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. Yuchung Cheng (8): tcp: support DUPACK threshold in RACK tcp: disable RFC6675 loss detection tcp: simpler NewReno implementation tcp: account lost retransmit after timeout tcp: new helper tcp_timeout_mark_lost tcp: separate loss marking and state update on RTO tcp: new helper tcp_rack_skb_timeout tcp: don't mark recently sent packets lost on RTO Documentation/networking/ip-sysctl.txt | 4 +- include/net/tcp.h | 5 ++ net/ipv4/tcp_input.c | 99 ++++++++++++++------------ net/ipv4/tcp_recovery.c | 80 ++++++++++++++++----- 4 files changed, 124 insertions(+), 64 deletions(-) -- 2.17.0.441.gb46fe60e1d-goog
