From 0e57976b6376f7fda6bef8b7dee2a3c8819ec9e9 Mon Sep 17 00:00:00 2001 From: John Heffner Date: Thu, 23 Jun 2005 12:29:07 -0700 Subject: [TCP]: Add Scalable TCP congestion control module. This patch implements Tom Kelly's Scalable TCP congestion control algorithm for the modular framework. The algorithm has some nice scaling properties, and has been used a fair bit in research, though is known to have significant fairness issues, so it's not really suitable for general purpose use. Signed-off-by: John Heffner Signed-off-by: David S. Miller --- net/ipv4/tcp_scalable.c | 68 +++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 68 insertions(+) create mode 100644 net/ipv4/tcp_scalable.c (limited to 'net/ipv4/tcp_scalable.c') diff --git a/net/ipv4/tcp_scalable.c b/net/ipv4/tcp_scalable.c new file mode 100644 index 000000000000..70e108e15c71 --- /dev/null +++ b/net/ipv4/tcp_scalable.c @@ -0,0 +1,68 @@ +/* Tom Kelly's Scalable TCP + * + * See htt://www-lce.eng.cam.ac.uk/~ctk21/scalable/ + * + * John Heffner + */ + +#include +#include +#include + +/* These factors derived from the recommended values in the aer: + * .01 and and 7/8. We use 50 instead of 100 to account for + * delayed ack. + */ +#define TCP_SCALABLE_AI_CNT 50U +#define TCP_SCALABLE_MD_SCALE 3 + +static void tcp_scalable_cong_avoid(struct tcp_sock *tp, u32 ack, u32 rtt, + u32 in_flight, int flag) +{ + if (in_flight < tp->snd_cwnd) + return; + + if (tp->snd_cwnd <= tp->snd_ssthresh) { + tp->snd_cwnd++; + } else { + tp->snd_cwnd_cnt++; + if (tp->snd_cwnd_cnt > min(tp->snd_cwnd, TCP_SCALABLE_AI_CNT)){ + tp->snd_cwnd++; + tp->snd_cwnd_cnt = 0; + } + } + tp->snd_cwnd = min_t(u32, tp->snd_cwnd, tp->snd_cwnd_clamp); + tp->snd_cwnd_stamp = tcp_time_stamp; +} + +static u32 tcp_scalable_ssthresh(struct tcp_sock *tp) +{ + return max(tp->snd_cwnd - (tp->snd_cwnd>>TCP_SCALABLE_MD_SCALE), 2U); +} + + +static struct tcp_congestion_ops tcp_scalable = { + .ssthresh = tcp_scalable_ssthresh, + .cong_avoid = tcp_scalable_cong_avoid, + .min_cwnd = tcp_reno_min_cwnd, + + .owner = THIS_MODULE, + .name = "scalable", +}; + +static int __init tcp_scalable_register(void) +{ + return tcp_register_congestion_control(&tcp_scalable); +} + +static void __exit tcp_scalable_unregister(void) +{ + tcp_unregister_congestion_control(&tcp_scalable); +} + +module_init(tcp_scalable_register); +module_exit(tcp_scalable_unregister); + +MODULE_AUTHOR("John Heffner"); +MODULE_LICENSE("GPL"); +MODULE_DESCRIPTION("Scalable TCP"); -- cgit v1.2.3-59-g8ed1b