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Versions: 00 01 02 draft-ietf-teas-actn-framework

TEAS Working Group                             Daniele Ceccarelli (Ed)
Internet Draft                                                 Ericsson
Intended status: Informational                          Young Lee (Ed)
Expires: November 2016                                           Huawei



                                                        April 14, 2016



  Framework for Abstraction and Control of Traffic Engineered Networks

                draft-ceccarelli-teas-actn-framework-02



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   carefully, as they describe your rights and restrictions with
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Abstract

   Traffic Engineered networks have a variety of mechanisms to
   facilitate the
   separation of the data plane and control plane.  They also have a
   range of management and provisioning protocols to configure and
   activate network resources.  These mechanisms represent key
   technologies for enabling flexible and dynamic networking.

   Abstraction of network resources is a technique that can be applied
  to a single network domain or across multiple domains to create a
   single virtualized network that is under the control of a network
   operator or the customer of the operator that actually owns
   the network resources.

   This draft provides a framework for Abstraction and Control of
   Traffic Engineered Networks (ACTN).


Table of Contents


   1. Introduction................................................. 3
      1.1. Terminology............................................. 5
   2. Business Model of ACTN....................................... 7
      2.1. Customers............................................... 7
      2.2. Service Providers....................................... 9
      2.3. Network Providers...................................... 11
   3. ACTN architecture........................................... 11
      3.1. Customer Network Controller............................ 14
      3.2. Multi Domain Service Coordinator....................... 15
      3.3. Physical Network Controller............................ 16
      3.4. ACTN interfaces........................................ 17
   4. VN creation process......................................... 19
   5. Access Points and Virtual Network Access Points............. 20
      5.1. Dual homing scenario................................... 22
   6. End point selection & mobility.............................. 23
      6.1. End point selection & mobility......................... 23
      6.2. Preplanned end point migration......................... 24
      6.3. On the fly end point migration......................... 25


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   7. Security.................................................... 25
   8. References.................................................. 25
      8.1. Informative References................................. 25
   9. Contributors................................................ 28
   Authors' Addresses............................................. 28

1. Introduction

   Traffic Engineered networks have a variety of mechanisms to
   facilitate separation of data plane and control plane including
   distributed signaling for path setup and protection, centralized
   path computation for planning and traffic engineering, and a range
   of management and provisioning protocols to configure and activate
   network resources. These mechanisms represent key technologies for
   enabling flexible and dynamic networking.

   The term Traffic Engineered Network in this draft refers to any
   connection-oriented network that has the ability of dynamic
   provisioning, abstracting and orchestrating network resource to the
   network's clients.  Some examples of networks that are in scope of
   this definition are optical networks, MPLS Transport Profile (MPLS-
   TP), MPLS Traffic Engineering (MPLS-TE), and other emerging
   technologies with connection-oriented behavior.

   One of the main drivers for Software Defined Networking (SDN) is a
   decoupling of the network control plane from the data plane. This
   separation of the control plane from the data plane has been already
   achieved with the development of MPLS/GMPLS [GMPLS] and PCE [PCE]
   for TE-based transport networks. One of the advantages of SDN is its
   logically centralized control regime that allows a global view of
   the underlying network under its control. Centralized control in SDN
   helps improve network resources utilization compared with
   distributed network control. For TE-based transport network control,
   PCE is essentially equivalent to a logically centralized control for
   path computation function.

   Two key aspects that need to be solved by SDN are:

      . Network and service abstraction: Detach the network and service
        control from underlying technology and help customer express
        the network as desired by business needs.

      . Coordination of resources across multiple domains and multiple
        layers to provide end-to-end services regardless of whether the
        domains use SDN or not.




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   As networks evolve, the need to provide resource and service
   abstraction has emerged as a key requirement for operators; this
   implies in effect the virtualization of network resources so that
   the network is "sliced" for different tenants shown as a dedicated
   portion of the network resources

   Particular attention needs to be paid to the multi-domain case, where
   Abstraction and Control of Traffic Engineered Networks (ACTN) can
   facilitate virtual network operation via the creation of a single
   virtualized network or a seamless service. This supports operators in
   viewing and controlling different domains (at any dimension: applied
   technology, administrative zones, or vendor-specific technology
   islands) as a single virtualized network.

