The document defines a flag to mark NDP RA messages as originating from
an SNAC router.

As 6LoWPANs are likely to be typical stub networks, there may be relevant
IoT-related considerations in the broader context of SNAC, where this flag is
actually used.  However, within the limited, "define-and-register" scope of
this document, I struggle to find an IoT angle.  I guess topics like ND
optimisations/adaptations for 6LoWPANs, discussion on how constrained hosts on
the stub are protected from the infrastructure et similia will be tackled in
the main SNAC spec.

(RA-Guard is mentioned en-passant.  Maybe worth discussing it in the security
considerations -- e.g., mentioning RFC7113?)

# Nits (in --word-diff format):

* an [-autonomously-configuring-]{+autonomously configuring+} router

* The "SNAC Router" flag is[-router advertisement-] flag bit [-TBD.-]{+TBD in the RA Flags Extension Option.+}

* Devices that do not operate as SNAC routers[-[I-D.ietf-snac-simple]-]

* In environments that implement [-RA guard-]{+RA-Guard+}

* does not [-changes-]{+change+} these considerations