[Docs] [txt|pdf] [Tracker] [WG] [Email] [Diff1] [Diff2] [Nits]

Versions: (draft-tnbidt-ccamp-transport-nbi-use-cases) 00 01

CCAMP Working Group                                      I. Busi (Ed.)
Internet Draft                                                 Huawei
Intended status: Informational                                D. King
Expires: April 2018                              Lancaster University
                                                     October 09, 2017




    Transport Northbound Interface Applicability Statement and Use Cases
               draft-ietf-ccamp-transport-nbi-use-cases-00


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), its areas, and its working groups.  Note that
   other groups may also distribute working documents as Internet-
   Drafts.

   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."

   The list of current Internet-Drafts can be accessed at
   http://www.ietf.org/ietf/1id-abstracts.txt

   The list of Internet-Draft Shadow Directories can be accessed at
   http://www.ietf.org/shadow.html

   This Internet-Draft will expire on Aoril 10, 2018.

Copyright Notice

   Copyright (c) 2017 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
   (http://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.

Busi & King, et al.    Expires April 20, 2018                 [Page 1]


Internet-Draft         Transport NBI Use Cases            October 2017


Abstract

   Transport network domains, including Optical Transport Network (OTN)
   and Wavelength Division Multiplexing (WDM) networks, are typically
   deployed based on a single vendor or technology platforms. They are
   often managed using proprietary interfaces to dedicated Element
   Management Systems (EMS), Network Management Systems (NMS) and
   increasingly Software Defined Network (SDN) controllers.

   A well-defined open interface to each domain management system or
   controller is required for network operators to facilitate control
   automation and orchestrate end-to-end services across multi-domain
   networks. These functions may be enabled using standardized data
   models (e.g. YANG), and appropriate protocol (e.g., RESTCONF).

   This document describes the key use cases and requirements for
   transport network control and management. It reviews proposed and
   existing IETF transport network data models, their applicability,
   and highlights gaps and requirements.

Table of Contents

   1. Introduction ................................................3
      1.1. Scope of this document .................................4
   2. Terminology .................................................4
   3. Conventions used in this document............................4
      3.1. Topology and traffic flow processing ...................4
   4. Use Case 1: Single-domain with single-layer .................5
      4.1. Reference Network ......................................5
         4.1.1. Single Transport Domain - OTN Network .............5
      4.2. Topology Abstractions ..................................8
      4.3. Service Configuration ..................................9
         4.3.1. ODU Transit .......................................9
         4.3.2. EPL over ODU ......................................10
         4.3.3. Other OTN Client Services .........................10
         4.3.4. EVPL over ODU .....................................11
         4.3.5. EVPLAN and EVPTree Services .......................12
      4.4. Multi-functional Access Links ..........................13
      4.5. Protection Requirements ................................14
         4.5.1. Linear Protection .................................15
   5. Use Case 2: Single-domain with multi-layer ..................15
      5.1. Reference Network ......................................15
      5.2. Topology Abstractions ..................................16
      5.3. Service Configuration ..................................16
   6. Use Case 3: Multi-domain with single-layer ..................16
      6.1. Reference Network ......................................16
      6.2. Topology Abstractions ..................................19


Busi & King, et al.    Expires April 20, 2018                 [Page 2]


Internet-Draft         Transport NBI Use Cases            October 2017


      6.3. Service Configuration ..................................19
         6.3.1. ODU Transit .......................................20
         6.3.2. EPL over ODU ......................................20
         6.3.3. Other OTN Client Services .........................21
         6.3.4. EVPL over ODU .....................................21
         6.3.5. EVPLAN and EVPTree Services .......................21
      6.4. Multi-functional Access Links ..........................22
      6.5. Protection Scenarios ...................................22
         6.5.1. Linear Protection (end-to-end) ....................23
         6.5.2. Segmented Protection ..............................23
   7. Use Case 4: Multi-domain and multi-layer ....................24
      7.1. Reference Network ......................................24
      7.2. Topology Abstractions ..................................25
      7.3. Service Configuration ..................................25
   8. Security Considerations .....................................25
   9. IANA Considerations .........................................26
   10. References .................................................26
      10.1. Normative References ..................................26
      10.2. Informative References ................................26
   11. Acknowledgments ............................................27

1. Introduction

   Transport of packet services are critical for a wide-range of
   applications and services, including: data center and LAN
   interconnects, Internet service backhauling, mobile backhaul and
   enterprise Carrier Ethernet Services. These services are typically
   setup using stovepipe NMS and EMS platforms, often requiring
   propriety management platforms and legacy management interfaces. A
   clear goal of operators will be to automate setup of transport
   services across multiple transport technology domains.

   A common open interface (API) to each domain controller and or
   management system is pre-requisite for network operators to control
   multi-vendor and multi-domain networks and enable also service
   provisioning coordination/automation. This can be achieved by using
   standardized YANG models, used together with an appropriate protocol
   (e.g., [RESTCONF]).

   This document describes key use cases for analyzing the
   applicability of the existing models defined by the IETF for
   transport networks. The intention of this document is to become an
   applicability statement that provides detailed descriptions of how
   IETF transport models are applied to solve the described use cases
   and requirements.




Busi & King, et al.    Expires April 20, 2018                 [Page 3]


Internet-Draft         Transport NBI Use Cases            October 2017


1.1. Scope of this document

   This document assumes a reference architecture, including
   interfaces, based on the Abstraction and Control of Traffic-
   Engineered Networks (ACTN), defined in [ACTN-Frame]

   The focus of this document is on the MPI (interface between the
   Multi Domain Service Coordinator (MDSC) and a Physical Network
   Controller (PNC), controlling a transport network domain).

   The relationship between the current IETF YANG models and the type
   of ACTN interfaces can be found in [ACTN-YANG].

   The ONF Technical Recommendations for Functional Requirements for
   the transport API in [ONF TR-527] and the ONF transport API multi-
   layer examples in [ONF GitHub] have been considered as an input for
   this work.

   Considerations about the CMI (interface between the Customer Network
   Controller (CNC) and the MDSC) are outside the scope of this
   document.

2. Terminology

   E-LINE: Ethernet Line

   EPL: Ethernet Private Line

   EVPL: Ethernet Virtual Private Line

   OTH: Optical Network Hierarchy

   OTN: Optical Transport Network

3. Conventions used in this document

3.1. Topology and traffic flow processing

   The traffic flow between different nodes is specified as an ordered
   list of nodes, separated with commas, indicating within the brackets
   the processing within each node:

      <node> (<processing>){, <node> (<processing>)}

   The order represents the order of traffic flow being forwarded
   through the network.



