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Chapter 7 Local Area Networks : The Basics

2. Last time. Types of errors and their preventionError detectionParity

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Chapter 7 Local Area Networks : The Basics

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    1. 1 Chapter 7 Local Area Networks : The Basics

    2. 2 Last time Types of errors and their prevention Error detection Parity 50% CRC can detect nearly all errors Error correction 1. Do nothing 2. Return an error message to the transmitter 3. Fix the error with no further help from the transmitter

    3. 3 Three Major Types of Networks Local Area Network (LAN) Serves users within a confined geographical area (usually within a mile). Metropolitan Area Network (MAN) Covers a geographic area the size of a city or suburb. The purpose of a MAN is often to bypass local telephone companies when accessing long-distance service. Wide Area Network (WAN) Covers a wide geographical area, such as a state or a country. Examples: Tyment, Telenet, Uninet, and Accunet.

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    16. 16 LAN Topologies: Bus Consists of a single wire to which individual stations are attached Each end has a terminator attached to it Data travels the entire length of the cable Transmission from any stations travels entire medium (both directions) Inexpensive and easy to install Ethernet is the common form of a bus topology system

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    47. 47 Summary of topologies Logical vs physical topologies Bus and star-rings - old technologies Still some around Youll probably use Star-wired bus (star) With bus or routers (now much easier to use) Wireless network (Wi-fi)

    48. 48 Protocols Last time topologies Now how the data actually flows

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    55. 55 Collisions Busy CSMA/CD networks can waste over half their time dealing with collisions.

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    57. 57 Token Passing Protocols Before workstation can transmit it must possess the one and only token Two types: Token ring Token bus

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    62. 62 Problems with the OSI model for LANs Problems with broadcast networks! Routing (no decisions have to be made) Data link and physical link tightly coupled Need to specify hardware! Ugh! Broadcast networks need to be have a medium access control to decide who talks

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    74. 74 Ethernet Standards Key XXXBase or XXX Broad XXX 10 means 10Mbps

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    85. 85 What we covered Topologies Star-bus Wireless Protocols CSMA/CD Systems Ethernet Next time: wireless networks?

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