From aeb3d27b4dc412f2a2e23c5dee852672bdf58ca1 Mon Sep 17 00:00:00 2001
From: Viyom <viyommittal@gmail.com>
Date: Fri, 11 May 2018 19:30:43 +0200
Subject: [PATCH] tcp: Modularization of Fast Recovery - I

---
 CHANGES.html                            |   4 +-
 src/internet/doc/tcp.rst                |  54 ++++++-
 src/internet/model/tcp-bic.h            |   1 +
 src/internet/model/tcp-congestion-ops.h |   1 +
 src/internet/model/tcp-highspeed.h      |   1 +
 src/internet/model/tcp-htcp.h           |   1 +
 src/internet/model/tcp-hybla.h          |   1 +
 src/internet/model/tcp-illinois.h       |   1 +
 src/internet/model/tcp-l4-protocol.cc   |  14 +-
 src/internet/model/tcp-l4-protocol.h    |   3 +-
 src/internet/model/tcp-ledbat.h         |   1 +
 src/internet/model/tcp-lp.h             |   1 +
 src/internet/model/tcp-recovery-ops.cc  | 124 ++++++++++++++++
 src/internet/model/tcp-recovery-ops.h   | 183 ++++++++++++++++++++++++
 src/internet/model/tcp-scalable.h       |   1 +
 src/internet/model/tcp-socket-base.cc   |  84 +++++++----
 src/internet/model/tcp-socket-base.h    |  29 +++-
 src/internet/model/tcp-vegas.h          |   1 +
 src/internet/model/tcp-veno.h           |   1 +
 src/internet/model/tcp-westwood.h       |   1 +
 src/internet/model/tcp-yeah.h           |   1 +
 src/internet/test/tcp-general-test.cc   |  20 ++-
 src/internet/test/tcp-general-test.h    |  33 +++++
 src/internet/wscript                    |   2 +
 24 files changed, 521 insertions(+), 42 deletions(-)
 create mode 100644 src/internet/model/tcp-recovery-ops.cc
 create mode 100644 src/internet/model/tcp-recovery-ops.h

diff --git a/CHANGES.html b/CHANGES.html
index 02c50fed1..bee376e75 100644
--- a/CHANGES.html
+++ b/CHANGES.html
@@ -63,7 +63,9 @@ nodes to be placed outside of buildings defined in the scenario.</li>
 <h2>Changes to existing API:</h2>
 <ul>
   <li>TrafficControlHelper::Install now only includes root queue discs in the returned
-  QueueDiscContainer.</li>
+    QueueDiscContainer.</li>
+  <li>Recovery algorithms are now in a different class, instead of being tied to TcpSocketBase.
+    Take a look to TcpRecoveryOps for more information.</li>
 </ul>
 <h2>Changes to build system:</h2>
 <ul>
diff --git a/src/internet/doc/tcp.rst b/src/internet/doc/tcp.rst
index e8cafc2fa..93a2e0d2e 100644
--- a/src/internet/doc/tcp.rst
+++ b/src/internet/doc/tcp.rst
@@ -867,11 +867,63 @@ provided by TcpTxBuffer to query the scoreboard; please refer to the Doxygen
 documentation (and to in-code comments) if you want to learn more about this
 implementation.
 
+Loss Recovery Algorithms
+++++++++++++++++++++++++
+The following loss recovery algorithms are supported in ns-3 TCP:
+
+Classic Recovery
+^^^^^^^^^^^^^^^^
+Classic Recovery refers to the combination of NewReno algorithm described in
+RFC 6582 along with SACK based loss recovery algorithm mentioned in RFC 6675.
+SACK based loss recovery is used when sender and receiver support SACK options.
+In the case when SACK options are disabled, the NewReno modification handles
+the recovery.
+
+At the start of recovery phase the congestion window is reduced diffently for
+NewReno and SACK based recovery. For NewReno the reduction is done as given below:
+
+.. math::  cWnd = ssThresh
+
+For SACK based recovery, this is done as follows:
+
+.. math::   cWnd = ssThresh + (dupAckCount * segmentSize)
+
+While in the recovery phase, the congestion window is inflated by segmentSize
+on arrival of every ACK when NewReno is used. The congestion window is kept
+same when SACK based loss recovery is used.
+
+Adding a new loss recovery algorithm in ns-3
+++++++++++++++++++++++++++++++++++++++++++++
+
+Writing (or porting) a loss recovery algorithms from scratch (or from
+other systems) is a process completely separated from the internals of
+TcpSocketBase.
+
+All operations that are delegated to a loss recovery are contained in
+the class TcpRecoveryOps and are given below:
+
+.. code-block:: c++
+
+  virtual std::string GetName () const;
+  virtual void EnterRecovery (Ptr<const TcpSocketState> tcb, uint32_t unAckDataCount,
+                              bool isSackEnabled, uint32_t dupAckCount,
+                              uint32_t bytesInFlight, uint32_t lastDeliveredBytes);
+  virtual void DoRecovery (Ptr<const TcpSocketState> tcb, uint32_t unAckDataCount,
+                           bool isSackEnabled, uint32_t dupAckCount,
+                           uint32_t bytesInFlight, uint32_t lastDeliveredBytes);
+  virtual void ExitRecovery (Ptr<TcpSocketState> tcb, uint32_t bytesInFlight);
+  virtual Ptr<TcpRecoveryOps> Fork ();
+
+EnterRecovery is called when packet loss is detected and recovery is triggered.
+While in recovery phase, each time when an ACK arrives, DoRecovery is called which
+performs the necessary congestion window changes as per the recovery algorithm.
+ExitRecovery is called just prior to exiting recovery phase in order to perform the
+required congestion window ajustments.
+
 Current limitations
 +++++++++++++++++++
 
 * TcpCongestionOps interface does not contain every possible Linux operation
-* Fast retransmit / fast recovery are bound with TcpSocketBase, thereby preventing easy simulation of TCP Tahoe
 
 .. _Writing-tcp-tests:
 
diff --git a/src/internet/model/tcp-bic.h b/src/internet/model/tcp-bic.h
index 4563cf82b..8428a77fd 100644
--- a/src/internet/model/tcp-bic.h
+++ b/src/internet/model/tcp-bic.h
@@ -21,6 +21,7 @@
 #define TCPBIC_H
 
