The old telephone system (PSTN) uses circuit switching to transmit voice data whereas VoIP uses packet-switching to do so. The difference in the way these two types of switching work is the thing that made VoIP so different and successful. To understand switching, you need to realize that the network in place between two communicating persons is a complex field of devices and machines, especially if the network is the Internet. Consider a person in Mauritius having a phone conversation with another person on the other side of the globe, say in the US. There are a large number of routers, switches and other kinds of devices that take the data transmitted during the communication from one end to the other. Switching and routing
Switching and routing are technically two different things, but for the sake of simplicity, let us take switches and routers (which are devices that make switching and routing respectively) as devices doing one job: make a link in the connection and forward data from the source to the destination. Paths or circuits
The important thing to look for in transmitting information over such a complex network is the path or circuit. The devices making up the path are called nodes. For instance, switches, routers and some other network devices, are nodes. In circuit-switching, this path is decided upon before the data transmission starts. The system decides on which route to follow, based on a resource-optimizing algorithm, and transmission goes according to the path. For the whole length of the communication session between the two communicating bodies, the route is dedicated and exclusive, and released only when the session terminates. Packets
To be able to understand packet-switching, you need to know what a packet is. The Internet Protocol(IP), just like many other protocols, breaks data into chunks and wraps the chunks into structures called packets. Each packet contains, along with the data load, information about the IP address of the...
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