Chapter 6

1. Chapter 6 Telecommunications and Networks

2. Learning Objectives • Understand the concept of a network. • Apply Metcalfe’s law in understanding the value of a network. • Identify several major developments and trends in the industries, technologies, and business applications of telecommunications and Internet technologies. • Provide examples of the business value of Internet, intranet, and extranet applications.

3. Learning Objectives • Identify the basic components, functions, and types of telecommunications networks used in business. • Explain the functions of major components of telecommunications network hardware, software, media, and services. • Explain the concept of client/server networking. • Understand the two forms of peer-to-peer networking. • Explain the difference between digital and analog signals.

4. Learning Objectives • Identify the various transmission media and topologies used in telecommunications networks. • Understand the fundamentals of wireless network technologies. • Explain the concepts behind TCP/IP. • Understand the seven layers of the OSI network model.

5. Network Concept • Network: A connected system of objects or people • Computer network: A collection of computers and other hardware devices connected together so users can share hardware, software, and data, and electronically communicate • Networks range from small private networks to the Internet (largest network in the world)

6. Network Concepts • Number of possible connections on a network is N * (N-1) • Where N = number of nodes (points of connections on the network) • Example, if there are 10 computers on a network, there are 10 * 9 = 90 possible connections

7. Bob Metcalfe’s Law • The usefulness (value) of a network equals the square of the number of users • If there are only 2 users on the network, it’s not very useful; if there are 200 it’s much more useful. • So the Internet with millions of computers is incredibly useful.

8. Telecommunications • Telecommunications • Exchange of information in any form (voice, data, text, images, audio, video) over networks

9. Telecommunications • When we communicate, we are sharing information. This sharing can be local or remote. • Local ( usually occurs face to face) or • remote ( take place over distance) • Data Communications • The movement of computer information from one point to another by means of electrical or optical transmission systems. • Such systems are often called data communications networks. • Telecommunication (which Includes telephony, telegraphy and television ) (teleis Greek for "far“) • means communication at a distance • Exchange of information in any form (voice, data, text, images, audio, video) over networks

10. Components of data communication • Message: data  text, number, audio … • Sender: device that sends the data – computer, telephone, camera • Receiver: device that receives the data – computer, telephone, camera • Transmission medium: physical path by which message travels. • Rules or Protocols: Set of rules that govern data communications/ an agreement between the communicating devices components of data communication

11. Simple model of communication

12. Simple model of Communication • The key elements of this model are: • Source • generates data to be transmitted • Transmitter • converts data into transmittable signals • Transmission System • carries data from source to destination • Receiver • converts received signal into data • Destination • takes incoming data

13. Open Systems • Information systems that use common standards for hardware, software, applications and networks • Open systems provide:- • Connectivity: • Ability of networked computers to easily access and communicate with each other and share information • Interoperability: • The ability of an open system to enable end user applications to be accomplished using different varieties of computer systems, software packages, and databases provided by a variety of interconnected networks

14. Middleware • Any programming that serves to “glue together” two separate programs Middleware Programming that mediates between two separate programs Allows a particular database to access other databases without custom programming

15. Data Transmission Characteristics There are two fundamentally different types of data: Digital data – Computer produced signals that are binary, either on or off. Digital data have discrete states and take discrete values. Analog – Electrical signals which are shaped like the sound waves they transfer. Analog data are continuous and take continuous values

16. Data Transmission Characteristics Signals: Electric representations of information. Can be Analog or Digital An analog signal refers to something that is continuous- a type of signal represented by continuous waves. Analog signals can have an infinite number of values in a range A digital signal refers to something that is discrete –a type of signal where data represented by 0s and 1s digital signals can have only a limited number of values. Transmission can also be Analog or Digital Analog transmission system: continuous signals Digital transmission system: discrete signals

17. encoder/decoder modulator/demodulator

18. Digital Network Technologies • Rapid change from analog to digital network technologies • Analog: voice-oriented transmission, sound waves • Digital: discrete pulse transmission • Digital allows: • Higher transmission speed • Larger amounts of information • Lower error rates • …

19. Internet2 • Next generation of the Internet • High-performance network • In use at 200 universities, scientific institutions, communications corporations • Internet2 may never replace the Internet. May remain a scientific and government network.

