[Teas] Relationship between TE topology and SAP topology

[Italo Busi <[e-mail]>]

Hi Oscar, TEAS WG,

During the TEAS WG session at IETF 121, Oscar offered to provide some text to clarify the relationship between the TE topology and the SAP topology

This is the current text in draft-ietf-teas-actn-poi-applicability-12:

   There are two possible models to report the access links between CEs
   and PEs: the TE Topology Model, defined in [RFC8795], or the Service
   Attachment Points (SAP) Model, defined in [RFC9408].

   Although the discovery of access links is outside the scope of this
   document, clarifying the relationship between these two models has
   been identified as a gap.

Considering that the scope of draft-ietf-teas-actn-poi-applicability is to identify gaps, the authors think that we can add the guidelines on using TE Topology and SAP Topology if the text proposal is available before the document is ready for WG LC. Otherwise, the document can be submitted to WG LC just highlighting the gap and without providing any guidance on how to address it.

It is worth noting that there is a similar issue in the TE topology profile draft and the gap can be addressed in that document.

These are some doubts I am having:

  1.  Are TE topology and the SAP topology intended to be used exclusively on different control interfaces? Or, can they co-exist on the same control interface?
  2.  It they can co-exist on the same interface, how it is possible to associate TE and SAP topological entities? For example, which LTP is associate with which SAP?
  3.  It they can co-exist on the same interface, are the they providing completely different and complimentary information or there is some overlapping of information?
  4.  It they can co-exist on the same interface and provides some overlapping information, how to reconcile any difference/inconsistency between the information reported by the two models?

Thanks, Italo