Hi Ted,
I agree with you on the notion that we shouldn't publish anything that we
know already that will need fixes or does not work properly for the intended
use at this point. However, I think it is completely proper to revise
specifications based on operational experience - ever rather quickly after
publishing as a PS. Though, seldom done I have understood it is has been
even the original idea of the three step standardization process.
However, that is not my main point. And I don't quite agree that this
document in its current format is in a shape where we would have to revise
it right after publishing.
I would like to comment a bit on your proposal to make the MN-AR draft a
normative reference, and moving MN-AR to standards-track. First of all, I'm
happy to say that the MN-AR draft has been revived and can be found at
http://www.ietf.org/internet-drafts/draft-ietf-netlmm-mn-ar-if-03.txt
Secondly, taking into account the multiple customers for the pmip6 and the
multitude of environments where PMIP is either going to be used or
potentially going to be used (3GPP, 3GPP2, Wimax to my understanding) I
don't think it is possible to write a MN-AR draft that would cover
adequately those networks and be really useful for them. I think the purpose
of the MN-AN is not to show how PMIP6 should be deployed, but how it could
be deployed. I however do agree that MN-AR draft should go forward in the
working group and it should not be forgotten.
I cross-posted this to the netlmm mailing list to make sure everybody knows
this discussion is going on.
Cheers,
Jonne.
On 2/14/08 3:01 AM, "ext Ted Hardie" <hardie(_at_)qualcomm(_dot_)com> wrote:
Summary: One issue needs resolution.
First, let me start by saying that -09, which was put out for Last Call, was a
substantial
improvement over the -08. I normally read Last Call documents using a diff
tool,
and the number of really solid additions in this update was quite high. I was
a bit
surprised, given the extent of the new text, that there was no WG last call,
but
I assume that the WG is reviewing the changes in parallel. I assume that the
issuance
of -10, which came out during the last call, was a response to one or more
reviews
from the WG or solicited experts.
To call out one particular improvement, I found the update's language around
multi-homing much clearer, and I believe the risk of assignment of the same
address to multiple interfaces is much reduced in this version. Given the
potential consequences (watching your stack scream "I'm melting! I'm
melting!"
as someone entertainingly put it), that's a really good thing.
There are still some opportunities for editorial update, and I hope that as
the IESG enters its discussions that some of those are targets for resolution.
I'd particularly like to see even more clear light on the description in
bullet 4 of Section 6.9.1.1, as "predictably knows" is not as clean as
it might be. (The current sentence is: "The Handoff Indicator field MUST be
set to
value 1 (Attachment over a new interface), if the mobile access gateway
predictably
knows that the mobile node's current attachment to the network over this
interface is not as a result of an handoff of an existing mobility session
(over
the same interface or through a different interface), but as a result of an
attachment over a new interface. "). But that is really a language clarity
problem, at least I hope, at this point.
The big issue that remains is actually one that starts from the scope creep.
I was on the IESG during the period when this charter was approved, and it
was clear at the time that some of the limitations being put in were intended
to focus NETLMM on cases where nodes were re-associating at layer 2 with the
same network. The charter says, for example: "The protocol will not attempt
to hide handover between two separate interfaces on the mobile node.".
This document (and, as I understand it, the working group discussion for some
time)
has gone beyond that initial scope. A good portion of this document's
complexity
is because it does handle the multi-interface case. While it would have been
nice
to have the charter updated to state the new scope, I don't personally have a
problem with the scope. I am concerned, however, that the design constraints
changed with that new scope and that other parts of the charter are limiting
folks' understandings of what can be done here, when those restraints are
really
salient for the single layer 2 initial scope.
To put it simply, given the inter-technology handoff, signalling from the
mobile node
to the network is one of the clearest and most likely to be interoperable ways
to achieve
the correct behavior in some of the base cases. At the moment, because the
mechanisms
for setting the handoff indicator do not necessarily involve the mobile node
(and are
appear to be below IP where between the mobile node and the networ), a mobile
node with multiple interfaces will not always be able to signal that it
desires handoff or
prefers multihoming. The document is now clear that in that case it gets
multihoming. That's a tremendous advance over the previous state. But the
really
big win here would be to enable the signaling . As it stands, the operations
are based
on the handoff indicator provided by the MAG, but the document does not
provide
any information on how the MAG will know this information. There certainly
will
be cases where a network architecture will allow the MAG to use layer 2
indicators
or other mechanisms, but there will also be cases where that set of mechanisms
is inconsistently available. Adding the higher-layer signalling makes this a
complete solution.
I'm concerned that sending the document out in its current state will either
require
a quick re-spin at PS to enable this once the issues arise in deployment or
that some of
the contexts in which this is intended to be used will work around the problem
in ways which will hinder an interoperable, long-term deployment.
I am very conscious, however, that there is considerable time pressure on this
document. I propose the following as a way forward which should not add any
significant delay.
1) Add an explicit, normative reference to draft-netlmm-mn-ar (which would
need to be revived) as the basis for a forthcoming above-IP signalling
mechanism,
using an RFC-Editor's note.
2) Put draft-netlmm-mn-ar on the standards track, but make an explicit
downref statement for this document to the internet-draft. This would allow
this document to progress without delay, but provide a reference for those who
will be deploying this in contexts which do not have the same
highly-structured
network management of the networks for which this is urgent. When
draft-netlmm-mn-ar is published, it would be available, of course, to both
network types.
3) Go ahead with IESG processing on this document on the basis of the existing
Last Call
date, with the understand that the IESG would reconsider only if the second
Last Call
with the explicit downref raised new issues. IESG consideration prior to the
end of a Last Call already occurs in some cases, and it certainly could be
used in this case to meet the
time pressures.
I'm aware that the charter states that there should be no signalling required
between the mobile and the network. In the context of the original design
scope,
that should have been read quite strictly. In the context of the current
design scope,
I believe we have to distinguish between making something required and setting
a standard way of handling something in the inter-technology case. I do not
believe
that adding this normative reference would make it required. It would simply
show how the IETF intended to meet the need for an interoperable mechanism
for signalling where the mobile node had the capability and interest. Where
it did
not, the basic mechanisms in this draft would suffice.
I understand that this has been an active, and at times contentious, area of
discussion,
and I do not want this last call comment to fan any old flames. As an APPs
guy, trust
that I'm in favor of pretty much anything that reduces the need for updated IP
addresses
and all the concomitant pain. I also see us about to miss an opportunity
here, by
setting out a toolkit that is missing a critical tool. I don't believe the
time pressures
here should or need to stop us from building the full toolkit, even if the
first shipment
of toolboxes goes out simply with the right shape cut out, to be filled later.
regards,
Ted Hardie
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Jonne Soininen
Nokia Siemens Networks
Tel: +358 40 527 46 34
E-mail: jonne(_dot_)soininen(_at_)nsn(_dot_)com
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