In RPL (Routing Protocol for Low Power and Lossy Networks), to maintain a DAG (Directed Acyclic Graphs), each node periodically generates DIO messages triggered by the trickle timer.
If the rank value of a node has changed after recalculation (due to update of ETX after data transmission), does the node issue a DIO message to broadcast the updated rank immediately or waiting for the trickle timer?
RPL supports mechanisms that may be used for local repair within
the DODAG Version. The DIO message specifies the necessary
parameters as configured and controlled by policy at the DODAG
root.
RPL nodes transmit always DIOs using a Trickle timer. however, you can find the details in paragraph 8.3 specification RCF6550.
In RPL , If a node discovered inconsistency ( in your case Rank changed.. Usually it is implementation decision whether change in the rank is considered inconsistency or not ). A node would return back to THE MINIMUM INTERVAL, , choose a random time to schedule a DIO to transmit at . Provided it has not received up to K consistent DIOs with its own DIO, then, a DIO would be transmitted at that randomly scheduled time. However if the rank change was not considered inconsistency , then the nod will wait for Trickle time
RPL supports mechanisms that may be used for local repair within
the DODAG Version. The DIO message specifies the necessary
parameters as configured and controlled by policy at the DODAG
root.
RPL topology formation:
The DODAG(destination-oriented directed acyclic graph) is built based on the information of DODAG information object (DIO) messages (ICMPv6 messages defined in RPL). These messages contain a DODAGID, rank information, and objective function.
DIO packets are first sent by the root and then periodically by each node of the DODAG after calculation of its own rank. The rate at which the DIO messages are being sent is dynamically tuned, using the Trickle algorithm[16]. In the absence of changes in the DODAG structure, the algorithm doubles the period of the DIO messages after each transmission of a DIO messages; otherwise, the trickle timer is reset to send the DIO messages more frequently in order to propagate the updated DODAG quickly.
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