Author: rscheff Date: Fri Oct 9 09:33:45 2020 New Revision: 366564 URL: https://svnweb.freebsd.org/changeset/base/366564
Log: MFC r366149: TCP newreno: improve after_idle ssthresh Adjust ssthresh in after_idle to the maximum of the prior ssthresh, or 3/4 of the prior cwnd. See RFC2861 section 2 for an in depth explanation for the rationale around this. As newreno is the default "fall-through" reaction, most tcp variants will benefit from this. Reviewed by: tuexen MFC after: 2 weeks Sponsored by: NetApp, Inc. Differential Revision: https://reviews.freebsd.org/D22438 Modified: stable/12/sys/netinet/cc/cc_newreno.c Directory Properties: stable/12/ (props changed) Modified: stable/12/sys/netinet/cc/cc_newreno.c ============================================================================== --- stable/12/sys/netinet/cc/cc_newreno.c Fri Oct 9 05:28:32 2020 (r366563) +++ stable/12/sys/netinet/cc/cc_newreno.c Fri Oct 9 09:33:45 2020 (r366564) @@ -213,12 +213,19 @@ newreno_after_idle(struct cc_var *ccv) * wirespeed, overloading router and switch buffers along the way. * * See RFC5681 Section 4.1. "Restarting Idle Connections". + * + * In addition, per RFC2861 Section 2, the ssthresh is set to the + * maximum of the former ssthresh or 3/4 of the old cwnd, to + * not exit slow-start prematurely. */ if (V_tcp_do_rfc3390) rw = min(4 * CCV(ccv, t_maxseg), max(2 * CCV(ccv, t_maxseg), 4380)); else rw = CCV(ccv, t_maxseg) * 2; + + CCV(ccv, snd_ssthresh) = max(CCV(ccv, snd_ssthresh), + CCV(ccv, snd_cwnd)-(CCV(ccv, snd_cwnd)>>2)); CCV(ccv, snd_cwnd) = min(rw, CCV(ccv, snd_cwnd)); } _______________________________________________ svn-src-all@freebsd.org mailing list https://lists.freebsd.org/mailman/listinfo/svn-src-all To unsubscribe, send any mail to "svn-src-all-unsubscr...@freebsd.org"
