US Patent 9135037 Virtual network protocol

Methods, systems, and apparatus, including computer programs encoded on a computer storage medium, for receiving an outgoing packet from a source virtual machine; obtaining a secret key for the source virtual machine, the secret key not being known by a destination virtual machine; obtaining a unique token derived at least partly from the secret key and a network address of the destination virtual machine; encapsulating the outgoing packet in a second packet along with the token and a token expiration time; and sending the second packet to the destination virtual machine.