I had written another lengthy reply to Tony's last message, but I'm not 
going to send it right now - maybe I'll wait, or maybe I'll send it in 
private mail.  I'm sending a briefer reply because I want to focus 
attention on a question which seems fairly important to Tony's position:



One of the assertions that Tony seems to be making is that SLs can be
used to communicate to applications when policy forbids them from talking
to one another.    (Tony, if I'm mistating this, please restate it)

So for instance if a process resides on a host which only has an SL 
address, and it wants to communicate with a peer for which it only has 
a global address, then the process can infer that it is forbidden as 
a matter of policy from communicating with that peer.

Or perhaps if process A lives on a host with both global and SL addresses,
and it has only a SL address for the host on which process B resides,
then A can infer that B is forbidden from communicating off-site.

(Offhand I haven't thought of other inferences that could be made - 
certainly if both hosts have both SL and global addresses then 
you can't assume that the hosts are allowed to connect.)

Is there a widespread idea that it's reasonable for apps to make
these kind of inferences?  



Personally, I don't think either of those inferences are reasonable - 
there are too many situations where a host can be temporarily without
a global address (but not forbidden to communicate externally as a 
matter of policy), and too many situations where a process might know
some but not all of the addresses at which a potential peer might be
reached (so the lack of knowledge of a global for that peer doesn't 
imply anything about policy).

Keith
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