Re: [Teas] What SLOs and SLEs should be in the Slicing Service Model?

[Gyan Mishra <[e-mail]>]

Hi Med & Joel

I reread section 4.1 of the slice draft and to me it seems that SLO is from
provider POV measurable indicators and SLE is the is unmeasurable
expectations which is makes up the customer fulfillment of obligations by
the provider which would be like taking the tangible measurement
characteristics from the SLO and translation into legal obligation
fulfillment verbiage that goes into the service agreement.  So as the SLE
is not tangible but just a translation of SLO metrics into legal verbiage
my thoughts are that the framework as well as Yang model need only focus on
the SLO tangible metrics and leave the intangible for the lawyers writing
the customer agreement.


4.1 <https://datatracker.ietf.org/doc/html/draft-ietf-teas-ietf-network-slices-09#section-4.1>.
Objectives for IETF Network Slices

   An IETF Network Slice service is defined in terms of quantifiable
   characteristics known as Service Level Objectives (SLOs) and
   unquantifiable characteristics known as Service Level Expectations
   (SLEs).  SLOs are expressed in terms Service Level Indicators (SLIs),
   and together with the SLEs form the contractual agreement between
   service customer and service provider known as a Service Level
   Agreement (SLA).

   The terms are defined as follows:

   *  A Service Level Indicator (SLI) is a quantifiable measure of an
      aspect of the performance of a network.  For example, it may be a
      measure of throughput in bits per second, or it may be a measure
      of latency in milliseconds.

   *  A Service Level Objective (SLO) is a target value or range for the
      measurements returned by observation of an SLI.  For example, an
      SLO may be expressed as "SLI <= target", or "lower bound <= SLI <=
      upper bound".  A customer can determine whether the provider is
      meeting the SLOs by performing measurements on the traffic.

   *  A Service Level Expectation (SLE) is an expression of an
      unmeasurable service-related request that a customer of an IETF
      Network Slice makes of the provider.  An SLE is distinct from an
      SLO because the customer may have little or no way of determining
      whether the SLE is being met, but they still contract with the
      provider for a service that meets the expectation.



On Thu, Mar 24, 2022 at 10:36 AM <[e-mail]> wrote:

