Re: [Teas] Two more examples for draft-ietf-teas-ietf-network-slices

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Hi Adrian,

Thanks.

The centralized approach used in A.6 (particularly in Figure 13) is one way to stitch slices. That approach is suitable when the underlying domains belong to the same administrative entity or when the "coordinator" can assure the overall slice (e.g., identify intermediate root causes, react to localized deterioration signals, etc.). In cases where distinct entities are involved, the bilateral mode would be more convenient because it offers a clear responsibility scope for each involved domain and also offers means to intermediate domains to react to upstream failures/deterioration symptoms in order to satisfy the slice objectives (e.g., make use of multihoming). The bilateral mode is similar to what is depicted in https://datatracker.ietf.org/doc/html/rfc5160#section-4.1. 

In a bilateral mode, the slice services that will lead to the stitched slices would be between these service attachment points: 
* SDP1-SDP2 (ctrl of nw1)
* SDPX-SDP2 (ctrl of nw2)
* SDPU-SDP2 (ctrl of nw3)
* SDPS-SDP2 (ctrl of nw4)

The flow of the service requests would be as follows: 
             
(ctrl of nw1)==>(ctrl of nw2)==>(ctrl of nw3)==>(ctrl of nw4)
  | Device        | Device        | Device        | Device
  | Config        | Config        | Config        | Config
  v               v               v               v