20. Business Value of Telecommunication Networks

21. The Internet • Over 46 million servers (2004) • 710 – 945 million users (2004) • No central computer system • No governing body • No one owns it

22. Internet Service Provider • ISP • A company that specializes in providing easy access to the Internet • For a monthly fee, you get software, user name, password and access • ISPs are connect to one another through network access points

23. Popular uses of the Internet

24. An Intranet • A network inside an organization • That uses Internet technologies (such as Web browsers and servers, TCP/IP protocols, HTML, etc.) • To provide an Internet-like environment within the organization • For information sharing, communications, collaboration and support of business processes • Can be accessed by authorized users through the Internet

25. Enterprise Information Portal Intranets provide an enterprise information portal.

26. Extranet • Network links that use Internet technologies • To connect the Intranet of a business With the Intranets of its customers, suppliers or other business partners • Intranet that is at least partially accessible to authorized outsiders

27. Wide Area Local Area Peer-to-Peer Virtual Private Client/Server Types of Communications Networks Communication Networks

28. Wide Area Network (WAN) • Telecommunications network that covers a large geographic area Source: Courtesy of Cisco Systems Inc.

29. Local Area Network (LAN) • Connect computers within a limited physical area such as an office, classroom, or building

30. Virtual Private Networks (VPN) • A secure network that uses the Internet as its backbone but relies on firewalls, encryption and other security • A pipe traveling through the Internet

31. VPN

32. Client/Server networks • Clients: End user personal computers or networked computers • Interconnected by LANs • Servers: manage networks • Processing shared between clients and servers

33. Network Computing • Thin client means that very little processing is done on the client. Most the processing is done on the server. • Three-tier model includes thin clients, application servers and database servers • Two tiered client server includes just client and server

34. Peer-to-Peer Networks Central Server Architecture P2P file-sharing software connects all PCsto a central server that contains a directory of all online users The server sends the requesting PC a list oflinks to all active peers who have the file Clicking a link connects the two PCs andautomatically transfers the file to the requesting PC

35. Peer-to-Peer Networks Pure Peer-to-Peer Architecture No central directory or server File-sharing software connectsone PC to another online user When you request a file, the softwaresearches every online user, then sendsyou a list of active file names Clicking a link automatically transfers the filefrom that user’s hard drive to yours

36. Peer-to-Peer Network Diagrams

37. Telecommunications Media Source: Phil Degginger/Getty Images.

38. Wireless Technologies • microwave • Earthbound microwave systems that transmit high-speed radio signals in a line-of-sight path • Between relay systems spaced approximately 30-miles apart • Communications satellites • Satellite serves as relay stations for communications signals • Uses microwave radio signals

39. Wireless Technologies • Cellular and PCS telephone and pager systems • Divide the geographic area into small areas or cells • Each cell has transmitter or radio relay antenna to send message from one cell to another • Wireless LANs • Radio signals within an office or building • Connect PCs to networks • Bluetooth • Short-range wireless technology • To connect PC to peripherals such as printer

40. Wireless Web • Connect portable communications devices to the Internet

41. Telecommunications Processors • Modems • Convert digital signals from a computer into • Analog frequencies that can be transmitted over ordinary telephone lines

42. Comparing modem and other technologies

43. Internetwork Processors • Switch – makes connections between telecommunications circuits in a network • Router – intelligent communications processor that interconnects networks based on different protocols • Hub – a port switching communications processor • Gateway – connects networks using different communications architectures

44. Telecommunications Processors • Multiplexer… allows a single communications channel to carry simultaneous data transmissions from many terminals

45. Telecommunications Software • Used by servers and other computers to manage network performance • Network Operating Systems • Middleware

46. Network management functions • Traffic Management – manage network resources and traffic to avoid congestion and optimize service levels to users • Security – provide authentication, encryption, firewall, auditing and enforcement • Network Monitoring – troubleshoot and watch over the network, informing network administrators of potential problems before they occur • Capacity Planning – survey network resources and traffic patterns and users’ needs to determine how best to accommodate the needs of the network as it grows and changes

47. Network Topologies Topology: structure of a network Star: ties end user computers to a central computer Ring: ties local computer processors together in a ring on a relatively equal basis Bus: local processors share the same communications channel

48. Network Topologies

49. OSI & TCP/IP Models • Open Systems Interconnection (OSI) Model • A seven-layer model that serves as a standard model for network architectures • Model for how messages should be transmitted between two points in a network • Each layer adds functions • Transmission Control Protocol / Internet Protocol (TCP/IP) • A five layer telecommunications protocol used by the Internet

50. OSI & TCP/IP Models