RE: Small issue on draft-ietf-ccamp-gmpls-sdh-00.txt

["Mannie, Eric" <Eric.Mannie@ebone.com>]

Dear All,

Sorry I was confused, the original text of the draft is correct:

With any kind of ***contiguous*** concatenation there is one big signal, so
one and only one label (pointer) is needed (otherwise it is not a contiguous
concatenation). With any kind of virtual concatenation, there are several
VC's, so one label (pointer) per VC is needed. Even if all the VC's
virtually concatenated are contiguous (by coincidence) we still need to
identify each of them.

Arbitrary and standard concatenations are orthogonal with contiguous and
virtual concatenations.

Arbitrary means anything that is not standard.

We use a code to differentiate between standard and arbitrary contiguous
concatenation to avoid that a downstream node returns a timeslot at a
position not supported by the upstream node. The upstream node indicates the
number and types of signals to be concatenated and the downstream node
cannot change it (it can just accept or refuse).

We don't need a code to differentiate between standard versus arbitrary
virtual concatenation because there is no restriction anyway on the timeslot
positions that can return the downstream node. Again, the upstream node
indicates the number and types of signals to be concatenated and the
downstream node cannot change that (it can just accept or refuse). SDH 1996
restricts the virtual concatenation to some well defined signals, while SDH
2000 allows everything that make sense. But for the previous reasons we
don't need to differentiate between the two (thing about the reason why you
put a signaling element in a signaling message).

Agreed ?

Kind regards,

Eric

-----Original Message-----
From: Bernstein, Greg [mailto:GregB@ciena.com]
Sent: Wednesday, May 16, 2001 5:33 PM
To: ccamp@ops.ietf.org; mpls@UU.NET
Subject: Small issue on draft-ietf-ccamp-gmpls-sdh-00.txt


Hi in the draft draft-ietf-ccamp-gmpls-sdh-00.txt it says:

   In case of any type of contiguous concatenation (e.g. standard or
   arbitrary concatenation), only one label appears in the Label
   field. That label is the lowest signal of the contiguously
   concatenated signal. By lowest signal we mean the one having the
   lowest label when compared as integer values, i.e. the first
   component signal of the concatenated signal encountered when
   descending the tree.

   In case of virtual concatenation, the explicit ordered list of all
   labels in the concatenation is given. Each label indicates a
   component of the virtually concatenated signal.

This does not reflect the intent of arbitrary concatenation- arbitrary, size
and placement of timeslots.  Otherwise the main benefit of arbitrary
concatenation, preventing re-grooming is lost.  Corrected text could read:

    In the case of standard contiguous, only one label appears in the Label
   field. That label is the lowest signal of the standard contiguously
   concatenated signal. By lowest signal we mean the one having the
   lowest label when compared as integer values, i.e. the first
   component signal of the concatenated signal encountered when
   descending the tree.

   In the cases of arbitrary or virtual concatenation, the explicit ordered
list of all
   labels in the concatenation is given. Each label indicates a
   component of the arbitrary or virtually concatenated signal.


Greg B.
	Dr. Greg M. Bernstein, Senior Scientist, Ciena 
	New phone: (510) 573-2237