Clarification of the 'on-mesh' prefix flag role

[konradderda]

Hello,
Even though I work with the Thread for some time I have always wondered what's the exact meaning of the 'on-mesh' flag of prefix configuration. I was looking for the answer both in the Specification and OT's source code but I could not find any description other than similar to "on-mesh flag indicates that prefix is on-mesh".

What are the implications of configuring a prefix without this flag? I know that it means that a given prefix is not a valid OMR prefix but that must be more and I am very curious 😄.

[jwhui]

On-mesh prefix indicates whether or not to perform Address Query to discover destination. It is analogous to the "on-link" flag in Prefix Information Option contained within IPv6 Router Advertisements.