First, note that the @code{Receive ()} function has a matching signature

First, note that the @code{Receive ()} function has a matching signature

to the ReceiveCallback in the @code{class Node}.  This function pointer

to the ReceiveCallback in the @code{class Node}.  This function pointer

@code{AddInterface ()} is called.  The actual registration is done

@code{AddInterface ()} is called.  The actual registration is done

with a statement such as:

with a statement such as:

follows:

follows:

  p2pNodes.Create (2);

  p2pNodes.Create (2);

@end verbatim

@end verbatim

part of the bus (CSMA) network.  First, we just instantiate the container

part of the bus (CSMA) network.  First, we just instantiate the container

object itself.  

object itself.  

channels, and the next lines introduce them.  The @code{CsmaHelper} works just

channels, and the next lines introduce them.  The @code{CsmaHelper} works just

like a @code{PointToPointHelper}, but it creates and connects CSMA devices and

like a @code{PointToPointHelper}, but it creates and connects CSMA devices and

channels.  In the case of a CSMA device and channel pair, notice that the data

channels.  In the case of a CSMA device and channel pair, notice that the data

This is because a real CSMA network does not allow one to mix, for example, 

This is because a real CSMA network does not allow one to mix, for example, 

10Base-T and 100Base-T devices on a given channel.  We first set the data rate

10Base-T and 100Base-T devices on a given channel.  We first set the data rate

to 100 megabits per second, and then set the speed-of-light delay of the channel

to 100 megabits per second, and then set the speed-of-light delay of the channel

Recall that the @code{csmaNodes NodeContainer} contains one of the 

Recall that the @code{csmaNodes NodeContainer} contains one of the 

nodes created for the point-to-point network and @code{nCsma} ``extra'' nodes. 

nodes created for the point-to-point network and @code{nCsma} ``extra'' nodes. 

What we want to get at is the last of the ``extra'' nodes.  The zeroth entry of

What we want to get at is the last of the ``extra'' nodes.  The zeroth entry of

way to think of this, then, is if we create one ``extra'' CSMA node, then it

way to think of this, then, is if we create one ``extra'' CSMA node, then it

if we create @code{nCsma} ``extra'' nodes the last one will be at index 

if we create @code{nCsma} ``extra'' nodes the last one will be at index 

@code{nCsma}.  You see this exhibited in the @code{Get} of the first line of 

@code{nCsma}.  You see this exhibited in the @code{Get} of the first line of 

code.

code.

Now look at @code{second-1-0.pcap} and @code{second-1-1.pcap}.  The former is

Now look at @code{second-1-0.pcap} and @code{second-1-1.pcap}.  The former is

the pcap trace for device zero on node one and the latter is the trace file 

the pcap trace for device zero on node one and the latter is the trace file 

the start of the section, you will see that node one is the node that has

the start of the section, you will see that node one is the node that has

both a point-to-point device and a CSMA device, so we should expect two pcap

both a point-to-point device and a CSMA device, so we should expect two pcap

traces for that node.

traces for that node.

  ~/repos/ns-3-dev >

  ~/repos/ns-3-dev >

@end verbatim

@end verbatim

though.  The bus network needs @code{ARP}, the Address Resolution Protocol.

though.  The bus network needs @code{ARP}, the Address Resolution Protocol.

The node knows it needs to send the packet to IP address 10.1.2.4, but it

The node knows it needs to send the packet to IP address 10.1.2.4, but it

doesn't know the MAC address of the corresponding node.  It broadcasts on the

doesn't know the MAC address of the corresponding node.  It broadcasts on the

  ~/repos/ns-3-dev >

  ~/repos/ns-3-dev >

@end verbatim

@end verbatim

the ARP exchange we just explained.  The third packet is the echo packet 

the ARP exchange we just explained.  The third packet is the echo packet 

being delivered to its final destination.

being delivered to its final destination.

  p2pDevices = pointToPoint.Install (p2pNodes);

  p2pDevices = pointToPoint.Install (p2pNodes);

@end verbatim

@end verbatim

part of the bus (CSMA) network.

part of the bus (CSMA) network.

@verbatim

@verbatim

Now, we are going to add mobility models.  We want the STA nodes to be mobile,

Now, we are going to add mobility models.  We want the STA nodes to be mobile,

wandering around inside a bounding box, and we want to make the AP node 

wandering around inside a bounding box, and we want to make the AP node 

stationary.  We use the @code{MobilityHelper} to make this easy for us.

stationary.  We use the @code{MobilityHelper} to make this easy for us.

controlling the ``position allocator'' functionality.

controlling the ``position allocator'' functionality.

@verbatim

@verbatim

place the STA nodes.  Feel free to explore the Doxygen for class 

place the STA nodes.  Feel free to explore the Doxygen for class 

@code{ns3::GridPositionAllocator} to see exactly what is being done.

@code{ns3::GridPositionAllocator} to see exactly what is being done.

how to move.  We choose the @code{RandomWalk2dMobilityModel} which has the 

how to move.  We choose the @code{RandomWalk2dMobilityModel} which has the 

nodes move in a random direction at a random speed around inside a bounding 

nodes move in a random direction at a random speed around inside a bounding 

box.

box.

