CertiGuide to Network+  9  Chapter 0000:  Network Basics       9  VI  Private vs Public Networks

Private Networks 1 Virtual Private Networks

A public network is one where network connectivity and resources are shared by many different administrative units. Typically no one company using the network has control over every piece of the network. One often shares the links between sites on a public network or more entities, with multiple organizations’ data intermixed on the same network lines. The most well known public network is the Internet.

Public networks enable organizations to take advantage of economies of scale, as it’s often the case that Wide Area Network links that handle a large amount of traffic aren’t much more expensive than slower WAN links. With the cost of a faster pipe split among multiple organizations, users can enjoy faster network speeds at lower cost than would be possible on a private network.

Another advantage of public networks is that they allow organizations to basically time-share connectivity, and not pay for a line when they’re not using it. Not every organization uses network capacity at the same time. If you transmit large amounts of data from Baltimore to Phoenix between 3am and 6am, but don’t otherwise need connectivity between those two cities, why pay for the capability to network between those two points, the other 21 hours of the day?

The primary disadvantage of public networks is a reduced amount of control over data and host security. Since your data is traveling along paths that other organizations’ data are also using, it is possible

Another disadvantage is that public networks often provide less control over bandwidth than do private networks. Unless you pay your public network service provider a substantial premium for guaranteed bandwidth (specified as a CIR, or committed information rate), odds are that when many other people are using the network, the speed of the network will seem to slow down. In some situations, this may not matter. But if you have a business-critical need to move data within a specific time window, guaranteed bandwidth may be an important criterion when selecting a network service provider.

Private Networks 1 Virtual Private Networks