Definition: packet switching

A digital network technology that breaks up a message into smaller chunks (packets) for transmission. Unlike circuit switching in traditional telephone networks, which requires the establishment of a dedicated point-to-point connection, each packet in a packet-switched network contains a destination address. Thus, all packets in a single message do not have to travel the same path. As traffic conditions change, they can be dynamically routed via different paths in the network, and they can even arrive out of order. The destination computer reassembles the packets into their proper sequence.

Data, Voice and Video
Packet switching always excelled at handling messages of different lengths, as well as different priorities, providing the attributes for quality of service (QoS) were included in the design of the network. However, packet switching was originally created for data. Today, using the global standard IP protocol (see TCP/IP), packet networks have become the norm for voice and video as well (see IP on Everything).

The First Packet Switches
The first international standard for wide area packet switching networks was X.25, which was defined at a time when circuits were analog and very susceptible to noise. Subsequent packet technologies, such as frame relay, were designed for almost-error-free digital lines.

ATM uses a cell-switching technology that provides the bandwidth-sharing efficiency of packet switching with the guaranteed bandwidth of circuit switching. See X.25, frame relay and ATM. Contrast with circuit switching.

From FDM to TDM to IP

IP-based packet switching has become the transport for nearly everything, including voice and video. For voice conversations especially, analog and digital-based circuit switching waste as much as 75% of the bandwidth due to pauses in speech and one person listening while the other talks.