--- a/examples/csma-multicast.cc	Mon Aug 13 12:08:01 2007 -0700
+++ b/examples/csma-multicast.cc	Mon Aug 13 14:58:06 2007 -0700
@@ -16,31 +16,27 @@
 
 // Network topology
 //
-//       n0    n1   n2   n3
-//       |     |    |    |
-//     =====================
+//                     Lan1
+//                 ===========
+//                 |    |    | 
+//       n0   n1   n2   n3   n4
+//       |    |    |
+//       ===========
+//           Lan0
 //
-// - CBR/UDP flows from n0 to n1, and from n3 to n0
-// - UDP packet size of 210 bytes, with per-packet interval 0.00375 sec.
-//   (i.e., DataRate of 448,000 bps)
-// - DropTail queues 
-// - Tracing of queues and packet receptions to file "csma-one-subnet.tr"
-
-#include <iostream>
-#include <fstream>
-#include <string>
-#include <cassert>
+// - Multicast source is at node n0;
+// - Multicast forwarded by node n2 onto LAN1;
+// - Nodes n0, n1, n2, n3, and n4 receive the multicast frame.
+// - Node n4 listens for the data (actual listener not yet implementted)
 
 #include "ns3/command-line.h"
 #include "ns3/default-value.h"
 #include "ns3/ptr.h"
 #include "ns3/random-variable.h"
 #include "ns3/debug.h"
-
 #include "ns3/simulator.h"
 #include "ns3/nstime.h"
 #include "ns3/data-rate.h"
-
 #include "ns3/ascii-trace.h"
 #include "ns3/pcap-trace.h"
 #include "ns3/internet-node.h"
@@ -58,15 +54,18 @@
 
 using namespace ns3;
 
-NS_DEBUG_COMPONENT_DEFINE ("Me");
+NS_DEBUG_COMPONENT_DEFINE ("CsmaMulticast");
 
 int 
 main (int argc, char *argv[])
 {
-  // Users may find it convenient to turn on explicit debugging
-  // for selected modules; the below lines suggest how to do this
+//
+// Users may find it convenient to turn on explicit debugging
+// for selected modules; the below lines suggest how to do this
+//
 #if 0
-  DebugComponentEnable("Me");
+  DebugComponentEnable("CsmaMulticast");
+
   DebugComponentEnable("Object");
   DebugComponentEnable("Queue");
   DebugComponentEnable("DropTailQueue");
@@ -86,105 +85,182 @@
   DebugComponentEnable("Ipv4LoopbackInterface");
 #endif
 
-  DebugComponentEnable("Me");
+  DebugComponentEnable("UdpSocket");
+  DebugComponentEnable("UdpL4Protocol");
+  DebugComponentEnable("Ipv4L3Protocol");
+  DebugComponentEnable("Ipv4StaticRouting");
+  DebugComponentEnable("Ipv4Interface");
+  DebugComponentEnable("ArpIpv4Interface");
+  DebugComponentEnable("Ipv4LoopbackInterface");
+
+  DebugComponentEnable("CsmaMulticast");
   DebugComponentEnable("CsmaChannel");
   DebugComponentEnable("CsmaNetDevice");
-  DebugComponentEnable("UdpL4Protocol");
-
-  // Set up some default values for the simulation.  Use the Bind()
-  // technique to tell the system what subclass of Queue to use,
-  // and what the queue limit is
-
-  // The below Bind command tells the queue factory which class to
-  // instantiate, when the queue factory is invoked in the topology code
+//
+// Set up default values for the simulation.  Use the DefaultValue::Bind()
+// technique to tell the system what subclass of Queue to use.  The Bind
+// command command tells the queue factory which class to instantiate when the
+// queue factory is invoked in the topology code
+//
   DefaultValue::Bind ("Queue", "DropTailQueue");
-
-  // Allow the user to override any of the defaults and the above
-  // Bind()s at run-time, via command-line arguments
+//
+// Allow the user to override any of the defaults and the above Bind() at
+// run-time, via command-line arguments
+//
   CommandLine::Parse (argc, argv);
-
-  // Here, we will explicitly create four nodes.  In more sophisticated
-  // topologies, we could configure a node factory.
+//
+// Explicitly create the nodes required by the topology (shown above).
+//
   NS_DEBUG("Create nodes.");
   Ptr<Node> n0 = Create<InternetNode> ();
   Ptr<Node> n1 = Create<InternetNode> (); 
   Ptr<Node> n2 = Create<InternetNode> (); 
   Ptr<Node> n3 = Create<InternetNode> ();
+  Ptr<Node> n4 = Create<InternetNode> ();
 
