From d6f671e834258e65c654d565a7069c8a2e1b98e7 Mon Sep 17 00:00:00 2001
From: Andrea Lupia <alupia@dimes.unical.it>
Date: Sat, 10 Sep 2016 01:52:53 +0200
Subject: [PATCH] aodv: (fixes #2123) AODV doesn't use / honor IP TTL in the
 RREQ / RREP

---
 CHANGES.html                            |  58 ++++++++--
 RELEASE_NOTES                           |   2 +
 src/aodv/model/aodv-routing-protocol.cc | 141 +++++++++++++++++++++---
 src/aodv/model/aodv-routing-protocol.h  |  10 +-
 4 files changed, 183 insertions(+), 28 deletions(-)

diff --git a/CHANGES.html b/CHANGES.html
index 1fb8dafb7..032ac25dd 100644
--- a/CHANGES.html
+++ b/CHANGES.html
@@ -73,13 +73,20 @@ us a note on ns-developers mailing list.</p>
     See the pfifo_fast queue disc section of the Traffic Control Layer model
     for more information.
 </li>
-<li> A new class <b>SpectrumWifiPhy</b> has been introduced that makes use of the Spectrum module.  Its functionality and API is currently very similar to that of the YansWifiPhy, especially because it reuses the same InterferenceHelper and ErrorModel classes (for this release).  Some example programs in the 'examples/wireless/' directory, such as 'wifi-spectrum-per-example.cc', illustrate how the SpectrumWifiPhy class can be substituted for the default YansWifiPhy PHY model.
+<li>A new class <b>SpectrumWifiPhy</b> has been introduced that makes use of the 
+    Spectrum module.  Its functionality and API is currently very similar to that 
+    of the YansWifiPhy, especially because it reuses the same InterferenceHelper 
+    and ErrorModel classes (for this release).  Some example programs in the 
+    'examples/wireless/' directory, such as 'wifi-spectrum-per-example.cc', 
+    illustrate how the SpectrumWifiPhy class can be substituted for the default 
+    YansWifiPhy PHY model.
+</li>
+<li>We have added support for generating traces for the
+    <a href="https://wilseypa.github.io/desMetrics">DES Metrics</a> project.
+    These can be enabled by adding <tt>--enable-des-metrics</tt> at configuration;
+    you must also use <tt>CommandLine</tt> in your script.  See the API docs
+    for class <tt>DesMetrics</tt> for more details.
 </li>
-<li> We have added support for generating traces for the
-<a href="https://wilseypa.github.io/desMetrics/>DES Metrics</a> project.
-These can be enabled by adding <tt>--enable-des-metrics</tt> at configuration;
-you must also use <tt>CommandLine</tt> in your script.  See the API docs
-for class <tt>DesMetrics</tt> for more details.
 </ul>
 <h2>Changes to existing API:</h2>
 <ul>
@@ -100,10 +107,32 @@ for class <tt>DesMetrics</tt> for more details.
 </li>
 <li>The QosTag is removed as it has been superseded by the SocketPriorityTag.</li>
 <li>The Ipv4L3Protocol::DefaultTos attribute is removed.</li>
-<li>The attributes YansWifiPhy::Frequency, YansWifiPhy::ChannelNumber, and YansWifiPhy::ChannelWidth, and the related accessor methods, were moved to base class WifiPhy.  YansWifiPhy::GetChannelFrequencyMhz() was deleted.  A new method WifiPhy::DefineChannelNumber () was added to allow users to define relationships between channel number, standard, frequency, and channel width.
+<li>The attributes YansWifiPhy::Frequency, YansWifiPhy::ChannelNumber, and 
+    YansWifiPhy::ChannelWidth, and the related accessor methods, were moved to 
+    base class WifiPhy.  YansWifiPhy::GetChannelFrequencyMhz() was deleted.  
