From 71efdc0b0207bfa8c1e4ad3eee9f4f26df6a58b4 Mon Sep 17 00:00:00 2001
From: Raj Bhattacharjea <raj.b@gatech.edu>
Date: Sat, 13 Dec 2008 23:44:20 -0500
Subject: [PATCH] Add a minimum RTO (adapted from Mathieu, bug 418)

---
 src/internet-stack/rtt-estimator.cc | 17 +++++++++++++++--
 src/internet-stack/rtt-estimator.h  |  1 +
 2 files changed, 16 insertions(+), 2 deletions(-)

diff --git a/src/internet-stack/rtt-estimator.cc b/src/internet-stack/rtt-estimator.cc
index e6a849c7b..1cd0655cf 100644
--- a/src/internet-stack/rtt-estimator.cc
+++ b/src/internet-stack/rtt-estimator.cc
@@ -51,6 +51,11 @@ RttEstimator::GetTypeId (void)
                    TimeValue (Seconds (1.0)),
                    MakeTimeAccessor (&RttEstimator::est),
                    MakeTimeChecker ())
+    .AddAttribute ("MinRTO", 
+                   "Minimum retransmit timeout value",
+                   TimeValue (Seconds (0.2)),
+                   MakeTimeAccessor (&RttEstimator::minrto),
+                   MakeTimeChecker ())
     ;
   return tid;
 }
@@ -217,9 +222,17 @@ Time RttMeanDeviation::RetransmitTimeout ()
 {
   // If not enough samples, justjust return 2 times estimate   
   //if (nSamples < 2) return est * 2;
+  Time retval;
   if (variance < est / Scalar (4.0))
-    return est * Scalar (2 * multiplier);            // At least twice current est
-  return (est + Scalar (4) * variance) * Scalar (multiplier); // As suggested by Jacobson
+    {
+      retval = est * Scalar (2 * multiplier);            // At least twice current est
+    }
+  else
+    {
+      retval = (est + Scalar (4) * variance) * Scalar (multiplier); // As suggested by Jacobson
+    }
+  retval = Max (retval, minrto);
+  return retval;
 }
 
 Ptr<RttEstimator> RttMeanDeviation::Copy () const
diff --git a/src/internet-stack/rtt-estimator.h b/src/internet-stack/rtt-estimator.h
index 6ee3ad48b..8128d663f 100644
--- a/src/internet-stack/rtt-estimator.h
+++ b/src/internet-stack/rtt-estimator.h
@@ -76,6 +76,7 @@ private:
   double m_maxMultiplier;
 public:
   Time       est;     // Current estimate
+  Time       minrto; // minimum value of the timeout
   uint32_t      nSamples;// Number of samples
   double       multiplier;   // RTO Multiplier
 };