How to Implement Network Flow Rule Placement in NS2

To implement the Network Flow Rule Placement using the simulation tool NS2 that encompass appending the flow rule placement and management mechanisms, usually for Software-Defined Networking (SDN) situations. It is describe how packets are managed by switches or routers within the network. To Implement Network Flow Rule Placement in NS2 tool stay in touch with us we  provide you with best guidance. Below we provide a simplified procedure to implement it in NS2:

Step-by-Step Process for Implementing Network Flow Rule Placement in NS2:

  1. Understand NS2 Basics and Flow Rule Concepts:
  • The simulation platform NS2, being a packet-level simulator that mainly manages the packets using standard routing protocols such as AODV, DSDV, or DSR. To execute the flow rules, we will require to change the packet forwarding mechanism.
  • Flow rules are normally discovered within SDN networks that a centralized controller (OpenFlow, for example) installs rules on switches to handle the packet forwarding.
  1. Identify the Network Layer for Rule Placement:
  • Flow rules impacts how packets are sent or dropped according to the criteria like source IP, destination IP, and protocol type.
  • In the simulating framework NS2, the network layer (IP layer) will be required to change to contain the logic for verifying and installing the flow rules before sending packets.
  1. Modify the Routing Module for Flow Rule Placement:
  • In NS2, routing is managed by the routing agent (e.g., AODV, DSDV). To execute the flow rules, alter the routing agent or make a custom one, which supports this flow rule placement.
  • The flow rules will install rely on the conditions like IP addresses or protocol types. If a matching rule exists then packets are forwarded consequently.
  1. Add Flow Table in C++ Code:
  • We want to execute a flow table in the routing agent. This table will hold flow rules, which dictate how packets are processed.
  • Evert rule can contain fields such as:
    • Source IP
    • Destination IP
    • Protocol type (e.g., TCP, UDP)
    • Action (forward, drop, etc.)
    • Priority
    • Timeout

In the C++ file (e.g., aodv.cc), make a structure for the flow table:

struct FlowRule {

int src_ip;

int dst_ip;

int protocol;

int action;  // 1 = forward, 0 = drop

int priority;

double timeout;

};

  • Make a flow table that holds numerous flow rules:

std::vector<FlowRule> flow_table;

  1. Implement Flow Rule Matching Logic:
  • The node should verify if it is a matching flow rule in the flow table, before forwarding a packet.
  • Execute a function, which observes a packet in the flow table and determines the action:

int checkFlowTable(Packet *p) {

hdr_ip *iph = hdr_ip::access(p);

for (auto rule : flow_table) {

if (iph->saddr() == rule.src_ip && iph->daddr() == rule.dst_ip && iph->proto() == rule.protocol) {

return rule.action;  // Return the action for this rule

}

}

return -1;  // No matching rule

}

  1. Define Flow Rule Installation:
  • Flow rules can install in react to particular events, like receiving a new flow or instructions from a centralized controller (in SDN scenarios).
  • We can execute a function to install new flow rules in the flow table:

void installFlowRule(int src_ip, int dst_ip, int protocol, int action, int priority, double timeout) {

FlowRule new_rule;

new_rule.src_ip = src_ip;

new_rule.dst_ip = dst_ip;

new_rule.protocol = protocol;

new_rule.action = action;

new_rule.priority = priority;

new_rule.timeout = timeout;

flow_table.push_back(new_rule);

}

  • In an SDN context, it would replicate the controller installing a rule depends on the network events.
  1. Packet Forwarding Based on Flow Rules:
  • Alter the existing packet forwarding logic to use the flow rules. If it is a matching rule, the packet is processed rely on the action stipulated in the rule (forward, drop, etc.).
  • In the forwarding function, contain the flow rule check:

void forwardPacket(Packet *p) {

int action = checkFlowTable(p);

if (action == 1) {

// Forward packet as usual

send(p, 0);

} else if (action == 0) {

// Drop the packet

drop(p);

} else {

// No rule, handle it with the default routing behavior

defaultForward(p);

}

}

  1. Add Flow Rule Expiration Logic (Optional):
  • Some flow rules may have a timeout, after that they expire and are removed from the table. Execute a function to periodically verify for expired rules and remove them.

void expireFlowRules() {

double current_time = Scheduler::instance().clock();

for (auto it = flow_table.begin(); it != flow_table.end(); ) {

if (current_time > it->timeout) {

it = flow_table.erase(it);  // Remove expired rule

} else {

++it;

}

}

}

  • This function can schedule periodically in the simulation to make certain that old rules are detached.
  1. Write OTcl Simulation Script:
  • Compose a simulation script in OTcl to setup the network, describe the nodes, and install flow rules.

Example OTcl script:

set ns [new Simulator]

set nf [open out.tr w]

$ns trace-all $nf

set node0 [$ns node]

set node1 [$ns node]

set node2 [$ns node]

# Configure flow rule for node0

$node0 installFlowRule 1.0.0.0 2.0.0.0 TCP 1 1 10.0 ;# Forward TCP packets from 1.0.0.0 to 2.0.0.0

$node0 installFlowRule 1.0.0.0 2.0.0.0 UDP 0 1 10.0 ;# Drop UDP packets from 1.0.0.0 to 2.0.0.0

# Run the simulation

$ns at 1.0 “generate_traffic”

$ns run

  • Now, we describe a flow rule for the node0 to send TCP packets among particular IPs and drop UDP packets.
  1. Compile and Run the Simulation:
  • After changing the C++ source files, recompile NS2 by running the below commands:

make clean

make

  • Then, we run the OTcl script:

ns your_script.tcl

  1. Analyze the Results:
  • We can use the trace file or NAM (Network Animator) to evaluate how flow rules are impacting the network behaviour. Check if the appropriate flow rules are being applied to packets, and verify the outcomes depending on the packet forwarding or dropping actions.

Key Components:

  • Flow Table: A data structure, which holds flow rules for packet managing.
  • Flow Rule Matching: Logic to verify if a packet matches a rule and take action.
  • Flow Rule Installation: Mechanism to install new flow rules whichever manually or through the controller logic.
  • Packet Forwarding: Changes to send or drop the packets rely on the flow rules.
  • Rule Expiration: Optional logic to eliminate outdated flow rules after a timeout.

We performed a structured approach on how to implement and analyse the network Flow Rule Placement, employing the NS2 simulating platform. If you want further details on this topic, we will provide in upcoming manual.