Virtual Circuit Switching (VCS) is a communication method used in packet-switched networks to establish a predefined logical path between source and destination nodes before data transfer begins. Unlike circuit switching, where a dedicated physical path is maintained, VCS provides a logical connection, ensuring efficient utilization of network resources.
Key Characteristics of Virtual Circuit Switching
1. Logical Path Setup:
A virtual circuit (VC) is established before the actual data transfer. This involves the negotiation of routing paths and the allocation of resources.
2. Packet Sequencing:
Packets follow the predefined VC, arriving at the destination in order, eliminating the need for reassembly or sequencing.
3. Connection-Oriented:
Virtual circuits require a connection to be established before communication, similar to circuit switching, but operate at the logical level.
4. Resource Sharing:
Multiple virtual circuits can coexist on the same physical link, allowing for efficient resource utilization.
Types of Virtual Circuits
1. Switched Virtual Circuits (SVCs):
Dynamically established and terminated for each session.
Example: Video calls or on-demand file transfers.
2. Permanent Virtual Circuits (PVCs):
Predefined and persistent, suitable for regular, long-term connections.
Example: Connections in leased-line environments.
How Virtual Circuit Switching Works
1. Setup Phase:
A VC is established by exchanging control packets to define the logical path.
Routing tables in each intermediate switch are updated to map incoming and outgoing ports for the VC.
2. Data Transfer Phase:
Data packets are forwarded through the VC, following the predetermined path.
3. Teardown Phase:
The VC is terminated, and network resources are released.
Advantages of Virtual Circuit Switching
1. Guaranteed Delivery Order:
Packets arrive in sequence, simplifying the reassembly process.
2. Resource Efficiency:
Logical paths enable multiple connections on the same physical medium.
3. Reliable Communication:
Reduced packet loss due to error checking during the setup phase.
Disadvantages of Virtual Circuit Switching
1. Setup Delay:
Establishing the VC before data transfer introduces latency.
2. Overhead:
Control packets for setup and teardown add to network traffic.
3. Failure Impact:
A failure in the VC can disrupt the entire connection.
Code Example: Simulating Virtual Circuit Setup in Python
class VirtualCircuit:
def __init__(self):
self.routing_table = {}
def setup(self, src, dest, path):
self.routing_table[(src, dest)] = path
print(f”Virtual Circuit established from {src} to {dest} via {path}”)
def send_data(self, src, dest, data):
if (src, dest) in self.routing_table:
print(f”Data ‘{data}’ sent from {src} to {dest} via {self.routing_table[(src, dest)]}”)
else:
print(“No virtual circuit exists.”)
# Example Usage
vc = VirtualCircuit()
vc.setup(“A”, “D”, [“A”, “B”, “C”, “D”])
vc.send_data(“A”, “D”, “Hello, Network!”)
Schematic of Virtual Circuit Switching
1. Setup: Control packets establish the logical path through routers.
2. Data Transfer: Packets follow the predefined VC.
3. Teardown: Logical path is released, freeing resources.
Applications of Virtual Circuit Switching
1. X.25 Networks:
Early packet-switching networks used VCS for reliable communication.
2. Frame Relay:
Employs PVCs for efficient data transfer in wide-area networks.
3. ATM Networks:
Use VCS for high-speed, low-latency communication.
Conclusion
Virtual Circuit Switching strikes a balance between the reliability of circuit switching and the efficiency of packet switching. Its logical connection model ensures ordered data delivery and resource optimization, making it ideal for applications requiring consistent performance, such as voice calls and multimedia streaming. Understanding VCS is crucial for modern network design and management.
The article above is rendered by integrating outputs of 1 HUMAN AGENT & 3 AI AGENTS, an amalgamation of HGI and AI to serve technology education globally.