IETF Definition of Transport Slice
draft-nsdt-teas-transport-slice-definition-00

Document Type Active Internet-Draft (individual)
Last updated 2019-11-03
Stream (None)
Intended RFC status (None)
Formats plain text xml pdf htmlized bibtex
Stream Stream state (No stream defined)
Consensus Boilerplate Unknown
RFC Editor Note (None)
IESG IESG state I-D Exists
Telechat date
Responsible AD (None)
Send notices to (None)
teas                                                            R. Rokui
Internet-Draft                                                     Nokia
Intended status: Informational                                  S. Homma
Expires: May 5, 2020                                                 NTT
                                                            K. Makhijani
                                                               Futurewei
                                                        November 2, 2019

                   IETF Definition of Transport Slice
             draft-nsdt-teas-transport-slice-definition-00

Abstract

   This document describes the definition of transport slice in IETF and
   considerations on implementation (realization) of transport slice.
   This work is part of work on TEAS WG network slicing Design Team.

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 5, 2020.

Copyright Notice

   Copyright (c) 2019 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

Rokui, et al.              Expires May 5, 2020                  [Page 1]
Internet-Draft draft-nsdt-teas-transport-slice-definition  November 2019

   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  High level architecture of end-to-end network slicing . . . .   3
   3.  IETF Definition of Transport slice  . . . . . . . . . . . . .   5
     3.1.  Scenario-1  . . . . . . . . . . . . . . . . . . . . . . .   6
     3.2.  Scenario-2  . . . . . . . . . . . . . . . . . . . . . . .   7
     3.3.  Scenario-3  . . . . . . . . . . . . . . . . . . . . . . .   7
   4.  Implementation (aka Realization) of Transport slice . . . . .   9
     4.1.  Implementation of Scenario-1  . . . . . . . . . . . . . .   9
     4.2.  Implementation of Scenario-2  . . . . . . . . . . . . . .  11
     4.3.  Implementation of Scenario-3  . . . . . . . . . . . . . .  12
   5.  Definition of SLA and Isolation levels  . . . . . . . . . . .  15
   6.  Informative References  . . . . . . . . . . . . . . . . . . .  15
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  15

1.  Introduction

   Network slicing is an approach to provide separate virtual networks
   depending on requirements of each service.  Network slicing receives
   attention due to factors such as diversity of services and devices,
   and it is also a fundamental concept of the 5G for applying networks
   to such various types of requirements (Ref [TS.23.501-3GPP]).
   However there are other applications which might benefit from network
   slicing.  Following is a list of other applicaitons:

   o  5G network slicig

   o  Wholesale business VPN

   o  Network sharing among operators

   o  NVVI connectivity (DCI)

   A network slice is composed of several parts such as endpoints and
   transport connecctivity between them.  However, there is no concrete
   definition of network slices established on transport and how to
   realize them.

   This document describes the definition of transport slice from IETF
   aspect and considerations on their realization as well.

Rokui, et al.              Expires May 5, 2020                  [Page 2]
Internet-Draft draft-nsdt-teas-transport-slice-definition  November 2019

2.  High level architecture of end-to-end network slicing

   To demonstrate IETF definition of both E2E network slice and
   transport slice, consider a typical network shown in Figure 1 where
   the network operator-Y has various networks of various technologies
   (e.g.  IP, MPLS, Optics, PON, Microwave, 5G RAN, 5G Core etc.).  Each
   network contains one or more nodes of (aka physical or virtual
   network functions, PNFs or VNFs), which have various capabilities and
   technologies such as:

   o  Routers

   o  Switches

   o  Application servers

   o  Firewalls

   o  4G/5G RAN nodes

   o  4G/5G Core nodes

   o  etc.

