A VPN, or Virtual Private Network, can be broadly defined as referring to the different technologies used to extend a company’s network while preserving data confidentiality and overcoming the physical barriers of traditional networks.
VPN solutions generally provide the following benefits: public key authentication, confidential exchanges, preserved confidentiality in the case of compromised encryption secrets, and packet transfers to private networks via public ones.
In the world of open source solutions there are many quality products, including OpenVPN and Openswan, presented below.

Solution	Views	Global Rating
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		3.8 5