Packet Switching

 

Packet Switching

Packet switching is a switching technique used at the network layer, where a message received from the upper layer is divided into smaller, manageable units called packets.

The packets are then transmitted through the network, usually independently, from the source toward the destination. The destination receives the packets and waits for all packets belonging to the same message before delivering the complete message to the upper layer.

Basic operation

Source
  │
  │  Message
  ↓
Divide into packets
  │
  ├── Packet 1 ──→
  ├── Packet 2 ──→    Network
  ├── Packet 3 ──→   (Routers)
  └── Packet 4 ──→
                         ↓
                     Destination
                         │
                  Reassemble packets
                         ↓
                      Message

At each router, the network layer determines how a packet should be forwarded toward its final destination.

Important points

• The unit of data at the network layer is a packet.
• A message is divided into multiple packets.
• Packets are transmitted one by one through the network.
• Routers perform switching and forwarding of packets.
• The destination receives the packets and reconstructs the original message.
• Unlike circuit switching, packet switching does not require a dedicated physical path for the entire communication.

Two approaches to packet switching

At the network layer, packet-switched networks can use two approaches for routing packets:

1. Datagram approach
2. Virtual circuit approach

These two approaches differ mainly in how the network handles the path and forwarding of packets belonging to the same message.

In short: Packet switching divides a message into packets and forwards these packets through a packet-switched network toward the destination, where they are collected to reconstruct the original message.