[TCP]: Add TCP Hybla congestion control module.

TCP Hybla congestion avoidance. - "In heterogeneous networks, TCP connections that incorporate a terrestrial or satellite radio link are greatly disadvantaged with respect to entirely wired connections, because of their longer round trip times (RTTs). To cope with this problem, a new TCP proposal, the TCP Hybla, is presented and discussed in the paper[1]. It stems from an analytical evaluation of the congestion window dynamics in the TCP standard versions (Tahoe, Reno, NewReno), which suggests the necessary modifications to remove the performance dependence on RTT.[...]"[1] [1]: Carlo Caini, Rosario Firrincieli, "TCP Hybla: a TCP enhancement for heterogeneous networks", International Journal of Satellite Communications and Networking Volume 22, Issue 5 , Pages 547 - 566. September 2004. Signed-off-by: Daniele Lacamera (root at danielinux.net)net Signed-off-by: Stephen Hemminger <shemminger@osdl.org> Signed-off-by: David S. Miller <davem@davemloft.net>

[TCP]: Add TCP Hybla congestion control module.
TCP Hybla congestion avoidance. - "In heterogeneous networks, TCP connections that incorporate a terrestrial or satellite radio link are greatly disadvantaged with respect to entirely wired connections, because of their longer round trip times (RTTs). To cope with this problem, a new TCP proposal, the TCP Hybla, is presented and discussed in the paper[1]. It stems from an analytical evaluation of the congestion window dynamics in the TCP standard versions (Tahoe, Reno, NewReno), which suggests the necessary modifications to remove the performance dependence on RTT.[...]"[1] [1]: Carlo Caini, Rosario Firrincieli, "TCP Hybla: a TCP enhancement for heterogeneous networks", International Journal of Satellite Communications and Networking Volume 22, Issue 5 , Pages 547 - 566. September 2004. Signed-off-by: Daniele Lacamera (root at danielinux.net)net Signed-off-by: Stephen Hemminger <shemminger@osdl.org> Signed-off-by: David S. Miller <davem@davemloft.net>
Daniele Lacamera · David S. Miller
1 parent a628d29b56
Showing 3 changed files with 198 additions and 0 deletions Side-by-side Diff
net/ipv4/Kconfig
net/ipv4/Makefile
net/ipv4/tcp_hybla.c
@@ -478,6 +478,16 @@
 	increase the congestion window by when an ACK is received.
  	For more detail	see http://www.icir.org/floyd/hstcp.html
  
+config TCP_CONG_HYBLA
+	tristate "TCP-Hybla congestion control algorithm"
+	depends on INET && EXPERIMENTAL
+	default n
+	---help---
+	TCP-Hybla is a sender-side only change that eliminates penalization of
+	long-RTT, large-bandwidth connections, like when satellite legs are
+	involved, expecially when sharing a common bottleneck with normal
+	terrestrial connections.
