Re: [Teas] New term for the underlay construct used for slice realization

[Vishnu Pavan Beeram <[e-mail]>]

** As a WG participant.. **

Adrian, Hi!

Thanks for your earlier emails in this thread that have helped drill down
the discussion to the specific item that needs a fresh term!
Please see inline (prefixed VPB).

-Pavan (as a WG participant)

On Thu, Aug 12, 2021 at 10:05 AM Adrian Farrel <[e-mail]> wrote:

> Thanks for your useful opinion, Tarek.
>
>
>
> I have no objection to the use of the word “aggregate”. It is generally
> used to express grouping together to treat as a single entity or to be
> treated in the same way.
>
>
>
> But I do like “foo aggregate” to mean that a number of foo have been
> aggregated.
>

[VPB] But, that isn’t necessarily how IETF has been using the term
“aggregate”.  “Behavior Aggregate” (as defined in IETF) doesn’t mean
aggregating behaviors. The same goes for “Treatment Aggregate”. Behavior
Aggregate (the way we read/interpret it) is an aggregate with a specific
behavior.

>
>
> So “slice aggregate” would be an aggregation of slices. Your use in I-D.draft-bestbar-teas-ns-packet
> is, therefore, confusing. If the slices are **not** separated out into
> different flows (or traffic streams) then, yes, you are aggregating slices.
> But if the slices are separated out, as you describe, then what you have is
> “IETF network slice traffic stream aggregation”.
>


[VPB] Yes. The definition of the slice aggregate (as defined in
draft-bestbar-teas-ns-packet) does state that the slice aggregate comprises
of one or more IETF network slice traffic streams.  We could have chosen a
longer descriptive name, but opted to keep it short.


>
>
> “Network resource aggregate” would imply that resources have been
> collected together to be used as a single entity.
>

[VPB] Not necessarily. "Network Resource Aggregate" isn't meant to imply
"aggregating network resources". The intent behind the proposal is to say
that it is an aggregate that has specific network resources.

