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[CCID3]: Use initial RTT sample from SYN exchange 

The patch follows the following recommendation made in an erratum to RFC 4342:

  "Senders MAY additionally make use of other available RTT measurements,
   including those from the initial Request-Response packet exchange."

It implements larger initial windows with regard to this inital RTT measurement,
using the mechanism suggested in draft-ietf-dccp-rfc3448bis, section 4.2.

Signed-off-by: Gerrit Renker <gerrit@erg.abdn.ac.uk>
Signed-off-by: Ian McDonald <ian.mcdonald@jandi.co.nz>
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Gerrit Renker 2007-03-20 15:31:56 -03:00 committed by David S. Miller
parent 89560b53b9
commit 30833ffead
1 changed files with 21 additions and 10 deletions
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31
net/dccp/ccids/ccid3.c
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@ -334,19 +334,30 @@ static int ccid3_hc_tx_send_packet(struct sock *sk, struct sk_buff *skb)
usecs_to_jiffies(TFRC_INITIAL_TIMEOUT)));
hctx->ccid3hctx_last_win_count = 0;
hctx->ccid3hctx_t_last_win_count = now;
ccid3_hc_tx_set_state(sk, TFRC_SSTATE_NO_FBACK);
/* Set initial sending rate X/s to 1pps (X is scaled by 2^6) */
hctx->ccid3hctx_x = hctx->ccid3hctx_s = skb->len;
hctx->ccid3hctx_x <<= 6;
/* First timeout, according to [RFC 3448, 4.2], is 1 second */
hctx->ccid3hctx_t_ipi = USEC_PER_SEC;
/* Initial delta: minimum of 0.5 sec and t_gran/2 */
hctx->ccid3hctx_delta = TFRC_OPSYS_HALF_TIME_GRAN;
/* Set t_0 for initial packet */
hctx->ccid3hctx_t_nom = now;
hctx->ccid3hctx_s = skb->len;
/*
* Use initial RTT sample when available: recommended by erratum
* to RFC 4342. This implements the initialisation procedure of
* draft rfc3448bis, section 4.2. Remember, X is scaled by 2^6.
*/
if (dp->dccps_syn_rtt) {
ccid3_pr_debug("SYN RTT = %uus\n", dp->dccps_syn_rtt);
hctx->ccid3hctx_rtt = dp->dccps_syn_rtt;
hctx->ccid3hctx_x = rfc3390_initial_rate(sk);
hctx->ccid3hctx_t_ld = now;
} else {
/* Sender does not have RTT sample: X = MSS/second */
hctx->ccid3hctx_x = dp->dccps_mss_cache;
hctx->ccid3hctx_x <<= 6;
}
ccid3_update_send_interval(hctx);
ccid3_hc_tx_set_state(sk, TFRC_SSTATE_NO_FBACK);
break;
case TFRC_SSTATE_NO_FBACK:
case TFRC_SSTATE_FBACK: