Hi Praveen,
These are different topics with different solutions. First of all, keep in mind that VPN is often used to talk about encryption / authentication / security but this is not always the case. Even a VLAN could be considered a VPN, it’s “virtual” and a “private network”.
Let me give you a quick overview in a nutshell:
- MPLS VPN: we use this for connectivity. service providers offer MPLS for remote connectivity. For details, check the MPLS material. The "VPN" part of MPLS is that we use VRFs to separate customer routing information and we create unique VPN routes.
- IPsec VPN: There is no security at all on the network layer, IPsec is a framework that takes care of this.
- SSL VPN: This is a VPN on the application layer, it's typically used with web browsers so that you don't need any client software on your computer. Take a look at this example that I created with the ASA firewall.
Rene