To implement a custom MAC frame design in ns3 requires a creation of MAC layer protocol whether it’s new or altering an existing one with your certain frame structure.
Let’s take a look at the step-by-step implementation guide on how to design a frame in ns3:
Step-by-Step Implementation:
Step 1: Define Your MAC Frame Structure
First, we have to describe the MAC frame based on our preferences by stating the fields and its sizes.
For instance, a simple custom MAC frame might look like this:
| Field | Size (bits) |
| Preamble | 8 |
| Frame Control | 16 |
| Duration/ID | 16 |
| Address 1 | 48 |
| Address 2 | 48 |
| Address 3 | 48 |
| Sequence Control | 16 |
| Address 4 | 48 (optional) |
| Payload | variable |
| FCS | 32 |
Step 2: Create a Custom MAC Header
Second, we have to describe a new MAC header which contains the fields you specified and creating a new header class derived from the header.
Create a new header file, e.g., my-mac-header.h:
#ifndef MY_MAC_HEADER_H
#define MY_MAC_HEADER_H
#include “ns3/header.h”
#include “ns3/address.h”
namespace ns3 {
class MyMacHeader : public Header
{
public:
MyMacHeader ();
virtual ~MyMacHeader ();
void SetAddresses (Mac48Address src, Mac48Address dst);
Mac48Address GetSource () const;
Mac48Address GetDestination () const;
static TypeId GetTypeId (void);
virtual TypeId GetInstanceTypeId (void) const;
virtual void Print (std::ostream &os) const;
virtual uint32_t GetSerializedSize (void) const;
virtual void Serialize (Buffer::Iterator start) const;
virtual uint32_t Deserialize (Buffer::Iterator start);
private:
Mac48Address m_src;
Mac48Address m_dst;
uint16_t m_duration;
uint16_t m_sequence;
uint32_t m_fcs;
};
} // namespace ns3
#endif // MY_MAC_HEADER_H
Create the implementation file, e.g., my-mac-header.cc:
#include “my-mac-header.h”
#include “ns3/address-utils.h”
#include “ns3/packet.h”
namespace ns3 {
NS_OBJECT_ENSURE_REGISTERED (MyMacHeader);
TypeId
MyMacHeader::GetTypeId (void)
{
static TypeId tid = TypeId (“ns3::MyMacHeader”)
.SetParent<Header> ()
.SetGroupName (“Network”)
.AddConstructor<MyMacHeader> ();
return tid;
}
TypeId
MyMacHeader::GetInstanceTypeId (void) const
{
return GetTypeId ();
}
MyMacHeader::MyMacHeader ()
: m_duration (0),
m_sequence (0),
m_fcs (0)
{
}
MyMacHeader::~MyMacHeader ()
{
}
void
MyMacHeader::SetAddresses (Mac48Address src, Mac48Address dst)
{
m_src = src;
m_dst = dst;
}
Mac48Address
MyMacHeader::GetSource () const
{
return m_src;
}
Mac48Address
MyMacHeader::GetDestination () const
{
return m_dst;
}
void
MyMacHeader::Print (std::ostream &os) const
{
os << “Src: ” << m_src << “, Dst: ” << m_dst
<< “, Duration: ” << m_duration << “, Sequence: ” << m_sequence
<< “, FCS: ” << m_fcs;
}
uint32_t
MyMacHeader::GetSerializedSize (void) const
{
return 2 + 2 + 6 + 6 + 4; // duration, sequence, src, dst, FCS
}
void
MyMacHeader::Serialize (Buffer::Iterator start) const
{
start.WriteHtonU16 (m_duration);
WriteTo (start, m_src);
WriteTo (start, m_dst);
start.WriteHtonU16 (m_sequence);
start.WriteHtonU32 (m_fcs);
}
uint32_t
MyMacHeader::Deserialize (Buffer::Iterator start)
{
m_duration = start.ReadNtohU16 ();
ReadFrom (start, m_src);
ReadFrom (start, m_dst);
m_sequence = start.ReadNtohU16 ();
m_fcs = start.ReadNtohU32 ();
return GetSerializedSize ();
}
} // namespace ns3
Step 3: Integrate the Custom Header into a MAC Protocol
To use this header, we need to build or modify a MAC protocol class by integrating your custom MAC header into a MAC protocol. Here, we will demonstrate how to modify an existing simple MAC protocol for demonstration.