You might do that, for example, with a set of parallel links that can be
> aggregated (or bundled) and treated as a single link.
>
>
>
> I don’t think we are aggregating resources in this case. We are grouping,
> profiling, partitioning, collecting, or even filtering.
>
>
>
> Adrian
>
>
>
> *From:* Tarek Saad <[e-mail]>
> *Sent:* 12 August 2021 15:41
> *To:* [e-mail]; 'Kiran Makhijani' <[e-mail]>;
> 'John E Drake' <jdrake=[e-mail]>; 'Dongjie (Jimmy)' <
> [e-mail]>; 'Lizhenbin' <[e-mail]>; [e-mail]
> *Subject:* Re: [Teas] New term for the underlay construct used for slice
> realization
>
>
>
> Hi Adrian/all,
>
>
>
> As described in I-D.ietf-teas-ietf-network-slice-definition, an IETF
> Network Slice service may include multiple connections that associate sets
> of endpoints - each having a set of SLOs/SLEs.
>
> In I-D.draft-bestbar-teas-ns-packet, we defined a Slice Aggregate as a
> construct that comprises of one or more IETF network slice traffic streams
> that share the same set of SLOs/SLEs.
>
> The Slice Aggregate construct allows aggregating streams from multiple
> IETF Network Slice connections that share common SLOs/SLEs so that the
> provider network can offer the same aggregate treatment to them. The Slice
> Aggregate resources are instantiated on specific network elements as
> dictated by the Slice Aggregate topology.
>
>
>
> Since the scope of I-D.draft-bestbar-teas-ns-packet was the realization of
> IETF Network Slice service in a provider network, we had constrained the
> aggregate construct to slices.
>
>
>
> We understand that the aggregate construct can be generalized to support
> other services. Let us offer another option to consider for representing
> the generic construct: “Network Resource Aggregate”. There are multiple
> IETF documents that use the term Aggregate whenever grouping multiple
> service classes (Behavior Aggregate, Treatment Aggregate, Traffic
> Aggregate, etc.) - refer to rfc5127 and rfc2474 for more examples.
>
>
>
> Regards,
>
> Tarek
>
>
>
>
>
> *From: *Teas <[e-mail]> on behalf of Adrian Farrel <
> [e-mail]>
> *Date: *Wednesday, August 11, 2021 at 3:38 PM
> *To: *'Kiran Makhijani' <[e-mail]>, 'John E Drake' <
> jdrake=[e-mail]>, 'Dongjie (Jimmy)' <
> [e-mail]>, 'Lizhenbin' <[e-mail]>, [e-mail] <
> [e-mail]>
> *Subject: *Re: [Teas] New term for the underlay construct used for slice
> realization
>
> I wonder whether we can pick this apart and put it back together in a way
> that makes sense.
>
> The customer's view of all this is an "IETF network slice service". I think
> (hope) we are all agreed on this. The customer may ask (in shorthand) for a
> "network slice", but:
> - they are talking about IETF technology, so they asking for an "IETF
> network slice"
> - they actually want behavioural characteristics and have no right to tell
> the operator
>   how to manage the network, so they are asking for an "IETF network slice
> service."
>
> The operator has a bigger set of things to worry about.
>
> 1. At the top of the operator's view is the "IETF network slice service" as
>     requested by the customer. We have this defined already, so nothing
> more
>     to say.
>
> 2. The operator maps the request for a slice service into the "IETF network
>     slice" which is the expression of the service in terms of network
> connectivity
>     in the context of the operator's network. The relationship here is like
> the
>     relationship between the L3SM and L3NM.
>
> 3. At the bottom of their view is an underlying network. The technology of
> this
>    network depends, of course, on the operator's offering, but this is the
> network
>    technology being sliced. It may be an IP network, and MPLS network, an
> OTN,
>    or whatever. I would call this the "Underlay Network." This network may,
> in
>    turn, be built upon an underlay network of the same or a different
> technology,
>    and it may be facilitated through network slicing - but this need not
> concern
>    us here.
>
> 4. That leaves the glue in the middle: the bit that enables the scaling and
> maps
>    the network slice to the network. And I think it is this bit that is
> causing the
>    most debate about terminology. There are some points to consider:
>
>    a. The term "network resources" applies to the bandwidth, queues,
> buffers,
>        etc. available on the links and nodes in the network. That may be
>        extended to refer to whole links and nodes.
>
>    b. The number of IETF network slice services is potentially large and
> the
>        operator needs a mechanism to scale the mapping of services to
>        network resources.
>
>    c. The IETF network slices may be grouped for identical treatment to
