diff --git a/examples/sprint-pops.latencies b/examples/sprint-pops.latencies
new file mode 100644
index 0000000..7c3fd07
--- /dev/null
+++ b/examples/sprint-pops.latencies
@@ -0,0 +1,84 @@
+0 1 0.312
+2 3 10.786
+1 4 0.222
+1 5 1.035
+1 6 1.414
+1 7 1.24
+1 8 0.814
+1 9 19.532
+1 10 0.352
+1 11 4.593
+12 13 2.622
+14 15 0.207
+14 16 12.098
+14 17 13.941
+15 18 7.791
+15 19 38.946
+20 21 19.775
+20 22 0.345
+23 24 5.337
+25 26 0.276
+27 28 0.645
+8 20 19.787
+8 16 8.352
+8 28 1.578
+8 24 10.459
+8 26 5.005
+21 31 20.741
+13 32 4.737
+13 33 1.424
+17 35 2.091
+17 20 14.409
+17 18 7.13
+17 28 6.214
+17 24 6.437
+17 25 1.315
+17 26 1.176
+17 29 3.282
+17 36 2.478
+11 24 5.751
+11 38 3.235
+11 17 4.718
+33 39 1.817
+33 40 2.035
+6 7 0.327
+6 28 0.97
+6 25 5.176
+6 8 0.612
+6 17 5.725
+6 34 0.802
+6 11 6.007
+39 42 0.699
+16 24 3.655
+16 29 0.135
+16 17 3.286
+31 45 0.268
+31 46 0.268
+31 37 3.375
+31 47 2.708
+32 48 1.712
+32 44 2.329
+32 42 1.595
+48 49 3.201
+7 13 31.13
+38 43 1.643
+9 15 5.513
+9 20 0.437
+9 31 2.648
+9 30 0.124
+9 17 14.774
+9 19 42.03
+5 32 28.338
+5 8 0.359
+5 7 0.316
+18 23 0.779
+40 48 2.34
+40 49 2.529
+24 38 7.706
+24 31 9.827
+24 45 10.045
+24 50 0.092
+3 9 59.812
+19 41 26.19
+19 20 42.057
+19 51 14.125
diff --git a/examples/sprint-pops.weights b/examples/sprint-pops.weights
new file mode 100644
index 0000000..387a37f
--- /dev/null
+++ b/examples/sprint-pops.weights
@@ -0,0 +1,84 @@
+0 1 312
+2 3 10786
+1 4 222
+1 5 2500
+1 6 4000
+1 7 2500
+1 8 3860
+1 9 11769
+1 10 352
+1 11 3500
+12 13 2622
+14 15 500
+14 16 14192
+14 17 8909
+15 18 11747
+15 19 44530
+20 21 19775
+20 22 345
+23 24 5337
+25 26 2184
+27 28 645
+8 20 11409
+8 16 8282
+8 28 3000
+8 24 7735
+8 26 5500
+21 31 20741
+13 32 7552
+13 33 1500
+17 35 2091
+17 20 14409
+17 18 4337
+17 28 4000
+17 24 5735
+17 25 1315
+17 26 2500
+17 29 3282
+17 36 2478
+11 24 5096
+11 38 3235
+11 17 4360
+33 39 2000
+33 40 3000
+6 7 2500
+6 28 6860
+6 25 5176
+6 8 5860
+6 17 3860
+6 34 802
+6 11 5500
+39 42 699
+16 24 1547
+16 29 3000
+16 17 5282
+31 45 500
+31 46 268
+31 37 3375
+31 47 2708
+32 48 1712
+32 44 2329
+32 42 3352
+48 49 3201
+7 13 30890
+38 43 1643
+9 15 5500
+9 20 2500
+9 31 4735
+9 30 124
+9 17 13909
+9 19 42030
+5 32 28338
+5 8 2360
+5 7 2000
+18 23 5735
+40 48 2340
+40 49 2529
+24 38 2860
+24 31 9909
+24 45 10409
+24 50 92
+3 9 59812
+19 41 26190
+19 20 39530
+19 51 14125
diff --git a/examples/sprint-topology.cc b/examples/sprint-topology.cc
index 3a53c35..b3baa7c 100644
--- a/examples/sprint-topology.cc
+++ b/examples/sprint-topology.cc
@@ -35,6 +35,13 @@
 
