OMS Protection: document refinement

[dieterbeller]

The I-D needs to be refined based on Editor's note in 2.10.2.1. and 2.10.2.2:

   [Editor's note: text and a figure based on the slide deck attached to
   Open Issue #119 on GitHub showing more details regarding the LTPs of
   the primary and secondary TE-link will be added here.]

Reference: https://github.com/ietf-ccamp-wg/draft-ietf-ccamp-optical-impairment-topology-yang/files/10267404/optical.protection.switching-25.pptx

[dieterbeller]

New figure for section 2.10.2.1. - text still to be added:

            WDM-TE-Node-1                         WDM-TE-Node-2
       +-----------------------+           +-----------------------+
       |     ROADM             |           |Selector     ROADM     |
       |   +-------+   +-------+LTP2   LTP4+-------+   +-------+   |
       |   |       |   |    ---o<--------->o---    |   |       |   |
   LTP1|   |    RP1|   |   /   |  prim.    |   \   |   |RP2    |   |LPT6
   <-->o---o.......o---o--o    |           |    o--o---o.......o---o<-->
       |   |       |   |   \   |  second.  |   /   |   |       |   |
       |   |       |   |    ---o<--------->o---    |   |       |   |
       |   +-------+   +-------+LTP3   LTP5+-------+   +-------+   |
       |                       |           |                       |
       +-----------------------+           +-----------------------+

        ROADM port |  1+1 protected OMS MCG (TE-link)  | ROADM port
               RP1 o<--------------------------------->o RP2
                   |  between ROADM ports RP1 and RP2  |

                underlying primary and secondary TE-links:
                          LTP2 o<--------->o LTP4
                          LTP3 o<--------->o LTP5

           connectivity matrix provides optical impairments in
           both directions between LTPs in the two WDM-TE-Nodes:
           * LTP1 and LTP2,                    * LTP6 and LTP4,
           * LTP1 and LTP3                     * LTP6 and LTP5

     Figure 19: Modeling view of Protected TE-link with underlying TE-
                                   links

[egriseri]

Hi @dieterbeller, there's a minor typo in the figure: LPT6 should be LTP6. Figure is crystal clear.

[dieterbeller]

Updated figure for section 2.10.2.1. - text still to be added:

            WDM-TE-Node-1                         WDM-TE-Node-2
       +-----------------------+           +-----------------------+
       |     ROADM     Splitter|           |Selector     ROADM     |
       |   +-------+   +-------+LTP2   LTP4+-------+   +-------+   |
       |   |       |   |    ---o<--------->o---    |   |       |   |
   LTP1|   |    RP1|   |   /   |  prim.    |   \   |   |RP2    |   |LTP6
   <-->o---o.......o---o--o    |           |    o--o---o.......o---o<-->
       |   |       |   |   \   |  second.  |   /   |   |       |   |
       |   |       |   |    ---o<--------->o---    |   |       |   |
       |   +-------+   +-------+LTP3   LTP5+-------+   +-------+   |
       |               Selector|           |Splitter               |
       +-----------------------+           +-----------------------+

        ROADM port |  1+1 protected OMS MCG (TE-link)  | ROADM port
               RP1 o<--------------------------------->o RP2
                   |  between ROADM ports RP1 and RP2  |

                underlying primary and secondary TE-links:
                          LTP2 o<--------->o LTP4
                          LTP3 o<--------->o LTP5

           connectivity matrix provides optical impairments in
           both directions between LTPs in the two WDM-TE-Nodes:
           * LTP1 and LTP2,                    * LTP6 and LTP4,
           * LTP1 and LTP3                     * LTP6 and LTP5

     Figure 19: Modeling view of 1+1 Protected TE-link with underlying
                                  TE-links

New figures for section 2.10.2.2. - text still to be added:

            WDM-TE-Node-1                         WDM-TE-Node-2
       +-----------------------+           +-----------------------+
       |     ROADM     Splitter|           |Selector     ROADM     |
       |   +-------+   +.......+...........+-------+   +-------+   |
       |   |       |   .    ---o<--------->o---    .   |       |   |
   LTP1|   |   LTP2|   .   /   |           |   \   .   |LTP3   |   |LTP4
   <-->o---o.......o---o--o    |           |    o--o---o.......o---o<-->
       |   |       |   .   \   |           |   /   .   |       |   |
       |   |       |   .    ---o<--------->o---    .   |       |   |
       |   +-------+   +...................+.......+   +-------+   |
       |               Selector|           |Splitter               |
       +-----------------------+           +-----------------------+

