The document discusses error control in TCP networks. It describes tools like acknowledgements and timeouts that TCP uses to detect errors in transmitted data and request retransmissions. It also covers error detection techniques like cyclic redundancy checksums and different ARQ protocols including stop-and-wait, go-back-N, and selective repeat which use acknowledgements and negative acknowledgements to ensure reliable data transmission.

1. J.ARTHY,
Assistant Professor,
SRMIST,
Ramapuram

2. 1. Do nothing
2. Return an error message to the
transmitter
3. Fix the error with no further
help from the transmitter

3. TCP ERROR CONTROLS
 Noise
 signal will be lost or corrupted.
 check for transmission errors.
 perform some action.
 error be discarded.

5. TCP ERROR CONTROLS TOOLS
1.Acknowledgement (no negative ack)(Corruption)
2.Time-out (no ack by timeout implies corrupt or lost)
3.time-out (one time-out counter per segment)

6. Lost segment or corrupted segment
Duplicate segment
Out-of-order segment
Lost ACK

9.  Proper shielding
 Equalization
 New digital components
 Digital repeaters
 Analog amplifiers

10. Cyclic Redundancy Checksum
The message (with the remainder) receiver.
The receiver divides the message and remainder by the
same generating polynomial.
If a remainder not equal to zero  error
If a remainder of zero results no error

11. r is the degree of the generating polynomial

13. Error Control Steps
 Error detection
 Positive Acknowledgment (ACK)
 Retransmission
 Negative acknowledgment (NAK)

14. 1. Stop-and-wait ARQ
2. Go-back-N ARQ
3. Selective-repeat ARQ

15. Stop-and-wait ARQ
A transmitter sends a frame then stops and waits for an acknowledgment.
If a positive acknowledgment (ACK) is received, the next frame is sent.
If a negative acknowledgment (NAK) is received, the same frame is
transmitted again.

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SEECTIVE REPEAT ARQ