Telecommunications & Internet

Hun Myoung Park, Ph.D.,

Public Management and Policy Analysis ProgramGraduate School of International Relations

International University of Japan

OutlineCommunication BasicsTransmission TypesTelecommunication MediaTypologies and Types of NetworkPacket SwitchingInternet and TCP/IPIP Address and DNS Internet ServicesWeb Servers and Browsers

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Communication BasicsSender encodes his message.Receiver decodes (translates) the

message received.Message to be sentMedia through which the

message travels (air, radio, TV, phone, Internet, etc.)

Feedback (error checking)

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Analog vs. Digital SignalsAnalog signals: continuousFrequencyAmplitude

Digital signals: discrete

Modem (modulator/demodulator) converts analog signals to digital ones and vice versa

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FrequencyFrequency (Hz), the number of

times a signal makes a complete cycle per second.

KHz, MHz, GHzWavelength: from long (low

frequency) to short (high frequency—UHF, cell phone).

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BandwidthBandwidth (bps) is ranges of

frequencies. The difference between the

highest and lowest frequency transmitted or amount of data transmitted per second.

Bps (bit per second) Kbps, Mbps. Baud (pulses per second) or modulation rate

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Transmission Types 1Serial versus parallel

transmissionWired (faster and more secure)

versus wireless network

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Transmission Types 2Direction of transmission Simplex: transmitted in a single

direction only Half-duplex: one direction at a

time Full-duplex: both directions at

the same time

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Transmission Types 3Timing of transmission Synchronous: blocks of data are

transferred Asynchronous: start and stop

bits to distinguish one byte from the others.

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Media 1Twisted-pair wire: RJ-45 (LAN) and

RJ-11Coaxial cable (coax) in the cable

TV industry. More expensive, faster, less susceptible to interference (by shield blocking electro-magnetic signals)

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Media 2Optical fiber cable uses light

pulse sent by a laser device thought the cable.

Super-fast and in turn expensive. Used for backbone network.

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Media 4Radio frequency (RF)

transmissionInfrared (IR) transmissionCellular radio: cell, cellular tower,

mobile telephone switching office (MTSO). G3.

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Media 5Microwave (“line-of-sight”):

communication satellite use microwave stations (microwave antennas) and satellite dishes.

Global positioning systems (GPS), Wi-Fi, Bluetooth

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Media 7Telephone linesConventional dial-up connectionISDN (Integrated Services

Digital Network) ADSL (Asymmetric Digital

Subscriber Line) and DSL use higher frequency than voce phone call on telephone lines.

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Media 8Cable access (cable TV).Satellite and fixed wireless

access need modems and transceivers.

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Media 9Wired Ethernet (T1, T3)Broadband over fiber (BoF) Cellular broadband or mobile

wireless (laptops, smart phones)Wi-Fi (Wireless Fidelity) is

wireless networking standards (wireless Ethernet)

IEEE 802.11802.11g and 802.11n

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Network Topologies 1Star network has a central hub

(router) connected by other devices.

Ring network: devices are connected from one node to the next. One-way direction of transmission. IBM’s Token Ring Network

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Network Topologies 2Bus network has a central bus

line to which devices (nodes) are attached.

Mesh network: each device is connected to multiple devices in a network.

Hybrid network combines above typologies.

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Client-server NetworkServers process clients’ request

and provide services to clients. Does not mean particular

machines but roles and functions.Depending on tasks, network, file,

mail, Web, DNS, printer, license servers and others are available.

A single machine can run more than one servers.

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Peer-to-peer (P2P) networkDirect access to other devices

without central servers.P2P servers mange indexes, not

contents, to bridge users.Used to share resources online but

likely to infringe intellectual property rights.

Suck down all available computing resources (network congestion)

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Types of Network 1Sharing programs, data, and

devicesAccess to databases and better

security

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Types of Network 2LAN (Local Area Network)Covers small geographical areaBridge for same types of

networks Router for different networks

(layer 3)Gateway, bridge + router + etc.

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Types of Network 3WAN (Wide Area Network)MAN (Metropolitan Area Network)VPN (Virtual Private Network)

allows remote and secure access to the network (intranet) through encrypted “tunneling”

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Types of Network 4Intranet versus extranet

Intranet as a private network used for employees.

Authorized outsiders can access extranets.

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Circuit vs. Packet SwitchingCircuit switching establishes a

connection (physical path and circuit) that cannot be use by others. PSTN (public switched telephone network)

Packet switching sends data in a series of packets and then assembles them in the destination. PSDN (public switched data network)

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Packet Switching 1Paul Baran, Donald Davies,

Leonard Kleinrock in the 1960s. Data are split into small chunks,

“packets”Each packet has a header with

information about its sequence number and the destination

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Packet Switching 2Each packet may independently

travel a different routes to get to the destination and be buffered and queued depending on network traffic.

No order in transmission.

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Packet Switching 3The packet header at the

destination is stripped off and then packets are put together (assemble) in the proper order.

In case of failures of packets (e.g., damaged), they will be requested and sent again.