   Each node (aka endpoint) in the network might support various
   technologies such as IP, MPLS, Microwave, 5G RAN, 5G Core etc.  For
   example,

   o  Network-1 might contains multiple 5G gNBs connected to a few
      routers as Cell Site Gateways (CSG).

   o  Network-3 might have one or more L2/L3 routers and switches which
      are running on top on Optical network.

   o  Network-2 might have a few nodes of 5G RAN which are connected by
      PON.

Rokui, et al.              Expires May 5, 2020                  [Page 3]
Internet-Draft draft-nsdt-teas-transport-slice-definition  November 2019

         <========================= E2E NS =====================>

         <-OS1-> <-TS1-> <-TS2-> <-OS2->    ...   <-TSn-> <-OSm->

             .--.             .--.                    .--.
            (    )--.        (    )--.               (    )--.
           .'         '     .'         '            .'        '
   [EU-x] (  Network-1  )  (  Network-2  )   ...   (  Network-p ) [EU-y]
           `-----------'    `-----------'           `----------'

   Legends
     E2E NS: End-2-end network slice
     TSy: Transport Slice y
     OSx: Other Slice x
     EU-x: End User-x

                        Figure 1: E2E network slice

   To further clarify the concept of the E2E network slice, consider the
   network operator-Y has various customers (tenants).  One of its
   customers, needs to have a separate independent E2E logical network
   for specific service (e.g.  CCTV, autonomous driving, HD map etc) for
   specific SLA requirement (e.g. high secure connection with Latency
   less than 5ms) from End User-x (EU-x) from one side of the network to
   End User-y (EU-y) to the other side.  This E2E logical network is
   call an "E2E network slice".  A typical example of EU-x in 5G is the
   User equipment such as infotainment unit in the car, CCTV, Car for
   autonomous driving etc. and a typical example of EU-y in 5G is 5G
   application server, IMS etc.

   As shown in Figure 1 we use the term "E2E network slice" to show this
   logical i ndependent network from EU-X to EU-Y.  It is important to
   consider that an "E2E network slice" is associated to a customer
   (tenant) and a service type (e.g.  CCTV, autonomous driving etc.).
   Also there is only one E2E context between EU-x and EU-y.  Anything
   else is not E2E.

   For example, customer "City of NY" would like to connect all its CCTV
   cameras for entire city together.  To do so, it asks Operator-Y who
   has coverage in NY to create a new separate independent logical
   network with SLA requirement of B/W greater than 10Mbps.  In this
   case, a single E2E network slice (with NS ID 10) will be created by
   Operator-Y for Customer "City of NY", service type of CCT and SLA of
   10Mbps.

   It is also possible that customer and service type associate to an
   E2E network slice to be a wild card.  For instance, in above example,

Rokui, et al.              Expires May 5, 2020                  [Page 4]
Internet-Draft draft-nsdt-teas-transport-slice-definition  November 2019

   the E2E network slice 10, can be associated not only to service type
   CCTV but another service "Public Safety", i.e. NS ID 10 is used for
   two services for City of NY.

3.  IETF Definition of Transport slice

   The IETF definition of a transport slice is as follows:

   A Transport Slice is an abstract network topology connecting
   different endpoints with appropriate isolation and specific Service
   Level Agreement (SLA) described in terms of shared or dedicated
   network resources, level of isolation etc.

   In other words, a transport slice is a group of connections which
   connecting various endpointss in the network to achieve specific SLA
   for a customer as shown in Figure 2.  Examples of the endpoints are
   any physical or virtual network functions (PNF/VNF) or any network
   services.

                    <-------  Transport slice -------->

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

              Legend
                EP: Endpoint

                         Figure 2: Transport slice

   Referring to Figure 1, when operator-Y would like to create a
   specific E2E network slice, it should create one or more of two types
   of artefacts:

   o  Transport slice (aka Transport sub-slices or Transport sub-nets)

   o  Other slice (aka Other sub-slices or other sub-nets)

   As shown in Figure 1, an E2E network slice might have one or more of
   "Transport Slices" and one or more of "Other Slices" of any
   combinations.  One of the critical parts of an E2E network slice is
   "Transport Slices" which provides various connections with certain
   SLA between various nodes (aka endpoints).

