To simulate TCP/IP projects using NS2 has needs to configure a network topology in which nodes interact using the TCP protocol over the Internet Protocol (IP). TCP is a reliable, connection-oriented protocol, and NS2 deliver a built-in implementation for replicating numerous kinds of TCP connections such as Reno, Tahoe, NewReno. We need to utilize NS2 to replicate TCP/IP behaviour in diverse network conditions, like congestion, packet loss, and changing link delays.
Here’s a step-by-step guide to simulate TCP/IP projects using NS2:
Steps to Simulate TCP/IP Projects in NS2
- Install NS2
- Download and install NS2 from the official NS2 website.
- Make sure that all essential dependencies (Tcl/Tk, OTcl, NAM) are installed to execute simulation scripts and envision outcomes using NAM (Network Animator).
- Understand TCP/IP Concepts
- TCP (Transmission Control Protocol): A reliable transport layer protocol that makes sure data is routed accurately and in the sequential order. NS2 supports numerous TCP variants such as Tahoe, Reno, NewReno, and Sack.
- IP (Internet Protocol): The network layer protocol that manage to addressing and routing among nodes. In NS2, we simulate this by set up the links among nodes with certain delays and bandwidths.
- Congestion Control: TCP utilizes algorithms such as slow start, congestion avoidance, and fast retransmit to regulate network congestion.
- Define the Network Topology
Configure a network topology in which TCP flows happens among nodes. Nodes are associated by links with certain bandwidth and delay features.
Example OTcl Code for TCP/IP Topology:
# Create a simulator instance
set ns [new Simulator]
# Define the topology (grid-based for simplicity)
set topo [new Topography]
$topo load_flatgrid 1000 1000
# Create nodes (e.g., a sender and a receiver)
set sender [$ns node]
set receiver [$ns node]
# Create routers between sender and receiver
set router1 [$ns node]
set router2 [$ns node]
# Set up links between nodes (bandwidth and delay)
$ns duplex-link $sender $router1 10Mb 10ms DropTail
$ns duplex-link $router1 $router2 10Mb 20ms DropTail
$ns duplex-link $router2 $receiver 10Mb 10ms DropTail
In this example:
- Sender and receiver nodes interact through two routers (router1 and router2).
- Links among nodes have a specified bandwidth (e.g., 10 Mbps) and delay (e.g., 10 ms).
- Configure TCP Agents
We required configuring TCP agents at the sender and receiver. TCP agents in NS2 are responsible for handling the transmission and reception of TCP packets.
Example: Setting Up TCP Agents
# Create a TCP agent at the sender
set tcp [new Agent/TCP]
$tcp set class_ 2 ;# Class 2 is TCP Reno by default
$ns attach-agent $sender $tcp
# Create a TCP sink (receiver)
set sink [new Agent/TCPSink]
$ns attach-agent $receiver $sink
# Connect the TCP agent and the TCP sink
$ns connect $tcp $sink
In this example:
- TCP agent is generated at the sender, and a TCP sink is created at the receiver.
- The TCP agent and sink are connected; significance the receiver will recognize the TCP packets sent by the sender.
- Simulate TCP Traffic
To replicate TCP traffic, we need to utilize FTP or CBR (Constant Bit Rate) applications to create data that the TCP agent will send.
Example: FTP Over TCP
# Create an FTP application attached to the TCP agent
set ftp [new Application/FTP]
$ftp attach-agent $tcp
# Start the FTP traffic at time 1.0 seconds
$ns at 1.0 “$ftp start”
In this instance, FTP traffic initiate at 1.0 seconds that creates TCP packets from the sender to the receiver.
- Run the Simulation
Save OTcl script as tcp_ip_simulation.tcl and execute the simulation using the NS2 command:
ns tcp_ip_simulation.tcl
- Analyse the Results
NS2 creates trace files that record all network events that contain TCP packet transmissions, acknowledgments, congestion window changes, and packet loss. We can measure these trace files to measure TCP performance.
