15. Suggestions for Interoperation with Neighbor Discovery

This specification directly borrows the Prefix Information Option (PIO) and the Route Information Option (RIO) from IPv6 ND. It is envisioned that, as future specifications build on this base, there may be additional cause to leverage parts of IPv6 ND. This section provides some suggestions for future specifications.

First and foremost, RPL is a routing protocol. One should take great care to preserve architecture when mapping functionalities between RPL and ND. RPL is for routing only. That said, there may be persuading technical reasons to allow for sharing options between RPL and IPv6 ND in a particular implementation/deployment.

In general, the following guidelines apply:

• RPL Type codes must be allocated from the RPL Control Message Options registry.

• RPL Length fields must be expressed in units of single octets, as opposed to ND Length fields, which are expressed in units of 8 octets.

• RPL options are generally not required to be aligned to 8-octet boundaries.

• When mapping/transposing an IPv6 ND option for redistribution as a RPL option, any padding octets should be removed when possible. For example, the Prefix Length field in the PIO is sufficient to describe the length of the Prefix field. When mapping/transposing a RPL option for redistribution as an IPv6 ND option, any such padding octets should be restored. This procedure must be unambiguous.