teas                                                            R. Rokui
Internet-Draft                                                     Nokia
Intended status: Informational                                  S. Homma
Expires: May 6, 2021                                                 NTT
                                                            K. Makhijani
                                                           LM. Contreras
                                                             J. Tantsura
                                                            Apstra, Inc.
                                                        November 2, 2020

                   Definition of IETF Network Slices


   This document provides a definition of the term "IETF Network Slice"
   for use within the IETF and specifically as a reference for other
   IETF documents that describe or use aspects of network slices.

   The document also describes the characteristics of an IETF network
   slice, related terms and their meanings, and explains how IETF
   network slices can be used in combination with end-to-end network
   slices or independent of them.

Status of This Memo

   This Internet-Draft is submitted in full conformance with the
   provisions of BCP 78 and BCP 79.

   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF).  Note that other groups may also distribute
   working documents as Internet-Drafts.  The list of current Internet-
   Drafts is at https://datatracker.ietf.org/drafts/current/.

   Internet-Drafts are draft documents valid for a maximum of six months
   and may be updated, replaced, or obsoleted by other documents at any
   time.  It is inappropriate to use Internet-Drafts as reference
   material or to cite them other than as "work in progress."

   This Internet-Draft will expire on May 6, 2021.

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Copyright Notice

   Copyright (c) 2020 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents
   (https://trustee.ietf.org/license-info) in effect on the date of
   publication of this document.  Please review these documents
   carefully, as they describe your rights and restrictions with respect
   to this document.  Code Components extracted from this document must
   include Simplified BSD License text as described in Section 4.e of
   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
     1.1.  Rationale . . . . . . . . . . . . . . . . . . . . . . . .   3
   2.  Terms and Abbreviations . . . . . . . . . . . . . . . . . . .   4
   3.  Definition and Scope of IETF Network Slice  . . . . . . . . .   4
   4.  IETF Network Slice System Characteristics . . . . . . . . . .   5
     4.1.  Objectives for IETF Network Slices  . . . . . . . . . . .   5
       4.1.1.  Service Level Objectives  . . . . . . . . . . . . . .   5
       4.1.2.  Minimal Set of SLOs . . . . . . . . . . . . . . . . .   6
       4.1.3.  Other Objectives  . . . . . . . . . . . . . . . . . .   7
     4.2.  IETF Network Slice Endpoints  . . . . . . . . . . . . . .   7
       4.2.1.  IETF Network Slice Connectivity Types . . . . . . . .   9
     4.3.  IETF Network Slice Composition  . . . . . . . . . . . . .   9
   5.  IETF Network Slice Structure  . . . . . . . . . . . . . . . .  10
   6.  IETF Network Slice Stakeholders . . . . . . . . . . . . . . .  11
   7.  IETF Network Slice Controller Interfaces  . . . . . . . . . .  12
   8.  Realizing IETF Network Slice  . . . . . . . . . . . . . . . .  12
   9.  Isolation in IETF Network Slices  . . . . . . . . . . . . . .  13
     9.1.  Isolation as a Service Requirement  . . . . . . . . . . .  13
     9.2.  Isolation in IETF Network Slice Realization . . . . . . .  14
     9.3.  Relationship with Isolation in 5G Network Slice . . . . .  14
   10. Security Considerations . . . . . . . . . . . . . . . . . . .  14
   11. IANA Considerations . . . . . . . . . . . . . . . . . . . . .  15
   12. Acknowledgment  . . . . . . . . . . . . . . . . . . . . . . .  15
   13. Informative References  . . . . . . . . . . . . . . . . . . .  15
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  17

1.  Introduction

   A number of use cases benefit from network connections that along
   with the connectivity provide assurance of meeting a specific set of
   objectives wrt network resources use.  In this document, as detailed

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   in the subsequent sections, we refer to this connectivity and
   resource commitment as an IETF network slice.  Services that might
   benefit from the network slices include but not limited to:

   o  5G services (e.g. eMBB, URLLC, mMTC)(See [TS.23.501-3GPP])

   o  Network wholesale services

   o  Network infrastructure sharing among operators

   o  NFV connectivity and Data Center Interconnect

   The use cases are further described in [I-D.nsdt-teas-ns-framework].

