Packet-Switched Network vs. Circuit-Switched Network

A circuit-switched network relies on a physical connection between two nodes, which requires the link to be set up before the nodes can communicate. In contrast, a packet-switched network is a digital network that manages data transfer in the form of small and optimized packets, an improvement from older network types. This article explains each network type in detail, their pros and cons, and critical differences.

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What Is a Packet Switched Network?

A packet-switched network is defined as a digital network that manages data transfer in the form of small and optimized packets comprising a payload and a header, an improvement from older, analog-era network types.

Communication technology has evolved over the years – from loud-sounding gongs to the discovery of the telephone and radio waves. In the telecom industry, data is transferred from one location or device to another through packet switching.

Packet switching is a means of organizing and sharing data into bits called packets which are then transmitted across a digital network. These packets consist of two parts; the header and the payload. The header on each packet contains information about the data packet. This information includes the packet’s destination address, the source of the extracted payload, and other details. The networking hardware utilizes this information to direct the packets.

Packet switching is the primary basis for transferring data across computer networks. With packet switching, routing and the movement of data packets are done so that a channel is occupied only when a packet is being moved on it. When the data packet has been sent to its designated address, the channel is immediately made available and can transmit further incoming data packets.

Packet switching works by allocating resources as needed. Resources in this instance refer to open channels for transferring bits of data. This allocation is done using statistical multiplexing and dynamic bandwidth dispersing methods. Every time the data packets reach any hardware component, they are received, buffered, assembled, and sent again until they arrive at the next location. This process is repeated throughout the distance covered by the traveling data packet.

In packet switching, a specialized channel must not be reserved solely for a data stream. This differentiates it from other types of data transmission over computer networks. The good thing about packet switching is that even though packets are broken up into bits and sent over different networks to a destination, they are still reassembled in the order in which they were sent and then presented to the final receiver.

To explain this, a sender may send data reading three, five, and seven in that order. In transmission, that data packet bearing three may arrive just after the packet bearing five. Yet, they will be arranged as three, five, and seven at the final destination, replicating the original message.

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Pros and cons of packet switching

The pros of packet switching include:

In packet switching, data packets can find the destination address without traveling on one dedicated channel.
Packet switching allows the sender to resend missing or dropped packets. Thus there is reduced packet loss.
Transmission of

Voice over Internet Protocol (VOIP)

audio and data is less expensive because dedicated channels are unnecessary.

There are also a few cons to packet switching:

It does not fully support communication methods that are constantly used, such as high-volume voice calls.
There is no security protocol for the data packets sent across the network.
Packet loss is still possible, especially when traffic flow is very high. These packets can not be resent again.

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What Is a Circuit Switched Network?

A circuit-switched network is defined as a type of network that relies on a physical connection between two distinct network nodes, which requires the link to be set up before the nodes can communicate.

Circuit switching is another type of switched network communication. They are connection-based networks where data is transferred directly across an already chosen and dedicated channel without interruption until the complete information has been sent to the destination and the communication link ends.

Circuit switching was created in 1878 and is the technology on which Alexander Bell built his telephone. Circuit switching has been the dominant technology that telecommunications companies have used for over 100 years. This was before the discovery of packet switching networks.

In a communication network, multiple links are connected via nodes or switches. Data is then passed from node to node through the switching process information to its destination. In the switching nodes, the type of information is less important than the destination the information is headed for. End user devices such as our telephones, computers, and mobile phones are called stations and are attached to nodes.

Circuit switching is set up in the physical layer and used for direct data transmission through a dedicated channel. This makes it perfect for transmitting susceptible and continuous information streams such as voice transmission. Otherwise, sending data in short batches will waste underutilized bandwidth as data will be sent across in short bursts.

Circuit switching at the physical layer routes the complete message via the dedicated channel built when setting up the connection. Because data is delivered and received in streams, this kind of switching isn’t optimal for data transfer since the line would be inactive between transmission waves.