Busi & King, et al.    Expires April 20, 2018                 [Page 4]


Internet-Draft         Transport NBI Use Cases            October 2017


   The processing can be either an adaptation of a client layer into a
   server layer "(client -> server)" or switching at a given layer
   "([switching])". Multi-layer switching is indicated by two layer
   switching with client/server adaptation: "([client] -> [server])".

   For example, the following traffic flow:

      C-R1 (|PKT| -> ODU2), S3 (|ODU2|), S5 (|ODU2|), S6 (|ODU2|),
      C-R3 (ODU2 -> |PKT|)

   Node C-R1 is switching at the packet (PKT) layer and mapping packets
   into a ODU2 before transmission to node S3. Nodes S3, S5 and S6 are
   switching at the ODU2 layer: S3 sends the ODU2 traffic to S5 which
   then sends it to S6 which finally sends to C-R3. Node C-R3
   terminates the ODU2 from S6 before switching at the packet (PKT)
   layer.

   The paths of working and protection transport entities are specified
   as an ordered list of nodes, separated with commas:

      <node> {, <node>}

   The order represents the order of traffic flow being forwarded
   through the network in the forward direction. In case of
   bidirectional paths, the forward and backward directions are
   selected arbitrarily, but the convention is consistent between
   working/protection path pairs as well as across multiple domains.

4. Use Case 1: Single-domain with single-layer

4.1. Reference Network

   The current considerations discussed in this document are based on
   the following reference networks:

        - single transport domain: OTN network

4.1.1. Single Transport Domain - OTN Network

   As shown in Figure 1 the network physical topology composed of a
   single-domain transport network providing transport services to an
   IP network through five access links.







Busi & King, et al.    Expires April 20, 2018                 [Page 5]


Internet-Draft         Transport NBI Use Cases            October 2017


           ................................................
           :                 IP domain                    :
           :        ..............................        :
           :        :  ........................  :        :
           :        :  :                      :  :        :
           :        :  :      S1 -------- S2 ------ C-R4  :
           :        :  :     /             |  :  :        :
           :        :  :    /              |  :  :        :
           :  C-R1 ------ S3 ----- S4      |  :  :        :
           :        :  :    \        \     |  :  :        :
           :        :  :     \        \    |  :  :        :
           :        :  :      S5       \   |  :  :        :
           :  C-R2 -----+    /  \       \  |  :  :        :
           :        :  : \  /    \       \ |  :  :        :
           :        :  :  S6 ---- S7 ---- S8 ------ C-R5  :
           :        :  : /                    :  :        :
           :  C-R3 -----+                     :  :        :
           :        :  :   Transport domain   :  :        :
           :        :  :                      :  :        :
           :........:  :......................:  :........:
                  Figure 1 Reference network for Use Case 1

   The IP and transport (OTN) domains are respectively composed by five
   routers C-R1 to C-R5 and by eight ODU switches S1 to S8. The
   transport domain acts as a transit network providing connectivity
   for IP layer services.

   The behavior of the transport domain is the same whether the
   ingress or egress service nodes in the IP domain are only attached
   to the transport domain, or if there are other routers in between
   the ingress or egress nodes of the IP domain not also attached to
   the transport domain. In other words, the behavior of the transport
   network does not depend on whether C-R1, C-R2, ..., C-R5 are PE or P
   routers for the IP services.

   The transport domain control plane architecture follows the ACTN
   architecture and framework document [ACTN-Frame], and functional
   components:

   o Customer Network Controller (CNC) act as a client with respect to
      the Multi-Domain Service Coordinator (MDSC) via the CNC-MDSC
      Interface (CMI);







Busi & King, et al.    Expires April 20, 2018                 [Page 6]


Internet-Draft         Transport NBI Use Cases            October 2017


   o MDSC is connected to a plurality of Physical Network Controllers
      (PNCs), one for each domain, via a MDSC-PNC Interface (MPI). Each
      PNC is responsible only for the control of its domain and the
      MDSC is the only entity capable of multi-domain functionalities
      as well as of managing the inter-domain links;

   The ACTN framework facilitates the detachment of the network and
   service control from the underlying technology and help the customer
   express the network as desired by business needs. Therefore, care
   must be taken to keep minimal dependency on the CMI (or no
   dependency at all) with respect to the network domain technologies.
   The MPI instead requires some specialization according to the domain
   technology.


                                 +-----+
                                 | CNC |
                                 +-----+
                                    |
                                    |CMI I/F
                                    |
                         +-----------------------+
                         |         MDSC          |
                         +-----------------------+
                                    |
                                    |MPI I/F
                                    |
                                +-------+
                                |  PNC  |
                                +-------+
                                    |
                                  -----
                                (       )
                               (   OTN   )
                              ( Physical  )
                               ( Network )
                                (       )
                                  -----

                Figure 2 Controlling Hierarchy for Use Case 1

   Once the service request is processed by the MDSC the mapping of the
   client IP traffic between the routers (across the transport network)
   is made in the IP routers only and is not controlled by the
   transport PNC, and therefore transparent to the transport nodes.




Busi & King, et al.    Expires April 20, 2018                 [Page 7]


Internet-Draft         Transport NBI Use Cases            October 2017


4.2. Topology Abstractions

   Abstraction provides a selective method for representing
   connectivity information within a domain. There are multiple methods
   to abstract a network topology. This document assumes the
   abstraction method defined in [RFC7926]:

     "Abstraction is the process of applying policy to the available TE
     information within a domain, to produce selective information that
     represents the potential ability to connect across the domain.
     Thus, abstraction does not necessarily offer all possible
     connectivity options, but presents a general view of potential
     connectivity according to the policies that determine how the
     domain's administrator wants to allow the domain resources to be
     used."

   [TE-Topo] describes a YANG base model for TE topology without any
   technology specific parameters. Moreover, it defines how to abstract
   for TE-network topologies.

