Subject: Re: [CCAMP] I-D Action: draft-lee-ccamp-wson-impairment-yang-00.txt

From: Dieter Beller <[email-masked]>
Date: Thu, 27 Sep 2018 11:07:21 +0200

Hi Young and Haomian,

I had a look at draft-lee-ccamp-wson-impairment-yang-00, which you
submitted a few weeks ago and I have the following concerns:

The abstract and introduction states:

Abstract

This document provides a YANG data model for the impairment-aware TE
topology in wavelength switched optical networks (WSONs).

1. Introduction

...

This document provides a YANG data model for the impairment-aware
Traffic Engineering (TE) topology in wavelength switched optical
networks (WSONs). The YANG model described in this document is a
WSON technology-specific Yang model based on the information model
developed in [RFC7446] and the two encoding documents [RFC7581] and
[RFC7579] that developed protocol independent encodings based on
[RFC7446].

Based on this scope, I was expecting that this I-D provides
te-link augmentations for WSON networks.

Examples of WSON specific te-link attributes are fiber type,
spectrum availability, chromatic dispersion, PMD, PDL, OSNR
contribution (if the link includes ILAs) just to list a few.

However, the only te-link augmentation is:

augment /nw:networks/nw:network/nt:link/tet:te/tet:te-link-attributes:
+--ro power? int32

It is also reasonable to define WSON augmentations for termination
points representing the line side of optical transponders as they
can be considered as topological elements

even if these attributes are not representing optical
impairments!:

augment /nw:networks/nw:network/nw:node/tet:te/tet:tunnel-termination-point:
+--ro available-modulation* identityref
+--ro modulation-enabled? boolean
+--ro modulation-type? identityref
+--ro available-FEC* identityref
+--ro FEC-enabled? boolean
+--ro FEC-type? identityref
+--ro FEC-code-rate? decimal64
+--ro FEC-threshold? decimal64

I don't understand why all the OT attributes are defined as ro
attributes. State of the art OTs typically provide multiple
operational modes. Hence, these attributes should

be defined as rw attributes.

All other augmentations are defined for paths (te-tunnels) or
termination points, which is a bit strange! Here are two examples:

augment /nw:networks/nw:network/nt:link/tet:te/tet:te-link-
attributes/tet:underlay/tet:primary-path/tet:path-
element/tet:type/tet:label/tet:label-hop/tet:te-label/tet:technology:
+--:(wson-imp-topo)
+--rw (grid-type)?
| +--:(dwdm)
| | +--ro channel-freq? decimal64
| +--:(cwdm)
| +--ro channel-wavelength? uint32
+--ro bit-rate? decimal64
+--ro BER? decimal64
+--ro pmd? decimal64
+--ro cd? decimal64
+--ro osnr? decimal64
+--ro q-factor? decimal64

channel-freq/channel-wavelength, bit-rate, BER are definitively
service (te-tunnel) attributes and do not represent optical
impairments for a WSON network topology.

For pmd, cd, and q-factor (definition?), it looks like these are
attributes for all the links along the path. Why are these
impairments defined for a path and are not te-link

augmentations?

I was expecting that this draft defines optical impairments for
the topological entities in a WSON network where optical
impairments matter. Could you please clarify.

Thanks,

Dieter

On 01.09.2018 05:42, [email-masked]
wrote:

A New Internet-Draft is available from the on-line Internet-Drafts directories.

Title : A Yang Data Model for Impairment-Aware WSON Optical Networks
Authors : Young Lee
Haomian Zheng
Filename : draft-lee-ccamp-wson-impairment-yang-00.txt
Pages : 18
Date : 2018-08-31

Abstract:
This document provides a YANG data model for the impairment-aware TE
topology in wavelength switched optical networks (WSONs).

The IETF datatracker status page for this draft is:
https://datatracker.ietf.org/doc/draft-lee-ccamp-wson-impairment-yang/

There are also htmlized versions available at:
https://tools.ietf.org/html/draft-lee-ccamp-wson-impairment-yang-00
https://datatracker.ietf.org/doc/html/draft-lee-ccamp-wson-impairment-yang-00

Please note that it may take a couple of minutes from the time of submission
until the htmlized version and diff are available at tools.ietf.org.

Internet-Drafts are also available by anonymous FTP at:
ftp://ftp.ietf.org/internet-drafts/

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