How to Implement Real Time Protocol in NS2

To implement the Real-Time Protocol in ns2, we have to simulate the realistic data exchanges like audio or video streaming through a network. It commonly executes over UDP and is used for sending audio and video over IP networks. We have to replicate RTP traffic by generating custom application-level traffic that imitates the properties of RTP due to the ns2 can’t support RTP. The demonstration will guide you to implement the basic simulation in ns2:

Steps to Implement RTP in NS2

  1. Set Up NS2 Environment
    • Make certain that you have ns2 installed on your computer.
  2. Understand RTP Protocol
    • RTP is developed for real-time transmission of multimedia data. It functions together with the Real-Time Control Protocol (RTCP) for observing data delivery and offering fewer control information. RTP usually runs over UDP because of its low-latency nature.
  3. Simulate RTP Traffic Using Custom Applications
    • Use the available potential of ns2 to simulate RTP traffic. This involves generating a custom application that produce UDP traffic with characteristics relevant to RTP streams like small, regular packets.
  4. Create a Basic RTP Simulation in NS2

Here’s how you can configure a simple simulation script that mock-up RTP traffic:

# Define the simulation environment

set ns [new Simulator]

# Open the trace file

set tracefile [open out.tr w]

$ns trace-all $tracefile

# Define the finish procedure

proc finish {} {

global ns tracefile

$ns flush-trace

close $tracefile

exec nam out.nam &

exit 0

}

# Create RTP sender and receiver nodes

set rtp_sender [$ns node]

set rtp_receiver [$ns node]

# Create a duplex link between sender and receiver

$ns duplex-link $rtp_sender $rtp_receiver 10Mb 10ms DropTail

# Create UDP agent for RTP sender and attach it to the node

set udp_sender [new Agent/UDP]

$ns attach-agent $rtp_sender $udp_sender

# Create UDP agent for RTP receiver and attach it to the node

set udp_receiver [new Agent/UDP]

$ns attach-agent $rtp_receiver $udp_receiver

# Connect UDP agents

$ns connect $udp_sender $udp_receiver

# Create a custom application to simulate RTP traffic

set rtp_app [new Application/Traffic/Pareto]

$rtp_app attach-agent $udp_sender

$rtp_app set packetSize_ 160       ;# Typical size of an RTP audio packet (e.g., G.711 codec)

$rtp_app set burst_time_ 0.02      ;# Simulate packetization interval (20ms)

$rtp_app set idle_time_ 0.001      ;# Minimal idle time to simulate continuous stream

$rtp_app set rate_ 64Kb            ;# Bandwidth rate for the RTP stream

# Start the RTP traffic at 1.0s

$ns at 1.0 “$rtp_app start”

# Stop the simulation at 10.0s

$ns at 10.0 “finish”

# Run the simulation

$ns run

  1. Explanation of the Script
    • Simulator Object ($ns): Build the simulation environment.
    • Nodes: Two nodes are designed to indicate the RTP sender and receiver.
    • UDP Agents: RTP typically uses UDP, so UDP agents are included to the sender and receiver nodes.
    • Custom RTP Application: A custom application using Traffic/Pareto is generated to replicate RTP traffic. This model is frequently used for bursty traffic patterns, common in multimedia applications.
    • Packet Size and Timing: Packet sizes and timing intervals are setting up to simulate RTP streams, with small, recurrent packets imitating audio or video streams.
  2. Run the Simulation
    • Store the OTcl script to a file (like rtp_simulation.tcl).
    • Run the script using the given command:

ns rtp_simulation.tcl

    • The simulation will produce a trace file (out.tr) and a Network Animator (NAM) file (out.nam). Use NAM file to visualize the simulation.
  2. Analyze the Results
    • The trace file (out.tr) has detailed information about the packets sent, received, and dropped. You can use this data to evaluate the performance of RTP traffic as well as latency, jitter, packet loss, and throughput.
  3. Enhancements
    • Multiple RTP Streams: Replicate multiple RTP streams by generating extra RTP sender-receiver pairs, simulating a video conference or streaming scenario.
    • RTCP Simulation: Create control packets that observes the quality of service (QoS) to simulate RTCP traffic combined with RTP.
    • Network Conditions: Launch network impairments like packet loss, jitter, and delay to learn RTP’s behavior under various conditions.
  4. Additional Considerations
    • QoS Metrics: Compute vital RTP-related QoS metrics includes jitter, delay, and packet loss.
    • Codec Simulation: Modify the packet size and interval in terms of several codecs (e.g., G.711, G.729 for audio, or H.264 for video) to simulate different RTP scenarios.
    • Security: Consider simulating Secure RTP (SRTP) by presenting encryption mechanisms, although this would be more advanced to model in NS2.

At the end of this manual, we provided the details through elaborated instructions regarding Real Time Protocol and its examples which is implemented in ns2 environment. If needed, we will offer any other details on this topic.

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