   NS_DEBUG("Create channels.");
-  // We create the channels first without any IP addressing information
-  Ptr<CsmaChannel> channel0 = 
+//
+// Explicitly create the channels required by the topology (shown above).
+//
+  Ptr<CsmaChannel> lan0 = 
+    CsmaTopology::CreateCsmaChannel(
+      DataRate(5000000), MilliSeconds(2));
+
+  Ptr<CsmaChannel> lan1 = 
     CsmaTopology::CreateCsmaChannel(
       DataRate(5000000), MilliSeconds(2));
 
   NS_DEBUG("Build Topology.");
-  uint32_t netDeviceNumberNode0 = CsmaIpv4Topology::AddIpv4CsmaNode (n0, 
-    channel0, Eui48Address("10:54:23:54:23:50"));
-  uint32_t netDeviceNumberNode1 = CsmaIpv4Topology::AddIpv4CsmaNode (n1, 
-    channel0, Eui48Address("10:54:23:54:23:51"));
-  uint32_t netDeviceNumberNode2 = CsmaIpv4Topology::AddIpv4CsmaNode (n2, 
-    channel0, Eui48Address("10:54:23:54:23:52"));
-  uint32_t netDeviceNumberNode3 = CsmaIpv4Topology::AddIpv4CsmaNode (n3, 
-    channel0, Eui48Address("10:54:23:54:23:53"));
+//
+// Now fill out the topology by creating the net devices required to connect
+// the nodes to the channels and hooking them up.  AddIpv4CsmaNetDevice will
+// create a net device, add a MAC address (in memory of the pink flamingo) and
+// connect the net device to a nodes and also to a channel. the 
+// AddIpv4CsmaNetDevice method returns a net device index for the net device
+// created on the node.  Interpret nd0 as the net device we created for node
+// zero.  Interpret nd2Lan0 as the net device we created for node two to
+// connect to Lan0. 
+//
+  uint32_t nd0 = CsmaIpv4Topology::AddIpv4CsmaNetDevice (n0, lan0, 
+    Eui48Address("08:00:2e:00:00:00"));
+  uint32_t nd1 = CsmaIpv4Topology::AddIpv4CsmaNetDevice (n1, lan0, 
+    Eui48Address("08:00:2e:00:00:01"));
+  uint32_t nd2Lan0 = CsmaIpv4Topology::AddIpv4CsmaNetDevice (n2, lan0, 
+    Eui48Address("08:00:2e:00:00:02"));
 
-  NS_DEBUG ("netDeviceNumberNode0 = " << netDeviceNumberNode0);
-  NS_DEBUG ("netDeviceNumberNode1 = " << netDeviceNumberNode1);
-  NS_DEBUG ("netDeviceNumberNode2 = " << netDeviceNumberNode2);
-  NS_DEBUG ("netDeviceNumberNode3 = " << netDeviceNumberNode3);
+  uint32_t nd2Lan1 = CsmaIpv4Topology::AddIpv4CsmaNetDevice (n2, lan1, 
+    Eui48Address("08:00:2e:00:00:00"));
+  uint32_t nd3 = CsmaIpv4Topology::AddIpv4CsmaNetDevice (n3, lan1, 
+    Eui48Address("08:00:2e:00:00:01"));
+  uint32_t nd4 = CsmaIpv4Topology::AddIpv4CsmaNetDevice (n4, lan1, 
+    Eui48Address("08:00:2e:00:00:02"));
 