   Network virtualization refers to allowing the customers of network
   operators (see Section 2.1) to utilize a certain amount of network
   resources as if they own them and thus control their allocated
   resources with higher layer or application processes that enables
   the resources to be used in the most optimal way. More flexible,
   dynamic customer control capabilities are added to the traditional
   VPN along with a customer specific virtual network view. Customers
   control a view of virtual network resources, specifically allocated
   to each one of them. This view is called an abstracted network
   topology. Such a view may be specific to a specific service, the set
   of consumed resources or to a particular customer. Customer
   controller of the virtual network is envisioned to support a
   plethora of distinct applications.  This means that there may be a
   further level of virtualization that provides a view of resources in
   the customer's virtual network for use by an individual application.

   The framework described in this draft is named Abstraction and
   Control of Traffic Engineered Network (ACTN) and facilitates:

      - Abstraction of the underlying network resources to higher-layer
        applications and customers [TE-INFO].

      - Virtualization of particular underlying resources, whose
        selection criterion is the allocation of those resources to a
        particular customer, application or service. [ONF-ARCH]

      - Slicing infrastructure to connect multiple customers to meet
        specific customer's service requirements.

      - Creation of a virtualized environment allowing operators to
        view and control multi-domain networks into a single
        virtualized network;


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      - Possibility of providing a customer with virtualized network or
        services (totally hiding the network).

      - A virtualization/mapping network function that adapts customer
        requests to the virtual resources (allocated to them) to the
        supporting physical network control and performs the necessary
        mapping, translation, isolation and security/policy
        enforcement, etc.; This function is often referred to as
        orchestration.

      - The presentation of the networks as a virtualized topology to
        the customers via open and programmable interfaces. This allows
        for the recursion of controllers in a customer-provider
        relationship.


1.1. Terminology

   The following terms are used in this document. Some of them are
   newly defined, some others reference existing definition:
      - Node: A node is a topological entity describing the "opaque"
        forwarding aspect of the topological component which represents
        the opportunity to enable forwarding between points at the edge
        of the node. It provides the context for instructing the
        formation, adjustment and removal of the forwarding. A node, in
        a VN network, can be represented by single physical entity or
        by a group of nodes moving from physical to virtual network.

      - Link: A link is a topological entity describing the effective
        adjacency between two or more forwarding entities, such as two
        or more nodes. In its basic form (i.e., point-to-point Link) it
        associates an edge point of a node with an equivalent edge
        point on another node. Links in virtual network is in fact
        connectivity, realized by bandwidth engineering between any two
        nodes meeting certain criteria, for example, redundancy,
        protection, latency, not tied to any technology specific
        characteristics like timeslots or wavelengths. The link can be
        dynamic, realized by a service in underlay, or static.


      - PNC domain: A PNC domain includes all the resources under the
        control of a single PNC. It can be composed by different
        routing domains, administrative domains and different layers.
        The interconnection between PNC domains can be a link or a
        node.


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                             border
                    -------   link    -------
                   (       )---------(       )
                  -         -       -         -
                 (   PNC     )+---+(   PNC     )
                (  Domain X   )   (  Domain Y   )
                 (           )+---+(           )
                  -         - border-         -
                   (       )   node  (       )
                    -------           -------


                       Figure 1 : PNC domain borders


      - Virtual Network: A Virtual Network (VN) is a customer view of the
        transport network.  It is composed by a set of physical
        resources sliced in the provider network and presented to the
        customer as a set of abstract resources i.e. virtual nodes and
        virtual links. Depending on the agreement between customer and
        provider a VN can be just represented by:

           o How the end points can be connected with given SLA
             attributes(e.g., re satisfying the customer's objectives)
           o A pre-configured set of physical resources
           o Or as outcome of a dynamic request from customer.

        In the first case the VN can be seen at customer level as an
        e2e connectivity that can be formed by recursive aggregation of
        lower layers tunnels within the provider domain.
        When the VN is pre-configured, it is provided after a static
        negotiation between customer and provider while in the third
        case VN can be dynamically created, deleted, or modified in
        response to requests from the customer. This implies dynamic
        changes of network resources reserved for the customer.
        In the second and third case , once that customer has obtained
        his VN, can act upon the virtual network resources to perform
        connection management (set-up/release/modify connections).

