Transport Layer - Freie Universität Berlin
Transport Layer - Freie Universität Berlin
Transport Layer - Freie Universität Berlin
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Fast Retransmit and Fast Recovery<br />
● Fast Retransmit has to be enhanced to be useful in overload situations…<br />
● Fast Recovery<br />
● When the third ACK is received, reduce<br />
● Retransmit the missing segment, set<br />
ssthresh = max(ssthresh/2, 2×MSS)<br />
cwnd = ssthresh + 3*MSS<br />
● For each more duplicated ACK, increment cwnd by MSS<br />
● This reduces cwnd by the amount of lost segments to adapt to the network<br />
situation<br />
● If the new cwnd (and the receiver’s buffer) allows, send a segment<br />
● When the next (normal) ACK arrives, set cwnd to ssthresh to go on normally<br />
Univ.-Prof. Dr.-Ing. Jochen H. Schiller ▪ cst.mi.fu-berlin.de ▪ Telematics ▪ Chapter 8: <strong>Transport</strong> <strong>Layer</strong><br />
8.105
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