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[TCP]: Add Scalable TCP congestion control module.

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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 <jheffner@psc.edu>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
John Heffner 2005-06-23 12:29:07 -07:00 committed by David S. Miller
parent a7868ea68d
commit 0e57976b63
3 changed files with 78 additions and 0 deletions
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9
net/ipv4/Kconfig
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@ -511,6 +511,15 @@ config TCP_CONG_VEGAS
window. TCP Vegas should provide less packet loss, but it is
not as aggressive as TCP Reno.
config TCP_CONG_SCALABLE
tristate "Scalable TCP"
depends on INET && EXPERIMENTAL
default n
---help---
Scalable TCP is a sender-side only change to TCP which uses a
MIMD congestion control algorithm which has some nice scaling
properties, though is known to have fairness issues.
See http://www-lce.eng.cam.ac.uk/~ctk21/scalable/
endmenu

1
net/ipv4/Makefile
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@ -37,6 +37,7 @@ obj-$(CONFIG_TCP_CONG_HSTCP) += tcp_highspeed.o
obj-$(CONFIG_TCP_CONG_HYBLA) += tcp_hybla.o
obj-$(CONFIG_TCP_CONG_HTCP) += tcp_htcp.o
obj-$(CONFIG_TCP_CONG_VEGAS) += tcp_vegas.o
obj-$(CONFIG_TCP_CONG_SCALABLE) += tcp_scalable.o
obj-$(CONFIG_XFRM) += xfrm4_policy.o xfrm4_state.o xfrm4_input.o \
xfrm4_output.o

68
net/ipv4/tcp_scalable.c Normal file
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@ -0,0 +1,68 @@
/* Tom Kelly's Scalable TCP
*
* See htt://www-lce.eng.cam.ac.uk/~ctk21/scalable/
*
* John Heffner <jheffner@sc.edu>
*/
#include <linux/config.h>
#include <linux/module.h>
#include <net/tcp.h>
/* 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");