      - Abstract Topology: Every lower controller in the provider
        network, when is representing its network topology to an higher
        layer, it may want to hide details of the actual network
        topology. In such case, an abstract topology may be used for
        this purpose. Abstract topology enhances scalability for the
        MDSC to operate multi-domain networks


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      - Access link: A link between a customer node and a provider
        node.

      - Inter domain link: A link between domains managed by different
        PNCs. The MDSC is in charge of managing inter-domain links.

      - Border node: A node whose interfaces belong to different
        domains. It may be managed by different PNCs or by the MDSC.

      - Access Point (AP): An access point is defined on an access
        link. It is used to keep confidentiality between the customer
        and the provider. It is an identifier shared between the
        customer and the provider, used  to map the end points of the
        border node in the provider NW. The AP can be used by the
        customer when requesting connectivity service to the provider.
        A number of parameters, e.g. available bandwidth, need to be
        associated to the AP to qualify it.

      - VN Access Point (VNAP): A VNAP is defined within an AP as part
        of a given VN and is used to identify the portion of the AP,
        and hence of the access link) dedicated to a given VN.


2. Business Model of ACTN

   The Virtual Private Network (VPN) [RFC4026] and Overlay Network (ON)
   models [RFC4208] are built on the premise that one single network
   provider provides all virtual private or overlay networks to its
   customers. These models are simple to operate but have some
   disadvantages in accommodating the increasing need for flexible and
   dynamic network virtualization capabilities.

   The ACTN model is built upon entities that reflect the current
   landscape of network virtualization environments. There are three
   key entities in the ACTN model [ACTN-PS]:

      - Customers
      - Service Providers
      - Network Providers


2.1. Customers

   Within the ACTN framework, different types of customers may be taken
   into account depending on the type of their resource needs, on their



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   number and type of access. As example, it is possible to group them
   into two main categories:

   Basic Customer: Basic customers include fixed residential users,
   mobile users and small enterprises. Usually the number of basic
   customers is high; they require small amounts of resources and are
   characterized by steady requests (relatively time invariant). A
   typical request for a basic customer is for a bundle of voice
   services and internet access. Moreover basic customers do not modify
   their services themselves; if a service change is needed, it is
   performed by the provider as proxy and they generally have very few
   dedicated resources (subscriber drop), with everything else shared
   on the basis of some SLA, which is usually best-efforts.

   Advanced Customer: Advanced customers typically include enterprises,
   governments and utilities. Such customers can ask for both point to
   point and multipoint connectivity with high resource demand
   significantly varying in time and from customer to customer. This is
   one of the reasons why a bundled service offering is not enough and
   it is desirable to provide each of them with a customized virtual
   network service.

   Advanced customers may own dedicated virtual resources, or share
   resources. They may also have the ability to modify their service
   parameters within the scope of their virtualized environments.

   As customers are geographically spread over multiple network
   provider domains, they have to interface multiple providers and may
   have to support multiple virtual network services with different
   underlying objectives set by the network providers. To enable these
   customers to support flexible and dynamic applications they need to
   control their allocated virtual network resources in a dynamic
   fashion, and that means that they need an abstracted view of the
   topology that spans all of the network providers.


   ACTN's primary focus is Advanced Customers.

   Customers of a given service provider can in turn offer a service to
   other customers in a recursive way. An example of recursiveness with
   2 service providers is shown below.

      - Customer (of service B)
      - Customer (of service A) & Service Provider (of service B)
      - Service Provider (of service A)
      - Network Provider



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   +------------------------------------------------------------+   ---
   |                                                            |    ^
   |                                     Customer (of service B)|    .
   | +--------------------------------------------------------+ |    B
   | |                                                        | |--- .
   | |Customer (of service A) & Service Provider(of service B)| | ^  .
   | | +---------------------------------------------------+  | | .  .
   | | |                                                   |  | | .  .
   | | |                    Service Provider (of service A)|  | | A  .
   | | |+------------------------------------------+       |  | | .  .
   | | ||                                          |       |  | | .  .
   | | ||                          Network provider|       |  | | v  v
   | | |+------------------------------------------+       |  | |------
   | | +---------------------------------------------------+  | |
   | +--------------------------------------------------------+ |
   +------------------------------------------------------------+

                     Figure 2 : Service Recursiveness.

