A virtual private network (VPN) allows remote users to securely connect to a private server from any location. For example, large companies with offices spanning multiple locations use VPNs to ensure a secure and universal network for all office sites. In other instances, employees on the road or working from home can use VPNs to securely connect to the office network from their laptops.
The purpose of VPNs
VPNs can connect multiple sites over tremendous distances, similar to a wide area network (WAN).
However, VPNs are used to extend Intranets — large private networks — worldwide and provide access to a wider user base. Educational institutions such as universities use VPNs to connect campuses and students to university machines.
To give a user access to a private network, users must first be authenticated using a unique identification and password via a remote portal.
A VPN is most often used through browser-based software (a VPN client) that requires a user to log in to the system. The software then displays the remote computer’s desktop or network files, which can be accessed through the browser.
Due to the secure nature of VPNs, they use a number of protocols that encrypt data traffic. This is especially important because data is being transmitted over a public network between two remote locations.
Protocols used by VPNs include IP Security (IPSec), Secure Sockets Layer (SSL), Transport Layer Security (TLS), Point-to-Point Tunneling Protocol (PPTP) and Layer 2 Tunneling Protocol (L2TP).
The most commonly used of these methods is SSL because of the secure communication it provides over the Internet. Both locations use a "handshake" method of authentication. To successfully initiate this connection, the connecting computer must share a key that matches the required parameters for the receiving location.
The advantage of VPN
VPNs are traditionally a very inexpensive cost-effective way to build a private network. The use of the Internet as a communications channel between sites is quite common, which is driving down the cost of such services. A VPN is an ideal choice for corporations needing flexibility.
The disadvantage of VPN
Performance issues can be common, often depending on the location of the remote client accessing the private network. A loss of data can occur due to the risks of transmitting data over multiple public networks. To combat this, many VPN vendors offers a guaranteed quality of service (QoS) to ensure no data is lost in transmission.