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[TCP]: H-TCP maxRTT estimation at startup

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Small patch to H-TCP from Douglas Leith. 

Fix estimation of maxRTT.  The original code ignores rtt measurements
during slow start (via the check tp->snd_ssthresh < 0xFFFF) yet this
is probably a good time to try to estimate max rtt as delayed acking
is disabled and slow start will only exit on a loss which presumably
corresponds to a maxrtt measurement.  Second, the original code (via
the check htcp_ccount(ca) > 3) ignores rtt data during what it
estimates to be the first 3 round-trip times.  This seems like an
unnecessary check now that the RCV timestamp are no longer used
for rtt estimation.

Signed-off-by: Stephen Hemminger <shemminger@linux-foundation.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Stephen Hemminger 2007-08-07 18:29:05 -07:00 committed by David S. Miller
parent 591e620693
commit f34d1955df
1 changed files with 1 additions and 3 deletions
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4
net/ipv4/tcp_htcp.c
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@ -79,7 +79,6 @@ static u32 htcp_cwnd_undo(struct sock *sk)
static inline void measure_rtt(struct sock *sk, u32 srtt) static inline void measure_rtt(struct sock *sk, u32 srtt)
{ {
const struct inet_connection_sock *icsk = inet_csk(sk); const struct inet_connection_sock *icsk = inet_csk(sk);
const struct tcp_sock *tp = tcp_sk(sk);
struct htcp *ca = inet_csk_ca(sk); struct htcp *ca = inet_csk_ca(sk);
/* keep track of minimum RTT seen so far, minRTT is zero at first */ /* keep track of minimum RTT seen so far, minRTT is zero at first */
@ -87,8 +86,7 @@ static inline void measure_rtt(struct sock *sk, u32 srtt)
ca->minRTT = srtt; ca->minRTT = srtt;
/* max RTT */ /* max RTT */
if (icsk->icsk_ca_state == TCP_CA_Open if (icsk->icsk_ca_state == TCP_CA_Open) {
&& tp->snd_ssthresh < 0xFFFF && htcp_ccount(ca) > 3) {
if (ca->maxRTT < ca->minRTT) if (ca->maxRTT < ca->minRTT)
ca->maxRTT = ca->minRTT; ca->maxRTT = ca->minRTT;
if (ca->maxRTT < srtt if (ca->maxRTT < srtt