2.2. Service Providers

   Service providers are the providers of virtual network services to
   their customers. Service providers may or may not own physical
   network resources. When a service provider is the same as the
   network provider, this is similar to traditional VPN models. This
   model works well when the customer maintains a single interface with
   a single provider.  When customer location spans across multiple
   independent network provider domains, then it becomes hard to
   facilitate the creation of end-to-end virtual network services with
   this model.

   A more interesting case arises when network providers only provide
   infrastructure while service providers directly interface their
   customers. In this case, service providers themselves are customers
   of the network infrastructure providers. One service provider may
   need to keep multiple independent network providers as its end-users
   span geographically across multiple network provider domains as
   shown in Figure 2 where Service Provider A uses resources from
   Network Provider A and Network Provider B to offer a virtualized
   network to its customer.









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   Customer            X -----------------------------------X

   Service Provider A  X -----------------------------------X

   Network Provider B                     X-----------------X

   Network Provider A  X------------------X



   Figure 3 : A service Provider as Customer of Two Network Providers.




   The ACTN network model is predicated upon this three tier model and
   is summarized in Figure 3:

                       +----------------------+
                       |       customer       |
                       +----------------------+
                                 |
                                 |   /\  Service/Customer specific
                                 |   ||  Abstract Topology
                                 |   ||
                       +----------------------+  E2E abstract
                       |  Service Provider    | topology creation
                       +----------------------+
                       /         |            \
                      /          |             \  Network Topology
                     /           |              \ (raw or abstract)
                    /            |               \
   +------------------+   +------------------+   +------------------+
   |Network Provider 1|   |Network Provider 2|   |Network Provider 3|
   +------------------+   +------------------+   +------------------+



                       Figure 4 : Three tier model.



   There can be multiple types of service providers.



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      . Data Center providers: can be viewed as a service provider type
        as they own and operate data center resources to various WAN
        customers, they can lease physical network resources from
        network providers.
      . Internet Service Providers (ISP): can be a service provider of
        internet services to their customers while leasing physical
        network resources from network providers.
      . Mobile Virtual Network Operators (MVNO): provide mobile
        services to their end-users without owning the physical network
        infrastructure.

2.3. Network Providers

   Network Providers are the infrastructure providers that own the
   physical network resources and provide network resources to their
   customers. The layered model proposed by this draft separates the
   concerns of network providers and customers, with service providers
   acting as aggregators of customer requests.

3. ACTN architecture

   This section provides a high-level control and interface model of
   ACTN.

   The ACTN architecture, while being aligned with the ONF SDN
   architecture [ONF-ARCH], is presenting a 3-tiers reference model. It
   allows for hierarchy and recursiveness not only of SDN controllers
   but also of traditionally controlled domains. It defines three types
   of controllers depending on the functionalities they implement. The
   main functionalities that are identified are:

      . Multi domain coordination function: With the definition of
        domain being "everything that is under the control of the same
        controller",it is needed to have a control entity that oversees
        the specific aspects of the different domains and to build a
        single abstracted end-to-end network topology in order to
        coordinate end-to-end path computation and path/service
        provisioning.

      . Virtualization/Abstraction function: To provide an abstracted
        view of the underlying network resources towards customer,
        being it the client or a higher level controller entity. It
        includes computation of customer resource requests into virtual
        network paths based on the global network-wide abstracted
        topology and the creation of an abstracted view of network
        slices allocated to each customer, according to customer-



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        specific virtual network objective functions, and to the
        customer traffic profile.

      . Customer mapping function: In charge of mapping customer VN
        setup commands into network provisioning requests to the
        Physical Network Controller (PNC) according to business OSS/NMS
        provisioned static or dynamic policy. Moreover it provides
        mapping and translation of customer virtual network slices into
        physical network resources


      . Virtual service coordination: Virtual service coordination
        function in ACTN incorporates customer service-related
        knowledge into the virtual network operations in order to
        seamlessly operate virtual networks while meeting customer's
        service requirements.


