Subject: Re: [rrg] question about the Identifier/Locator separation

From: [email-masked] (Noel Chiappa)
Date: Fri, 27 Mar 2009 23:50:19 -0400 (EDT)

> From: <[email-masked]>

    > My problem is that in traditional routing systems, the IPv4 address
    > serves both the identifier and locator, and the routing table growth
    > and routing dynamics happens to the routing system. When identifier and
    > locator separates, the routing system will have much less pressure, but
    > what about the mapping system. It seems that the pressure has been
    > transfered from the routing system to the mapping system. Can the
    > mapping system handle the large number of mappings and dynamics?

This is a good observation. My answer has two parts.

First, the path selection (i.e. routing) system has a hard enough time as it
is - trying to handle the network growth, dynamics etc is already hard,
without supporting other things too. So we _have_ to split things up into two
subsystems, because the network has gotten so large.

However, you are correct that if we want to support things like a certain
rate of change in identity->location bindings, the mapping system has to be
designed to handle that. I think the question is not so much 'can we build a
system that supports a given rate of change in bindings', or 'can we build a
system in which after a binding change, the change is propogated to everyone
who has a copy of that binding'. The question really is 'can we meet a given
desired performance target with an acceptable level of cost'. There's no way
to answer that without actually designing the mapping system in detail,
though.

	Noel

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From: Tony Li <[email-masked]>
Date: Fri, 27 Mar 2009 22:08:33 -0700

> to answer that without actually designing the mapping system in detail,

And, to be even more explicit, we only have one good example of such a 
mapping system: DNS.  We've seen that it does scale, and, for the most 
part works reasonably reliably at its job.  It does have some drawbacks 
(attacks of the root servers, cache corruption issues, low update rate, 
lack of DNSSec deployment, etc.), but it does serve as proof of concept 
to say that there is probably SOME mapping system that we can construct 
that has some reasonable set of properties.  Perhaps not perfect, but 
then, what is?

Regards,
Tony