+    A new method WifiPhy::DefineChannelNumber () was added to allow users to 
+    define relationships between channel number, standard, frequency, and channel width.
+</li>
+<li>The class <b>WifiSpectrumValueHelper</b> has been refactored; previously it 
+    was an abstract base class supporting the WifiSpectrumValue5MhzFactory spectrum 
+    model.  It now contains various static member methods supporting the creation 
+    of power spectral densities with the granularity of a Wi-Fi OFDM subcarrier 
+    bandwidth.  The class WifiSpectrumValue5MhzFactory and its API remain but 
+    it is not subclassed.
+ </li>
+<li>A new method InterferenceHelper::AddForeignSignal has been introduced to 
+    support use of the SpectrumWifiPhy (so that non-Wi-Fi signals may be handled 
+    as noise power).
+</li>
+<li>A new method InterferenceHelper::AddForeignSignal has been introduced to 
+    support use of the SpectrumWifiPhy (so that non-Wi-Fi signals may be handled 
+    as noise power).
+</li>
+<li>AODV now honors the TTL in RREQ/RREP and it uses a method compliant with 
+    <a href="http://www.ietf.org/rfc/rfc3561.txt">RFC 3561</a>. I.e., the
+    node search radius is increased progressively. This could increase slightly 
+    the node search time, but it also decreases the network congestion.
 </li>
-<li> The class <b>WifiSpectrumValueHelper</b> has been refactored; previously it was an abstract base class supporting the WifiSpectrumValue5MhzFactory spectrum model.  It now contains various static member methods supporting the creation of power spectral densities with the granularity of a Wi-Fi OFDM subcarrier bandwidth.  The class WifiSpectrumValue5MhzFactory and its API remain but it is not subclassed.</li>
-<li> A new method InterferenceHelper::AddForeignSignal has been introduced to support use of the SpectrumWifiPhy (so that non-Wi-Fi signals may be handled as noise power).</li>
 </ul>
 <h2>Changes to build system:</h2>
 <ul>
@@ -111,7 +140,16 @@ for class <tt>DesMetrics</tt> for more details.
 <h2>Changed behavior:</h2>
 This section is for behavioral changes to the models that were not due to a bug fix.
 <ul>
-  <li> (wifi) The relationship between channel number, frequency, channel width, and Wi-Fi standard has been revised (see bug 2412).  Previously, ChannelNumber and Frequency were attributes of class YansWifiPhy, and the frequency was defined as the start of the band.  Now, Frequency has been redefined to be the center frequency of the channel, and the underlying device relies on the pair of frequency and channel width to control behavior; the channel number and Wi-Fi standard are used as attributes to configure frequency and channel width.  The wifi module documentation discusses this change and the new behavior.
+  <li>(wifi) The relationship between channel number, frequency, channel width, 
+      and Wi-Fi standard has been revised (see bug 2412).  Previously, ChannelNumber 
+      and Frequency were attributes of class YansWifiPhy, and the frequency was 
+      defined as the start of the band.  Now, Frequency has been redefined to be 
+      the center frequency of the channel, and the underlying device relies on 
+      the pair of frequency and channel width to control behavior; the channel 
+      number and Wi-Fi standard are used as attributes to configure frequency 
+      and channel width.  The wifi module documentation discusses this change 
+      and the new behavior.
+  </li>
 </ul>
 
