A VPN creates a private, secure "tunnel" from one endpoint to another endpoint. The endpoints can be a remote user's notebook computer to a network gateway (client to gateway). A network gateway is a designated entry point into a network, such as a router or wireless AP. Another endpoint configuration for a VPN is connecting a network gateway in one location to a network gateway in another location (gateway to gateway). This article focuses on a client-to-gateway scenario for mobile, remote access to your SOHO network.
To create the secure tunnel, a VPN uses a variety of technologies that support encryption, authentication, and/or data integrity. Encryption is the process of making information unreadable to unauthorized users by converting it to cipher text. Authentication ensures that users attempting to access your network are who they say they are. Authentication methods include passwords, usernames, and PKI (public-key infrastructure; a means of verifying users and network devices). Data integrity guarantees that the transmitted information is not altered or tampered with.