 #include "ns3/tcp-congestion-ops.h"
+#include "ns3/tcp-recovery-ops.h"
 
 class TcpBicIncrementTest;
 class TcpBicDecrementTest;
diff --git a/src/internet/model/tcp-congestion-ops.h b/src/internet/model/tcp-congestion-ops.h
index 4e74d8c2b..10e251a59 100644
--- a/src/internet/model/tcp-congestion-ops.h
+++ b/src/internet/model/tcp-congestion-ops.h
@@ -20,6 +20,7 @@
 #define TCPCONGESTIONOPS_H
 
 #include "ns3/tcp-socket-base.h"
+#include "ns3/tcp-recovery-ops.h"
 
 namespace ns3 {
 
diff --git a/src/internet/model/tcp-highspeed.h b/src/internet/model/tcp-highspeed.h
index 1afb42f89..c65ff3a80 100644
--- a/src/internet/model/tcp-highspeed.h
+++ b/src/internet/model/tcp-highspeed.h
@@ -21,6 +21,7 @@
 #define TCPHIGHSPEED_H
 
 #include "ns3/tcp-congestion-ops.h"
+#include "ns3/tcp-recovery-ops.h"
 
 namespace ns3 {
 
diff --git a/src/internet/model/tcp-htcp.h b/src/internet/model/tcp-htcp.h
index 73388fab1..ea19c31c7 100644
--- a/src/internet/model/tcp-htcp.h
+++ b/src/internet/model/tcp-htcp.h
@@ -28,6 +28,7 @@
 #define TCP_HTCP_H
 
 #include "ns3/tcp-congestion-ops.h"
+#include "ns3/tcp-recovery-ops.h"
 
 namespace ns3 {
 
diff --git a/src/internet/model/tcp-hybla.h b/src/internet/model/tcp-hybla.h
index 9bae424c7..68561679e 100644
--- a/src/internet/model/tcp-hybla.h
+++ b/src/internet/model/tcp-hybla.h
@@ -20,6 +20,7 @@
 #define TCPHYBLA_H
 
 #include "ns3/tcp-congestion-ops.h"
+#include "ns3/tcp-recovery-ops.h"
 #include "ns3/traced-value.h"
 
 namespace ns3 {
diff --git a/src/internet/model/tcp-illinois.h b/src/internet/model/tcp-illinois.h
index 64245a982..90ac5e573 100644
--- a/src/internet/model/tcp-illinois.h
+++ b/src/internet/model/tcp-illinois.h
@@ -29,6 +29,7 @@
 #define TCPILLINOIS_H
 
 #include "ns3/tcp-congestion-ops.h"
+#include "ns3/tcp-recovery-ops.h"
 
 namespace ns3 {
 
diff --git a/src/internet/model/tcp-l4-protocol.cc b/src/internet/model/tcp-l4-protocol.cc
index c31821fb6..ef05a98dc 100644
--- a/src/internet/model/tcp-l4-protocol.cc
+++ b/src/internet/model/tcp-l4-protocol.cc
@@ -42,6 +42,7 @@
 #include "tcp-socket-factory-impl.h"
 #include "tcp-socket-base.h"
 #include "tcp-congestion-ops.h"
+#include "tcp-recovery-ops.h"
 #include "rtt-estimator.h"
 
 #include <vector>
@@ -80,6 +81,11 @@ TcpL4Protocol::GetTypeId (void)
                    TypeIdValue (TcpNewReno::GetTypeId ()),
                    MakeTypeIdAccessor (&TcpL4Protocol::m_congestionTypeId),
                    MakeTypeIdChecker ())
+    .AddAttribute ("RecoveryType",
+                   "Recovery type of TCP objects.",
+                   TypeIdValue (ClassicRecovery::GetTypeId ()),
+                   MakeTypeIdAccessor (&TcpL4Protocol::m_recoveryTypeId),
+                   MakeTypeIdChecker ())
     .AddAttribute ("SocketList", "The list of sockets associated to this protocol.",
                    ObjectVectorValue (),
                    MakeObjectVectorAccessor (&TcpL4Protocol::m_sockets),
@@ -175,22 +181,26 @@ TcpL4Protocol::DoDispose (void)
 }
 
 Ptr<Socket>
-TcpL4Protocol::CreateSocket (TypeId congestionTypeId)
+TcpL4Protocol::CreateSocket (TypeId congestionTypeId, TypeId recoveryTypeId)
 {
   NS_LOG_FUNCTION (this << congestionTypeId.GetName ());
   ObjectFactory rttFactory;
   ObjectFactory congestionAlgorithmFactory;
+  ObjectFactory recoveryAlgorithmFactory;
   rttFactory.SetTypeId (m_rttTypeId);
   congestionAlgorithmFactory.SetTypeId (congestionTypeId);
+  recoveryAlgorithmFactory.SetTypeId (recoveryTypeId);
 
   Ptr<RttEstimator> rtt = rttFactory.Create<RttEstimator> ();
   Ptr<TcpSocketBase> socket = CreateObject<TcpSocketBase> ();
   Ptr<TcpCongestionOps> algo = congestionAlgorithmFactory.Create<TcpCongestionOps> ();
+  Ptr<TcpRecoveryOps> recovery = recoveryAlgorithmFactory.Create<TcpRecoveryOps> ();
 
   socket->SetNode (m_node);
   socket->SetTcp (this);
   socket->SetRtt (rtt);
   socket->SetCongestionControlAlgorithm (algo);
+  socket->SetRecoveryAlgorithm (recovery);
 
   m_sockets.push_back (socket);
   return socket;
@@ -199,7 +209,7 @@ TcpL4Protocol::CreateSocket (TypeId congestionTypeId)
 Ptr<Socket>
 TcpL4Protocol::CreateSocket (void)
 {
-  return CreateSocket (m_congestionTypeId);
+  return CreateSocket (m_congestionTypeId, m_recoveryTypeId);
 }
 
