How to Begin Implement Benes Network Routing in NS3

To begin a Benes network is a kind of multistage interconnection network frequently used in switching systems for its rearrangeable non-blocking properties. Apply the Benes network routing in NS3 has includes the making a network topology which implement the Benes network and routing procedures to use the properties.

Here’s how you can begin implementing Benes Network Routing in NS-3:

Steps to Begin Implement Benes Network Routing in NS3

Step 1: Understand Benes Network

1. Key Characteristics:
   • A Benes network is a multistage network through 2×n−12 \times n – 12×n−1 stages for N=2kN = 2^kN=2k inputs/outputs.
   • Rearrange able the non-blocking property: It can route some variation of inputs to outputs.
   • Recursively designed by butterfly networks for the front and back.
2. Routing Rules:
   • Plot the input ports to output ports using the central stages for rearrangement.
   • Route according to the binary illustrations of the input and output directories.

Step 2: Set Up NS-3

1. Install NS-3:

git clone https://gitlab.com/nsnam/ns-3-dev.git

cd ns-3-dev

./ns3 configure –enable-examples –enable-tests

./ns3 build

1. Verify Installation: Validate with a basic script:

./ns3 run examples/tutorial/first

Step 3: Plan the Benes Network Topology

1. Network Structure:
   • Every node has corresponds to a switch.
   • Numerous phases in which every stage has N/2N/2N/2 switches.
   • Communicate the steps form the Benes network.
2. Workflow:
   • Describe the function for generate a Benes network.
   • Apply the routing logic to traverse the network according to the source and destination directories.

Step 4: Implement Benes Network Routing

Step 4.1: Define the Protocol Class

Encompass the Ipv4RoutingProtocol class:

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

#include <vector>

#include <map>

using namespace ns3;

class BenesRouting : public Ipv4RoutingProtocol {

public:

static TypeId GetTypeId(void);

BenesRouting();

virtual ~BenesRouting();

virtual Ptr<Ipv4Route> RouteOutput(Ptr<Packet> packet, const Ipv4Header &header,

Ptr<NetDevice> oif, Socket::SocketErrno &sockerr) override;

virtual bool RouteInput(Ptr<const Packet> packet, const Ipv4Header &header,

Ptr<const NetDevice> idev, UnicastForwardCallback ucb,

MulticastForwardCallback mcb, LocalDeliverCallback lcb,

ErrorCallback ecb) override;

void BuildBenesNetwork(uint32_t size);

void AddRoute(Ipv4Address src, Ipv4Address dst);

private:

struct Switch {

uint32_t stage;

uint32_t index;

std::vector<Ipv4Address> connections;

};

uint32_t m_size; // Number of input/output ports

std::vector<std::vector<Switch>> m_stages; // Benes network stages

std::map<Ipv4Address, Ipv4Address> m_routingTable; // Src -> Dst mapping

Ipv4Address GetNextHop(Ipv4Address current, Ipv4Address destination);

};

Step 4.2: Construct the Benes Network

• Network Initialization: Create a multistage topology.

void BenesRouting::BuildBenesNetwork(uint32_t size) {

m_size = size;

uint32_t stages = 2 * log2(size) – 1;

m_stages.resize(stages);

for (uint32_t stage = 0; stage < stages; ++stage) {

uint32_t numSwitches = size / 2;

for (uint32_t i = 0; i < numSwitches; ++i) {

Switch sw = {stage, i, {}};

m_stages[stage].push_back(sw);

}

}

// Connect switches between stages (specific to Benes topology)

for (uint32_t stage = 0; stage < stages – 1; ++stage) {

for (uint32_t i = 0; i < m_stages[stage].size(); ++i) {

// Forward connections

m_stages[stage][i].connections.push_back(m_stages[stage + 1][i].index);

m_stages[stage][i].connections.push_back(m_stages[stage + 1][i ^ 1].index);

}

}

}

Step 4.3: Implement Routing Logic

• Routing Table Setup: Increase the predefined source-to-destination mappings.

void BenesRouting::AddRoute(Ipv4Address src, Ipv4Address dst) {

m_routingTable[src] = dst;

}

• Next Hop Computation: Define the next hop according to the Benes network phases.