 NS_LOG_COMPONENT_DEFINE ("CcnxSprintTopology");
 
+void PrintTime ()
+{
+  NS_LOG_INFO (Simulator::Now ());
+
+  Simulator::Schedule (Seconds (1.0), PrintTime);
+}
+
 int 
 main (int argc, char *argv[])
 {
@@ -42,16 +49,20 @@
   // Packet::EnablePrinting();
   string weights ("./src/NDNabstraction/examples/sprint.weights");
   string latencies ("./src/NDNabstraction/examples/sprint.latencies");
+  string positions;
     
   Time finishTime = Seconds (2.0);
   string animationFile;
   string strategy = "ns3::CcnxFloodingStrategy";
+  string save;
   CommandLine cmd;
   cmd.AddValue ("finish", "Finish time", finishTime);
   cmd.AddValue ("netanim", "NetAnim filename", animationFile);
   cmd.AddValue ("strategy", "CCNx forwarding strategy", strategy);
   cmd.AddValue ("weights", "Weights file", weights);
   cmd.AddValue ("latencies", "Latencies file", latencies);
+  cmd.AddValue ("positions", "Positions files", positions);
+  cmd.AddValue ("save", "Save positions to a file", save);
   cmd.Parse (argc, argv);
 
   // ------------------------------------------------------------
@@ -61,9 +72,16 @@
   RocketfuelWeightsReader reader ("/sprint");
   reader.SetBoundingBox (0, 0, 400, 250);
 
+  if (!positions.empty())
+    {
+      reader.SetFileName (positions);
+      reader.SetFileType (RocketfuelWeightsReader::POSITIONS);
+      reader.Read ();
+    }
+  
   reader.SetFileName (weights);
   reader.SetFileType (RocketfuelWeightsReader::WEIGHTS);    
-  NodeContainer nodes = reader.Read ();
+  reader.Read ();
 
   reader.SetFileName (latencies);
   reader.SetFileType (RocketfuelWeightsReader::LATENCIES);    
@@ -76,13 +94,13 @@
       return -1;
     }
     
-  NS_LOG_INFO("Nodes = " << nodes.GetN());
+  NS_LOG_INFO("Nodes = " << reader.GetNodes ().GetN());
   NS_LOG_INFO("Links = " << reader.LinksSize ());
     
   InternetStackHelper stack;
   Ipv4GlobalRoutingHelper ipv4RoutingHelper ("ns3::Ipv4GlobalRoutingOrderedNexthops");
   stack.SetRoutingHelper (ipv4RoutingHelper);
-  stack.Install (nodes);
+  stack.Install (reader.GetNodes ());
 
   reader.AssignIpv4Addresses (Ipv4Address ("10.0.0.0"));
 
@@ -98,14 +116,21 @@
   // ccnxHelper.InstallFakeGlobalRoutes ();
   // ccnxHelper.InstallRouteTo (Names::Find<Node> ("/sprint", "San+Jose,+CA4062"));
 
-  // Simulator::Schedule (Seconds (1.0), PrintFIBs);
-  // PrintFIBs ();
-
   Simulator::Stop (finishTime);
+  Simulator::Schedule (Seconds (1.0), PrintTime);
+
+  // reader.SavePositions (save+".debug");
 
   NS_LOG_INFO ("Run Simulation.");
   Simulator::Run ();
   Simulator::Destroy ();
   NS_LOG_INFO ("Done.");
+
+  if (!save.empty ())
+    {
+      NS_LOG_INFO ("Saving positions.");
+      reader.SavePositions (save);
+    }
+  
   return 0;
 }
diff --git a/model/annotated-topology-reader.cc b/model/annotated-topology-reader.cc
index 2ca17eb..194a90c 100644
--- a/model/annotated-topology-reader.cc
+++ b/model/annotated-topology-reader.cc
@@ -101,21 +101,28 @@
   loc->SetPosition (Vector (posX, posY, 0));
 