 Ipv4EndPoint *
diff --git a/src/internet/model/tcp-l4-protocol.h b/src/internet/model/tcp-l4-protocol.h
index bbf87b5e9..ad089b107 100644
--- a/src/internet/model/tcp-l4-protocol.h
+++ b/src/internet/model/tcp-l4-protocol.h
@@ -113,7 +113,7 @@ public:
    *
    * \param congestionTypeId the congestion control algorithm TypeId
    */
-  Ptr<Socket> CreateSocket (TypeId congestionTypeId);
+  Ptr<Socket> CreateSocket (TypeId congestionTypeId, TypeId recoveryTypeId);
 
   /**
    * \brief Allocate an IPv4 Endpoint
@@ -306,6 +306,7 @@ private:
   Ipv6EndPointDemux *m_endPoints6; //!< A list of IPv6 end points.
   TypeId m_rttTypeId;              //!< The RTT Estimator TypeId
   TypeId m_congestionTypeId;       //!< The socket TypeId
+  TypeId m_recoveryTypeId;         //!< The recovery TypeId
   std::vector<Ptr<TcpSocketBase> > m_sockets;      //!< list of sockets
   IpL4Protocol::DownTargetCallback m_downTarget;   //!< Callback to send packets over IPv4
   IpL4Protocol::DownTargetCallback6 m_downTarget6; //!< Callback to send packets over IPv6
diff --git a/src/internet/model/tcp-ledbat.h b/src/internet/model/tcp-ledbat.h
index 357026f83..a5458b7e1 100644
--- a/src/internet/model/tcp-ledbat.h
+++ b/src/internet/model/tcp-ledbat.h
@@ -24,6 +24,7 @@
 
 #include <vector>
 #include "ns3/tcp-congestion-ops.h"
+#include "ns3/tcp-recovery-ops.h"
 
 namespace ns3 {
 
diff --git a/src/internet/model/tcp-lp.h b/src/internet/model/tcp-lp.h
index 8924af01f..d15ec17e7 100644
--- a/src/internet/model/tcp-lp.h
+++ b/src/internet/model/tcp-lp.h
@@ -25,6 +25,7 @@
 #define TCPLP_H
 
 #include "ns3/tcp-congestion-ops.h"
+#include "ns3/tcp-recovery-ops.h"
 #include "ns3/traced-value.h"
 