-  // Later, we add IP addresses.  
+  NS_DEBUG ("nd0 = " << nd0);
+  NS_DEBUG ("nd1 = " << nd1);
+  NS_DEBUG ("nd2Lan0 = " << nd2Lan0);
+  NS_DEBUG ("nd2Lan1 = " << nd2Lan1);
+  NS_DEBUG ("nd3 = " << nd3);
+  NS_DEBUG ("nd4 = " << nd3);
+//
+// We've got the "hardware" in place.  Now we need to add IP addresses.
+//
   NS_DEBUG("Assign IP Addresses.");
-  // XXX BUGBUG
-  // Need a better way to get the interface index.  The point-to-point topology
-  // as implemented can't return the index since it creates interfaces on both
-  // sides (i.e., AddIpv4Addresses, not AddIpv4Address).  Need a method on
-  // Ipv4 to find the interface index corresponding to a given ipv4 address.
-  uint32_t ifIndexNode0 = CsmaIpv4Topology::AddIpv4Address (n0, 
-    netDeviceNumberNode0, Ipv4Address ("10.1.1.1"), 
-    Ipv4Mask ("255.255.255.0"));
+//
+// XXX BUGBUG
+// Need a better way to get the interface index.  The point-to-point topology
+// as implemented can't return the index since it creates interfaces on both
+// sides (i.e., it does AddIpv4Addresses, not AddIpv4Address).  We need a
+// method on Ipv4 to find the interface index corresponding to a given ipv4 
+// address.
+//
+// First, assign IP addresses to the net devices and associated interfaces
+// on Lan0.  The AddIpv4Address method returns an Ipv4 interface index.
+// Interpret ifIndexNd0 as the interface index to use to reference the
+// net device we created on node zero when coming in from the Ipv4 interface.
+// Net device numbers and interface indices are distinct.  Interpret
+// ifIndexNd2Lan0 as the interface index to use to reference the
+// net device we created that connects node two to lan zero.
+//
+  uint32_t ifIndexNd0 = CsmaIpv4Topology::AddIpv4Address (n0, nd0, 
+    Ipv4Address ("10.1.1.1"), Ipv4Mask ("255.255.255.0"));
 
-  uint32_t ifIndexNode1 = CsmaIpv4Topology::AddIpv4Address (n1, 
-    netDeviceNumberNode1, Ipv4Address ("10.1.1.2"), 
-    Ipv4Mask ("255.255.255.0"));
+  uint32_t ifIndexNd1 = CsmaIpv4Topology::AddIpv4Address (n1, nd1, 
+    Ipv4Address ("10.1.1.2"), Ipv4Mask ("255.255.255.0"));
 
-  uint32_t ifIndexNode2 = CsmaIpv4Topology::AddIpv4Address (n2, 
-    netDeviceNumberNode2, Ipv4Address ("10.1.1.3"), 
-    Ipv4Mask ("255.255.255.0"));
-  
-  uint32_t ifIndexNode3 = CsmaIpv4Topology::AddIpv4Address (n3, 
-    netDeviceNumberNode3, Ipv4Address ("10.1.1.4"), 
-    Ipv4Mask ("255.255.255.0"));
+  uint32_t ifIndexNd2Lan0 = CsmaIpv4Topology::AddIpv4Address (n2, nd2Lan0,
+    Ipv4Address ("10.1.1.3"), Ipv4Mask ("255.255.255.0"));
+//
+// Assign IP addresses to the net devices and associated interfaces on Lan1
+//
+  uint32_t ifIndexNd2Lan1 = CsmaIpv4Topology::AddIpv4Address (n2, nd2Lan1, 
+    Ipv4Address ("10.1.2.1"), Ipv4Mask ("255.255.255.0"));
+
+  uint32_t ifIndexNd3 = CsmaIpv4Topology::AddIpv4Address (n3, nd1, 
+    Ipv4Address ("10.1.2.2"), Ipv4Mask ("255.255.255.0"));
+
+  uint32_t ifIndexNd4 = CsmaIpv4Topology::AddIpv4Address (n4, nd4,
+    Ipv4Address ("10.1.2.3"), Ipv4Mask ("255.255.255.0"));
 
