Index: sys/netinet/cc/cc_newreno.c
===================================================================
--- sys/netinet/cc/cc_newreno.c
+++ sys/netinet/cc/cc_newreno.c
@@ -1,7 +1,7 @@
 /*-
  * Copyright (c) 1982, 1986, 1988, 1990, 1993, 1994, 1995
  *	The Regents of the University of California.
- * Copyright (c) 2007-2008,2010
+ * Copyright (c) 2007-2008,2010,2014
  *	Swinburne University of Technology, Melbourne, Australia.
  * Copyright (c) 2009-2010 Lawrence Stewart <lstewart@freebsd.org>
  * Copyright (c) 2010 The FreeBSD Foundation
@@ -46,6 +46,11 @@
  * University Research Program Fund at Community Foundation Silicon Valley.
  * More details are available at:
  *   http://caia.swin.edu.au/urp/newtcp/
+ *
+ * Dec 2014 garmitage@swin.edu.au
+ * Borrowed code fragments from cc_cdg.c to add modifiable beta
+ * via sysctls.
+ *
  */
 
 #include <sys/cdefs.h>
@@ -68,11 +73,21 @@
 #include <netinet/cc/cc.h>
 #include <netinet/cc/cc_module.h>
 
+#define	CAST_PTR_INT(X) (*((int*)(X)))
+
+#define	vnet_sysctl_handle_uint(oidp, arg1, arg2, req) \
+    sysctl_handle_int(oidp, arg1, arg2, req)
+
 static void	newreno_ack_received(struct cc_var *ccv, uint16_t type);
 static void	newreno_after_idle(struct cc_var *ccv);
 static void	newreno_cong_signal(struct cc_var *ccv, uint32_t type);
 static void	newreno_post_recovery(struct cc_var *ccv);
 
+static VNET_DEFINE(uint32_t, newreno_beta_loss) = 50;
+static VNET_DEFINE(uint32_t, newreno_beta_ecn) = 80;
+#define V_newreno_beta_loss VNET(newreno_beta_loss)
+#define V_newreno_beta_ecn VNET(newreno_beta_ecn)
+
 struct cc_algo newreno_cc_algo = {
 	.name = "newreno",
 	.ack_received = newreno_ack_received,
@@ -182,7 +197,7 @@
 static void
 newreno_cong_signal(struct cc_var *ccv, uint32_t type)
 {
-	uint32_t cwin, ssthresh_on_loss;
+	uint32_t cwin, ssthresh_on_loss, factor;
 	u_int mss;
 
 	cwin = CCV(ccv, snd_cwnd);
@@ -195,7 +210,11 @@
 	KASSERT((type & CC_SIGPRIVMASK) == 0,
 	    ("%s: congestion signal type 0x%08x is private\n", __func__, type));
 
-	cwin = max(cwin / 2 / mss, 2) * mss;
+	if (V_tcp_do_abe) 
+		factor = (type == CC_ECN ? V_newreno_beta_ecn : V_newreno_beta_loss);
+	else 
+		factor = 50;
+	cwin = max((cwin * factor) / (100 * mss), 2) * mss;
 
 	switch (type) {
 	case CC_NDUPACK:
@@ -252,5 +271,28 @@
 	}
 }
 
+static int
+newreno_beta_handler(SYSCTL_HANDLER_ARGS)
+{
+	if (req->newptr != NULL &&
+		(CAST_PTR_INT(req->newptr) <= 0 || CAST_PTR_INT(req->newptr) > 100))
+		return (EINVAL);
 
+	return (sysctl_handle_int(oidp, arg1, arg2, req));
+}
+
+SYSCTL_DECL(_net_inet_tcp_cc_newreno);
+SYSCTL_NODE(_net_inet_tcp_cc, OID_AUTO, newreno, CTLFLAG_RW, NULL,
+    "New Reno related settings");
+
+SYSCTL_PROC(_net_inet_tcp_cc_newreno, OID_AUTO, beta_loss,
+	CTLFLAG_VNET | CTLTYPE_UINT | CTLFLAG_RW,
+	&VNET_NAME(newreno_beta_loss), 3, &newreno_beta_handler, "IU",
+	"New Reno beta loss, specified as number between 0 and 100");
+
+SYSCTL_PROC(_net_inet_tcp_cc_newreno, OID_AUTO, beta_ecn,
+	CTLFLAG_VNET | CTLTYPE_UINT | CTLFLAG_RW,
+	&VNET_NAME(newreno_beta_ecn), 3, &newreno_beta_handler, "IU",
+	"New Reno beta ecn, specified as number between 0 and 100");
+
 DECLARE_CC_MODULE(newreno, &newreno_cc_algo);
Index: sys/netinet/tcp_input.c
===================================================================
--- sys/netinet/tcp_input.c
+++ sys/netinet/tcp_input.c
@@ -181,6 +181,11 @@
     &VNET_NAME(tcp_abc_l_var), 2,
     "Cap the max cwnd increment during slow-start to this number of segments");
 
+VNET_DEFINE(int, tcp_do_abe) = 0;
+SYSCTL_INT(_net_inet_tcp, OID_AUTO, abe, CTLFLAG_VNET | CTLFLAG_RW,
+    &VNET_NAME(tcp_do_abe), 0,
+    "Enable TCP Alternative Backoff with ECN (ABE)");
+
 static SYSCTL_NODE(_net_inet_tcp, OID_AUTO, ecn, CTLFLAG_RW, 0, "TCP ECN");
 
 VNET_DEFINE(int, tcp_do_ecn) = 2;
Index: sys/netinet/tcp_var.h
===================================================================
--- sys/netinet/tcp_var.h
+++ sys/netinet/tcp_var.h
@@ -709,6 +709,7 @@
 VNET_DECLARE(int, path_mtu_discovery);
 VNET_DECLARE(int, tcp_do_rfc3465);
 VNET_DECLARE(int, tcp_abc_l_var);
+VNET_DECLARE(int, tcp_do_abe);
 #define	V_tcb			VNET(tcb)
 #define	V_tcbinfo		VNET(tcbinfo)
 #define	V_tcp_mssdflt		VNET(tcp_mssdflt)
@@ -721,6 +722,7 @@
 #define	V_path_mtu_discovery	VNET(path_mtu_discovery)
 #define	V_tcp_do_rfc3465	VNET(tcp_do_rfc3465)
 #define	V_tcp_abc_l_var		VNET(tcp_abc_l_var)
+#define	V_tcp_do_abe		VNET(tcp_do_abe)
 
 VNET_DECLARE(int, tcp_do_sack);			/* SACK enabled/disabled */
 VNET_DECLARE(int, tcp_sc_rst_sock_fail);	/* RST on sock alloc failure */