   This document defines the concept of IETF Network Slices that provide
   connectivity coupled with a set of specific commitments of network
   resources between a number of endpoints over a shared network
   infrastructure.  Since the term network slice is rather generic, the
   qualifying term 'IETF' is used in this document to limit the scope of
   network slice to network technologies described and standardized by
   the IETF.

1.1.  Rationale

   IETF Network Slices are created and managed within the scope of one
   or more network technologies (e.g., IP, MPLS, optical).  They are
   intended to enable a diverse set of applications that have different
   requirements to coexist on the same network infrastructure.

   An IETF Network Slice is a well-defined structure of connectivity
   requirements and associated network behaviors.  IETF Network Slices
   are defined such that they are independent of the underlying
   infrastructure connectivity and technologies used.  This is to allow
   an IETF Network Slice consumer to describe their network connectivity
   and relevant objectives in a common format, independent of the
   underlying technologies used.

   IETF Network Slices may be combined hierarchically, so that a network
   slice may itself be sliced.  They may also be combined sequentially
   so that various different networks can each be sliced and the network
   slices placed into a sequence to provide an end-to-end service.  This
   form of sequential combination is utilized in some services such as
   in 3GPP's 5G network [TS.23.501-3GPP].

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2.  Terms and Abbreviations

   The terms and abbreviations used in this document are listed below.

   o  NS: Network Slice

   o  NSC: Network Slice Controller

   o  NBI: NorthBound Interface

   o  SBI: SouthBound Interface

   o  SLI: Service Level Indicator

   o  SLO: Service Level Objective

   o  SLA: Service Level Agreement

   The above terminology is defined in greater details in the remainder
   of this document.

3.  Definition and Scope of IETF Network Slice

   The definition of a network slice in IETF context is as follows:

   An IETF Network Slice is a logical network topology connecting a
   number of endpoints with a set of shared or dedicated network
   resources, that are used to satisfy specific Service Level Objectives

   IETF Network Slice specification is technology-agnostic, and the
   means for IETF network slice realization can be chosen depending on
   several factors such as: service requirements, specifications or
   capabilities of underlying infrastructure.  The structure and
   different characteristics of IETF Network Slices are described in the
   following sections.

   Term "Slice" refers to a set of characteristics and behaviours that
   separate one type of user-traffic from another.  IETF Network Slice
   assumes that an underlying network is capable of changing the
   configurations of the network devices on demand, through in-band
   signaling or via controller(s) and fulfilling all or some of SLOs to
   all of the traffic in the slice or to specific flows.

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4.  IETF Network Slice System Characteristics

   The following subsections describe the characteristics of IETF
   network slices.

4.1.  Objectives for IETF Network Slices

   An IETF Network Slice is defined in terms of several quantifiable
   characteristics or service level objectives (SLOs).  SLOs along with
   terms Service Level Indicator (SLI) and Service Level Agreement (SLA)
   are used to define the performance of a service at different levels.

   A Service Level Indicator (SLI) is a quantifiable measure of an
   aspect of the performance of a network.  For example, it may be a
   measure of throughput in bits per second, or it may be a measure of
   latency in milliseconds.

   A Service Level Objective (SLO) is a target value or range for the
   measurements returned by observation of an SLI.  For example, an SLO
   may be expressed as "SLI <= target", or "lower bound <= SLI <= upper
   bound".  A network slice is expressed in terms of the set of SLOs
   that are to be delivered for the different connections between

   A Service Level Agreement (SLA) is an explicit or implicit contract
   between the consumer of an IETF Network Slice and the provider of the
   slice.  The SLA is expressed in terms of a set of SLOs and may
   include commercial terms as well as the consequences of missing/
   violating the SLOs they contain.

   Additional descriptions of IETF network slice attributes is covered
   in [I-D.contreras-teas-slice-nbi].

4.1.1.  Service Level Objectives

   SLOs define a set of network attributes and characteristics that
   describe an IETF network slice.  SLOs do not describe 'how' the IETF
   network slices are implemented or realized in the underlying network
   layers.  Instead, they are defined in terms of dimensions of
   operation (time, capacity, etc.), availability, and other attributes.
   An IETF network slice can have one or more SLOs associated with it.
   The SLOs are combined in an SLA.  The SLOs are defined for sets of
   two or more endpoints and apply to specific directions of traffic
   flow.  That is, they apply to specific source endpoints and specific
   connections between endpoints within the set of endpoints and
   connections in the network slice.

