Re: ITU-T SG15 comments on draft-ietf-ccamp-transport-lmp-00.txt

["Adrian Farrel" <adrian@olddog.co.uk>]

Thanks Steve,

And available in glorious HTML

Authors, the relevant text from the liaison is included below. I think we
can assume it is no different to what will receive through the formal
channels.

Adrian

=======

We have several questions of clarification, e.g., in section 3.1
(paragraph 2) of the I-D, "The separation between the two processes and
corresponding two name spaces has the advantage that the discovery of the
transport plane can be performed independent from that of the control
plane (and vice-versa), and independent of the method used in each name
space. This allows assigning link connections in the control plane without
the link connection being physically connected."
  1.. What is the intention of the term independent, for example, could it
be indicating at a different time or different approaches?

  2.. In the last sentence, is "assign" used in the context of the
management plane, meaning management plane provisioning?  Is it assumed
that the transport plane resources supporting the link connection
endpoints exist or do not exist?
In section 4.2 (paragraph 2) of the I-D, "G.8080 refers to a component
link as a variable adaptation function i.e. a single server layer trail
dynamically supporting different multiplexing structures." This could be
interpreted as indicating G.8080 defines the term "component link".
G.8080 does not use this term.  Some clarification would be beneficial.
Initial reviews of the draft document have raised concerns about the
possible misinterpretation in the usage of the term 'TE link'. As the
draft notes, the definition of a TE link is concise. Some more clarity
would be appreciated.  Our current understanding of this term includes the
following:

  1.. A TE link may be composed of resource from multiple (G.805) layers
in parallel.  If so, this is an important distinction as an SNPP link is
in a single layer only.

  2.. An SNPP link may contain SNP link connections from various links
(e.g., different STS-1s from a set of parallel OC -48 trails).  It is not
clear if this is also true for TE links.  We think it may, but it is not
stated.

  3.. SNPPs exist at different routing levels (not layers) and thus an
SNPP link at a higher level can encompass SNPPs at a lower level (see
Section 6.2.2 of G.8080 Amendment 2, which is attached for your
convenience).  We think TE links may do this with bundles and FAs, but the
definition is not clear to us.
Please advise if this is a correct understanding or not.  This may have an
impact on the terminology mapping in the draft.  We think it would be
beneficial to have a TE link definition that enables these distinctions to
be understood.
In the table in section 4.2 "CP" is mapped to "Interface".  A Connection
Point is more closely related to a timeslot, wavelength, etc. rather than
to an entire interface.  Similarly "CP Name" is mapped to "Interface ID"
while it might more closely relate to a "Label".  Joint discussion of the
terminology mapping may be beneficial in reaching alignment on the most
accurate mapping.


----- Original Message ----- 
From: "Stephen J Trowbridge" <sjtrowbridge@lucent.com>
To: "Adrian Farrel" <adrian@olddog.co.uk>
Cc: <ccamp@ops.ietf.org>; "Don Fedyk" <dwfedyk@nortelnetworks.com>;
<osama@nortelnetworks.com>; "Brungard, Deborah A, ALABS"
<dbrungard@att.com>; "Jonathan Lang" <Jonathan.Lang@sonos.com>; "Dimitri
Papadimitriou" <Dimitri.Papadimitriou@alcatel.be>
Sent: Friday, December 17, 2004 6:53 PM
Subject: Re: ITU-T SG15 comments on draft-ietf-ccamp-transport-lmp-00.txt


