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RE: Let's abolish scope [Re: Unicast scope field (was: Moving forward on Site-Local and Local Addressing)]

Brian E Carpenter wrote:
> ...
> > No, a link must be wholly contained within a site, and by 
> definition 
> > anything that is less than global fits wholly within global. Yes 
> > multiple local regions can overlap, but that does not 
> invalidate the 
> > overall model.
> I think it does, because it makes "less than global" 
> ambiguous. Does it mean "my intranet", "my intranet plus a 
> VPN to company X", "a VPN to company X but not my intranet", 
> "my VPNs to companies X and Y plus a secure subset of my 
> intranet", or a combinatorial number of similar choices?

Why do you assume it needs a predefined meaning? I am approaching this from
the perspective that the local network manager defines what it means in
context. They do this all the time with routing areas, so why is a scope
context any different?

> ...
> > I agree with the last sentence, but not the premise about 
> defining an 
> > API. One way to describe a desired outcome would be, bind 
> to a limited 
> > range address associated with ibm.com.
> Indeed. Good example. It turns out to be a list of about 139 
> IPv4 prefixes, manually maintained. I got that from my VPN 
> setup. That's exactly the problem.

So add sub-domains whenever there is a real difference in usefulness of any
prefix in the list (fwiw: I assume that the 139 are artifacts of history,
and there are probably less than 6 real groupings).  Since these are unique,
once the system has one it will be clear which interface or context it
should be used with.

> ...
> > > I think we'd be better off to simply forget about address scope.
> > 
> > We could choose to ignore the most commonly deployed segment of the 
> > existing Internet, but how useful would the results be.
> That's not what I'm suggesting. I'm suggesting that trying to 
> solve it with a simple concentric-circles model of scope is 
> impossible.

I doubt it is impossible. More challenging than global flat routing? Yes,
but not impossible. 

In any case, I think the point you are bringing up is that truly global
routing is a rare exception, and the vast bulk of the environment lives in
the middle space. If so, I agree which leads to the question, why are we
trying to optimize the address space and api's around the least likely usage
scenario? I realize it makes app development simpler to assume the world is
flat, but if the bulk of reality says otherwise, shouldn't we acknowledge
that and bring app development into the 21st century?


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