Virtual Circuit Networks

Overview/Summary:

Virtual circuit networks, also a type of packet-switched network, establish a dedicated path or connection (a virtual circuit) between the sender and receiver before data transmission. All packets belonging to a message follow the same pre-established path. This ensures in-order delivery and simplifies packet forwarding, but it requires connection setup and maintenance. Virtual circuit networks offer more predictable performance but can be less flexible than datagram networks.

Detailed Explanation:

In a virtual circuit network, a logical connection, called a virtual circuit, is established between the sender and receiver before any data is transmitted. This involves signaling between the end hosts and the network routers to reserve resources and determine the path. Once the virtual circuit is established, all packets belonging to the same message follow the same path. Each packet contains a virtual circuit identifier (VCI) instead of the full destination address, which simplifies forwarding.

Key characteristics of virtual circuit networks:

  • Connection Establishment: A virtual circuit must be established before data transmission. This involves a setup phase.
  • In-Order Delivery: Packets are guaranteed to arrive at the destination in the same order they were sent.
  • Simplified Forwarding: Routers only need to look up the VCI in their tables to forward packets along the correct path.
  • Predictable Performance: Since all packets follow the same path, the delay and latency variation are more predictable.

Advantages of virtual circuit networks:

  • In-order delivery: Simplifies the receiver’s task.
  • Simplified packet forwarding: Reduces router processing overhead.
  • Better congestion control: Easier to manage network congestion along the established path.

Disadvantages of virtual circuit networks:

  • Connection setup overhead: Requires time and resources to establish the virtual circuit.
  • Less flexible: If a router on the path fails, the entire connection is disrupted.
  • Resource reservation: Resources are reserved along the path, even if no data is being transmitted. This can be less efficient than datagram networks in some scenarios.