+
 endmenu
  
 source "net/ipv4/ipvs/Kconfig"
@@ -34,6 +34,7 @@
 obj-$(CONFIG_TCP_CONG_BIC) += tcp_bic.o
 obj-$(CONFIG_TCP_CONG_WESTWOOD) += tcp_westwood.o
 obj-$(CONFIG_TCP_CONG_HSTCP) += tcp_highspeed.o
+obj-$(CONFIG_TCP_CONG_HYBLA) += tcp_hybla.o
  
 obj-$(CONFIG_XFRM) += xfrm4_policy.o xfrm4_state.o xfrm4_input.o \
 		      xfrm4_output.o
+/*
+ * TCP HYBLA
+ *
+ * TCP-HYBLA Congestion control algorithm, based on:
+ *   C.Caini, R.Firrincieli, "TCP-Hybla: A TCP Enhancement
+ *   for Heterogeneous Networks",
+ *   International Journal on satellite Communications,
+ *				       September 2004
+ *    Daniele Lacamera
+ *    root at danielinux.net
+ */
+
+#include <linux/config.h>
+#include <linux/module.h>
+#include <net/tcp.h>
+
+/* Tcp Hybla structure. */
+struct hybla {
+	u8    hybla_en;
+	u32   snd_cwnd_cents; /* Keeps increment values when it is <1, <<7 */
+	u32   rho;	      /* Rho parameter, integer part  */
+	u32   rho2;	      /* Rho * Rho, integer part */
+	u32   rho_3ls;	      /* Rho parameter, <<3 */
+	u32   rho2_7ls;	      /* Rho^2, <<7	*/
+	u32   minrtt;	      /* Minimum smoothed round trip time value seen */
+};
+
+/* Hybla reference round trip time (default= 1/40 sec = 25 ms),
+   expressed in jiffies */
+static int rtt0 = 25;
+module_param(rtt0, int, 0644);
+MODULE_PARM_DESC(rtt0, "reference rout trip time (ms)");
+
+
+/* This is called to refresh values for hybla parameters */
+static inline void hybla_recalc_param (struct tcp_sock *tp)
+{
+	struct hybla *ca = tcp_ca(tp);
+
+	ca->rho_3ls = max_t(u32, tp->srtt / msecs_to_jiffies(rtt0), 8);
+	ca->rho = ca->rho_3ls >> 3;
+	ca->rho2_7ls = (ca->rho_3ls * ca->rho_3ls) << 1;
+	ca->rho2 = ca->rho2_7ls >>7;
+}
+
+static void hybla_init(struct tcp_sock *tp)
+{
+	struct hybla *ca = tcp_ca(tp);
+
+	ca->rho = 0;
+	ca->rho2 = 0;
+	ca->rho_3ls = 0;
+	ca->rho2_7ls = 0;
+	ca->snd_cwnd_cents = 0;
+	ca->hybla_en = 1;
+	tp->snd_cwnd = 2;
+	tp->snd_cwnd_clamp = 65535;
+
+	/* 1st Rho measurement based on initial srtt */
+	hybla_recalc_param(tp);
+
+	/* set minimum rtt as this is the 1st ever seen */
+	ca->minrtt = tp->srtt;
+	tp->snd_cwnd = ca->rho;
+}
+
+static void hybla_state(struct tcp_sock *tp, u8 ca_state)
+{
+	struct hybla *ca = tcp_ca(tp);
+
+	ca->hybla_en = (ca_state == TCP_CA_Open);
+}
+
+static inline u32 hybla_fraction(u32 odds)
+{
+	static const u32 fractions[] = {
+		128, 139, 152, 165, 181, 197, 215, 234,
+	};
+
+	return (odds < ARRAY_SIZE(fractions)) ? fractions[odds] : 128;
+}
+
+/* TCP Hybla main routine.
+ * This is the algorithm behavior:
+ *     o Recalc Hybla parameters if min_rtt has changed
+ *     o Give cwnd a new value based on the model proposed
+ *     o remember increments <1
+ */
+static void hybla_cong_avoid(struct tcp_sock *tp, u32 ack, u32 rtt,
+			    u32 in_flight, int flag)
+{
+	struct hybla *ca = tcp_ca(tp);
+	u32 increment, odd, rho_fractions;
+	int is_slowstart = 0;
+
+	/*  Recalculate rho only if this srtt is the lowest */
+	if (tp->srtt < ca->minrtt){
+		hybla_recalc_param(tp);
+		ca->minrtt = tp->srtt;
+	}
+
+	if (!ca->hybla_en)
+		return tcp_reno_cong_avoid(tp, ack, rtt, in_flight, flag);
+
+	if (in_flight < tp->snd_cwnd)
+		return;
+
+	if (ca->rho == 0)
+		hybla_recalc_param(tp);
+
+	rho_fractions = ca->rho_3ls - (ca->rho << 3);
+
+	if (tp->snd_cwnd < tp->snd_ssthresh) {
+		/*
+		 * slow start
+		 *      INC = 2^RHO - 1
+		 * This is done by splitting the rho parameter
+		 * into 2 parts: an integer part and a fraction part.