 namespace ns3 {
diff --git a/src/internet/model/tcp-recovery-ops.cc b/src/internet/model/tcp-recovery-ops.cc
new file mode 100644
index 000000000..d3ec83c2d
--- /dev/null
+++ b/src/internet/model/tcp-recovery-ops.cc
@@ -0,0 +1,124 @@
+/* -*- Mode:C++; c-file-style:"gnu"; indent-tabs-mode:nil; -*- */
+/*
+ * Copyright (c) 2018 NITK Surathkal
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation;
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
+ *
+ * Author: Viyom Mittal <viyommittal@gmail.com>
+ *         Vivek Jain <jain.vivek.anand@gmail.com>
+ *         Mohit P. Tahiliani <tahiliani@nitk.edu.in>
+ *
+ */
+#include "tcp-recovery-ops.h"
+#include "tcp-socket-base.h"
+#include "tcp-congestion-ops.h"
+#include "ns3/log.h"
+
+namespace ns3 {
+
+NS_LOG_COMPONENT_DEFINE ("TcpRecoveryOps");
+
+NS_OBJECT_ENSURE_REGISTERED (TcpRecoveryOps);
+
+TypeId
+TcpRecoveryOps::GetTypeId (void)
+{
+  static TypeId tid = TypeId ("ns3::TcpRecoveryOps")
+    .SetParent<Object> ()
+    .SetGroupName ("Internet")
+  ;
+  return tid;
+}
+
+TcpRecoveryOps::TcpRecoveryOps () : Object ()
+{
+}
+
+TcpRecoveryOps::TcpRecoveryOps (const TcpRecoveryOps &other) : Object (other)
+{
+}
+
+TcpRecoveryOps::~TcpRecoveryOps ()
+{
+}
+
+
+// Classic recovery
+
+NS_OBJECT_ENSURE_REGISTERED (ClassicRecovery);
+
+TypeId
+ClassicRecovery::GetTypeId (void)
+{
+  static TypeId tid = TypeId ("ns3::ClassicRecovery")
+    .SetParent<TcpRecoveryOps> ()
+    .SetGroupName ("Internet")
+    .AddConstructor<ClassicRecovery> ()
+  ;
+  return tid;
+}
+
+ClassicRecovery::ClassicRecovery (void) : TcpRecoveryOps ()
+{
+  NS_LOG_FUNCTION (this);
+}
+
+ClassicRecovery::ClassicRecovery (const ClassicRecovery& sock)
+  : TcpRecoveryOps (sock)
+{
+  NS_LOG_FUNCTION (this);
+}
+
+ClassicRecovery::~ClassicRecovery (void)
+{
+}
+
+void
+ClassicRecovery::EnterRecovery (Ptr<TcpSocketState> tcb, uint32_t dupAckCount)
+{
+  tcb->m_cWnd = tcb->m_ssThresh;
+  tcb->m_cWndInfl = tcb->m_ssThresh + (dupAckCount * tcb->m_segmentSize);
+}
+
+void
+ClassicRecovery::DoRecovery (Ptr<TcpSocketState> tcb)
+{
+  tcb->m_cWndInfl += tcb->m_segmentSize;
+}
+
+void
+ClassicRecovery::ExitRecovery (Ptr<TcpSocketState> tcb)
+{
+  // Follow NewReno procedures to exit FR if SACK is disabled
+  // (RFC2582 sec.3 bullet #5 paragraph 2, option 2)
+  // For SACK connections, we maintain the cwnd = ssthresh. In fact,
+  // this ACK was received in RECOVERY phase, not in OPEN. So we
+  // are not allowed to increase the window
+  tcb->m_cWndInfl = tcb->m_ssThresh.Get ();
+}
+
+std::string
+ClassicRecovery::GetName () const
+{
+  return "ClassicRecovery";
+}
+
+Ptr<TcpRecoveryOps>
+ClassicRecovery::Fork ()
+{
+  return CopyObject<ClassicRecovery> (this);
+}
+
+} // namespace ns3
+
diff --git a/src/internet/model/tcp-recovery-ops.h b/src/internet/model/tcp-recovery-ops.h
new file mode 100644
index 000000000..885c2df78
--- /dev/null
+++ b/src/internet/model/tcp-recovery-ops.h
@@ -0,0 +1,183 @@
+/* -*- Mode:C++; c-file-style:"gnu"; indent-tabs-mode:nil; -*- */
+/*
+ * Copyright (c) 2018 NITK Surathkal
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation;
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
+ *
+ * Author: Viyom Mittal <viyommittal@gmail.com>
+ *         Vivek Jain <jain.vivek.anand@gmail.com>
+ *         Mohit P. Tahiliani <tahiliani@nitk.edu.in>
+ *
+ */
+#ifndef TCPRECOVERYOPS_H
+#define TCPRECOVERYOPS_H
+
+#include "ns3/tcp-socket-base.h"
+
+namespace ns3 {
+
+/**
+ * \ingroup tcp
+ * \defgroup recoveryOps Recovery Algorithms.
+ *
+ * The various recovery algorithms used in recovery phase of TCP.
+ */
+
+/**
+ * \ingroup recoveryOps
+ *
+ * \brief recovery abstract class
+ *
+ * The design is inspired by the TcpCongestionOps class in ns-3. The fast
+ * recovery is splitted from the main socket code, and it is a pluggable
+ * component. An interface has been defined; variables are maintained in the
+ * TcpSocketState class, while subclasses of TcpRecoveryOps operate over an
+ * instance of that class.
+ *
+ * \see DoRecovery
+ */
+class TcpRecoveryOps : public Object
+{
+public:
+  /**
+   * \brief Get the type ID.
+   * \return the object TypeId
+   */
+  static TypeId GetTypeId (void);
+
+  /**
+   * \brief Constructor
+   */
+  TcpRecoveryOps ();
+
+  /**
+   * \brief Copy constructor.
+   * \param other object to copy.
+   */
+  TcpRecoveryOps (const TcpRecoveryOps &other);
+
+  /**
+   * \brief Deconstructor
+   */
+  virtual ~TcpRecoveryOps ();
+
+  /**
+   * \brief Get the name of the recovery algorithm
+   *
+   * \return A string identifying the name
+   */
+  virtual std::string GetName () const = 0;
+
+  /**
+   * \brief Performs variable initialization at the start of recovery
+   *
+   * The function is called when the TcpSocketState is changed to CA_RECOVERY.
+   *
+   * \param tcb internal congestion state
+   * \param dupAckCount duplicate acknowldgement count
+   */
+  virtual void EnterRecovery (Ptr<TcpSocketState> tcb, uint32_t dupAckCount)
+  {
+    NS_UNUSED (tcb);
+    NS_UNUSED (dupAckCount);
+  }
+
+  /**
+   * \brief Performs recovery based on the recovery algorithm
+   *
+   * The function is called on arrival of every ack when TcpSocketState
+   * is set to CA_RECOVERY. It performs the necessary cwnd changes
+   * as per the recovery algorithm.
+   *
+   * \param tcb internal congestion state
+   */
+  virtual void DoRecovery (Ptr<TcpSocketState> tcb)
+  {
+    NS_UNUSED (tcb);
+  }
+
+  /**
+   * \brief Performs cwnd adjustments at the end of recovery
+   *
+   * The function is called when the TcpSocketState is changed from CA_RECOVERY.
+   *
+   * \param tcb internal congestion state
+   * \param isSackEnabled
+   */
+  virtual void ExitRecovery (Ptr<TcpSocketState> tcb)
+  {
+    NS_UNUSED (tcb);
+  }
+
+  /**
+   * \brief Copy the recovery algorithm across socket
+   *
+   * \return a pointer of the copied object
+   */
+  virtual Ptr<TcpRecoveryOps> Fork () = 0;
+};
+
+/**
+ * \brief The Classic recovery implementation
+ *
+ * Classic recovery refers to the two well-established recovery algorithms,
+ * namely, NewReno (RFC 6582) and SACK based recovery (RFC 6675).
+ *
+ * The idea of the algorithm is that when we enter recovery, we set the
+ * congestion window value to the slow start threshold and maintain it
+ * at such value until we are fully recovered (in other words, until
+ * the highest sequence transmitted at time of detecting the loss is
+ * ACKed by the receiver).
+ *
+ * \see DoRecovery
+ */
+class ClassicRecovery : public TcpRecoveryOps
+{
+public:
+  /**
+   * \brief Get the type ID.
+   * \return the object TypeId
+   */
+  static TypeId GetTypeId (void);
+
+  /**
+   * \brief Constructor
+   */
+  ClassicRecovery ();
+
+  /**
+   * \brief Copy constructor.
+   * \param recovery object to copy.
+   */
+  ClassicRecovery (const ClassicRecovery& recovery);
+
+  /**
+   * \brief Constructor
+   */
+  ~ClassicRecovery ();
+
+  virtual std::string GetName () const override;
+
+  virtual void EnterRecovery (Ptr<TcpSocketState> tcb, uint32_t dupAckCount) override;
+
+  virtual void DoRecovery (Ptr<TcpSocketState> tcb) override;
+
+  virtual void ExitRecovery (Ptr<TcpSocketState> tcb) override;
+
+  virtual Ptr<TcpRecoveryOps> Fork () override;
+};
+
+} // namespace ns3
+
+#endif // TCPRECOVERYOPS_H
diff --git a/src/internet/model/tcp-scalable.h b/src/internet/model/tcp-scalable.h
index 6edea9f29..bda66ed0e 100644
--- a/src/internet/model/tcp-scalable.h
+++ b/src/internet/model/tcp-scalable.h
@@ -31,6 +31,7 @@
 #define TCPSCALABLE_H
 
 #include "ns3/tcp-congestion-ops.h"
+#include "ns3/tcp-recovery-ops.h"
 
 namespace ns3 {
 
diff --git a/src/internet/model/tcp-socket-base.cc b/src/internet/model/tcp-socket-base.cc
index 2f21b7636..a2363e76a 100644
--- a/src/internet/model/tcp-socket-base.cc
+++ b/src/internet/model/tcp-socket-base.cc
@@ -54,6 +54,7 @@
 #include "tcp-option-sack-permitted.h"
 #include "tcp-option-sack.h"
 #include "tcp-congestion-ops.h"
+#include "tcp-recovery-ops.h"
 