   [ACTN-Frame] provides the context of topology abstraction in the
   ACTN architecture and discusses a few alternatives for the
   abstraction methods for both packet and optical networks. This is an
   important consideration since the choice of the abstraction method
   impacts protocol design and the information it carries.  According
   to [ACTN-Frame], there are three types of topology:

   o White topology: This is a case where the Physical Network
      Controller (PNC) provides the actual network topology to the
      multi-domain Service Coordinator (MDSC) without any hiding or
      filtering. In this case, the MDSC has the full knowledge of the
      underlying network topology;

   o Black topology: The entire domain network is abstracted as a
      single virtual node with the access/egress links without
      disclosing any node internal connectivity information;

   o Grey topology: This abstraction level is between black topology
      and white topology from a granularity point of view. This is
      abstraction of TE tunnels for all pairs of border nodes. We may
      further differentiate from a perspective of how to abstract
      internal TE resources between the pairs of border nodes:

        - Grey topology type A: border nodes with a TE links between
          them in a full mesh fashion;




Busi & King, et al.    Expires April 20, 2018                 [Page 8]


Internet-Draft         Transport NBI Use Cases            October 2017


        - Grey topology type B: border nodes with some internal
          abstracted nodes and abstracted links.

   For single-domain with single-layer use-case, the white topology may
   be disseminated from the PNC to the MDSC in most cases. There may be
   some exception to this in the case where the underlay network may
   have complex optical parameters, which do not warrant the
   distribution of such details to the MDSC. In such case, the topology
   disseminated from the PNC to the MDSC may not have the entire TE
   information but a streamlined TE information. This case would incur
   another action from the MDSC's standpoint when provisioning a path.
   The MDSC may make a path compute request to the PNC to verify the
   feasibility of the estimated path before making the final
   provisioning request to the PNC, as outlined in [Path-Compute].

   Topology abstraction for the CMI is for further study (to be
   addressed in future revisions of this document).

4.3. Service Configuration

   In the following use cases, the Multi Domain Service Coordinator
   (MDSC) needs to be capable to request service connectivity from the
   transport Physical Network Controller (PNC) to support IP routers
   connectivity. The type of services could depend of the type of
   physical links (e.g. OTN link, ETH link or SDH link) between the
   routers and transport network.

   As described in section 4.1.1, the control of different adaptations
   inside IP routers, C-Ri (PKT -> foo) and C-Rj (foo -> PKT), are
   assumed to be performed by means that are not under the control of,
   and not visible to, transport PNC. Therefore, these mechanisms are
   outside the scope of this document.

4.3.1. ODU Transit

   This use case assumes that the physical links interconnecting the IP
   routers and the transport network are OTN links. The
   physical/optical interconnection below the ODU layer is supposed to
   be pre-configured and not exposed at the MPI to the MDSC.

   To setup a 10Gb IP link between C-R1 to C-R3, an ODU2 end-to-end
   data plane connection needs to be created between C-R1 and C-R3,
   crossing transport nodes S3, S5, and S6.

   The traffic flow between C-R1 and C-R3 can be summarized as:




Busi & King, et al.    Expires April 20, 2018                 [Page 9]


Internet-Draft         Transport NBI Use Cases            October 2017


      C-R1 (|PKT| -> ODU2), S3 (|ODU2|), S5 (|ODU2|), S6 (|ODU2|),
      C-R3 (ODU2 -> |PKT|)

   The MDSC should be capable via the MPI to request the setup of an
   ODU2 transit service with enough information that enable the
   transport PNC to instantiate and control the ODU2 data plane
   connection segment through nodes S3, S5, S6.

4.3.2. EPL over ODU

   This use case assumes that the physical links interconnecting the IP
   routers and the transport network are Ethernet links.

   In order to setup a 10Gb IP link between C-R1 to C-R3, an EPL
   service needs to be created between C-R1 and C-R3, supported by an
   ODU2 end-to-end connection between S3 and S6, crossing transport
   node S5.

   The traffic flow between C-R1 and C-R3 can be summarized as:

      C-R1 (|PKT| -> ETH), S3 (ETH -> |ODU2|), S5 (|ODU2|),
      S6 (|ODU2| -> ETH), C-R3 (ETH-> |PKT|)

   The MDSC should be capable via the MPI to request the setup of an
   EPL service with enough information that can permit the transport
   PNC to instantiate and control the ODU2 end-to-end data plane
   connection through nodes S3, S5, S6, as well as the adaptation
   functions inside S3 and S6: S3&S6 (ETH -> ODU2) and S9&S6 (ODU2 ->
   ETH).

4.3.3. Other OTN Client Services

   [ITU-T G.709-2016] defines mappings of different client layers into
   ODU. Most of them are used to provide Private Line services over
   an OTN transport network supporting a variety of types of physical
   access links (e.g., Ethernet, SDH STM-N, Fibre Channel, InfiniBand,
   etc.).

   This use case assumes that the physical links interconnecting the IP
   routers and the transport network are any one of these possible
   options.

   In order to setup a 10Gb IP link between C-R1 to C-R3 using, for
   example STM-64 physical links between the IP routers and the
   transport network, an STM-64 Private Line service needs to be
   created between C-R1 and C-R3, supported by an ODU2 end-to-end data
   plane connection between S3 and S6, crossing transport node S5.


Busi & King, et al.    Expires April 20, 2018                [Page 10]


Internet-Draft         Transport NBI Use Cases            October 2017


   The traffic flow between C-R1 and C-R3 can be summarized as:

      C-R1 (|PKT| -> STM-64), S3 (STM-64 -> |ODU2|), S5 (|ODU2|),
      S6 (|ODU2| -> STM-64), C-R3 (STM-64 -> |PKT|)

   The MDSC should be capable via the MPI to request the setup of an
   STM-64 Private Line service with enough information that can permit
   the transport PNC to instantiate and control the ODU2 end-to-end
   connection through nodes S3, S5, S6, as well as the adaptation
   functions inside S3 and S6: S3&S6 (STM-64 -> ODU2) and S9&S3 (STM-64
   -> PKT).

4.3.4. EVPL over ODU

   This use case assumes that the physical links interconnecting the IP
   routers and the transport network are Ethernet links and that
   different Ethernet services (e.g, EVPL) can share the same physical
   link using different VLANs.

   In order to setup two 1Gb IP links between C-R1 to C-R3 and between
   C-R1 and C-R4, two EVPL services need to be created, supported by
   two ODU0 end-to-end connections respectively between S3 and S6,
   crossing transport node S5, and between S3 and S2, crossing
   transport node S1.

   Since the two EVPL services are sharing the same Ethernet physical
   link between C-R1 and S3, different VLAN IDs are associated with
   different EVPL services: for example VLAN IDs 10 and 20
   respectively.

