Published:
Alrshah, M.A., Othman, M., Ali, B. and Hanapi, Z.M., 2015. Agile-SD: a
Linux-based
TCP congestion control algorithm for supporting high-speed and short-distance
networks.
Journal of Network and Computer Applications, 55, pp.181-190.
Agile-SD is a new loss-based and RTT-independent TCP congestion
control algorithm designed to support high-speed and Short-Distance (SD)
networks. It mainly contributes the agility factor mechanism, which allows
Agile-SD to deal with small buffer sizes while reducing its sensitivity to
packet loss. Due to the use of this mechanism, Agile-SD improves the
throughput of TCP up to 50% compared to Cubic-TCP and Compound-TCP. Its
performance was evaluated using the well-known NS2 simulator to measure
the average throughput, loss ratio and fairness.
Agile-SD is designed and implemented by Mohamed A. Alrshah et al. (2015) as
a Linux kernel module in the real Linux operating system (openSUSE 42.1 Leap),
which is implemented at the Network, Parallel and Distributed Computing
Laboratory,
A2.10, second floor, Block A, Faculty of Computer Science and Information
Technology,
Universiti Putra Malaysia, over real PCs connected to the Internet for daily
uses and
evaluation purposes.
The main motivation behind Agile-SD is to support the short-distance networks
such
as local area networks and data center networks in order to increase the
bandwidth
utilization over high-speed networks. Moreover, Agile-SD is introduced in
support
of the open source community, where it can be used under the OpenGL agreement.
---
net/ipv4/Kconfig | 15 ++++
net/ipv4/Makefile | 1 +
net/ipv4/tcp_agilesd.c | 221 +++++++++++++++++++++++++++++++++++++++++++++++++
3 files changed, 237 insertions(+)
create mode 100755 net/ipv4/tcp_agilesd.c
diff --git a/net/ipv4/Kconfig b/net/ipv4/Kconfig
index 91a25579..22d824b1 100644
--- a/net/ipv4/Kconfig
+++ b/net/ipv4/Kconfig
@@ -677,6 +677,17 @@ config TCP_CONG_BBR
bufferbloat, policers, or AQM schemes that do not provide a delay
signal. It requires the fq ("Fair Queue") pacing packet scheduler.
+config TCP_CONG_AGILESD
+ tristate "Agile-SD Congestion control"
+ default n
+ ---help---
+
+ This is version 1.0 of Agile-SD TCP. It is a sender-side only.
+ It contributes the Agility Factor (AF) to shorten the epoch time
+ and to make TCP independent from RTT. AF reduces the sensitivity
+ to packet losses, which in turn Agile-SD to achieve better throughput
+ over high-speed networks.
+
choice
prompt "Default TCP congestion control"
default DEFAULT_CUBIC
@@ -713,6 +724,9 @@ choice
config DEFAULT_BBR
bool "BBR" if TCP_CONG_BBR=y
+
+ config DEFAULT_AGILESD
+ bool "AGILESD" if TCP_CONG_AGILESD=y
config DEFAULT_RENO
bool "Reno"
@@ -738,6 +752,7 @@ config DEFAULT_TCP_CONG
default "dctcp" if DEFAULT_DCTCP
default "cdg" if DEFAULT_CDG
default "bbr" if DEFAULT_BBR
+ default "agilesd" if DEFAULT_AGILESD
default "cubic"
config TCP_MD5SIG
diff --git a/net/ipv4/Makefile b/net/ipv4/Makefile
index f83de23a..33d398b5 100644
--- a/net/ipv4/Makefile
+++ b/net/ipv4/Makefile
@@ -44,6 +44,7 @@ obj-$(CONFIG_INET_UDP_DIAG) += udp_diag.o
obj-$(CONFIG_INET_RAW_DIAG) += raw_diag.o
obj-$(CONFIG_NET_TCPPROBE) += tcp_probe.o
obj-$(CONFIG_TCP_CONG_BBR) += tcp_bbr.o
+obj-$(CONFIG_TCP_CONG_AGILESD) += tcp_agilesd.o
obj-$(CONFIG_TCP_CONG_BIC) += tcp_bic.o
obj-$(CONFIG_TCP_CONG_CDG) += tcp_cdg.o
obj-$(CONFIG_TCP_CONG_CUBIC) += tcp_cubic.o
diff --git a/net/ipv4/tcp_agilesd.c b/net/ipv4/tcp_agilesd.c
new file mode 100755
index 00000000..fd040ff2
--- /dev/null
+++ b/net/ipv4/tcp_agilesd.c
@@ -0,0 +1,221 @@
+/* agilesd is a Loss-Based Congestion Control Algorithm for TCP v1.0.
