How to Calculate Network Authorization in NS2
To calculate the Network Authorization in Network Simulator 2 (NS2), we need to control the access to the network resources and services depend on a set of rules or policies. Since NS2 is not particularly configured for simulating advanced authentication and authorization mechanisms, we have to replicate simple authorization rules by controlling how packets are dispatched or congested amongst nodes, simulating user or device access control. It could encompass allowing rules that permits or deny traffic in terms of source or destination of the traffic, imitating authorization features.
In this context, network authorization can be simulated by executing access control policies, where specific nodes (users or devices) are granted or denied access to network services (e.g., servers) according to the specified rules. Utilize the following procedure to calculate the network authorization in ns2:
Steps to Simulate and Calculate Network Authorization in NS2
- Set Up the NS2 Simulation
Start by generating a network with specific nodes indicates authorized clients that can access certain resources, and other nodes are unauthorized clients that are denied access. The node allowing the authorization behaves like a gateway or firewall that confirms whether the source node is granted to access the destination node.
Example NS2 Script to Simulate Authorization
# Create NS2 simulator instance
set ns [new Simulator]
# Open trace file for output
set tracefile [open out.tr w]
$ns trace-all $tracefile
# Define nodes
set authorized_client [$ns node] ;# Authorized client node
set unauthorized_client [$ns node] ;# Unauthorized client node
set gateway [$ns node] ;# Gateway node enforcing authorization
set server [$ns node] ;# Server node (destination)
# Create links between nodes
$ns duplex-link $authorized_client $gateway 1Mb 10ms DropTail
$ns duplex-link $unauthorized_client $gateway 1Mb 10ms DropTail
$ns duplex-link $gateway $server 1Mb 10ms DropTail
# Set up UDP traffic from authorized client to server
set udp_auth [new Agent/UDP]
$ns attach-agent $authorized_client $udp_auth
set null_auth [new Agent/Null]
$ns attach-agent $server $null_auth
$ns connect $udp_auth $null_auth
set cbr_auth [new Application/Traffic/CBR]
$cbr_auth set packetSize_ 500
$cbr_auth set interval_ 0.01
$cbr_auth attach-agent $udp_auth
# Set up UDP traffic from unauthorized client to server
set udp_unauth [new Agent/UDP]
$ns attach-agent $unauthorized_client $udp_unauth
set null_unauth [new Agent/Null]
$ns attach-agent $server $null_unauth
$ns connect $udp_unauth $null_unauth
set cbr_unauth [new Application/Traffic/CBR]
$cbr_unauth set packetSize_ 500
$cbr_unauth set interval_ 0.01
$cbr_unauth attach-agent $udp_unauth
# Define authorization policy at gateway
proc authorization_policy {src dst type} {
if {$src == “unauthorized_client”} {
return 0 ;# Deny access to unauthorized clients
}
return 1 ;# Allow access to authorized clients
}
# Apply authorization policy
$ns at 0.5 “$ns set-forwarding-filter authorization_policy”
# Start and stop traffic
$ns at 0.5 “$cbr_auth start”
$ns at 0.5 “$cbr_unauth start”
$ns at 4.5 “$cbr_auth stop”
$ns at 4.5 “$cbr_unauth stop”
# End simulation
$ns at 5.0 “finish”
proc finish {} {
global ns tracefile
$ns flush-trace
close $tracefile
exit 0
}
# Run the simulation
$ns run
Explanation of the Script:
- Gateway Node: The gateway node behaves like the point where authorization is applied. It checks whether the client (source node) is permitted to access the server (destination node).
- Authorized and Unauthorized Clients: The node authorized_client is granted to access the server, while unauthorized_client is denied access.
- Authorization Policy: The authorization_policy function states the access rules. In this case, the policy blocks traffic from unauthorized_client and permit traffic from authorized_client.
- Implement Authorization Policy
The authorization_policy function is used to implement the authorization policies:
- If the source is the unauthorized client, the traffic is dropped.
- If the source is the authorized client, the traffic is permitted to pass.
You can mimic more modern authorization scenarios like access control depend on IP addresses, ports, or traffic variants by expanding this this policy.
- Capture Data from the Trace File
NS2 produces a trace file (out.tr) that logs key events like packet enqueueing, dequeuing, and dropping. You can assess this file to analyze the effectiveness of the authorization policy by computing:
- Packet drops: Estimate how many packets were dropped because of illegal access tries.
- Throughput: Calculate how much legal traffic was successfully transmitted.
