- It is a data forwarding technique where nodes switch data to other specific nodes in a network.
- It is made up of series of interconnected nodes called switches.
- In this all the devices are not directly connected to each other like P2P or like start topology, rather they are connected to a nodes called switch.
- First data is received by a switch which redirects this data to correct recipient.
This is of three types:
- Circuit switching
- Packet switching and
- Message switching
- In circuit switching, a dedicated path is established between two end points of communication.
- All the resources which is needed for communication is reserved before starting the communication that is during the setup phase and all these resources persist until the teardown phase.
- Circuit switching takes place at the physical layer.
- Since it works at the physical layer, data is in the form of signal that is 0 and 1.
- Examples are: TDM(Time Division Multiplexing) and FDM(Frequency Division Multiplexing).
- In packets switching, data is transferred in smallest unit called packet.
- The resources needed for communication are not reserved in advance, rather its allocated dynamic.
- Packets are forwarded on the basis of source and destination IP address.
- Internet uses packet switching technique.
Packet switching is of two types:
- Virtual-circuit Networks
- Datagram Networks
- In case of virtual-circuit network, a virtual path is established between two end point of communication.
- All the packets take the same route to reach the destination.
- Even in this case there are three phase that is connection setup, connection maintain and connection teardown.
- Resource are allocated during the setup phase and released once the connection is terminated.
- It is connection oriented service like a telephone call.
- Some of the common examples are: HTTP, SSH, FTP
- In this the packets are referred as datagram.
- Each packets are independents of each other and can take up a different route to reach the destination.
- It provides connection less service that is connection setup or teardown phase.
- Common example is like postcard, where each postcard can take different route and are independent to each other.
Examples are: TFTP, Tunneling protocol, DNS, RIP, VOIP
- HTTPS is HTTP with SSL/TLS, which typically runs on TCP but can also run on UDP
- This came before packet switching and hence it has characteristics as that of packet switching.
- The basic difference between them is that in case of message switching complete message is appended with header and transferred whereas in case of packet switching, message is divided into smaller chunks called packets and each packet is appended with header and send.
- Even in this packets are treated independently and can take different path to reach other end.
- Connection is not established so there is no setup or teardown phase.
- In this the intermediate nodes would store the message in the queue and checks for transmission errors, inspects the destination address and then delivers it to recipient. This is like store and forward mechanism causing delay in transmission.
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