+ * agilesd has been created by Mohamed A. Alrshah,
+ * at Faculty of Computer Science and Information Technology,
+ * Universiti Putra Malaysia.
+ * agilesd is based on the article, which is published in 2015 as below:
+ *
+ * Alrshah, M.A., Othman, M., Ali, B. and Hanapi, Z.M., 2015.
+ * Agile-SD: a Linux-based TCP congestion control algorithm for supporting
high-speed and short-distance networks.
+ * Journal of Network and Computer Applications, 55, pp.181-190.
+ */
+
+/* These includes are very important to operate the algorithm under NS2. */
+//#define NS_PROTOCOL "tcp_agilesd.c"
+//#include "../ns-linux-c.h"
+//#include "../ns-linux-util.h"
+//#include <math.h>
+/* These includes are very important to operate the algorithm under NS2. */
+
+/* These includes are very important to operate the algorithm under Linux OS.
*/
+#include <linux/mm.h>
+#include <linux/module.h>
+#include <linux/math64.h>
+#include <net/tcp.h>
+//#include <linux/skbuff.h> // optional
+//#include <linux/inet_diag.h> // optional
+/* These includes are very important to operate the algorithm under Linux OS.
*/
+
+#define SCALE 1000 /* Scale factor to avoid fractions */
+#define Double_SCALE 1000000 /* Double_SCALE must be equal to SCALE^2 */
+#define beta 900 /* beta for multiplicative
decrease */
+
+static int initial_ssthresh __read_mostly;
+//static int beta __read_mostly = 900; /*the initial value of beta is equal to
90%*/
+
+module_param(initial_ssthresh, int, 0644);
+MODULE_PARM_DESC(initial_ssthresh, "initial value of slow start threshold");
+//module_param(beta, int, 0444);
+//MODULE_PARM_DESC(beta, "beta for multiplicative decrease");
+
+/* agilesd Parameters */
+struct agilesdtcp {
+ u32 loss_cwnd; // congestion window at
last loss.
+ u32 frac_tracer; // This is to trace the
fractions of the increment.
+ u32 degraded_loss_cwnd; // loss_cwnd after degradation.
+ enum dystate{SS=0, CA=1} agilesd_tcp_status;
+};
+
+static inline void agilesdtcp_reset(struct sock *sk)
+{
+ /*After timeout loss cntRTT and baseRTT must be reset to the initial
values as below */
+}
+
+/* This function is called after the first acknowledgment is received and
before the congestion
+ * control algorithm will be called for the first time. If the congestion
control algorithm has
+ * private data, it should initialize its private date here. */
+static void agilesdtcp_init(struct sock *sk)
+{
+ struct agilesdtcp *ca = inet_csk_ca(sk);
+
+ // If the value of initial_ssthresh is not set, snd_ssthresh will be
initialized by a large value.
+ if (initial_ssthresh)
+ tcp_sk(sk)->snd_ssthresh = initial_ssthresh;
+ else
+ tcp_sk(sk)->snd_ssthresh = 0x7fffffff;
+
+ ca->loss_cwnd = 0;
+ ca->frac_tracer = 0;
+ ca->agilesd_tcp_status = SS;
+}
+
+/* This function is called whenever an ack is received and the congestion
window can be increased.