 <hr>
diff --git a/RELEASE_NOTES b/RELEASE_NOTES
index 15d288c89..d00197e96 100644
--- a/RELEASE_NOTES
+++ b/RELEASE_NOTES
@@ -43,6 +43,7 @@ New user-visible features
   over time is expected to support a different PHY abstraction and error
   models.
 - (core) DES Metrics support, see the API docs for class DesMetrics.
+- (aodv) The node search radius is increased progressively (as per standard). 
 
 Bugs fixed
 ----------
@@ -51,6 +52,7 @@ Bugs fixed
 - Bug 1939 - Aggregating the same object to two nodes produce unexpected results
 - Bug 1977 - v4Ping verbose output when not explicitly stopped
 - Bug 2057 - ARP and Ndisc caches should be updated by receiving valid L3 packets
+- Bug 2123 - AODV doesn't use / honor IP TTL in the RREQ / RREP
 - Bug 2222 - incorrect EDCA behavior in case of internal collision
 - Bug 2308 - PacketTag instead of ByteTag in LTE PDCP/RLC
 - Bug 2346 - SixLowPan ConpressionThreshold can be violated.
diff --git a/src/aodv/model/aodv-routing-protocol.cc b/src/aodv/model/aodv-routing-protocol.cc
index 24f33e207..ead590c91 100644
--- a/src/aodv/model/aodv-routing-protocol.cc
+++ b/src/aodv/model/aodv-routing-protocol.cc
@@ -35,6 +35,8 @@
 #include "ns3/inet-socket-address.h"
 #include "ns3/trace-source-accessor.h"
 #include "ns3/udp-socket-factory.h"
+#include "ns3/udp-l4-protocol.h"
+#include "ns3/udp-header.h"
 #include "ns3/wifi-net-device.h"
 #include "ns3/adhoc-wifi-mac.h"
 #include "ns3/string.h"
@@ -119,6 +121,10 @@ NS_OBJECT_ENSURE_REGISTERED (DeferredRouteOutputTag);
 //-----------------------------------------------------------------------------
 RoutingProtocol::RoutingProtocol () :
   RreqRetries (2),
+  TtlStart (1),
+  TtlIncrement (2),
+  TtlThreshold (7),
+  TimeoutBuffer (2),
   RreqRateLimit (10),
   RerrRateLimit (10),
   ActiveRouteTimeout (Seconds (3)),
@@ -165,6 +171,22 @@ RoutingProtocol::GetTypeId (void)
                    TimeValue (Seconds (1)),
                    MakeTimeAccessor (&RoutingProtocol::HelloInterval),
                    MakeTimeChecker ())
+    .AddAttribute ("TtlStart", "Initial TTL value for RREQ.",
+                   UintegerValue (1),
+                   MakeUintegerAccessor (&RoutingProtocol::TtlStart),
+                   MakeUintegerChecker<uint16_t> ())
+    .AddAttribute ("TtlIncrement", "TTL increment for each attempt using the expanding ring search for RREQ dissemination.",
+                   UintegerValue (2),
+                   MakeUintegerAccessor (&RoutingProtocol::TtlIncrement),
+                   MakeUintegerChecker<uint16_t> ())
+    .AddAttribute ("TtlThreshold", "Maximum TTL value for expanding ring search, TTL = NetDiameter is used beyond this value.",
+                   UintegerValue (7),
+                   MakeUintegerAccessor (&RoutingProtocol::TtlThreshold),
+                   MakeUintegerChecker<uint16_t> ())
+    .AddAttribute ("TimeoutBuffer", "Provide a buffer for the timeout.",
+                   UintegerValue (2),
+                   MakeUintegerAccessor (&RoutingProtocol::TimeoutBuffer),
+                   MakeUintegerChecker<uint16_t> ())
     .AddAttribute ("RreqRetries", "Maximum number of retransmissions of RREQ to discover a route",
                    UintegerValue (2),
                    MakeUintegerAccessor (&RoutingProtocol::RreqRetries),
@@ -476,6 +498,16 @@ RoutingProtocol::RouteInput (Ptr<const Packet> p, const Ipv4Header &header,
               {
                 return true;
               }
+            if (header.GetProtocol () == UdpL4Protocol::PROT_NUMBER)
+              {
+                UdpHeader udpHeader;
+                p->PeekHeader (udpHeader);
+                if (udpHeader.GetDestinationPort () == AODV_PORT)
+                  {
+                    // AODV packets sent in broadcast are already managed
+                    return true;
+                  }
+              }
             if (header.GetTtl () > 1)
               {
                 NS_LOG_LOGIC ("Forward broadcast. TTL " << (uint16_t) header.GetTtl ());
@@ -632,7 +664,7 @@ RoutingProtocol::NotifyInterfaceUp (uint32_t i)
   socket->Bind (InetSocketAddress (iface.GetLocal (), AODV_PORT));
   socket->BindToNetDevice (l3->GetNetDevice (i));
   socket->SetAllowBroadcast (true);
-  socket->SetAttribute ("IpTtl", UintegerValue (1));
+  socket->SetIpRecvTtl (true);
   m_socketAddresses.insert (std::make_pair (socket, iface));
 
   // create also a subnet broadcast socket
@@ -643,7 +675,7 @@ RoutingProtocol::NotifyInterfaceUp (uint32_t i)
   socket->Bind (InetSocketAddress (iface.GetBroadcast (), AODV_PORT));
   socket->BindToNetDevice (l3->GetNetDevice (i));
   socket->SetAllowBroadcast (true);
-  socket->SetAttribute ("IpTtl", UintegerValue (1));
+  socket->SetIpRecvTtl (true);
   m_socketSubnetBroadcastAddresses.insert (std::make_pair (socket, iface));
 
