System information

Packet-Switched Networks
In the mid-1990s, network performance improved to the point where it became possible
to send a stream of media information in real time across a network connection. Because
the media stream is chopped up into segments, which are then wrapped in an address-
ing envelope, such connections are referred to as packet-based. The challenge, of course,
is to send a flood of these packets between two endpoints, ensuring that the packets
arrive in the same order in which they were sent, in less than 150 milliseconds, with
none lost. This is the essence of Voice over IP.
Conclusion
This appendix has explored the technologies currently in use in the PSTN. In Appen-
dix B, we will discuss protocols for VoIP: the carrying of telephone connections across
IP-based networks. These protocols define different mechanisms for carrying telephone
conversations, but their significance is far greater than just that. Bringing the telephone
network into the data network will finally erase the line between telephones and com-
puters, which holds the promise of a revolutionary evolution in the way we
communicate.
Conclusion | 615