   Names::Add (m_path, name, node);
+  m_nodes.Add (node);
 
   return node;
 }
 
 NodeContainer
+AnnotatedTopologyReader::GetNodes () const
+{
+  return m_nodes;
+}
+
+
+NodeContainer
 AnnotatedTopologyReader::Read (void)
 {
   ifstream topgen;
   topgen.open (GetFileName ().c_str ());
-  NodeContainer nodes;
         
   if ( !topgen.is_open () )
     {
       NS_LOG_ERROR ("Cannot open file " << GetFileName () << " for reading");
-      return nodes;
+      return m_nodes;
     }
 
   while (!topgen.eof ())
@@ -138,8 +145,9 @@
       double latitude, longitude;
 
       lineBuffer >> name >> city >> latitude >> longitude;
+      if (name.empty ()) continue;
+
       Ptr<Node> node = CreateNode (name, m_scale*longitude, -m_scale*latitude);
-      nodes.Add (node);
     }
 
   map<string, set<string> > processedLinks; // to eliminate duplications
@@ -185,12 +193,12 @@
       NS_LOG_DEBUG ("New link " << from << " <==> " << to << " / " << capacity << " with " << metric << " metric (" << delay << ", " << maxPackets << ")");
     }
         
-  NS_LOG_INFO ("Annotated topology created with " << nodes.GetN () << " nodes and " << LinksSize () << " links");
+  NS_LOG_INFO ("Annotated topology created with " << m_nodes.GetN () << " nodes and " << LinksSize () << " links");
   topgen.close ();
         
   ApplySettings ();
   
-  return nodes;
+  return m_nodes;
 }
     
 void
diff --git a/model/annotated-topology-reader.h b/model/annotated-topology-reader.h
index cbcd890..b9268b8 100644
--- a/model/annotated-topology-reader.h
+++ b/model/annotated-topology-reader.h
@@ -53,8 +53,14 @@
    *
    * \return the container of the nodes created (or empty container if there was an error)
    */
-  virtual
-  NodeContainer Read (void);
+  virtual NodeContainer
+  Read ();
+
+  /**
+   * \brief Get nodes read by the reader
+   */
+  NodeContainer
+  GetNodes () const;
     
   /**
    * \brief Assign IPv4 addresses to all links
@@ -92,6 +98,7 @@
     
 protected:
   std::string m_path;
+  NodeContainer m_nodes;
 
 private:
   AnnotatedTopologyReader (const AnnotatedTopologyReader&);
diff --git a/model/rocketfuel-weights-reader.cc b/model/rocketfuel-weights-reader.cc
index 448464e..f6895fa 100644
--- a/model/rocketfuel-weights-reader.cc
+++ b/model/rocketfuel-weights-reader.cc
@@ -39,8 +39,7 @@
 #include "ns3/uinteger.h"
 #include "ns3/ipv4-address.h"
 
-#include "ns3/constant-position-mobility-model.h"
-#include "ns3/random-variable.h"
+#include "ns3/mobility-model.h"
 
 #include <regex.h>
 
@@ -78,14 +77,16 @@
 NodeContainer
 RocketfuelWeightsReader::Read ()
 {
+  if (m_inputType == POSITIONS)
+    return AnnotatedTopologyReader::Read ();
+  
   ifstream topgen;
   topgen.open (GetFileName ().c_str ());
-  NodeContainer nodes;
         
   if ( !topgen.is_open () )
     {
       NS_LOG_ERROR ("Cannot open file " << GetFileName () << " for reading");
-      return nodes;
+      return m_nodes;
     }
 
   map<string, set<string> > processedLinks; // to eliminate duplications
@@ -117,14 +118,12 @@
       if (fromNode == 0)
         {
           fromNode = CreateNode (from);
-          nodes.Add (fromNode);
         }
 
       Ptr<Node> toNode   = Names::Find<Node> (m_path, to);
       if (toNode == 0)
         {
           toNode = CreateNode (to);
-          nodes.Add (toNode);
         }
 