   // Add local broadcast record to the routing table
@@ -744,7 +776,7 @@ RoutingProtocol::NotifyAddAddress (uint32_t i, Ipv4InterfaceAddress address)
           socket->Bind (InetSocketAddress (iface.GetBroadcast (), AODV_PORT));
           socket->BindToNetDevice (l3->GetNetDevice (i));
           socket->SetAllowBroadcast (true);
-          socket->SetAttribute ("IpTtl", UintegerValue (1));
+          socket->SetIpRecvTtl (true);
           m_socketSubnetBroadcastAddresses.insert (std::make_pair (socket, iface));
 
           // Add local broadcast record to the routing table
@@ -793,7 +825,7 @@ RoutingProtocol::NotifyRemoveAddress (uint32_t i, Ipv4InterfaceAddress address)
           socket->Bind (InetSocketAddress (iface.GetLocal (), AODV_PORT));
           socket->BindToNetDevice (l3->GetNetDevice (i));
           socket->SetAllowBroadcast (true);
-          socket->SetAttribute ("IpTtl", UintegerValue (1));
+          socket->SetIpRecvTtl (true);
           m_socketAddresses.insert (std::make_pair (socket, iface));
 
           // create also a unicast socket
@@ -804,7 +836,7 @@ RoutingProtocol::NotifyRemoveAddress (uint32_t i, Ipv4InterfaceAddress address)
           socket->Bind (InetSocketAddress (iface.GetBroadcast (), AODV_PORT));
           socket->BindToNetDevice (l3->GetNetDevice (i));
           socket->SetAllowBroadcast (true);
-          socket->SetAttribute ("IpTtl", UintegerValue (1));
+          socket->SetIpRecvTtl (true);
           m_socketSubnetBroadcastAddresses.insert (std::make_pair (socket, iface));
 
           // Add local broadcast record to the routing table
@@ -910,14 +942,29 @@ RoutingProtocol::SendRequest (Ipv4Address dst)
   rreqHeader.SetDst (dst);
 
   RoutingTableEntry rt;
+  // Using the Hop field in Routing Table to manage the expanding ring search
+  uint16_t ttl = TtlStart;
   if (m_routingTable.LookupRoute (dst, rt))
     {
-      rreqHeader.SetHopCount (rt.GetHop ());
+      if (rt.GetFlag () != IN_SEARCH)
+        {
+          ttl = std::min<uint16_t> (rt.GetHop () + TtlIncrement, NetDiameter);
+        }
+      else
+        {
+          ttl = rt.GetHop () + TtlIncrement;
+          if (ttl > TtlThreshold)
+            ttl = NetDiameter;
+        }
+      if (ttl == NetDiameter)
+        rt.IncrementRreqCnt ();
       if (rt.GetValidSeqNo ())
         rreqHeader.SetDstSeqno (rt.GetSeqNo ());
       else
         rreqHeader.SetUnknownSeqno (true);
+      rt.SetHop (ttl);
       rt.SetFlag (IN_SEARCH);
+      rt.SetLifeTime (PathDiscoveryTime);
       m_routingTable.Update (rt);
     }
   else
@@ -925,8 +972,11 @@ RoutingProtocol::SendRequest (Ipv4Address dst)
       rreqHeader.SetUnknownSeqno (true);
       Ptr<NetDevice> dev = 0;
       RoutingTableEntry newEntry (/*device=*/ dev, /*dst=*/ dst, /*validSeqNo=*/ false, /*seqno=*/ 0,
-                                              /*iface=*/ Ipv4InterfaceAddress (),/*hop=*/ 0,
-                                              /*nextHop=*/ Ipv4Address (), /*lifeTime=*/ Seconds (0));
+                                              /*iface=*/ Ipv4InterfaceAddress (),/*hop=*/ ttl,
+                                              /*nextHop=*/ Ipv4Address (), /*lifeTime=*/ PathDiscoveryTime);
+      // Check if TtlStart == NetDiameter
+      if (ttl == NetDiameter)
+        newEntry.IncrementRreqCnt ();
       newEntry.SetFlag (IN_SEARCH);
       m_routingTable.AddRoute (newEntry);
     }
@@ -940,7 +990,6 @@ RoutingProtocol::SendRequest (Ipv4Address dst)
   rreqHeader.SetOriginSeqno (m_seqNo);
   m_requestId++;
   rreqHeader.SetId (m_requestId);
-  rreqHeader.SetHopCount (0);
 
