34 AVR2070 8240B-AVR-06/09
Figure A-4-3 In-Direct Association Message Sequence
End/Router Node Pan Coord Node
Association Request Direct
Association Response Indirect
Router Node
Association Request Indirect
Association Response Direct
When a router node starts up, the router does the following steps:
1. Perform the steps that an end node does, as outlined above. This results in
the router becoming associated to the network, with a short address and a
parent.
2. Listen for beacon requests. For each beacon request, issue a beacon frame.
If the router has reached its limit of router/end nodes, or if it has lost its
network connection, then it does not return a beacon frame. The beacon
frame contains:
• PAN ID of the network.
• Short address of node sending the beacon.
• Special ID byte (application specific).
• Number of hops to coordinator (zero means that the beacon frame
was sent by the coordinator).
3. Listen for frames received from parent or children nodes.
• Routing frames – this frame has a payload which is a list of short
addresses that describe a route through a string of routers to a
destination node. For this kind of frame, remove the first short address
from the list, and re-send the frame to the short address removed from
the list. Also, store the address of the next router in the chain, so that all
further data packets will be sent to this child node from now on.
• For all other frames – dispatch to other nodes in the following order. The
word “my” denotes the router’s point of view.
• If the final destination address is my child node, then send the packet to
the child.
• If the frame was sent from my child node, send the packet to my parent.