From f5c0605aab22303670187373df4e671abbcfa914 Mon Sep 17 00:00:00 2001
From: Tom Henderson <tomh@tomh.org>
Date: Wed, 30 May 2012 10:38:47 -0700
Subject: [PATCH] bug 1399: TCP not backing off retransmissions properly

---
 src/aodv/test/tcp-chain-test-0-0.pcap | Bin 40218 -> 36360 bytes
 src/aodv/test/tcp-chain-test-9-0.pcap | Bin 20784 -> 18354 bytes
 src/internet/model/rtt-estimator.cc   |  28 +++++++++-----------------
 3 files changed, 10 insertions(+), 18 deletions(-)

diff --git a/src/aodv/test/tcp-chain-test-0-0.pcap b/src/aodv/test/tcp-chain-test-0-0.pcap
index 3e74461a8522d1baf30a8b39b19c1661728abf8c..fdd863644b3a81d9786c7477fea4072c097f245e 100644
GIT binary patch
delta 27
jcmbQWi>YG{(+0NA$vk~Zn>9Lvm?k$&aM--7+m8tVnu`kV

delta 282
zcmeB}!!&Cb(+0Lq=AyGKli%yeZ`SAxVq*S&fn~BFmpD5U0|P_i6_&|{74n;Rb^9?*
z%43<#)~O`Gz_e-=Gf<9$!Igo@fkAe%fSkzYd)-=K1y$V+0uRs?OvqfeiDL#M&;aI7
z&$&Q02?(I7kwZ3wx%@R3+yxKcae-VQ@Bv)|lA%UldBKJ%psJCF8#=k5jg{#KFWgYY
RKfGW=8JJPLB0m{wC;+JzOsW6?

diff --git a/src/aodv/test/tcp-chain-test-9-0.pcap b/src/aodv/test/tcp-chain-test-9-0.pcap
index d214a163702a422ef6eb22bd120f35e297d7a3e4..174490484da8bdab1aedd0ded28f71a87cce6522 100644
GIT binary patch
delta 30
mcmdn6h;dUt<AxrW$=lo=HlJ|`Vw&vX<uEzU-D>h7FDU@e91M*B

delta 310
zcmdng&$wX`<Axp==9X71lMjlCPkvy|!u;+n%Va@z`ORlsf|!{90Xc#8(#$^ZSSCC2
z$xn`Rw_@ga&oa5tC0c-idDSXr1_lNW23H0q2L{>64_HMue{jiT5(r>K$S`Oy2u?2G
zlbC$YL1^*}cPVxzpcWQZZn%AU9NZxL1O!lxlY<(k$HZI*Q~`3t86fS*r@)VDx)98C
z<_=DvIvZ(b7a=~l>FY%Kz@{spnl6tpeIHN-$aEetK9Cm$3Q&y~h8uqZs9>RrH~_nm
BPF?^2

diff --git a/src/internet/model/rtt-estimator.cc b/src/internet/model/rtt-estimator.cc
index bcf0f2b3e..d67012344 100644
--- a/src/internet/model/rtt-estimator.cc
+++ b/src/internet/model/rtt-estimator.cc
@@ -279,25 +279,17 @@ void RttMeanDeviation::Measurement (Time m)
 Time RttMeanDeviation::RetransmitTimeout ()
 {
   NS_LOG_FUNCTION (this);
-  // If not enough samples, just return 2 times estimate
-  //if (nSamples < 2) return est * 2;
-  Time retval (Seconds (0));
-  double var = m_variance.ToDouble (Time::S);
-  NS_LOG_DEBUG ("RetransmitTimeout:  var " << var << " est " << m_currentEstimatedRtt.ToDouble (Time::S) << " multiplier " << m_multiplier);
-  if (var < (m_currentEstimatedRtt.ToDouble (Time::S) / 4.0) )
+  NS_LOG_DEBUG ("RetransmitTimeout:  var " << m_variance.GetSeconds () << " est " << m_currentEstimatedRtt.GetSeconds () << " multiplier " << m_multiplier);
+  // RTO = srtt + 4* rttvar
+  int64_t temp = m_currentEstimatedRtt.ToInteger (Time::MS) + 4 * m_variance.ToInteger (Time::MS);
+  if (temp < m_minRto.ToInteger (Time::MS))
     {
-      for (uint16_t i = 0; i < 2* m_multiplier; i++)
-        {
-          retval += m_currentEstimatedRtt;
-        }
-    }
-  else
-    {
-      int64_t temp = m_currentEstimatedRtt.ToInteger (Time::S) + 4 * m_variance.ToInteger (Time::S);
-      retval = Time::FromInteger (temp, Time::S);
-    }
-  NS_LOG_DEBUG ("RetransmitTimeout:  return " << (retval > m_minRto ? retval.GetSeconds () : m_minRto.GetSeconds ()));
-  return (retval > m_minRto ? retval : m_minRto);  // return maximum
+      temp = m_minRto.ToInteger (Time::MS);
+    } 
+  temp = temp * m_multiplier; // Apply backoff
+  Time retval = Time::FromInteger (temp, Time::MS);
+  NS_LOG_DEBUG ("RetransmitTimeout:  return " << retval.GetSeconds ());
+  return (retval);  
 }
 
 Ptr<RttEstimator> RttMeanDeviation::Copy () const