   The traffic flow between C-R1 and C-R3 can be summarized as:

      C-R1 (|PKT| -> VLAN), S3 (VLAN -> |ODU0|), S5 (|ODU0|),
      S6 (|ODU0| -> VLAN), C-R3 (VLAN -> |PKT|)

   The traffic flow between C-R1 and C-R4 can be summarized as:

      C-R1 (|PKT| -> VLAN), S3 (VLAN -> |ODU0|), S1 (|ODU0|),
      S2 (|ODU0| -> VLAN), C-R4 (VLAN -> |PKT|)

   The MDSC should be capable via the MPI to request the setup of these
   EVPL services with enough information that can permit the transport
   PNC to instantiate and control the ODU0 end-to-end data plane
   connections as well as the adaptation functions on the boundary
   nodes: S3&S2&S6 (VLAN -> ODU0) and S3&S2&S6 (ODU0 -> VLAN).




Busi & King, et al.    Expires April 20, 2018                [Page 11]


Internet-Draft         Transport NBI Use Cases            October 201


4.3.5. EVPLAN and EVPTree Services

   This use case assumes that the physical links interconnecting the IP
   routers and the transport network are Ethernet links and that
   different Ethernet services (e.g, EVPL, EVPLAN and EVPTree) can
   share the same physical link using different VLANs.

   Note - it is assumed that EPLAN and EPTree services can be supported
   by configuring EVPLAN and EVPTree with port mapping.

   In order to setup an IP subnet between C-R1, C-R2, C-R3 and C-R4, an
   EVPLAN/EVPTree service needs to be created, supported by two ODUflex
   end-to-end connections respectively between S3 and S6, crossing
   transport node S5, and between S3 and S2, crossing transport node
   S1.

   In order to support this EVPLAN/EVPTree service, some Ethernet
   Bridging capabilities are required on some nodes at the edge of the
   transport network: for example Ethernet Bridging capabilities can be
   configured in nodes S3 and S6 but not in node S2.

   Since this EVPLAN/EVPTree service can share the same Ethernet
   physical links between IP routers and transport nodes (e.g., with
   the EVPL services described in section 4.3.4), a different VLAN ID
   (e.g., 30) can be associated with this EVPLAN/EVPTree service.

   In order to support an EVPTree service instead of an EVPLAN,
   additional configuration of the Ethernet Bridging capabilities on
   the nodes at the edge of the transport network is required.

   The MAC bridging function in node S3 is needed to select, based on
   the MAC Destination Address, whether the Ethernet frames form C-R1
   should be sent to the ODUflex terminating on node S6 or to the other
   ODUflex terminating on node S2.

   The MAC bridging function in node S6 is needed to select, based on
   the MAC Destination Address, whether the Ethernet frames received
   from the ODUflex should be set to C-R2 or C-R3, as well as whether
   the Ethernet frames received from C-R2 (or C-R3) should be sent to
   C-R3 (or C-R2) or to the ODUflex.

   For example, the traffic flow between C-R1 and C-R3 can be
   summarized as:

      C-R1 (|PKT| -> VLAN), S3 (VLAN -> |MAC| -> |ODUflex|),
      S5 (|ODUflex|), S6 (|ODUflex| -> |MAC| -> VLAN),
      C-R3 (VLAN -> |PKT|)


Busi & King, et al.    Expires April 20, 2018                [Page 12]


Internet-Draft         Transport NBI Use Cases            October 2017


   The MAC bridging function in node S3 is also needed to select, based
   on the MAC Destination Address, whether the Ethernet frames one
   ODUflex should be sent to C-R1 or to the other ODUflex.

   For example, the traffic flow between C-R3 and C-R4 can be
   summarized as:

      C-R3 (|PKT| -> VLAN), S6 (VLAN -> |MAC| -> |ODUflex|),
      S5 (|ODUflex|), S3 (|ODUflex| -> |MAC| -> |ODUflex|),
      S1 (|ODUflex|), S2 (|ODUflex| -> VLAN), C-R4 (VLAN -> |PKT|)

   In node S2 there is no need for any MAC bridging function since all
   the Ethernet frames received from C-R4 should be sent to the ODUflex
   toward S3 and viceversa.

   The traffic flow between C-R1 and C-R4 can be summarized as:

      C-R1 (|PKT| -> VLAN), S3 (VLAN -> |MAC| -> |ODUflex|),
      S1 (|ODUflex|), S2 (|ODUflex| -> VLAN), C-R4 (VLAN -> |PKT|)

   The MDSC should be capable via the MPI to request the setup of this
   EVPLAN/EVPTree services with enough information that can permit the
   transport PNC to instantiate and control the ODUflex end-to-end data
   plane connections as well as the Ethernet Bridging and adaptation
   functions on the boundary nodes: S3&S6 (VLAN -> MAC -> ODU2), S3&S6
   (ODU2 -> ETH -> VLAN), S2 (VLAN -> ODU2) and S2 (ODU2 -> VLAN).

4.4. Multi-functional Access Links

   This use case assumes that some physical links interconnecting the
   IP routers and the transport network can be configured in different
   modes, e.g., as OTU2 or STM-64 or 10GE.

   This configuration can be done a-priori by means outside the scope
   of this document. In this case, these links will appear at the MPI
   either as an ODU Link or as an STM-64 Link or as a 10GE Link
   (depending on the a-priori configuration) and will be controlled at
   the MPI as discussed in section 4.3.

   It is also possible not to configure these links a-priori and give
   the control to the MPI to decide, based on the service
   configuration, how to configure it.

   For example, if the physical link between C-R1 and S3 is a multi-
   functional access link while the physical links between C-R3 and S6
   and between C-R4 and S2 are STM-64 and 10GE physical links
   respectively, it is possible at the MPI to configure either an STM-


Busi & King, et al.    Expires April  20, 2018                [Page 13]


Internet-Draft         Transport NBI Use Cases            October 2017


   64 Private Line service between C-R1 and C-R3 or an EPL service
   between C-R1 and C-R4.

   The traffic flow between C-R1 and C-R3 can be summarized as:

      C-R1 (|PKT| -> STM-64), S3 (STM-64 -> |ODU2|), S5 (|ODU2|),
      S6 (|ODU2| -> STM-64), C-R3 (STM-64 -> |PKT|)

   The traffic flow between C-R1 and C-R4 can be summarized as:

      C-R1 (|PKT| -> ETH), S3 (ETH -> |ODU2|), S1 (|ODU2|),
      S2 (|ODU2| -> ETH), C-R4 (ETH-> |PKT|)

   The MDSC should be capable via the MPI to request the setup of
   either service with enough information that can permit the transport
   PNC to instantiate and control the ODU2 end-to-end data plane
   connection as well as the adaptation functions inside S3 and S2 or
   S6.

