Flow and Error Control - Data Communication - Lecture Slides, Slides of Data Communication Systems and Computer Networks

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DATA

COMMUNICATION

Lecture-

Recap of Lecture 37

 Line Discipline

• ENQ/ACK
• POLL/SELECT

 Flow Control

Flow Control

 A set of procedures used to restrict the amount of data the sender can send before waiting for acknowledgment

 Each receiving device has a buffer

Flow Control

Stop-and-Wait

Sliding Window

 Sliding window is an imaginary box

• At both sender and the receiver
• Frames are numbered modulo-n, window size is n-
• An ACK includes the number of next frame it expects

Sender Window

 Sliding window of the sender

• Shrink from the left when frames are sent
• Expands to the right when ACKs are received

Sender Window

Receiver Window

Error Control

Stop-and-Wait ARQ:

Damaged Frame

Stop-and-Wait ARQ:

Lost ACK

Summary

 Flow Control

-Stop-and-Wait- -Sliding Window

 Error Control