Interconnecting (or Stitching) Network Slice Subnets
draft-defoy-coms-subnet-interconnection-01

Versions: 00 01                                                         
none                                                           X. de Foy
Internet-Draft                                                 A. Rahman
Intended status: Informational                         InterDigital Inc.
Expires: April 6, 2018                                   October 3, 2017


                 Interconnecting Network Slice Subnets
               draft-defoy-coms-subnet-interconnection-00

Abstract

   This document aims to define a network slice subnet as a general
   concept, and to augment a baseline network slice model with
   attributes that describe interconnections between network slice
   subnets.

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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
     1.1.  Terminology . . . . . . . . . . . . . . . . . . . . . . .   3
   2.  Interconnection Concepts  . . . . . . . . . . . . . . . . . .   3
   3.  Information Model . . . . . . . . . . . . . . . . . . . . . .   5
   4.  Operations  . . . . . . . . . . . . . . . . . . . . . . . . .   5
   5.  Security Considerations . . . . . . . . . . . . . . . . . . .   5
   6.  Next Steps  . . . . . . . . . . . . . . . . . . . . . . . . .   6
   7.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   6
   8.  Informative References  . . . . . . . . . . . . . . . . . . .   6
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .   7

1.  Introduction

   Network Slicing enables creating end-to-end partitioned virtual
   networks, including compute and storage resources, to deploy services
   with diverse requirements over the same infrastructure.
   [I-D.geng-coms-problem-statement] describes a problem statement for
   supervised heterogeneous network slicing, enabling users to deploy
   network slices including connectivity, computing and storage
   components.

   Nevertheless, defining and managing a network slice (NS) end-to-end
   does not always have to be done directly: it may be convenient to
   define and manage subsets of NS components.  The concept of network
   slice subnet is defined originally in [NGMN_Network_Slicing], though
   we only need to retain its definition in the most general form:
   network slice subnet instances are comprised of network, compute and
   storage resources, but cannot be operated in isolation as a complete
   network slice.  They must be interconnected with other NS subnets to
   form a complete, end-to-end network slice.  To summarize: a NS subnet
   can be seen as a network slice with unconnected links.  The term
   network slice segments has also occasionally been used to designate
   NS subnets.  Use cases for using NS subnets include managing multi-
   domain network slices, or even within one domain, isolate management
   and maintenance of different portions of a network slice.

   A model for network slicing is currently being defined in
   [I-D.qiang-coms-netslicing-information-model].  One question we would
   like to address is how to augment this base model to describe
   interconnections between NS subnets.  The base model is not
   technology specific, and therefore the description of
   interconnections should not be either.  Moreover, such an
   augmentation should both enable describing the intent for
   interconnection, as well as describing actual interconnections once
   NS subnets have been stitched together.




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1.1.  Terminology

   Network slicing related terminology used in this document should be
   interpreted as described in [I-D.geng-coms-problem-statement].

   Note: in this text we refer to termination points, as defined in
   [I-D.ietf-i2rs-yang-network-topo], while a similar concept is called
   "port" in [I-D.qiang-coms-netslicing-information-model].  Terminology
   will be adjusted as needed later on.

2.  Interconnection Concepts

   The general goal of an interconnection between 2 NS subnets is to
   have links established between nodes from both subnets.  A secondary
   goal is to keep NS subnet descriptions isolated from each other (to
   some extent that is still to be defined).  This relative isolation
   will contribute to simplify and decentralize management, as well as
   enabling operations such as substituting a subnet with another, etc.

   As described in Figure 1, we can represent a network slice subnet as
   a network slice that also has one or more logical nodes, which
   terminate (at logical termination points) links that need to be
   interconnected with external nodes (cross-subnet links).

   During a stitching operation, logical termination points from both NS
   subnets can be paired together into an interconnection point.  When
   implemented at the infrastructure layer, this interconnection point
   may be either implemented as a gateway, or abstracted away, in which
   case nodes from both NS subnets end up being directly interconnected
   between each other.  In any cases, interconnected links will need to
   have compatible QoS attributes.




















