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Commit 0e57976b authored by John Heffner's avatar John Heffner Committed by David S. Miller
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[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: default avatarJohn Heffner <jheffner@psc.edu>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent a7868ea6

net/ipv4/Kconfig

+9 −0
Original line number Diff line number Diff line
@@ -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

net/ipv4/Makefile

+1 −0
Original line number Diff line number Diff line
@@ -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

net/ipv4/tcp_scalable.c

0 → 100644
+68 −0
Original line number Diff line number Diff line 
/* 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");