 #include <math.h>
 #include <algorithm>
@@ -187,7 +188,7 @@ TcpSocketBase::GetTypeId (void)
                      "ns3::TracedValueCallback::Uint32")
     .AddTraceSource ("CongestionWindowInflated",
                      "The TCP connection's congestion window inflates as in older RFC",
-                     MakeTraceSourceAccessor (&TcpSocketBase::m_cWndInfl),
+                     MakeTraceSourceAccessor (&TcpSocketBase::m_cWndInflTrace),
                      "ns3::TracedValueCallback::Uint32")
     .AddTraceSource ("SlowStartThreshold",
                      "TCP slow start threshold (bytes)",
@@ -232,6 +233,10 @@ TcpSocketState::GetTypeId (void)
                      "The TCP connection's congestion window",
                      MakeTraceSourceAccessor (&TcpSocketState::m_cWnd),
                      "ns3::TracedValue::Uint32Callback")
+    .AddTraceSource ("CongestionWindowInflated",
+                     "The TCP connection's inflated congestion window",
+                     MakeTraceSourceAccessor (&TcpSocketState::m_cWndInfl),
+                     "ns3::TracedValue::Uint32Callback")
     .AddTraceSource ("SlowStartThreshold",
                      "TCP slow start threshold (bytes)",
                      MakeTraceSourceAccessor (&TcpSocketState::m_ssThresh),
@@ -305,6 +310,10 @@ TcpSocketBase::TcpSocketBase (void)
                                           MakeCallback (&TcpSocketBase::UpdateCwnd, this));
   NS_ASSERT (ok == true);
 
+  ok = m_tcb->TraceConnectWithoutContext ("CongestionWindowInflated",
+                                          MakeCallback (&TcpSocketBase::UpdateCwndInfl, this));
+  NS_ASSERT (ok == true);
+
   ok = m_tcb->TraceConnectWithoutContext ("SlowStartThreshold",
                                           MakeCallback (&TcpSocketBase::UpdateSsThresh, this));
   NS_ASSERT (ok == true);
@@ -405,12 +414,21 @@ TcpSocketBase::TcpSocketBase (const TcpSocketBase& sock)
       m_congestionControl = sock.m_congestionControl->Fork ();
     }
 
+  if (sock.m_recoveryOps)
+    {
+      m_recoveryOps = sock.m_recoveryOps->Fork ();
+    }
+
   bool ok;
 
   ok = m_tcb->TraceConnectWithoutContext ("CongestionWindow",
                                           MakeCallback (&TcpSocketBase::UpdateCwnd, this));
   NS_ASSERT (ok == true);
 
+  ok = m_tcb->TraceConnectWithoutContext ("CongestionWindowInflated",
+                                          MakeCallback (&TcpSocketBase::UpdateCwndInfl, this));
+  NS_ASSERT (ok == true);
+
   ok = m_tcb->TraceConnectWithoutContext ("SlowStartThreshold",
                                           MakeCallback (&TcpSocketBase::UpdateSsThresh, this));
   NS_ASSERT (ok == true);
@@ -1250,7 +1268,7 @@ TcpSocketBase::DoForwardUp (Ptr<Packet> packet, const Address &fromAddress,
 
       // Initialize cWnd and ssThresh
       m_tcb->m_cWnd = GetInitialCwnd () * GetSegSize ();
-      m_cWndInfl = m_tcb->m_cWnd;
+      m_tcb->m_cWndInfl = m_tcb->m_cWnd;
       m_tcb->m_ssThresh = GetInitialSSThresh ();
 
       if (tcpHeader.GetFlags () & TcpHeader::ACK)
@@ -1489,7 +1507,7 @@ TcpSocketBase::EnterRecovery ()
     }
   else
     {
-      if (! m_txBuffer->IsLost (m_txBuffer->HeadSequence ()))
+      if (!m_txBuffer->IsLost (m_txBuffer->HeadSequence ()))
         {
           // We received 3 dupacks, but the head is not marked as lost
           // (received less than 3 SACK block ahead).
@@ -1511,8 +1529,7 @@ TcpSocketBase::EnterRecovery ()
   // compatibility with old ns-3 versions
   uint32_t bytesInFlight = m_sackEnabled ? BytesInFlight () : BytesInFlight () + m_tcb->m_segmentSize;
   m_tcb->m_ssThresh = m_congestionControl->GetSsThresh (m_tcb, bytesInFlight);
-  m_tcb->m_cWnd = m_tcb->m_ssThresh;
-  m_cWndInfl = m_tcb->m_ssThresh + m_dupAckCount * m_tcb->m_segmentSize;
+  m_recoveryOps->EnterRecovery (m_tcb, m_dupAckCount);
 
   NS_LOG_INFO (m_dupAckCount << " dupack. Enter fast recovery mode." <<
                "Reset cwnd to " << m_tcb->m_cWnd << ", ssthresh to " <<
@@ -1550,15 +1567,6 @@ TcpSocketBase::DupAck ()
       ++m_dupAckCount;
     }
 
-  if (!m_sackEnabled && m_tcb->m_congState == TcpSocketState::CA_RECOVERY)
-    {
-      // If we are in recovery and we receive a dupack, one segment
-      // has left the network. This is equivalent to a SACK of one block.
-      m_txBuffer->AddRenoSack ();
-
-      m_cWndInfl += m_tcb->m_segmentSize;
-    }
-
   if (m_tcb->m_congState == TcpSocketState::CA_OPEN)
     {
       // From Open we go Disorder
@@ -1571,7 +1579,19 @@ TcpSocketBase::DupAck ()
       NS_LOG_DEBUG ("CA_OPEN -> CA_DISORDER");
     }
 
