Subject: Re: [rrg] definitions - alternate view

From: [email-masked] (Noel Chiappa)
Date: Sat, 4 Apr 2009 20:36:49 -0400 (EDT)

> From: William Herrin <[email-masked]>

    >> That would make an MPLS tag an "address". Somehow I don't think so.

    > Why not? What characteristics of what you think of as an address are
    > missing from the typical use of an MPLS tag?

Um, because to me, an address, like its real-world prototype, says _where_
you are, in some way that anyone can grok, independent of either who they,
where they are, or how they get to that destination. (Yes, NAT complicates
the issue for IPv4 addresses.)

An MPLS tag identifies (at best) a particular path. It identifies a
particular destination only as a _side-effect_ (the same way that my
land-line phone number identifies my street address as a side-effect).

    > From: Tony Li <[email-masked]>

    >>> If we really need a name for some particular crisp definition ...
    >>> ... pick a new word/phrase, don't try and morph an existing word.

    >> If the chair is amenable to that idea, so am I. 

    > Normally, I would love that idea. However, our specific request is that
    > we define the terms locator and identifier.

I don't see a conflict here. We can define locator and identifier, as
requested - and on our own, for our own use, we can define a term to mean
'field(s) in the packet used to make next-hop forwarding decisions' - along
with terms for any other meanings that seem useful to have terms for, meanings
_other_ than the defined meanings for address, locator and identifier.

	Noel

---

From: William Herrin <[email-masked]>
Date: Sat, 4 Apr 2009 20:59:32 -0400

On Sat, Apr 4, 2009 at 8:36 PM, Noel Chiappa <[email-masked]> wrote:
>    > From: William Herrin <[email-masked]>
>    >> That would make an MPLS tag an "address". Somehow I don't think so
>    > Why not? What characteristics of what you think of as an address are
>    > missing from the typical use of an MPLS tag?
>

Hi Noel,

You can send mail to my mother via the postal address:

General Delivery
Dora, MO

That address probably fails to reveal that she lives just north of
Kitty Hawk NC.

Defining address in terms of where you are, whether geographically or
topologically, offers a very slippery definition. It's hard to give it
any kind of rigor in the face of anycast, multicast and load
balancing.

>    > Normally, I would love that idea. However, our specific request is that
>    > we define the terms locator and identifier.
>
> I don't see a conflict here.

I'd like to a see a definition of locator and identifier which is
rigorous and consistent both with our theoretical constructs and with
existing network protocols. Giving the community a sloppy definition
of identifier and locator would diminish us.

Regards,
Bill Herrin

-- 
William D. Herrin ................ [email-masked]  [email-masked]
3005 Crane Dr. ...................... Web: <http://bill.herrin.us/>
Falls Church, VA 22042-3004