anchao opened a new pull request #2414: URL: https://github.com/apache/incubator-nuttx/pull/2414
## Summary net/tcp: implement the fast retransmit https://tools.ietf.org/html/rfc2001#section-3 ``` RFC2001: TCP Slow Start, Congestion Avoidance, Fast Retransmit, and Fast Recovery Algorithms ... 3. Fast Retransmit Modifications to the congestion avoidance algorithm were proposed in 1990 [3]. Before describing the change, realize that TCP may generate an immediate acknowledgment (a duplicate ACK) when an out- of-order segment is received (Section 4.2.2.21 of [1], with a note that one reason for doing so was for the experimental fast- retransmit algorithm). This duplicate ACK should not be delayed. The purpose of this duplicate ACK is to let the other end know that a segment was received out of order, and to tell it what sequence number is expected. Since TCP does not know whether a duplicate ACK is caused by a lost segment or just a reordering of segments, it waits for a small number of duplicate ACKs to be received. It is assumed that if there is just a reordering of the segments, there will be only one or two duplicate ACKs before the reordered segment is processed, which will then generate a new ACK. If three or more duplicate ACKs are received in a row, it is a strong indication that a segment has been lost. TCP then performs a retransmission of what appears to be the missing segment, without waiting for a retransmission timer to expire. ``` Change-Id: Ie2cbcecab507c3d831f74390a6a85e0c5c8e0652 Signed-off-by: chao.an <anc...@xiaomi.com> ## Impact TCP retransmit ## Testing iperf test ---------------------------------------------------------------- This is an automated message from the Apache Git Service. To respond to the message, please log on to GitHub and use the URL above to go to the specific comment. For queries about this service, please contact Infrastructure at: us...@infra.apache.org