> Adrian,
> I don't know why the TSB would not have sent out the liaison statements
> generated from December 3. In any case, all of the liaison statements to
ccamp
> that were generated in our meeting are available at the usual spot in
the FTP area:
>
>
ftp://sg15opticalt:otxchange@ftp.itu.int/tsg15opticaltransport/COMMUNICATIONS/index.html
>
> Follow the links for the ccamp working group.
> Regards,
> Steve
>
> On 12/17/2004 11:22 AM, Adrian Farrel wrote:
> > Hi,
> >
> > Please note that these are the unofficial comments from SG15.
> > I was present when this was discussed in the Q14/15 meeting in Geneva
at
> > the end of November / start of December, but I have not seen the final
> > version of the material that they intended to liaise to us.
> >
> > Unfortunatley, the liaison response missed the deadline (set to allow
good
> > time after the Geneva meeting) and the WG last call (set to end after
the
> > liaison deadline). No matter; let's see what we can do with my notes
from
> > the meeting.
> >
> > Thanks,
> > Adrian
> > ===
> >
> > Section 3.1
> >
> > "The separation between the two processes and corresponding two name
> > spaces has the advantage that the discovery of the transport plane can
be
> > performed independent from that of the control plane (and vice-versa),
and
> > independent of the method used in each name space. This allows
assigning
> > link connections in the control plane without the link connection
being
> > physically connected."
> >
> > There were some questions about the term "independent". Does it imply
a
> > different mechanism or a different timing?
> > Also, what is meant by the last sentence? Do the transport resource
exist
> > or not when the control plane assignment is made?
> >
> > My understanding of this paragraph is that:
> > - It is material extracted from G.8080 so Q14/15 should be better
> >   placed to answer these questions than us.
> > - The "independence" is precisely that raised in the final question.
> >    That is, assignment in the management plane is independent of
> >    connectivity in the data plane. The two discovery processes
> >    are fully independent (time and mechanism).
> >
> > Perhaps you can find a way to clarify the text.
> >
> >
> >
> > Section 4.2
> >
> > "G.8080 refers to a component link as a variable adaptation function"
> >
> > It was pointed out that G.8080 does not use the term "component link".
> > Obviously what your text means is that the term "variable adaptation
> > function" used in G.8080 is broadly equivalent to the term "component
> > link" used in [LMP] and [BUNDLE]. Perhaps you can change the wording
so
> > that there is no misunderstanding possible.
> >
> >
> > Section 4.2 table
> >
> > CP---Interface
> > The meaning of the term "interface" was misunderstood in that it
appeared
> > to be applied in some non-IETF context, thus we are told that a CP is
like
> > a timeslot or wavelength not an interface. Further, the two columns
for
> > port and component link terminology should make this clear.
> > I don't believe we can go through the pain of writing out an
explanation
> > of every IETF term. This draft is intended to bring LMP transport
within
> > the view of the IETF, not the other way around.
> >
> >
> > General comments on TE links
> >
> > There was (still) some considerable unquiet about the precise nature
of a
> > TE link and how it maps to G.805/8080 concepts. There are a bunch of
> > specific questions about the definition of a TE link, and it is not
clear
> > whether this is the right document to contain the answers. I suggest
that
> > you have a go at answering the questions (we can liaise them back to
> > Q14/15 when we recieve the questions :-) and include them in the draft
if
> > you think it is appropriate.
> >
> > IMHO some of the questions are refusing to acknowledge the abstract
nature
> > of a TE link, and the fact that it is not material how it is
constructed
> > at a lower level because it simply exists at the higher level. In any
> > case, as I say above, this draft is intended to explain transport
concepts
> > so that the IETF can understand them, not the other way around.
> >
> > q1: Can a TE link use parallel resources from different transport
layers?
> > For example, could a TE link between LSR A and LSR B use a lambda and
a
> > timeslot from the same fiber? (Note that there is a claim that an SNPP
> > cannot do this because it exists only within a single layer.)
> >
> > q2: Can a TE link use component resources from parallel links. For
> > example, could a TE link be built from all of the red lambdas from a
> > collection of parallel fibers? Or could a TE link be built from
different
> > STS-1s from parallel OC-48s? (This is said to be true of SNPPs.)
> >
> > q3: Is it possible to build a TE link out of other TE links at
different
> > routing levels? This might (I suppose) involve bundling FAs to provide
> > another TE link. Or possibly we are talking about concatenating FAs to
> > provide a path that is presented as a TE link. (Again, the claim is
that
> > an SNPP link at one level can include SNPPs from a lower level).
> >
> >
> >
> >
> >
> >
>
>
>
>
>