Safe way to communicate each other.

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Internet History 1Systems of interconnected

computer networksARPAnet (Advanced Research

Project Agency) of Department of Defense in 1969

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Internet History 2Packet switching as a method of

network communications in the 1960s.

Paul Baran at RAND Leonard Kleinrock at UCLA

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Internet History 3File Transfer Protocol (FTP) in

1971. SSH FTP (SFTP)Mail protocol in 1973. (Simple Mail

Transfer Protocol) SMTP in 1981Open Systems Interconnection

(OSI) in 1977Transmission Control

Protocol/Internet Protocol (TCP/IP) in 1983

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Internet History 4World Wide Web in 1991Tim Berners-Lee at CERNWorld Wide Web Consortium

(W3C) was proposed by Berners-Lee in 1989

Web standard HTML 5.0 in 2014

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TCP/IP 1Internet Protocol SuiteCommunication protocol for

InternetFive layers (from the lower one)Replaced ISO’s OSI w/o session

and presentation layers under applications

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TCP/IP 21. Physical layer converts bits into

signals on media2. Data link: node-to-node

delivery of frames3. Network (delivery of packets by

routing and Internet Protocol (IP). IPv4 and IPv6

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TCP/IP 34. Transport (logical delivery of

messages)5. Application (provide services to

users)

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IP Address 1IP address (Internet address) is a

numerical label assigned to devices wired on Internet

Network interface identification and location addressing under TCP/IP

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IP Address 2IPv4 (32bits);

28.28.28.28=4,294,967,296Scarcity of domain names in IPv4Move toward IPv6 (128bits) in

1998 supporting up to 2128 = 28.28.28.28.28.28

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IP Address 3Static versus dynamic IP

addressesStatic address has a fixed IP

addressDynamic address is assigned

when a machine is networked Dynamic Host Configuration

Protocol (DHCP) server manages dynamic addresses

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Domain Name Systems 1Hierarchical naming systems

translates a human friendly name to its associated IP address

Identification string of memorable names for Internet resources (e.g., computer, network, and service)

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Domain Name System 2Domain names registrations controlled

by Internet Corporation for Assigned Names and Numbers (ICANN), nonprofit organization

Domain Name System (DNS) serversTop-level domain (TLD): com, edu, gov,

org, net Second-level domain (SLD) is one to

the left of the TLD: co, ac, …

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Domain Name System 3Types of email addresses

User_ID@domain.root_domain_typeUser_ID@domain.domain_type.countr

yUser_ID@subdomain.domain.domain_

type

Root domain: edu, com, ..Domain type: .ac, .co, .re, .go … Country: .us, .jp, .kr, .fr

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Web Address 1Uniform Resource Locator (URL)

as a URI (Uniform Resource Identifier)

http://www.iuj.ac.jp/faculty/kucc625/or.html

Protocol or scheme (http, https, ftp, etc.)

Domain name, domain type, country

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Web Address 2Port number

(http://www.iuj.ac.jp:80)Directory or path (forward slash /

not \) Document name and arguments

of CGI (e.g., search.php?key=e-government&book=yes)

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Internet Services 1E-mail (Electronic mail) SMTP (Simple Mail Transfer

Protocol) MIME (Multipurpose Internet Mail

Extension)POP (Post Office Protocol) IMAP (Internet Mail Access

Protocol)Most reliable and widely used

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Internet Services 2FTP (Filer transfer protocol) Telnet (Terminal Network) for

establishing remote connection. Traditional FTP and Telnet have

security problems and were thus replaced by secured FTP (SFTP) and secured telnet.

SSH (Secured shell) includes both SFTP and Secured telnet

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Internet Services 3Internet chatting (Internet relay

chat)Gopher, browsing and searching

services Usenet (user network) newsgroup

of Internet discussion systemListservs, e-mail based discussion

groups

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Internet Services 4WWW (World Wide Web)

integrates other Internet services using hyperlinks Web servers and browsersHTTP (Hypertext Transfer Protocol)Static and dynamic documents

(HTML)CGI (Common Gateway Interface)Plug-in or applets (Java applets)

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Web ServersProcess requests from Web

browsers and send the result back to the browsers

Use CGI to generate dynamic documents

Apache (HTTP/Tomcat), IIS (Microsoft), other vendors’ products (IBM, Oracle, etc.)

Server-side scripts (SSI)

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Web Browsers 1Interpret markup languages

(HTML/XML) and display the result on the screen

This process is called as Web rendering

Each Web browser has its own rendering engine that has different default values in settings.

May include plug-ins (add-ons)

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Web Browsers 2Web standards: Mozilla and

FirefoxWeb compatible: Safari, Google

chromeOthers: Opera, KonquerorText-based: LynxMicrosoft Internet Explorer (MSIE)

and ActivX do not comply with Web standards

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Web Features and Web 2.0Interface for input and output of

text, image, audio, and videoReplacing or integrating existing

Internet services like FTP, Gopher, Listservs.

Push technology (Webcasting) for information delivery by software

Improved interactivity Web 2.0Internet radio and television

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