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