How do nodes form networks?

The following was taken from the JenNet Stack User Guide, JN-UG-3041, which at the time of this document is available at http://www.jennic.com/support/user_guides/jn-ug-3041_jennet_user_guide :

Routers and End Devices can join an existing network already created by a Coordinator. Both Routers and the Co-ordinator have the capability to allow other nodes to join the network, but this feature of the node can be enabled or disabled (the node also has a maximum child capacity - see Section 2.2.3). The join process is as follows:

  1. The new node first scans the available channels to find operating networks and identifies which one it should join. Multiple networks may operate in the same channel and differentiated by their Network Application IDs.

  2. The node may be able to “see” multiple Routers and a Co-ordinator from the same network, in which case it selects which one it should connect to. This is determined by the following three criteria - first, the nodes highest up the tree are considered, then the one with the fewest existing children and, if there is still more than one candidate, the one with the strongest signal is selected.

  3. The node then sends a message to the chosen Router/Co-ordinator, asking to join the network.

  4. The Router/Co-ordinator determines whether it is currently allowing devices to join and ensures that it has not already reached its maximum number of children. If these criteria are satisfied, the Router/Co-ordinator then allows the device to join.

  5. The stack sends a “Child Joined” notification message to the application on the Router/Co-ordinator, where this message contains the child’s address.

  6. The node is now connected to the network and ready to establish a route. The handshaking between parent and child when a new node joins the network is known as association.

Note that changes to the node hierarchy under the JenNet tree may, and often do, occur. This may happen because of changes in RF signal strength between nodes (say from a temporary interference) resulting in excessive packet losses, or as a consequence of a power event to one or more router nodes. When the reformation of nodes in the JenNet tree occurs, this can make some previously-captured “Pan info data” in the station invalid or “stale”. For related details, see PAN info data.