4.5. Protection Requirements

   Protection switching provides a pre-allocated survivability
   mechanism, typically provided via linear protection methods and
   would be configured to operate as 1+1 unidirectional (the most
   common OTN protection method), 1+1 bidirectional or 1:n
   bidirectional. This ensures fast and simple service survivability.

   The MDSC needs to be capable to request the transport PNC to
   configure protection when requesting the setup of the connectivity
   services described in section 4.3.

   Since in this use case it is assumed that switching within the
   transport network domain is performed only in one layer, also
   protection switching within the transport network domain can only be
   provided at the OTN ODU layer, for all the services defined in
   section 4.3.

   It may be necessary to consider not only protection, but also
   restoration functions in the future. Restoration methods would
   provide capability to reroute and restore connectivity traffic
   around network faults, without the network penalty imposed with
   dedicated 1+1 protection schemes.







Busi & King, et al.    Expires April  20, 2018                [Page 14]


Internet-Draft         Transport NBI Use Cases            October 2017


4.5.1. Linear Protection

   It is possible to protect any service defined in section 4.3 from
   failures within the OTN transport domain by configuring OTN linear
   protection in the data plane between node S3 and node S6.

   It is assumed that the OTN linear protection is configured to with
   1+1 unidirectional protection switching type, as defined in [ITU-T
   G.808.1-2014] and [ITU-T G.873.1-2014], as well as in [RFC4427].

   In these scenarios, a working transport entity and a protection
   transport entity, as defined in [ITU-T G.808.1-2014], (or a working
   LSP and a protection LSP, as defined in [RFC4427]) should be
   configured in the data plane, for example:

     Working transport entity: S3, S5, S6

     Protection transport entity: S3, S4, S8, S7, S6

   The Transport PNC should be capable to report to the MDSC which is
   the active transport entity, as defined in [ITU-T G.808.1-2014], in
   the data plane.

   Given the fast dynamic of protection switching operations in the
   data plane (50ms recovery time), this reporting is not expected to
   be in real-time.

   It is also worth noting that with unidirectional protection
   switching, e.g., 1+1 unidirectional protection switching, the active
   transport entity may be different in the two directions.

5. Use Case 2: Single-domain with multi-layer

5.1. Reference Network

   The current considerations discussed in this document are based on
   the following reference network:

        - single transport domain: OTN and OCh multi-layer network

   In this use case, the same reference network shown in Figure 1 is
   considered. The only difference is that all the transport nodes are
   capable to switch in the ODU as well as in the OCh layer.

   All the physical links within the transport network are therefore
   assumed to be OCh links. Therefore, with the exception of the access



Busi & King, et al.    Expires April  20, 2018                [Page 15]


Internet-Draft         Transport NBI Use Cases            October 2017


   links, no ODU internal link exists before an OCh end-to-end data
   plane connection is created within the network.

   The controlling hierarchy is the same as described in Figure 2.

   The interface within the scope of this document is the Transport MPI
   which should be capable to control both the OTN and OCh layers.

5.2. Topology Abstractions

   A grey topology type B abstraction is assumed: abstract nodes and
   links exposed at the MPI corresponds 1:1 with the physical nodes and
   links controlled by the PNC but the PNC abstracts/hides at least
   some optical parameters to be used within the OCh layer.

5.3. Service Configuration

   The same service scenarios, as described in section 4.3, are also
   applicable to these use cases with the only difference that end-to-
   end OCh data plane connections will need to be setup before ODU data
   plane connections.

6. Use Case 3: Multi-domain with single-layer

6.1. Reference Network

   In this section we focus on a multi-domain reference network with
   homogeneous technologies:

        - multiple transport domains: OTN networks

   Figure 3 shows the network physical topology composed of three
   transport network domains providing transport services to an IP
   customer network through eight access links:














Busi & King, et al.    Expires April  20, 2018                [Page 16]


Internet-Draft         Transport NBI Use Cases            October 2017


                ........................
   ..........   :                      :
   :        :   :   Network domain 1   :   .............
   :Customer:   :                      :   :           :
   :domain 1:   :     S1 -------+      :   :  Network  :
   :        :   :    /           \     :   :  domain 3 :   ..........
   :  C-R1 ------- S3 ----- S4    \    :   :           :   :        :
   :        :   :    \        \    S2 --------+        :   :Customer:
   :        :   :     \        \    |  :   :   \       :   :domain 3:
   :        :   :      S5       \   |  :   :    \      :   :        :
   :  C-R2 ------+    /  \       \  |  :   :    S31 --------- C-R7  :
   :        :   : \  /    \       \ |  :   :   /   \   :   :        :
   :        :   :  S6 ---- S7 ---- S8 ------ S32   S33 ------ C-R8  :
   :        :   : /        |       |   :   : / \   /   :   :........:
   :  C-R3 ------+         |       |   :   :/   S34    :
   :        :   :..........|.......|...:   /    /      :
   :........:              |       |      /:.../.......:
                           |       |     /    /
                ...........|.......|..../..../...
                :          |       |   /    /   :    ..........
                : Network  |       |  /    /    :    :        :
                : domain 2 |       | /    /     :    :Customer:
                :         S11 ---- S12   /      :    :domain 2:
                :        /          | \ /       :    :        :
                :     S13     S14   | S15 ------------- C-R4  :
                :     |  \   /   \  |    \      :    :        :
                :     |   S16     \ |     \     :    :        :
                :     |  /         S17 -- S18 --------- C-R5  :
                :     | /             \   /     :    :        :
                :    S19 ---- S20 ---- S21 ------------ C-R6  :
                :                               :    :        :
                :...............................:    :........:

                  Figure 3 Reference network for Use Case 3

   It is worth noting that the network domain 1 is identical to the
   transport domain shown in Figure 1.











