How to Implement QoS aware Routing in NS2

To implement QoS-aware routing in NS2 has needs to setting up the network to select specific kinds of traffic based on Quality of Service (QoS) parameters, like bandwidth, latency, jitter, and packet loss. QoS-aware routing is crucial in scenarios such as multimedia streaming or VoIP, in which real-time performance and reliability are necessary.

NS2 helps to some QoS mechanisms, however for particular routing protocols and QoS scheduling, we need to tweak existing routing protocols such as AODV, DSDV, or DSR or use the CBR (Constant Bit Rate) traffic generator with particular metrics.

Here, is step-by-step implementation procedure to implement QoS-aware routing in ns2:

Step-by-Step Implementation:

  1. Understand QoS-Aware Routing Concepts

QoS-aware routing usually aims to meet particular network performance goals based on:

  • Bandwidth: Make sure that assured applications get a minimum amount of data throughput.
  • Delay: Reducing the delay for sensitive applications such VoIP.
  • Jitter: Diminishing variations in packet arrival times.
  • Packet Loss: Make sure that critical traffic is less likely to be dropped.

In NS2, we can mimic this by selects traffic flows, setting up routing parameters and handling queues to regulate how packets are managed.

  1. Basic Network Setup

Begin by generating a network topology with multiple nodes and links. The aim is to setting up routing and queuing to select particular types of traffic according QoS requirements.

# Create a simulator instance

set ns [new Simulator]

# Open a trace file to log the simulation

set tracefile [open “qos_routing_trace.tr” w]

$ns trace-all $tracefile

# Create network nodes

set node1 [$ns node]

set node2 [$ns node]

set node3 [$ns node]

set node4 [$ns node]

# Define links between nodes (with bandwidth and delay)

$ns duplex-link $node1 $node2 1Mb 10ms DropTail

$ns duplex-link $node2 $node3 512Kb 20ms DropTail

$ns duplex-link $node3 $node4 2Mb 5ms DropTail

  1. Configure Traffic Flows with QoS Requirements

Now, configure diverse types of traffic like UDP for real-time applications and TCP for non-real-time data. We can use CBR to mimic real-time traffic and FTP for non-real-time traffic.

Traffic with High QoS Requirements (e.g., VoIP or Video Streaming):

# Create a UDP agent for real-time traffic (high QoS)

set udp_high_qos [new Agent/UDP]

$ns attach-agent $node1 $udp_high_qos

# Create a CBR traffic generator with high priority

set cbr_high_qos [new Application/Traffic/CBR]

$cbr_high_qos attach-agent $udp_high_qos

$cbr_high_qos set packetSize_ 1000

$cbr_high_qos set rate_ 500Kb   ;# Higher data rate for real-time traffic

Traffic with Lower QoS Requirements (e.g., File Transfer):

# Create a TCP agent for non-real-time traffic (lower QoS)

set tcp_low_qos [new Agent/TCP]

$ns attach-agent $node1 $tcp_low_qos

# Create an FTP traffic generator with lower priority

set ftp_low_qos [new Application/FTP]

$ftp_low_qos attach-agent $tcp_low_qos

$ftp_low_qos set type_ FTP

  1. Configuring Routing Protocols with QoS Support

Most standard routing protocols in NS2, such as AODV, DSR, and DSDV, do not natively support QoS routing. But, we can adjust the routing parameters by change link metrics like bandwidth and latency to mimic a preference for assured paths based on QoS.

Example: Using AODV with modified routing preferences

We can configure AODV (Ad-hoc On-demand Distance Vector) routing to desire paths with higher bandwidth or lower delay by adapting link properties and queuing mechanisms.

# Configure AODV routing protocol for all nodes

$ns node-config -adhocRouting AODV \

-llType LL \

-macType Mac/802_11 \

-ifqType Queue/DropTail/PriQueue \

-ifqLen 50 \

-antType Antenna/OmniAntenna \

-propType Propagation/TwoRayGround \

-phyType Phy/WirelessPhy

  1. Implement Priority Queuing (PriQueue) for QoS

To make sure that traffic with higher QoS requirements is prioritized, we can use a priority queue. NS2 delivers a DropTail/PriQueue mechanism, that permits to allocate priority levels to diverse traffic classes.

# Define a priority queue between nodes

$ns duplex-link $node2 $node3 1Mb 10ms Queue/DropTail/PriQueue

# Assign priorities to the traffic agents

$udp_high_qos set prio_ 1  ;# High priority for real-time traffic

$tcp_low_qos set prio_ 2   ;# Lower priority for non-real-time traffic

The selects queue makes sure that packets from higher-priority flows (like real-time traffic) are sent before packets from lower-priority flows.

  1. Simulate Network and Observe QoS Behavior

After configure the traffic flows and priority queues, execute the simulation and observe the performance of the diverse traffic types.

# Start traffic at different times

$ns at 1.0 “$cbr_high_qos start”

$ns at 2.0 “$ftp_low_qos start”

# Stop traffic after 10 seconds

$ns at 10.0 “$cbr_high_qos stop”

$ns at 10.0 “$ftp_low_qos stop”

# End simulation at 12 seconds

$ns at 12.0 “finish”

proc finish {} {

global ns tracefile

$ns flush-trace

close $tracefile

exit 0

}

# Run the simulation

$ns run

  1. Monitoring QoS Metrics

After executing the simulation, evaluate the trace files to assess the network’s performance for each traffic type. We should concentrate on the following parameters:

  • Throughput: Evaluate the throughput of both high-priority and low-priority traffic.
  • Delay: Assess the end-to-end delay for the high-priority traffic.
  • Packet Loss: Validate for dropped packets in the real-time traffic.
  • Jitter: Evaluate the variation in packet arrival times for real-time traffic.
  1. Advanced QoS Routing Protocols

If we want a more cutting-edge QoS routing protocol, we might have to execute or adjust an existing protocol. For instance, we could execute a version of AODV-QoS that takes into account QoS parameters such as bandwidth and latency when selecting routes.

In such cases, we will need to adapt the AODV source code or expand it to contain additional parameters. This would involve:

  • Adjusting the AODV route discovery process to reflect bandwidth and delay metrics.
  • Adding logic to the AODV routing table to store QoS data for each route.
  • Modify the RREP (Route Reply) messages to contain QoS metrics.

The above is an implementation procedure that executes a basic QoS-aware routing mechanism in NS2 environment simply by modifying traffic flows, queues, and routing configurations to mimic diverse levels of service. More information will be shared regarding the QoS aware routing.

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