VPN can be thought as same network but it is much cheaper solution because rather using private lines it uses the shared public network such as internet.
VPN uses the tunneling protocol such as layer 2 tunneling protocols.
Tunneling protocol is the method which encapsulates the payload and delivers the payload over the network. Tunneling protocol is used where the network is incompatible for the delivery of payload.
The main emphasis is kept on keeping the data secured and reliable. At sending end the data is encrypted while on the other end which is the receiving end the data is decrypted.
VPN Security methods
VPN security is one of the main issues. Reliable and secure data transfer and access to the VPN is very important. There are many undergoing techniques to make the VPN secure; and some of the Techniques are discussed below.
1). Firewall
A Firewall is the first method to secure the VPN connection. Firewall can be used to restrict the number of open ports, which protocols are necessary and what type of data packets should be allowed to pass through.
2). Encryption
Encryption is the technique in which the data packets are encoded at the sending end and same data packets are decoded at receiving end. There are two common techniques used for encryption.
A). Symmetric-key encryption
In Symmetric-key encryption each computer which is communicating over the network has the Key. Every computer in communication must know the key before the data is sent over the network. The sending computer encrypts the data using the key and the computer on the receiving side also knows the key already and used the same key to decode the encrypted message.
B). Public-key encryption
This is another way to send the data securely. The Public-key encryption is consisted of public key and private key. A private key is known only by originated computer and public key is given by the originated computer to the computer which wants to communicate securely.
To receive the message/data securely the receiving computer must know the public key.
3). IPSec (Internet Protocol Security Protocol)
This is the very advance technique of encryption. It provides better encryption techniques and comprehensive security algorithms. IPSec can encode data between many network devices. The IPSec uses the tunneling protocol. The tunneling protocol puts the data packets in the additional header, and the additional header provides the routing details and thus the payload can be transferred over the internet securely.
4). AAA (Authentication, Authorization and Accounting) Servers
The Request from the remote client is send to the AAA server and the AAA server does the Authentication of the user, Authorizes the user and Accounts that what actually the user does.