How to Start BGP Routing Projects Using NS2

To stimulate a BGP (Border Gateway Protocol) routing project in NS2 (Network Simulator 2) needs the execution or encompass the routing mechanisms in NS2, as it does not natively include BGP. Here’s a step-by-step guide to building a BGP routing simulation in NS2:

Steps to Start BGP Routing Projects Using NS2

Step 1: Set Up NS2 Environment

  1. Install NS2:
    • Download and install NS2 from the NS2 Official Website.
    • Install need to dependencies like as Tcl, OTcl, and NAM.
    • Validate the installation:

ns -version

  1. Explore NS2 Examples:
    • Examine the basic routing samples in ns-allinone-2.x/examples/ to understand on how routing operates in NS2.

Step 2: Understand BGP

  1. What is BGP?
    • The BGP is a path vector routing protocol used to modify the routing data among the autonomous systems (ASes) in a Internet.
    • BGP calculates the routes according to the policies, not parameter metric such as hop count or delay.
  2. Key Components:
    • Neighbor Relationships: Peering among routers in various ASes.
    • Routing Policies: According to the attributes such as AS_PATH, NEXT_HOP, and LOCAL_PREF.
    • Route Selection: Optimize the paths are chosen in a attribute.

Step 3: Design Network Topology

  1. Describes the nodes and connection to signify the ASes and BGP routers:

set ns [new Simulator]

# Define nodes

set r1 [$ns node]

set r2 [$ns node]

set r3 [$ns node]

set r4 [$ns node]

# Define links between nodes

$ns duplex-link $r1 $r2 10Mb 10ms DropTail

$ns duplex-link $r2 $r3 10Mb 15ms DropTail

$ns duplex-link $r3 $r4 10Mb 20ms DropTail

$ns duplex-link $r1 $r4 10Mb 25ms DropTail

  1. Characterize the AS boundaries via grouping nodes into clusters.

Step 4: Implement BGP Logic

Since NS2 doesn’t has includes the BGP through default, we require to exection it:

Option 1: Tcl-Based BGP Simulation

  1. Define Routing Tables:
    • Manually setting the routing tables for every AS:

set routingTable(r1) {r2 r4}

set routingTable(r2) {r1 r3}

set routingTable(r3) {r2 r4}

set routingTable(r4) {r1 r3}

  1. Simulate Route Advertisement:
    • Nodes are alter the route advertisements periodically:

proc advertiseRoutes {src dst} {

global routingTable

puts “Node $src advertising routes to $dst: $routingTable($src)”

}

  1. Policy-Based Route Selection:
    • Replicate the BGP policy-based decisions:

proc selectBestRoute {routes} {

# Example: Prefer shorter AS_PATH

set bestRoute {}

set minPathLen inf

foreach route $routes {

if {[llength $route] < $minPathLen} {

set bestRoute $route

set minPathLen [llength $route]

}

}

return $bestRoute

}

Option 2: Custom BGP Agent in C++

  1. Create a BGP Agent:
    • Extend the Agent class to implement BGP logic.
    • Handle the routing table and maintain the route advertisements.

Example:

class BGPAgent : public Agent {

public:

BGPAgent();

void recv(Packet* p, Handler* h);

void advertiseRoutes();

void selectBestRoute();

private:

std::map<int, std::vector<int>> routingTable; // Destination -> AS_PATH

};

  1. Implement Key Functions:
    • Route Advertisement: Modify the routes through neighbours.
    • Route Selection: Used the selection for BGP attributes such as AS_PATH or LOCAL_PREF we choose the best route.
  2. Compile and Link:
    • Enhance the agent to the NS2 Makefile and recompile:

make clean && make

Step 5: Add Traffic and Test BGP Routing

  1. Define Traffic Sources and Sinks:

set udp [new Agent/UDP]

$ns attach-agent $r1 $udp

set sink [new Agent/Null]

$ns attach-agent $r4 $sink

$ns connect $udp $sink

# Generate traffic

set cbr [new Application/Traffic/CBR]

$cbr attach-agent $udp

$cbr set packetSize_ 512

$cbr set interval_ 0.05

$ns at 1.0 “$cbr start”

  1. Monitor on how the traffic flows with the network according on BGP routing decisions.

Step 6: Simulate and Analyze

  1. Store the Tcl script as bgp_routing.tcl and replication for the process:

ns bgp_routing.tcl

  1. Show on the outcomes using NAM (Network Animator):

nam bgp_routing.nam

  1. Analyze the trace file to verify:
    • Commercial for the routers.
    • Choose the path terms on BGP policies.
    • Packet delivery ratio and latency.

Step 7: Enhance the Project

  1. Dynamic Updates:
    • Replicate the connection failures or policy changes we follow on the route convergence.
  2. Advanced BGP Attributes:
    • Execute the attributes such as MULTI_EXIT_DISC (MED) or LOCAL_PREF.
  3. Comparison:
    • Associate the BGP routing by other protocols such as OSPF or RIP.
  4. Scalability Testing:
    • Replicate a larger network by several ASes and further nodes.

In the end of the manual, we had utterly delivered the comprehensive details about how to setup and how to simulate the Border Gateway Protocol routing in NS2 simulator. A secondary manual will provide answers to any further queries about this project.

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