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CS 635 Lecture 3, Part 3 Logical Link Control

(Note: Material for this page has been borrowed from

Error Control

Go-Back-N ARQ

Go-Back-N continued

Go Back N: Example


Selective Repeat ARQ

As in go back-N:

Unlike Go-Back-N


Selective Repeat ARQ: example:


How Big Can a Window Be?

Suppose sequence number space size is N

Fundamental problem: sender and receiver

Detecting Errors: checksums

Need to detect errors: bits in packet may be flipped while in transit or stored at intermediate notes.

Approach: add extra bits to packets that will aloow us to detect (possibly correct) bit errors

Simple example: parity

Forward Error Correction: FEC

ARQ protocols operate by detecting errors and retransmitting

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