Upon seeing #6 arrive, though, it would stop sending the duplicate acknowledgements. As above, if the receiver sees (for example) a segment with sequence #5 followed by another with #7 before seeing sequence #6 then it might try to begin to trigger a fast retransmit. But since it did acknowlege the SYN-ACK, it shouldnt need to retransmit the SYN. If the client hadnt already acknowledged the SYN-ACK, this would have been reported as a retransmission. It's also possible that the same symptom of gaps in sequence numbers might be seen in a situation where packets are being delivered out of order. TCP post number reused means that it saw a successful connection handshake, then the client sent another SYN packet with the same port numbers. This can occur without waiting for the acknowledgement timeout for the lost packet to hit on the transmitter - which, as the name implies, means recovering a lot faster. The repeated acknowledgements at the last known value before the gap signal which packets the sender should retransmit.
The use of TCP Fast Retransmission which is a mechanism by which a receiver can indicate that it has seen a gap in the received sequence numbers that implies the loss of one or more packets in transit. TCP Retransmission occurs when time out timer expires before receiving the acknowledgement or 3 duplicate acknowledgements are received from the receiver for the same segment. Tekrar gönderilen paketler için Wirehark bazen Retransmission bazen de Fast Retransmission metnini gösterir.Įğer alan taraf paket sırasında atlama olduğunu saptarsa TCP Duplicate Ack göndererek hangi paketi alamadığını belirtir. TCP Retransmission is a process of retransmitting a TCP segment. Tekrar gönderilen paketleri görmek için şöyle yaparız.
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