Chapter 1: Introduction to Computer Networks and Data Communications

1. Chapter 1: Introduction to Computer Networks and Data Communications

2. Objectives After reading this chapter, you should be able to: • Define the basic terminology of computer networks • Recognize the individual components of the big picture of computer networks • Outline the basic network configurations • Cite the reasons for using a network model and explain how they apply to current network systems

3. Objectives (continued) • List the layers of the OSI model and describe the duties of each layer • List the layers of the TCP/IP protocol suite and describe the duties of each layer • Compare the OSI model and TCP/IP protocol suite and list their differences and similarities

4. Introduction • Who today has not used a computer network? • Mass transit, interstate highways, 24-hour bankers, grocery stores, cable television, cellular telephones, most businesses and schools, and other retail outlets can support some form of computer networks

5. The Language of Computer Networks • Computer network - an interconnection of computers and computing equipment using either wires or radio waves over small or large geographic distances • Local area network - networks that are small in geographic size spanning a room, building, or campus • Metropolitan area network - networks that serve an area of 3 to 30 miles - approximately the area of a typical city

6. The Language of Computer Networks • Wide area network - a large network that encompasses parts of states, multiple states, countries, and the world • Data communications - the transfer of digital or analog data using digital or analog signals • Voice network - a network that transmits telephone signals • Data network - a network that transmits computer data

7. The Language of Computer Networks (continued) • Telecommunications - the study of telephones and the systems that transmit telephone signals • Network management - the design, installation, and support of a network and its hardware and software • Personal area network – a network of a few meters, between wireless devices such as PDAs, laptops, and similar devices

8. The Big Picture of Networks • Networks are composed of many devices, including: • Workstations (computers and telephones) • Servers • Network hubs and switches (bridges) • Routers (LAN-WAN and WAN-WAN) • Telephone switching gear

9. The Big Picture of Networks (continued)

10. Computer Networks - Basic Configurations • Computer terminal/microcomputer to mainframe computer • Microcomputer to local area network • Microcomputer to Internet • Local area network to local area network • Personal area network to workstation

11. Computer Networks – Basic Configurations (continued) • Local area network to metropolitan area network • Local area network to wide area network • Sensor to local area network • Satellite and microwave • Wireless telephone and wired telephone to network

12. Terminal/microcomputer-to-mainframe Computer Configurations • Predominant form in 60s and 70s • Still used in many types of businesses for data entry and data retrieval • Usually involves a low-speed connection

13. Terminal/microcomputer-to- mainframe Computer Configurations (continued)

14. Microcomputer-to-Local Area Network • Highly common throughout business and academic environments, and now even homes • Typically a medium- to high-speed connection • Microcomputer requires a NIC (network interface card) • NIC connects to a hub-like device

15. Microcomputer-to-local Network Configurations (continued)

16. Microcomputer-to-Internet Configurations • Very popular with home users and some small businesses • Typically, a dial-up modem is used to connect user’s microcomputer to an Internet service provider • Newer technologies such as DSL and cable modems are replacing modems

17. Microcomputer-to-Internet Configurations (continued)

18. Local Area Network-to-Local Area Network Configurations (continued) • Found in businesses and schools that have two or more LANs and a need for them to intercommunicate • A bridge-like device (such as a switch) is typically used to interconnect LANs • Bridge-like device can filter frames

19. Local Area Network-to-Local Area Network Configurations (continued)

20. Personal Area Network-to-Workstation Configurations • Interconnects wireless devices such as PDAs, laptops, and music playback devices • Used over a short distance such as a few meters

21. Personal Area Network-to-Workstation Configurations (continued)

22. Local Area Network-to-Metropolitan Area Network Configurations • Used to interconnect companies (usually their local area networks) to networks that encompass a metropolitan city • High speed networks with redundant circuits

23. Local Area Network-to-Metropolitan Area Network Configurations (continued)

24. Local Area Network-to-Wide Area Network Configurations • One of the most common ways to interconnect a user on a LAN workstation to the Internet (a wide area network) • Router • Typical device that performs LAN to WAN connections • More complex devices than bridges/switches

25. Local Area Network-to-Wide Area Network Configurations (continued)

26. Wide Area Network-to-Wide Area Network Network Configurations • High-speed routers and switches are used to connect one wide area network to another • Thousands of wide area networks across North America • Many interconnected via these routers and switches

27. Sensor-to-Local Area Network Configurations • Not all local area networks deal with microcomputer workstations • Often found in industrial and laboratory environments • Assembly lines and robotic controls depend heavily on sensor-based local area networks

28. Sensor-to-Local Area Network Configurations (continued)

29. Satellite and Microwave Configurations • Long distance wireless connections • Many types of applications including long distance telephone, television, radio, long-haul data transfers, and wireless data services • Typically expensive services but many companies offer competitive services and rates

30. Satellite and Microwave Configurations (continued)

31. Wireless Telephone Configurations • Constantly expanding market across the U.S. and world • Second generation PCS services available in most areas and under many types of plans • Next generation services beginning to replace PCS phones

32. Wireless Telephone Configurations (continued)

33. Wireless Telephone Configurations (continued) • An additional basic configuration is telephone to network • Telephone systems are ubiquitous and can now carry more data than voice • Common configuration – telephone connected to POTS • Newer configuration – telephone to LAN via gateway (VoIP)

34. Network Architectures • Reference model that describes the layers of hardware and software necessary to transmit data between two points or for multiple devices / applications to interoperate • Reference models are necessary to increase the likelihood that different components from different manufacturers will converse • Two architectures are required learning: The OSI Model, and the TCP/IP protocol suite

35. The Open Systems Interconnection (OSI) model

36. The Open Systems Interconnection (OSI) model (continued) • Application layer - where the application using the network resides • Common network applications include remote login, file transfer, e-mail, and web page browsing • Presentation layer - performs series of miscellaneous functions necessary for presenting the data package properly to the sender or receiver

37. The Open Systems Interconnection (OSI) model (continued) • Session layer - responsible for establishing sessions between users • Transport layer - provides end-to-end error-free network connection • Makes sure data arrives at destination exactly as it left the source • Network layer - responsible for creating, maintaining and ending network connections • Transfers a data packet from node to node within the network

38. The Open Systems Interconnection (OSI) model (continued) • Data link layer - responsible for taking data and transforming it into a frame with header, control and address information, as well as error detection code • Physical layer - handles the transmission of bits over a communications channel • Includes voltage levels, connectors, media choice, modulation techniques

39. The Open Systems Interconnection (OSI) model (continued)

40. The TCP/IP Protocol Suite

41. The TCP/IP Protocol Suite (continued) • Application layer - equivalent to the OSI’s presentation and application layers • Transport layer - performs same function as OSI transport layer • Network (Internet or internetwork) layer - roughly equivalent to the OSI’s network layer • Network access (data link/physical) layer - equivalent to the OSI’s physical and data link layers

42. Logical and Physical Connections • Logical connection – exists only in the software • Physical connection – exists in the hardware • In a network architecture • Only lowest layer contains physical connection • All higher layers contain logical connections

43. Logical and Physical Connections (continued)

44. Logical and Physical Connections (continued)

45. Network Configurations in Action

46. The TCP/IP Protocol Suite in Action • Note the flow of data from user to web browser and back • At each layer, information is either added or removed • Depends on whether data is leaving or arriving at a workstation • Encapsulation - adding information over pre-existing information

47. The TCP/IP Protocol Suite in Action (continued)

48. Summary • Basic terminology of computer networks • Individual components of computer networks • Basic network configurations • Network models and how they apply to current network systems • Layers of the OSI model and the TCP/IP protocol suite