   // Send RREQ as subnet directed broadcast from each interface used by aodv
   for (std::map<Ptr<Socket>, Ipv4InterfaceAddress>::const_iterator j =
@@ -953,6 +1002,9 @@ RoutingProtocol::SendRequest (Ipv4Address dst)
       m_rreqIdCache.IsDuplicate (iface.GetLocal (), m_requestId);
 
       Ptr<Packet> packet = Create<Packet> ();
+      SocketIpTtlTag tag;
+      tag.SetTtl (ttl);
+      packet->AddPacketTag (tag);
       packet->AddHeader (rreqHeader);
       TypeHeader tHeader (AODVTYPE_RREQ);
       packet->AddHeader (tHeader);
@@ -993,10 +1045,18 @@ RoutingProtocol::ScheduleRreqRetry (Ipv4Address dst)
   m_addressReqTimer[dst].SetArguments (dst);
   RoutingTableEntry rt;
   m_routingTable.LookupRoute (dst, rt);
-  rt.IncrementRreqCnt ();
-  m_routingTable.Update (rt);
-  m_addressReqTimer[dst].Schedule (Time (rt.GetRreqCnt () * NetTraversalTime));
-  NS_LOG_LOGIC ("Scheduled RREQ retry in " << Time (rt.GetRreqCnt () * NetTraversalTime).GetSeconds () << " seconds");
+  Time retry;
+  if (rt.GetHop () < NetDiameter)
+    {
+      retry = 2 * NodeTraversalTime * (rt.GetHop () + TimeoutBuffer);
+    }
+  else
+    {
+      // Binary exponential backoff
+      retry = std::pow<uint16_t> (2, rt.GetRreqCnt () - 1) * NetTraversalTime;
+    }
+  m_addressReqTimer[dst].Schedule (retry);
+  NS_LOG_LOGIC ("Scheduled RREQ retry in " << retry.GetSeconds () << " seconds");
 }
 
 void
@@ -1254,12 +1314,23 @@ RoutingProtocol::RecvRequest (Ptr<Packet> p, Ipv4Address receiver, Ipv4Address s
         }
     }
 
+  SocketIpTtlTag tag;
+  p->RemovePacketTag (tag);
+  if (tag.GetTtl () < 2)
+    {
+      NS_LOG_DEBUG ("TTL exceeded. Drop RREQ origin " << src << " destination " << dst );
+      return;
+    }
+
   for (std::map<Ptr<Socket>, Ipv4InterfaceAddress>::const_iterator j =
          m_socketAddresses.begin (); j != m_socketAddresses.end (); ++j)
     {
       Ptr<Socket> socket = j->first;
       Ipv4InterfaceAddress iface = j->second;
       Ptr<Packet> packet = Create<Packet> ();
+      SocketIpTtlTag ttl;
+      ttl.SetTtl (tag.GetTtl () - 1);
+      packet->AddPacketTag (ttl);
       packet->AddHeader (rreqHeader);
       TypeHeader tHeader (AODVTYPE_RREQ);
       packet->AddHeader (tHeader);
@@ -1292,6 +1363,9 @@ RoutingProtocol::SendReply (RreqHeader const & rreqHeader, RoutingTableEntry con
   RrepHeader rrepHeader ( /*prefixSize=*/ 0, /*hops=*/ 0, /*dst=*/ rreqHeader.GetDst (),
                                           /*dstSeqNo=*/ m_seqNo, /*origin=*/ toOrigin.GetDestination (), /*lifeTime=*/ MyRouteTimeout);
   Ptr<Packet> packet = Create<Packet> ();
+  SocketIpTtlTag tag;
+  tag.SetTtl (toOrigin.GetHop ());
+  packet->AddPacketTag (tag);
   packet->AddHeader (rrepHeader);
   TypeHeader tHeader (AODVTYPE_RREP);
   packet->AddHeader (tHeader);
@@ -1324,6 +1398,9 @@ RoutingProtocol::SendReplyByIntermediateNode (RoutingTableEntry & toDst, Routing
   m_routingTable.Update (toOrigin);
 
