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 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 Introduction

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, , 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