Gitweb:     
http://git.kernel.org/git/?p=linux/kernel/git/torvalds/linux-2.6.git;a=commit;h=c462238d6a6d8ee855bda10f9fff442971540ed2
Commit:     c462238d6a6d8ee855bda10f9fff442971540ed2
Parent:     9be9a6b983314dd57e2c5ba548dee8b53d338ac3
Author:     Stephen Hemminger <[EMAIL PROTECTED]>
AuthorDate: Fri Apr 20 17:07:51 2007 -0700
Committer:  David S. Miller <[EMAIL PROTECTED]>
CommitDate: Wed Apr 25 22:29:23 2007 -0700

    [TCP]: TCP Illinois congestion control (rev3)
    
    This is an implementation of TCP Illinois invented by Shao Liu
    at University of Illinois. It is a another variant of Reno which adapts
    the alpha and beta parameters based on RTT. The basic idea is to increase
    window less rapidly as delay approaches the maximum. See the papers
    and talks to get a more complete description.
    
    Signed-off-by: Stephen Hemminger <[EMAIL PROTECTED]>
    Signed-off-by: David S. Miller <[EMAIL PROTECTED]>
---
 net/ipv4/Kconfig        |   13 ++
 net/ipv4/Makefile       |    1 +
 net/ipv4/tcp_illinois.c |  284 +++++++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 298 insertions(+), 0 deletions(-)

diff --git a/net/ipv4/Kconfig b/net/ipv4/Kconfig
index dc61e66..e62aee0 100644
--- a/net/ipv4/Kconfig
+++ b/net/ipv4/Kconfig
@@ -588,6 +588,19 @@ config TCP_CONG_YEAH
        For further details look here:
          http://wil.cs.caltech.edu/pfldnet2007/paper/YeAH_TCP.pdf
 
+config TCP_CONG_ILLINOIS
+       tristate "TCP Illinois"
+       depends on EXPERIMENTAL
+       default n
+       ---help---
+       TCP-Illinois is a sender-side modificatio of TCP Reno for
+       high speed long delay links. It uses round-trip-time to
+       adjust the alpha and beta parameters to achieve a higher average
+       throughput and maintain fairness.
+
+       For further details see:
+         http://www.ews.uiuc.edu/~shaoliu/tcpillinois/index.html
+
 choice
        prompt "Default TCP congestion control"
        default DEFAULT_CUBIC
diff --git a/net/ipv4/Makefile b/net/ipv4/Makefile
index eeb94d5..4ff6c15 100644
--- a/net/ipv4/Makefile
+++ b/net/ipv4/Makefile
@@ -50,6 +50,7 @@ obj-$(CONFIG_TCP_CONG_VENO) += tcp_veno.o
 obj-$(CONFIG_TCP_CONG_SCALABLE) += tcp_scalable.o
 obj-$(CONFIG_TCP_CONG_LP) += tcp_lp.o
 obj-$(CONFIG_TCP_CONG_YEAH) += tcp_yeah.o
+obj-$(CONFIG_TCP_CONG_ILLINOIS) += tcp_illinois.o
 obj-$(CONFIG_NETLABEL) += cipso_ipv4.o
 
