Re: [Teas] I-D Action: draft-nsdt-teas-transport-slice-definition-03.txt

[Eric Gray <[e-mail]>]

Hi Kiran.

Your proposed text misses a few important points.

	On the topic of “SBI"
1) As mentioned multiple times, “SBI” is a logical concept that may or may not exist in any instance of TSC interactions.
2) As such, it is incorrect to assert that the TSC “will send the request via its SBI …”
3) In fact, a more accurate (and less restrictive) wording would be along the lines of “When a TSC receives a request via its NBI, it needs to map the NBI-provided information in the request to one or more transport slice realization instances, using - for example - some form of SBI.”

	On the topic of whether or not we need to include “TSRE"
4) TSRE is a concept that - as discussed so far - is not visible to the Transport Slice consumer.
5) As I have so far understood the concept, TSE and TSRE are not interchangeable (were they actually interchangeable, we should only define and use one of these terms) - hence it is not clear how it is even possible to refer to a TSE as a TSRE, let alone imagine why it would be “necessary.”

Note that - if the distinction between TSE and TSRE arises from the possibility that transport slice service termination points may exist either on consumer nodes, or on provider nodes - then this is something that would likely be visible to the slice consumer.  But - if that is the case - that has not been clear in ongoing discussions and is not AFAIK explicitly stated in the draft.