-  NS_DEBUG ("ifIndexNode0 = " << ifIndexNode0);
-  NS_DEBUG ("ifIndexNode1 = " << ifIndexNode1);
-  NS_DEBUG ("ifIndexNode2 = " << ifIndexNode2);
-  NS_DEBUG ("ifIndexNode3 = " << ifIndexNode3);
-
-  // Configure multicasting
+  NS_DEBUG ("ifIndexNd0 = " << ifIndexNd0);
+  NS_DEBUG ("ifIndexNd1 = " << ifIndexNd1);
+  NS_DEBUG ("ifIndexNd2Lan0 = " << ifIndexNd2Lan0);
+  NS_DEBUG ("ifIndexNd2Lan1 = " << ifIndexNd2Lan1);
+  NS_DEBUG ("ifIndexNd3 = " << ifIndexNd3);
+  NS_DEBUG ("ifIndexNd4 = " << ifIndexNd4);
   NS_DEBUG("Configure multicasting.");
+//
+// Now we can configure multicasting.  As described above, the multicast 
+// source is at node zero, which we assigned the IP address of 10.1.1.1 
+// earlier.  We need to define a multicast group to send packets to.  This
+// can be any multicast address from 224.0.0.0 through 239.255.255.255
+// (avoiding the reserved routing protocol addresses).  We just pick a
+// convenient number.
+//
   Ipv4Address multicastSource ("10.1.1.1");
   Ipv4Address multicastGroup ("225.0.0.0");
-
+//
+// We are going to manually configure multicast routing.  This means telling
+// node two that it should expect multicast data coming from IP address 
+// 10.1.1.1 over its IP interface connected to Lan0.  These are called
+// multicastSource and ifIndexNd2Lan0 respectively.  When node two receives
+// these packets, they should be forwarded out the interface that connects it
+// to Lan1 which is called ifIndexNd2Lan1.  All we need to do is to call the
+// AddMulticastRoute method on node two's Ipv4 interface and provide this
+// information.  (Note: the vector of output interfaces is in case there are
+// multiple net devices on a node).
+//
   Ptr<Ipv4> ipv4;
-  ipv4 = n0->QueryInterface<Ipv4> (Ipv4::iid);
+  ipv4 = n2->QueryInterface<Ipv4> (Ipv4::iid);
 
   std::vector<uint32_t> outputInterfaces (1);
-  outputInterfaces[0] = ifIndexNode0;
+  outputInterfaces[0] = ifIndexNd2Lan1;
 
-  ipv4->AddMulticastRoute (multicastSource, multicastGroup, 0, 
+  ipv4->AddMulticastRoute (multicastSource, multicastGroup, ifIndexNd2Lan0,
     outputInterfaces);
-
-  ipv4 = n1->QueryInterface<Ipv4> (Ipv4::iid);
-  //  ipv4->JoinMulticastGroup (multicastSource, multicastGroup);
+//
+// We also need to explain to the node zero forwarding code that when it sees
+// a packet destined for the multicast group it needs to send it out its
+// one and only interface.  The 0xffffffff in the call means that the input
+// interface qualification is not applicable in this case (the packet has
+// not been received over an interface, it has been created locally).
+//
+  ipv4 = n0->QueryInterface<Ipv4> (Ipv4::iid);
 
-  ipv4 = n2->QueryInterface<Ipv4> (Ipv4::iid);
-  //  ipv4->JoinMulticastGroup (multicastSource, multicastGroup);
+  outputInterfaces[0] = ifIndexNd0;;
 