       Link *link;
@@ -142,8 +141,8 @@
         {
         case WEIGHTS:
           {
-            double metric = boost::lexical_cast<double> (attribute);
-            link->SetAttribute ("OSPF", boost::lexical_cast<string> (metric*2));
+            uint16_t metric = boost::lexical_cast<uint16_t> (attribute);
+            link->SetAttribute ("OSPF", boost::lexical_cast<string> (metric));
             break;
           }
         case LATENCIES:
@@ -165,9 +164,9 @@
 
   if (!repeatedRun)
     {
-      NS_LOG_INFO ("Rocketfuel topology created with " << nodes.GetN () << " nodes and " << LinksSize () << " links");
+      NS_LOG_INFO ("Rocketfuel topology created with " << m_nodes.GetN () << " nodes and " << LinksSize () << " links");
     }
-  return nodes;
+  return m_nodes;
 }
 
 void
@@ -178,6 +177,23 @@
   SpringMobilityHelper::InstallSprings (LinksBegin (), LinksEnd ());
 }
 
+void
+RocketfuelWeightsReader::SavePositions (const std::string &file) const
+{
+  ofstream os (file.c_str (), ios::trunc);
+  os << "router\n";
+  
+  for (NodeContainer::Iterator node = m_nodes.Begin ();
+       node != m_nodes.End ();
+       node++)
+    {
+      std::string name = Names::FindName (*node);
+      Ptr<MobilityModel> mobility = (*node)->GetObject<MobilityModel> ();
+      Vector position = mobility->GetPosition ();
+
+      os << name << "\t" << "unknown" << "\t" << -position.y << "\t" << position.x << "\n";
+    }
+}
 
 // void
 // RocketfuelWeightsReader::Cheat (NodeContainer &nodes)
diff --git a/model/rocketfuel-weights-reader.h b/model/rocketfuel-weights-reader.h
index ecf4905..cf6a784 100644
--- a/model/rocketfuel-weights-reader.h
+++ b/model/rocketfuel-weights-reader.h
@@ -64,12 +64,13 @@
   enum
     {
       WEIGHTS,
-      LATENCIES
+      LATENCIES,
+      POSITIONS
     };
 
-  // void
-  // Cheat (NodeContainer &nodes);
-
+  void
+  SavePositions (const std::string &file) const;
+  
 private:
   RocketfuelWeightsReader (const RocketfuelWeightsReader&);
   RocketfuelWeightsReader& operator= (const RocketfuelWeightsReader&);
diff --git a/utils/spring-mobility-model.cc b/utils/spring-mobility-model.cc
index 5fb968b..170b428 100644
--- a/utils/spring-mobility-model.cc
+++ b/utils/spring-mobility-model.cc
@@ -33,6 +33,9 @@
 NS_OBJECT_ENSURE_REGISTERED (SpringMobilityModel);
 
 double SpringMobilityModel::m_totalKineticEnergy = 0.0;
+bool SpringMobilityModel::m_stable = false;
+EventId SpringMobilityModel::m_updateEvent;
+double SpringMobilityModel::m_epsilon = 100.0;
 
 const double COLOUMB_K = 200; 
 
@@ -41,10 +44,10 @@
   static TypeId tid = TypeId ("ns3::SpringMobilityModel")
     .SetParent<MobilityModel> ()
     .AddConstructor<SpringMobilityModel> ()
-    .AddAttribute ("Epsilon", "Bound for kinetic energy when system is considered stable",
-                   DoubleValue (1000.0),
-                   MakeDoubleAccessor (&SpringMobilityModel::m_epsilon),
-                   MakeDoubleChecker<double> ())
+    // .AddAttribute ("Epsilon", "Bound for kinetic energy when system is considered stable",
+    //                DoubleValue (100.0),
+    //                MakeDoubleAccessor (&SpringMobilityModel::m_epsilon),
+    //                MakeDoubleChecker<double> ())
     .AddAttribute ("NodeMass", "Node mass",
                    DoubleValue (10),
                    MakeDoubleAccessor (&SpringMobilityModel::m_nodeMass),
@@ -62,7 +65,7 @@
                    MakeDoubleAccessor (&SpringMobilityModel::m_springConstant),
                    MakeDoubleChecker<double> ())
     .AddAttribute ("DampingFactor", "Dumping factor",
-                   DoubleValue (0.6),
+                   DoubleValue (0.8),
                    MakeDoubleAccessor (&SpringMobilityModel::m_dampingFactor),
                    MakeDoubleChecker<double> ())
     ;
@@ -73,7 +76,6 @@
 SpringMobilityModel::SpringMobilityModel ()
   : m_position (0,0,0)
   , m_velocity (0,0,0)
-  , m_stable (false)
 {
 }
 
