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

Vishnu Pavan Beeram <vishnupavan@gmail.com> Tue, 17 August 2021 18:51 UTC

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From: Vishnu Pavan Beeram <vishnupavan@gmail.com>
Date: Tue, 17 Aug 2021 13:51:28 -0500
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To: Adrian Farrel <adrian@olddog.co.uk>
Cc: TEAS WG <teas@ietf.org>
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Subject: Re: [Teas] New term for the underlay construct used for slice realization
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Thanks for the humble clarification! :)


I understand that you don't want to put a name to the "collection of slice
flows" that are mapped to (and use) a specific network resource partition
(or group or pool).

But I do want to ensure that the scope of the network resource partition is
clearly articulated. I interpreted your response as there being a
one-to-one mapping between the "network resource partition" and the
"collection of slice flows" using it.

Thanks,
-Pavan (WG participant)

On Tue, Aug 17, 2021 at 11:57 AM Adrian Farrel <adrian@olddog.co.uk> wrote:

> Hi Pavan,
>
>
>
> > ** As a WG participant.. **
>
>
>
> ** As a humble servant of the WG and pen-holder for the document **
>
>
>
> > Adrian, Hi!
>
> >
>
> >> 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".
>
> >
>
> > In the definition above, Is “resource partition” a collection of “items”
> that are
>
> > marked within the network for “exclusive” use by a set of network slice
> traffic
>
> > flows (slice aggregate)? Or can multiple slice aggregates use the same
> resource
>
> > partition?
>
>
>
> I see that you have determined to introduce a separation between the
> concept you call a “slice aggregate” and the resources used by that thing.
>
>
>
> I, on the other hand, had considered that the “resource partition” is the
> set of resources available for / used by the collection of slice flows, and
> that there is no need to introduce a separate construct. That is, in one
> hand you have a set of slices each comprised of one or more traffic flows,
> and in the other hand you have a network. You map one to the other by
> associating slice flows with the resources they can use.
>
>
>
> There could be a debate about “resource sharing”. That is, when resources
> in one partition are not being used, can they be “borrowed” by another
> partition? I suppose the answer is yes, but I wonder how both slices can
> guarantee the service SLAs if the resources they use are not guaranteed to
> be available. This is considerably different from borrowing resources for
> best effort traffic, which can happen in any resource reservation scheme.
>
>
>
> Regards,
>
> Adrian (as a humble WG participant and pen-holder for the document)
>
>
>
> > Regards,
>
> > -Pavan (as a WG participant)
>
>
>
>
>
>
>
> On Wed, Aug 11, 2021 at 2:38 PM Adrian Farrel <adrian@olddog.co.uk> 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 <teas-bounces@ietf.org> On Behalf Of Kiran Makhijani
> Sent: 11 August 2021 16:00
> To: John E Drake <jdrake=40juniper.net@dmarc.ietf.org>rg>; Dongjie (Jimmy)
> <jie.dong@huawei.com>om>; Lizhenbin <lizhenbin@huawei.com>om>; teas@ietf.org
> 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=40juniper.net@dmarc.ietf.org>
> To: "Dongjie (Jimmy)" <jie.dong@huawei.com>om>; "Lizhenbin"
> <lizhenbin@huawei.com>om>; "teas@ietf.org" <teas@ietf.org>
> 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) <jie.dong@huawei.com>
> >>  Sent: Tuesday, August 10, 2021 11:03 PM
> >>  To: John E Drake <jdrake@juniper.net>et>; Lizhenbin <lizhenbin@huawei.com
> >;
> >>teas@ietf.org
> >>  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
> >>  > > Teas@ietf.org
> >>  > >
> https://urldefense.com/v3/__https://www.ietf.org/mailman/listinfo/te
> <https://urldefense.com/v3/__https:/www.ietf.org/mailman/listinfo/te>
> >>  > > as
> >>  > > __;!!N
> >>  > > Et6yMaO-gk!Q0ycOf0ELxT6mG1GbnO4LSL-Q99J4uu7jfdUtBECaI-
> >>  > > O08HqD31TGJciNjuxL2A$
> >>  >
> >>  > _______________________________________________
> >>  > Teas mailing list
> >>  > Teas@ietf.org
> >>  >
> https://urldefense.com/v3/__https://www.ietf.org/mailman/listinfo/teas
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> >>  > __;!!NEt6yMaO-gk!TCiJHCZCwFgwpuFoujxVlZ4r9F6mLpE4nJ-9zpqkY-kls-
> >>  ROxL4C2
> >>  > _xNDCrPaNQ$
> >
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