>        achieve scaling, where the grouping collects IETF network slices
> with
>        similar SLAs.
>
>    d. It may be that different traffic flows within a single IETF network
> slice
>         have different characteristics. In this case, it may be beneficial
> to group
>         together some of the traffic flows from different slices.
>
>    e. The grouped slices/flows are enabled in the network using network
>         resources assigned for that purpose. The assignment may be anything
>         from a fully-fledged virtual network (such as in ACTN or VPN+),
> through
>         network reserved resources (such as in MPLS-TE), and centrally
>         accounted resources (such as SDN or possible SR), to statistically
>         shared resources.
>
> There seems to be various points for and against 4d. But, it would appear
> that this is an implementation or deployment issue that doesn't change what
> the protocols need to do. So we should probably allow it architecturally,
> or
> at least, not disallow it.
>
> Of course, as Kiran points out, 4c/d/e may be a pass-through. That is, it
> is
> not necessary to implement such groupings either because there are only a
> few slices (which has been the view of some operators) or because the
> network systems can handle the number of slices. And it is in the nature of
> architectures of this sort that all functions can be nulled out without
> loss
> of generality, and we have to recall that the internals of provisioning
> systems may appear as functional blocks in our architectures, but we don't
> compel implementations to adhere to that type of architecture. So I don't
> think we have to worry on that account.
>
> And that brings the question of how we name the resources that are gathered
> in 4e.
>
> I can't decide whether it is helpful to spend time saying why I don't like
> each of the proposed terms. I certainly have things I don't like about (for
> example) "slice aggregate" (because of 4d, which means it is really a
> "slice
> sub-flow aggregate"), and I am not a fan of "VTN" (because of "transport"
> and maybe it is not really a network). But maybe it is better for me to say
> what I think we should call things? I think we have...
>
> -       IETF network slice service (customer view)
> -       IETF network slice (operator view)
> -       Resource partition (delivery mechanism)
> -       Underlay network (network used to support the slice)
>
> Why "resource partition"? Well it is a collection of "nodes, links, and
> network resources that are marked within the network for use by a set of
> network slice traffic flows".
> It is possible that the word "partition" is too strong because it may imply
> to some people that resources in a partition cannot be shared, but I don't
> feel that.
> Softer words than "partition" would be "group", "bundle", "pool", and I
> could live with any of them.
>
> Best,
> Adrian
>
>
> -----Original Message-----
> From: Teas <[e-mail]> On Behalf Of Kiran Makhijani
> Sent: 11 August 2021 16:00
> To: John E Drake <jdrake=[e-mail]>; Dongjie (Jimmy)
> <[e-mail]>; Lizhenbin <[e-mail]>; [e-mail]
> Subject: Re: [Teas] New term for the underlay construct used for slice
> realization
>
> Hi John, (and all),
>
> Two very basic clarification questions:
> 1. How do we differentiate between  the slice-segments that are
> resource-aware vs those that are not? I had assumed that since a slice
> has an SLO, it will need network resource allocations in some form.
>
> 2. Is it ok to assume that the customer view of slice is an 'IETF
> network slice service' and the 'IETF slice realization' of that service
> in a provider network is raises the question of underlay and overlay
> constructs. Am I right?
> (a) if so, then we are acknowledging  the presence of another layer of
> abstraction (for realization). It could be underlay/overlay or
> aggregate/??. Then the term 'slice aggregate' is better and my
> preference, it is easier to see that different slice-services are
> aggregated into a single construct  in a provider network. Use of
> underlay/overlay are confusing.
> (b) for a leaner provisioning, I would also prefer to see it documented
> that the aggregate is optional and it should be possible to directly map
> a slice-service to physical or real resources in the network.
> specifically useful when a single domain is carving out slices for
> different purposes.
>
> Thanks
> Kiran
>
>
> ------ Original Message ------
> From: "John E Drake" <jdrake=[e-mail]>
> To: "Dongjie (Jimmy)" <[e-mail]>; "Lizhenbin"
> <[e-mail]>; "[e-mail]" <[e-mail]>
> Sent: 8/11/2021 5:38:05 AM
> Subject: Re: [Teas] New term for the underlay construct used for slice