@@ -90,15 +92,35 @@
 void
 SpringMobilityModel::DoStart ()
 {
-  // m_updateEvent = Simulator::Schedule (Seconds(0.05), &SpringMobilityModel::Update, this);
+  if (!m_updateEvent.IsRunning ())
+    m_updateEvent = Simulator::Schedule (Seconds(0.05), SpringMobilityModel::UpdateAll);
+}
 
-  // Simulator::Schedule (Seconds(2.0), &SpringMobilityModel::Test, this);
+void
+SpringMobilityModel::UpdateAll ()
+{
+  for (NodeList::Iterator node = NodeList::Begin ();
+       node != NodeList::End ();
+       node++)
+    {
+      Ptr<SpringMobilityModel> model = (*node)->GetObject<SpringMobilityModel> ();
+      if (model != 0)
+        model->Update ();
+    }
+
+  if (m_totalKineticEnergy < m_epsilon)
+    {
+      m_stable = true;
+      NS_LOG_INFO ("Stabilized with " << m_totalKineticEnergy);
+    }
+  else
+    m_updateEvent = Simulator::Schedule (Seconds(0.05), SpringMobilityModel::UpdateAll);  
 }
 
 void
 SpringMobilityModel::Update () const
 {
-  // NS_LOG_FUNCTION (this << m_stable << m_position << m_velocity);
+  NS_LOG_FUNCTION (this << m_stable << m_position << m_velocity);
   if (m_stable) return;
   Time now = Simulator::Now ();
 
@@ -152,22 +174,13 @@
   velocityValue = CalculateDistance (m_velocity, Vector(0,0,0)); 
   m_totalKineticEnergy += m_nodeMass * velocityValue * velocityValue;
 
-  if (m_totalKineticEnergy < m_epsilon)
-    {
-      m_stable = true;
-      NS_LOG_INFO ("Stabilized with " << m_totalKineticEnergy);
-    }
-
   NotifyCourseChange ();
-  // m_updateEvent = Simulator::Schedule (Seconds(0.05), &SpringMobilityModel::Update, this);
 }
 
 Vector
 SpringMobilityModel::DoGetPosition (void) const
 {
   // NS_LOG_FUNCTION (this << m_position);
-  Update ();
-  
   return m_position;
 }
 void 
@@ -178,6 +191,19 @@
 
   NotifyCourseChange ();
   m_stable = false;
+
+
+  for (NodeList::Iterator node = NodeList::Begin ();
+       node != NodeList::End ();
+       node++)
+    {
+      Ptr<SpringMobilityModel> model = (*node)->GetObject<SpringMobilityModel> ();
+      if (model != 0)
+        model->m_lastTime = Simulator::Now ();
+    }
+  
+  if (!m_updateEvent.IsRunning ())
+    m_updateEvent = Simulator::Schedule (Seconds(0.05), SpringMobilityModel::UpdateAll);
 }
 Vector
 SpringMobilityModel::DoGetVelocity (void) const
diff --git a/utils/spring-mobility-model.h b/utils/spring-mobility-model.h
index 553ab9d..700c994 100644
--- a/utils/spring-mobility-model.h
+++ b/utils/spring-mobility-model.h
@@ -68,8 +68,11 @@
   void 
   Update (void) const;
 
+  static void
+  UpdateAll ();
+
 private:
-  double m_epsilon;
+  static double m_epsilon;
 
   double m_nodeMass;
   double m_nodeCharge;
@@ -78,14 +81,13 @@
   double m_dampingFactor;
 
   static double m_totalKineticEnergy;  
+  static bool m_stable;
+  static EventId m_updateEvent;
   
   mutable Vector m_position;
   mutable Vector m_velocity;
-  mutable bool m_stable;
   mutable Time m_lastTime;
 
-  EventId m_updateEvent;
-
   std::list<Ptr<MobilityModel> > m_springs;
 };