[Physics Class Notes] on Difference Between Circuit Switching and Packet Switching Pdf for Exam

Switching is a mechanism to connect different networks or different components of a network. Circuit switching and packet switching are two different kinds of switching. For data transfer through circuit switching, a dedicated path is employed between the source and the destination. However, packet switching is a connectionless technique. Initially, the circuit switching technique was designed for voice communication and the packet switching technique was designed for data transfer. Generally, the packet switching method is far more efficient than the circuit switching method. These two techniques have interesting differences, which will be discussed below. 

Circuit Switching

Circuit switching is a method of switching, which uses a dedicated connection between the sender and the receiver for data transfer. There are three phases of circuit switching, which are as follows:

1. Circuit Establishment: A dedicated physical route is established between the sender and the receiver. The path may include a number of intermediate switching centers.

2. Transfer of Data: After the establishment or setup phase, data is transferred through the dedicated path.

3. Circuit Disconnect: Once the data transfer is done, the circuit is disconnected from one of the ends. All the intermediate links are disconnected in this phase. Circuit switching is usually used in telephones.

To explain the circuit switch, let’s try an example of a telephone network. If a call is dialed from one telephone to another, switches of the telephone exchange make a wire circuit that is continuous between those two telephones, as long as the call goes. During a connection in a circuit network, a small delay is permanent. The competing users cannot degrade any circuit, because till the release of the circuit and setting up a new connection, it gets protected from use by the other callers. When there is a situation in which no communication is actually happening, the channel still stands reserved and gets protection from competing users. 

Packet Switching

In the packet switching method, the data is broken into “pieces” or “packets” and transmitted individually from the source to the destination. Upon receiving, the packets are reassembled at the destination. This method does not require any pre-established dedicated route. The types of packet switching are:

• Virtual Circuit Based Packet Switching: In this mode of packet switching, virtual circuits are established for each packet. Each packet is transmitted through the predestined route. This mode has similar phases as the circuit switching method.

• Datagram Based Packet Switching: In this mode, every packet has two parts, which are a header and a payload. The header of a packet contains the required information (e.g. source and destination addresses, port identity, etc.). The payload contains the original data. The packets are transmitted randomly without any predestined path. At the receiver end, all the packets are arranged and assembled, based on the header information. 

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History of Packet Switching Method

In the 1960s, Paul Baran at RAND corporation, USA, first independently explored the concept of switching data of small blocks while in the UK, in 1965, Donald Davies explored this concept at National Physical Laboratory (NPL). The Air Force of the US in the late 1950s, created a network of wide areas for the semi-automatic ground environment (SAGE) radar defense system. There were vulnerabilities in the network after being recognised by the Air Force, soughted a new system that could survive a nuclear attack and enable a response. The attractiveness of first strike by the enemies diminishes because of this system. To support the initiative taken by the Air Force, Baran created the concept of distributed adaptive message block switching. The Air Force first saw the concept in the summer of 1961, as b-265. It was published later in 1964 as RAND report p-2626. A basic architecture for a communication network that is large-scale, distributed and survivable was described in the p-2626 report. 

It focuses on three main points; making a use of a network that is decentralized with many paths in between the two points, it focuses on dividing the messages of the users into message blocks and lastly, the messages are delivered by forward and store stitching. 

Uses of Packet Switching in Network

Packet switching optimizes using the channel capacity that is available in digital networks of telecommunications, like computer networks, it increases communication’s robustness and it decreases the transmission latency.

It is mostly used in local area networks and on the internet. The internet protocol suite used a variety of link layer technologies to implement the internet. Frame relay and Ethernet are common examples. Mobile phone technologies which are new, use packet switching.

Comparison between Circuit Switching and Packet Switching

The comparison between circuit switching and packet switching is shown in the following table:

Circuit Switching vs Packet Switching

Did you know?

• Apart from circuit switching and packet switching, there is a third type of switching namely message switching. This is a connectionless technique, where an entire message is routed from the source to the destination, through a number of intermediate nodes. Each node stores the data and then forwards it to the next node.

• Packet switching is derived from the message switching technique.

• The concept of packet switching was invented by Paul Baran.

• Circuit switching is effective for voice transmission and packet switching is effective for data transmission.