Cheers,
Med

> -----Message d'origine-----
> De : Teas <[e-mail]> De la part de Adrian Farrel
> Envoyé : dimanche 31 juillet 2022 10:10
> À : [e-mail]
> Objet : [Teas] Two more examples for draft-ietf-teas-ietf-network-
> slices
> 
> Hi,
> 
> During the meeting at IETF-114, Lou suggested that we might make
> some efforts to include a discussion of hierarchical and
> concatenated IETF Network Slices within the framework draft.
> 
> We already have some text that notes that these approaches fall
> within the architecture, so probably nothing new needed there. But
> the Appendix provides a place to give simple examples of various
> deployment options (without getting into the details of
> realisation).
> 
> So, here is some proposed text.
> 
> Let me know if it causes any of you a problem.
> 
> Cheers,
> Adrian
> 
> ====
> 
> A.5.  Hierarchical Composition of Network Slices
> 
>    As mentioned in Section 4.3, IETF Network Slices may be
> arranged
>    hierarchically.  There is nothing special of novel about such
> an
>    arrangement, and it models the hierarchical arrangement of
> services
>    of virtual networks in many other environments.
> 
>    As shown in Figure 9, an Operator's Controller (NSC) that is
>    requested to provide an IETF Network Slice for a customer may,
> in
>    turn, request an IETF Network Slice from another carrier.  The
>    Operator's NSC may manage and control the underlay IETF Network
> Slice
>    by modifying the requested connectivity constructs and changing
> the
>    SLAs.  The customer is entirely unaware of the hierarchy of
> slices,
>    and the underlay carrier is entirely unaware of how its slice
> is
>    being used.
> 
>    This "stacking" of IETF Network Slice constructs is no
> different to
>    the way virtual networks may be arranged.
> 
>                --------------
>               | Network      |
>               | Slice        |
>               | Orchestrator |
>                --------------
>                 | IETF Network Slice
>                 | Service Request
>                 |                    Customer view
>             ....|................................
>                -v----------------    Operator view
>               |Controller        |
>               |  ------------    |
>               | | IETF       |   |
>               | | Network    |---|---
>               | | Slice      |   |   |
>               | | Controller |   |   |
>               | | (NSC)      |   |   |
>               |  ------------    |   |
>                ------------------    |
>                                      | IETF Network Slice
>                                      | Service Request
>                                      |
>             .........................|.....................
>                            ----------v-------    Carrier view
>                           |Controller        |
>                           |  ------------    |
>                           | | IETF       |   |
>                           | | Network    |   |--> Virtual Network
>                           | | Slice      |   |
>                           | | Controller |   |
>                           | | (NSC)      |   |
>                           |  ------------    |
>                       ....|  | Network       |............
>                           |  | Configuration |   Underlay Network
>                           |  v               |
>                           |  ------------    |
>                           | | Network    |   |
>                           | | Controller |   |
>                           | | (NC)       |   |
>                           |  ------------    |
>                            ------------------
>                             | Device Configuration
>                             v
> 
>      Figure 9: Example Hierarchical Arrangement of IETF Network
> Slices
> 
>    In this case, the network hierarchy may also be provided to
> bridge
>    connectivity between networks as shown in Figure 10.  Here, the
> an
>    IETF Network Slice may be requested of the lower layer network
> to
>    provide the desired connectivity constructs to supplement the
>    connectivity in the higher layer network where this
> connectivity may
>    be presented as a virtual link.
> 
>                   CE1                                       CE2
>                    |                                         |
>                    |                                         |
>                   _|_________________________________________|_
>                  ( :                                         : )
>                 (  :..............             ..............:  )
>                  (_______________:_____________:_______________)
>                                __|_____________|__
>                               (  :             :  )
>                              (   :.............:   )
>                               (___________________)
> 
>         Figure 10: Example Hierarchical Arrangement of IETF
> Network
>                        Slices to Bridge Connectivity
> 
> A.6.  Horizontal Composition of Network Slices
> 
>    It may be that end-to-end connectivity is achieved using a set
> of
>    cooperating networks as described in Section 4.3.  For example,
> there
>    may be multiple inter-connected networks that provide the
> required
>    connectivity as shown in Figure 11.  The networks may utilize
>    different technologies and may be under separate administrative
>    control.
> 
>                   CE1                                       CE2
>                    |                                         |
>                   SDP1                                      SDP2
>                    |                                         |
>                   _|____       ______       ______       ____|_
>                  (      )     (      )     (      )     (      )
>                 (        )---(        )---(        )---(        )
>                  (______)     (______)     (______)     (______)
> 
>         Figure 11: Example Customer View of Inter-connected
> Networks
>                       Provide End-to-End Connectivity
> 
>    In this scenario, the customer (represented by CE1 and CE2) may
>    request an IETF Network Slice service connecting the CEs.  The
>    customer considers the SDPs at the edge (shown as SDP1 and SDP2
> in
>    Figure 11) and might not be aware of how the end-to-end
> connectivity
>    is composed.
> 
>    However, because the various networks may be of different
>    technologies and under separate administrative control, the
> networks
>    are sliced individually and coordination is necessary to
> deliver the
>    desired connectivity.  The network to network interfaces (NNIs)
> are
>    present as SDPs for the IETF Network Slices in each network so
> that
>    each network is individually sliced.  In the example in Figure
> 11,
>    this is illustrated as network 1 (N/w1) being sliced between
> SDP1 and
>    SDPX, N/w2 being sliced between SDPY and SDPU, etc.  The
> coordination
>    activity involves binding the SDPs, and hence the connectivity
>    constructs, to achieve end-to-end connectivity.  In this way,
> simple
>    and complex end-to-end connectivity can be achieved with a
> variety of
>    connectivity constructs in the IETF Network Slices of different
>    networks "stitched" together.
> 
>               CE1
> CE2
>                |
> |
>               SDP1
> SDP2
>                |
> |
>               _|____          ______          ______
> ____|_
>              (      ) SDPX   (      ) SDPU   (      ) SDPS   (
> )
>             (  N/w1  )------(  N/w2  )------(  N/w3  )------(
> N/w4  )
>              (______)   SDPY (______)   SDPV (______)   SDPT
> (______)
> 
> 
>       Figure 12: Example Delivery of An End-to-End IETF Network
> Slice
>                        with Inter- connected Networks
> 
>    The controller/coordinator relationship is shown in Figure 13.
> 
>           --------------
>          | Network      |
>          | Slice        |
>          | Orchestrator |
>           --------------
>            | IETF Network Slice
>            | Service Request
>            |                    Customer view
>        ....|................................
>           -v----------------    Coordinator view
>          |Coordinator       |
>          |                  |
>           ------------------
>            |             |_________________
>            |                               |
>            |                               |
>        ....|.......................    ....|.....................
>           -v--------------                -v--------------
>          |Controller1     | Operator1    |Controller2     |
> Operator2
>          |  ------------  |              |  ------------  |
>          | | IETF       | |              | | IETF       | |
>          | | Network    | |              | | Network    | |
>          | | Slice      | |              | | Slice      | |
>          | | Controller | |              | | Controller | |
>          | | (NSC)      | |              | | (NSC)      | |
>          |  ------------  |              |  ------------  |
>      ....|  | Network     |............  |  | Network
> |............
>          |  | Config      | Underlay1    |  | Config      |
> Underlay2
>          |  v             |              |  v             |
>          |  ------------  |              |  ------------  |
>          | | Network    | |              | | Network    | |
>          | | Controller | |              | | Controller | |
>          | | (NC)       | |              | | (NC)       | |
>          |  ------------  |              |  ------------  |
>           ----------------                ----------------
>            | Device Configuration
>            v
> 
>      Figure 13: Example Relationship of IETF Network Slice
> Coordination
> 
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