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4.1.2.  Minimal Set of SLOs

   This document defines a minimal set of SLOs and later systems or
   standards could extend this set as per Section 4.1.3.

   SLOs can be categorized in to 'Directly Measurable Objectives' or
   'Indirectly Measurable Objectives'.  Objectives such as guaranteed
   minimum bandwidth, guaranteed maximum latency, maximum permissible
   delay variation, maximum permissible packet loss rate, and
   availability are 'Directly Measurable Objectives'.  While 'Indirectly
   Measurable Objectives' include security, geographical restrictions,
   maximum occupancy level objectives.  The later standard might define
   other SLOs as needed.

   Editor's Note TODO: Minimal set describes most commonly used
   objectives to describe network behavior.  Other directly or
   indirectly measurable objectives may be requested by that customer of
   an IETF network slice.

   The definition of these objectives are as follows:

      Guaranteed Minimum Bandwidth

         Minimum guaranteed bandwidth between two endpoints at any time.
         The bandwidth is measured in data rate units of bits per second
         and is measured unidirectionally.

      Guaranteed Maximum Latency

         Upper bound of network latency when transmitting between two
         endpoints.  The latency is measured in terms of network
         characteristics (excluding application-level latency).
         [RFC2681] and [RFC7679] discuss round trip times and one-way
         metrics, respectively.

      Maximum Permissible Delay Variation

         Packet delay variation (PDV) as defined by [RFC3393], s the
         difference in the one-way delay between sequential packets in a
         flow.  This SLO sets a maximum value PDV for packets between
         two endpoints.

      Maximum permissible packet loss rate

         The ratio of packets dropped to packets transmitted between two
         endpoints over a period of time.  See [RFC7680]


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         The ratio of uptime to the sum of uptime and downtime, where
         uptime is the time the IETF network slice is available in
         accordance with the SLOs associated with it.


         An IETF Network Slice consumer may request that the network
         applies encryption or other security techniques to traffic
         flowing between endpoints.

         Note that the use of security or the violation of this SLO is
         not directly observable by the IETF Network Slice consumer and
         cannot be measured as a quantifiable metric.

         Also note that the objective may include request for encryption
         (e.g., [RFC4303]) between the two endpoints explicitly to meet
         architecture recommendations as in [TS33.210] or for compliance
         with [HIPAA] and/or [PCI].

         Editor's Note: Please see more discussion on security in
         Section 10.

4.1.3.  Other Objectives

   Additional SLOs may be defined to provide additional description of
   the IETF network slice that a consumer requests.

   If the IETF Network Slice consumer service is traffic aware, other
   traffic specific characteristics may be valuable including MTU,
   traffic-type (e.g., IPv4, IPv6, Ethernet or unstructured), or a
   higher-level behavior to process traffic according to user-
   application (which may be realized using network functions).

   Maximal occupancy for an IETF network slice should be provided.
   Since it carries traffic for multiple flows between the two
   endpoints, the objectives should also say if they are for the entire
   connection, group of flows or on per flow basis.  Maximal occupancy
   should specify the scale of the flows (i.e. maximum number of flows
   to be admitted) and optionally a maximum number of countable resource
   units, e.g IP or MAC addresses a slice might consume.

4.2.  IETF Network Slice Endpoints

   As noted in Section 3, an IETF network slice describes connectivity
   between endpoints across the underlying network.  This connectivity
   may be be point-to-point, point-to-multipoint (P2MP), multipoint-to-
   point, or multipoint-to-multipoint.

