3.7.2. DODAG Loops

A DODAG loop may occur when a node detaches from the DODAG and reattaches to a device in its prior sub-DODAG. In particular, this may happen when DIO messages are missed. Strict use of the DODAGVersionNumber can eliminate this type of loop, but this type of loop may possibly be encountered when using some local repair mechanisms.

For example, consider the local repair mechanism that allows a node to detach from the DODAG, advertise a Rank of INFINITE_RANK (in order to poison its routes / inform its sub-DODAG), and then reattach to the DODAG. In some of these cases, the node may reattach to its own prior-sub-DODAG, causing a DODAG loop, because the poisoning may fail if the INFINITE_RANK advertisements are lost in the LLN environment. (In this case, the Rank-based data-path validation mechanisms would eventually detect and trigger correction of the loop).