VPN Virtual Private Network
This is a private network link, which is carried on a public network. VPNs can be implemented in number of ways, ranging from: Layer 1 VPN utilizing physical layer links such as E1 and SDH; Layer 2 VPN using data link connections based on ATM, FR, Ethernet etc; Layer 3 VPN, typically based on IP in IP tunnelling techniques such as those provided by IPSec. In addition, MPLS networks are also extensively deployed to support VPN connectivity. In this case, customer traffic is kept separate through the use of unique labels per customer.
