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Mainframe

Receiver Caller
Fig. 8.7: Packet Switching

CTM: Packet switching offers a connectionless service. Data is fragmented into small packets and each
packet is of fixed size in packet switching technology.

Message Switching

In message switching, the sender sends the data to a switching office first, which is then stored in
its buffer. It then checks the available link and if it is free, the data is relayed to another switching
office. This process goes on until the data is sent to the destination (receiver). As the data is first
stored in a buffer and then sent to the next switching office, it is also called store and forward
switching technique.
CTM: Message switching is a store and forward switching technique where there is no direct connection
between the sender and the receiver.

8.7.3 Difference between Circuit Switching and Packet Switching

1. The circuit switching reserves the required bandwidth in advance, whereas packet switching
uses bandwidth as and when required by the packets to be transmitted.

2. Circuit switching is a fast technology as compared to packet switching which is a slow
mechanism of transferring packets from sender to receiver.
3. Circuit switching requires a dedicated path. Once the connection is established, the
communication path is entirely dedicated to it until the data is completely transferred from
sender to receiver, whereas in packet switching, packets can use any dynamic path.
4. In circuit switching, if the path is overloaded, the call is blocked and communication is delayed.
But in packet switching, packets are allocated to different paths.

5. Circuit-switched networks are used for phone calls and packet-switched networks handle data.
6. Packet switching is more efficient because the cost of the link is shared by many users.

7. In circuit switching, the telephone message is sent unbroken. The message is received in the
Computer Networks
same order as it is originally sent. In packet switching, the message is broken into small packets
which are randomly sent from source and received in random order at destination, which is
then sequentially arranged.

8.9