—
Eric



> On Aug 12, 2020, at 12:01 PM, Kiran Makhijani <[e-mail]> wrote:
> 
> Eric:
> In my mind, the scope at least for definitions is to identify components that help describe the transport slices concept and hopefully normalize the terms in context. It helps someone reading this document for the first time. I agree that NBI and upper layers will not see this mapping. On the other hand, framework and SBI when extended may use it.
> We could balance clarity vs concerns raised by augmenting the text as below. What do you think?
>  
>    TSEs will get mapped to the endpoints that are allocated and
>    assigned by the network controller during the realization of a
>    transport slice and are technology-specific, i.e. they depend on the
>    network technology used during the transport slice realization.  They
>    are identified by a node and some associated data. They may be referred to as
>    TSREs when necessary. A non-exhaustive
>    list of nodes containing TSREs are routers, switches, PON nodes,
>    Wireless nodes and Optical devices.
>   
>    When TSC receives a request via its NBI to create a transport slice between
>    multiple TSEs, it will send the request via its SBI to realize the transport slice. 
>    The TSRE will be notified by network controller during TS realization to enable
>    mapping between TSREs and the TSEs.
>  
>  
> Thanks
> Kiran
>  
> From: Teas <[e-mail]> On Behalf Of Eric Gray
> Sent: Wednesday, August 12, 2020 6:46 AM
> To: Rokui, Reza (Nokia - CA/Ottawa) <[e-mail]>
> Cc: Joel Halpern Direct <[e-mail]>; [e-mail]
> Subject: Re: [Teas] I-D Action: draft-nsdt-teas-transport-slice-definition-03.txt
>  
> Reza,
>  
>              On the topic of continued inclusion of TSRE.
>  
>              You are inappropriately assuming that we will _ever_ be undertaking standards work that details the much of the internals of the transport slice controller.
>  
>              I did not object to including some text on the topic of a South-Bound Interface (SBI) - even though this is also out of scope in our work (being again a part of the logical model for interactions between the TSC and “stuff” underlying it) - because of the argument that it is useful to think of an SBI in order to allow examples to be made for using various technology specific service models.
>  
>              This is legitimate, because the use of such examples suggests some similar work on technology-specific service models that might be useful for support some possible TSC implementations.
>  
>              But Joel makes a very good point in saying that TSRE is out of scope in this draft.  Also, Joel earlier made the point that including out-of-scope concepts strictly intended for use in future work is misguided.
>  
>              For our purposes, it would be more useful to limit ourselves to a simpler set of definitions that do not include additional and out-of-scope confusing concepts.
>  
>              Finally, your stance on whether or not to remove this concept should be based on TEAS working group consensus to continue to include it - rather than your personal inclinations to do so.  This draft was - after all - suggested for adoption by the working group, and subsequent changes will therefore be under the change control of the TEAS WG.
>  
>  
> 
> 
> On Aug 10, 2020, at 7:59 AM, Rokui, Reza (Nokia - CA/Ottawa) <[e-mail] <mailto:[e-mail]>> wrote:
>  
> Joel
> Please see inline.
>  
> Cheers,
> Reza
>  
> On 2020-08-06, 11:17 AM, "Joel Halpern Direct" <[e-mail] <mailto:[e-mail]>> wrote:
>  
>     Thank you for commenting the the TSRE question.
>     Let me reprase my question, given the comments...
>  
>     Given that TSRE is strictly technology and infrastructure specific, why
>     is it defined in this document?  Whether we need it or not it seems to
>     be outside the scope of this document.
> [Reza] Since the transport slice definition draft addresses various aspects of the transport slice such transport slice realization were introduced and a result the TRSE was mentioned briefly to allow later drafts to discuss it in details.
> Same is for example for “Transport Slice Controller (TSC)”. This document introduced the TSC concept and again later draft can give more details.
>  
>  
>     Yours,
>     Joel
>  
>     On 8/6/2020 11:12 AM, Rokui, Reza (Nokia - CA/Ottawa) wrote:
>     > Thanks Joel for your comments.
>     > 
>     > Please see inline for TSRE.
>     > 
>     > Reza
>     > 
>     > On 2020-07-12, 11:59 PM, "Teas on behalf of Joel Halpern"
>     > <[e-mail] <mailto:[e-mail]> on behalf of [e-mail] <mailto:[e-mail]>> wrote:
>     > 
>     >      My thanks to the design team for the update to this document.  It is
>     > 
>     >      much improved.
>     > 
>     >      I a  unable to understand the third paragraph of section 4.1.2.  I do
>     > 
>     >      not know what maximum occupancy refers to.  It seems to be talking
>     > about
>     > 
>     >      some kind of notion of objectives applying to subsets of traffic
>     > within
>     > 
>     >      a slice.  But I can't tell.
>     > 
>     >      Appendix A.1 is labeled as discussion, and as such appears to be
>     > trying
>     > 
>     >      to be informative rather than normative.  However, the last
>     > paragraph of
>     > 
>     >      introduces things a customer may ask for (i.e. SLOs) that are not
>     > 
>     >      described in the rest of the document, and do not actually seem to
>     > me to
>     > 
>     >      be appropriate.  I wowuld ask that the last paragraph of section
>     > A.1 be
>     > 
>     >      stricken.
