Subject: Re: [rrg] Terminology, 2nd pass

From: [email-masked] (Noel Chiappa)
Date: Mon, 30 Mar 2009 12:27:18 -0400 (EDT)

> From: Dino Farinacci <[email-masked]>

    > From a network perspective, if a switching node makes a forwarding
    > decision based on an [field] in a packet header, then that [field] is a
    > locator.

Dino, I hear what you're saying: I have made a very similar point before,
but.... I called those fields 'forwarding tags'. (Not that I have any
particular deep attachment to that particular name, I'd be happy with pretty
much any term.)

The reason I picked a new term there was simple: I think we need terms for
_both_ of these concepts (what others call 'locators', and 'forwarding
tags'), and overloading both meanings onto one term is just confusing.

Like I said earlier, it's true that one can use a MAC address, or any similar
unique identifier, for flat routing. (In which case it's what Tony defined as
an 'identifier', for the interface - i.e. just a name which denotes one
particular instance of a set of objects.)

However, for _non-flat_ routing, one needs a set of names with more
_structure_ in them, and it's names of that type (ones with built-in structure
which is related to the _location_ of the thing they are naming), which most
people mean when they say 'locator'.

And clearly, one can't use the same term for both of these (quite different)
concepts, without great confusion...

	Noel

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From: Dino Farinacci <[email-masked]>
Date: Mon, 30 Mar 2009 09:31:25 -0700

I think we need to keep all this terminology stuff simple. And not  
have too many terms. What comes out of this group will pro-market or  
negative-market locator/ID separation. And you don't want people to  
react "this locator/ID separation stuff is more trouble then it is  
worth".

Dino

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From: Scott Brim <[email-masked]>
Date: Mon, 30 Mar 2009 12:56:27 -0400

> And clearly, one can't use the same term for both of these (quite
> different) concepts, without great confusion...

But where's the difference?  This is where Dow's axes come in handy.
The more structure there is in the name, the less work routing has to
do.  On one end of the spectrum you have a strict source route (or a
circuit or a PIP "address").  On the other end you have MACs.  It's
all routing, it's all forwarding, it's all "locators" (meaning things
used by forwarding), but there is a continuum of how much structure
there is and how much work you have to do.  

So there is clearly a difference between a something that cannot be
used by forwarding for any purpose and something that can, but within
the group that can, structure is not a qualitative difference -- the
alternatives are points along a dimension of how structured they are.
Thank you Dow.

Scott

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From: Scott Brim <[email-masked]>
Date: Mon, 30 Mar 2009 12:59:32 -0400

> react "this locator/ID separation stuff is more trouble then it is

For me it's about the meaning of 'locator/identifier separation', and
mainly in endpoints.  The essential point is to get identification
functions to stop using data that might have to change when topology
changes.