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Yuchung Cheng says: ==================== tcp: default RACK loss recovery This patch set implements the features correspond to the draft-ietf-tcpm-rack-03 version of the RACK draft. https://datatracker.ietf.org/meeting/101/materials/slides-101-tcpm-update-on-tcp-rack-00 1. SACK: implement equivalent DUPACK threshold heuristic in RACK to replace existing RFC6675 recovery (tcp_mark_head_lost). 2. Non-SACK: simplify RFC6582 NewReno implementation 3. RTO: apply RACK's time-based approach to avoid spuriouly marking very recently sent packets lost. 4. with (1)(2)(3), make RACK the exclusive fast recovery mechanism to mark losses based on time on S/ACK. Tail loss probe and F-RTO remain enabled by default as complementary mechanisms to send probes in CA_Open and CA_Loss states. The probes would solicit S/ACKs to trigger RACK time-based loss detection. All Google web and internal servers have been running RACK-only mode (4) for a while now. a/b experiments indicate RACK/TLP on average reduces recovery latency by 10% compared to RFC6675. RFC6675 is default-off now but can be enabled by disabling RACK (sysctl net.ipv4.tcp_recovery=0) for unseen issues. ==================== Signed-off-by: David S. Miller <davem@davemloft.net>
Linux kernel
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