   The virtual services that are coordinated under ACTN can be split
   into two categories:

      . Service-aware Connectivity Services: This category includes all
        the network service operations used to provide connectivity
        between customer end-points while meeting policies and service
        related constraints. The data model for this category would
        include topology entities such as virtual nodes, virtual links,
        adaptation and termination points and service-related entities
        such as policies and service related constraints. (See Section
        4.2.2)

      . Network Function Virtualization Services: These kinds of
        services are usually setup in NFV (e.g. cloud) providers and
        require connectivity between a customer site and the NFV
        provider site (e.g. a data center). These VNF services may
        include a security function like firewall, a traffic optimizer,
        the provisioning of storage or computation capacity. In these
        cases the customer does not care whether the service is
        implemented in a given data center or another. This allows the
        network provider divert customer requests where most suitable.
        This is also known as "end points mobility" case. (See Section
        4.2.3)

   The types of controller defined are shown in Figure 4 below and are
   the following:

      . CNC - Customer Network Controller
      . MDSC - Multi Domain Service Coordinator


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      . PNC - Physical Network Controller














































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   VPN customer         NW Mobile Customer     ISP NW service Customer
       |                         |                           |
   +-------+                 +-------+                   +-------+
   | CNC-A |                 | CNC-B |                   | CNC-C |
   +-------+                 +-------+                   +-------+
        \                        |                           /
          -----------            |CMI I/F      --------------
                     \           |            /
                      +-----------------------+
                      |         MDSC          |
                      +-----------------------+
                      /          |            \
         -------------           |MPI I/F      -------------
        /                        |                          \
   +-------+                 +-------+                   +-------+
   |  PNC  |                 |  PNC  |                   |  PNC  |
   +-------+                 +-------+                   +-------+
        | GMPLS             /      |                      /    \
        | trigger          /       |                     /      \
       --------         ----      +-----+            +-----+     \
      (        )       (    )     | PNC |            | PCE |      \
      -        -      ( Phys )    +-----+            +-----+    -----
     (  GMPLS   )      (Netw)        |                /        (     )
    (  Physical  )      ----         |               /        ( Phys. )
     (  Network )                 -----        -----           ( Net )
      -        -                 (     )      (     )           -----
      (        )                ( Phys. )    ( Phys  )
       --------                  ( Net )      ( Net )
                                  -----        -----

                     Figure 5 : ACTN Control Hierarchy



    3.1. Customer Network Controller

   A Virtual Network Service is instantiated by the Customer Network
   Controller via the CMI (CNC-MDSC Interface). As the Customer Network
   Controller directly interfaces the applications, it understands
   multiple application requirements and their service needs. It is
   assumed that the Customer Network Controller and the MDSC have a
   common knowledge on the end-point interfaces based on their business
   negotiation prior to service instantiation. End-point interfaces
   refer to customer-network physical interfaces that connect customer
   premise equipment to network provider equipment.




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   In addition to abstract networks, ACTN allows to provide the CNC
   with services. Example of services include connectivity between one
   of the customer's end points with a given set of resources in a data
   center from the service provider.



    3.2. Multi Domain Service Coordinator

   The MDSC (Multi Domain Service Coordinator) sits between the CNC
   (the one issuing connectivity requests) and the PNCs (Physical
   Network Controllersr - the ones managing the physical network
   resources). The MDSC can be collocated with the PNC, especially in
   those cases where the service provider and the network provider are
   the same entity.

   The internal system architecture and building blocks of the MDSC are
   out of the scope of ACTN. Some examples can be found in the
   Application Based Network Operations (ABNO) architecture [ABNO] and
   the ONF SDN architecture [ONF-ARCH].

   The MDSC is the only building block of the architecture that is able
   to implement all the four ACTN main functionalities, i.e. multi
   domain coordination function, virtualization/abstraction function,
   customer mapping function and virtual service coordination. The key
   point of the MDSC and the whole ACTN framework is detaching the
   network and service control from underlying technology and help
   customer express the network as desired by business needs. The MDSC
   envelopes the instantiation of right technology and network control
   to meet business criteria. In essence it controls and manages the
   primitives to achieve functionalities as desired by CNC
   A hierarchy of MDSCs can be foreseen for scalability and
   administrative choices.














