Virtual Private Networks

Preface

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Definition

A regular phyiscally existing network consisting of cables and routers/switches/etc is called a *network*. You run the various known internet protocols layer 1-4 on it. You can also use those protocols to emulate a *virtual network*. This is mostly done in layer 2 (IP). You tunnel the data of the virtual network encapsulated in IP-Packets for example. If you secure your tunnel as well with various encryption methods one might call the tunneled data a *virtual private network*. This is used in various scenarios, mostly for tunneling sensitive information over an inherently insecure architecture - for example to connect two corporate LANs over the internet.