How to Implement Link Aggregation Control Protocol in ns2

To implement the Link Aggregation Control Protocol (LACP) within NS2, we will require to simulate the situation in which several physical links among two nodes that are combined into the unique logical link. This protocol normally used in the wired networks and is not a portion of the simulations NS2’s default protocol stack. Thus we will want to simulate the performance of this protocol by tailoring how the links are handled among the nodes in the simulation tool NS2.

Overview of Link Aggregation Control Protocol (LACP):

This protocol that permits to bundle numerous physical interfaces to maximize the bandwidth and it give redundancy. The idea is to mimic the traffic load balancing and failover among several links.

Steps to Implement LACP in NS2

  1. Understand the Behaviour of LACP

LACP aggregates numerous physical links into single logical link that includes:

  • Load balancing: Dispensing these packets over several physical links.
  • Redundancy: If single physical link fails then the traffic is rerouted across other active links.

We can replicate this performance by making several links among the two nodes and also using the custom logic to simulate the failover and balance the load.

  1. Modify NS2 to Simulate LACP

To mimic LACP in NS2, we can change the path that simulator manages the links and packet distribution over those links.

Key points for implementation:

  • Make a several links among the two nodes.
  • We can write a custom script to handle the load balancing and redundancy among the links.
  1. TCL Script Example for Simulating LACP in NS2

Given below is an instance TCL script to mimic link aggregation among the two nodes using several physical links:

# Create a new simulator instance

set ns [new Simulator]

# Open trace file for output

set tracefile [open “lacp.tr” w]

$ns trace-all $tracefile

# Open NAM file for visualization

set namfile [open “lacp.nam” w]

$ns namtrace-all $namfile

# Define the nodes

set node1 [$ns node]

set node2 [$ns node]

# Create multiple duplex links between node1 and node2 (to simulate LACP)

$ns duplex-link $node1 $node2 10Mb 5ms DropTail

$ns duplex-link $node1 $node2 10Mb 5ms DropTail

$ns duplex-link $node1 $node2 10Mb 5ms DropTail

# Create a UDP agent and attach it to node1

set udp1 [new Agent/UDP]

$ns attach-agent $node1 $udp1

# Create a UDP sink and attach it to node2

set null [new Agent/Null]

$ns attach-agent $node2 $null

# Connect UDP agent to the null sink

$ns connect $udp1 $null

# Create a CBR traffic generator and attach it to the UDP agent

set cbr1 [new Application/Traffic/CBR]

$cbr1 set packetSize_ 1000

$cbr1 set rate_ 5Mb

$cbr1 attach-agent $udp1

# Schedule the CBR traffic generator to start and stop

$ns at 0.1 “$cbr1 start”

$ns at 4.0 “$cbr1 stop”

# Define a procedure to simulate link failure (failover in LACP)

proc link-fail {} {

global ns node1 node2

$ns rtmodel-at 2.0 down $node1 $node2

puts “Link between node1 and node2 failed at 2.0s”

}

# Schedule the link failure event

$ns at 2.0 “link-fail”

# Finish procedure

proc finish {} {

global ns tracefile namfile

$ns flush-trace

close $tracefile

close $namfile

exec nam lacp.nam &

exit 0

}

# Schedule end of simulation

$ns at 5.0 “finish”

 

# Run the simulation

$ns run

Explanation of TCL Script:

  1. Multiple duplex links: The script is makes three duplex links among the nodes like node1 and node2 to mimic link aggregation.
  2. Traffic generation: A UDP agent is attached to a node1 and Null agent is attached to node2. A CBR traffic generator forwards packets over the links.
  3. Link failure simulation: The process link-fail is planned to replicate a link failure among the node1 and node2. At 2.0 seconds, one of the links among the two nodes will be failed.
  4. Load balancing and failover: In this basic script, the simulator NS2 will send the packets over the remaining links after the failure, mimicking LACP’s failover mechanism.
  1. Add Custom Load Balancing Logic (Optional)

We can improve the script by appending the load balancing among the links and to do this we may want to write a custom scheduling mechanism to distribute traffic evenly over all active links.

For instance, we can alter the traffic generator in C++ class to distribute packets over the various links according to their status (up or down). It needs diving into the C++ source code of NS2 in which we can launch the logic to manage load balancing.

  1. Analysing Simulation Results

We can open the generated trace file (lacp.tr) and NAM file (lacp.nam) to evaluate the traffic flow, after running the simulation and the effect of link failure on the network.

  1. Run the script using the below command:

ns lacp_simulation.tcl

  1. Open the NAM visualization:

nam lacp.nam

In NAM, we should be able to observe the traffic flowing over several links and monitor the impact of the link failure event.

  1. Enhancing the Simulation

To enhance the realism of the LACP simulation, we can:

  • Execute more furthered traffic management logic.
  • We can use the Agent/TCP instead of UDP to mimic more realistic application-level traffic.
  • Test with various link capacities, failure rates, and load balancing algorithms.

The procedure to execute and evaluate the Link Aggregation Control protocol in the NS2 has been fully illustrated above. Additional specific details will follow according to your requirements. You can Obtain top-notch project guidance from our team. Reach out to ns2project.com for expert implementation advice on Link Aggregation Control Protocol in ns2. We specialize in simulating the performance analysis of LACP.