Cheatsheet: Difference between revisions
→TCP Topics Hierarchy
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*Congestion Control
- 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
- Congestion Avoidance - Additive Increase▼
- Congestion Detection - Multiplicative Decrease▼
- Increases the cwnd Additively, When a “window” is Ack cwnd is increased by 1, Window = No of segments transmitted during RTT
- The increase is based on RTT, not on the number of arrived ACKs, Congestion window increases additively until congestion is detected
- If congestion occurs, Window size must be decreased, Sender knows about congestion via RTO or 3 Dup Acks received, Size of Threshold is dropped to half
*Tahoe
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- '''Clark’s Solution''': Announce window size 0 till 1) enough space for 1 MSS in Buffer or Half Receive buffer is empty
- '''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
= VPN Messages =
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