-  ipv4 = n3->QueryInterface<Ipv4> (Ipv4::iid);
-  //  ipv4->JoinMulticastGroup (multicastSource, multicastGroup);
-
-  // Create the OnOff application to send UDP datagrams
-  // from n0 to the multicast group
+  ipv4->AddMulticastRoute (multicastSource, multicastGroup, 0xffffffff,
+    outputInterfaces);
+//
+// As described above, node four will be the only node listening for the
+// multicast data.  To enable forwarding bits up the protocol stack, we need
+// to tell the stack to join the multicast group.
+//
+  ipv4 = n4->QueryInterface<Ipv4> (Ipv4::iid);
+  ipv4->JoinMulticastGroup (multicastSource, multicastGroup);
+//
+// Create an OnOff application to send UDP datagrams from node zero to the
+// multicast group (node four will be listening).
+//
   NS_DEBUG("Create Applications.");
   Ptr<OnOffApplication> ooff = Create<OnOffApplication> (
     n0, 
@@ -192,27 +268,33 @@
     "Udp",
     ConstantVariable(1), 
     ConstantVariable(0),
-    DataRate ("128b/s"),
+    DataRate ("255b/s"),
     128);
-  // Start the application
+//
+// Tell the application when to start and stop.
+//
   ooff->Start(Seconds(1.));
   ooff->Stop (Seconds(10.));
-
-  // Configure tracing of all enqueue, dequeue, and NetDevice receive events
-  // Trace output will be sent to the csma-one-subnet.tr file
+//
+// Configure tracing of all enqueue, dequeue, and NetDevice receive events.
+// Trace output will be sent to the file "csma-multicast.tr"
+//
   NS_DEBUG("Configure Tracing.");
   AsciiTrace asciitrace ("csma-multicast.tr");
   asciitrace.TraceAllNetDeviceRx ();
   asciitrace.TraceAllQueues ();
-
-  // Also configure some tcpdump traces; each interface will be traced
-  // The output files will be named 
-  // simple-point-to-point.pcap-<nodeId>-<interfaceId>
-  // and can be read by the "tcpdump -r" command (use "-tt" option to
-  // display timestamps correctly)
+//
+// Also configure some tcpdump traces; each interface will be traced.
+// The output files will be named:
+//     csma-multicast.pcap-<nodeId>-<interfaceId>
+// and can be read by the "tcpdump -r" command (use "-tt" option to
+// display timestamps correctly)
+//
   PcapTrace pcaptrace ("csma-multicast.pcap");
   pcaptrace.TraceAllIp ();
-
+//
+// Now, do the actual simulation.
+//
   NS_DEBUG("Run Simulation.");
   Simulator::Run ();
   Simulator::Destroy ();

--- a/examples/csma-one-subnet.cc	Mon Aug 13 12:08:01 2007 -0700
+++ b/examples/csma-one-subnet.cc	Mon Aug 13 14:58:06 2007 -0700
@@ -14,35 +14,25 @@
  * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
  */
 
-// Port of ns-2/tcl/ex/simple.tcl to ns-3
-//
 // Network topology
 //
 //       n0    n1   n2   n3
 //       |     |    |    |
-//     =====================
+//       =================
+//              LAN
 //
-// - CBR/UDP flows from n0 to n1, and from n3 to n0
-// - UDP packet size of 210 bytes, with per-packet interval 0.00375 sec.
-//   (i.e., DataRate of 448,000 bps)
+// - CBR/UDP flows from n0 to n1 and from n3 to n0
 // - DropTail queues 
 // - Tracing of queues and packet receptions to file "csma-one-subnet.tr"
 
-#include <iostream>
-#include <fstream>
-#include <string>
-#include <cassert>
-
 #include "ns3/command-line.h"
 #include "ns3/default-value.h"
 #include "ns3/ptr.h"
 #include "ns3/random-variable.h"
 #include "ns3/debug.h"
-
 #include "ns3/simulator.h"
 #include "ns3/nstime.h"
 #include "ns3/data-rate.h"
-
 #include "ns3/ascii-trace.h"
 #include "ns3/pcap-trace.h"
 #include "ns3/internet-node.h"
@@ -60,15 +50,18 @@
 
 using namespace ns3;
 
-NS_DEBUG_COMPONENT_DEFINE ("Me");
+NS_DEBUG_COMPONENT_DEFINE ("CsmaOneSubnet");
 
 int 
 main (int argc, char *argv[])
 {
-  // Users may find it convenient to turn on explicit debugging
-  // for selected modules; the below lines suggest how to do this
+//
+// Users may find it convenient to turn on explicit debugging
+// for selected modules; the below lines suggest how to do this
+//
 #if 0 
-  DebugComponentEnable("Me");
+  DebugComponentEnable("CsmaOneSubnet");
+
   DebugComponentEnable("Object");
   DebugComponentEnable("Queue");
   DebugComponentEnable("DropTailQueue");
@@ -88,71 +81,90 @@
   DebugComponentEnable("Ipv4LoopbackInterface");
 #endif
 