Rokui, et al.              Expires May 5, 2020                  [Page 5]
Internet-Draft draft-nsdt-teas-transport-slice-definition  November 2019

   "The Other Slices" is out-of-scope of current work but in summary
   they contain various context or personality in the network to support
   a specific e2e network slice, i.e. The "Other Slices" are referred to
   as slices created by networks or components where IETF protocols do
   not strictly apply and operator can choose any method for defining
   them.  For instance, in 5G, the prime example of these slices are:

   o  5G RAN slice (aka RAN sub-slice, RAN sub-net or RAN-NNSI):
      Contains the context or personality on various 5G RAN network
      functions (e.g. gNB, eNB, CU, DU etc) in support of specific e2e
      network slice with certain SLA

   o  5G Core slice (aka Core sub-slice, Core sub-net or Core-NNSI):
      Contains the context or personality on various 5G Core network
      functions (e.g UPF, SMF, AMF, etc) in support of specific e2e
      network slice with certain SLA

   Figure 2 demonstrates the definition of a Transport Slice where a
   single Transport slice provides connectivity between "m" endpoints on
   left hand side to "n" endpoints on right hand side with specific
   characteristic for Service Level Agreement (SLA).

   Each transport slice has main characteristics:

   o  Transport slice definition: Technology agnostic to address a set
      of connections between various endpoints with certain SLA

   o  Transport slice Implementation (aka realization): In addition to
      its definition, a Transport Slice has an implementation (aka
      realization) in the operator's network.  Unlike transport slice
      definition, its implementation (aka realization) might be
      technology specific.

   A few examples below demonstrate the idea of transport slice in
   various scenarios.

3.1.  Scenario-1

   Figure 3 depicts an example of transport slice connecting two 5G RAN
   nodes (gNB) to three 5G Core user plan function nodes (UPF).  In this
   case a transport slice 20 is created with SLA of latency 10 [msec] or
   better between 5G endpoints gNBs and UPFs.

Rokui, et al.              Expires May 5, 2020                  [Page 6]
Internet-Draft draft-nsdt-teas-transport-slice-definition  November 2019

                    <--- Transport slice(TS ID:20) --->
                         with SLA of latency, less
                         than 10[msec]

                        .--.              .--.
              [gNB1]   (    )--.         (    )--.    [UPF1]
                      .'Network '      .' Network '
                     (  Midhaul  )    (   Backhaul )  [UPF2]
              [gNB2]  `----------'     `-----------'
                                                      [UPF3]

    Figure 3: Example of Transport Slice 20 connecting gNBs to 5G Core
                                    UPF

3.2.  Scenario-2

   Figure 4 depicts another example where transport slice 30 is created
   to connect router ER1 to two firewall endpoints with SLA of 10 [Mbps]
   or higher bandwidth.

                   <--- Transport slice(TS ID:30) --->
                          with SLA B/W 5Mbps

                                .----.
                               (      )----.
                          .---'             '----.    [FW1]
               [ER1]     (          Network       )
                         `-----------------------'    [FW2]

               Legends
                 ER: Edge Router
                 FW: Firewall

       Figure 4: Example of Transport Slice connecting Router to two
                                 firewalls

3.3.  Scenario-3

   Another example of transport slice is SFC case as shown in Figure 5
   and Figure 6 which depict an example with SF1 and SF2 (e.g.  DPI,
   Firewall, WAF, video optimizer, content cache server, NAT/CGN, Load
   balancer) and the transport slice between ER1 and ER2 traverses these
   SFs.  There are two approaches:

