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Re: about draft-arkko-multi6dt-failure-detection-00.txt

Francis Dupont wrote:

 - in 3.2 "Theoretically, it is also
   possible for hosts to learn about routing failures for a particular
   selected source prefix, even if no protocol exists today to
   distribute this information in a convenient manner."
   I disagree about the last part: there is a well known and simple
   protocol to announce routing failures for a source prefix: deprecate
   it, i.e., send RAs with zero preferred lifetime in the prefix info.

In doing so you would be overloading two very different semantics on the deprecated state:
- this prefix will stop working in the future (sometime after the valid
lifetime expires) so don't use addresses in this prefix for new
communication; no effect on existing communication
- this prefix is currently not working; immediately switch existing
communication (as well as new communication) to use an address from a
different prefix.

Those two semantics are in conflict.

So if we want the second semantics one would need to carry that semantics. Of course, it wouldn't be hard to define some extension to the router advertisements (and the router renumbering protocol if we don't want to manually configure the routers) to say this; a single bit in the prefix option might be sufficient.

   Erik