- Latency: Quantify the time delay for authorized traffic to reach the destination.
- Calculate Authorization Metrics
Packet Drops Due to Unauthorized Access
You can sum the amount of packets that were dropped due to they originated from the unauthorized client, indicating the enforcement of the authorization policy.
Here’s an AWK script to compute packet drops caused by unauthorized access:
awk ‘
{
if ($1 == “d” && $3 == “gateway” && $4 == “server” && $7 == “unauthorized_client”) {
dropped_packets++;
}
}
END { print “Total Packets Dropped Due to Unauthorized Access:”, dropped_packets; }’ out.tr
This script totals the counts of packets dropped by the gateway because of unauthorized access tried by the unauthorized_client.
Throughput of Authorized Traffic
Throughput means that the number of authorized traffic that was successfully transmitted from the legal client to the server.
Here’s an AWK script to estimate throughput for authorized traffic:
awk ‘
{
if ($1 == “-” && $3 == “gateway” && $4 == “server” && $7 == “authorized_client”) {
total_bytes += $6; # Sum the total bytes forwarded by the gateway for the authorized client
}
}
END { print “Throughput for Authorized Client:”, total_bytes / 5.0, “bytes/sec”; }’ out.tr
This script measures the throughput by couting the total bytes transferred by the authorized_client to the server through the gateway, and dividing by the simulation time (5 seconds).
Latency for Authorized Traffic
You can quantify the latency for authorized traffic by estimating the time it takes for a packet to move from the authorized client to the server over the gateway.
Here’s an AWK script to calculate average latency for authorized traffic:
awk ‘
{
if ($1 == “+”) {
send_time[$7] = $2; # Record the time a packet is sent from the authorized client
}
if ($1 == “-” && $3 == “gateway” && $4 == “server” && $7 == “authorized_client”) {
if (send_time[$7] != “”) {
latency = $2 – send_time[$7]; # Calculate the latency for authorized traffic
total_latency += latency;
count++;
}
}
}
END { print “Average Latency for Authorized Client:”, total_latency / count, “seconds”; }’ out.tr
This script measures the average latency for traffic from the authorized_client as it conveys across the gateway to the server.
- Enhance the Authorization Policy
You can improve the authorization policy by attaching more sophisticated access controls, like:
- Port-based authorization: Permit or deny access in terms of the source or destination port.
- Time-based authorization: Grant access only during certain periods.
- Role-based authorization: Simulate various roles (e.g., admin vs user) with changing levels of access to the server.
Example: Port-Based Authorization
You can alter the authorization_policy function to congest or enable traffic based on the destination port:
proc authorization_policy {src dst type src_port dst_port} {
if {$src == “unauthorized_client”} {
return 0 ;# Deny access for unauthorized clients
} elseif {$dst_port == 80} {
return 0 ;# Deny access to port 80
}
return 1 ;# Allow other traffic
}
This function blocks traffic from the unauthorized client and also blocks traffic to port 80, denoting extra access limitations.
- Visualize Authorization Performance
You can visualize the impacts of the authorization policy by plotting metrics like packet drops, throughput, and latency over time using tools like Python (matplotlib) or Excel.
Example Python Plot for Throughput of Authorized Client:
import matplotlib.pyplot as plt
# Example data for throughput over time
time = [0.5, 1.0, 1.5, 2.0, 2.5, 3.0, 3.5, 4.0, 4.5]
throughput = [500, 520, 530, 540, 550, 560, 570, 580, 590] # Example throughput data (bytes/sec)
plt.plot(time, throughput, marker=’o’)
plt.title(‘Throughput for Authorized Client Over Time’)
plt.xlabel(‘Time (seconds)’)
plt.ylabel(‘Throughput (bytes/sec)’)
plt.grid(True)
plt.show()
Summary
To replicate and compute network authorization in NS2:
- Set up the simulation: Configure nodes for authorized and unauthorized clients, a gateway node for policy enforcement, and a server node.
- Implement the authorization policy: State access control rules that permit or deny traffic according to the source node or other policies.
- Capture trace data: Use the trace file to evaluate the impacts of the authorization policy as well as packet drops, throughput, and latency.
- Enhance the policy: Establish latest access control mechanisms like port-based or time-based authorization.
- Visualize performance: Use tools like Python to plot and assess how the authorization policy influences network performance.
Here, we have accumulated the necessary insights and examples of authorization and its computation process including how to attach their advanced mechanisms into the simulation with the help of ns2 simulator. You can refer the examples to better understanding the authorization features.
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