Telecommunications & Internet Hun Myoung Park, Ph.D., Public Management and Policy Analysis Program Graduate School of International Relations International University of Japan

Outline  Communication Basics  Transmission Types  Telecommunication Media  Typologies and Types of Network  Packet Switching  Internet and TCP/IP  IP Address and DNS  Internet Services  Web Servers and Browsers 2

Communication Basics  Sender encodes his message.  Receiver decodes (translates) the message received.  Message to be sent  Media through which the message travels (air, radio, TV, phone, Internet, etc.)  Feedback (error checking) 3

Analog vs. Digital Signals  Analog signals: continuous  Frequency  Amplitude  Digital signals: discrete  Modem (modulator/demodulator) converts analog signals to digital ones and vice versa 4

Frequency  Frequency (Hz), the number of times a signal makes a complete cycle per second.  KHz, MHz, GHz  Wavelength: from long (low frequency) to short (high frequency—UHF, cell phone). 5

Bandwidth  Bandwidth (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 6

Transmission Types 1  Serial versus parallel transmission  Wired (faster and more secure) versus wireless network 7

Transmission Types 2  Direction of transmission  Simplex: transmitted in a single direction only  Half-duplex: one direction at a time  Full-duplex: both directions at the same time 8

Transmission Types 3  Timing of transmission  Synchronous: blocks of data are transferred  Asynchronous: start and stop bits to distinguish one byte from the others. 9

Media 1  Twisted-pair wire: RJ-45 (LAN) and RJ-11  Coaxial cable (coax) in the cable TV industry. More expensive, faster, less susceptible to interference (by shield blocking electro-magnetic signals) 10

Media 2  Optical fiber cable uses light pulse sent by a laser device thought the cable.  Super-fast and in turn expensive.  Used for backbone network. 11

Media 4  Radio frequency (RF) transmission  Infrared (IR) transmission  Cellular radio: cell, cellular tower, mobile telephone switching office (MTSO). G3. 13

Media 5  Microwave (“line-of-sight”): communication satellite use microwave stations (microwave antennas) and satellite dishes.  Global positioning systems (GPS), Wi-Fi, Bluetooth 14

Media 7  Telephone lines  Conventional dial-up connection  ISDN (Integrated Services Digital Network)  ADSL (Asymmetric Digital Subscriber Line) and DSL use higher frequency than voce phone call on telephone lines. 16

Media 8  Cable access (cable TV).  Satellite and fixed wireless access need modems and transceivers. 17

Media 9  Wired 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  g and n 18

Network Topologies 1  Star 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 20

Network Topologies 2  Bus 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. 21

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Client-server Network  Servers 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. 23

Peer-to-peer (P2P) network  Direct 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) 24

Types of Network 1  Sharing programs, data, and devices  Access to databases and better security 25

Types of Network 2  LAN (Local Area Network)  Covers small geographical area  Bridge for same types of networks  Router for different networks (layer 3)  Gateway, bridge + router + etc. 26

Types of Network 3  WAN (Wide Area Network)  MAN (Metropolitan Area Network)  VPN (Virtual Private Network) allows remote and secure access to the network (intranet) through encrypted “tunneling” 27

Types of Network 4  Intranet versus extranet  Intranet as a private network used for employees.  Authorized outsiders can access extranets. 28

Circuit vs. Packet Switching  Circuit 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) 29

Packet Switching 1  Paul 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 30

Packet Switching 2  Each 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. 31

Packet Switching 3  The 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. 32

Internet History 1  Systems of interconnected computer networks  ARPAnet (Advanced Research Project Agency) of Department of Defense in

Internet History 2  Packet switching as a method of network communications in the 1960s.  Paul Baran at RAND  Leonard Kleinrock at UCLA 34

Internet History 3  File Transfer Protocol (FTP) in SSH FTP (SFTP)  Mail protocol in (Simple Mail Transfer Protocol) SMTP in 1981  Open Systems Interconnection (OSI) in 1977  Transmission Control Protocol/Internet Protocol (TCP/IP) in

Internet History 4  World Wide Web in 1991  Tim Berners-Lee at CERN  World Wide Web Consortium (W3C) was proposed by Berners- Lee in 1989  Web standard HTML 5.0 in

TCP/IP 1  Internet Protocol Suite  Communication protocol for Internet  Five layers (from the lower one)  Replaced ISO’s OSI w/o session and presentation layers under applications 37

TCP/IP 2 1.Physical layer converts bits into signals on media 2.Data link: node-to-node delivery of frames 3.Network (delivery of packets by routing and Internet Protocol (IP). IPv4 and IPv6 38

TCP/IP 3 4.Transport (logical delivery of messages) 5.Application (provide services to users) 39

IP Address 1  IP address (Internet address) is a numerical label assigned to devices wired on Internet  Network interface identification and location addressing under TCP/IP 41

IP Address 2  IPv4 (32bits); =4,294,967,296  Scarcity of domain names in IPv4  Move toward IPv6 (128bits) in 1998 supporting up to =

IP Address 3  Static versus dynamic IP addresses  Static address has a fixed IP address  Dynamic address is assigned when a machine is networked  Dynamic Host Configuration Protocol (DHCP) server manages dynamic addresses 43

Domain Name Systems 1  Hierarchical 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) 44

Domain Name System 2  Domain names registrations controlled by Internet Corporation for Assigned Names and Numbers (ICANN), nonprofit organization  Domain Name System (DNS) servers  Top-level domain (TLD): com, edu, gov, org, net  Second-level domain (SLD) is one to the left of the TLD: co, ac, … 45

Domain Name System 3  Types of addresses    ype  Root domain: edu, com,..  Domain type:.ac,.co,.re,.go …  Country:.us,.jp,.kr,.fr 46

Web Address 1  Uniform Resource Locator (URL) as a URI (Uniform Resource Identifier)  25/or.html  Protocol or scheme (http, https, ftp, etc.)  Domain name, domain type, country 47

Web Address 2  Port number (  Directory or path (forward slash / not \)  Document name and arguments of CGI (e.g., search.php?key=e- government&book=yes) 48

Internet Services 1  (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 49

Internet Services 2  FTP (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 50

Internet Services 3  Internet chatting (Internet relay chat)  Gopher, browsing and searching services  Usenet (user network) newsgroup of Internet discussion system  Listservs, based discussion groups 51

Internet Services 4  WWW (World Wide Web) integrates other Internet services using hyperlinks  Web servers and browsers  HTTP (Hypertext Transfer Protocol)  Static and dynamic documents (HTML)  CGI (Common Gateway Interface)  Plug-in or applets (Java applets) 52

Web Servers  Process 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) 53

Web Browsers 1  Interpret 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) 54

Web Browsers 2  Web standards: Mozilla and Firefox  Web compatible: Safari, Google chrome  Others: Opera, Konqueror  Text-based: Lynx  Microsoft Internet Explorer (MSIE) and ActivX do not comply with Web standards 55

Web Features and Web 2.0  Interface for input and output of text, image, audio, and video  Replacing or integrating existing Internet services like FTP, Gopher, Listservs.  Push technology (Webcasting) for information delivery by software  Improved interactivity  Web 2.0  Internet radio and television 56