Switching (Formal Definition)
Switching is the technique of transferring information from one computer network to another by establishing temporary connections between devices, usually achieved with the help of switches.
Packet Switching (Formal Definition)
Packet switching is a method of communication in which a message is divided into small units called packets, each containing addressing and sequencing information, that travel independently through the network and are reassembled in the correct order at the destination.
Datagram Packet Switching (Formal Definition)
Datagram packet switching is a connectionless switching technique where each packet (datagram) is treated independently, carrying full destination information, with routes determined dynamically at each intermediate node.
Virtual Circuit Switching (Formal Definition)
Virtual circuit switching is a connection-oriented switching technique in which a logical path is established between sender and receiver before data transfer, and all packets follow the same path using a Virtual Circuit Identifier (VCI).
SWITCHING
Switching is the technique of transferring information from one computer network to another. It is achieved by using switches, which are hardware devices used to connect multiple computers within a Local Area Network (LAN). Switches create temporary connections between devices and forward packets based on MAC addresses. They transfer data only to the intended device, operate in full duplex mode, and avoid unnecessary broadcasting, thus conserving bandwidth.
Advantages of Switching
- Increases bandwidth of the network.
- Reduces workload on PCs by sending data only to the addressed device.
- Improves overall network performance by reducing traffic.
- Minimizes frame collision by creating separate collision domains.
Disadvantages of Switching
- More expensive than bridges.
- Cannot easily determine network connectivity issues.
- Requires proper design and configuration to handle multicast packets.
Types of Switching Techniques
- Circuit Switching
- Packet Switching
- Message Switching
- Virtual Circuit Approach
- Datagram Approach
PACKET SWITCHING
Packet switching is a technique where a message is divided into smaller units called packets, each containing source address, destination address, and sequence number. Packets may travel through different paths but are reassembled in the correct order at the receiving end. Missing or corrupted packets are retransmitted, and acknowledgment is sent upon successful reception.
Advantages of Packet Switching
- Cost-effective
- Reliable
- Efficient for bursty traffic
APPROACHES OF PACKET SWITCHING
-
Datagram Packet Switching (Connectionless)
- Packets are treated independently (called datagrams).
- Each packet carries full destination information.
- Path is not fixed; routing decisions are taken dynamically at intermediate nodes.
- No setup or teardown phases; each packet is handled equally.
- Uses routing tables, updated dynamically.
- Delay depends on transmission time, propagation delay, and waiting time in queues.
-
Virtual Circuit Switching (Connection-Oriented)
- A logical connection (virtual circuit) is established before data transfer.
- Uses call request and call accept packets to set up connection.
- Path remains fixed for the session.
- Each switch maintains a Virtual Circuit Table (VCT) with:
- Incoming interface & VCI
- Outgoing interface & VCI
- Uses Virtual Circuit Identifier (VCI) which is unique only within a switch.
- Data passes in correct order, ensuring sequencing and reliability.
Phases of Virtual Circuit Switching
- Establishment Phase – Logical connection is set up, quality of service is agreed.
- Data Transfer Phase – Flow control and error control ensure proper sequencing.
- Connection Release Phase – Clear-request packet terminates the connection.
COMPARISON
- Datagram Switching: Connectionless, dynamic path, no setup phase, packets may arrive out of order.
- Virtual Circuit Switching: Connection-oriented, fixed path, requires setup/release phases, packets arrive in order.
