Circuit switching is the technology that has been powering the good old PSTN telephone systems. This technology was later successfully challenged by the latest VoIP technology that uses Packet switching. There is a big difference between the working techniques followed by both the technologies and packet switching definitely enjoys an edge over circuit switching. The success of VoIP can be attributed to the efficient packet switching technology.

The Need for a Network

Prior to delving deeper into the subject of switching, we must realize that communication between two persons involves a network and when the network is as big as the internet, there are numerous machines and devices involved. For instance, communication between a person from Hawaii and another located at Canberra involves transmission of data through several switches, routers and variety of other network devices.

Routing vs Switching

We often tend to confuse between routing and switching but these are two different techniques. The only common thing between these two is their job; they basically establish a link and forward the data to destination from the source.

The most significant thing to decide is the transmission of information over a very complex network, which is known as the circuit or path. There are nodes placed around the path and it is the routers or switches along with variety of other network equipments that constitute the nodes.

Circuit Switching

In the case circuit switching, signals or data are transmitted over a predetermined path. It is the system that decides the route, which is based on the algorithm of resource optimization; the entire transmission is carried through the predetermined path. The communication takes place along a secured and dedicated route and it is released after the termination of a communication session.

Packet Switching

Prior to learning about packet switching, it is imperative that we learn a bit about the term packet. The IP or internet protocol facilitates the breaking down of data signal into smaller packets that are stuffed with information like the IP address of the destination and source, data load, sequence numbers and a variety of other control information. Datagram or segment is the other name used for a packet. On reaching the destination, every packet is reassembled to complete the original data. Only digital data can be converted into packets.

The packet switching technology does not allot any predetermined path for the data packets. The packets are transmitted over the network, irrespective of each other’s path and every packet has to find their own route to reach the destination. Only when a packet reaches a node, the decision on which node to move next is taken. The pre-stuffed information in the packets like source IP or destination IP address helps it to determine the route.

It might already be clear to you that PSTN phones use the circuit switching technology whereas the modern VoIP systems use the packet switching technology. 

Circuit Switching Vs Packet Switching

  • Packet switching is less expensive when compared to the circuit switching used by the PSTN systems. Since circuit switching uses dedicated lines for communication, users end up renting a single line, which makes it really expensive. On the other hand, when a packet switching technology is used, a single line can be used by multiple users, thus bringing down the cost.
  • Reliability is often the USP of circuit switching and packet switching technology often fails to match up to the grand old technology. As the circuit switching technology uses a dedicated line so there is no data loss is experienced. On the other hand, in a packet switching technology as a single line is used by numerous packets, it often amounts to congestion or data loss. This makes packet switching far less reliable and this also results in poor voice quality in VoIP systems.