-  if (m_tcb->m_congState == TcpSocketState::CA_DISORDER)
+  if (m_tcb->m_congState == TcpSocketState::CA_RECOVERY)
+    {
+      if (!m_sackEnabled)
+        {
+          // If we are in recovery and we receive a dupack, one segment
+          // has left the network. This is equivalent to a SACK of one block.
+          m_txBuffer->AddRenoSack ();
+        }
+      m_recoveryOps->DoRecovery (m_tcb);
+      NS_LOG_INFO (m_dupAckCount << " Dupack received in fast recovery mode."
+                   "Increase cwnd to " << m_tcb->m_cWnd);
+    }
+  else if (m_tcb->m_congState == TcpSocketState::CA_DISORDER)
     {
       // RFC 6675, Section 5, continuing:
       // ... and take the following steps:
@@ -1674,9 +1694,9 @@ TcpSocketBase::ProcessAck (const SequenceNumber32 &ackNumber, bool scoreboardUpd
    */
 
   bool isDupack = m_sackEnabled ?
-        scoreboardUpdated
-      : ackNumber == oldHeadSequence &&
-        ackNumber < m_tcb->m_highTxMark;
+    scoreboardUpdated
+    : ackNumber == oldHeadSequence &&
+    ackNumber < m_tcb->m_highTxMark;
 
   NS_LOG_DEBUG ("ACK of " << ackNumber <<
                 " SND.UNA=" << oldHeadSequence <<
@@ -1767,10 +1787,10 @@ TcpSocketBase::ProcessAck (const SequenceNumber32 &ackNumber, bool scoreboardUpd
               m_txBuffer->DeleteRetransmittedFlagFromHead ();
             }
           DoRetransmit (); // Assume the next seq is lost. Retransmit lost packet
-          m_cWndInfl = SafeSubtraction (m_cWndInfl, bytesAcked);
+          m_tcb->m_cWndInfl = SafeSubtraction (m_tcb->m_cWndInfl, bytesAcked);
           if (segsAcked >= 1)
             {
-              m_cWndInfl += m_tcb->m_segmentSize;
+              m_recoveryOps->DoRecovery (m_tcb);
             }
 
           // This partial ACK acknowledge the fact that one segment has been
@@ -1891,12 +1911,7 @@ TcpSocketBase::ProcessAck (const SequenceNumber32 &ackNumber, bool scoreboardUpd
           if (exitedFastRecovery)
             {
               NewAck (ackNumber, true);
-              // Follow NewReno procedures to exit FR if SACK is disabled
-              // (RFC2582 sec.3 bullet #5 paragraph 2, option 2)
-              m_cWndInfl = m_tcb->m_ssThresh.Get ();
-              // For SACK connections, we maintain the cwnd = ssthresh. In fact,
-              // this ACK was received in RECOVERY phase, not in OPEN. So we
-              // are not allowed to increase the window
+              m_recoveryOps->ExitRecovery (m_tcb);
               NS_LOG_DEBUG ("Leaving Fast Recovery; BytesInFlight() = " <<
                             BytesInFlight () << "; cWnd = " << m_tcb->m_cWnd);
             }
@@ -1904,7 +1919,7 @@ TcpSocketBase::ProcessAck (const SequenceNumber32 &ackNumber, bool scoreboardUpd
             {
               m_congestionControl->IncreaseWindow (m_tcb, segsAcked);
 
-              m_cWndInfl = m_tcb->m_cWnd;
+              m_tcb->m_cWndInfl = m_tcb->m_cWnd;
 
               NS_LOG_LOGIC ("Congestion control called: " <<
                             " cWnd: " << m_tcb->m_cWnd <<
@@ -3306,7 +3321,7 @@ TcpSocketBase::ReTxTimeout ()
 
   // Cwnd set to 1 MSS
   m_tcb->m_cWnd = m_tcb->m_segmentSize;
-  m_cWndInfl = m_tcb->m_cWnd;
+  m_tcb->m_cWndInfl = m_tcb->m_cWnd;
   m_congestionControl->CwndEvent (m_tcb, TcpSocketState::CA_EVENT_LOSS);
   m_congestionControl->CongestionStateSet (m_tcb, TcpSocketState::CA_LOSS);
   m_tcb->m_congState = TcpSocketState::CA_LOSS;
@@ -3891,6 +3906,12 @@ TcpSocketBase::UpdateCwnd (uint32_t oldValue, uint32_t newValue)
   m_cWndTrace (oldValue, newValue);
 }
 
+void
+TcpSocketBase::UpdateCwndInfl (uint32_t oldValue, uint32_t newValue)
+{
+  m_cWndInflTrace (oldValue, newValue);
+}
+
 void
 TcpSocketBase::UpdateSsThresh (uint32_t oldValue, uint32_t newValue)
 {
@@ -3937,6 +3958,13 @@ TcpSocketBase::SetCongestionControlAlgorithm (Ptr<TcpCongestionOps> algo)
   m_congestionControl = algo;
 }
 
+void
+TcpSocketBase::SetRecoveryAlgorithm (Ptr<TcpRecoveryOps> recovery)
+{
+  NS_LOG_FUNCTION (this << recovery);
+  m_recoveryOps = recovery;
+}
+
 Ptr<TcpSocketBase>
 TcpSocketBase::Fork (void)
 {
diff --git a/src/internet/model/tcp-socket-base.h b/src/internet/model/tcp-socket-base.h
index ee1abdbe4..6ac18e80f 100644
--- a/src/internet/model/tcp-socket-base.h
+++ b/src/internet/model/tcp-socket-base.h
@@ -45,6 +45,7 @@ class Packet;
 class TcpL4Protocol;
 class TcpHeader;
 class TcpCongestionOps;
+class TcpRecoveryOps;
 class RttEstimator;
 class TcpRxBuffer;
 class TcpTxBuffer;
@@ -170,6 +171,7 @@ public:
 
   // Congestion control
   TracedValue<uint32_t>  m_cWnd             {0}; //!< Congestion window
+  TracedValue<uint32_t>  m_cWndInfl         {0}; //!< Inflated congestion window trace (used only for backward compatibility purpose)
   TracedValue<uint32_t>  m_ssThresh         {0}; //!< Slow start threshold
   uint32_t               m_initialCWnd      {0}; //!< Initial cWnd value
   uint32_t               m_initialSsThresh  {0}; //!< Initial Slow Start Threshold value
@@ -459,6 +461,11 @@ public:
    */
   TracedCallback<uint32_t, uint32_t> m_cWndTrace;
 
