9. Backwards Compatibility

This section preserves the RFC text for RPL DAO Projection and root-initiated routing state, including P-DAO, P-DAO-ACK, P-DAO-REQ, PDR-ACK, VIO, SIO, RPI, SRH, Storing and Non-Storing P-Routes, Tracks, IANA registrations, and normative behavior.

Original RFC Text

9.  Backwards Compatibility

   This specification can operate in a mixed network where some nodes
   support it and some do not.  There are restrictions, though.  All
   nodes that need to process a P-DAO MUST support this specification.
   As discussed in Section 3.7.1, how the Root knows the node
   capabilities and whether they support this specification are out of
   scope.

   This specification defines the 'D' flag in the RPL DODAG
   Configuration option (see Section 4.1.7) to signal that the RPL nodes
   can request the creation of Tracks.  The requester may not know
   whether the Track can effectively be constructed or whether enough
   nodes along the preferred paths support this specification.
   Therefore, it makes sense to only set the 'D' flags in the DIO when
   the conditions for success are in place, in particular when all the
   nodes that could be on the path of the Tracks are upgraded.