To simulate Fiber Channel Arbitrated Loop (FC-AL) using NS2 simulator that has sequential procedure. FC-AL is a topology utilized within Fiber Channel (FC) networks for storage area networks (SANs) and other high-speed network communications. In FC-AL, devices are associated in a loop configuration, and single device can be communicated at a time after arbitrated for access to the loop. It makes a high-speed, low-latency, and reliable communication network for devices such as servers, storage systems, and other peripherals.
Even though NS2 doesn’t have a built-in module for replicating the Fiber Channel networks directly then we can estimate the Fiber Channel Arbitrated Loop (FC-AL) topology by designing a token-passing ring topology in which each node have to wait to get access to the network that is the token before sending data. This replicates the arbitration mechanism within FC-AL topology.
In the following below, we provided the step-by-step approach to simulate it:
Steps to Simulate Fiber Channel Arbitrated Loop (FC-AL) in NS2
Step 1: Understand Fiber Channel Arbitrated Loop (FC-AL) Topology
In an FC-AL topology:
- Devices are associated in a loop (ring topology).
- A device has initial win arbitration before it can transmit the data on the loop.
- Single device can send at a time, make sure a controlled, collision-free network.
- The token-passing mechanism makes certain that all devices are having the opportunity to communicate without collisions.
Step 2: Design the Network
We will replicate an FC-AL topology utilizing a ring topology:
- Devices (nodes) are associated within a circular loop.
- Each device need to wait for its turn to send the data.
- When a device has transmitted the data, the next device acquires a turn that replicating the arbitration procedure of FC-AL.
Step 3: Create an NS2 TCL Script for Simulating Fiber Channel Arbitrated Loop (FC-AL) Topology
Here is an NS2 TCL script, which replicates a Fiber Channel Arbitrated Loop Topology with the help of ring topology and token-passing logic.
Example: Fiber Channel Arbitrated Loop Topology Simulation in NS2
# Create a new NS2 simulator object
set ns [new Simulator]
# Define link parameters for FC-AL network simulation
set link_bw 2Gb ;# Bandwidth for fiber channel (2 Gbps)
set link_delay 1ms ;# Low delay for fiber optic links (1 millisecond)
set queue_size 50 ;# Queue size (FC-AL has low queue size)
set arbitration_time 0.5 ;# Time to wait for arbitration (token passing delay)
# Create nodes in a loop (FC-AL style ring topology)
set num_nodes 5
set nodes {}
for {set i 0} {$i < $num_nodes} {incr i} {
set node [$ns node]
lappend nodes $node
}
# Create a ring topology by connecting each node to its next and previous neighbor
for {set i 0} {$i < $num_nodes} {incr i} {
set next_idx [expr ($i + 1) % $num_nodes]
set prev_idx [expr ($i – 1 + $num_nodes) % $num_nodes]
# Create duplex links between nodes (simulate FC-AL loop)
$ns duplex-link [lindex $nodes $i] [lindex $nodes $next_idx] $link_bw $link_delay DropTail
}
# Attach UDP agents to nodes to simulate data transmission
set udp_agents {}
set null_agents {}
for {set i 0} {$i < $num_nodes} {incr i} {
set udp [new Agent/UDP]
set null [new Agent/Null]
lappend udp_agents $udp
lappend null_agents $null
$ns attach-agent [lindex $nodes $i] $udp
$ns attach-agent [lindex $nodes [expr ($i + 1) % $num_nodes]] $null
$ns connect $udp [lindex $null_agents [expr ($i + 1) % $num_nodes]]
}
# Create CBR (Constant Bit Rate) traffic to simulate data transfers in FC-AL
set cbr_traffic {}
for {set i 0} {$i < $num_nodes} {incr i} {
set cbr [new Application/Traffic/CBR]
$cbr set packetSize_ 1024
$cbr set interval_ 0.02 ;# High-speed data transfer, typical of fiber channel
$cbr attach-agent [lindex $udp_agents $i]
lappend cbr_traffic $cbr
}
# Schedule the CBR traffic with token passing simulation (arbitration in FC-AL)
for {set i 0} {$i < $num_nodes} {incr i} {
set start_time [expr $i * $arbitration_time]
$ns at $start_time “[lindex $cbr_traffic $i] start”
}
# Create trace and nam files for recording the simulation events
set tracefile [open “fc_al_topology.tr” w]
$ns trace-all $tracefile
set namfile [open “fc_al_topology.nam” w]
$ns namtrace-all $namfile
# Define the finish procedure to close files and start NAM
proc finish {} {
global ns tracefile namfile
$ns flush-trace
close $tracefile
close $namfile
exec nam fc_al_topology.nam &
exit 0
}
# Finish the simulation after 10 seconds
$ns at 10.0 “finish”
# Run the simulation
$ns run
Step 4: Explanation of the Script
- FC-AL Loop Setup:
- Nodes are associated within a loop in which each node is attached to the next node in the ring that replicating the FC-AL loop.
- The link bandwidth is set to 2Gbps (typical for fiber channel), including 1ms delay to mimic the low latency of fiber optic communication.
- Token-Passing Simulation:
- UDP agents are connected to each node to replicate the data transmission.
- A CBR (Constant Bit Rate) application is utilized to transmit continuous information amongst the nodes.
- Token-passing behavior is mimicked by staggering the start times of the CBR traffic. Every single node waits for their time to transmit data, which reflecting the arbitration process within FC-AL.
- Tracing and Visualization:
- A trace file (fc_al_topology.tr) records every network events, like packet transmissions and receptions.
- A NAM file (fc_al_topology.nam) is made for envisioning the network topology and the data flow among the nodes.
Step 5: Run the Simulation
- We need to save the script as fc_al_topology.tcl.
- Execute the script in NS2:
ns fc_al_topology.tcl
It will generate two files:
- fc_al_topology.tr: A trace files which records the packet-level information.
- fc_al_topology.nam: A NAM file for envisioning the network in NAM.
Step 6: Visualize the Simulation Using NAM
To envision the Fiber Channel Arbitrated Loop (FC-AL) Topology within NAM:
nam fc_al_topology.nam
In NAM, we will observe:
- The ring topology of nodes that each node is associated to its neighbors.
- Packet transmissions amongst nodes as the token-passing mechanism are replicated by the staggered traffic flows.
Step 7: Analyze the Trace File
The trace file (fc_al_topology.tr) records every network events, like:
- Packet transmissions and receptions among the nodes.
- Delays and traffic patterns by reason of the token passing (arbitration process).
We can be utilized the tools such as AWK, Python, or custom scripts to examine the trace file and extract crucial parameters like:
- Token-passing delays (arbitration time).
- Packet delivery ratio (PDR).
- End-to-end delay between nodes.
- Network throughput.
Step 8: Enhance the Simulation
Following is a few ways to expand or improve the simulation:
- Increase the Number of Nodes: Replicate a larger FC-AL loop including additional devices, which reflecting a larger SAN environment.
- Vary Arbitration Time: Modify the arbitration time to mimic diverse token-passing speeds also monitor the impact on network performance.
- Simulate Link Failures: Launch link failures to replicate what occurs when parts of the FC-AL loop are detached.
- Dynamic Traffic: Insert numerous kinds of traffic like storage requests, large file transfers to replicate the realistic FC-AL workloads within a SAN environment.
- Multi-loop Networks: Prolong the simulation to contain several FC-AL loops such as scatternets that were interconnected through the gateways or bridges.
In brief, we successfully provided the simplified guide with necessary examples to execute and simulate the Fiber Channel Arbitrated Loop Topology projects using NS2 platform. If you need any details regarding this process, we can provide it.
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