Date: Wed, 21 Aug 2002 13:40:25 -0700 (PDT) From: Oleg Polyakov <opolyakov@yahoo.com> To: freebsd-net@FreeBSD.org Subject: Re: Initial congestion window increase Message-ID: <20020821204025.33297.qmail@web10408.mail.yahoo.com> In-Reply-To: <0H1500FJLZIPYE@mta6.snfc21.pbi.net>
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--- Jeffrey Hsu <hsu@FreeBSD.org> wrote:
> Your copy of -current is a little out of date. I removed that hideous
> INET6 #ifdef last week.
Here is updated diff.
--- tcp_input.c.orig Mon Aug 19 19:47:11 2002
+++ tcp_input.c Wed Aug 21 11:12:24 2002
@@ -114,6 +114,10 @@
&tcp_delack_enabled, 0,
"Delay ACK to try and piggyback it onto a data packet");
+int inc_init_win = 0;
+SYSCTL_INT(_net_inet_tcp, OID_AUTO, increased_initial_window, CTLFLAG_RW,
+ &inc_init_win, 1, "Increased initial window");
+
#ifdef TCP_DROP_SYNFIN
static int drop_synfin = 0;
SYSCTL_INT(_net_inet_tcp, OID_AUTO, drop_synfin, CTLFLAG_RW,
@@ -2495,6 +2499,7 @@
* of the interface), as we can't discover anything about intervening
* gateways or networks. We also initialize the congestion/slow start
* window to be a single segment if the destination isn't local.
+ * We may increase the congestion/slow start window in accordance with
RFC2414.
* While looking at the routing entry, we also initialize other path-dependent
* parameters from pre-set or cached values in the routing entry.
*
@@ -2686,7 +2691,9 @@
if ((isipv6 && in6_localaddr(&inp->in6p_faddr)) ||
(!isipv6 && in_localaddr(inp->inp_faddr)))
tp->snd_cwnd = mss * ss_fltsz_local;
- else
+ else if (inc_init_win)
+ tp->snd_cwnd = min(4*mss, max(2*mss,4380));
+ else
tp->snd_cwnd = mss * ss_fltsz;
if (rt->rt_rmx.rmx_ssthresh) {
--- tcp_output.c.orig Sat Aug 17 18:26:01 2002
+++ tcp_output.c Wed Aug 21 11:12:24 2002
@@ -146,16 +146,22 @@
* Set the slow-start flight size depending on whether
* this is a local network or not.
*/
- int ss = ss_fltsz;
+ if (
#ifdef INET6
- if (isipv6) {
- if (in6_localaddr(&tp->t_inpcb->in6p_faddr))
- ss = ss_fltsz_local;
- } else
+ (isipv6 && in6_localaddr(&tp->t_inpcb->in6p_faddr)) ||
+ (!isipv6 &&
#endif /* INET6 */
- if (in_localaddr(tp->t_inpcb->inp_faddr))
- ss = ss_fltsz_local;
- tp->snd_cwnd = tp->t_maxseg * ss;
+ in_localaddr(tp->t_inpcb->inp_faddr)
+#ifdef INET6
+ )
+#endif /* INET6 */
+ )
+ tp->snd_cwnd = tp->t_maxseg * ss_fltsz_local;
+ else if (inc_init_win)
+ tp->snd_cwnd = min(tp->snd_cwnd,min(4*tp->t_maxseg,
+ max(2*tp->t_maxseg,4380)));
+ else
+ tp->snd_cwnd = tp->t_maxseg * ss_fltsz;
}
tp->t_flags &= ~TF_LASTIDLE;
if (idle) {
--- tcp_subr.c.orig Sat Aug 17 18:26:02 2002
+++ tcp_subr.c Wed Aug 21 11:12:24 2002
@@ -1408,6 +1408,14 @@
#endif
if (so->so_snd.sb_hiwat < mss)
mss = so->so_snd.sb_hiwat;
+ /*
+ * Follow suggestion in RFC 2414 to reduce the congestion
+ * window by the ratio of the old segment size to the new
+ * segment size.
+ */
+ if (mss < tp->t_maxseg)
+ tp->snd_cwnd = max((tp->snd_cwnd / tp->t_maxseg) *
+ mss, mss);
tp->t_maxseg = mss;
--- tcp_var.h.orig Sat Aug 17 18:26:02 2002
+++ tcp_var.h Wed Aug 21 11:12:24 2002
@@ -442,6 +442,7 @@
extern int path_mtu_discovery;
extern int ss_fltsz;
extern int ss_fltsz_local;
+extern int inc_init_win;
void tcp_canceltimers(struct tcpcb *);
struct tcpcb *
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