+		 * Inrement<<7 is estimated by doing:
+		 *	       [2^(int+fract)]<<7
+		 * that is equal to:
+		 *	       (2^int)	*  [(2^fract) <<7]
+		 * 2^int is straightly computed as 1<<int,
+		 * while we will use hybla_slowstart_fraction_increment() to
+		 * calculate 2^fract in a <<7 value.
+		 */
+		is_slowstart = 1;
+		increment = ((1 << ca->rho) * hybla_fraction(rho_fractions))
+			- 128;
+	} else {
+		/*
+		 * congestion avoidance
+		 * INC = RHO^2 / W
+		 * as long as increment is estimated as (rho<<7)/window
+		 * it already is <<7 and we can easily count its fractions.
+		 */
+		increment = ca->rho2_7ls / tp->snd_cwnd;
+		if (increment < 128)
+			tp->snd_cwnd_cnt++;
+	}
+
+	odd = increment % 128;
+	tp->snd_cwnd += increment >> 7;
+	ca->snd_cwnd_cents += odd;
+
+	/* check when fractions goes >=128 and increase cwnd by 1. */
+	while(ca->snd_cwnd_cents >= 128) {
+		tp->snd_cwnd++;
+		ca->snd_cwnd_cents -= 128;
+		tp->snd_cwnd_cnt = 0;
+	}
+
+	/* clamp down slowstart cwnd to ssthresh value. */
+	if (is_slowstart)
+		tp->snd_cwnd = min(tp->snd_cwnd, tp->snd_ssthresh);
+
+	tp->snd_cwnd = min_t(u32, tp->snd_cwnd, tp->snd_cwnd_clamp);
+}
+
+static struct tcp_congestion_ops tcp_hybla = {
+	.init		= hybla_init,
+	.ssthresh	= tcp_reno_ssthresh,
+	.min_cwnd	= tcp_reno_min_cwnd,
+	.cong_avoid	= hybla_cong_avoid,
+	.set_state	= hybla_state,
+
+	.owner		= THIS_MODULE,
+	.name		= "hybla"
+};
+
+static int __init hybla_register(void)
+{
+	BUG_ON(sizeof(struct hybla) > TCP_CA_PRIV_SIZE);
+	return tcp_register_congestion_control(&tcp_hybla);
+}
+
+static void __exit hybla_unregister(void)
+{
+	tcp_unregister_congestion_control(&tcp_hybla);
+}
+
+module_init(hybla_register);
+module_exit(hybla_unregister);
+
+MODULE_AUTHOR("Daniele Lacamera");
+MODULE_LICENSE("GPL");
+MODULE_DESCRIPTION("TCP Hybla");
...	...	@@ -478,6 +478,16 @@
478	478	increase the congestion window by when an ACK is received.
479	479	For more detail see http://www.icir.org/floyd/hstcp.html
480	480
	481	+config TCP_CONG_HYBLA
	482	+ tristate "TCP-Hybla congestion control algorithm"
	483	+ depends on INET && EXPERIMENTAL
	484	+ default n
	485	+ ---help---
	486	+ TCP-Hybla is a sender-side only change that eliminates penalization of
	487	+ long-RTT, large-bandwidth connections, like when satellite legs are
	488	+ involved, expecially when sharing a common bottleneck with normal
	489	+ terrestrial connections.
