Subject: Re: [lisp] WG Review: Locator/ID Separation Protocol (lisp)

From: [email-masked] (Noel Chiappa)
Date: Wed, 18 Mar 2009 01:14:08 -0400 (EDT)

> On 2009-3-17, at 19:04, Brian E Carpenter wrote:

    > The entity that LISP calls an EID is in fact a locator; it's simply a
    > locator of limited routeability.

Calling it a "locator" is even 'wronger' than calling it an EID, alas.

If the mapping-encapsulation takes place at the first-hop router (which I
expect to be an eventual evolutionary step), _at the internetworking level_
the properties of the LISP EID are extremely similar to an IEEE Interface ID,
which nobody would call a locator. All they both do is identify (in a
globally unique way) an interface. It certainly would have no more inherent
location information in it than an IEEE IID does.

And that doesn't even touch on the possibility that the interface naming
functionality would _also_ be leached out of the LISP EID, leaving it as
purely a location-less identifier for a stack (which is, exactly, an EID...)

Please see my previous length message to the RRG list (sigh, too many lists):

  http://www.irtf.org/mail-archive/web/rrg/current/msg04612.html

which discusses at more length the issue of the changing semantics of the
LISP EID over time, and in particular how the 'location' functionality is
incrementally leached out of it.

    > I believe it should be called a LLOC (local locator), with
    > consequent changes to the charter text. ... the risk in the current
    > terminology is that people will be confused for ever.

I don't know why the original LISP team decided to call it an EID. (I wasn't
involved in the project at that point.) The problem now with changing it is
that, as a LISP term, it has been used for a long time now, and I'm not sure
it's really plausible to change it. (People will keep saying 'LISP EID',
I suspect.)

But if it is changed, it needs to be an _entirely new term_, since _any_
existing term is at best an inexact fit to the particular, detailed (and
probably not constant over time) semantics of the LISP EID.

	Noel

---

From: Eliot Lear <[email-masked]>
Date: Wed, 18 Mar 2009 11:47:21 +0100

To Robin's and Brian's points, I think the charter makes it very clear 
that there can be no perfect use of terminology just because the 
function of the IP address is overloaded.  As such, can we not accept 
this fact and move on?  The real work lies elsewhere, wouldn't you agree?

Eliot

---

From: Sam Hartman <[email-masked]>
Date: Wed, 18 Mar 2009 07:36:07 -0400

>>>>> "Eliot" == Eliot Lear <[email-masked]> writes:

    Eliot> To Robin's and Brian's points, I think the charter makes it
    Eliot> very clear that there can be no perfect use of terminology
    Eliot> just because the function of the IP address is overloaded.
    Eliot> As such, can we not accept this fact and move on?  The real
    Eliot> work lies elsewhere, wouldn't you agree?

I'm going to push back very strongly on terminology arguments.  They
tend not to be productive.  Instead, I'd like people to describe what
is unclear about the charter and we can work on fixing that.  That may
or may not involve changing terminology, but I have high confidence
that we'll at least have a more constructive discussion than if we
fight first about the terminology.

Bryan, Margaret and Lixia have all identified what I believe is
roughly the same issue: EIDs have local topology and are locally
routable.  They contain three portions: a part that identifies an
organization.  That part really does seem to be an identifier.  They
contain a portion that identifies a subnet within an organization and
a portion that identifies an interface.  How large each of these
portions is may change as LISP deployment changes.

The chairs are aware that the chartar does not currently describe this
issue accurately enough[1] and will propose resolution.

[1] I understand that until the WG is created it is more what Jari
thinks than what the chairs think that matter.

Robin has identified a similar issue that is not entirely the same: we
need to clarify that EIDs are IP addresses.  I don't want to argue
about whether they are or are not the same namespace.  Are ULAs in the
same namespace as PA IPV6 addresses?  What about 6-to-4 address?  That
doesn't seem productive.  It does seem productive to point out that
EIDs are IP addresses and that there will definitely be cases where an
end-system cannot tell whether an address is an EID or an RLOC.  There
may be cases where an end system can tell that something is an EID,
for example, if EIDs are allocated from well-known IPV6 prefixes.  I'd
appreciate comments on whether this level of detail belongs in the
charter.

---

From: Eliot Lear <[email-masked]>
Date: Wed, 18 Mar 2009 14:28:02 +0100

On 3/18/09 12:36 PM, Sam Hartman wrote:
> organization.  That part really does seem to be an identifier.

In the context of LISP it is the only identifier bound by the mapping 
system.

> thinks than what the chairs think that matter.

Tweak if you must, but I stand by my original statement, that the real 
work lies elsewhere.

> doesn't seem productive.

I agree.

> It does seem productive to point out that

If you're looking for text to add, from my point of view it would be 
this: unchanged semantics of an IP address from the end host's 
perspective meets a design goal of not requiring end host changes.

That's a big deal.  Anything that tweaks that goal should be met with 
great skepticism because of the potential costs.

I myself have one nit with the charter.   LISP and the similar map-encap 
proposals are about as potentially harmful as any other L3VPN  
mechanism, and it seems excessive to label LISP any more harmful than 
those.  It seems sufficient to label the work experimental for now.

Eliot

---

From: "Templin, Fred L" <[email-masked]>
Date: Wed, 18 Mar 2009 08:53:10 -0700

Noel,

> -----Original Message-----
> From: Noel Chiappa [mailto:[email-masked]]
> Sent: Tuesday, March 17, 2009 10:14 PM
> To: [email-masked]
> Cc: [email-masked]
> Subject: Re: [lisp] WG Review: Locator/ID Separation Protocol (lisp)
> 
> 

I'm not sure about the analogy. If I assign the same
interface ID on multiple interfaces of the same node,
it works fine (as long as they're not attached to the
same link). But, if I assign the same IP address on
multiple interfaces of the same node (i.e., if the
system even let me do that), the behavior might be
more difficult to predict.

I think there is no way around acknowledging that the
LISP "EID" is actually an IP address that is routable
within a limited scope - even if only node-local. As
has been said before then, if you really want a *true*
endpoint identifier, HIP provides an example.

> probably not constant over time) semantics of the LISP EID.

I am still offering Endpoint Interface iDentifeir (EID);
wouldn't take much of a tweak to the documents.

Fred
[email-masked]

> 
> 	Noel
> _______________________________________________
> lisp mailing list
> [email-masked]
> https://www.ietf.org/mailman/listinfo/lisp