Link Layer - Slides (R3)

Link Layer Slides - CSCI 232 CSCI 232 Computer Networking Link Layer George Blankenship Blankenship Link Layer George Blankenship 1 Lesson Outline

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SCI 232 CSCI 232 Computer Networking: Link Layer eorge Blankenship George Blankenship Link Layer George Blankenship 1
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Lesson Outline oncepts Concepts – Protocol properties – Flow control – Error control • Non-shared media – General principles – HDLC • Shared Media eneral principles – General principles –W i r e d LAN • 802.3 and 802.5 ireless LAN – Wireless LAN • 802.11 and 802.15 – Wide area access l Link Layer George Blankenship 2 • Frame relay
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Protocol perspective oncepts • Virtual connection is from link layer to link yer •Concepts –Protocol low layer – link layer hides physical layer from service questors (network layer) –Flow –Error ontrol requestors (network layer) – encodes messages for peer link layer –Control •Non-shared hared • Actual connection is from physical layer to physical layer •Shared – service request to physical layer sends message Link Layer George Blankenship 3
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Message Movement oncepts System 1 Layer 7 System 2 Layer 7 •Concepts –Protocol low Layer 6 Layer 5 Layer 6 Layer 5 –Flow –Error ontrol Layer 4 Layer 3 Layer 4 ayer 3 –Control •Non-shared hared Layer 2 Service Interface Layer 3 ayer 2 Service Interface irtual Interface •Shared aye ayer 1 Real Interface Layer 2 ayer 1 Real Interface Real Interface V tua te ace Link Layer George Blankenship 4 Layer 1 Layer 1
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Basic Properties oncepts • Flow Control •Concepts –Protocol low – Pace the flow to the speed of the receiver –Flow –Error ontrol – Maximize the media utilization • Error Detection –Control •Non-shared hared – Recognize traffic with errors rror Control •Shared Error Control – Recover from traffic with errors Link Layer George Blankenship 5
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Flow Control essage can only be sent with oncepts • Message can only be sent with permission •Concepts –Protocol low – receiver issues permission when able to receive –Flow –Error ontrol – sender must hold message until permitted • Unbuffered flow control –Control •Non-shared hared – send, then wait for permission •B uffered flow control •Shared Buffered flow control – receiver issues permission for n messages nder may send n then waits Link Layer George Blankenship 6 – sender may send n, then waits
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Probability of Error oncepts •P b (BER): probability that a bit will be ceived inverted •Concepts –Protocol low received inverted 1 : Probability that a PDU of size F will –Flow –Error ontrol not be received in error P 1 = (1-P b ) F (BER=10 -6 , P 1 =.999) –Control •Non-shared hared 2 : Probability that a PDU will be ceived with undetected error •Shared received with undetected error P 2 = 1-P 1 (P 2 =10 -3 , 1 of 1000) Link Layer George Blankenship 7
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Types of Error oncepts • An error occurs when a bit is altered between transmission and reception •Concepts –Protocol low • Single bit errors – One bit altered djacent bits not affected –Flow –Error ontrol Adjacent bits not affected – White noise • Burst errors –Control
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This note was uploaded on 09/03/2010 for the course CS 232 taught by Professor Susan during the Summer '09 term at GWU.

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Link Layer Slides - CSCI 232 CSCI 232 Computer Networking Link Layer George Blankenship Blankenship Link Layer George Blankenship 1 Lesson Outline

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