Site to Site VPN, Remote VPN

In terms of Internetworking Security, there are 2 types of VPN (Virtual Private Network). VPN are private network that interconnects remote network providing security through tunelling protocols and security procedures. The types of VPNs are as follows:


Site-to-Site VPN
A site-to-site VPN allows offices in multiple fixed locations to establish secure connections with each other over a public network such as the Internet. Site-to-site VPN extends the company’s network, allowing computer resources from one location accessible to employees at other locations. An example of company that uses site-to-site VPN is growing corporation with branch offices located around the world.
Similarly, there are also two types of site-to-site VPNs:

Intranet-based: If a company has one or more remote locations that they wish to join in a single private network, they can create an intranet VPN to connect each separate LAN to a single WAN.

Extranet-based: When a company has a close relationship with another company (such as a partner, supplier or customer), it can build an extranet VPN that connects those companies’ LANs. This extranet VPN allows the companies to work together in a secure, shared network environment while preventing access to their separate intranets.




Remote-Access VPN
A remote-access VPN allows individual users to establish secure connections with a remote computer network. Those users can access the secure resources on that network as if they were directly plugged into the network’s servers. An example of a company that needs a remote-access VPN is a large firm with hundreds of salespeople in the field. Remote-access VPN is also known as virtual private dial-up network (VPDN), acknowledging that in its earliest form, a remote-access VPN required dialling in to a server using an analogue telephone system.

There are two components required in a remote-access VPN. The first is a network access server (NAS), also known as a media gateway or a remote-access server (RAS). A NAS might be a dedicated server, or it might be one of multiple software applications running on a shared server. It’s a NAS that a user connects to from the Internet in order to use a VPN. The NAS requires that user to provide valid credentials to sign in to the VPN. To authenticate the user’s credentials, the NAS uses either its own authentication process or a separate authentication server running on the network.

The other required component is client software. This software is required for the employees to establish and maintain a connection to the VPN. Most operating systems today have built-on software that are capable of connecting to remote-access VPNs, although there might be some other VPNs which requires downloading of other specific applications instead.




References:
http://en.wikipedia.org/wiki/Vpn_client
http://computer.howstuffworks.com/vpn4.htm
http://computer.howstuffworks.com/vpn3.htm