+ * This is equivalent to opencwnd in tcp.cc.
+ * ack is the number of bytes that are acknowledged in the latest
acknowledgment;
+ * rtt is the the rtt measured by the latest acknowledgment;
+ * in_flight is the packet in flight before the latest acknowledgment;
+ * good_ack is an indicator whether the current situation is normal (no
duplicate ack, no loss and no SACK). */
+static void agilesdtcp_cong_avoid(struct sock *sk, u32 ack, u32 in_flight)
//For Linux Kernel Use.
+//static void agilesdtcp_cong_avoid(struct sock *sk, u32 ack, u32 seq_rtt, u32
in_flight, int data_acked) //For NS2 Use.
+{
+ struct tcp_sock *tp = tcp_sk(sk);
+ struct agilesdtcp *ca = inet_csk_ca(sk);
+ u32 inc_factor;
+ u32 ca_inc;
+ u32 current_gap, total_gap;
+ /* The value of inc_factor is limited by lower_fl and upper_fl.
+ * The lower_fl must be always = 1. The greater the upper_fl the higher
the aggressiveness.
+ * But, if upper_fl set to 1, agilesd will work exactly as newreno.
+ * We have already designed an equation to calculate the optimum
upper_fl based on the given beta.
+ * This equation will be revealed once its article is published*/
+ u32 lower_fl = 1 * SCALE;
+ u32 upper_fl = 3 * SCALE;
+
+ //if (!tcp_is_cwnd_limited(sk, in_flight)) return; //For NS-2 Use,
if the in flight packets not >= cwnd do nothing//
+ if (!tcp_is_cwnd_limited(sk)) return; // For Linux
Kernel Use.
+
+ if (tp->snd_cwnd < tp->snd_ssthresh){
+ ca->agilesd_tcp_status = SS;
+ //tcp_slow_start(tp); //For NS-2 Use
+ tcp_slow_start(tp, in_flight); // For Linux
Kernel Use.
+ }
+ else {
+ ca->agilesd_tcp_status = CA;
+
+ if (ca->loss_cwnd > ca->degraded_loss_cwnd)
+ total_gap = ca->loss_cwnd - ca->degraded_loss_cwnd;
+ else
+ total_gap = 1;
+
+ if (ca->loss_cwnd > tp->snd_cwnd)
+ current_gap = ca->loss_cwnd - tp->snd_cwnd;
+ else
+ current_gap = 0;
+
+ inc_factor = min(max(((upper_fl * current_gap) / total_gap),
lower_fl), upper_fl);
+
+ ca_inc = ((inc_factor * SCALE) / tp->snd_cwnd); /* SCALE is
used to avoid fractions*/
+
+ ca->frac_tracer += ca_inc; /* This in
order to take the fraction increase into account */
+ if (ca->frac_tracer >= Double_SCALE) /* To take factor scale
into account */
+ {
+ tp->snd_cwnd += 1;
+ ca->frac_tracer -= Double_SCALE;
+ }
+ }
+}
+
+/* This function is called when the TCP flow detects a loss.
+ * It returns the slow start threshold of a flow, after a packet loss is
detected. */
+static u32 agilesdtcp_recalc_ssthresh(struct sock *sk)
+{
+ const struct tcp_sock *tp = tcp_sk(sk);
+ struct agilesdtcp *ca = inet_csk_ca(sk);
+
+ ca->loss_cwnd = tp->snd_cwnd;
+
+ if (ca->agilesd_tcp_status == CA)
+ ca->degraded_loss_cwnd = max((tp->snd_cwnd * beta) / SCALE, 2U);
+ else
+ ca->degraded_loss_cwnd = max((tp->snd_cwnd * beta) / SCALE, 2U);
+
+ ca->frac_tracer = 0;
+
+ return ca->degraded_loss_cwnd;
+}
+
+/* This function is called when the TCP flow detects a loss.