        ROADM port |  Splitter/Selector abstracted in  | ROADM port
              LTP2 o<--------------------------------->o LTP3
                   |  1+1 protected OMS MCG (TE-link)  |

           connectivity matrix provides optical impairments in
           both directions between LTPs in the two WDM-TE-Nodes:
           * LTP1 and LTP2                     * LTP3 and LTP4

           Optical impairments of splitter/selector modeled as
           optical impairments of the 1+1 protected TE-link

       Figure 20: Modeling view of Abstracted 1+1 Protected TE-link -
                        ROADM ports modeled as LTPs

            WDM-TE-Node-1                         WDM-TE-Node-2
       +-----------------------+           +-----------------------+
       |     ROADM     Splitter|           |Selector     ROADM     |
       |   +-------+   +-------+...........+-------+   +-------+   |
       |   |       |   |    ---o<--------->o---    |   |       |   |
   LTP1|   |       |   |   /   |LTP2   LTP3|   \   |   |       |   |LTP4
   <-->o---o.......o---o--o    |           |    o--o---o.......o---o<-->
       |   |       |   |   \   |LTP2   LTP3|   /   |   |       |   |
       |   |       |   |    ---o<--------->o---    |   |       |   |
       |   +-------+   +-------+...........+-------+   +-------+   |
       |               Selector|           |Splitter               |
       +-----------------------+           +-----------------------+

                               |           |
                          LTP2 o<--------->o LTP3
                               |           |
                               1+1 protected
                               OMS MCG (TE-link)

           connectivity matrix provides optical impairments in
           both directions between LTPs in the two WDM-TE-Nodes:
           * LTP1 and LTP2                     * LTP3 and LTP4

           Optical impairments of Splitter/Selector are included in
           the optical impairments provided by the connectivity matrix

       Figure 21: Modeling view of Abstracted 1+1 Protected TE-link -
        physical ports abstracted into single LTP on both link ends

[dieterbeller]

Updated figures based on comments from @sergiobelotti :

            WDM-TE-Node-1                         WDM-TE-Node-2
       +-----------------------+           +-----------------------+
       |     ROADM     Splitter|           |Selector     ROADM     |
       |   +-------+   +-------+LTP2   LTP4+-------+   +-------+   |
       |   |       |   |    ---o<--------->o---    |   |       |   |
   LTP1|   |    RP1|   |   /   |  prim.    |   \   |   |RP2    |   |LTP6
   <-->o---o.......o---o--o    |           |    o--o---o.......o---o<-->
       |   |       |   |   \   |  second.  |   /   |   |       |   |
       |   |       |   |    ---o<--------->o---    |   |       |   |
       |   +-------+   +-------+LTP3   LTP5+-------+   +-------+   |
       |               Selector|           |Splitter               |
       +-----------------------+           +-----------------------+

                 --+                                   +--
        ROADM port |                                   | ROADM port
               RP1 o<--------------------------------->o RP2
                   |                                   |
                 --+                                   +--
                      1+1 protected OMS MCG (TE-link)
                      between ROADM ports RP1 and RP2

                underlying primary and secondary TE-links:

                             --+           +--
                               |  prim.    |
                          LTP2 o<--------->o LTP4
                          LTP3 o<--------->o LTP5
                               |  second.  |
                             --+           +--

           connectivity matrix provides optical impairments in
           both directions between LTPs in the two WDM-TE-Nodes:
           * LTP1 and LTP2,                     * LTP6 and LTP4,
           * LTP1 and LTP3                      * LTP6 and LTP5

     Figure 19: Modeling view of 1+1 protected TE-link with underlying
                       primary and secondary TE-link

            WDM-TE-Node-1                         WDM-TE-Node-2
       +-----------------------+           +-----------------------+
       |     ROADM     Splitter|           |Selector     ROADM     |
       |   +-------+   +.......+...........+-------+   +-------+   |
       |   |       |   .    ---o<--------->o---    .   |       |   |
   LTP1|   |   LTP2|   .   /   |           |   \   .   |LTP3   |   |LTP4
   <-->o---o.......o---o--o    |           |    o--o---o.......o---o<-->
       |   |       |   .   \   |           |   /   .   |       |   |
       |   |       |   .    ---o<--------->o---    .   |       |   |
       |   +-------+   +...................+.......+   +-------+   |
       |               Selector|           |Splitter               |
       +-----------------------+           +-----------------------+