> Re-,
>
> They shouldn't!
>
> This is why I'm suggesting to not have that tagging frozen in the model.
> We can simply have a provision for a set of parameters. These parameters
> will be included to characterize the service with a service assurance
> component that will call out the identity of the subset of parameters that
> will be used as committed ones. That component will also include other data
> to ensure the same based used for assessment, etc.
>
> Cheers,
> Med
>
> > -----Message d'origine-----
> > De : Joel M. Halpern <[e-mail]>
> > Envoyé : jeudi 24 mars 2022 15:29
> > À : BOUCADAIR Mohamed INNOV/NET <[e-mail]>
> > Cc : 'TEAS WG' <[e-mail]>; [e-mail]
> > Objet : Re: [Teas] What SLOs and SLEs should be in the Slicing Service
> > Model?
> >
> > If the others are best effort, why would they be included in the SLO?
> > (We do not assume that every IETF network slice service will specify all
> > possible parameters.)
> >
> > Yours,
> > Joel
> >
> > On 3/24/2022 10:20 AM, [e-mail] wrote:
> > > Re-,
> > >
> > > Some services may be sensitive to delay for example but the slice
> service
> > request may include (for whatever reason) not only the delay, but also
> > other attributes that are currently listed as SLOs in the draft. The
> > provider is requested to only commit on the delay and best effort for the
> > other attributes.
> > >
> > > Cheers,
> > > Med
> > >
> > >> -----Message d'origine-----
> > >> De : Joel M. Halpern <[e-mail]> Envoyé : jeudi 24 mars
> > >> 2022 15:07 À : BOUCADAIR Mohamed INNOV/NET
> > >> <[e-mail]> Cc : 'TEAS WG' <[e-mail]>;
> > >> [e-mail] Objet : Re: [Teas] What SLOs and SLEs should be
> > >> in the Slicing Service Model?
> > >>
> > >> Interesting.  If they are indeed not coupled, then you are clearly
> > >> correct about representation.
> > >>
> > >> Can you give an example so I can understand when they would not be
> > coupled.
> > >> I had leapt to the (quite possibly incorrect) conclusion that the two
> > >> sets of properties went together.
> > >>
> > >> Thank you,
> > >> Joel
> > >>
> > >> On 3/24/2022 10:03 AM, [e-mail] wrote:
> > >>> Hi Joel,
> > >>>
> > >>> It is.
> > >>>
> > >>> As mentioned below, this should be covered as part of service
> > >> assurance/fulfillment/reporting parameters. Which parameters to put
> > >> there is deployment-specific. Not all parameters tagged as SLO in the
> > >> framework will end up as part of the assurance/fulfillment/reporting.
> > >>>
> > >>> Cheers,
> > >>> Med
> > >>>
> > >>>> -----Message d'origine-----
> > >>>> De : Joel M. Halpern <[e-mail]> Envoyé : jeudi 24 mars
> > >>>> 2022 14:52 À : BOUCADAIR Mohamed INNOV/NET
> > >>>> <[e-mail]>; [e-mail]; 'TEAS WG'
> > >>>> <[e-mail]> Objet : Re: [Teas] What SLOs and SLEs should be in
> > >>>> the Slicing Service Model?
> > >>>>
> > >>>> Isn't it important to distinguish between "these are things I
> > >>>> expect you to do, measure, and report" and "these are things I
> > >>>> would like you to do even though they are not measurable or
> > reportable"?
> > >>>>
> > >>>> Yours,
> > >>>> Joel
> > >>>>
> > >>>> On 3/23/2022 10:08 AM, [e-mail] wrote:
> > >>>>> Hi all,
> > >>>>>
> > >>>>> This message actually triggers a companion comment I have on the
> > >>>>> SLO/SLE
> > >>>> taxonomy. From the service modeling standpoint, I suggest that we
> > >>>> don't inherit that taxonomy for various reasons:
> > >>>>>
> > >>>>> * Things would be much simpler if we just focus on service
> > >>>>> requirements
> > >>>> without making an assumption how such requirement is expressed and
> > >>>> whether it is quantified/quantitative/qualitative/measurable/etc.
> > >>>> Whether/how a specific service requirement is covered by service
> > >>>> assurance/fulfillment can be part of the slice service definition
> > >> itself.
> > >>>>>
> > >>>>> * What we may tag as an SLE today because of the technology
> > >>>>> limitations,
> > >>>> may not stay as such forever. It may be true that an "expectation"
> > >>>> may not be easily assessed using current techniques (and thus be
> > >>>> tagged as SLE), but this does not prevent that innovative means
> > >>>> would be defined in the future (which means that it is an SLO, not
> > >>>> an SLE
> > >> anymore).
> > >>>>>
> > >>>>> * We are artificially adding extra complexity for the modelling
> > >>>>> part as
> > >>>> service requirement will need to be classified based as SLO or SLEs.
> > >>>>>
> > >>>>> * I remember that Kiran agreed at least to not import that
> > >>>>> taxonomy into
> > >>>> the data model when we were discussing the call for adoption of the
> > >>>> slice
> > >>>> definition:
> > >>>>>
> > >>>>> ==(the full message from Kiran can be found in the archives)===
> > >>>>> "However, it should not imply that NBI models are required to have
> > >>>> SLE/SLO indicators and I totally agreed with your comments on
> > >>>> draft-wd- teas-ietf-network-slice-nbi-yang-03"
> > >>>>> ==
> > >>>>>
> > >>>>> Cheers,
> > >>>>> Med
> > >>>>>
> > >>>>>> -----Message d'origine-----
> > >>>>>> De : Teas <[e-mail]> De la part de Adrian Farrel
> > >>>>>> Envoyé
> > >>>>>> : mercredi 23 mars 2022 14:47 À : 'TEAS WG' <[e-mail]>
> Objet :
> > >>>>>> [Teas] What SLOs and SLEs should be in the Slicing Service Model?
> > >>>>>>
> > >>>>>> Hi,
> > >>>>>>
> > >>>>>> Sorry for my audio being a mess in TEAS today.
> > >>>>>>
> > >>>>>> I believe I heard the discussion between Kireeti and Reza
> > >>>>>> correctly, and there was some follow-up in the chat.
> > >>>>>>
> > >>>>>> I agree that "Protection" is a realisation feature and so it
> > >>>>>> qualifies as an SLE, if at all.
> > >>>>>> But "Reliability" is clearly an SLO. Usually expressed as maximum
> > >>>>>> down- time per unit of time, or maximum lost traffic.
> > >>>>>>
> > >>>>>> There was one thing that I *think* I heard. This was Reza saying
> > >>>>>> that the service YANG model was only including the SLOs and SLEs
> > >>>>>> noted in the framework. Maybe I misheard "only" because I think
> > >>>>>> that might be a mistake.
> > >>>>>> The YANG model should certainly be interested in what the
> > >>>>>> framework says, but it is not a requirement that all SLOs and
> > >>>>>> SLEs in the framework be in the model if the authors find that
> > >>>>>> there is no interest in implementing them, and there should
> > >>>>>> certainly be no limitation about including additional SLOs or SLEs
> > in the YANG model.
> > >>>>>> Indeed, the SLOs and SLEs listed in the framework are presented
> > >>>>>> as
> > >>>> examples.
> > >>>>>>
> > >>>>>> Cheers,
> > >>>>>> Adrian
> > >>>>>>
> > >>>>>> _______________________________________________
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> > >>>>>> https://www.ietf.org/mailman/listinfo/teas
> > >>>>>
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>
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