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

Adrian Farrel <adrian@olddog.co.uk> Wed, 03 August 2022 20:08 UTC

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From: "Adrian Farrel" <adrian@olddog.co.uk>
To: "'LUIS MIGUEL CONTRERAS MURILLO'" <luismiguel.contrerasmurillo@telefonica.com>
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Date: Wed, 3 Aug 2022 21:08:09 +0100
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Subject: Re: [Teas] Two more examples for draft-ietf-teas-ietf-network-slices
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Hi Luis,

Thanks for reading and commenting.

I think it is certainly true that what the upper layer asks of the lower layer is more than a simple connection: it may be a whole set of connectivity constructs that provide complex connectivity between the SDPs. It's also true that the operator that provides the network slice may choose to operate it as a virtual network.

However, what is going on here is that the service request is for a network slice service not for a virtual network. If the higher layer wants to request a virtual network (possibly to use as an NRP) then or course it can. There is some discussion of this in section 5.2 with references to RFC 7926 and RFC 8453.

A

-----Original Message-----
From: LUIS MIGUEL CONTRERAS MURILLO <luismiguel.contrerasmurillo@telefonica.com> 
Sent: 03 August 2022 12:35
To: adrian@olddog.co.uk; teas@ietf.org
Subject: RE: [Teas] Two more examples for draft-ietf-teas-ietf-network-slices

HI Adrian,

One additional comment from my side, in this case for A.5 text.

On the hierarchical approach you mention that
" ... 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."

I think it would be more generic to reference the fact that the lower layer network could present to the higher layer a topology rather than a link. I mean, a representation that could be similar to the filter topology as in the normal case is provided by the network controller, but being realized as a slice in the context of A.5. The extreme case of such a filter topology would be a virtual link, but in generic terms we could expect a filter topology.

Best regards

Luis

-----Mensaje original-----
De: Teas <teas-bounces@ietf.org> En nombre de Adrian Farrel
Enviado el: domingo, 31 de julio de 2022 10:10
Para: teas@ietf.org
Asunto: [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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