Re: host-centric draft

[Erik Nordmark <Erik.Nordmark@sun.com>]

> So the question is: can we detect the actual reachability using probes 
> fast enough that we don't feel we also need to look in the routing 
> tables? If end-to-end is 30 seconds while routing table is 30 
> microseconds, then sure, I agree that the latter is useful. If 
> end-to-end is 3 seconds, maybe having to wait this long some of the 
> time is better than importing all this BGP complexity. If it's 300 
> milliseconds I'm sure it is.

That's on the benefit side, but also have too look at the cost side
in terms of scaling.
If all hosts perform e2e probing of all the local/peer locator pairs
this might add up to a lot of packets; might be more than the amount of
data packets that are exchanged in some cases (imagine hosts being sensors
which only send a data packet every 30 seconds and now you add probing 4 or
so local/peer locator pairs!).

If we care about *site* (and not *host*) multihoming one could try to
have hosts share the information they learn from probing with their
neighboring hosts. But that leads more or less to reinventing
a routing protocol.

  Erik