Trace routing

Determining the route a DigiMesh unicast takes to its destination is useful when setting up a network or diagnosing problems within a network. Use the Trace Route API option of Tx Request Packets to transmit routing information packets to the originator of a DigiMesh unicast by the intermediate nodes. For a description of the API frames, see API operating mode.

If you enable the Trace Route API option, the device sends the unicast to its destination devices, which forward the unicast to its eventual destination. The destination devices transmit a Route Information—RI—packet back along the route to the unicast originator.

When a unicast is sent with the Trace Route API option enabled, the unicast is sent to its destination radios which forward the unicast to its eventual destination and transmit a Route Information—RI—packet back along the route to the unicast originator. For more information, see API operating mode.

The destination devices contain addressing information for the unicast and intermediate hop that generates the trace route packet, and other link quality information.

Example:

Suppose you unicast a data packet with the trace route enabled from radio A to radio E, through radios B, C, and D. The following sequence occurs:

• After the successful MAC transmission of the data packet from A to B, A outputs an RI Packet indicating that the transmission of the data packet from A to E was successfully forwarded one hop from A to B.
• After the successful MAC transmission of the data packet from B to C, B transmits a RI Packet to A. Then, A outputs this RI packet out its serial interface.
• After the successful MAC transmission of the data packet from C to D, C transmits a RI Packet to A—through B. Then, A outputs this RI packet out its serial interface.
• After the successful MAC transmission of the data packet from D to E, D transmits an RI Packet to A—through C and B. Then, A outputs this RI packet out its serial interface.

Route Information packets are not guaranteed to arrive in the same order as the unicast packet took. It is also possible Route Information packets that are transferred on a weak route to fail before arriving at the unicast originator.

Because of the large number of Route Information packets that can be generated by a unicast with Trace Route enabled, we suggest that the Trace Route option only be used for occasional diagnostic purposes and not for normal operations.