Difference between circuit switching and packet switching
In this page circuit switching vs packet switching describes difference between circuit switching(CS) and packet switching(PS).
In circuit switching network dedicated channel has to be established before the call is made between users. The channel is reserved between the users till the connection is active. For half duplex communication, one channel is allocated and for full duplex communication, two channels are allocated. It is mainly used for voice communication requiring real time services without any much delay.
As shown in the figure 1, if user-A wants to use the network; it need to first ask for the request to obtain the one and then user-A can communicate with user-C. During the connection phase if user-B tries to call/communicate with user-D or any other user it will get busy signal from the network.
In packet switching network unlike CS network, it is not required to establish the connection initially. The connection/channel is available to use by many users. But when capacity or number of users increases then it will lead to congestion in the network. Packet switched networks are mainly used for data and voice applications requiring non-real time scenarios.
As shown in the figure 2, if user-A wants to send data/information to user-C and if user-B wants to send data to user-D, it is simultaneously possible. Here information is padded with header which contains addresses of source and destination. This header is sniffed by intermediate switching nodes to determine their route and destination.
In packet switching, station breaks long message into packets. Packets are sent one at a time to the network. Packets are handled in two ways, viz. datagram and virtual circuit.
In datagram, each packet is treated independently. Packets can take up any practical route. Packets may arrive out of order and may go missing.
In virtual circuit, preplanned route is established before any packets are transmitted. The handshake is established using call request and call accept messages. Here each packet contains virtual circuit identifier(VCI) instead of the destination address. In this type, routing decisions for each packet are not needed.
Comparison between CS vs. PS networks
As shown above in Packet switched (PS) networks quality of service (QoS) is not guaranteed while in circuit switched (CS) networks quality is guaranteed.
PS is used for time insensitive applications such as internet/email/SMS/MMS/VOIP etc.
In CS even if user is not talking the channel cannot be used by any other users, this will waste the resource capacity at those intervals.
The example of circuit switched network is PSTN and example of packet switched network is GPRS/EDGE.
Following table summarizes difference between circuit switching and packet switching of type datagram and virtual circuit.
|Circuit Switching||Packet Switching(Datagram type)||Packet Switching(Virtual Circuit type)|
|Dedicated path||No Dedicated path||No Dedicated path|
|Path is established for entire conversation||Route is established for each packet||Route is established for entire conversation|
|Call setup delay||packet transmission delay||call setup delay as well as packet transmission delay|
|Overload may block call setup||Overload increases packet delay||Overload may block call setup and increases packet delay|
|Fixed bandwidth||Dynamic bandwidth||Dynamic bandwidth|
|No overhead bits after call setup||overhead bits in each packet||overhead bits in each packet|