   Ptr<Packet> packet = Create<Packet> ();
+  SocketIpTtlTag tag;
+  tag.SetTtl (toOrigin.GetHop ());
+  packet->AddPacketTag (tag);
   packet->AddHeader (rrepHeader);
   TypeHeader tHeader (AODVTYPE_RREP);
   packet->AddHeader (tHeader);
@@ -1338,6 +1415,9 @@ RoutingProtocol::SendReplyByIntermediateNode (RoutingTableEntry & toDst, Routing
                                                  /*dst seqno=*/ toOrigin.GetSeqNo (), /*origin=*/ toDst.GetDestination (),
                                                  /*lifetime=*/ toOrigin.GetLifeTime ());
       Ptr<Packet> packetToDst = Create<Packet> ();
+      SocketIpTtlTag gratTag;
+      gratTag.SetTtl (toDst.GetHop ());
+      packetToDst->AddPacketTag (gratTag);
       packetToDst->AddHeader (gratRepHeader);
       TypeHeader type (AODVTYPE_RREP);
       packetToDst->AddHeader (type);
@@ -1355,6 +1435,9 @@ RoutingProtocol::SendReplyAck (Ipv4Address neighbor)
   RrepAckHeader h;
   TypeHeader typeHeader (AODVTYPE_RREP_ACK);
   Ptr<Packet> packet = Create<Packet> ();
+  SocketIpTtlTag tag;
+  tag.SetTtl (1);
+  packet->AddPacketTag (tag);
   packet->AddHeader (h);
   packet->AddHeader (typeHeader);
   RoutingTableEntry toNeighbor;
@@ -1480,8 +1563,18 @@ RoutingProtocol::RecvReply (Ptr<Packet> p, Ipv4Address receiver, Ipv4Address sen
       toNextHopToOrigin.InsertPrecursor (toDst.GetNextHop ());
       m_routingTable.Update (toNextHopToOrigin);
     }
+  SocketIpTtlTag tag;
+  p->RemovePacketTag(tag);
+  if (tag.GetTtl () < 2)
+    {
+      NS_LOG_DEBUG ("TTL exceeded. Drop RREP destination " << dst << " origin " << rrepHeader.GetOrigin ());
+      return;
+    }
 
   Ptr<Packet> packet = Create<Packet> ();
+  SocketIpTtlTag ttl;
+  ttl.SetTtl (tag.GetTtl() - 1);
+  packet->AddPacketTag (ttl);
   packet->AddHeader (rrepHeader);
   TypeHeader tHeader (AODVTYPE_RREP);
   packet->AddHeader (tHeader);
@@ -1569,6 +1662,9 @@ RoutingProtocol::RecvError (Ptr<Packet> p, Ipv4Address src )
         {
           TypeHeader typeHeader (AODVTYPE_RERR);
           Ptr<Packet> packet = Create<Packet> ();
+          SocketIpTtlTag tag;
+          tag.SetTtl (1);
+          packet->AddPacketTag (tag);
           packet->AddHeader (rerrHeader);
           packet->AddHeader (typeHeader);
           SendRerrMessage (packet, precursors);
@@ -1586,6 +1682,9 @@ RoutingProtocol::RecvError (Ptr<Packet> p, Ipv4Address src )
     {
       TypeHeader typeHeader (AODVTYPE_RERR);
       Ptr<Packet> packet = Create<Packet> ();
+      SocketIpTtlTag tag;
+      tag.SetTtl (1);
+      packet->AddPacketTag (tag);
       packet->AddHeader (rerrHeader);
       packet->AddHeader (typeHeader);
       SendRerrMessage (packet, precursors);
@@ -1611,7 +1710,7 @@ RoutingProtocol::RouteRequestTimerExpire (Ipv4Address dst)
    */
   if (toDst.GetRreqCnt () == RreqRetries)
     {
-      NS_LOG_LOGIC ("route discovery to " << dst << " has been attempted RreqRetries (" << RreqRetries << ") times");
+      NS_LOG_LOGIC ("route discovery to " << dst << " has been attempted RreqRetries (" << RreqRetries << ") times with ttl " << NetDiameter);
       m_addressReqTimer.erase (dst);
       m_routingTable.DeleteRoute (dst);
       NS_LOG_DEBUG ("Route not found. Drop all packets with dst " << dst);
@@ -1621,7 +1720,7 @@ RoutingProtocol::RouteRequestTimerExpire (Ipv4Address dst)
 