In every computer network, there is a maximum data transfer rate per link in the network. This is distributed across all the devices present in the network. Circuit switching ensures equal bandwidth allocation irrespective of whether those devices are actively transmitting.

There are three phases during the circuit switching process:

Establishment of the circuit
: Before sending data across, the network ensures a patent, free and available path between the nodes in the network, joining the sender and receiving device. If available, a circuit is now created and established.
Transfer of data
: data of any type, voice, data, analog or digital, is then sent across.
Disconnection
: After the data transfer, the circuit ends so that the bandwidth becomes available for other use.

Pros and cons of a circuit-switched network

The pros of a circuit-switched network are:

There is reduced delay and latency before and especially during a call.
Data packets arrive in the proper order and with minimum packet loss.
Communication is done with a steady bandwidth and consistent data rate.

It is also important to remember the cons of such a network:

It is not well adapted to internet communication.
The channels used for circuit switching become automatically unavailable for other purposes.
There is a risk of poor use of resources.

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Differences Between Packet-Switched Network and Circuit-Switched Network

Packet-switched networks and circuit switch networks have clear differences between them. These are tied to their primary mode of operation. However, their overall function in information transmission and communication remains the same. Differences between both switching technologies include:

1. Need for connection

Circuit switching is a connection-oriented network technique (much like transmission control protocol or TCP), while packet switching is a connectionless network switching method. This means that for circuit switching, there must be an actual creation of the network path through which information will pass.

Connection-oriented also involves the termination of that same network. In circuit switching, there is an end-to-end connection between the sender and the receiver. It was designed to model the telephone system, which works in a very similar fashion.

Circuit switching uses a handshake method referred to as a reliable network service. Connectionless, on the other hand, can be likened to a postal office. The packets can take different routes as long as they arrive at their destination.

2. Phases involved in data transfer

In circuit switching networks, data is sent across the network, which involves three phases. However, packet switching does not need special steps or stages before one can send data across. The three phases in the circuit switching protocol include the connection establishment phase, the actual data transfer phase, and the connection termination phase.

Each phase is essential and needed for the seamless running of the circuit switch network. Failure to establish a connection means data transfer will not occur, while failure to terminate a link keeps that bandwidth unavailable and useless in subsequent data transfer.

3. Resource reservation

Resource reservation is a unique feature of circuit switching, whereas, in packet switching, there is no resource allocation for any user. Resource allocation invoked maintaining the patency of a particular bandwidth for transmission between two nodes. Resource allocation in circuit switching is because there is a fixed data transfer pathway.

Resource reservation can lead to unavailable paths for other users and require them to wait for a communication link to be freed up. This does not occur in packet-switched networks where every station trying to transmit data is fitted in as soon as possible, and packets flow in any available path.

4. The degree of flexibility

Circuit switching networks are not very flexible. However, packet-switched networks offer greater flexibility. In circuit switching, the links between nodes make a connection between the sender and receiver and are dedicated to that purpose. One cannot use them for other purposes, hence the rigidity of the pathway.

For example, one cannot simultaneously use a path used for a voice call in circuit switching between two phones to send information over the internet or transfer files.

On the other hand, packet switching is a flexible virtual network circuit that offers a connection to multiple uses simultaneously. Data packets from the same source follow numerous different routes. As long as the packets are well labeled, each will arrive at its proper destination with minimal interference.

5. Store and forward transmission

In circuit switching, store and forward transmissions do not occur. However, there is a store and forward transmission feature in packet switching.

The store and forward transmission technique is applied in packet-switched networks, where data packets arrive at a node and are stored before being sent off to other nodes. The node storing the incoming packets screens the data packet for any error that may compromise the message. This store and forward transmission eliminates bad or invalid packets and is repeated at each intermediate node along all the routes taken by different data packets.

As much as it makes the transmission error-free, it increases the latency period of the packet-switched communication technology.

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6. The degree of reliability

Circuit-switched networks are very reliable, while packet-switched networks have poor reliability and can easily get congested. Reliability is a function of how certain it is that data sent from a user at one end of the network will arrive entirely at the other end of the network topology.

