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

From: "Adrian Farrel" <[email-masked]>
Date: Fri, 17 Dec 2004 18:22:41 -0000

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).

---

From: Stephen J Trowbridge <[email-masked]>
Date: Fri, 17 Dec 2004 11:53:15 -0700

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:[email-masked]/tsg15opticaltransport/COMMUNICATIONS/index.html

Follow the links for the ccamp working group.
Regards,
Steve

---

From: "Adrian Farrel" <[email-masked]>
Date: Fri, 17 Dec 2004 19:48:12 -0000

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" <[email-masked]>
To: "Adrian Farrel" <[email-masked]>
Cc: <[email-masked]>; "Don Fedyk" <[email-masked]>;
<[email-masked]>; "Brungard, Deborah A, ALABS"
<[email-masked]>; "Jonathan Lang" <[email-masked]>; "Dimitri
Papadimitriou" <[email-masked]>
Sent: Friday, December 17, 2004 6:53 PM
Subject: Re: ITU-T SG15 comments on draft-ietf-ccamp-transport-lmp-00.txt