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   The characteristics of IETF network slice endpoints (NSEs) are as

   o  They are conceptual points of connection of a customer network,
      network function, device, or application to the IETF network
      slice.  This might include routers, switches, firewalls, WAN,
      4G/5G RAN nodes, 4G/5G Core nodes, application acceleration, Deep
      Packet Inspection (DPI), server load balancers, NAT44 [RFC3022],
      NAT64 [RFC6146], HTTP header enrichment functions, and TCP

   o  They are identified in a request provided by the consumer of an
      IETF Network Slice when the IETF Network Slice is requested.

   o  An NSE is identified a unique identifier and/or a unique name and
      other data.  A non-exhaustive list of other data includes IPv4 or
      IPv6 address, VLAN tag, port number, connectivity type (P2P, P2MP,

   Note that the NSE is different from access points (AP) defined in
   [RFC8453] as an AP is a logical identifier to identify the shared
   link between the customer and the operator where as NSE is an
   identifier of an endpoint.  Also NSE is different from TE Link
   Termination Point (LTP) defined in [I-D.ietf-teas-yang-te-topo] as it
   is a conceptual point of connection of a TE node to one of the TE
   links on a TE node.

   The NSE is similar to the Termination Point (TP) defined in [RFC8345]
   and can contain more attributes.  NSE could be modeled by augmenting
   the TP model.

   There is another type of the endpoints called "IETF Network Slice
   Realization Endpoints (NSREs)".  These endpoints are allocated and
   assigned by the network controller during the realization of an IETF
   Network Slice and are technology-specific, i.e.  they depend on the
   network technology used during the IETF Network Slice realization.
   The identification of NSREs forms part of the realization of the IETF
   Network Slice and is implementation and deployment specific.

   Figure 1 shows an example of an IETF Network Slice and its
   realization between multiple NSEs and NSREs.

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                          ( IETF scoped Network )
        DAN1             (                       )                DAN2
     --------  NSRE1 --------                  -------- NSRE2   --------
     |    o |-------o|  A   |                  |  B   |o--------| o    |
     |  NSE1|        --------                  --------         | NSE2 |
     --------        |   (                        )    |        --------
          |          |    (                      )     |          |
          |          |     (-------------------)       |          |
          |          |                                 |          |
          |          | <=============================> |          |
          |             IETF Network Slice realization            |
          |                 between NSRE1 and NSRE2               |
          |                                                       |
          | <===================================================> |
               IETF Network Slice between NSE1 and NSE2 with SLO1

      DAN: Device, application and/or network function

     Figure 1: An IETF Network Slice between NSEs and its realization
                               between NSREs

4.2.1.  IETF Network Slice Connectivity Types

   The IETF Network Slice connection types can be point to point (P2P),
   point to multipoint (P2MP), multi-point to point (MP2P), or multi-
   point to multi-point (MP2MP).  They will requested by the higher
   level operation system.

4.3.  IETF Network Slice Composition

   Operationally, an IETF Network Slice maybe decomposed in two or more
   IETF Network Slices as specified below.  Decomposed network slices
   are then independently realized and managed.

   o  Hierarchical (i.e., recursive) composition: An IETF Network Slice
      can be further sliced into other network slices.  Recursive
      composition allows an IETF Network Slice at one layer to be used
      by the other layers.  This type of multi-layer vertical IETF
      Network Slice associates resources at different layers.

   o  Sequential composition: Different IETF Network Slices can be
      placed into a sequence to provide an end-to-end service.  In
      sequential composition, each IETF Network Slice would potentially
      support different dataplanes that need to be stitched together.

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5.  IETF Network Slice Structure

   Editor's note: This content of this section merged with Relationship
   with E2E slice discussion.

   An IETF Network Slice is a set of connections among various endpoints
   to form a logical network that meets the SLOs agreed upon.

           [EP11]------/                           /--[EP21]
                      /                           /
           [EP12]----/   IETF Network  Slice     /----[EP22]
             :      /        (SLOs e.g.         /
             :     / B/W > x bps, Delay < y ms)/

           == == == == == == == == == == == == == == == == == ==

                      .--.               .--.
           [EP11]    (    )- .          (    )- .     [EP21]
                    .'         '  SLO  .'         '
           [EP12]  (  Network-1 ) ... (  Network-p )  [EP22]
            :       `-----------'      `-----------'     :
           [EP1m]                                     [EP2n]

             SLOs in terms of attributes, e.g. BW, delay.
             EP: Endpoint
             B/W: Bandwidth

                       Figure 2: IETF Network slice

   Figure 2 illustrates a case where an IETF Network Slice provides
   connectivity between a set of endpoints pairs with specific
   characteristics for each SLO (e.g. guaranteed minimum bandwidth of x
   bps and guaranteed delay of no more than y ms).  The endpoints may be
   distributed in the underlay networks, and an IETF Network Slice can
   be deployed across multiple network domains.  Also, the endpoints on
   the same IETF Network Slice may belong to the same or different
   address spaces.

