In the previous course "IP Networks, Routers and Addresses", we used a private network, i.e. dedicated point-to-point circuits connected with routers, as the simplest framework for understanding packets, bandwidth on demand, routers, and network addresses.
A router is a device than relays packets from one circuit to another on a first-come, first-served, packet-by-packet basis.
Knowing which circuit to relay the packet to is the routing part of the story, also called packet switching and packet forwarding.
Routers implement bandwidth on demand by not reserving a fraction of the capacity of the connecting circuit for each device (channelizing), but instead giving each device the possibility of using the full capacity of the connecting circuit – when there is something to transmit.
Since devices generate traffic in bursts, and normally have nothing to transmit, many more devices can be connected to the circuit using bandwidth on demand instead of channelizing.
This results in either lower cost or higher bandwidth for each device:
• Implement the same apparent bandwidth as channelizing using a cheaper, lower-speed connecting circuit, or
• Implement higher apparent bandwidth for each device for the same cost as a channelized connecting circuit.
In this course, we will take the same idea and apply it again at the carrier network level: replacing the dedicated lines between customer locations from the simple framework of the previous course with bandwidth on demand service from a carrier between the customer locations.
This brings the same benefit to the customer as it did to individual devices in the previous course: lower cost or faster performance.
All of the carrier's customers in a city are given access to the same high-speed intercity circuits, with the possibility of transmitting to other cities at full line speed – but only when they have something to transmit.
This is called a packet network service provided by a carrier.
This type of service is used by businesses (including government, organizations and other carriers) to implement cost-effective, flexible, high-speed packet communications between specific locations.
It is, of course, also the technical fundamentals of the collection of packet networks that are called the Internet.