+  /**
+   * \brief Callback pointer for cWndInfl trace chaining
+   */
+  TracedCallback<uint32_t, uint32_t> m_cWndInflTrace;
+
   /**
    * \brief Callback pointer for ssTh trace chaining
    */
@@ -496,6 +503,13 @@ public:
    */
   void UpdateCwnd (uint32_t oldValue, uint32_t newValue);
 
+  /**
+   * \brief Callback function to hook to TcpSocketState inflated congestion window
+   * \param oldValue old cWndInfl value
+   * \param newValue new cWndInfl value
+   */
+  void UpdateCwndInfl (uint32_t oldValue, uint32_t newValue);
+
   /**
    * \brief Callback function to hook to TcpSocketState slow start threshold
    * \param oldValue old ssTh value
@@ -546,6 +560,13 @@ public:
    */
   void SetCongestionControlAlgorithm (Ptr<TcpCongestionOps> algo);
 
+  /**
+   * \brief Install a recovery algorithm on this socket
+   *
+   * \param recovery Algorithm to be installed
+   */
+  void SetRecoveryAlgorithm (Ptr<TcpRecoveryOps> recovery);
+
   // Necessary implementations of null functions from ns3::Socket
   virtual enum SocketErrno GetErrno (void) const;    // returns m_errno
   virtual enum SocketType GetSocketType (void) const; // returns socket type
@@ -1046,7 +1067,7 @@ protected:
   void AddOptions (TcpHeader& tcpHeader);
 
   /**
-   * \brief Read TCP options begore Ack processing
+   * \brief Read TCP options before Ack processing
    *
    * Timestamp and Window scale are managed in other pieces of code.
    *
@@ -1252,6 +1273,7 @@ protected:
   // Transmission Control Block
   Ptr<TcpSocketState>    m_tcb {nullptr};               //!< Congestion control informations
   Ptr<TcpCongestionOps>  m_congestionControl {nullptr}; //!< Congestion control
+  Ptr<TcpRecoveryOps>    m_recoveryOps {nullptr};       //!< Recovery Algorithm
 
   // Guesses over the other connection end
   bool m_isFirstPartialAck {true}; //!< First partial ACK during RECOVERY
@@ -1265,11 +1287,6 @@ protected:
 
   // Pacing related variable
   Timer m_pacingTimer {Timer::REMOVE_ON_DESTROY}; //!< Pacing Event
-
-  /**
-   * \brief Inflated congestion window trace (not used in the real code, deprecated)
-   */
-  TracedValue<uint32_t> m_cWndInfl {0};
 };
 
 /**
diff --git a/src/internet/model/tcp-vegas.h b/src/internet/model/tcp-vegas.h
index a3d160aac..d092af0ab 100644
--- a/src/internet/model/tcp-vegas.h
+++ b/src/internet/model/tcp-vegas.h
@@ -28,6 +28,7 @@
 #define TCPVEGAS_H
 
 #include "ns3/tcp-congestion-ops.h"
+#include "ns3/tcp-recovery-ops.h"
 
 namespace ns3 {
 
diff --git a/src/internet/model/tcp-veno.h b/src/internet/model/tcp-veno.h
index 39d46ed6f..dbd76ad79 100644
--- a/src/internet/model/tcp-veno.h
+++ b/src/internet/model/tcp-veno.h
@@ -28,6 +28,7 @@
 #define TCPVENO_H
 
 #include "ns3/tcp-congestion-ops.h"
+#include "ns3/tcp-recovery-ops.h"
 
 namespace ns3 {
 
diff --git a/src/internet/model/tcp-westwood.h b/src/internet/model/tcp-westwood.h
index 4601c451e..19ae151fe 100644
--- a/src/internet/model/tcp-westwood.h
+++ b/src/internet/model/tcp-westwood.h
@@ -34,6 +34,7 @@
 #define TCP_WESTWOOD_H
 
 #include "tcp-congestion-ops.h"
+#include "ns3/tcp-recovery-ops.h"
 #include "ns3/sequence-number.h"
 #include "ns3/traced-value.h"
 
diff --git a/src/internet/model/tcp-yeah.h b/src/internet/model/tcp-yeah.h
index 762fdfa39..202d4b6bc 100644
--- a/src/internet/model/tcp-yeah.h
+++ b/src/internet/model/tcp-yeah.h
@@ -28,6 +28,7 @@
 #define TCPYEAH_H
 
 #include "ns3/tcp-scalable.h"
+#include "ns3/tcp-recovery-ops.h"
 
 namespace ns3 {
 
diff --git a/src/internet/test/tcp-general-test.cc b/src/internet/test/tcp-general-test.cc
index a69f1c00e..b678ed1f1 100644
--- a/src/internet/test/tcp-general-test.cc
+++ b/src/internet/test/tcp-general-test.cc
@@ -37,6 +37,7 @@ NS_LOG_COMPONENT_DEFINE ("TcpGeneralTest");
 TcpGeneralTest::TcpGeneralTest (const std::string &desc)
   : TestCase (desc),
     m_congControlTypeId (TcpNewReno::GetTypeId ()),
+    m_recoveryTypeId (ClassicRecovery::GetTypeId ()),
     m_remoteAddr (Ipv4Address::GetAny (), 4477)
 {
   NS_LOG_FUNCTION (this << desc);
@@ -96,6 +97,7 @@ TcpGeneralTest::ConfigureEnvironment ()
   NS_LOG_FUNCTION (this);
 
   SetCongestionControl (m_congControlTypeId);
+  SetRecoveryAlgorithm (m_recoveryTypeId);
   SetPropagationDelay (MilliSeconds (500));
   SetTransmitStart (Seconds (10));
   SetAppPktSize (500);
@@ -197,6 +199,8 @@ TcpGeneralTest::DoRun (void)
   m_senderSocket->SetUpdateRttHistoryCb (MakeCallback (&TcpGeneralTest::UpdateRttHistoryCb, this));
   m_senderSocket->TraceConnectWithoutContext ("CongestionWindow",
                                               MakeCallback (&TcpGeneralTest::CWndTrace, this));
+  m_senderSocket->TraceConnectWithoutContext ("CongestionWindowInflated",
+                                              MakeCallback (&TcpGeneralTest::CWndInflTrace, this));
   m_senderSocket->TraceConnectWithoutContext ("SlowStartThreshold",
                                               MakeCallback (&TcpGeneralTest::SsThreshTrace, this));
   m_senderSocket->TraceConnectWithoutContext ("CongState",
@@ -264,24 +268,34 @@ TcpGeneralTest::CreateChannel ()
 Ptr<TcpSocketMsgBase>
 TcpGeneralTest::CreateSocket (Ptr<Node> node, TypeId socketType,
                               TypeId congControl)
+{
+  return CreateSocket (node, socketType, congControl, m_recoveryTypeId);
+}
+
+Ptr<TcpSocketMsgBase>
+TcpGeneralTest::CreateSocket (Ptr<Node> node, TypeId socketType,
+                              TypeId congControl, TypeId recoveryAlgorithm)
 {
   ObjectFactory rttFactory;
   ObjectFactory congestionAlgorithmFactory;
+  ObjectFactory recoveryAlgorithmFactory;
   ObjectFactory socketFactory;
 
