You may have heard or read the phrase “Routing Table” when referring to a Subscriber. This solution explains what the Routing Table is and how it is generated.An AES IntelliNet Subscriber maintains a list of ID’s, up to eight for the purpose of passing its messages or data packets through, in route to the head end or Central Receiver. The list is generated by listening. Any transmission by any other device on the IntelliNet network at the same frequency and with the same Cipher code that is passed through the Transceiver and decoded by the Subscriber is evaluated. The Subscriber that hears the transmission will extract values contained in the header of the transmission detected.
The extracted information will include the ID of the device currently transmitting the packet along with its Link Layer / Level (LL), NetCon (NC) and Status or fault code. The signal strength of the transmission will also be evaluated. The signal strength evaluation includes whether the Carrier Detect level was reached (CD) and a value that identifies how readable the data was.Upon decoding a packet header, the extracted values are compared with the current list or Routing Table. If the ID is in the list and the values have not changed the Table is left as is.
If there was a change to a value of an ID in the list, the list is modified. If the ID is not in the list, then it is evaluated to determine if it should be in the list. That evaluation includes the signal strength, Status code and whether the LL is equal to or better than what is currently in the list. If the ID rates a place in the list, the list is modified, the Table is sorted and the Subscriber calculates new LL and NC values.
The important thing to take away from this lesson is that the Routing Table is built by listening. Attempts to communicate back to those ID’s in the list, does not occur until the Subscriber has a Data Packet to transmit and only then, if it progresses through the List of ID’s and reaches that ID in the process of using its Routing Table because others in the list before it have failed to have a packet Acknowledge received.