Chapter One

1. Chapter One Introduction to Computer Networks and Data Communications

2. Introduction Chapter One - Introduction to Computer Networks And Data Communications • Who today has not used a computer network? • Mass transit, interstate highways, 24-hour bankers, grocery stores, cable television, cellphones, businesses and schools, and retail outlets support some form of computer network

3. The Language of Computer Networks Chapter One - Introduction to Computer Networks And Data Communications • Computer network – an interconnection of computers and computing equipment using either wires or radio waves over small or large geographic areas • Local area network – networks that are small in geographic size spanning a room, floor, building, or campus

4. The Language of Computer Networks Chapter One - Introduction to Computer Networks And Data Communications • Metropolitan area network – networks that serve an area of 1 to 30 miles, approximately the size of a typical city • Wide area network – a large network that encompasses parts of states, multiple states, countries, and the world

5. The Language of Computer Networks Chapter One - Introduction to Computer Networks And Data Communications • Personal area network – a network of a few meters, between wireless devices such as PDAs, laptops, and similar devices • Voice network – a network that transmits telephone signals • Data network – a network that transmits computer data

6. The Language of Computer Networks Chapter One - Introduction to Computer Networks And Data Communications • Data communications – the transfer of digital or analog data using digital or analog signals • Telecommunications – the study of telephones and the systems that transmit telephone signals • Network management – the design, installation, and support of a network, including its hardware and software

7. The Big Picture Chapter One - Introduction to Computer Networks And Data Communications • Networks are composed of many devices, including: • Workstations (computers, telephones) • Servers • Network hubs and switches (bridges) • Routers (LAN to WAN and WAN to WAN) • Telephone switching gear

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9. Computer Networks – Basic Connections Chapter One - Introduction to Computer Networks And Data Communications • Computer terminal / microcomputer to mainframe • Microcomputer to local area network • Microcomputer to Internet • Local area network to local area network • Personal area network to workstation

10. Computer Networks – Basic Connections Chapter One - Introduction to Computer Networks And Data Communications • 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

11. Basic Connections – Computer Terminal / Microcomputer to Mainframe Computer Chapter One - Introduction to Computer Networks And Data Communications • Predominant form in the 1960s and 1970s • Still used in many types of businesses for data entry and data retrieval • Usually involves a low-speed connection

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13. Basic Connections – Microcomputer to Local Area Network Chapter One - Introduction to Computer Networks And Data Communications • Highly common throughout business and academic environments, and now homes • Typically a medium- to high-speed connection • Computer (device) requires a NIC (network interface card) • NIC connects to a hub-like device

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15. Basic Connections – Microcomputer to Internet Chapter One - Introduction to Computer Networks And Data Communications • Popular with home users and small businesses • Often a dial-up modem is used to connect user’s microcomputer to an Internet service provider • Technologies such as DSL and cable modems are replacing modems

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17. Basic Connections – Local Area Network to Local Area Network Chapter One - Introduction to Computer Networks And Data Communications • Found in systems 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 • Switch can filter frames

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19. Basic Connections – Personal Area Network to Workstation Chapter One - Introduction to Computer Networks And Data Communications • Interconnects wireless devices such as PDAs, laptops and notebooks, and music playback devices • Used over short distances such as a few meters

20. Chapter One - Introduction to Computer Networks And Data Communications

21. Basic Connections – Local Area Network to Metropolitan Area Network Chapter One - Introduction to Computer Networks And Data Communications • Used to interconnect companies (usually their local area networks) to networks that encompass a city • High-speed networks with redundant circuits • Metro Ethernet is latest form of metropolitan LAN

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23. Basic Connections – Local Area Network to Wide Area Network Chapter One - Introduction to Computer Networks And Data Communications • One of the most common ways to interconnect a user on a LAN workstation to the Internet (a wide area network) • A router is the typical device that performs LAN to WAN connections • Routers are more complex devices than switches

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25. Basic Connections – Wide Area Network to Wide Area Network Chapter One - Introduction to Computer Networks And Data Communications • 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

26. Basic Connections – Sensor to Local Area Network Chapter One - Introduction to Computer Networks And Data Communications • 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

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28. Basic Connections – Satellite and Microwave Chapter One - Introduction to Computer Networks And Data Communications • Typically 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 • Newer shorter-distance services such as Wi-Max

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30. Basic Connections – Wireless or Cellular Telephones Chapter One - Introduction to Computer Networks And Data Communications • Constantly expanding market across the U.S. and world • Third generation services available in many areas and under many types of plans • Newest generation includes higher speed data transfers (100s of kilobits per second)

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32. An Additional Basic Connection – Telephone to Network Chapter One - Introduction to Computer Networks And Data Communications • Telephone systems are ubiquitous and now carry more data than voice • Common configuration – telephone connected to POTS • Newer configuration (VoIP) – telephone to LAN via gateway or telephone to gateway via DSL/cable

33. Network Architectures Chapter One - Introduction to Computer Networks And Data Communications • A 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 likelihood that different components from different manufacturers will converse • Two models to learn: OSI model and TCP/IP protocol suite

34. Network Architectures Chapter One - Introduction to Computer Networks And Data Communications • The OSI model’s seven layers:

35. Network Architectures - OSI Chapter One - Introduction to Computer Networks And Data Communications • Application layer – where the application using the network resides. Common network applications include web browsing, e-mail, file transfers, and remote logins • Presentation layer – performs a series of miscellaneous functions necessary for presenting the data package properly to the sender or receiver

36. Network Architectures - OSI Chapter One - Introduction to Computer Networks And Data Communications • Session layer – responsible for establishing sessions between users • Transport layer – provides an end-to-end error-free network connection. Makes sure the data arrives at the 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.

37. Network Architectures - OSI Chapter One - Introduction to Computer Networks And Data Communications • Data link layer – responsible for taking the data and transforming it into a frame with header, control and address information, and error detection code • Physical layer – handles the transmission of bits over a communications channel. Includes voltage levels, connectors, media choice, modulation techniques

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39. Network Architectures Chapter One - Introduction to Computer Networks And Data Communications • The TCP/IP protocol suite (DoD protocol suite, Internet model):

40. Network Architectures – TCP/IP Chapter One - Introduction to Computer Networks And Data Communications • Application layer – equivalent to OSI’s application and presentation layers • Transport layer – equivalent to OSI’s transport layer • Network (Internet or internetwork) layer – equivalent to OSI’s network layer • Network access (data link/physical) layer – equivalent to OSI’s data link and physical layers

41. Network Architectures Chapter One - Introduction to Computer Networks And Data Communications • Logical and physical connections – A logical connection is one that exists only in the software, while a physical connection is one that exists in the hardware • Note that in a network architecture, only the lowest layer contains the physical connection, while are higher layers contain logical connections

42. Chapter One - Introduction to Computer Networks And Data Communications Logical and physical connections

43. Chapter One - Introduction to Computer Networks And Data Communications Example of data flow through layers

44. Chapter One - Introduction to Computer Networks And Data Communications Network connections in action

45. The TCP/IP protocol suite in action Chapter One - Introduction to Computer Networks And Data Communications • Note the flow of data from user to web browser and back • At each layer, information is either added or removed, depending on whether the data is leaving or arriving at a workstation • The adding of information over pre-existing information is termed encapsulation

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