Busi & King, et al.    Expires April  20, 2018                [Page 17]


Internet-Draft         Transport NBI Use Cases            October 2017


                      --------------
                     |    Client    |
                     |  Controller  |
                      --------------
                            |
        ....................|.......................
                            |
                     ----------------
                    |                |
                    |      MDSC      |
                    |                |
                     ----------------
                       /   |    \
                      /    |     \
       ............../.....|......\................
                    /      |       \
                   /   ----------   \
                  /   |   PNC2   |   \
                 /     ----------     \
        ----------         |           \
       |   PNC1   |      -----          \
        ----------     (       )      ----------
            |         (         )    |   PNC3   |
          -----      (  Network  )    ----------
        (       )    (  Domain 2 )        |
       (         )    (         )       -----
      (  Network  )    (       )      (       )
      (  Domain 1 )      -----       (         )
       (         )                  (  Network  )
        (       )                   (  Domain 3 )
          -----                      (         )
                                      (       )
                                        -----

                Figure 4 Controlling Hierarchy for Use Case 3

   In this section we address the case where the CNC controls the
   customer IP network and requests transport connectivity among IP
   routers, via the CMI, to an MDSC which coordinates, via three MPIs,
   the control of a multi-domain transport network through three PNCs.

   The interfaces within the scope of this document are the three MPIs
   while the interface between the CNC and the IP routers is out of its
   scope and considerations about the CMI are outside the scope of this
   document.




Busi & King, et al.    Expires April  20, 2018                [Page 18]


Internet-Draft         Transport NBI Use Cases            October 2017


6.2. Topology Abstractions

   Each PNC should provide the MDSC a topology abstraction of the
   domain's network topology.

   Each PNC provides topology abstraction of its own domain topology
   independently from each other and therefore it is possible that
   different PNCs provide different types of topology abstractions.

   As an example, we can assume that:

   o PNC1 provides a white topology abstraction (likewise use case 1
      described in section 4.2)

   o PNC2 provides a type A grey topology abstraction

   o PNC3 provides a type B grey topology abstraction, with two
      abstract nodes (AN31 and AN32). They abstract respectively nodes
      S31+S33 and nodes S32+S34. At the MPI, only the abstract nodes
      should be reported: the mapping between the abstract nodes (AN31
      and AN32) and the physical nodes (S31, S32, S33 and S34) should
      be done internally by the PNC.

   The MDSC should be capable to glue together these different abstract
   topologies to build its own view of the multi-domain network
   topology. This might require proper administrative configuration or
   other mechanisms (to be defined/analysed).

6.3. Service Configuration

   In the following use cases, it is assumed that the CNC is capable to
   request service connectivity from the MDSC to support IP routers
   connectivity.

   The same service scenarios, as described in section 4.3, are also
   application to this use cases with the only difference that the two
   IP routers to be interconnected are attached to transport nodes
   which belong to different PNCs domains and are under the control of
   the CNC.

   Likewise, the service scenarios in section 4.3, the type of services
   could depend of the type of physical links (e.g. OTN link, ETH link
   or SDH link) between the customer's routers and the multi-domain
   transport network and the configuration of the different adaptations
   inside IP routers is performed by means that are outside the scope
   of this document because not under control of and not visible to the
   MDSC nor to the PNCs. It is assumed that the CNC is capable to


Busi & King, et al.    Expires April  20, 2018                [Page 19]


Internet-Draft         Transport NBI Use Cases            October 2017


   request the proper configuration of the different adaptation
   functions inside the customer's IP routers, by means which are
   outside the scope of this document.

   It is also assumed that the CNC is capable via the CMI to request
   the MDSC the setup of these services with enough information that
   enable the MDSC to coordinate the different PNCs to instantiate and
   control the ODU2 data plane connection through nodes S3, S1, S2,
   S31, S33, S34, S15 and S18, as well as the adaptation functions
   inside nodes S3 and S18, when needed.

   As described in section 6.2, the MDSC should have its own view of
   the end-to-end network topology and use it for its own path
   computation to understand that it needs to coordinate with PNC1,
   PNC2 and PNC3 the setup and control of a multi-domain ODU2 data
   plane connection.

6.3.1. ODU Transit

   In order to setup a 10Gb IP link between C-R1 and C-R5, an ODU2 end-
   to-end data plane connection needs be created between C-R1 and C-R5,
   crossing transport nodes S3, S1, S2, S31, S33, S34, S15 and S18
   which belong to different PNC domains.

   The traffic flow between C-R1 and C-R5 can be summarized as:

      C-R1 (|PKT| -> ODU2), S3 (|ODU2|), S1 (|ODU2|), S2 (|ODU2|),
      S31 (|ODU2|), S33 (|ODU2|), S34 (|ODU2|),
      S15 (|ODU2|), S18 (|ODU2|), C-R5 (ODU2 -> |PKT|)

6.3.2. EPL over ODU

   In order to setup a 10Gb IP link between C-R1 and C-R5, an EPL
   service needs to be created between C-R1 and C-R5, supported by an
   ODU2 end-to-end data plane connection between transport nodes S3 and
   S18, crossing transport nodes S1, S2, S31, S33, S34 and S15 which
   belong to different PNC domains.

   The traffic flow between C-R1 and C-R5 can be summarized as:

      C-R1 (|PKT| -> ETH), S3 (ETH -> |ODU2|), S1 (|ODU2|),
      S2 (|ODU2|), S31 (|ODU2|), S33 (|ODU2|), S34 (|ODU2|),
      S15 (|ODU2|), S18 (|ODU2| -> ETH), C-R5 (ETH -> |PKT|)






Busi & King, et al.    Expires April  20, 2018                [Page 20]


Internet-Draft         Transport NBI Use Cases            October 2017


6.3.3. Other OTN Client Services

   In order to setup a 10Gb IP link between C-R1 and C-R5 using, for
   example SDH physical links between the IP routers and the transport
   network, an STM-64 Private Line service needs to be created between
   C-R1 and C-R5, supported by ODU2 end-to-end data plane connection
   between transport nodes S3 and S18, crossing transport nodes S1, S2,
   S31, S33, S34 and S15 which belong to different PNC domains.

