Subject: Re: [RAM] some draft proposed definitions

From: [email-masked] (Noel Chiappa)
Date: Tue, 12 Jun 2007 17:06:18 -0400 (EDT)

> Here is a draft proposal for terminology ... This is a starting point,
    > not an all-inclusive list.

After thinking about this for a while, I still think the best way to
proceed is to identify axes of characteristics or attributes of potential
names (as I suggested towards the end of my message yesterday), rather than
the definition of particular terms, because I'm not sure we're going to get
agreement on definitions.

In part, that's because i) we're not trying to name all possible N-tuple
(for N different axes) choice-sets along these axes - many of which
probably aren't useful - but only the 'desirable' or 'interesting' ones,
and people differ on which choice-sets are preferable (e.g. 'should the
topology-sensitive names name interfaces or hosts'), and ii) allied to
this, there are a limited number of words being tussled over.

Also, my sense is that discussing what the possible axes are is more likely
to be useful, because I think it will lead people to think more clearly
about the underlying fundamentals.

So, let me try and list the axes (and I'll then comment on your proposed
definitions in a separate message). Here's my list of axes of
characteristics or attributes of potential names, with the potential values
for each:

- Level: internetwork/transport
- Object-named: physical-network (aka subnet)/interface/host-'endpoint'-stack
- Locational: non-locational/network-topological/geographical
- Uniqueness: globally-unique/locally-unique (within some scope)/non-unique
- Directorizable: directorized/non-directorized
- Ubiquity: in-all-packets/not-in-all-packets
- Forwarding-tag: looked-at-by-switches/not-looked-at

What others are there?

Note that we can define useful terms without necessarily making picks along
all these axes, but we might then need further qualifers when using one of
these terms before it would clearly refer to one specific possibility.

For example, if we define 'locator' without specifying one particular
choice from the 'object-named' axis, we could then further refer to 'subnet
locator' (your definition of 'locator'), 'interface locator' (my definition
of 'locator'), or 'host locator' (IPv6 address definition).

	Noel

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From: [email-masked] (Noel Chiappa)
Date: Tue, 12 Jun 2007 17:19:34 -0400 (EDT)

> From: RJ Atkinson <[email-masked]>

    > not an all-inclusive list.

Now for a few comments on your proposed definition

    > Identifier:  An object that is used only for identification,
    >       never for forwarding packets or determining location.

A couple of problems with this one. First, the term "identifier" is a
generic term, sort of equivalent to "name", and I think trying to restrict
its meaning in any way is bound to cause confusion. Second, the term
"object" is generally used to refer to the entities or instances that names
are bound to; you probably want to use the term 'name' instead.

However, I do agree it's useful to have the concept of a name whose only
function is to indentify things, not say anything about where they are,
or anything else. But I think we need a different word/phrase..

    > Locator:   An object that is used only for forwarding packets
    >       or determining location, never for identification.

There have been designs in which interfaces were named at the internet
level with locators, and those locators were the only names those entities
had. As such, those locators identified (in the generic sense) those
interfaces. Of course, they did not 'identify' them (in the sense of
'identifier' above). Which shows the problem (above) with the term
'identifier'. (Also, "object" again.)

    > Address:   An object that with mixed semantics, where it is
    >      sometimes used for identity and sometimes used
    >       for packet forwarding.

Not only do the uses differ, but also the levels at which they are used,
what they name, etc. E.g. IPvN addresses are used as locators at the
internetwork level, and as identifiers at transport level.

	Noel