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en.wikipedia.org/wiki/Packet_switching

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Posted by crouse

PSN: A Packet Switched Network, or PSN, refers to the packet switched networks that existed before the Internet. The history of such networks can be divided into three eras: early networks before the introduction of X.25 and OSI, the X.25 era when many Postal Telephone and Telegraph (PTT) companies introduced networks with X.25 interfaces, and the Internet era when restrictions on connection to the Internet were removed.

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Posted by HamidAliKhan

Packets are routed individually. In Packet Networks, the source chops the data into units called packets and delivers the packets to the network with an address attached (in a header). It is up to the network to figure out where that destination is and deliver it
Voice is chopped into packets. (Each packet has a header containing a destination address and a separate data section)
It is up to the network to decide the path for each packet
Division of labor- It is the source’s job is to build a good packet. It is the network’s job to deliver the packet
Network only promises “best effort”. It will “try” to deliver the packet. No guarantee of time

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Posted by snjysanjay05

A Packet Switched Network, or PSN, refers to the packet switched networks that existed before the Internet. The history of such networks can be divided into three eras: early networks before the introduction of X.25 and OSI, the X.25 era when many Postal Telephone and Telegraph (PTT) companies introduced networks with X.25 interfaces, and the Internet era when restrictions on connection to the Internet were removed.

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Posted by sagitraz

The public switched telephone network (PSTN) is the network of the world's public circuit-switched telephone networks, in much the same way that the Internet is the network of the world's public IP-based packet-switched networks. Originally a network of fixed-line analog telephone systems, the PSTN is now almost entirely digital, and now includes mobile as well as fixed telephones.

The PSTN is largely governed by technical standards created by the ITU-T, and uses E.163/E.164 addresses (more commonly known as telephone numbers) for addressing.

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Posted by sagitraz