2008 springc.-s. shieh, ec, kuas, taiwan1 chapter 0 computers and the internet chin-shiuh shieh (...
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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
2008 Spring C.-S. Shieh, EC, KUAS, Taiwan 2
Outline
• What are computers?
• Why computer networks?
• What are computer networks?
• The Internet
• Evolution of connections
• Applications
2008 Spring C.-S. Shieh, EC, KUAS, Taiwan 3
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, …
2008 Spring C.-S. Shieh, EC, KUAS, Taiwan 4
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.
2008 Spring C.-S. Shieh, EC, KUAS, Taiwan 5
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.
2008 Spring C.-S. Shieh, EC, KUAS, Taiwan 6
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.
2008 Spring C.-S. Shieh, EC, KUAS, Taiwan 7
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.
2008 Spring C.-S. Shieh, EC, KUAS, Taiwan 11
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.
2008 Spring C.-S. Shieh, EC, KUAS, Taiwan 12
The Internet (cont)
• Service paradigms– Client-server architecture– Peer-to-peer architecture– Hybrid architecture
2008 Spring C.-S. Shieh, EC, KUAS, Taiwan 13
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
2008 Spring C.-S. Shieh, EC, KUAS, Taiwan 14
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
2008 Spring C.-S. Shieh, EC, KUAS, Taiwan 15
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
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Evolution of Connections (cont)
• 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)
2008 Spring C.-S. Shieh, EC, KUAS, Taiwan 17
Evolution of Connections (cont)
• 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)
2008 Spring C.-S. Shieh, EC, KUAS, Taiwan 18
Evolution of Connections (cont)
• Ethernet– Ethernet card, hub, switching hub– 10Mbps, 100Mbps, 1000Mbps– Carrier Sense Multiple Access with Collision
Detection (CSMA/CD)
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Evolution of Connections (cont)
Internet
hub hubswitching hub
router
Ethernet LANEthernet LAN
Ethernet LAN
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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
2008 Spring C.-S. Shieh, EC, KUAS, Taiwan 21
Evolution of Connections (cont)
Internet
hub hubswitching hub
router
access point
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Evolution of Connections (cont)
Internet
Gateway
GSM/GPRS
Gateway
UMTS
• Networking via Mobile Phone Systems
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Evolution of Connections (cont)
• 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)
2008 Spring C.-S. Shieh, EC, KUAS, Taiwan 24
Evolution of Connections (cont)
– 3G: UMTS (Universal Mobile Telecommunication System)
• 1920 Kbps (384 Kbps in practice)
– 3.5G: HSDPA (High Speed downlink Packet Access)
• 14.4 Mbps
2008 Spring C.-S. Shieh, EC, KUAS, Taiwan 25
Evolution of Connections (cont)
• 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」
2008 Spring C.-S. Shieh, EC, KUAS, Taiwan 26
Network Topology in My House
ADSL Modem
IEEE 802.11Access Point
1Gbps
2008 Spring C.-S. Shieh, EC, KUAS, Taiwan 27
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.
2008 Spring C.-S. Shieh, EC, KUAS, Taiwan 28
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.
2008 Spring C.-S. Shieh, EC, KUAS, Taiwan 29
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)
2008 Spring C.-S. Shieh, EC, KUAS, Taiwan 30
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).
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Applications (cont)
– Users turn their roles from audiences to authors
–人人皆可著書立說
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Applications (cont)
• Recent applications– Instant message– Voice over IP– Multimedia streaming– Remote login, Wake-On-LAN– P2P– …
2008 Spring C.-S. Shieh, EC, KUAS, Taiwan 33
Applications (cont)
• Instant message– Microsoft MSN Messenger, Yahoo
Messenger, ICQ, …– Presence service– Text chatting, voice conference, video
conference, file transfer, …
2008 Spring C.-S. Shieh, EC, KUAS, Taiwan 34
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, …
2008 Spring C.-S. Shieh, EC, KUAS, Taiwan 35
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
2008 Spring C.-S. Shieh, EC, KUAS, Taiwan 36
Applications (cont)
Internet
Presence Server
Alice Bob
PSTN
Gateway
GSM/3G
Gateway
Cindy
David
Skype Out
2008 Spring C.-S. Shieh, EC, KUAS, Taiwan 37
Applications (cont)
• Multimedia casting– Network radio, network TV, Web-TV…– EZTV v 2.018 by 全球網通科技
2008 Spring C.-S. Shieh, EC, KUAS, Taiwan 38
Applications (cont)
– Live casting– SimpleCam v1.3 by Dead Pirate Software– For surveillance or just show off
2008 Spring C.-S. Shieh, EC, KUAS, Taiwan 39
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.
2008 Spring C.-S. Shieh, EC, KUAS, Taiwan 41
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
2008 Spring C.-S. Shieh, EC, KUAS, Taiwan 42
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