>     > 
>     >      Some minor comments:
>     > 
>     >      At one point the SLA is defined (I believe reasonably)as the contract
>     > 
>     >      5that describes the SLOs with the consequences for missing them.  Then
>     > 
>     >      in section 4.1 it says "all SLOs combine to form the SLA".  Believe
>     > you
>     > 
>     >      mean "form the objective portion of the SLA"  or "contribute to the
>     > SLA"
>     > 
>     >      or something, since the contractual and consequence aspects of the SLA
>     > 
>     >      are outside of the SLOs?
>     > 
>     >      Given that availability is defined in terms of the other SLOs (quite
>     > 
>     >      reasonable) and that some of those may not be directly measurable), it
>     > 
>     >      seems that availability should itself be considered indirectly
>     > measurable?
>     > 
>     >      nit - Given that the earlier text says that this is only an initial
>     > 
>     >      list, there is no need to include a bullet in the aspects that says
>     > 
>     >      "Other objectives could be specified".  It is true.  But has already
>     > 
>     >      been stated above.
>     > 
>     >      In section 4.2 on transport service endpoints, the text seems to say
>     > 
>     >      that an endpoint has a specific kind of connectivity (P2P, P2MP, ....).
>     > 
>     >      It seems perfectly valid for a single TSE to be using both P2P and
>     > P2MP
>     > 
>     >      communication.  It seems rather odd to have to consider it to be two
>     > 
>     >      TSEs.  From later text, it is the slice, not the endpoint, which as a
>     > 
>     >      particular connectivity type.
>     > 
>     >      I wonder if the "Transport Slice Realization endpoint" is useful? 
>     > Given
>     > 
>     >      that many things are in both the sample TSE list and the sample TSRE
>     > 
>     >      list, it is going to be hard to tell them apart.  And as far as I can
>     > 
>     >      tell, the TSRE is internal to the transport, and therefore outside the
>     > 
>     >      scope of this document?  The differentiation in the diagram that
>     > follows
>     > 
>     >      the description does not seem to line up with the description, and
>     > 
>     >      leaves me more confused.
>     > 
>     > [Reza]
>     > 
>     > As mentioned in draft, Transport slice realization endpoints (TSRE) are
>     > allocated and
>     > 
>     > assigned by the network controller during the realization of a
>     >   transport slice and are technology-specific, i.e. they depend on the
>     > 
>     > network technology used during the transport slice realization.
>     > 
>     > Depends on the definition of the transport slice, Transport Slice
>     > endpoints (TSE) and TSRE might be very similar but their object models
>     > are different.
>     > 
>     > Please also see the following draft which addresses the modeling of the
>     > transport slice realization:
>     > 
>     >   * draft-liu-teas-transport-network-slice-yang-01
>     > 
>     > In summary, TRSE are assigned during the transport slice realization and
>     > will be communicated from TSC NBI to higher system “Transport slice
>     > Customer” and identifies how a transport slice is realized in the network.
>     > 
>     > We will add more clarification to the draft.
>     > 
>     >      Yours,
>     > 
>     >      Joel
>     > 
>     >      On 7/12/2020 10:49 PM, [e-mail] <mailto:[e-mail]> wrote:
>     > 
>     >      >
>     > 
>     >      > A New Internet-Draft is available from the on-line
>     > Internet-Drafts directories.
>     > 
>     >      >
>     > 
>     >      >
>     > 
>     >      >          Title           : IETF Definition of Transport Slice
>     > 
>     >      >          Authors         : Reza Rokui
>     > 
>     >      >                            Shunsuke Homma
>     > 
>     >      >                            Kiran Makhijani
>     > 
>     >      >                            Luis M. Contreras
>     > 
>     >      >                            Jeff Tantsura
>     > 
>     >      >         Filename        :
>     > draft-nsdt-teas-transport-slice-definition-03.txt
>     > 
>     >      >         Pages           : 21
>     > 
>     >      >         Date            : 2020-07-12
>     > 
>     >      >
>     > 
>     >      > Abstract:
>     > 
>     >      >     This document describes the definition of a slice in the
>     > transport
>     > 
>     >      >     networks and its characteristics.  The purpose here is to bring
>     > 
>     >      >     clarity and a common understanding of the transport slice
>     > concept and
>     > 
>     >      >     describe related terms and their meaning.  It explains how
>     > transport
>     > 
>     >      >     slices can be used in combination with end to end network
>     > slices, or
>     > 
>     >      >     independently.
>     > 
>     >      >
>     > 
>     >      >
>     > 
>     >      > The IETF datatracker status page for this draft is:
>     > 
>     >      > 
>     > https://datatracker.ietf.org/doc/draft-nsdt-teas-transport-slice-definition/ <https://nam11.safelinks.protection.outlook.com/?url=https%3A%2F%2Fdatatracker.ietf.org%2Fdoc%2Fdraft-nsdt-teas-transport-slice-definition%2F&data=02%7C01%7Ckiranm%40futurewei.com%7Cc540b0786b4147a7db5d08d83ec61e0c%7C0fee8ff2a3b240189c753a1d5591fedc%7C1%7C1%7C637328367948000379&sdata=bICHb3oQ2hIAdRRf8CNOZymu7vasTHEbdzVxJaZJfiA%3D&reserved=0>
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>     >      >
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