Tactical Data Link in Model Builder Visual is very similar to the DACS interface. The packet data structure is sent via signal PDUs (see Part II of this Application Note), radios are used to transmit the data, and the DIS network is used as a conduit. There are a few notable differences:
To set up the data bridge use the TDL Host and TDL Net controls, which are in RMS under the Radio->Settings tab. Send packets that will be transferred across the data bridge to the port and interface of the TDL Host setting. This is where the Telestra will look for the special signal PDUs from the host computer.
TDL Net is the network that implements the bridging across Telestras. The user can set up separate subnets for the DIS information such as transmitter and receiver PDUs (DIS Net), the actual transmitted audio in Signal PDUs (Signals Net), and the TDL PDUs (TDL Net). By default, the Signals Net and the TDL Net are the same as the DIS Net.
Once a radio receives a TDL PDU from across the bridge, it will transmit the data to another host computer based on the IP address and port number of the TDL Host setting. Note that the TDL Host control in RMS sets the location of both the reception and transmission of TDL packets. It is important to remember that the IP address listed in TDL Host should be the IP address of the host computer and the interface will refer to the IP address of the Telestra.
The Generic Radio component comes with TDL enabled and running by default. Turn off the service by using the TDL_Enable flag inside the radio. The radio environment is used to run the data bridge; therefore, radios must be powered on and in-range with the proper frequency and modulation.
When looking to debug your data bridge, there are several tools already available on the Telestra. Radio Monitor has TDL receive and transmit counters available on the radio stats pages, and also radio information pages (see Application Note 71 for more information on the Radio Monitor). Additionally, Ethereal comes pre-installed on the Telestra with a plug-in that decodes signal and other DIS PDUs.