Chapter 5 Introduction to Telecommunications Applications of Telecommunications

Chapter 5 Introduction to Telecommunications

Applications of Telecommunications O’Brien 121 Business Telecommunications Architectures Electronic communications system • • • Electronic mail Voice mail Bulletin Board systems Videotex Fascimile Public Information Service Electronic meeting systems • Desktop Video conferencing • Decision room conferencing • Computer conferencing • Teleconferencing • • • Centralized Distributed Client/server Interorganizational Global Business process systems • Online transaction processing • Inquiry/Response • EDI / XML • Electronic Funds Transfer • Activity monitoring • Process control • Telecommuting

Trends O’Brien 122 - 124 Industry trends Towards a greater number of competitive vendors, carriers, alliances and telecommunications network services. Technology trends Towards open and interconnected local and global digital networks for voice, data and video, using high-speed fiber-optics and satellites. Application Trends Towards a pervasive use of the internet and enterprise and interorganizational intranets, to support collaborative computing, online business operations and strategic advantage in local and global markets.

Technological Developments General trend: Connect everybody to everybody else. § Internet-network technologies ð thousands new hardware- and software products ð web-browsers, HTML- editors, firewalls § Open systems: based on standards ð connectivity of systems: middleware ð OSI, TCP/IP § Digital technologies ð higher transmission speed ð larger information streams ð more efficient transmission method ð less errors text: O’Brien : p. 168

Internet Revolution § § Explosive growth Terminology ð WWW: inquiry sources of information via graphical browser software ð E-mail: electronic mail ð Usenet: place messages on bulletin board ð IRC: real time dialogs ð FTP: file transfer ð Telnet: login on other systems ð Other: telephone, video conferencing, . . . text: O’Brien : p. 172

Telecommunication model § O’Brien 125 Terminals ð terminal, office equipment , telephones , . . . § Telecommunications processors ð modems, multiplexers, front-end processors, . . . § Telecommunications channels and media ð copper wires, coaxial cables, fiber optic cables, satellites, . . . § Computers ð host computers, front-end computers, network servers, . . . § Telecommunications control software ð telecommunication monitors, network operating systems, . . . Middleware

Interactive usage : - increases considerably the productivity - requires communication networks Required transmission capacity depends on the application and on the user interface : - administrative input <1000 char/sec - CAD/CAM millions char/sec § § Physical location often crucial factor to decide on the type of connection between the computer and the workstation Standardization is an absolute must in this respect

Telecommunication Components O’Brien 126 5 components Telecom Channels and Media Telecom processors End-user workstation Telecom processors Telecommunications software Computers

LAN PC-workstation O’Brien 127 - 128 PC-workstation Databases and Software packages Shared hard disk Network Server Shared printer PC-workstation Port to other networks

WAN - Internetwork LAN’s Mainframe, hosts network in US network in Europe LAN’s Tymnet Internet network in Australia Cisco corporation network

Client/server network Company A Internet Router Intranet Firewall Router Company B text: O’Brien p 178 Intranet Mainframe host system

Client - Server Clients DB. server Print server CAD server comm. server Clients DB. server O. A. server comm. server

The Internetwork-enterprise The Internet Intranets Extranets Enterprise Intranets Supplier Client Intranets Electronic Commerce Other Organizations text: O’Brien p 180

Media and Channels § Signals Medium Metal wire Microwave Fiber optics ð analog ð digital § Cables ð Twisted-pair ð Coaxial cable Transmission speed. 0012 Mbps - 10 Mbps. 256 Mbps - 100 Mbps. 5 Mbps - 1, 000 Mbps interference 20 x more expensive 5. 500 simultaneous phone calls ð Fiber-optic 1 fiber 30. 000 phone calls § Wireless ð microwave ð satellites § § Radio, Infrared, Cellular Radio, Mobile computing GPS global positioning system text: O’Brien p 183 - 186

Communication hardware § § Modems 9. 600 14. 400 28. 800 bps Transmission mode ðSimplex ðHalf-duplex ð Full duplex § 1 circuit , 1 direction 1 circuit, 2 directions, difficult co-ordination 2 circuits, 2 directions Transmission accurateness ð parity bits forward and backward error correction § Processors ð multiplexers frequency, time or statistic time distribution ð front-end processors to handle routine communication tasks with peripheral equipment text: O’Brien p 187 - 189

Network Topology § Star ðall communications go via the central system § Bus ðcan easily be extended at the ends § Ring ðmore secure

Star network O’Brien 147 - 148 With direct connections Point-to-point lines - Efficient , also for high speeds - With a large number of workstations cabling might be a problem

Star network (multiplexed) Access via multiplexed lines eventually rented - local speed up to 2000 char/sec , 1 M char/sec very expensive - internationally 1000 char/sec commonly available

Bus network Shared usage of a broadband network Multidrop lines - more complex hardware - simpler cabling system O’Brien 191

Ring Networks Ring Network - more equal basis O’Brien 147

Public data networks PAD = Packet Assembler and Disassembler Data Network PAD E. g. . : DCS 1000 - 6000 char/sec , cost / volume data ( X 25 ) Due to high connection cost ($ 30. 000 year) usage of PAD

ISDN Integrated services Digital network ISDN - universal network for telephone and data - > 6000 char/sec

Open systems Definition: An open system is a system where the design has not been made by a supplier but by an accredited standardization organization (eg: ISO , IEEE , ANSI , CODASYL , . . . ) § § This provides the user a better independence from a specific hardware or software supplier and therefore a better guarantee for his investments. It allows the user to make always the most appropriate and optimal choice for each of the sub-systems. Open systems are not yet sufficiently available on the market. The best examples are UNIX and the OSI network model

The OSI model Defined by ISO ( International Standard Organization ). OSI ( Open System Interconnect ) describes a framework to subdivide connection problems in networks into almost independent sub-problems. e. g. : president x diplomatic rules president y interpreter x common language interpreter y cryptography common key cryptography operator common channel operator physical link

The TCP/IP and the 7 layer OSI model TCP/IP OSI Application layer Application- or process layer Presentation layer Session layer Host-to-host transport layer Internet-protocol IP network-interface Physical layer O’Brien 193 Transport layer Network layer data link Physical layer Communication services for end users Correct formatting and coding Support for session initiation Data transfers between nodes routing of connections Support for error-free data transfer physical access to communication media

OSI 7 -Layer Model O’Brien 150 7. Application (user application program) 6. Presentation (user interface / screen display ) 5. Session ( exchange between two nodes on the network ) 4. Transport ( protocol for encoding messages ) 3. Network ( mechanism for separating multiple messages ) 2. Link ( data encoding schemes ) 1. Physical ( wires, connectors , voltage )