RE: Unreachability detection at tunnels servers WAS: RE: Comments on zeroconf draft

["Karen E. Nielsen (AH/TED)" <karen.e.nielsen@ericsson.com>]

Hi Christian,

> 
> > Now a standard last hop IPv6 router on a lan monitors the 
> reachability
> of
> > its lan hosts using NUD and notifies of black holes by sending IPv6
> > destination unreachable
> > back to origin. (Actually the ICMP is generated when a NUD 
> cache times
> out
> > and address resolution cannot be performed anew, but in 
> this context 
> > that's a detail.)
> 
> I don't think that in this age of firewalls, any application 
> should rely
> on ICMP packets for detecting that a destination is not 
> reachable. Most
> firewalls are programmed to silently drop the traffic they 
> don't like...
> 

I don't disagree. The problem is with the alternative.

> That being said, Teredo hosts and relays can in fact use the Teredo
> bubble mechanism to verify that their peers are reachable.
> 

Does this mean that Teredo Servers perform (or are meant to perform, i.e. SHOULD - ?)
some kind of RFC 2461 NUD-like reachability
mechanism using the bubble mechanism, when the reachability of end-host
are in question ?
- Or is it rather so that vendors if they like could implement this ?

BR, Karen