+ * It returns the congestion window of a flow, after a packet loss is detected;
+ * (for many algorithms, this will be equal to ssthresh). When a loss is
detected,
+ * min_cwnd is called after ssthresh. But some others algorithms might set
min_cwnd
+ * to be smaller than ssthresh. If this is the case, there will be a slow
start after loss recovery. */
+//static u32 agilesdtcp_min_cwnd(const struct sock *sk)
+//{
+// return tcp_sk(sk)->snd_ssthresh;
+//}
+
+static u32 agilesdtcp_undo_cwnd(struct sock *sk)
+{
+ const struct tcp_sock *tp = tcp_sk(sk);
+ const struct agilesdtcp *ca = inet_csk_ca(sk);
+ return max(tp->snd_cwnd, ca->loss_cwnd);
+}
+
+/* This function is called when the congestion state of the TCP is changed.
+ * newstate is the state code for the state that TCP is going to be in.
+ * The possible states are listed below:
+ * The current congestion control state, which can be one of the followings:
+ * TCP_CA_Open: normal state
+ * TCP_CA_Recovery: Loss Recovery after a Fast Transmission
+ * TCP_CA_Loss: Loss Recovery after a Timeout
+ * (The following two states are not effective in TCP-Linux but is effective
in Linux)
+ * TCP_CA_Disorder: duplicate packets detected, but haven't reach the
threshold. So TCP shall assume that packet reordering is happening.
+ * TCP_CA_CWR: the state that congestion window is decreasing (after local
congestion in NIC, or ECN and etc).
+ * It is to notify the congestion control algorithm and is used by some
+ * algorithms which turn off their special control during loss recovery. */
+static void agilesdtcp_state(struct sock *sk, u8 new_state)
+{
+ if (new_state == TCP_CA_Loss)
+ agilesdtcp_reset(inet_csk_ca(sk));
+}
+
+/* This function is called when there is an acknowledgment that acknowledges
some new packets.
+ * num_acked is the number of packets that are acknowledged by this
acknowledgments. */
+//static void agilesdtcp_acked(struct sock *sk, u32 num_acked, ktime_t rtt_us)
//For NS2 Use.
+static void agilesdtcp_acked(struct sock *sk, u32 num_acked, s32 rtt_us)
//For Linux Kernel Use.
+{
+
+}
+
+static struct tcp_congestion_ops agilesdtcp __read_mostly = {
+ .init = agilesdtcp_init,
+ .ssthresh = agilesdtcp_recalc_ssthresh, //REQUIRED
+ .cong_avoid = agilesdtcp_cong_avoid, //REQUIRED
+ .set_state = agilesdtcp_state,
+ .undo_cwnd = agilesdtcp_undo_cwnd,
+ .pkts_acked = agilesdtcp_acked,
+ .owner = THIS_MODULE,
+ .name = "agilesd", //REQUIRED
+ //.min_cwnd = agilesdtcp_min_cwnd, //NOT REQUIRED
+};
+
+static int __init agilesdtcp_register(void)
+{
+ BUILD_BUG_ON(sizeof(struct agilesdtcp) > ICSK_CA_PRIV_SIZE);
+ return tcp_register_congestion_control(&agilesdtcp);
+}
+
+static void __exit agilesdtcp_unregister(void)
+{
+ tcp_unregister_congestion_control(&agilesdtcp);
+}
+
+module_init(agilesdtcp_register);
+module_exit(agilesdtcp_unregister);
+
+MODULE_AUTHOR("Mohamed A. Alrshah <[email protected]>");
+MODULE_AUTHOR("Mohamed Othman");
+MODULE_AUTHOR("Borhanuddin Ali");
+MODULE_AUTHOR("Zurina Hanapi");
+MODULE_LICENSE("Dual BSD/GPL");
+MODULE_DESCRIPTION("agilesd is a Loss-Based Congestion Control Algorithm for
TCP v1.0. By Mohamed A. Alrshah");
+MODULE_VERSION("1.0");
--
2.12.3