Ipv4Address BenesRouting::GetNextHop(Ipv4Address current, Ipv4Address destination) {

// Implement routing logic based on source and destination binary representations

auto srcIdx = std::distance(m_routingTable.begin(), m_routingTable.find(current));

auto dstIdx = std::distance(m_routingTable.begin(), m_routingTable.find(destination));

// Traverse stages of Benes network

for (uint32_t stage = 0; stage < m_stages.size(); ++stage) {

if (srcIdx < dstIdx) {

srcIdx = (srcIdx + dstIdx) / 2; // Simplified transition logic

} else {

dstIdx = (srcIdx + dstIdx) / 2;

}

}

return m_stages[srcIdx][dstIdx].connections[0]; // Return the first connected address

}

• Route Output: Use the routing table and Benes logic for establish the routes.

Ptr<Ipv4Route> BenesRouting::RouteOutput(Ptr<Packet> packet, const Ipv4Header &header,

Ptr<NetDevice> oif, Socket::SocketErrno &sockerr) {

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

Ipv4Address nextHop = GetNextHop(header.GetSource(), header.GetDestination());

if (nextHop.IsBroadcast() || nextHop.IsAny()) {

sockerr = Socket::ERROR_NOROUTETOHOST;

return nullptr;

}

route->SetDestination(header.GetDestination());

route->SetGateway(nextHop);

route->SetOutputDevice(oif);

return route;

}

• Route Input: Sending the packets through the Benes network.

bool BenesRouting::RouteInput(Ptr<const Packet> packet, const Ipv4Header &header,

Ptr<const NetDevice> idev, UnicastForwardCallback ucb,

MulticastForwardCallback mcb, LocalDeliverCallback lcb,

ErrorCallback ecb) {

if (header.GetDestination() == GetNode()->GetObject<Ipv4>()->GetAddress(1, 0).GetLocal()) {

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

return true;

}

Ipv4Address nextHop = GetNextHop(header.GetSource(), header.GetDestination());

if (!nextHop.IsBroadcast() && !nextHop.IsAny()) {

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

route->SetDestination(header.GetDestination());

route->SetGateway(nextHop);

ucb(route, packet, header);

return true;

}

return false;

}

Step 5: Register the Protocol

Save the protocol through NS-3’s TypeId system:

TypeId BenesRouting::GetTypeId(void) {

static TypeId tid = TypeId(“ns3::BenesRouting”)

.SetParent<Ipv4RoutingProtocol>()

.SetGroupName(“Internet”)

.AddConstructor<BenesRouting>();

return tid;

}

Step 6: Integrate into a Simulation

1. Simulation Script Example:

#include “ns3/internet-stack-helper.h”

#include “ns3/benes-routing.h”

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

NodeContainer nodes;

nodes.Create(8); // Number of nodes in the Benes network

Ptr<BenesRouting> benesRouting = CreateObject<BenesRouting>();

benesRouting->BuildBenesNetwork(8); // Build an 8-port Benes network

for (uint32_t i = 0; i < nodes.GetN(); ++i) {

Ipv4Address src = nodes.Get(i)->GetObject<Ipv4>()->GetAddress(1, 0);

Ipv4Address dst = nodes.Get((i + 1) % nodes.GetN())->GetObject<Ipv4>()->GetAddress(1, 0);

benesRouting->AddRoute(src, dst);

}

InternetStackHelper stack;

stack.SetRoutingHelper(benesRouting);

stack.Install(nodes);

Simulator::Run();

Simulator::Destroy();

return 0;

}

Step 7: Test and Debug

1. Enable Logging:

export NS_LOG=”BenesRouting=level_all|prefix_time”

./ns3 run my-simulation

1. Verify Results:
   • Assure the packets follow the Benes routing logic.
   • Experiment against the Benes network topology.

Step 8: Extend and Optimize

1. Enhancements:
   • Enhance the capabilities for dynamic routing.
   • Incorporate the parameter metrics such as delay or bandwidth for better routing.
2. Performance Testing:
   • Validate with larger network sizes.
   • Calculate the scalability and packet delivery for effectiveness.

Finally, we discussed here about procedures to execution, sample snippets for the Benes network routing through ns3 tool. Here we also support further information about Benes routing.