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                               Slice Provider
                                     |
   +---------------------------------v---------------------------------+
   |  Slice Manager                                                    |
   |                                                                   |
   | +---------------------------------------------------------------+ |
   | |   Data model: network slice composed of NS subnet 1 and 2     | |
   | |                                                               | |
   | |      Network Slice Subnet 1            Network Slice Subnet 2 | |
   | | +---------------------------+  +----------------------------+ | |
   | | |     cross-subnet link     |  |   cross-subnet             | | |
   | | |    +----------------+     |  |       link    +------+     | | |
   | | |    |                |     |  |      +--------o node |     | | |
   | | |    |                |Interconnection|        +---o--+     | | |
   | | |+---o--+     +-------|-----+--+------|------+     |        | | |
   | | || node |     |       |     |  |      |      |     |        | | |
   | | |+---o--+     | +-----|---+ |  | +----|----+ |     |        | | |
   | | |    |        | |     |   | |  | |    |    | |     |        | | |
   | | |    |        | |     o - - - - - - - o    | |     |        | | |
   | | |    |        | |         | |  | |         | |     |        | | |
   | | |    |        | | logical | |  | | logical | |     |        | | |
   | | |    |        | |  node   | |  | |  node   | |     |        | | |
   | | |    |        | |         | |  | |         | |     +---+    | | |
   | | |    |        | |     o - - - - - - - o    | |         |    | | |
   | | |    |        | |     |   | |  | |    |    | |         |    | | |
   | | |    |        | +-----|---+ |  | +----|----+ |     +---o--+ | | |
   | | |    |        |       |     |  |      |      |     | node | | | |
   | | |    |        +-------|-----+--+------|------+     +---o--+ | | |
   | | |    | +------+       |     |  |      |                |    | | |
   | | |    +-o node o-------+     |  |      +----------------+    | | |
   | | |      +------+ cross-subnet|  |         cross-subnet       | | |
   | | |                link       |  |           link             | | |
   | | +---------------------------+  +----------------------------+ | |
   | +---------------------------------------------------------------+ |
   +--------------------------------+----------------------------------+
                                    |
                                    v
                            Network Infrastructure

              Figure 1: Network Slice Subnets Interconnection

   Network slice interconnection information in data models can be used
   for different related purposes:

   o  Anchoring interconnections at logical termination points: a NS
      subnet model should specify which link termination points are the
      "network slice subnet boundaries" that need to be interconnected.




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   o  Programming interconnections: a NS provider may set attributes in
      a NS subnet model to configure the interconnection with another NS
      subnet.

   o  Describing the state of interconnection (once NS subnets are
      interconnected).

3.  Information Model

   A fairly minimal way to represent an interconnection is:

   o  To represent an interconnection anchor in a subnet: a logical
      termination point in this subnet.

   o  To program or represent an interconnection between subnets: a pair
      of logical termination points, one in each subnet.

   Some form of grouping of logical termination points (for example, in
   logical nodes) may tell the NS manager to treat those termination
   points as a single unit for placement, implementation, etc.

   Additional information may be useful to complement the description of
   an interconnections.  Some attributes may be useful to describe an
   interconnection point anchor, while others may be useful to program
   or represent the state of an interconnection.  For example, logical
   termination points may be associated with information that
   facilitates placement or stitching operations.  Future work should
   determine what type of information would be useful to specify or
   represent a NS interconnection.

4.  Operations

   Stitching may occur when network slice subnets are initially
   instantiated, or later after instantiation.

5.  Security Considerations

   Access control mechanisms for managing network slices can likely be
   reused for network slice subnets, since their models should be
   similar to each other.

   Stitching 2 NS subnets together may be subject to some form of
   authorization by a NS tenant.








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6.  Next Steps

   The present draft investigates one aspect of a non-technology
   specific representation of a network slice.  It may therefore be part
   of the larger discussion on the need for such a representation.

   Beyond this, next steps can include the following:

   o  Discussing the definition and need for NS subnets.  Is "NS with
      unconnected links" an adequate simple definition?  Is there an
      agreement on the use cases?  Should NS subnet interconnection be
      standardized?

   o  Assuming there is some interest in this, further work is needed to
      better understand what attributes and operations are needed, and
      how to integrate them in a baseline NS model.

7.  IANA Considerations

   This document has no actions for IANA.

8.  Informative References

   [I-D.geng-coms-problem-statement]
              67, 4., Slawomir, S., Qiang, L., Matsushima, S., Galis,
              A., and L. Contreras, "Problem Statement of Supervised
              Heterogeneous Network Slicing", draft-geng-coms-problem-
              statement-00 (work in progress), September 2017.

   [I-D.ietf-i2rs-yang-network-topo]
              Clemm, A., Medved, J., Varga, R., Bahadur, N.,
              Ananthakrishnan, H., and X. Liu, "A Data Model for Network
              Topologies", draft-ietf-i2rs-yang-network-topo-16 (work in
              progress), September 2017.

   [I-D.qiang-coms-netslicing-information-model]
              Qiang, L., Galis, A., 67, 4., kiran.makhijani@huawei.com,
              k., Martinez-Julia, P., and H. Flinck, "Technology
              Independent Information Model for Network Slicing", draft-
              qiang-coms-netslicing-information-model-00 (work in
              progress), September 2017.

   [NGMN_Network_Slicing]
              NGMN, "Description of Network Slicing Concept", 10 2016,
              <https://www.ngmn.org/uploads/
              media/161010_NGMN_Network_Slicing_framework_v1.0.8.pdf>.





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Authors' Addresses

   Xavier de Foy
   InterDigital Inc.
   1000 Sherbrooke West
   Montreal
   Canada

   Email: Xavier.Defoy@InterDigital.com


   Akbar Rahman
   InterDigital Inc.
   1000 Sherbrooke West
   Montreal
   Canada

   Email: Akbar.Rahman@InterDigital.com

































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