Rokui, et al.              Expires May 5, 2020                  [Page 7]
Internet-Draft draft-nsdt-teas-transport-slice-definition  November 2019

   o  Approach-1 shown in Figure 5 where Transport slice 40 chains
      router ER1, SF1, SF2, and router ER2.  Transport slice 40 needs
      lower than 30 ms delay.  However, endpoints SF1 and SF2 are
      implicitly identified during the transport slice implementation.
      In this case, a single transport slice is created between ER1 and
      ER2.

   o  Approach-2 shown in Figure 6 where the transport slice 40 can be
      broken into transport slices 41, 42, 43.  In this case SF1 and SF2
      are explicityly identified and as a results three transport slides
      between following endpoints will be realized:

      *  Between endpoints ER1 and SF1

      *  Between endpoints SF1 and SF2

      *  Between endpoints SF2 and ER2

                    <--- Transport slice(TS ID:40) --->
                          with SLA of latency 30ms

                         +-----+
                         | SF1 |
                         + *** +     .----.
                           * *      (      )--.
                           * *     (           )
                           * *  --' Network    '--.
               [ER1]******** *********** *************[ER2]
                         `-------------*-*--------'
                                       * *
                                     + *** +
                                     | SF2 |
                                     +-----+

     Figure 5: Approach-1: Example of Transport Slice connecting Edge
                       Routers ER1 and ER2 with SFC

Rokui, et al.              Expires May 5, 2020                  [Page 8]
Internet-Draft draft-nsdt-teas-transport-slice-definition  November 2019

                   <-- Transport slice (TS ID:40) -->
                         with SLA latency 30ms
                   <- TS41 -> <- TS42 ->  <- TS43 -->
                      SLA        SLA         SLA
                      5[ms]      20[ms]      5[ms]

                         +-----+
                         | SF1 |
                         + *** +     .----.
                           * *      (      )--.
                           * *     (           )
                           * *  --' Network    '--.
               [ER1]******** *********** *************[ER2]
                         `-------------*-*--------'
                                       * *
                                     + *** +
                                     | SF2 |
                                     +-----+

     Figure 6: Approach-2: Example of Transport Slice connecting Edge
                       Routers ER1 and ER2 with SFC

4.  Implementation (aka Realization) of Transport slice

   In addition to its definition, a Transport Slice has another
   characteristic which is its implementation (aka realization) in the
   operator's network.  Unlike transport slice definition, which is
   technology agnostics, its implementation (aka realization) is
   technology specific.  To clarify the concept of transport slice
   implementation, in following section the implementation of scenarios
   described above will be described.

4.1.  Implementation of Scenario-1

   Figure 7 depicts the implementation (realization) of the transport
   slice 20 of Figure 3.  Operator's transport slice controller receives
   an abstract API to create a transport slice between 5G endpoints gNB1
   and gNB2 to 5G Core endpoints UPF1, UPF2 and UPF3 with SLA of 10
   [ms].

   Since in most cases neither 5G RAN endpoints nor the 5G Core
   endpoints can support any IP/MPLS/Optics services, the endpoints to
   implement the transport slice 20 will not be the endpoints passed in.
   This is one of the most important aspects to consider when
   implementing the transport slices.

Rokui, et al.              Expires May 5, 2020                  [Page 9]
Internet-Draft draft-nsdt-teas-transport-slice-definition  November 2019

   As shown in Figure 7, the implementation of transport slice 20
   required the transport slice controller to find out the "best"
   endpoints which support the realization of transport slice 20 in the
   network, i.e. endpoints ER1, ER2 and ER3.  After that, the
   implementation of the transport slice 20 will be initiated by
   creation of various services/tunnels/paths between edge routers ER1,
   ER2 and ER3.  The type of Services/Tunnels/Paths depends on the
   supported technologies of endpoints ER1, ER2 and ER3.