                 --+                                   +--
        ROADM port |                                   | ROADM port
              LTP2 o<--------------------------------->o LTP3
                   |                                   |
                 --+                                   +---
                     Splitter/Selector abstracted into
                     1+1 protected OMS MCG (TE-link)

           connectivity matrix provides optical impairments in
           both directions between LTPs in the two WDM-TE-Nodes:
           * LTP1 and LTP2                      * LTP3 and LTP4

       Figure 20: Modeling view of abstracted 1+1 protected TE-link -
                        ROADM ports modeled as LTPs

            WDM-TE-Node-1                         WDM-TE-Node-2
       +-----------------------+           +-----------------------+
       |     ROADM     Splitter|           |Selector     ROADM     |
       |   +-------+   +-------+...........+-------+   +-------+   |
       |   |       |   |    ---o<--------->o---    |   |       |   |
   LTP1|   |       |   |   /   |LTP2   LTP3|   \   |   |       |   |LTP4
   <-->o---o.......o---o--o    |           |    o--o---o.......o---o<-->
       |   |       |   |   \   |LTP2   LTP3|   /   |   |       |   |
       |   |       |   |    ---o<--------->o---    |   |       |   |
       |   +-------+   +-------+...........+-------+   +-------+   |
       |               Selector|           |Splitter               |
       +-----------------------+           +-----------------------+

                             --+           +--
                               |           |
                          LTP2 o<--------->o LTP3
                               |           |
                             --+           +--
                               1+1 protected
                               OMS MCG (TE-link)

           connectivity matrix provides optical impairments in
           both directions between LTPs in the two WDM-TE-Nodes:
           * LTP1 and LTP2                      * LTP3 and LTP4

       Figure 21: Modeling view of abstracted 1+1 protected TE-link -
        physical ports abstracted into single LTP on both link ends

[dieterbeller]

Updated sections 2.10.2.1. and 2.10.2.2:

2.10.2.1.  OMS MCG Protection Modeled as Protected TE-link with
           underlying TE-links

   [Editor's note: this sub-section is still work in progress]

   This modeling approach models the 1+1 protected TE-link as an
   additional TE-link entity on top of the primary and secondary TE-link
   between the two adjacent WDM-TE-Nodes terminating the 1+1 OMS MCG
   protection group formed by these two TE-links and the splitter and
   selector functions in the two nodes.  This 1+1 protected TE-link is
   associated with underlying primary and secondary TE-links forming the
   1+1 protection group.  The following "te-link-attributes" already
   defined in [RFC8795] and [RFC8776] can be used for modeling the 1+1
   protected TE-link ("te-link-attributes" augmentation copied from
   [RFC8795]:

     augment /nw:networks/nw:network/nt:link:
     +--rw te!
        +--rw te-link-attributes
        |  ....................
        |  +--rw underlay {te-topology-hierarchy}?
        |  |  +--rw enabled?                     boolean
        |  |  +--rw primary-path
        |  |  |  +--rw network-ref?    leafref
        |  |  |     ....................
        |  |  +--rw backup-path* [index]
        |  |  |  +--rw index           uint32
        |  |  |  +--rw network-ref?    leafref
        |  |  |     ....................
        |  |  +--rw protection-type?             identityref

   These attributes are used as follows:

   *  "underlay": the presence of this container is indicating that an
      underlying protection scheme exists
   *  "enabled": (boolean) is set to 'true'
   *  "primary-path": is referencing the primary OMS MCG (TE-link)
   *  "backup-path": is referencing the secondary OMS MCG (TE-link)
   *  "link-protection-type" (identityref) set to 'link-protection-1-
      plus-1' as defined in [RFC8776]

   The optical impairments for the underlying primary and secondary TE-
   link can be described as for unprotected TE-links.  It may also be
   possible to only describe the optical impairments for the 1+1
   protected TE-link.  In this case the optical impairments of the worse
   of the two underlying TE-links shall be used.  This should be
   sufficient as input for path computation (worst case optical
   feasibility consideration).

