[6lowpan] 6lowpan-nd-15 node mobility and default router(s)

["Dijk, Esko" <[e-mail]>]

Dear all,

A comment on Section 1.3 of 6lowpan-nd-15, last bullet:

When a node moves away from the registered default router, it SHOULD first de-register by
sending a registration message with zero lifetime and then
registers with a new default router that is reachable

- it should probably say "moves away from _a_ registered default router" here, because there may be more default routers? Or otherwise if there is only one that should be made explicit as a special case.
- If a node has >1 default routers, it could also de-register from one without registering with a new router, or not?
- why shouldn't a node register first with a new default router before de-registering with the router it is moving away from? This ensures that the node remains reachable. This works only of course in those cases the new router is already available prior to the move.
- finally, this text should probably not be under the "1.3 Assumptions" section because it describes normative node behaviour in case of mobility, not only an assumption.

best regards,
Esko



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