In circuit-switched networks, there is a dedicated channel to pass all incoming data from one user to the other throughout the connection. This means there is a very low possibility of data loss and a high certainty that the network will accurately pass all information. On the other hand, a packet-switched network does not regulate the flow of data traffic across a network. Data loss is quite common during congestion as multiple data packets are vying for available bandwidths.

7. Handling of bilateral traffic

Circuit switching does not handle bilateral traffic easily, while the packet switching technique makes bilateral traffic go as smoothly as possible. In circuit switching, there is just one channel, and it is occupied by data coming from the sender. This proves problematic if the receiver tries to send a message to the sender. In packet switch networks, the link between two nodes may be occupied, but data packets can easily take another link and thus get from the receiver back to the sender.

8. Availability of bandwidth

Optimized bandwidth availability is a feature seen in a packet-switched network that is not seen in circuit-switched networks. In the latter, the total bandwidth is already shared among the devices connected through the broad network. Each device has its bandwidth and can be used or not, depending on the activity level. This reduces the availability of bandwidth. That is, the size is already fixed.

Also, data transmission must be completed once bandwidth is in use before it becomes available for others. The reverse is the case for packet switching, where bandwidth is allocated based on current demand. This makes it always available except when there is congestion from too much traffic.

9. Cost and pricing

The cost of a communication network includes installation and running costs. For circuit-switched networks, the initial cost for installing them is pretty low. However, the charging of running cost is based on time spent on the network and the distance between receiver and sender.

This means that international calls across two countries, for example, using the circuit-switched network, will be costly. For a packet-switched network, the installation cost is a bit expensive. However, uses are charged based on time and the size of data packets. Users do not need to worry about distance as pricing excludes that.

10. The nature of layers

The layers used by circuit-switched networks and packet-switched networks are different. The circuit network is implemented at the physical layer, whereas the packet-switched network is implemented at the network layer.

The physical layer is the bottom-most layer per the Open Systems Interconnection (OSI) model of computer networking. The circuit fixed network’s physical layer means that there must be physical connections between the devices. A good example is the traditional telephone landlines used quite commonly in the past.

The network layer used by packet switching is layer 3 of the OSI. It allows data to move into and through other networks and is responsible for packaging data with the correct labels containing the destination addresses. The network layer also helps direct each data packet to a selected bandwidth.

11. The end terminal

In circuit switching, the logical end terminal is the telephone and modem, while in a packet-switched network, the end terminal is typically a computer.

12. The technologies in use

Circuit switching and packet switching use different types of technologies. Circuit switching uses time and space division switching, while packet switching uses the datagram and virtual circuit approaches. In addition, the protocols for delivery using circuit switching technologies are more straightforward than packet switching technologies with more complex protocols.

13. Information type

Circuit switching technology uses analog voice or Pulse Code Modulation (PCM) digital voices. Packet switching makes use of binary information. The analog voice is an audio recording in a mechanical format. It converts the original sound waveforms to continuous vibrations. This is the same technique by which sounds are imprinted upon vinyl records or magnetic tape. Pulse Code Modulation is used to represent analog signals in digital form. It is used in computers, compact discs, and other digital audio applications.

14. Applications

Circuit switching was initially designed for voice transfer. In contrast, the discovery of packet switching technology was suitable in time for the internet. Therefore, packet switching is used to transfer data packets across the internet and most local area networks (LAN). Currently, packet switching is used to produce new phone technologies like Long-Term Evolution (LTE) and Global System for Mobile Communications (GSM). All these networks don’t need a prior established connection or dedicated link to transmit data between end users.

15. Routing scheme

The route used for circuit switching is selected during the initial setup, whereas, in packet switching, the route for each packet is chosen independently of each other.

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Takeaway

As enterprises become increasingly more digitally mature, the era of circuit-switched networks is all but over. Older networks like 2G and 3G use circuit switching, which is why one could not simultaneously conduct data transfers and voice calls. Today, the advent of 4G and 5G based on packet switching technology addresses this issue, a critical difference between the two network types.

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