Why would a company use a VPN?

Aside from supporting basic LAN interfaces, a good VPN should have high-availability features such as redundant power supplies. Also, all VPNs require some kind of authorization protocol and encryption, although some companies may choose to opt out of the latter.

Other advanced functions can be useful, such as data compression, routing ability, network address translation, bandwidth management capabilities and fail-over redundancy. When purchasing a ready-made VPN package from a solutions provider, it is often possible to get other bundled services to compliment the network, such as voice over IP and other hosted applications.