	490	+
481	491	endmenu
482	492
483	493	source "net/ipv4/ipvs/Kconfig"
...	...	@@ -34,6 +34,7 @@
34	34	obj-$(CONFIG_TCP_CONG_BIC) += tcp_bic.o
35	35	obj-$(CONFIG_TCP_CONG_WESTWOOD) += tcp_westwood.o
36	36	obj-$(CONFIG_TCP_CONG_HSTCP) += tcp_highspeed.o
	37	+obj-$(CONFIG_TCP_CONG_HYBLA) += tcp_hybla.o
37	38
38	39	obj-$(CONFIG_XFRM) += xfrm4_policy.o xfrm4_state.o xfrm4_input.o \
39	40	xfrm4_output.o
	1	+/*
	2	+ * TCP HYBLA
	3	+ *
	4	+ * TCP-HYBLA Congestion control algorithm, based on:
	5	+ * C.Caini, R.Firrincieli, "TCP-Hybla: A TCP Enhancement
	6	+ * for Heterogeneous Networks",
	7	+ * International Journal on satellite Communications,
	8	+ * September 2004
	9	+ * Daniele Lacamera
	10	+ * root at danielinux.net
	11	+ */
	12	+
	13	+#include <linux/config.h>
	14	+#include <linux/module.h>
	15	+#include <net/tcp.h>
	16	+
	17	+/* Tcp Hybla structure. */
	18	+struct hybla {
	19	+ u8 hybla_en;
	20	+ u32 snd_cwnd_cents; /* Keeps increment values when it is <1, <<7 */
	21	+ u32 rho; /* Rho parameter, integer part */
	22	+ u32 rho2; /* Rho * Rho, integer part */
	23	+ u32 rho_3ls; /* Rho parameter, <<3 */
	24	+ u32 rho2_7ls; /* Rho^2, <<7 */
	25	+ u32 minrtt; /* Minimum smoothed round trip time value seen */
	26	+};
	27	+
	28	+/* Hybla reference round trip time (default= 1/40 sec = 25 ms),
	29	+ expressed in jiffies */
	30	+static int rtt0 = 25;
	31	+module_param(rtt0, int, 0644);
	32	+MODULE_PARM_DESC(rtt0, "reference rout trip time (ms)");
	33	+
	34	+
	35	+/* This is called to refresh values for hybla parameters */
	36	+static inline void hybla_recalc_param (struct tcp_sock *tp)
	37	+{
	38	+ struct hybla *ca = tcp_ca(tp);
	39	+
	40	+ ca->rho_3ls = max_t(u32, tp->srtt / msecs_to_jiffies(rtt0), 8);
	41	+ ca->rho = ca->rho_3ls >> 3;
	42	+ ca->rho2_7ls = (ca->rho_3ls * ca->rho_3ls) << 1;
	43	+ ca->rho2 = ca->rho2_7ls >>7;
	44	+}
	45	+
	46	+static void hybla_init(struct tcp_sock *tp)
	47	+{
	48	+ struct hybla *ca = tcp_ca(tp);
	49	+
	50	+ ca->rho = 0;
	51	+ ca->rho2 = 0;
	52	+ ca->rho_3ls = 0;
	53	+ ca->rho2_7ls = 0;
	54	+ ca->snd_cwnd_cents = 0;
	55	+ ca->hybla_en = 1;
	56	+ tp->snd_cwnd = 2;
	57	+ tp->snd_cwnd_clamp = 65535;
	58	+
	59	+ /* 1st Rho measurement based on initial srtt */
	60	+ hybla_recalc_param(tp);
	61	+
	62	+ /* set minimum rtt as this is the 1st ever seen */
	63	+ ca->minrtt = tp->srtt;
	64	+ tp->snd_cwnd = ca->rho;
	65	+}
	66	+
	67	+static void hybla_state(struct tcp_sock *tp, u8 ca_state)
	68	+{
	69	+ struct hybla *ca = tcp_ca(tp);
	70	+
	71	+ ca->hybla_en = (ca_state == TCP_CA_Open);
	72	+}
	73	+
	74	+static inline u32 hybla_fraction(u32 odds)
	75	+{
	76	+ static const u32 fractions[] = {
	77	+ 128, 139, 152, 165, 181, 197, 215, 234,
	78	+ };
	79	+
	80	+ return (odds < ARRAY_SIZE(fractions)) ? fractions[odds] : 128;
	81	+}
	82	+
	83	+/* TCP Hybla main routine.
