Chapter 0
Computers 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
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Outline
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•
•
•
•
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What are computers?
Why computer networks?
What are computer networks?
The Internet
Evolution of connections
Applications
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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, …
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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.
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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.
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What Are Computer Networks? (cont)
• Directions of the evolvement of computer
networks
– Local Area Network (LAN) for file/printer
sharing, such as Microsoft Network
Neighborhood.
– Wide Area Network (WAN) for global
communications, such as the Internet.
– The boundary is getting blurred.
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The Internet
• The Internet
– A global network with the interconnection of
hosts/networks running TCP/IP.
– TCP/IP is a free/open standard. Any
manufactures can incorporate it into their
products.
– Cross-platform with global coverage.
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The Internet (cont)
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The Internet (cont)
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The Internet (cont)
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The Internet (cont)
• Typical applications
– E-mail, remote login, file transfer, world-wideweb, 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.
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The Internet (cont)
• Service paradigms
– Client-server architecture
– Peer-to-peer architecture
– Hybrid architecture
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The Internet (cont)
• Client-server architecture
4. Client machine is
powered on and
connected to Internet
when necessary.
6. Request for a
particular web page.
Internet
7. Response with
requested web page.
5. HTTP client (browser),
such as Internet Explorer,
is invoked.
2008 Spring
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.
8. HTTP client parses and
displays web pages on screen.
C.-S. Shieh, EC, KUAS, Taiwan
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Evolution of Connections
• Core
– Frame-relay
– ATM
– …
• Edge (last mile)
–
–
–
–
–
–
–
–
Modem
ADSL
Cable-TV
Ethernet
802.11
3G/UMTS
WiMAX
…
2008 Spring
Cited from James F. Kurose and Keith W. Ross, Computer Networking:
A Top-Down Approach Featuring the Internet, 2nd Ed., Addison Wesley
C.-S. Shieh, EC, KUAS, Taiwan
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Evolution of Connections (cont)
• Modem
– Using voice band (<4K Hz)
– V.92 at 56Kbps
– Free for now
Internet
Public Switching Telephone Network
modem
modem
PSTN
Internet Service Provider
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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)
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Evolution of Connections (cont)
Cited from http://www.giga.net.tw
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Evolution of Connections (cont)
• Digital Subscriber Line Access Multiplexer
(DSLAM)
• Broadband Remote Access Server
(BBRAS)
• Radius Server: An authentication and
accounting server for terminal servers that
speak the RADIUS protocol
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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)
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Evolution of Connections (cont)
Cited from http://www.giga.net.tw
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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)
Ethernet LAN
Ethernet LAN
Internet
Ethernet LAN
router
hub
2008 Spring
switching hub
hub
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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
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Evolution of Connections (cont)
Internet
access point
router
hub
2008 Spring
switching hub
hub
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Applications (cont)
• Networking via Mobile Phone Systems
Gateway
GSM/GPRS
Internet
UMTS
Gateway
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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)
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Evolution of Connections (cont)
– 3G: UMTS (Universal Mobile
Telecommunication System)
• 1920 Kbps (384 Kbps in practice)
• 中華電信 3G mPro 商務 450型, 450元/月, (贈送國
內數據50萬封包,約61MB), 每一封包為128 Bytes
• 台灣大哥大 catch 3G 399型, 399元/月, (贈送40MB),
0.0048元/KB
– 3.5G: HSDPA (High Speed downlink Packet
Access)
• 14.4 Mbps
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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
(Orthogonal Frequency Division Modulation)
– 行政院經濟部「台灣WiMAX發展藍圖」, 「WiMAX加
速計畫」
– Fee: ?
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Evolution of Connections (cont)
Cited from 工研院 IEK 2005/08
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Evolution of Connections (cont)
Cited from 工研院 IEK 2005/08
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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.
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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.
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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)
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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
–…
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Applications (cont)
• Instant message
– Microsoft MSN Messenger, Yahoo Messenger,
ICQ, …
– Presence service
– Text chatting, voice conference, video
conference, file transfer, …
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Applications (cont)
1. Alice login
Presence Server
2. Bob login
3. Bob is online
3. Alice is online
Internet
Alice
2008 Spring
4. Text chatting, voice
conference, video conference,
file transfer, …
C.-S. Shieh, EC, KUAS, Taiwan
Bob
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Applications (cont)
• Voice over IP
– Skype, Microsoft MSN Messenger, Google
Talk, …
– 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/zhHant/products/skypeout/rates/all_rates.html
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Applications (cont)
Skype Out
GSM/3G
Gateway
Presence Server
PSTN
David
Internet
Alice
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Gateway
Cindy
Bob
C.-S. Shieh, EC, KUAS, Taiwan
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Applications (cont)
• Multimedia casting
– Network radio, network TV, Web-TV…
– EZTV v 2.018 by 全球網通科技
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Applications (cont)
– Live casting
– SimpleCam v1.3 by Dead Pirate Software
– For surveillance or just show off
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Applications (cont)
• Remote login
– Telent is a text-based remote login.
– SSH is a secure replacement of telnet.
– Remote login with graphic user interface (GUI)
• Remote Desktop for Microsoft Windows
• Virtual Network Computing (VNC) for crossplatform
– As if you are in front of the target machine.
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Applications (cont)
Internet
Remote login
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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
hub
VPN server
connect to VPN
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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
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Applications (cont)
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Applications (cont)
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Applications (cont)
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Applications (cont)
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Applications (cont)
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