   IETF Network slice structure fits into a broader concept of end-to-
   end network slices.  A network operator may be responsible for
   delivering services over a number of technologies (such as radio
   networks) and for providing specific and fine-grained services (such

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   as CCTV feed or High definition realtime traffic data).  That
   operator may need to combine slices of various networks to produce an
   end-to-end network service.  Each of these networks may include
   multiple physical or virtual nodes and may also provide network
   functions beyond simply carrying of technology-specific protocol data
   units.An end-to-end network slice is defined by the 3GPP as a
   complete logical network that provides a service in its entirety with
   a specific assurance to the customer [TS.23.501-3GPP].

   An end-to-end network slice may be composed from other network slices
   that include IETF Network Slices.  This composition may include the
   hierarchical (or recursive) use of underlying network slices and the
   sequential (or stitched) combination of slices of different networks.

6.  IETF Network Slice Stakeholders

   An IETF Network Slice and its realization involves the following
   stakeholders and it is relevant to define them for consistent

   Consumer:  A consumer is the requester of an IETF Network Slice.
      Consumers may request monitoring of SLOs.  A consumer may manage
      the IETF Network Slice service directly by interfacing with the
      IETF Network Slice controller or indirectly through an

   Orchestrator:  An orchestrator is an entity that composes different
      services, resource and network requirements.  It interfaces with
      the IETF Network Slice controllers.

   IETF Network Slice Controller (NSC):  It realizes an IETF Network
      Slice in the underlying network, maintains and monitors the run-
      time state of resources and topologies associated with it.  A
      well-defined interface is needed between different types of IETF
      Network Slice controllers and different types of orchestrators.
      An IETF Network Slice operator (or slice operator for short)
      manages one or more IETF Network Slices using the IETF Network
      Slice Controller(s).

   Network Controller:  is a form of network infrastructure controller
      that offers network resources to NSC to realize a particular
      network slice.  These may be existing network controllers
      associated with one or more specific technologies that may be
      adapted to the function of realizing IETF Network Slices in a

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7.  IETF Network Slice Controller Interfaces

   The interworking and interoperability among the different
   stakeholders to provide common means of provisioning, operating and
   monitoring the IETF Network slices is enabled by the following
   communication interfaces (see Figure 3).

   NSC Northbound Interface (NBI):  The NSC Northbound Interface is an
      interface between a consumer's higher level operation system
      (e.g., a network slice orchestrator) and the NSC.  It is a
      technology agnostic interface.  The consumer can use this
      interface to communicate the requested characteristics and other
      requirements (i.e., the SLOs) for the IETF Network Slice, and the
      NSC can use the interface to report the operational state of an
      IETF Network Slice to the consumer.

   NSC Southbound Interface (SBI):  The NSC Southbound Interface is an
      interface between the NSC and network controllers.  It is
      technology-specific and may be built around the many network
      models defined within the IETF.

                   | Consumer higher level operation system   |
                   |   (e.g E2E network slice orchestrator)   |
                                        | NSC NBI
                   |    IETF Network Slice Controller (NSC)   |
                                        | NSC SBI
                   |           Network Controllers            |

           Figure 3: Interface of IETF Network Slice Controller

8.  Realizing IETF Network Slice

   Realization of IETF Network Slices is out of scope of this document.
   It is a mapping of the definition of the IETF Network Slice to the

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   underlying infrastructure and is necessarily technology-specific and
   achieved by the NSC over the SBI.

   The realization can be achieved in a form of either physical or
   logical connectivity through VPNs (see, for example,
   [I-D.ietf-teas-enhanced-vpn], a variety of tunneling technologies
   such as Segment Routing, MPLS, etc.  Accordingly, endpoints may be
   realized as physical or logical service or network functions.

