Cheatsheet: Difference between revisions
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[[File:Mtu mss.png|center]]
* '''RTO:''' Four ACKs acknowledging the same packet, which are not piggybacked on data and do not change the receiver's advertised window.▼
*Fast Retransmission▼
- If RTO has a larger value▼
- If sender receives four acknowledgments with same value (three duplicates)▼
- Segment expected by all of these Ack is resent immediately▼
*Fast Recovery:
-
*Congestion Control
;Slow Start - Exponential Increase
- Sender starts with cwnd = 1 MSS, Size increases 1 MSS each time one Ack arrives, Increases the rate exponentially(1,2,4,8....) until a threshold is reached
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* Behavior of Tahoe and Reno differ primarily in how they react to duplicate ACKs.
<center>
▲* Four ACKs acknowledging the same packet, which are not piggybacked on data and do not change the receiver's advertised window.
{| class="wikitable"
|-
! Event !! Tahoe !! Reno
|-
| 3 Dup Acks ||
|-
| RTO (Ack time out) || Slow start is used<br>Reduce congestion window to 1 MSS || Slow start is used<br>Reduce congestion window to 1 MSS
▲|-
|}
</center>
*Silly Window Syndrome: Sender creates data slowly or Receiver consumes slowly or both.
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- '''Delayed Acknowledgment''': Segment not acknowledged immediately, Sender TCP does not slide its window, reduces traffic, sender may unnecessarily retransmit, Not delay more than 500 ms.
▲*Fast Retransmission
▲ - If RTO has a larger value
▲ - If sender receives four acknowledgments with same value (three duplicates)
▲ - Segment expected by all of these Ack is resent immediately
*Persistence Timer
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