 obj-$(CONFIG_XFRM) += xfrm4_policy.o xfrm4_state.o xfrm4_input.o \
diff --git a/net/ipv4/tcp_illinois.c b/net/ipv4/tcp_illinois.c
new file mode 100644
index 0000000..91a2a34
--- /dev/null
+++ b/net/ipv4/tcp_illinois.c
@@ -0,0 +1,284 @@
+/*
+ * TCP Illinois congestion control.
+ * Home page:
+ *     http://www.ews.uiuc.edu/~shaoliu/tcpillinois/index.html
+ *
+ * The algorithm is described in:
+ * "TCP-Illinois: A Loss and Delay-Based Congestion Control Algorithm
+ *  for High-Speed Networks"
+ * http://www.ews.uiuc.edu/~shaoliu/papersandslides/liubassri06perf.pdf
+ *
+ * Implemented from description in paper and ns-2 simulation.
+ * Copyright (C) 2007 Stephen Hemminger <[EMAIL PROTECTED]>
+ */
+
+#include <linux/module.h>
+#include <linux/skbuff.h>
+#include <linux/inet_diag.h>
+#include <asm/div64.h>
+#include <net/tcp.h>
+
+#define ALPHA_SHIFT    7
+#define ALPHA_SCALE    (1u<<ALPHA_SHIFT)
+#define ALPHA_MIN      ((3*ALPHA_SCALE)/10)    /* ~0.3 */
+#define ALPHA_MAX      (10*ALPHA_SCALE)        /* 10.0 */
+#define ALPHA_BASE     ALPHA_SCALE             /* 1.0 */
+
+#define BETA_SHIFT     6
+#define BETA_SCALE     (1u<<BETA_SHIFT)
+#define BETA_MIN       (BETA_SCALE/8)          /* 0.8 */
+#define BETA_MAX       (BETA_SCALE/2)
+#define BETA_BASE      BETA_MAX                /* 0.5 */
+
+#define THETA          5
+
+static int win_thresh __read_mostly = 15;
+module_param(win_thresh, int, 0644);
+MODULE_PARM_DESC(win_thresh, "Window threshold for starting adaptive sizing");
+
+#define MAX_RTT                0x7fffffff
+
+/* TCP Illinois Parameters */
+struct tcp_illinois {
+       u32     last_alpha;
+       u32     min_rtt;
+       u32     max_rtt;
+       u32     rtt_low;
+       u32     rtt_cnt;
+       u64     sum_rtt;
+};
+
+static void tcp_illinois_init(struct sock *sk)
+{
+       struct tcp_illinois *ca = inet_csk_ca(sk);
+
+       ca->last_alpha = ALPHA_BASE;
+       ca->min_rtt = 0x7fffffff;
+}
+
+/*
+ * Keep track of min, max and average RTT
+ */
+static void tcp_illinois_rtt_calc(struct sock *sk, u32 rtt)
+{
+       struct tcp_illinois *ca = inet_csk_ca(sk);
+
+       if (rtt < ca->min_rtt)
+               ca->min_rtt = rtt;
+       if (rtt > ca->max_rtt)
+               ca->max_rtt = rtt;
+
+       if (++ca->rtt_cnt == 1)
+               ca->sum_rtt = rtt;
+       else
+               ca->sum_rtt += rtt;
+}
+
+/* max queuing delay */
+static inline u32 max_delay(const struct tcp_illinois *ca)
+{
+       return ca->max_rtt - ca->min_rtt;
+}
+
+/* average queueing delay */
+static u32 avg_delay(struct tcp_illinois *ca)
+{
+       u64 avg_rtt = ca->sum_rtt;
+
+       do_div(avg_rtt, ca->rtt_cnt);
+
+       ca->sum_rtt = 0;
+       ca->rtt_cnt = 0;
+
+       return avg_rtt - ca->min_rtt;
+}
+
+/*
+ * Compute value of alpha used for additive increase.
+ * If small window then use 1.0, equivalent to Reno.
+ *
+ * For larger windows, adjust based on average delay.
+ * A. If average delay is at minimum (we are uncongested),
+ *    then use large alpha (10.0) to increase faster.
+ * B. If average delay is at maximum (getting congested)
+ *    then use small alpha (1.0)
+ *
+ * The result is a convex window growth curve.
+ */
+static u32 alpha(const struct sock *sk)
+{
+       struct tcp_sock *tp = tcp_sk(sk);
+       struct tcp_illinois *ca = inet_csk_ca(sk);
+       u32 dm = max_delay(ca);
+       u32 da = avg_delay(ca);
+       u32 d1, a;
+
+       if (tp->snd_cwnd < win_thresh)
+               return ALPHA_BASE;      /* same as Reno (1.0) */
+
+       d1 = dm / 100;
+       if (da <= d1) {
+               /* Don't let noise force agressive response */
+               if (ca->rtt_low < THETA) {
+                       ++ca->rtt_low;
+                       return ca->last_alpha;
+               } else
+                       return ALPHA_MAX;
+       }
+
+       ca->rtt_low = 0;
+
+       /*
+        * Based on:
+        *
+        *      (dm - d1) amin amax
+        * k1 = -------------------
+        *         amax - amin
+        *
+        *       (dm - d1) amin
+        * k2 = ----------------  - d1
+        *        amax - amin
+        *
+        *             k1
+        * alpha = ----------
+        *          k2 + da
