Packet switching is a technique for sending data whereby the data is split up into variable sized packets before being sent to the destination. A network interface places the data into each packet as payload and frames it with headers that designate the source and the destination. A router reading the destination address on the packet can then determine the best path to the destination.
There are two distinctive type of packet switching in telecom networks:
- Datagram packet switching where each packet is sent out independently based solely on the packets destination address. Routing decisions are made dynamically at each next hop router until the packet reaches its destination. As a result, of this independent treatment packets may take different paths, so there has to be mechanisms built into the protocols to handle out of order packets in a stream and lost packets.
- Virtual circuit packet switching is as its name suggests a way to utilize the benefits of circuit switching – stability, predictability – but still leverage the many benefits of IP packet switching – cost and efficiency. In virtual circuit packet switching, a route is determined prior to the data being sent. This makes the routing through the network predictable and all packets will traverse the network in the same way and importantly the same order. This method provides predictable key performance indicators for latency, packet loss and jitter, which are vital for ascertain the network quality required for delivering real-time voice and video streaming.
Circuit switching is not efficient for sending small packets, and this is one of the reasons for the switch to packet switching in voice networks. The biggest packet switched network is the Internet and it uses the datagram packet model as does VoIP and web browsing.