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Networking Architecture

The BlackDog communications framework consists of the following components and connections.

Components of the Network

There are two main network components:

• The BlackDog device
• The host computer, to which the BlackDog physically connects, and which provides network and peripheral resources for the BlackDog

The BlackDog relies on the host's internet connection to establish external communication.

Physical Connections

The following physical connections exist among the components. Physical connections are established directly through hardware.

• The BlackDog is connected to the host via a USB port.
• The host computer is connected to the Internet/Intranet via an Ethernet (or similar network) connection.

Networks

• Host PC Network: one end is a USB Ethernet connection to the BlackDog device, and the other end is the Ethernet (or similar network) connection to the Internet/Intranet.
• NAT Networking Tunnel: connects the BlackDog device to the Internet (using Network Address Translation (NAT) with Vtun and the host).Thus, the BlackDog becomes a virtual device that is proxied by the host PC (using NAT's Realm-networking.exe, and vtun) to create a virtual tunnel to the Internet.

Communication between Components

• BlackDog device talks to the host using TCP/IP, and can talk to the Internet when NAT is running and the Internet connection is active.
• Host PC talks to the device using TCP/IP, and to back end service applications through a port forward on the device.

Applications Communications Scenario

The following section describes how the data from an application running on the BlackDog is communicated to a backend server.

An application opens a TCP/IP socket to a remote backend service, then writes data through the socket. The kernel accepts this packet on behalf of the application, and then sends it to a tap device (virtual Ethernet device) on the BlackDog. The vtun application running on the BlackDog reads data from the tap device, packages it, and transmits it to the Realm-networking.exe process running on the host PC. The Realm-networking.exe process unpacks the encrypted data, performs network address translation on the data, and then sends the data to the destination network on behalf of the BlackDog.

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