   The traffic flow between C-R1 and C-R5 can be summarized as:

      C-R1 (|PKT| -> STM-64), S3 (STM-64 -> |ODU2|), S1 (|ODU2|),
      S2 (|ODU2|), S31 (|ODU2|), S33 (|ODU2|), S34 (|ODU2|),
      S15 (|ODU2|), S18 (|ODU2| -> STM-64), C-R5 (STM-64 -> |PKT|)

6.3.4. EVPL over ODU

   In order to setup two 1Gb IP links between C-R1 to C-R3 and between
   C-R1 and C-R5, two EVPL services need to be created, supported by
   two ODU0 end-to-end connections respectively between S3 and S6,
   crossing transport node S5, and between S3 and S18, crossing
   transport nodes S1, S2, S31, S33, S34 and S15 which belong to
   different PNC domains.

   The VLAN configuration on the access links is the same as described
   in section 4.3.4.

   The traffic flow between C-R1 and C-R3 is the same as described in
   section 4.3.4.

   The traffic flow between C-R1 and C-R5 can be summarized as:

      C-R1 (|PKT| -> VLAN), S3 (VLAN -> |ODU2|), S1 (|ODU2|),
      S2 (|ODU2|), S31 (|ODU2|), S33 (|ODU2|), S34 (|ODU2|),
      S15 (|ODU2|), S18 (|ODU2| -> VLAN), C-R5 (VLAN -> |PKT|)

6.3.5. EVPLAN and EVPTree Services

   In order to setup an IP subnet between C-R1, C-R2, C-R3 and C-R7, an
   EVPLAN/EVPTree service needs to be created, supported by two ODUflex
   end-to-end connections respectively between S3 and S6, crossing
   transport node S5, and between S3 and S18, crossing transport nodes
   S1, S2, S31, S33, S34 and S15 which belong to different PNC domains.

   The VLAN configuration on the access links is the same as described
   in section 4.3.5.



Busi & King, et al.    Expires April  20, 2018                [Page 21]


Internet-Draft         Transport NBI Use Cases            October 2017


   The configuration of the Ethernet Bridging capabilities on nodes S3
   and S6 is the same as described in section 4.3.5 while the
   configuration on node S18 similar to the configuration of node S2
   described in section 4.3.5.

   The traffic flow between C-R1 and C-R3 is the same as described in
   section 4.3.5.

   The traffic flow between C-R1 and C-R5 can be summarized as:

      C-R1 (|PKT| -> VLAN), S3 (VLAN -> |MAC| -> |ODUflex|),
      S1 (|ODUflex|), S2 (|ODUflex|), S31 (|ODUflex|),
      S33 (|ODUflex|), S34 (|ODUflex|),
      S15 (|ODUflex|), S18 (|ODUflex| -> VLAN), C-R5 (VLAN -> |PKT|)

6.4. Multi-functional Access Links

   The same considerations of section 4.4 apply with the only
   difference that the ODU data plane connections could be setup across
   multiple PNC domains.

   For example, if the physical link between C-R1 and S3 is a multi-
   functional access link while the physical links between C-R7 and S31
   and between C-R5 and S18 are STM-64 and 10GE physical links
   respectively, it is possible to configure either an STM-64 Private
   Line service between C-R1 and C-R7 or an EPL service between C-R1
   and C-R5.

   The traffic flow between C-R1 and C-R7 can be summarized as:

      C-R1 (|PKT| -> STM-64), S3 (STM-64 -> |ODU2|), S1 (|ODU2|),
      S2 (|ODU2|), S31 (|ODU2| -> STM-64), C-R3 (STM-64 -> |PKT|)

   The traffic flow between C-R1 and C-R5 can be summarized as:

      C-R1 (|PKT| -> ETH), S3 (ETH -> |ODU2|), S1 (|ODU2|),
      S2 (|ODU2|), S31 (|ODU2|), S33 (|ODU2|), S34 (|ODU2|),
      S15 (|ODU2|), S18 (|ODU2| -> ETH), C-R5 (ETH -> |PKT|)

6.5. Protection Scenarios

   The MDSC needs to be capable to coordinate different PNCs to
   configure protection switching when requesting the setup of the
   connectivity services described in section 6.3.

   Since in this use case it is assumed that switching within the
   transport network domain is performed only in one layer, also


Busi & King, et al.    Expires April  20, 2018                [Page 22]


Internet-Draft         Transport NBI Use Cases            October 2017


   protection switching within the transport network domain can only be
   provided at the OTN ODU layer, for all the services defined in
   section 6.3.

6.5.1. Linear Protection (end-to-end)

   In order to protect any service defined in section 6.3 from failures
   within the OTN multi-domain transport network, the MDSC should be
   capable to coordinate different PNCs to configure and control OTN
   linear protection in the data plane between nodes S3 and node S18.

   The considerations in section 4.5.1 are also applicable here with
   the only difference that MDSC needs to coordinate with different
   PNCs the setup and control of the OTN linear protection as well as
   of the working and protection transport entities (working and
   protection LSPs).

   Two cases can be considered.

   In one case, the working and protection transport entities pass
   through the same PNC domains:

      Working transport entity:   S3, S1, S2,
                          S31, S33, S34,
                          S15, S18

      Protection transport entity: S3, S4, S8,
                          S32,
                          S12, S17, S18

   In another case, the working and protection transport entities can
   pass through different PNC domains:

      Working transport entity:   S3, S5, S7,
                          S11, S12, S17, S18

      Protection transport entity: S3, S1, S2,
                          S31, S33, S34,
                          S15, S18

6.5.2. Segmented Protection

   In order to protect any service defined in section 6.3 from failures
   within the OTN multi-domain transport network, the MDSC should be
   capable to request each PNC to configure OTN intra-domain protection
   when requesting the setup of the ODU2 data plane connection segment.



Busi & King, et al.    Expires April  20, 2018                [Page 23]


Internet-Draft         Transport NBI Use Cases            October 2017


   If linear protection is used within a domain, the considerations in
   section 4.5.1 are also applicable here only for the PNC controlling
   the domain where intra-domain linear protection is provided.

   If PNC1 provides linear protection, the working and protection
   transport entities could be:

      Working transport entity:   S3, S1, S2

      Protection transport entity: S3, S4, S8, S2

   If PNC2 provides linear protection, the working and protection
   transport entities could be:

      Working transport entity:   S15, S18

      Protection transport entity: S15, S12, S17, S18

   If PNC3 provides linear protection, the working and protection
   transport entities could be:

      Working transport entity:   S31, S33, S34

      Protection transport entity: S31, S32, S34

7. Use Case 4: Multi-domain and multi-layer

7.1. Reference Network

   The current considerations discussed in this document are based on
   the following reference network:

        - multiple transport domains: OTN and OCh multi-layer networks

   In this use case, the reference network shown in Figure 3 is used.
   The only difference is that all the transport nodes are capable to
   switch either in the ODU or in the OCh layer.