Key Metrics to Analyse:
- Throughput: Evaluate the total amount of data successfully route over the TCP connection.
- Congestion Window (cwnd): Monitor on how the TCP congestion window grows and shrinks according to network conditions.
- Packet Loss: Count the number of dropped packets because of network congestion.
- Round-Trip Time (RTT): Estimate the time taken for a packet to travel from sender to receiver and back.
Example: Analyze Trace Files Using Awk
awk -f analyze_trace.awk tcp_ip_simulation.tr
- Visualize the Simulation Using NAM
We need to utilize Network Animator (NAM) to envision the TCP connection, packet transmission, and routing in the network.
nam tcp_ip_simulation.nam
- Simulate Different TCP Variants
NS2 supports numerous TCP variants that contain Tahoe, Reno, NewReno, and Sack. We can replicate these variants by altering the TCP agent’s type.
Example: Using TCP NewReno
# Create a TCP NewReno agent at the sender
set tcp [new Agent/TCP/Newreno]
$ns attach-agent $sender $tcp
We can also experiment with other variants such as TCP Vegas or TCP Sack by generating the proper agent.
- Advanced TCP/IP Features to Simulate
We can prolong TCP/IP simulation to contain more advanced characteristics:
- Congestion Control Algorithms: Replicate the behaviour of diverse congestion control algorithms, like TCP Vegas or TCP Cubic.
- Multiple TCP Flows: Replicate multiple TCP connections in parallel to learn how they compete for bandwidth.
- Packet Loss and Retransmissions: Establish packet loss and evaluate on how TCP manage retransmissions using the fast retransmit and fast recovery mechanisms.
- Buffering and Queue Management: Replicate different queue management schemes (e.g., DropTail, RED) to learn their effects on TCP performance.
Example Simulation Script Outline for TCP/IP
# TCP/IP Simulation script using NS2
set ns [new Simulator]
set topo [new Topography]
$topo load_flatgrid 1000 1000 ;# Set the topography area
# Create sender and receiver nodes
set sender [$ns node]
set receiver [$ns node]
# Create routers between sender and receiver
set router1 [$ns node]
set router2 [$ns node]
# Set up links between nodes with bandwidth and delay
$ns duplex-link $sender $router1 10Mb 10ms DropTail
$ns duplex-link $router1 $router2 10Mb 20ms DropTail
$ns duplex-link $router2 $receiver 10Mb 10ms DropTail
# Create a TCP agent at the sender
set tcp [new Agent/TCP]
$tcp set class_ 2 ;# TCP Reno
$ns attach-agent $sender $tcp
# Create a TCP sink at the receiver
set sink [new Agent/TCPSink]
$ns attach-agent $receiver $sink
# Connect the TCP agent and the sink
$ns connect $tcp $sink
# Create an FTP application to generate TCP traffic
set ftp [new Application/FTP]
$ftp attach-agent $tcp
# Start the FTP traffic at time 1.0 seconds
$ns at 1.0 “$ftp start”
# End the simulation after 10 seconds
$ns at 10.0 “finish”
# Run the simulation
$ns run
Key Points:
- TCP Communication: Replicate reliable TCP communication among nodes using diverse TCP variants.
- Traffic Generation: Utilize FTP or other applications to create TCP traffic for performance evaluation.
- Performance Metrics: evaluate throughput, congestion window, packet loss, and RTT to learn TCP behaviour.
- Congestion Control: Test with diverse TCP variants and congestion control mechanisms to monitor their effects on performance.
In this setup, we had illustrated about how the TCP/IP projects will be simulated in ns2 tool and also we provide the complete explanation to understand the TCP/IP projects. More information regarding this process will also be shared. Check out phdprime.com and send over all the details of your TCP/IP projects. We’ll hook you up with the best simulation results and insights on network performance. Plus, we can guide you through different types of TCP connections like Reno, Tahoe, and NewReno that we’ve worked on.
