How to Begin Implement Hot Potato Routing in NS3

To implement Hot Potato Routing in NS3, it is also named as Deflection Routing, which is a routing strategy in which packets are immediately sent to the next node for preventing the queuing. It is specifically supportive within bufferless networks or if delays reduction is critical.

Here, we will guide you on how to start executing Hot Potato Routing in NS3 through following steps:

Steps to Begin Implement Hot Potato Routing in NS3

Step 1: Understand Hot Potato Routing

1. Key Features:
   • Immediate Forwarding: Packets are sent to any obtainable outgoing connection.
   • Avoidance of Congestion: When chosen link is engaged then packets are diverted to other connections.
   • No Buffering: Packets are never line up.
2. Applications:
   • Fault-tolerant and low-latency networks.
   • High-speed connects such as chip multiprocessors.
   • Optical networks including bufferless nodes.

Step 2: Set Up NS3 Environment

1. Create a Protocol Directory:
   • Make a protocol directory in src/, for instance src/hot-potato-routing/.
2. Add Necessary Files:
   • hot-potato-routing-helper.h and hot-potato-routing-helper.cc: Helper classes.
   • hot-potato-routing-protocol.h: Header file for dynamic routing protocol.
   • hot-potato-routing-protocol.cc: It is an execution file.
3. Update Build System:
   • With the new module, we can change the wscript in src/.

Step 3: Design Hot Potato Routing Protocol

Define the Protocol Class

To execute hot potato routing logic, we need to prolong the Ipv4RoutingProtocol class.

Header File (hot-potato-routing-protocol.h)

#include “ns3/ipv4-routing-protocol.h”

#include “ns3/socket.h”

#include <map>

#include <vector>

class HotPotatoRoutingProtocol : public ns3::Ipv4RoutingProtocol {

public:

static ns3::TypeId GetTypeId (void);

HotPotatoRoutingProtocol ();

virtual ~HotPotatoRoutingProtocol ();

// Override Ipv4RoutingProtocol methods

virtual ns3::Ptr<ns3::Ipv4Route> RouteOutput (

ns3::Ptr<const ns3::Packet> packet,

const ns3::Ipv4Header &header,

ns3::Ptr<ns3::NetDevice> oif,

ns3::Socket::SocketErrno &sockerr);

virtual bool RouteInput (

ns3::Ptr<const ns3::Packet> packet,

const ns3::Ipv4Header &header,

ns3::Ptr<const ns3::NetDevice> idev,

ns3::UnicastForwardCallback ucb,

ns3::MulticastForwardCallback mcb,

ns3::LocalDeliverCallback lcb,

ns3::ErrorCallback ecb);

void AddNeighbor (ns3::Ipv4Address neighbor, uint32_t interface);

private:

struct NeighborEntry {

ns3::Ipv4Address address;

uint32_t interface;

};

std::vector<NeighborEntry> m_neighbors; // List of neighbors

};

Implement Core Functions

Neighbor Management

Now, save the collection of neighbors which is available.

void HotPotatoRoutingProtocol::AddNeighbor (ns3::Ipv4Address neighbor, uint32_t interface) {

NeighborEntry entry = {neighbor, interface};

m_neighbors.push_back(entry);

}

Packet Forwarding

Execute the hot potato logic for transmitting the packets to any obtainable neighbor.

ns3::Ptr<ns3::Ipv4Route> HotPotatoRoutingProtocol::RouteOutput (

ns3::Ptr<const ns3::Packet> packet,

const ns3::Ipv4Header &header,

ns3::Ptr<ns3::NetDevice> oif,

ns3::Socket::SocketErrno &sockerr) {

// Select a random neighbor to forward the packet

if (!m_neighbors.empty()) {

size_t index = rand() % m_neighbors.size();

NeighborEntry selectedNeighbor = m_neighbors[index];

ns3::Ptr<ns3::Ipv4Route> route = ns3::Create<ns3::Ipv4Route> ();

route->SetGateway(selectedNeighbor.address);

route->SetOutputDevice(oif);

return route;

}

sockerr = ns3::Socket::ERROR_NOROUTETOHOST;

return nullptr;

}

Handle Incoming Packets

Send incoming packets to any available link or locally distribute.

bool HotPotatoRoutingProtocol::RouteInput (

ns3::Ptr<const ns3::Packet> packet,

const ns3::Ipv4Header &header,

ns3::Ptr<const ns3::NetDevice> idev,

ns3::UnicastForwardCallback ucb,

ns3::MulticastForwardCallback mcb,

ns3::LocalDeliverCallback lcb,

ns3::ErrorCallback ecb) {

if (header.GetDestination() == m_selfAddress) {

lcb(packet, header, 0); // Deliver locally

return true;

}

if (!m_neighbors.empty()) {

size_t index = rand() % m_neighbors.size();

NeighborEntry selectedNeighbor = m_neighbors[index];

ucb(packet, header, selectedNeighbor.address, selectedNeighbor.interface);

return true;

}

ecb(packet, header, ns3::Ipv4Header::DESTINATION_UNREACHABLE);

return false;

}

Step 4: Write a Helper Class

Enable incorporation including simulations to create a helper class.

#include “hot-potato-routing-protocol.h”

class HotPotatoRoutingHelper {

public:

void Install (ns3::NodeContainer nodes) {

for (auto it = nodes.Begin(); it != nodes.End(); ++it) {

ns3::Ptr<HotPotatoRoutingProtocol> protocol = ns3::CreateObject<HotPotatoRoutingProtocol>();

(*it)->AggregateObject(protocol);

}

}

};

Step 5: Write a Simulation Script

Example Simulation Script

#include “ns3/core-module.h”

#include “ns3/network-module.h”

#include “ns3/internet-module.h”

#include “hot-potato-routing-helper.h”

using namespace ns3;

int main (int argc, char *argv[]) {

NodeContainer nodes;

nodes.Create (4);

InternetStackHelper stack;

stack.Install (nodes);

HotPotatoRoutingHelper hotPotatoHelper;

hotPotatoHelper.Install(nodes);

PointToPointHelper p2p;

p2p.SetDeviceAttribute (“DataRate”, StringValue (“10Mbps”));

p2p.SetChannelAttribute (“Delay”, StringValue (“2ms”));

p2p.Install (nodes.Get(0), nodes.Get(1));

p2p.Install (nodes.Get(0), nodes.Get(2));

p2p.Install (nodes.Get(1), nodes.Get(3));

p2p.Install (nodes.Get(2), nodes.Get(3));

Simulator::Run ();

Simulator::Destroy ();

return 0;

}

Step 6: Compile and Run

1. Build the Protocol:

./waf configure

./waf build

1. Run the Simulation:

./waf –run your-script

Step 7: Analyze and Extend

1. Tracing:
   • Examine the behaviour of packet forwarding with the support of AsciiTraceHelper or PcapHelper.
2. Enhancements:
   • Execute a fallback approach for deadlocks.
   • Add load balancing for enhancing the path utilization.

Detailed step-by-step methods for executing and examining the Hot Potato Routing have been outlined using NS3 tool. Additional information will be included in the forthcoming manual.