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

[Gyan Mishra <[e-mail]>]

Hi Adrian

Excellent job breaking this down and making it clear to all of us!!

The term partition is strong as I agree it implies underlay resources that
are not shared, however group sounds like a perfect.

Pool goes to far in the other direction as if all resources are shared.

Bundle I think is at about the same as far as right context in line with
group implying shared resources.

However I think from a nomenclature perspective I like group better.

Kind Regards

Gyan

On Wed, Aug 11, 2021 at 8:28 PM Kiran M <[e-mail]> wrote:

> Hi Adrian,
> Thank you for breaking it down clearly. It helped me see the delta due
> to use of term 'IETF network slice service’ instead of just slice.
>
> In this 4-tier architecture (for the sake of convenience), few things
> could be documented after clarification:
>
> 1) is it mandatory that operator must have an 'IETF Network slice
> instance' to realize an IETF network slice service?
>    - One of the things we discussed early on was that it should be
> possible to map a customer’s network slice request even when the
> operator does not have slice-infrastructure. This is why Southbound
> interface had lot of discussions on using existing data models. Should
> we  now redefine what a SBI would be? Is it between 2nd and 3rd tier?
> Should architecture allow 1st to 3rd? Since resource-partitioning is an
> important part of slices should we name the interface between 3rd to 4th
> tier?
>
> 2) in order to scale the slices, hierarchical slices were defined. The
> stitching could be done horizontally or vertically over the
> resource-partitions. are they still needed in this architecture.
>
> In my mind, what you call a resource partition is nothing but an
> abstraction of connected network resources (vaguely resembles the
> definition of slice, isn’t it?). What happens above that is an
> orchestration on different slice segments to produce the desired
> effects.
>
> So I think, with this architecture we would need to clean up/edit the
> text on 3 items in the document - SBI, optionality of 2nd tier (if you
> agree - related to your 4c/d/e), section on hierarchical structure.
>
> Thanks
> Kiran
>
> On 8/11/2021 12:37:49 PM, "Adrian Farrel" <[e-mail]> wrote:
>
> >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
> >>>   > 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
> >>>   > 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
> >>>   > >
> >>>   > > _______________________________________________
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> >>>   > > as
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> >>>   > > Et6yMaO-gk!Q0ycOf0ELxT6mG1GbnO4LSL-Q99J4uu7jfdUtBECaI-
> >>>   > > O08HqD31TGJciNjuxL2A$
> >>>   >
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> >>
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