   All the physical links within each transport network domain are
   therefore assumed to be OCh links, while the inter-domain links are
   assumed to be ODU links as described in section 6.1 (multi-domain
   with single layer - OTN network).

   Therefore, with the exception of the access and inter-domain links,
   no ODU link exists within each domain before an OCh single-domain
   end-to-end data plane connection is created within the network.



Busi & King, et al.    Expires April  20, 2018                [Page 24]


Internet-Draft         Transport NBI Use Cases            October 2017


   The controlling hierarchy is the same as described in Figure 4.

   The interfaces within the scope of this document are the three MPIs
   which should be capable to control both the OTN and OCh layers
   within each PNC domain.

7.2. Topology Abstractions

   Each PNC should provide the MDSC a topology abstraction of its own
   network topology as described in section 5.2.

   As an example, it is assumed that:

   o PNC1 provides a type A grey topology abstraction (likewise in use
      case 2 described in section 5.2)

   o PNC2 provides a type B grey topology abstraction (likewise in use
      case 3 described in section 6.2)

   o PNC3 provides a type B grey topology abstraction with two
      abstract nodes, likewise in use case 3 described in section 6.2,
      and hiding at least some optical parameters to be used within the
      OCh layer, likewise in use case 2 described in section 5.2.

7.3. Service Configuration

   The same service scenarios, as described in section 6.3, are also
   applicable to these use cases with the only difference that single-
   domain end-to-end OCh data plane connections needs to be setup
   before ODU data plane connections.

8. Security Considerations

   Typically, OTN networks ensure a high level of security and data
   privacy through hard partitioning of traffic onto isolated circuits.

   There may be additional security considerations applied to specific
   use cases, but common security considerations do exist and these
   must be considered for controlling underlying infrastructure to
   deliver transport services:

   o use of RESCONF and the need to reuse security between RESTCONF
      components;

   o use of authentication and policy to govern which transport
      services may be requested by the user or application;



Busi & King, et al.    Expires April  20, 2018                [Page 25]


Internet-Draft         Transport NBI Use Cases            October 2017


   o how secure and isolated connectivity may also be requested as an
      element of a service and mapped down to the OTN level.

9. IANA Considerations

   This document requires no IANA actions.

10. References

10.1. Normative References

   [RFC7926] Farrel, A. et al., "Problem Statement and Architecture for
             Information Exchange between Interconnected Traffic-
             Engineered Networks", BCP 206, RFC 7926, July 2016.

   [RFC4427] Mannie, E., Papadimitriou, D., "Recovery (Protection and
             Restoration) Terminology for Generalized Multi-Protocol
             Label Switching (GMPLS)", RFC 4427, April  2006.

   [ACTN-Frame] Ceccarelli, D., Lee, Y. et al., "Framework for
             Abstraction and Control of Transport Networks", draft-
             ietf-teas-actn-framework, work in progress.

   [ITU-T G.709-2016] ITU-T Recommendation G.709 (06/16), "Interfaces
             for the optical transport network", June 2016.

   [ITU-T G.808.1-2014] ITU-T Recommendation G.808.1 (05/14), "Generic
             protection switching - Linear trail and subnetwork
             protection", May 2014.

   [ITU-T G.873.1-2014] ITU-T Recommendation G.873.1 (05/14), "Optical
             transport network (OTN): Linear protection", May 2014.

10.2. Informative References

   [TE-Topo] Liu, X. et al., "YANG Data Model for TE Topologies",
             draft-ietf-teas-yang-te-topo, work in progress.

   [ACTN-YANG] Zhang, X. et al., "Applicability of YANG models for
             Abstraction and Control of Traffic Engineered Networks",
             draft-zhang-teas-actn-yang, work in progress.

   [Path-Compute] Busi, I., Belotti, S. et al., " Yang model for
             requesting Path Computation", draft-busibel-teas-yang-
             path-computation, work in progress.




Busi & King, et al.    Expires April  20, 2018                [Page 26]


Internet-Draft         Transport NBI Use Cases            October 2017


   [RESTCONF]  Bierman, A., Bjorklund, M., and K. Watsen, "RESTCONF
              Protocol", RFC 8040, DOI 10.17487/RFC8040, January 2017,
              <http://www.rfc-editor.org/info/rfc8040>.

   [ONF TR-527] ONF Technical Recommendation TR-527, "Functional
             Requirements for Transport API", June 2016.

   [ONF GitHub] ONF Open Transport (SNOWMASS)
             https://github.com/OpenNetworkingFoundation/Snowmass-
             ONFOpenTransport

11. Acknowledgments

   The authors would like to thank all members of the Transport NBI
   Design Team involved in the definition of use cases, gap analysis
   and guidelines for using the IETF YANG models at the Northbound
   Interface (NBI) of a Transport SDN Controller.

   The authors would like to thank Xian Zhang, Anurag Sharma, Sergio
   Belotti, Tara Cummings, Michael Scharf, Karthik Sethuraman, Oscar
   Gonzalez de Dios, Hans Bjursrom and Italo Busi for having initiated
   the work on gap analysis for transport NBI and having provided
   foundations work for the development of this document.

   This document was prepared using 2-Word-v2.0.template.dot.























Busi & King, et al.    Expires April  20, 2018                [Page 27]


Internet-Draft         Transport NBI Use Cases            October 2017


Authors' Addresses

   Italo Busi (Editor)
   Huawei
   Email: italo.busi@huawei.com

   Daniel King (Editor)
   Lancaster University
   Email: d.king@lancaster.ac.uk

   Sergio Belotti
   Nokia
   Email: sergio.belotti@nokia.com

   Gianmarco Bruno
   Ericsson
   Email: gianmarco.bruno@ericsson.com

   Young Lee
   Huawei
   Email: leeyoung@huawei.com

   Victor Lopez
   Telefonica
   Email: victor.lopezalvarez@telefonica.com

   Carlo Perocchio
   Ericsson
   Email: carlo.perocchio@ericsson.com

   Haomian Zheng
   Huawei
   Email: zhenghaomian@huawei.com















Busi & King, et al.    Expires April  20, 2018                [Page 28]


Html markup produced by rfcmarkup 1.124, available from https://tools.ietf.org/tools/rfcmarkup/