@code{Ipv4AddressHelper} to assign IP addresses to our device interfaces.

@code{Ipv4AddressHelper} to assign IP addresses to our device interfaces.

First we use the network 10.1.1.0 to create the two addresses needed for our

First we use the network 10.1.1.0 to create the two addresses needed for our

two point-to-point devices.  Then we use network 10.1.2.0 to assign addresses

two point-to-point devices.  Then we use network 10.1.2.0 to assign addresses

both the STA devices and the AP on the wireless network.

both the STA devices and the AP on the wireless network.

@verbatim

@verbatim

  clientApps.Stop (Seconds (10.0));

  clientApps.Stop (Seconds (10.0));

@end verbatim

@end verbatim

just as we did in the @code{second.cc} example script.

just as we did in the @code{second.cc} example script.

@verbatim

@verbatim

@cindex Channel

@cindex Channel

In the real world, one can connect a computer to a network.  Often the media

In the real world, one can connect a computer to a network.  Often the media

you connect your Ethernet cable to the plug in the wall, you are connecting 

you connect your Ethernet cable to the plug in the wall, you are connecting 

your computer to an Ethernet communication channel.  In the simulated world

your computer to an Ethernet communication channel.  In the simulated world

of @command{ns-3}, one connects a @code{Node} to an object representing a

of @command{ns-3}, one connects a @code{Node} to an object representing a

by the @code{PointToPointHelper}, the attributes previously set in the helper

by the @code{PointToPointHelper}, the attributes previously set in the helper

are used to initialize the corresponding attributes in the created objects.

are used to initialize the corresponding attributes in the created objects.

two nodes, each with an installed point-to-point net device and a 

two nodes, each with an installed point-to-point net device and a 

point-to-point channel between them.  Both devices will be configured to 

point-to-point channel between them.  Both devices will be configured to 

transmit data at five megabits per second over the channel which has a two 

transmit data at five megabits per second over the channel which has a two 

Recall that we used an @code{Ipv4InterfaceContainer} to keep track of the IP 

Recall that we used an @code{Ipv4InterfaceContainer} to keep track of the IP 

addresses we assigned to our devices.  The zeroth interface in the 

addresses we assigned to our devices.  The zeroth interface in the 

zeroth node in the @code{nodes} container.  The first interface in the 

zeroth node in the @code{nodes} container.  The first interface in the 

in the @code{nodes} container.  So, in the first line of code (from above), we

in the @code{nodes} container.  So, in the first line of code (from above), we

are creating the helper and telling it so set the remote address of the client

are creating the helper and telling it so set the remote address of the client

to be  the IP address assigned to the node on which the server resides.  We 

to be  the IP address assigned to the node on which the server resides.  We 

@end verbatim

@end verbatim

You can now run the example (note that if you build your program in the scratch

You can now run the example (note that if you build your program in the scratch

@verbatim

@verbatim

  ~/repos/ns-3-dev > ./waf --run scratch/first

  ~/repos/ns-3-dev > ./waf --run scratch/first

@cindex Channel

@cindex Channel

In the real world, one can connect a computer to a network.  Often the media

In the real world, one can connect a computer to a network.  Often the media

you connect your Ethernet cable to the plug in the wall, you are connecting 

you connect your Ethernet cable to the plug in the wall, you are connecting 

your computer to an Ethernet communication channel.  In the simulated world

your computer to an Ethernet communication channel.  In the simulated world

of ns-3 one connects a @code{Node} to an object representing a

of ns-3 one connects a @code{Node} to an object representing a

The rationale for this explicit division is to allow users to attach new

The rationale for this explicit division is to allow users to attach new

types of sinks to existing tracing sources, without requiring editing and 

types of sinks to existing tracing sources, without requiring editing and 

a user could define a new tracing sink in her script and attach it to an 

a user could define a new tracing sink in her script and attach it to an 

existing tracing source defined in the simulation core by editing only the 

existing tracing source defined in the simulation core by editing only the 

user script.

user script.

the final segments of the ``trace path'' which are @code{TxQueue/Enqueue}.

the final segments of the ``trace path'' which are @code{TxQueue/Enqueue}.

The remaining lines in the trace should be fairly intuitive.  References 03-04

The remaining lines in the trace should be fairly intuitive.  References 03-04

References 05-07 show that the packet has an IP version four header and has

References 05-07 show that the packet has an IP version four header and has

originated from IP address 10.1.1.1 and is destined for 10.1.1.2.  References

originated from IP address 10.1.1.1 and is destined for 10.1.1.2.  References

08-09 show that this packet has a UDP header and, finally, reference 10 shows

08-09 show that this packet has a UDP header and, finally, reference 10 shows

In our example script, we will eventually see files named ``first-0-0.pcap'' 

In our example script, we will eventually see files named ``first-0-0.pcap'' 

and ``first.1-0.pcap'' which are the pcap traces for node 0-device 0 and 

and ``first.1-0.pcap'' which are the pcap traces for node 0-device 0 and 

Once you have added the line of code to enable pcap tracing, you can run the

Once you have added the line of code to enable pcap tracing, you can run the

script in the usual way:

script in the usual way: