: Use initial RTT sample from SYN exchange
Subsystems (2)
PATCH 31/31 : 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 <[email protected]>
Signed-off-by Ian McDonald <[email protected]>
Signed-off-by Arnaldo Carvalho de Melo <[email protected]>
--- net/dccp/ccids/ccid3.c | 31 +++++++++++++++++++++---------- 1 files changed, 21 insertions(+), 10 deletions(-)
net/dccp/ccids/ccid3.c +21 -10
@@ -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 :
Signature · 1 line
1.5.0.3