   In this scenario, the end points of transport slice implementation
   are not those endpoints passed in, i.e.

   o  Definition of transport slice is between gNB1 and gNB2 to UPF1,
      UPF2, and UPF3

   o  Implementation of transport slice is between edge routers ER1, ER2
      and ER3

                        | Create Transport slice 20 between gNB1 & gNB2
                        | to UPF1 & UPF2 & UPF3  with SLA  latency
                        | 10 ms or better
                        v
       +-------------------------------------+
       |Operator-Y Transport Slice Controller|
       +-------------------------------------+
                        | Implement (aka Realize) transport slice 20
                        | between ER1, ER2 and ER3 with SLA latency
                        | 10 ms  or  better
                        v                          +----+
                      .----.                       +UPF1|
    [gNB1] +----+    (      )---.                 /+--=-+
         \ |    |===========================[ER2]+
          \| ER1|  (      Network       )          +----+
          /|    |===========================[ER3]+-|UPF2|
         / +----+    `----------------'         +  +----+
    [gNB2]                                       \
                                                  \+----+
                                                   +UPF3|
                                                   +----+
    Legends
      === : Tunnels & Services
      ER: Edge Router

    Figure 7: Implementation (aka Realization) of Transport slice 20 of
                                 Figure-3

Rokui, et al.              Expires May 5, 2020                 [Page 10]
Internet-Draft draft-nsdt-teas-transport-slice-definition  November 2019

4.2.  Implementation of Scenario-2

   Figure 8 depicts the realization of transport slice 30 of Figure-4.
   Operator's Transport Slice Controller receives a request to create a
   transport slice between network functions R1 and firewalls FW1 and
   FW2 with SLA of 5 [Mbps].  Depends on the underlying network
   topology, Operator's transport slice controller will implement (aka
   realize) the transport slice.  For example, if both network functions
   (i.e.  R1, FW1, FW2) and network supports segment routing, two
   Tunnels/Services of type SR can be created (or used) in the network
   between R1, FW1 and FW2 to realise the transport slice 30.  However,
   if the network just supports RSVP, two tunnels/services of type RSVP
   can be used to realize this transport slice.

   Note that since the network functions ER1, FW1 and FW2 support
   segment routing, the endpoints of the tunnels in this example are
   those endpointss passed in, i.e. the endpoints of the both transport
   slice definiton and its implementation are R1, FW1 and FW2:

   o  Definition of transport slice is between network functions R1 to
      FW1 and FW2

   o  Implementation of transport slice is between network functions R1
      to FW1 and FW2

   We will see in next example that in some scenarios this is not the
   case and the endpoints of Transport Slice definition might be
   different from endpoints of its implementation (aka realization of
   transport slices).

   It is very clear that regardless of how transport slice is realized
   in the network (i.e. using tunnels of type RSVP or SR), the
   definition of transport slice 30 does not change at all but rather
   its implementation.

Rokui, et al.              Expires May 5, 2020                 [Page 11]
Internet-Draft draft-nsdt-teas-transport-slice-definition  November 2019

                             | Create Transport slice 30 between
                             | ER1 and FW1 and FW2 with SLA 5 Mbps
                             v
            +---------------------------------------+
            | Operator-Y Transport Slice Controller |
            +---------------------------------------+
                             | Implement (aka Realize) transport
                             | slice 30 between R1 and FW1 & FW2
                             | with SLA 5  Mbps
                             v
                           .----.
         +----+      .----(      )----.
         |    |=============================[FW1]
         | ER |    (      Network       )
         |    |=============================[FW2]
         +----+      `----------------'

         Legends
           === : Tunnels & Services of type SR
                 or RSVP with SLA 5 Mbps

    Figure 8: Implementation (aka Realization) of Transport slice 30 of
                                 Figure-4

4.3.  Implementation of Scenario-3

   Figure 9 depicts the implementation (realization) of the transport
   slice 40 of Figure 5 where a transport slice needed between network
   functions R1 and R2 across SF1 and SF2.  However, the location of SF1
   and SF2 are decided internally with a logic in Transport Slice
   Controller.  For example, when SLA requires the high secure transport
   slice between ER1 and ER2 which in turn results on adding SF2 and SF2
   to the implementation of transport slice 40 implicitly by transport
   slice controller.