- Create a new MAC protocol file, e.g., my-mac-protocol.h:
#ifndef MY_MAC_PROTOCOL_H
#define MY_MAC_PROTOCOL_H
#include “ns3/net-device.h”
#include “ns3/packet.h”
#include “ns3/nstime.h”
#include “my-mac-header.h”
namespace ns3 {
class MyMacProtocol : public NetDevice
{
public:
static TypeId GetTypeId (void);
MyMacProtocol ();
virtual ~MyMacProtocol ();
void SendPacket (Ptr<Packet> packet, Mac48Address src, Mac48Address dst);
// Inherited from NetDevice
virtual void SetIfIndex (const uint32_t index);
virtual uint32_t GetIfIndex (void) const;
virtual Ptr<Channel> GetChannel (void) const;
virtual void SetAddress (Address address);
virtual Address GetAddress (void) const;
virtual bool SetMtu (const uint16_t mtu);
virtual uint16_t GetMtu (void) const;
virtual bool IsLinkUp (void) const;
virtual void AddLinkChangeCallback (Callback<void> callback);
virtual bool IsBroadcast (void) const;
virtual Address GetBroadcast (void) const;
virtual bool Send (Ptr<Packet> packet, const Address &dest, uint16_t protocolNumber);
virtual bool SendFrom (Ptr<Packet> packet, const Address &source, const Address &dest, uint16_t protocolNumber);
virtual Ptr<Node> GetNode (void) const;
virtual void SetNode (Ptr<Node> node);
virtual bool NeedsArp (void) const;
virtual void SetReceiveCallback (NetDevice::ReceiveCallback cb);
virtual void DoDispose (void);
private:
void ReceivePacket (Ptr<Packet> packet);
Ptr<Channel> m_channel;
Ptr<Node> m_node;
Address m_address;
NetDevice::ReceiveCallback m_receiveCallback;
};
} // namespace ns3
#endif // MY_MAC_PROTOCOL_H
Create the implementation file, e.g., my-mac-protocol.cc:
#include “my-mac-protocol.h”
#include “ns3/log.h”
#include “ns3/simulator.h”
namespace ns3 {
NS_LOG_COMPONENT_DEFINE (“MyMacProtocol”);
NS_OBJECT_ENSURE_REGISTERED (MyMacProtocol);
TypeId
MyMacProtocol::GetTypeId (void)
{
static TypeId tid = TypeId (“ns3::MyMacProtocol”)
.SetParent<NetDevice> ()
.SetGroupName (“Network”)
.AddConstructor<MyMacProtocol> ();
return tid;
}
MyMacProtocol::MyMacProtocol ()
{
}
MyMacProtocol::~MyMacProtocol ()
{
}
void
MyMacProtocol::SetIfIndex (const uint32_t index)
{
}
uint32_t
MyMacProtocol::GetIfIndex (void) const
{
return 0;
}
Ptr<Channel>
MyMacProtocol::GetChannel (void) const
{
return m_channel;
}
void
MyMacProtocol::SetAddress (Address address)
{
m_address = address;
}
Address
MyMacProtocol::GetAddress (void) const
{
return m_address;
}
bool
MyMacProtocol::SetMtu (const uint16_t mtu)
{
return true;
}
uint16_t
MyMacProtocol::GetMtu (void) const
{
return 1500;
}
bool
MyMacProtocol::IsLinkUp (void) const
{
return true;
}
void
MyMacProtocol::AddLinkChangeCallback (Callback<void> callback)
{
}
bool
MyMacProtocol::IsBroadcast (void) const
{
return true;
}
Address
MyMacProtocol::GetBroadcast (void) const
{
return Mac48Address::GetBroadcast ();
}
bool
MyMacProtocol::Send (Ptr<Packet> packet, const Address &dest, uint16_t protocolNumber)
{
MyMacHeader header;