-  DebugComponentEnable("Me");
-  DebugComponentEnable("OnOffApplication");
-  DebugComponentEnable("UdpSocket");
-  DebugComponentEnable("UdpL4Protocol");
-  DebugComponentEnable("Ipv4L3Protocol");
-  DebugComponentEnable("Ipv4StaticRouting");
-  DebugComponentEnable("CsmaNetDevice");
-  DebugComponentEnable("CsmaChannel");
-  DebugComponentEnable("Ipv4Interface");
-  DebugComponentEnable("ArpIpv4Interface");
-  DebugComponentEnable("Ipv4LoopbackInterface");
-
-  // Set up some default values for the simulation.  Use the Bind()
-  // technique to tell the system what subclass of Queue to use,
-  // and what the queue limit is
-
-  // The below Bind command tells the queue factory which class to
-  // instantiate, when the queue factory is invoked in the topology code
+//
+// Set up default values for the simulation.  Use the DefaultValue::Bind()
+// technique to tell the system what subclass of Queue to use.  The Bind
+// command command tells the queue factory which class to instantiate when the
+// queue factory is invoked in the topology code
+//
   DefaultValue::Bind ("Queue", "DropTailQueue");
-
-  // Allow the user to override any of the defaults and the above
-  // Bind()s at run-time, via command-line arguments
+//
+// Allow the user to override any of the defaults and the above Bind() at
+// run-time, via command-line arguments
+//
   CommandLine::Parse (argc, argv);
-
-  // Here, we will explicitly create four nodes.  In more sophisticated
-  // topologies, we could configure a node factory.
+//
+// Explicitly create the nodes required by the topology (shown above).
+//
   NS_DEBUG("Create nodes.");
   Ptr<Node> n0 = Create<InternetNode> ();
   Ptr<Node> n1 = Create<InternetNode> (); 
   Ptr<Node> n2 = Create<InternetNode> (); 
   Ptr<Node> n3 = Create<InternetNode> ();
 
-  // We create the channels first without any IP addressing information
   NS_DEBUG("Create channels.");
-  Ptr<CsmaChannel> channel0 = 
-    CsmaTopology::CreateCsmaChannel(
-      DataRate(5000000), MilliSeconds(2));
+//
+// Explicitly create the channels required by the topology (shown above).
+//
+  Ptr<CsmaChannel> lan = CsmaTopology::CreateCsmaChannel(
+    DataRate(5000000), MilliSeconds(2));
 
   NS_DEBUG("Build Topology.");
-  uint32_t n0ifIndex = CsmaIpv4Topology::AddIpv4CsmaNode (n0, channel0, 
-                                         Eui48Address("10:54:23:54:23:50"));
-  uint32_t n1ifIndex = CsmaIpv4Topology::AddIpv4CsmaNode (n1, channel0,
-                                         Eui48Address("10:54:23:54:23:51"));
-  uint32_t n2ifIndex = CsmaIpv4Topology::AddIpv4CsmaNode (n2, channel0,
-                                         Eui48Address("10:54:23:54:23:52"));
-  uint32_t n3ifIndex = CsmaIpv4Topology::AddIpv4CsmaNode (n3, channel0,
-                                         Eui48Address("10:54:23:54:23:53"));
+//
+// Now fill out the topology by creating the net devices required to connect
+// the nodes to the channels and hooking them up.  AddIpv4CsmaNetDevice will
+// create a net device, add a MAC address (in memory of the pink flamingo) and
+// connect the net device to a nodes and also to a channel. the 
+// AddIpv4CsmaNetDevice method returns a net device index for the net device
+// created on the node.  Interpret nd0 as the net device we created for node
+// zero.
+//
+  uint32_t nd0 = CsmaIpv4Topology::AddIpv4CsmaNetDevice (n0, lan, 
+    Eui48Address("08:00:2e:00:00:00"));
 