9.  Isolation in IETF Network Slices

   Editor's note: This content is a work in progress.  The section on
   isolation is too descriptive.

   An IETF Network Slice consumer may request, that the IETF Network
   Slice delivered to them is isolated from any other network slices of
   services delivered to any other customers.  It is expected that the
   changes to the other network slices of services do not have any
   negative impact on the delivery of the IETF Network Slice.  In a more
   general sense, isolation can be classified in the following ways:

   Traffic Separation:  Traffic of one network slice should not be
      subjected to policies and forwarding rules of other network

   Interference Avoidance:  Changes in other network slices should not
      impact to the SLOs of the network slice.  Here the changes in
      other network slice may include the changes in connectivity,
      traffic volume, traffic pattern, etc.

   Service Assurance:  In case service degradation is unacceptable due
      to unpredictable network situations producing service degradation
      (e.g., major congestion events, etc.), explicit reservation of
      resources in the network maybe requested for a reduces set IETF
      network slices.

9.1.  Isolation as a Service Requirement

   Isolation is an important requirement of IETF network slices for
   services like critical services, emergencies, etc.  A consumer may
   express this request through the description of SLOs.

   This requirement can be met by simple conformance with other SLOs.
   For example, traffic congestion (interference from other services)
   might impact on the latency experienced by an IETF network slice.
   Thus, in this example, conformance to a latency SLO would be the
   primary requirement for delivery of the IETF network slice service,
   and isolation from other services might be only a means to that end.

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   It should be noted that some aspects of isolation may be measurable
   by a customer who have the information about the traffic on a number
   of IETF network slices or other services.

9.2.  Isolation in IETF Network Slice Realization

   The isolation requirement can be achieved with existing, in-
   development, and potential new technologies in IETF.

   Isolation may be achieved in the underlying network by various forms
   of resource partitioning ranging from dedicated allocation of
   resources for a specific IETF network slice, to sharing or resources
   with safeguards.  For example, traffic separation between different
   IETF network slices may be achieved using VPN technologies, such as
   L3VPN, L2VPN, EVPN, etc.  Interference avoidance may be achieved by
   network capacity planning, allocating dedicated network resources,
   traffic policing or shaping, prioritizing in using shared network
   resources, etc.  Finally, service continuity may be ensured by
   reserving backup paths for critical traffic, dedicating specific
   network resources for a selected number of network slices, etc.

9.3.  Relationship with Isolation in 5G Network Slice

   Editor's note: This 5G subsection should not be added to terminology.
   it does not add value to the definitions.

   In the context of 5G network slice, "isolation level" is listed as
   one of the attributes which can be used to characterize the type of
   network slice [GSMA Generic Network Slice Template].  For 5G network
   slice, different types of isolation are considered, including
   physical and logical isolation.  Physical isolation refers to
   different physical network entities, and logical isolation is further
   classified into virtual resource isolation, network function
   isolation and tenant/service isolation.

10.  Security Considerations

   Editor's Note: Need further improvement; work in progress.

   This document specifies terminology and has no direct effect on the
   security of implementations or deployments.

   As noted in Section 4.1.2, some aspects of security may be expressed
   in SLOs and so form part of the service delivered as an IETF network
   slice.  As further mentioned in Section 8, there is an underlying
   asumption that traffic presented to an IETF network slice will not be
   misdelivered to an endpoint that is not part of that IETF network

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   Furthermore, the nature of conformance to SLOs means that it should
   not be possible to attack an IETF network slice service by varying
   the traffic on other services or slices carried by the same underlay
   network.  This concern can be strengthened by the stipulation of
   "isolation" as an SLO.

   Note, however, that a customer wanting to secure their data and keep
   it private will be responsible for applying appropriate security
   measures to their traffic and not depending on the network operator
   that provides the IETF network slice.

11.  IANA Considerations

   This memo includes no request to IANA.

12.  Acknowledgment

   The entire TEAS NS design team and everyone participating in those
   discussion has contributed to this draft.  Particularly, Eric Gray,
   Xufeng Liu, Jie Dong, Adrian Farrel, and Jari Arkko for a thorough
   review among other contributions.

