RFC 4960 Errata 3.27 identifies that ssthresh should be adjusted to cwnd because otherwise it could cause the transport to lock into congestion avoidance phase specially if ssthresh was previously reduced by some packet drop, leading to poor performance.
The Errata says to adjust ssthresh to cwnd only once, though the same goal is achieved by updating it every time we update cwnd too. The caveat is that we could take longer to get back up to speed but that should be compensated by the fact that we don't adjust on RTO basis (as RFC says) but based on Heartbeats, which are usually way longer. See-also: https://tools.ietf.org/html/draft-ietf-tsvwg-rfc4960-errata-01#section-3.27 Signed-off-by: Marcelo Ricardo Leitner <marcelo.leit...@gmail.com> --- net/sctp/transport.c | 2 ++ 1 file changed, 2 insertions(+) diff --git a/net/sctp/transport.c b/net/sctp/transport.c index e3ebf04ddbd092a1ba04962c8fbe85a58588771a..7cdd6bcddbc5ad277f525635cf56788f70a4ee30 100644 --- a/net/sctp/transport.c +++ b/net/sctp/transport.c @@ -569,6 +569,8 @@ void sctp_transport_lower_cwnd(struct sctp_transport *transport, */ transport->cwnd = max(transport->cwnd/2, 4*asoc->pathmtu); + /* RFC 4960 Errata 3.27.2: also adjust sshthresh */ + transport->ssthresh = transport->cwnd; break; } -- 2.9.4