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   +-------+                 +-------+                 +-------+
   | CNC-A |                 | CNC-B |                 | CNC-C |
   +-------+                 +-------+                 +-------+
       \                       |                        /
          ----------             |             ----------
                     \           |            /
                      +-----------------------+
                      |         MDSC          |
                      +-----------------------+
                      /          |            \
            ----------           |             -----------
           /                     |                        \
   +----------+              +----------+             +--------+
   |   MDSC   |              |   MDSC   |             |  MDSC  |
   +----------+              +----------+             +--------+
        |                    /     |                     /    \
        |                   /      |                    /      \
     +-----+           +-----+  +-----+            +-----+  +-----+
     | PNC |           | PNC |  | PNC |            | PNC |  | PNC |
     +-----+           +-----+  +-----+            +-----+  +-----+


                    Figure 6 : Controller recursiveness

   A key requirement for allowing recursion of MDSCs is that a single
   interface needs to be defined both for the north and the south
   bounds.
   In order to allow for multi-domain coordination a 1:N relationship
   must be allowed between MDSCs and between MDSCs and PNCs (i.e. 1
   parent MDSC and N child MDSC or 1 MDSC and N PNCs). In addition to
   that it could be possible to have also a M:1 relationship between
   MDSC and PNC to allow for network resource partitioning/sharing
   among different customers not necessarily connected to the same MDSC
   (e.g. different service providers).

    3.3. Physical Network Controller

   The Physical Network Controller is the one in charge of configuring
   the network elements, monitoring the physical topology of the
   network and passing it, either raw or abstracted, to the MDSC.

   The internal architecture of the PNC, his building blocks and the
   way it controls its domain, are out of the scope of ACTN. Some
   examples can be found in the Application Based Network Operations
   (ABNO) architecture [ABNO] and the ONF SDN architecture [ONF-ARCH]


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   The PNC, in addition to being in charge of controlling the physical
   network, is able to implement two of the four ACTN main
   functionalities: multi domain coordination function and
   virtualization/abstraction function
   A hierarchy of PNCs can be foreseen for scalability and
   administrative choices.

    3.4. ACTN interfaces

   To allow virtualization and multi domain coordination, the network
   has to provide open, programmable interfaces, in which customer
   applications can create, replace and modify virtual network
   resources and services in an interactive, flexible and dynamic
   fashion while having no impact on other customers. Direct customer
   control of transport network elements and virtualized services is
   not perceived as a viable proposition for transport network
   providers due to security and policy concerns among other reasons.
   In addition, as discussed in the previous section, the network
   control plane for transport networks has been separated from data
   plane and as such it is not viable for the customer to directly
   interface with transport network elements.

   Figure 5 depicts a high-level control and interface architecture for
   ACTN. A number of key ACTN interfaces exist for deployment and
   operation of ACTN-based networks. These are highlighted in Figure 5
   (ACTN Interfaces) below:






















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                .--------------
               -------------   |
              | Application |--
               -------------
                     ^
                     | I/F A                 --------
                     v                      (        )
                --------------             -          -
               | Customer     |           (  Customer  )
               |  Network     |--------->(    Network   )
               |   Controller |           (            )
                --------------             -          -
                     ^                      (        )
                     | I/F B                 --------
                     v
                --------------
               | MultiDomain  |
               |  Service     |
               |   Coordinator|            --------
                --------------            (        )
                     ^                   -          -
                     | I/F C            (  Physical  )
                     v                 (    Network   )
                  ---------------       (            )     --------
                 |               |<----> -          -     (        )
                --------------   |        (        )     -         -
               | Physical     |--          --------     (  Physical  )
               |  Network     |<---------------------->(    Network   )
               |   Controller |         I/F D           (            )
                --------------                           -         -
                                                          (        )
                                                           --------

                        Figure 7 : ACTN Interfaces

   The interfaces and functions are described below:

      . Interface A: A north-bound interface (NBI) that will
        communicate the service request or application demand. A
        request will include specific service properties, including:
        services, topology, bandwidth and constraint information.

      . Interface B: The CNC-MDSC Interface (CMI) is an interface
        between a Customer Network Controller and a Multi Service
        Domain Controller. It requests the creation of the network
        resources, topology or services for the applications. The
        Virtual Network Controller may also report potential network


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        topology availability if queried for current capability from
        the Customer Network Controller.


      . Interface C: The MDSC-PNC Interface (MPI) is an interface
        between a Multi Domain Service Coordinator and a Physical
        Network Controller. It communicates the creation request, if
        required, of new connectivity of bandwidth changes in the
        physical network, via the PNC. In multi-domain environments,
        the MDSC needs to establish multiple MPIs, one for each PNC, as
        there are multiple PNCs responsible for its domain control.