   Figure 10 shows the implementation (realization) of the transport
   slice 40 of Figure 6.  In this case the location of SF1 and SF2 has
   been explicitly decided by higher level logic.  In this case three
   transport slices 41, 42 and 43 will be created separately and
   eventually bind together to form a single transport slice 40 to meet
   the SLA that delay is lower than 30 ms.

Rokui, et al.              Expires May 5, 2020                 [Page 12]
Internet-Draft draft-nsdt-teas-transport-slice-definition  November 2019

                             | Create transport slice between ER1
                             | and ER2 with latency 30 [msec]
                             v
                    +------------------+              +-----------+
                    | Transport slice  |<------------>|    SF     |
                    |   controller     |              |  Manager  |
                    +------------------+              +-----------+
                             | Implementation transport slice 40
                             | between ER1 & ER2 traversing SF1 and SF2
                             | with SLA of latency 30 [msec]
                             V
        <----------------- TS 40 ------------------->
                +-----+
                | SF1 |
                + === +   .----.
                  # #    (      )--.
                  # #  (           )
                  # #  --' Network    '--.
    [ER1]=========   =========  ===================[ER2]
              `-------------- # # --------'
                              # #
                            + == +
                            | SF2 |
                            +-----+

    Legends
      ===== : Tunnels & Services

    Figure 9: Implementation (aka Realization) of Transport slice 40 of
                                 Figure-5

Rokui, et al.              Expires May 5, 2020                 [Page 13]
Internet-Draft draft-nsdt-teas-transport-slice-definition  November 2019

                          | Requirements on communication
                          | between ER1 and ER2
                          v
                 +-----------------+            +-----------+
                 |  Orchestrator   | <--------> | SF Manager|
                 +-----------------+            +-----------+
                          | Create transport slice between ER1 and SF1,
                          |        with latency 5 [msec]
                          | Create transport slice between SF1 and SF2,
                          |        with latency 20 [msec]
                          | Create transport slice between SF2 and ER2,
                          |        with latency 5 [msec]
                          v
                +-------------------+
                | Transport slice   |
                | manager/controller|
                +-------------------+
                   |      |     |         Realize TS 41 between ER and
                   |      |     |            SF1 with latency 5 msec
            +------+      |     +-------+ Realize TS 42 between SF1 and
            |             |             |    SF2 with latency  20 msec
            |             |             | Realize TS 43 between SF2 and
            |             |             |    ER2 with latency 5 msec
            v             v             v
       <--TS 41-->   <--TS 42-->   <--TS 43 -->
      <---------------- TS 40 ---------------->
                +-----+
              #=| SF1 |
              # +-----+ .----.
              #     #  (      )--.
              # .---#' Network    '--.
    [ER1]=====#(    #==========#       )#=====[ER2]
                `--------------#------' #
                               #        #
                             +-----+    #
                             | SF2 |====#
                             +-----+

    Legend
    === : Tunnels & Services

   Figure 10: Implementation (aka Realization) of Transport slice 40 of
                                 Figure-6

Rokui, et al.              Expires May 5, 2020                 [Page 14]
Internet-Draft draft-nsdt-teas-transport-slice-definition  November 2019

5.  Definition of SLA and Isolation levels

   TBD

6.  Informative References

   [TS.23.501-3GPP]
              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,
              <http://www.3gpp.org/ftp//Specs/
              archive/23_series/23.501/23501-g20.zip>.

Authors' Addresses

   Reza Rokui
   Nokia
   Canada

   Email: reza.rokui@nokia.com

   Shunsuke Homma
   NTT
   Japan

   Email: shunsuke.homma.fp@hco.ntt.co.jp

   Kiran Makhijani
   Futurewei
   USA

   Email: kiranm@futurewei.com

Rokui, et al.              Expires May 5, 2020                 [Page 15]