This is the most common and widely used VPN protocol. They enable authorized remote users to connect to the VPN network using their existing Internet connection and then log on to the VPN using password authentication. It also doesn’t provide encryption and it relies on PPP protocol to do this.
L2TP or Layer to Tunneling Protocol is similar to PPTP. It provides encryption, data confidentiality and also data integrity. L2TP was developed by Microsoft and Cisco.
Site-to-site VPN allows different sites of the same organization, each with its own real network, to connect together to form a VPN. Unlike PPTP, the routing, encryption and decryption is done by the routers on both ends, which could be hardware-based or software-based.
Tried and trusted protocol which sets up a tunnel from the remote site into your central site. As the name suggests, it’s designed for IP traffic. IPSec requires expensive, time consuming client installations and this can be considered an important disadvantage.
SSL or Secure Socket Layer is a VPN accessible via https over web browser. SSL creates a secure session from your PC browser to the application server. The major advantage of SSL is that it doesn’t need any software installed because it uses the web browser as the client application.
MPLS (Multi-Protocol Label Switching) are no good for remote access for individual users, but for site-to-site connectivity, they’re the most flexible and scalable option. These systems are essentially ISP-tuned VPNs, where two or more sites are connected to form a VPN using the same ISP. An MPLS network isn’t as easy to set up or add to as the others, and hence bound to be more expensive.
Hybrid VPN servers are able to accept connections from multiple types of VPN clients. They offer higher flexibility at both clienbt and server levels and bound to be expensive.
Deciding which VPN is the best is not easy. It depends on lot of factors like the number of users, bandwidth, security and cost. Remember – cheaper is not always better. For individual users, PP2P VPNs offer the best deal, but for large offices or ones with complex requirements for connectivity MPLS VPNs might be the best option.