header.SetAddresses (Mac48Address::ConvertFrom (m_address), Mac48Address::ConvertFrom (dest));
packet->AddHeader (header);
NS_LOG_INFO (“Sending packet with custom MAC header”);
return true;
}
bool
MyMacProtocol::SendFrom (Ptr<Packet> packet, const Address &source, const Address &dest, uint16_t protocolNumber)
{
return Send (packet, dest, protocolNumber);
}
Ptr<Node>
MyMacProtocol::GetNode (void) const
{
return m_node;
}
void
MyMacProtocol::SetNode (Ptr<Node> node)
{
m_node = node;
}
bool
MyMacProtocol::NeedsArp (void) const
{
return true;
}
void
MyMacProtocol::SetReceiveCallback (NetDevice::ReceiveCallback cb)
{
m_receiveCallback = cb;
}
void
MyMacProtocol::DoDispose (void)
{
m_channel = 0;
m_node = 0;
NetDevice::DoDispose ();
}
void
MyMacProtocol::ReceivePacket (Ptr<Packet> packet)
{
MyMacHeader header;
packet->RemoveHeader (header);
NS_LOG_INFO (“Received packet with custom MAC header”);
if (!m_receiveCallback.IsNull ())
{
m_receiveCallback (this, packet, 0, header.GetSource ());
}
}
} // namespace ns3
Step 4: Integrate Your Custom MAC Protocol into a Simulation
Use your custom MAC protocol in an ns3 simulation script.
- Include the necessary headers:
#include “ns3/core-module.h”
#include “ns3/network-module.h”
#include “ns3/internet-module.h”
#include “my-mac-protocol.h”
- 2. Create and configure the nodes and devices:
using namespace ns3;
int main (int argc, char *argv[])
{
NodeContainer nodes;
nodes.Create (2);
// Install Internet stack
InternetStackHelper internet;
internet.Install (nodes);
// Create and install custom MAC protocol on nodes
Ptr<MyMacProtocol> mac1 = CreateObject<MyMacProtocol> ();
Ptr<MyMacProtocol> mac2 = CreateObject<MyMacProtocol> ();
nodes.Get (0)->AddDevice (mac1);
nodes.Get (1)->AddDevice (mac2);
// Set addresses
mac1->SetAddress (Mac48Address::Allocate ());
mac2->SetAddress (Mac48Address::Allocate ());
// Assign IP addresses
Ipv4AddressHelper ipv4;
ipv4.SetBase (“10.1.1.0”, “255.255.255.0”);
Ipv4InterfaceContainer interfaces = ipv4.Assign (NetDeviceContainer (mac1, mac2));
// Set up applications
UdpEchoServerHelper echoServer (9);
ApplicationContainer serverApps = echoServer.Install (nodes.Get (1));
serverApps.Start (Seconds (1.0));
serverApps.Stop (Seconds (10.0));
UdpEchoClientHelper echoClient (interfaces.GetAddress (1), 9);
echoClient.SetAttribute (“MaxPackets”, UintegerValue (1));
echoClient.SetAttribute (“Interval”, TimeValue (Seconds (1.0)));
echoClient.SetAttribute (“PacketSize”, UintegerValue (1024));
ApplicationContainer clientApps = echoClient.Install (nodes.Get (0));
clientApps.Start (Seconds (2.0));
clientApps.Stop (Seconds (10.0));
Simulator::Run ();
Simulator::Destroy ();
return 0;
}
Step 5: Compile and Run Your Simulation
Lastly, we have to compile your ns3 simulation script and run the simulation.
Example Compilation Command:
./waf configure
./waf build
./waf –run my-mac-simulation
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