13.  Informative References

   [HIPAA]    HHS, "Health Insurance Portability and Accountability Act
              - The Security Rule", February 2003,

              Contreras, L., Homma, S., and J. Ordonez-Lucena,
              "Considerations for defining a Transport Slice NBI",
              draft-contreras-teas-slice-nbi-01 (work in progress),
              March 2020.

              Dong, J., Bryant, S., Li, Z., Miyasaka, T., and Y. Lee, "A
              Framework for Enhanced Virtual Private Networks (VPN+)
              Services", draft-ietf-teas-enhanced-vpn-05 (work in
              progress), February 2020.

              Liu, X., Bryskin, I., Beeram, V., Saad, T., Shah, H., and
              O. Dios, "YANG Data Model for Traffic Engineering (TE)
              Topologies", draft-ietf-teas-yang-te-topo-22 (work in
              progress), June 2019.

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              Gray, E. and J. Drake, "Framework for Transport Network
              Slices", draft-nsdt-teas-ns-framework-02 (work in
              progress), March 2020.

   [PCI]      PCI Security Standards Council, "PCI DSS", May 2018,

   [RFC2681]  Almes, G., Kalidindi, S., and M. Zekauskas, "A Round-trip
              Delay Metric for IPPM", RFC 2681, DOI 10.17487/RFC2681,
              September 1999, <https://www.rfc-editor.org/info/rfc2681>.

   [RFC3022]  Srisuresh, P. and K. Egevang, "Traditional IP Network
              Address Translator (Traditional NAT)", RFC 3022,
              DOI 10.17487/RFC3022, January 2001,

   [RFC3393]  Demichelis, C. and P. Chimento, "IP Packet Delay Variation
              Metric for IP Performance Metrics (IPPM)", RFC 3393,
              DOI 10.17487/RFC3393, November 2002,

   [RFC4303]  Kent, S., "IP Encapsulating Security Payload (ESP)",
              RFC 4303, DOI 10.17487/RFC4303, December 2005,

   [RFC6146]  Bagnulo, M., Matthews, P., and I. van Beijnum, "Stateful
              NAT64: Network Address and Protocol Translation from IPv6
              Clients to IPv4 Servers", RFC 6146, DOI 10.17487/RFC6146,
              April 2011, <https://www.rfc-editor.org/info/rfc6146>.

   [RFC7679]  Almes, G., Kalidindi, S., Zekauskas, M., and A. Morton,
              Ed., "A One-Way Delay Metric for IP Performance Metrics
              (IPPM)", STD 81, RFC 7679, DOI 10.17487/RFC7679, January
              2016, <https://www.rfc-editor.org/info/rfc7679>.

   [RFC7680]  Almes, G., Kalidindi, S., Zekauskas, M., and A. Morton,
              Ed., "A One-Way Loss Metric for IP Performance Metrics
              (IPPM)", STD 82, RFC 7680, DOI 10.17487/RFC7680, January
              2016, <https://www.rfc-editor.org/info/rfc7680>.

   [RFC8345]  Clemm, A., Medved, J., Varga, R., Bahadur, N.,
              Ananthakrishnan, H., and X. Liu, "A YANG Data Model for
              Network Topologies", RFC 8345, DOI 10.17487/RFC8345, March
              2018, <https://www.rfc-editor.org/info/rfc8345>.

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   [RFC8453]  Ceccarelli, D., Ed. and Y. Lee, Ed., "Framework for
              Abstraction and Control of TE Networks (ACTN)", RFC 8453,
              DOI 10.17487/RFC8453, August 2018,

              3rd Generation Partnership Project (3GPP), "3GPP TS 23.501
              (V16.2.0): System Architecture for the 5G System (5GS);
              Stage 2 (Release 16)", September 2019,

              3GPP, "3G security; Network Domain Security (NDS); IP
              network layer security (Release 14).", December 2016,

Authors' Addresses

   Reza Rokui

   Email: reza.rokui@nokia.com

   Shunsuke Homma

   Email: shunsuke.homma.ietf@gmail.com

   Kiran Makhijani

   Email: kiranm@futurewei.com

   Luis M. Contreras

   Email: luismiguel.contrerasmurillo@telefonica.com

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   Jeff Tantsura
   Apstra, Inc.

   Email: jefftant.ietf@gmail.com

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