Switching is a process of connecting communication devices together. Here data packets are transferred from one device to the target destination device. Packet switching and circuit switching are the commonly used techniques for switching devices.
In circuit switching, data is sent over a dedicated channel between the sender and receiver. On the other hand, in packet switching the data to be sent is divided into small packets. These packets have information about the source and destination. But the basic difference between them is that packet switching is connectionless but the circuit switching process is connection-oriented.
Lets us take a closer look at the details of the two switching processes.
What is Circuit Switching?
In circuit switching, messages are sent between a sender and receiver by establishing a physical path between them. After the connection has been established between them, the message is sent to the destination along this dedicated path.
After the receiver accepts the data, the network is informed about the completion of the process. Then the switches are released and a new connection is set up.
This type of switching is implemented at the Physical layer of a network. It is used commonly in Public Switched Telephone Network (PTSN), where the receiver and a caller share information using a dedicated channel. So if someone calls another person, the connection remains active until both the parties have disconnected the call.
However, circuit switching is not considered ideal for data transmission as data is transmitted in streams. During the process, the connection remains idle for a significant amount of time, so most of the bandwidth might be wasted.
What is Packet Switching?
In this process, no physical connection is created between the sender and the receiver. Before the message is sent, it is subdivided into small chunks called packets. Data packets are sent to the destination from their source one at a time.
Each packet consists of two parts – a header and a payload.
The header consists of the following information:
- Source address
- Destination address
- Total number of packet chunks or pieces
- The sequence number of the packets
The actual data is in the payload section.
The data packets take different routes to arrive at their destination. So, the packets of a particular file may not take the same way to reach the target location.
There are intermediate nodes located along the way – that examines the packet header and check their order. If the packets are not in order, they are reorganized back to the actual message and dispatched to the destination node.
Now that we have a better understanding of the basic concepts of the switching methods, let us compare them to figure out which is better.
Circuit Switching vs Packet Switching
In circuit switching, a physical connection is developed using a signalling protocol between the source and destination to send data.
On the other hand, in packet switching, a path is created dynamically for each packet using their source and destination information. The header section of the data packets has this vital information.
Circuit switching is commonly used for voice communication, such as a telephonic conversation. But packet switching is designed for data communication, such as sending an email.
Packet switching is flexible as the data divided into small packets where each packet may take a different route to reach its destination. On the contrary, circuit switching is not flexible as a dedicated connection is established between the sender and receiver.
In circuit switching, once the connection is established, data is processed without any delay. This dedicated path ensures that the data rate is guaranteed.
In packet switching, before the data is sent to the destination, it is processed at the intermediate nodes.
Arrangement of data
As data packets take different paths to reach the other end, they can be out of order in packet switching. They are later rearranged according to their sequence number.
In circuit switching, the message reaches the target while having the same arrangement with which it was sent in the first place.
Circuit switched networks the entire data is transferred over the same circuit. Each data unit has access to the circuit and the routing information obtained from the source.
The data packets of a packet switched network has the routing information stored in its header and are sent individually.
Key Differences between packet switching and circuit switching
The important features that separate packet switching and circuit switching from each other are:
- Circuit switching is connection-oriented and performed at the Physical layer. But, packet switching is connectionless and performed in the Network layer.
- In a circuit switching network, the connection is reserved and nobody can use it until the sender and receiver leave it. So, if no data is being transferred, the connection remains idle, and hence bandwidth is wasted. On the other hand, packet switching reduces bandwidth wastage, as the route is not decided beforehand.
- In circuit switching, all data packets can get lost if a router in the circuit goes down, as the packets follow the same path. Packet switching is more fault-tolerant as data packets take different routes to reach the destination. They can be routed over any malfunctioning network component.
- Packet switching bills the users according to the duration of connectivity. But in case of circuit switching, the users are billed as per the duration and distance of the connection.
- Congestion can occur when the connection is being established in circuit switching. In packet switching, the congestion usually occurs when the data is transferred.
As discussed in the above article, circuit switching is used mainly for telephonic communications where there is a fixed connection between two ends. But this process is not fault-tolerant and wastes bandwidth. On the contrary, packet switching is more fault-tolerant and sends data packets without wasting bandwidth.
However, due to a dedicated path, circuit switching guarantees data rate without much delay. But packet switching lags behind in this case as data packets take different routes to reach the target node, and hence delay is observed. Nevertheless, the transmission quality is high in packet switching and is better than a circuit-switched network.
So, the best switching method depends on how the processes are used and the requirements of the users.