From 235732f6afc598979b5a8d7ce7f433af1e8d8df2 Mon Sep 17 00:00:00 2001
From: Gauri Prasad <gauriprasad@Gauris-MacBook-Pro.local>
Date: Wed, 29 Sep 2021 14:06:47 -0700
Subject: [PATCH] tcp: (fixes #410) Fix TCP Westwood bandwidth estimation bug

---
 src/internet/model/tcp-westwood.cc | 12 ++++++++++--
 src/internet/model/tcp-westwood.h  |  1 +
 2 files changed, 11 insertions(+), 2 deletions(-)

diff --git a/src/internet/model/tcp-westwood.cc b/src/internet/model/tcp-westwood.cc
index 75cb6d906..1e2734e06 100644
--- a/src/internet/model/tcp-westwood.cc
+++ b/src/internet/model/tcp-westwood.cc
@@ -70,7 +70,8 @@ TcpWestwood::TcpWestwood (void) :
   m_lastSampleBW (0),
   m_lastBW (0),
   m_ackedSegments (0),
-  m_IsCount (false)
+  m_IsCount (false),
+  m_lastAck (0)
 {
   NS_LOG_FUNCTION (this);
 }
@@ -131,8 +132,15 @@ TcpWestwood::EstimateBW (const Time &rtt, Ptr<TcpSocketState> tcb)
 
   m_currentBW = m_ackedSegments * tcb->m_segmentSize / rtt.GetSeconds ();
 
-  if (m_pType == TcpWestwood::WESTWOODPLUS)
+  if (m_pType == TcpWestwood::WESTWOOD)
     {
+      Time currentAck = Simulator::Now ();
+      m_currentBW = m_ackedSegments * tcb->m_segmentSize / (currentAck - m_lastAck).GetSeconds ();
+      m_lastAck = currentAck;
+    }
+  else if (m_pType == TcpWestwood::WESTWOODPLUS)
+    {
+      m_currentBW = m_ackedSegments * tcb->m_segmentSize / rtt.GetSeconds ();
       m_IsCount = false;
     }
 
diff --git a/src/internet/model/tcp-westwood.h b/src/internet/model/tcp-westwood.h
index 154e141ca..39a5b9be6 100644
--- a/src/internet/model/tcp-westwood.h
+++ b/src/internet/model/tcp-westwood.h
@@ -133,6 +133,7 @@ protected:
   uint32_t               m_ackedSegments;          //!< The number of segments ACKed between RTTs
   bool                   m_IsCount;                //!< Start keeping track of m_ackedSegments for Westwood+ if TRUE
   EventId                m_bwEstimateEvent;        //!< The BW estimation event for Westwood+
+  Time                   m_lastAck;                //!< The last ACK time
 
 };