-  // Later, we add IP addresses.  
+  uint32_t nd1 = CsmaIpv4Topology::AddIpv4CsmaNetDevice (n1, lan, 
+    Eui48Address("08:00:2e:00:00:01"));
+
+  uint32_t nd2 = CsmaIpv4Topology::AddIpv4CsmaNetDevice (n2, lan, 
+    Eui48Address("08:00:2e:00:00:02"));
+
+  uint32_t nd3 = CsmaIpv4Topology::AddIpv4CsmaNetDevice (n3, lan, 
+    Eui48Address("08:00:2e:00:00:03"));
+
+  NS_DEBUG ("nd0 = " << nd0);
+  NS_DEBUG ("nd1 = " << nd1);
+  NS_DEBUG ("nd2 = " << nd2);
+  NS_DEBUG ("nd3 = " << nd3);
+//
+// We've got the "hardware" in place.  Now we need to add IP addresses.
+//
   NS_DEBUG("Assign IP Addresses.");
-  CsmaIpv4Topology::AddIpv4Address (
-      n0, n0ifIndex, Ipv4Address("10.1.1.1"), Ipv4Mask("255.255.255.0"));
-
-  CsmaIpv4Topology::AddIpv4Address (
-      n1, n1ifIndex, Ipv4Address("10.1.1.2"), Ipv4Mask("255.255.255.0"));
+//
+// XXX BUGBUG
+// Need a better way to get the interface index.  The point-to-point topology
+// as implemented can't return the index since it creates interfaces on both
+// sides (i.e., it does AddIpv4Addresses, not AddIpv4Address).  We need a
+// method on Ipv4 to find the interface index corresponding to a given ipv4 
+// address.
+//
+// Assign IP addresses to the net devices and associated interfaces
+// on the lan.  The AddIpv4Address method returns an Ipv4 interface index
+// which we do not need here.
+//
+  CsmaIpv4Topology::AddIpv4Address (n0, nd0, Ipv4Address("10.1.1.1"), 
+    Ipv4Mask("255.255.255.0"));
 
-  CsmaIpv4Topology::AddIpv4Address (
-      n2, n2ifIndex, Ipv4Address("10.1.1.3"), Ipv4Mask("255.255.255.0"));
+  CsmaIpv4Topology::AddIpv4Address (n1, nd1, Ipv4Address("10.1.1.2"), 
+    Ipv4Mask("255.255.255.0"));
+
+  CsmaIpv4Topology::AddIpv4Address (n2, nd2, Ipv4Address("10.1.1.3"), 
+    Ipv4Mask("255.255.255.0"));
   
-  CsmaIpv4Topology::AddIpv4Address (
-      n3, n3ifIndex, Ipv4Address("10.1.1.4"), Ipv4Mask("255.255.255.0"));
-
-  // Create the OnOff application to send UDP datagrams of size
-  // 210 bytes at a rate of 448 Kb/s
-  // from n0 to n1
+  CsmaIpv4Topology::AddIpv4Address (n3, nd3, Ipv4Address("10.1.1.4"), 
+    Ipv4Mask("255.255.255.0"));
+//
+// Create an OnOff application to send UDP datagrams from node zero to node 1.
+//
   NS_DEBUG("Create Applications.");
   Ptr<OnOffApplication> ooff = Create<OnOffApplication> (
     n0, 
@@ -160,36 +172,43 @@
     "Udp",
     ConstantVariable(1), 
     ConstantVariable(0));
-  // Start the application
+//
+// Tell the application when to start and stop.
+//
   ooff->Start(Seconds(1.0));
   ooff->Stop (Seconds(10.0));
-
-  // Create a similar flow from n3 to n0, starting at time 1.1 seconds
+// 
+// Create a similar flow from n3 to n0, starting at time 1.1 seconds
+//
   ooff = Create<OnOffApplication> (
     n3, 
     InetSocketAddress ("10.1.1.1", 80), 
     "Udp",
     ConstantVariable(1), 
     ConstantVariable(0));
-  // Start the application
+
   ooff->Start(Seconds(1.1));
   ooff->Stop (Seconds(10.0));
- 
-  // Configure tracing of all enqueue, dequeue, and NetDevice receive events
-  // Trace output will be sent to the csma-one-subnet.tr file
-  NS_DEBUG("Configure Tracing.");
+//
+// Configure tracing of all enqueue, dequeue, and NetDevice receive events.
+// Trace output will be sent to the file "csma-one-subnet.tr"
+//
+   NS_DEBUG("Configure Tracing.");
   AsciiTrace asciitrace ("csma-one-subnet.tr");
   asciitrace.TraceAllNetDeviceRx ();
   asciitrace.TraceAllQueues ();
-
-  // Also configure some tcpdump traces; each interface will be traced
-  // The output files will be named 
-  // simple-point-to-point.pcap-<nodeId>-<interfaceId>
-  // and can be read by the "tcpdump -r" command (use "-tt" option to
-  // display timestamps correctly)
+//
+// Also configure some tcpdump traces; each interface will be traced.
+// The output files will be named:
+//     csma-one-subnet.pcap-<nodeId>-<interfaceId>
+// and can be read by the "tcpdump -r" command (use "-tt" option to
+// display timestamps correctly)
+//
   PcapTrace pcaptrace ("csma-one-subnet.pcap");
   pcaptrace.TraceAllIp ();
-
+//
+// Now, do the actual simulation.
+//
   NS_DEBUG("Run Simulation.");
   Simulator::Run ();
   Simulator::Destroy ();