            WDM-TE-Node-1                         WDM-TE-Node-2
       +-----------------------+           +-----------------------+
       |     ROADM     Splitter|           |Selector     ROADM     |
       |   +-------+   +-------+LTP2   LTP4+-------+   +-------+   |
       |   |       |   |    ---o<--------->o---    |   |       |   |
   LTP1|   |    RP1|   |   /   |  prim.    |   \   |   |RP2    |   |LTP6
   <-->o---o.......o---o--o    |           |    o--o---o.......o---o<-->
       |   |       |   |   \   |  second.  |   /   |   |       |   |
       |   |       |   |    ---o<--------->o---    |   |       |   |
       |   +-------+   +-------+LTP3   LTP5+-------+   +-------+   |
       |               Selector|           |Splitter               |
       +-----------------------+           +-----------------------+

                 --+                                   +--
        ROADM port |                                   | ROADM port
               RP1 o<--------------------------------->o RP2
                   |                                   |
                 --+                                   +--
                      1+1 protected OMS MCG (TE-link)
                      between ROADM ports RP1 and RP2

                underlying primary and secondary TE-links:

                             --+           +--
                               |  prim.    |
                          LTP2 o<--------->o LTP4
                          LTP3 o<--------->o LTP5
                               |  second.  |
                             --+           +--

           connectivity matrix provides optical impairments in
           both directions between LTPs in the two WDM-TE-Nodes:
           * LTP1 and LTP2,                     * LTP6 and LTP4,
           * LTP1 and LTP3                      * LTP6 and LTP5

     Figure 19: Modeling view of 1+1 protected TE-link with underlying
                       primary and secondary TE-link

   Figure 19 illustrates this modeling approach including the LTPs in
   WDM-TE-Node-1 and WDM-TE-Node-2, respectively.  In addition to the
   physical view, the following three TE-links are shown:

   *  The 1+1 protected TE-link

   *  The underlying primary TE-link
   *  The underlying secondary TE-link

   The optical impairments of the splitter (outgoing direction) and the
   selector (incoming direction) are included in the optical impairments
   described by the connectivity matrix and the local link connectivity
   list for the TE node.  For the example shown in Figure 19, the
   connectivity matrix describes the optical impairments between LPT1
   and LTP2 as well as LTP1 and LTP3 for WDM-TE-Node-1.  Likewise, the
   connectivity matrix describes the optical impairments between LPT4
   and LTP6 as well as LTP5 and LTP6 in WDM-TE-Node-2.

2.10.2.2.  OMS MCG Protection Modeled as Single Protected TE-link

   [Editor's note: this sub-section is still work in progress]

   This modeling approach abstracts the two physical OMS links carrying
   the same OMS MCG together with the splitter and selector functions in
   the two WDM-TE-Nodes forming the OMS protection group into a single
   TE-link.  If this modeling approach is used the "te-link-attributes"
   already defined in [RFC8795] and [RFC8776] are used as follows:

   *  "underlay": this container must not be present
   *  "link-protection-type" (identityref) set to 'link-protection-1-
      plus-1' as defined in [RFC8776]

   The optical impairments exposed for this 1+1 protected TE-link are
   typically based on the optical impairments of the worse of the two
   underlying physical OMS links including the optical impairments
   imposed by the splitter (outgoing direction) and selector (incoming
   direction).

   Figure 20 illustrates this modeling approach where the splitter/
   selector in the adjacent WDM-TE-Nodes, WDM-TE-Node-1 and WDM-TE-Node-
   2, as well as the two physical OMS MCG links are abstracted into a
   single 1+1 protected TE-link.  This is illustrated by the the dotted
   line surrounding these four physical entities in Figure 20.  Based on
   this modeling approach, the ROADM port connected to the splitter/
   selector function is modeled as LTP for the 1+1 protected TE-link
   (LTP2 in WDM-TE-Node-1 and LTP3 in WDM-TE-Node-2).  In this example,
   the connectivity matrix describes the optical impairments between
   LPT1 and LTP2 in WDM-TE-Node-1.  Likewise, the connectivity matrix
   describes the optical impairments between LPT3 and LTP4 in WDM-TE-
   Node-2.

            WDM-TE-Node-1                         WDM-TE-Node-2
       +-----------------------+           +-----------------------+
       |     ROADM     Splitter|           |Selector     ROADM     |
       |   +-------+   +.......+...........+-------+   +-------+   |
       |   |       |   .    ---o<--------->o---    .   |       |   |
   LTP1|   |   LTP2|   .   /   |           |   \   .   |LTP3   |   |LTP4
   <-->o---o.......o---o--o    |           |    o--o---o.......o---o<-->
       |   |       |   .   \   |           |   /   .   |       |   |
       |   |       |   .    ---o<--------->o---    .   |       |   |
       |   +-------+   +...................+.......+   +-------+   |
       |               Selector|           |Splitter               |
       +-----------------------+           +-----------------------+