+        */
+
+       dm -= d1;
+       da -= d1;
+
+       a = (dm * ALPHA_MAX) / (dm - (da  * (ALPHA_MAX - ALPHA_MIN)) / 
ALPHA_MIN);
+       ca->last_alpha = a;
+       return a;
+}
+
+/*
+ * Increase window in response to successful acknowledgment.
+ */
+static void tcp_illinois_cong_avoid(struct sock *sk, u32 ack, u32 rtt,
+                                   u32 in_flight, int flag)
+{
+       struct tcp_sock *tp = tcp_sk(sk);
+
+       /* RFC2861 only increase cwnd if fully utilized */
+       if (!tcp_is_cwnd_limited(sk, in_flight))
+               return;
+
+       /* In slow start */
+       if (tp->snd_cwnd <= tp->snd_ssthresh)
+               tcp_slow_start(tp);
+
+       else {
+               /* additive increase  cwnd += alpha / cwnd */
+               if ((tp->snd_cwnd_cnt * alpha(sk)) >> ALPHA_SHIFT >= 
tp->snd_cwnd) {
+                       if (tp->snd_cwnd < tp->snd_cwnd_clamp)
+                               tp->snd_cwnd++;
+                       tp->snd_cwnd_cnt = 0;
+               } else
+                       tp->snd_cwnd_cnt++;
+       }
+}
+
+/*
+ * Beta used for multiplicative decrease.
+ * For small window sizes returns same value as Reno (0.5)
+ *
+ * If delay is small (10% of max) then beta = 1/8
+ * If delay is up to 80% of max then beta = 1/2
+ * In between is a linear function
+ */
+static inline u32 beta(struct sock *sk)
+{
+       struct tcp_sock *tp = tcp_sk(sk);
+       struct tcp_illinois *ca = inet_csk_ca(sk);
+       u32 dm = max_delay(ca);
+       u32 da = avg_delay(ca);
+       u32 d2, d3;
+
+       if (tp->snd_cwnd < win_thresh)
+               return BETA_BASE;
+
+       d2 = dm / 10;
+       if (da <= d2)
+               return BETA_MIN;
+       d3 = (8 * dm) / 10;
+       if (da >= d3 || d3 <= d2)
+               return BETA_MAX;
+
+       /*
+        * Based on:
+        *
+        *       bmin d3 - bmax d2
+        * k3 = -------------------
+        *         d3 - d2
+        *
+        *       bmax - bmin
+        * k4 = -------------
+        *         d3 - d2
+        *
+        * b = k3 + k4 da
+        */
+       return (BETA_MIN * d3 - BETA_MAX * d2 + (BETA_MAX - BETA_MIN) * da)
+               / (d3 - d2);
+}
+
+static u32 tcp_illinois_ssthresh(struct sock *sk)
+{
+       struct tcp_sock *tp = tcp_sk(sk);
+
+       /* Multiplicative decrease */
+       return max((tp->snd_cwnd * beta(sk)) >> BETA_SHIFT, 2U);
+}
+
+/* Extract info for TCP socket info provided via netlink.
+ * We aren't really doing Vegas, but we can provide RTT info
+ */
+static void tcp_illinois_get_info(struct sock *sk, u32 ext,
+                              struct sk_buff *skb)
+{
+       const struct tcp_illinois *ca = inet_csk_ca(sk);
+
+       if (ext & (1 << (INET_DIAG_VEGASINFO - 1))) {
+               struct tcpvegas_info info = {
+                       .tcpv_enabled = 1,
+                       .tcpv_rttcnt = ca->rtt_cnt,
+                       .tcpv_minrtt = ca->min_rtt,
+               };
+               u64 avg_rtt = ca->sum_rtt;
+               do_div(avg_rtt, ca->rtt_cnt);
+               info.tcpv_rtt = avg_rtt;
+
+               nla_put(skb, INET_DIAG_VEGASINFO, sizeof(info), &info);
+       }
+}
+
+static struct tcp_congestion_ops tcp_illinois = {
+       .init           = tcp_illinois_init,
+       .ssthresh       = tcp_illinois_ssthresh,
+       .min_cwnd       = tcp_reno_min_cwnd,
+       .cong_avoid     = tcp_illinois_cong_avoid,
+       .rtt_sample     = tcp_illinois_rtt_calc,
+       .get_info       = tcp_illinois_get_info,
+
+       .owner          = THIS_MODULE,
+       .name           = "illinois",
+};
+
+static int __init tcp_illinois_register(void)
+{
+       BUILD_BUG_ON(sizeof(struct tcp_illinois) > ICSK_CA_PRIV_SIZE);
+       return tcp_register_congestion_control(&tcp_illinois);
+}
+
+static void __exit tcp_illinois_unregister(void)
+{
+       tcp_unregister_congestion_control(&tcp_illinois);
+}
+
+module_init(tcp_illinois_register);
+module_exit(tcp_illinois_unregister);
+
+MODULE_AUTHOR("Stephen Hemminger, Shao Liu");
+MODULE_LICENSE("GPL");
+MODULE_DESCRIPTION("TCP Illinois");
+MODULE_VERSION("0.3");
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