--- a/examples/mixed-global-routing.cc	Mon Aug 13 12:08:01 2007 -0700
+++ b/examples/mixed-global-routing.cc	Mon Aug 13 14:58:06 2007 -0700
@@ -128,13 +128,13 @@
     CsmaTopology::CreateCsmaChannel(
       DataRate(5000000), MilliSeconds(2));
 
-  uint32_t n2ifIndex = CsmaIpv4Topology::AddIpv4CsmaNode (n2, channelc0,
+  uint32_t n2ifIndex = CsmaIpv4Topology::AddIpv4CsmaNetDevice (n2, channelc0,
                                          Eui48Address("10:54:23:54:23:50"));
-  uint32_t n3ifIndex = CsmaIpv4Topology::AddIpv4CsmaNode (n3, channelc0,
+  uint32_t n3ifIndex = CsmaIpv4Topology::AddIpv4CsmaNetDevice (n3, channelc0,
                                          Eui48Address("10:54:23:54:23:51"));
-  uint32_t n4ifIndex = CsmaIpv4Topology::AddIpv4CsmaNode (n4, channelc0,
+  uint32_t n4ifIndex = CsmaIpv4Topology::AddIpv4CsmaNetDevice (n4, channelc0,
                                          Eui48Address("10:54:23:54:23:52"));
-  uint32_t n5ifIndex = CsmaIpv4Topology::AddIpv4CsmaNode (n5, channelc0,
+  uint32_t n5ifIndex = CsmaIpv4Topology::AddIpv4CsmaNetDevice (n5, channelc0,
                                          Eui48Address("10:54:23:54:23:53"));
 
   // Later, we add IP addresses.  

--- a/src/devices/csma/csma-ipv4-topology.cc	Mon Aug 13 12:08:01 2007 -0700
+++ b/src/devices/csma/csma-ipv4-topology.cc	Mon Aug 13 14:58:06 2007 -0700
@@ -35,19 +35,20 @@
 namespace ns3 {
 
 uint32_t
-CsmaIpv4Topology::AddIpv4CsmaNode(Ptr<Node> n1,
-                                  Ptr<CsmaChannel> ch,
-                                  Eui48Address addr)
+CsmaIpv4Topology::AddIpv4CsmaNetDevice(
+  Ptr<Node> node,
+  Ptr<CsmaChannel> channel,
+  Eui48Address addr)
 {
   Ptr<Queue> q = Queue::CreateDefault ();
 
   // assume full-duplex
-  Ptr<CsmaNetDevice> nd0 = Create<CsmaNetDevice> (n1, addr, 
-                                                  ns3::CsmaNetDevice::IP_ARP,
-                                                  true, true);
-  nd0->AddQueue(q);
-  nd0->Attach (ch);
-  return nd0->GetIfIndex ();
+  Ptr<CsmaNetDevice> nd = Create<CsmaNetDevice> (node, addr, 
+    ns3::CsmaNetDevice::IP_ARP, true, true);
+
+  nd->AddQueue(q);
+  nd->Attach (channel);
+  return nd->GetIfIndex ();
 }
 
 

--- a/src/devices/csma/csma-ipv4-topology.h	Mon Aug 13 12:08:01 2007 -0700
+++ b/src/devices/csma/csma-ipv4-topology.h	Mon Aug 13 14:58:06 2007 -0700
@@ -61,9 +61,9 @@
    * 
    * \return ifIndex of the device
    */
-  static uint32_t AddIpv4CsmaNode( Ptr<Node> n1,
-                                     Ptr<CsmaChannel> ch,
-                                     Eui48Address addr);
+  static uint32_t AddIpv4CsmaNetDevice(Ptr<Node> node,
+                                       Ptr<CsmaChannel> channel,
+                                       Eui48Address addr);
 
   /**
    * \param n1 Node to be attached to the Csma channel