                 --+                                   +--
        ROADM port |                                   | ROADM port
              LTP2 o<--------------------------------->o LTP3
                   |                                   |
                 --+                                   +---
                     Splitter/Selector abstracted into
                     1+1 protected OMS MCG (TE-link)

           connectivity matrix provides optical impairments in
           both directions between LTPs in the two WDM-TE-Nodes:
           * LTP1 and LTP2                      * LTP3 and LTP4

       Figure 20: Modeling view of abstracted 1+1 protected TE-link -
                        ROADM ports modeled as LTPs

   Alternatively, the optical impairments imposed by the splitter and
   selector in each of the two adjacent WDM-TE-Nodes can also be
   included in the optical impairments described by the connectivity
   matrix of the two nodes instead of taking them into account as
   optical impairments of the 1+1 protected TE-link.  This is
   illustrated in Figure 21 below.  In this case, the two physical ports
   on both ends of the 1+1 protected TE-link are abstracted into a
   single LTP, LTP2 and LTP3, respectively.

            WDM-TE-Node-1                         WDM-TE-Node-2
       +-----------------------+           +-----------------------+
       |     ROADM     Splitter|           |Selector     ROADM     |
       |   +-------+   +-------+...........+-------+   +-------+   |
       |   |       |   |    ---o<--------->o---    |   |       |   |
   LTP1|   |       |   |   /   |LTP2   LTP3|   \   |   |       |   |LTP4
   <-->o---o.......o---o--o    |           |    o--o---o.......o---o<-->
       |   |       |   |   \   |LTP2   LTP3|   /   |   |       |   |
       |   |       |   |    ---o<--------->o---    |   |       |   |
       |   +-------+   +-------+...........+-------+   +-------+   |
       |               Selector|           |Splitter               |
       +-----------------------+           +-----------------------+

                             --+           +--
                               |           |
                          LTP2 o<--------->o LTP3
                               |           |
                             --+           +--
                               1+1 protected
                               OMS MCG (TE-link)

           connectivity matrix provides optical impairments in
           both directions between LTPs in the two WDM-TE-Nodes:
           * LTP1 and LTP2                      * LTP3 and LTP4

       Figure 21: Modeling view of abstracted 1+1 protected TE-link -
        physical ports abstracted into single LTP on both link ends

[sergiobelotti]

weekly call 2023-06-20 There is comment by Gert and Roberto about the figure and the fact the picture should provide two links for bidirectional. The final decision is to add the text that to simplify the ascii figure a single bidirectional link is represented. (suggested by Gabriele)

[dieterbeller]

Here is a new Note right above Figure 11 addressing the comment above:

   Note: Where several WDM nodes are involved, the links between WDM
   nodes in the figures below illustrating the various protection
   architectures are drawn as bi-directional links (arrows on both ends
   of the dashed line) for the sake of simplification.  Physically, all
   links in WDM networks are uni-directional and there is a fiber link
   in forward and a fiber link in reverse direction.  WDM services are
   typically bi-directional and the same media channel is used on the
   links in both directions.  The splitter function of the combined
   splitter/selector is always located on the upstream side whereas the
   selector function is always located on the downstream side in the two
   directions.

                           end-to-end MC path1
        |<------------------------------------------------------>|

   +-----------+                                          +-----------+
   | WDM Node1 |           +-----+      +-----+           | WDM Node2 |
   |      +----|           | WDM |      | WDM |           |----+      |
   |      |   -o<--------->o-----o<---->o-----o<--------->o-   |      |
   |  OT  |  / |           |Node3|      |Node4|           | \  |  OT  |
   | +--+ | /  |           +-----+      +-----+           |  \ | +--+ |
  -o-o  o-o-   |                                          |   -o-o  o-o-
   | +--+ | \  |     +-----+     +------+     +-----+     |  / | +--+ |
   |      |  \ |     | WDM |     | WDM  |     | WDM |     | /  |      |
   |      |   -o<--->o-----o<--->o------o<--->o-----o<--->o-   |      |
   |      +----|     |Node5|     | Node6|     |Node7|     |----+      |
   |           |     +-----+     +------+     +-----+     |           |
   +-----------+                                          +-----------+

        |<------------------------------------------------------>|
                           end-to-end MC path2

      Figure 11: Individual OTSi Protection without 3R regenerators

[dieterbeller]

This issue has been resolved with PR https://github.com/ietf-ccamp-wg/draft-ietf-ccamp-optical-impairment-topology-yang/pull/138.