   if (toDst.GetFlag () == IN_SEARCH)
     {
-      NS_LOG_LOGIC ("Resend RREQ to " << dst << " ttl " << NetDiameter);
+      NS_LOG_LOGIC ("Resend RREQ to " << dst << " previous ttl " << toDst.GetHop ());
       SendRequest (dst);
     }
   else
@@ -1693,6 +1792,9 @@ RoutingProtocol::SendHello ()
       RrepHeader helloHeader (/*prefix size=*/ 0, /*hops=*/ 0, /*dst=*/ iface.GetLocal (), /*dst seqno=*/ m_seqNo,
                                                /*origin=*/ iface.GetLocal (),/*lifetime=*/ Time (AllowedHelloLoss * HelloInterval));
       Ptr<Packet> packet = Create<Packet> ();
+      SocketIpTtlTag tag;
+      tag.SetTtl (1);
+      packet->AddPacketTag (tag);
       packet->AddHeader (helloHeader);
       TypeHeader tHeader (AODVTYPE_RREP);
       packet->AddHeader (tHeader);
@@ -1757,6 +1859,9 @@ RoutingProtocol::SendRerrWhenBreaksLinkToNextHop (Ipv4Address nextHop)
           NS_LOG_LOGIC ("Send RERR message with maximum size.");
           TypeHeader typeHeader (AODVTYPE_RERR);
           Ptr<Packet> packet = Create<Packet> ();
+          SocketIpTtlTag tag;
+          tag.SetTtl (1);
+          packet->AddPacketTag (tag);
           packet->AddHeader (rerrHeader);
           packet->AddHeader (typeHeader);
           SendRerrMessage (packet, precursors);
@@ -1774,6 +1879,9 @@ RoutingProtocol::SendRerrWhenBreaksLinkToNextHop (Ipv4Address nextHop)
     {
       TypeHeader typeHeader (AODVTYPE_RERR);
       Ptr<Packet> packet = Create<Packet> ();
+      SocketIpTtlTag tag;
+      tag.SetTtl (1);
+      packet->AddPacketTag (tag);
       packet->AddHeader (rerrHeader);
       packet->AddHeader (typeHeader);
       SendRerrMessage (packet, precursors);
@@ -1802,6 +1910,9 @@ RoutingProtocol::SendRerrWhenNoRouteToForward (Ipv4Address dst,
   rerrHeader.AddUnDestination (dst, dstSeqNo);
   RoutingTableEntry toOrigin;
   Ptr<Packet> packet = Create<Packet> ();
+  SocketIpTtlTag tag;
+  tag.SetTtl (1);
+  packet->AddPacketTag (tag);
   packet->AddHeader (rerrHeader);
   packet->AddHeader (TypeHeader (AODVTYPE_RERR));
   if (m_routingTable.LookupValidRoute (origin, toOrigin))
diff --git a/src/aodv/model/aodv-routing-protocol.h b/src/aodv/model/aodv-routing-protocol.h
index c9925c4cf..9bef32702 100644
--- a/src/aodv/model/aodv-routing-protocol.h
+++ b/src/aodv/model/aodv-routing-protocol.h
@@ -103,6 +103,10 @@ private:
   
   // Protocol parameters.
   uint32_t RreqRetries;             ///< Maximum number of retransmissions of RREQ with TTL = NetDiameter to discover a route
+  uint16_t TtlStart;                ///< Initial TTL value for RREQ.
+  uint16_t TtlIncrement;            ///< TTL increment for each attempt using the expanding ring search for RREQ dissemination.
+  uint16_t TtlThreshold;            ///< Maximum TTL value for expanding ring search, TTL = NetDiameter is used beyond this value.
+  uint16_t TimeoutBuffer;           ///< Provide a buffer for the timeout.
   uint16_t RreqRateLimit;           ///< Maximum number of RREQ per second.
   uint16_t RerrRateLimit;           ///< Maximum number of REER per second.
   Time ActiveRouteTimeout;          ///< Period of time during which the route is considered to be valid.
@@ -172,9 +176,9 @@ private:
   /// If route exists and valid, forward packet.
   bool Forwarding (Ptr<const Packet> p, const Ipv4Header & header, UnicastForwardCallback ucb, ErrorCallback ecb);
   /**
-  * To reduce congestion in a network, repeated attempts by a source node at route discovery
-  * for a single destination MUST utilize a binary exponential backoff.
-  */
+   * Repeated attempts by a source node at route discovery for a single destination
+   * use the expanding ring search technique.
+   */
   void ScheduleRreqRetry (Ipv4Address dst);
   /**
    * Set lifetime field in routing table entry to the maximum of existing lifetime and lt, if the entry exists