> realization
>
> >Jimmy,
> >
> >Snipped, comments inline.
> >
> >Yours Irrespectively,
> >
> >John
> >
> >
> >Juniper Business Use Only
> >
> >>  -----Original Message-----
> >>  From: Dongjie (Jimmy) <[e-mail]>
> >>  Sent: Tuesday, August 10, 2021 11:03 PM
> >>  To: John E Drake <[e-mail]>; Lizhenbin <[e-mail]
> >;
> >>[e-mail]
> >>  Subject: RE: New term for the underlay construct used for slice
> realization
> >>
> >>  [External Email. Be cautious of content]
> >>
> >underlay construct for network slice realization bound to
> >>  > > network slice services? That is, is the underlay construct only for
> >>  > > use in network slicing, or should it be generalized for more
> possible uses?
> >>  >
> >>  > [JD] Absolutely yes
> >>
> >>  [Jie] I guess you mean "Yes" to the latter case, which is "it should be
> generalized
> >>  for more possible uses", is my understanding correct?
> >
> >[JD]  Yes to the latter
> >
> >>
> >>  >
> >>  > >
> >>  > > 2.      If the answer to question 1 is YES, should it reflect the
> following
> >>  > > characteristics?
> >>  > >
> >>  > > a.      It is about the underlay
> >>  > > b.      It is about the partitioned resources used to deliver the
> network slice
> >>  > > services
> >>  > > c.      It allows the 1:1, N:1, and 1:N mapping models between the
> network
> >>  > slice
> >>  > > services and the underlay construct. The 1:1 and N:1 mapping may be
> >>  > > straightforward. Does it also make sense to divide the elements or
> >>  > > traffic flows in a single network slice service to carry them in
> >>  > > different
> >>  > underlay constructs?
> >>  >
> >>  > [JD]  Yes to all of the above.  Please see:
> >>  >
> https://urldefense.com/v3/__https://datatracker.ietf.org/doc/html/draf
> <https://urldefense.com/v3/__https:/datatracker.ietf.org/doc/html/draf>
> >>  > t-drake-bess-enhanced-vpn-06__;!!NEt6yMaO-
> >>  gk!TCiJHCZCwFgwpuFoujxVlZ4r9
> >>  > F6mLpE4nJ-9zpqkY-kls-ROxL4C2_xNaR2ImI4$
> >>  > >
> >>  > > Lastly, here are some candidates of the "new term":
> >>  > >
> >>  > > Option 1: The network slice service is called "overlay slice", then
> >>  > > the underlay construct is called "underlay slice".
> >>  > >
> >>  > > Option 2: The network slice service is called "service slice", then
> >>  > > the underlay construct is called "resource slice".
> >>  >
> >>  > [JD]  I don't think we need another term for what we are already
> >>  > calling an 'IETF Network Slice Service'.  Adrian and I are
> considering
> >>  > the term 'resource partition' to describe the partitioning of
> underlay
> >>  > network resources in support of various overlay services such as IETF
> Network
> >>  Slice Services.
> >>  > This is congruent with the ideas expressed in:
> >>  >
> https://urldefense.com/v3/__https://datatracker.ietf.org/doc/html/draf
> <https://urldefense.com/v3/__https:/datatracker.ietf.org/doc/html/draf>
> >>  > t-ietf-spring-resource-aware-segmen__;!!NEt6yMaO-
> >>  gk!TCiJHCZCwFgwpuFouj
> >>  > xVlZ4r9F6mLpE4nJ-9zpqkY-kls-ROxL4C2_xNxEfwaXg$
> >>  > ts-03.  What this allows one to build is an 'partitioned underlay
> >>  > network topology'.
> >>
> >>  [Jie] Agree that here we are talking about the term for the underlay
> construct.
> >>  "Resource partition" captures one of its key characteristics, while IMO
> another
> >>  thing the term needs to reflect is that the resource partition is
> needed
> on a
> >>  subset of the links and nodes (rather than on a single node or link) in
> the physical
> >>  network, which together builds a logical network topology.
> >
> >[JD]  In my initial email, above, I was proposing 'partitioned underlay
> network topology'
> >
> >>
> >>  Best regards,
> >>  Jie
> >>
> >>  >
> >>  > >
> >>  > > Your opinion about these candidates are much appreciated. You may
> >>  > > also propose other new term if it complies with the above two
> points.
> >>  >
> >>  > [JD]  I think you have exceeded your remit.
> >>  >
> >>  > >
> >>  > >
> >>  > >
> >>  > > Best Regards,
> >>  > > Robin
> >>  > >
> >>  > > _______________________________________________
> >>  > > Teas mailing list
> >>  > > [e-mail]
> >>  > >
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> <https://urldefense.com/v3/__https:/www.ietf.org/mailman/listinfo/te>
> >>  > > as
> >>  > > __;!!N
> >>  > > Et6yMaO-gk!Q0ycOf0ELxT6mG1GbnO4LSL-Q99J4uu7jfdUtBECaI-
> >>  > > O08HqD31TGJciNjuxL2A$
> >>  >
> >>  > _______________________________________________
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> >>  > __;!!NEt6yMaO-gk!TCiJHCZCwFgwpuFoujxVlZ4r9F6mLpE4nJ-9zpqkY-kls-
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> >
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