   rttFactory.SetTypeId (RttMeanDeviation::GetTypeId ());
   congestionAlgorithmFactory.SetTypeId (congControl);
+  recoveryAlgorithmFactory.SetTypeId (recoveryAlgorithm);
   socketFactory.SetTypeId (socketType);
 
   Ptr<RttEstimator> rtt = rttFactory.Create<RttEstimator> ();
   Ptr<TcpSocketMsgBase> socket = DynamicCast<TcpSocketMsgBase> (socketFactory.Create ());
   Ptr<TcpCongestionOps> algo = congestionAlgorithmFactory.Create<TcpCongestionOps> ();
+  Ptr<TcpRecoveryOps> recovery = recoveryAlgorithmFactory.Create<TcpRecoveryOps> ();
 
   socket->SetNode (node);
   socket->SetTcp (node->GetObject<TcpL4Protocol> ());
   socket->SetRtt (rtt);
   socket->SetCongestionControlAlgorithm (algo);
-
+  socket->SetRecoveryAlgorithm (recovery);
   return socket;
 }
 
@@ -300,13 +314,13 @@ TcpGeneralTest::CreateReceiverErrorModel ()
 Ptr<TcpSocketMsgBase>
 TcpGeneralTest::CreateSenderSocket (Ptr<Node> node)
 {
-  return CreateSocket (node, TcpSocketMsgBase::GetTypeId (), m_congControlTypeId);
+  return CreateSocket (node, TcpSocketMsgBase::GetTypeId (), m_congControlTypeId, m_recoveryTypeId);
 }
 
 Ptr<TcpSocketMsgBase>
 TcpGeneralTest::CreateReceiverSocket (Ptr<Node> node)
 {
-  return CreateSocket (node, TcpSocketMsgBase::GetTypeId (), m_congControlTypeId);
+  return CreateSocket (node, TcpSocketMsgBase::GetTypeId (), m_congControlTypeId, m_recoveryTypeId);
 }
 
 void
diff --git a/src/internet/test/tcp-general-test.h b/src/internet/test/tcp-general-test.h
index 7b5007c52..9a338b369 100644
--- a/src/internet/test/tcp-general-test.h
+++ b/src/internet/test/tcp-general-test.h
@@ -23,6 +23,7 @@
 #include "ns3/error-model.h"
 #include "ns3/tcp-socket-base.h"
 #include "ns3/tcp-congestion-ops.h"
+#include "ns3/tcp-recovery-ops.h"
 #include "ns3/test.h"
 
 namespace ns3 {
@@ -322,6 +323,18 @@ protected:
   virtual Ptr<TcpSocketMsgBase> CreateSocket (Ptr<Node> node, TypeId socketType,
                                               TypeId congControl);
 
+  /**
+   * \brief Create a socket
+   *
+   * \param node associated node
+   * \param socketType Type of the TCP socket
+   * \param congControl congestion control
+   * \param recoveryAlgorithm recovery algorithm
+   * \return a pointer to the newer created socket
+   */
+  virtual Ptr<TcpSocketMsgBase> CreateSocket (Ptr<Node> node, TypeId socketType,
+                                              TypeId congControl, TypeId recoveryAlgorithm);
+
   /**
    * \brief Get the pointer to a previously created sender socket
    * \return ptr to sender socket or 0
@@ -623,6 +636,13 @@ protected:
    */
   void SetCongestionControl (TypeId congControl) { m_congControlTypeId = congControl; }
 
+  /**
+   * \brief recovery algorithm of the sender socket
+   *
+   * \param recovery typeid of the recovery algorithm
+   */
+  void SetRecoveryAlgorithm (TypeId reccovery) { m_recoveryTypeId = reccovery; }
+
   /**
    * \brief MTU of the bottleneck link
    *
@@ -654,6 +674,18 @@ protected:
     NS_UNUSED (newValue);
   }
 
+  /**
+   * \brief Tracks the inflated congestion window changes
+   *
+   * \param oldValue old value
+   * \param newValue new value
+   */
+  virtual void CWndInflTrace (uint32_t oldValue, uint32_t newValue)
+  {
+    NS_UNUSED (oldValue);
+    NS_UNUSED (newValue);
+  }
+
   /**
    * \brief Rtt changes
    *
@@ -943,6 +975,7 @@ protected:
   }
 
   TypeId   m_congControlTypeId;      //!< Congestion control
+  TypeId   m_recoveryTypeId;         //!< Recovery
 
 private:
   // Member variables, accessible through getters
diff --git a/src/internet/wscript b/src/internet/wscript
index 4c6644f40..e5ef3d98d 100644
--- a/src/internet/wscript
+++ b/src/internet/wscript
@@ -179,6 +179,7 @@ def build(bld):
         'model/udp-socket-factory.cc',
         'model/tcp-socket.cc',
         'model/tcp-socket-factory.cc',
+        'model/tcp-recovery-ops.cc',
         'model/ipv4.cc',
         'model/ipv4-raw-socket-factory.cc',
         'model/ipv6-header.cc',
@@ -389,6 +390,7 @@ def build(bld):
         'model/tcp-socket-base.h',
         'model/tcp-tx-buffer.h',
         'model/tcp-rx-buffer.h',
+        'model/tcp-recovery-ops.h',
         'model/rtt-estimator.h',
         'model/ipv4-packet-probe.h',
         'model/ipv6-packet-probe.h',