	84	+ * This is the algorithm behavior:
	85	+ * o Recalc Hybla parameters if min_rtt has changed
	86	+ * o Give cwnd a new value based on the model proposed
	87	+ * o remember increments <1
	88	+ */
	89	+static void hybla_cong_avoid(struct tcp_sock *tp, u32 ack, u32 rtt,
	90	+ u32 in_flight, int flag)
	91	+{
	92	+ struct hybla *ca = tcp_ca(tp);
	93	+ u32 increment, odd, rho_fractions;
	94	+ int is_slowstart = 0;
	95	+
	96	+ /* Recalculate rho only if this srtt is the lowest */
	97	+ if (tp->srtt < ca->minrtt){
	98	+ hybla_recalc_param(tp);
	99	+ ca->minrtt = tp->srtt;
	100	+ }
	101	+
	102	+ if (!ca->hybla_en)
	103	+ return tcp_reno_cong_avoid(tp, ack, rtt, in_flight, flag);
	104	+
	105	+ if (in_flight < tp->snd_cwnd)
	106	+ return;
	107	+
	108	+ if (ca->rho == 0)
	109	+ hybla_recalc_param(tp);
	110	+
	111	+ rho_fractions = ca->rho_3ls - (ca->rho << 3);
	112	+
	113	+ if (tp->snd_cwnd < tp->snd_ssthresh) {
	114	+ /*
	115	+ * slow start
	116	+ * INC = 2^RHO - 1
	117	+ * This is done by splitting the rho parameter
	118	+ * into 2 parts: an integer part and a fraction part.
	119	+ * Inrement<<7 is estimated by doing:
	120	+ * [2^(int+fract)]<<7
	121	+ * that is equal to:
	122	+ * (2^int) * [(2^fract) <<7]
	123	+ * 2^int is straightly computed as 1<<int,
	124	+ * while we will use hybla_slowstart_fraction_increment() to
	125	+ * calculate 2^fract in a <<7 value.
	126	+ */
	127	+ is_slowstart = 1;
	128	+ increment = ((1 << ca->rho) * hybla_fraction(rho_fractions))
	129	+ - 128;
	130	+ } else {
	131	+ /*
	132	+ * congestion avoidance
	133	+ * INC = RHO^2 / W
	134	+ * as long as increment is estimated as (rho<<7)/window
	135	+ * it already is <<7 and we can easily count its fractions.
	136	+ */
	137	+ increment = ca->rho2_7ls / tp->snd_cwnd;
	138	+ if (increment < 128)
	139	+ tp->snd_cwnd_cnt++;
	140	+ }
	141	+
	142	+ odd = increment % 128;
	143	+ tp->snd_cwnd += increment >> 7;
	144	+ ca->snd_cwnd_cents += odd;
	145	+
	146	+ /* check when fractions goes >=128 and increase cwnd by 1. */
	147	+ while(ca->snd_cwnd_cents >= 128) {
	148	+ tp->snd_cwnd++;
	149	+ ca->snd_cwnd_cents -= 128;
	150	+ tp->snd_cwnd_cnt = 0;
	151	+ }
	152	+
	153	+ /* clamp down slowstart cwnd to ssthresh value. */
	154	+ if (is_slowstart)
	155	+ tp->snd_cwnd = min(tp->snd_cwnd, tp->snd_ssthresh);
	156	+
	157	+ tp->snd_cwnd = min_t(u32, tp->snd_cwnd, tp->snd_cwnd_clamp);
	158	+}
	159	+
	160	+static struct tcp_congestion_ops tcp_hybla = {
	161	+ .init = hybla_init,
	162	+ .ssthresh = tcp_reno_ssthresh,
	163	+ .min_cwnd = tcp_reno_min_cwnd,
	164	+ .cong_avoid = hybla_cong_avoid,
	165	+ .set_state = hybla_state,
	166	+
	167	+ .owner = THIS_MODULE,
	168	+ .name = "hybla"
	169	+};
	170	+
	171	+static int __init hybla_register(void)
	172	+{
	173	+ BUG_ON(sizeof(struct hybla) > TCP_CA_PRIV_SIZE);
	174	+ return tcp_register_congestion_control(&tcp_hybla);
	175	+}
	176	+
	177	+static void __exit hybla_unregister(void)
	178	+{
	179	+ tcp_unregister_congestion_control(&tcp_hybla);
	180	+}
	181	+
	182	+module_init(hybla_register);
	183	+module_exit(hybla_unregister);
	184	+
	185	+MODULE_AUTHOR("Daniele Lacamera");
	186	+MODULE_LICENSE("GPL");
	187	+MODULE_DESCRIPTION("TCP Hybla");