Tunelling is the technique of putting an integrated data packet into another packet (contains routing information) and sending it over the internet. The packets travel through a path which is known as tunnel. To secure a tunelled transmission against interception, all traffic over a VPN is encrypted for safety.
Virtual Private Network (VPN) supports 2 types of tunneling which are as follows:
1. Voluntary tunelling 2. Compulsory tunelling
Both types of tunelling are typically used. These are explained as following below:
1. Voluntary Tunelling:
VPN client in the voluntary tunelling handles all the connection setup. For the setup of connection through tunnel both the tunnel client and the tunnel server have to accept the same tunelling protocol. In voluntary tunelling, client first form a connection to the ISP or carrier network provider. Then the tunnel on a VPN server builds by the VPN client application using this live connection. Two step procedure is required to set up the VPN connection in voluntary tunelling.
2. Compulsory Tunelling:
The carrier network provider in the voluntary tunelling handles all the connection setup required for VPN. It is a one step process as compared to the two step in voluntary tunelling. In compulsory tunelling, the client first establish a normal connection to the carrier then the carrier works as an intermediary to make a connection between a VPN server and that client. Compulsory tunelling provides complete management control of the tunnels to the ISP and hides the details of the connectivity of VPN server from the clients.
Broker devices are used in compulsory tunelling for the verification of clients. The logic build in the broker device are used to associates the client with the different VPN servers. This network device is also called as the following:
- VPN Front End Processor (FEP)
- Network Access Server (NAS)
- Point of Presence Server (POS)
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