applications (cont)

• Interactive technologies bring WWW into new dimensions– E-commerce, database access, web search,

remote control, …– Programming is involved

• JavaScript / VBScript at client end• Active Server Page (ASP, Microsoft) / PHP:

Hypertext Preprocessor at server end• Common Gateway Interface Programming (CGI)


Applications (cont)

• Web 2.0– Not a brand new technology, but a new concept– blogs and wikis– A wiki is a type of website that allows users to easily

add, remove, or otherwise edit and change some available content, sometimes without the need for registration "Wiki-wiki" means "hurry quick" in Hawaiian. It also refers to a type of native fish of the islands (from wikiapedia).


Applications (cont)

– Users turn their roles from audiences to authors

–人人皆可著書立說


Applications (cont)

• Recent applications– Instant message– Voice over IP– Multimedia streaming– Remote login, Wake-On-LAN– P2P– …


Applications (cont)

• Instant message– Microsoft MSN Messenger, Yahoo

Messenger, ICQ, …– Presence service– Text chatting, voice conference, video

conference, file transfer, …


Applications (cont)

Internet

Presence Server

Alice Bob

1. Alice login

2. Bob login

3. Bob is online3. Alice is online

4. Text chatting, voice conference, video conference,

file transfer, …


Applications (cont)

• Voice over IP– Skype, Microsoft MSN Messenger, Google Ta

lk, …– Presence service, gateway to PSTN, GSM– Free for PC-to-PC– Charged for PC-to-Phone (Skype Out)

• € 0.017 per minute to USA, UK, Taiwan, China, …• € 0.082 per minute to Taiwan mobile• http://www.skype.com/intl/zh-Hant/products/skypeo

ut/rates/all_rates.html


Applications (cont)

Internet

Presence Server

Alice Bob

PSTN

Gateway

GSM/3G

Gateway

Cindy

David

Skype Out


Applications (cont)

• Multimedia casting– Network radio, network TV, Web-TV…– EZTV v 2.018 by 全球網通科技


Applications (cont)

– Live casting– SimpleCam v1.3 by Dead Pirate Software– For surveillance or just show off


Applications (cont)

• Remote login– Telent is a text-based remote login.– SSH is a secure replacement of telnet.– Remote login with graphic user interface (GU

I)• Remote Desktop for Microsoft Windows• Virtual Network Computing (VNC) for cross-platfor

m

– As if you are in front of the target machine.


Applications (cont)

Internet

Remote login


Applications (cont)

• Virtual Private Network (VPN)– As if you and your machine are in the target domain– For access of restricted data in the target domain

Internet

connect to VPN

hub

VPN server


Applications (cont)

• Peer-to-Peer (P2P) applications– Each node acts both as a client and a server– Distribution of large files– eMule, BitTorrent, …– Warning: illegal use of legal applications


Applications (cont)

2008 springc.-s. shieh, ec, kuas, taiwan1 chapter 0 computers and the internet chin-shiuh shieh (...

Documents

internet cont internet

internet cont slide

internet explorer

taiwan slide

internet chinshiuh shieh

single computer

server machine

http server web server