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2023-05-23 TAPI Meeting notes

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Preliminary agenda:

• Progresses in gNMI streaming and delta streaming
• Continue the Path Computation UCs analysis
• Continue the discussion of adding OMS CEP spec to version 2.1.3
• Model of the internal connectivity matrix of a ROADM

Nigel Davis informs about progresses in the gNMI structure of PM data (both UML and YANG) and related Protobuf encoding data.

• Next week will present some skeletons and pictures.

Regarding delta streaming, Nigel Davis recalls the challenge of mandatory properties which cannot be omitted even if not changed.

• Andrea Mazzini what about the tree depth? If a parent level attribute changes, shall the whole subtree be streamed?
• Answer is the same, if all the elements of the subtree are optional (in the UML/YANG), it is possible to condition them (e.g. in the RIA) according to the specific case, e.g.:
  • GET operation: in the reply always include all available parameters.
  • Streaming: in the stream include only the changed attributes.
  • Nigel Davis adds the consideration that a list shall be always streamed as a whole, in case one or more elements are added/removed/modified.

Andrea Mazzini shows slides 179-204 from updated otcc2022.AM.001_TAPI_RIASlides.pptx

• Use cases presented:
  • Path Computation Service Provisioning (slides 179-185, 184 added after the meeting)
  • Connectivity Service Provisioning – Configuration with Paths as constraints (slides 186-187)
  • Path Computation Service Provisioning based on existing Connection Routes (slides 188-190)
  • Path Computation Service Provisioning adopting orphan Paths (slides 191-195)
• Then brief overview of some samples from the reference IETF specifications - as previously indicated by Dominique Verchere (slides 198-204):
  • CCAMP:
    • YANG Data Models for requesting Path Computation in Optical Networks
    • A YANG Data Model for requesting Path Computation in an Optical Transport Network (OTN)
    • Framework and Data Model for OTN Network Slicing
    • OTN Tunnel YANG Model
  • TEAS:
    • A YANG Data Model for requesting path computation
    • Common YANG Data Types for Traffic Engineering RFC 8776
    • A Framework for IETF Network Slices
    • A YANG Data Model for the IETF Network Slice Service

  • Encoding of Objective Functions in the Path Computation Element Communication Protocol (PCEP) RFC 5541

Discussion items:

• Jonathan Sadler mentions the result/state of Path Computation Service, e.g. optical metrics (available in calculated Paths).
  • Input: bounding
  • Output: actual values
• Nigel Davis underlines that the Path object is currently modeled as a list of Links, hence there is no place e.g. for Node impairments.
• Esther, the Path Computation Service constraints are essentially related to the topology and the 3R capability.
• Gabriele Galimberti the including/excluding of 3R are constraints for optical feasibility, but by design, i.e. following the network planning previously performed.
  • Other optical parameters can be optionally specified as Path Computation Service constraints.
  • In general we need to be flexible, including full range of possible topological and optical constraints driving the computation.
• Esther considers that the same model could be used for both planning and provisioning.
  • Ramon Casellas we already have the example of externalized Path computation (GNPy), anyway it would be recommendable to have same model for same entities but involved in different management steps.
  • Consider both Compute Path and Validate Path features.
• Then long discussion on which are the essential differences between TAPI Connectivity Service and TAPI Path Computation Service.
  • Path is not reserving resources.
  • Could Path Computation Service constraints be exactly the same as Connectivity Service constraints?
  • Ramon Casellas Path shall include its partition, i.e. timeslot(s), wavelength(s).
    • A Path as a list of Links (OMS Sections) and wavelength slots valid for a given application

The conclusion is to continue exploring the real need of Path Computation Service and Path as distinct entities with respect to Connectivity Service and Connection-Route.

• Investigate which enhancements to Connectivity Service may satisfy Path computation Use Cases.