      . Interface D: The provisioning interface for creating forwarding
        state in the physical network, requested via the Physical
        Network Controller.


   The interfaces within the ACTN scope are B and C.

4. VN creation process

   The provider can present to the customer different level of network
   abstraction, spanning from one extreme (say "black") where nothing
   is shown, just the APs, to the other extreme (say "white") where a
   slice of the network is shown to the customer. There are shades of
   gray in between where a number of abstract links and nodes can be
   shown.

   The VN creation is composed by two phases: Negotiation and
   Implementation.

   Negotiation: In the case of grey/white topology abstraction, there
   is an a priori phase in which the customer agrees with the provider
   on the type of topology to be shown, e.q. 10 virtual links and 5
   virtual nodes with a given interconnectivity. This is something that
   is assumed to be preconfigured by the operator off-line, what is
   online is the capability of modifying/deleting something (e.g. a
   virtual link). In the case of "black" abstraction this negotiation
   phase does not happen, in the sense that the customer can only see
   the APs of the network.



   Implementation: In the case of black topology abstraction, the
   customers can ask for connectivity with given constraints/SLA


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   between the APs and LSPs/tunnels are created by the provider to
   satisfy the request. What the customer sees is only that his CEs are
   connected with a given SLA. In the case of grey/white topology the
   customer creates his own LSPs accordingly to the topology that was
   presented to him.


5. Access Points and Virtual Network Access Points

   In order not to share unwanted topological information between the
   customer domain and provider domain, a new entity is defined and
   associated to an access link, the Access Point (AP). See the
   definition of AP in Section 1.1.

   A customer node will use APs as the end points for the request of
   VNs.

   A number of parameters need to be associated to the APs. Such
   parameters need to include at least: the maximum reservable
   bandwidth on the link, the available bandwidth and the link
   characteristics (e.g. switching capability, type of mapping).

   Editor note: it is not appropriate to define link characteristics
   like bandwidth against a point (AP). A solution needs to be found.

                         -------------
                        (             )
                       -               -
        +---+ X       (                 )      Z +---+
        |CE1|---+----(                   )---+---|CE2|
        +---+   |     (                 )    |   +---+
               AP1     -               -    AP2
                        (             )
                         -------------


                  Figure 8 : APs definition customer view

   Let's take as example a scenario in which CE1 is connected to the
   network via a 10Gb link and CE2 via a 40Gb link. Before the creation
   of any VN between AP1 and AP2 the customer view can be summarized as
   follows:






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   +-----+----------+-------------+----------+
   |AP id| MaxResBw | AvailableBw | CE,port  |
   +-----+----------+-------------+----------+
   | AP1 |   10Gb   |    10Gb     |CE1,portX |
   +-----+----------+-------------+----------+
   | AP2 |   40Gb   |    40Gb     |CE2,portZ |
   +-----+----------+-------------+----------+

  Table 1: AP - customer view

   On the other side what the provider sees is:

             -------            -------
            (       )          (       )
           -         -        -         -
      W  (+---+       )      (       +---+)  Y
   -+---( |PE1| Dom.X  )----(  Dom.Y |PE2| )---+-
    |    (+---+       )      (       +---+)    |
    AP1    -         -        -         -     AP2
            (       )          (       )
             -------            -------


                    Figure 9 : Provider view of the AP

   Which in the example above ends up in a summarization as follows:

   +-----+----------+-------------+----------+
   |AP id| MaxResBw | AvailableBw | PE,port  |
   +-----+----------+-------------+----------+
   | AP1 |   10Gb   |    10Gb     |PE1,portW |
   +-----+----------+-------------+----------+
   | AP2 |   40Gb   |    40Gb     |PE2,portY |
   +-----+----------+-------------+----------+

   Table 2: AP - provider view

   The second entity that needs to be defined is a structure within the
   AP that is linked to a VN and that is used to allow for different VN
   to be provided starting from the same AP. It also allows reserving
   the bandwidth for the VN on the access link. Such entity is called
   Virtual Network Access Point. For each virtual network is defined on
   an AP, a different VNAP is created.

   In the simple scenario depicted above we suppose to create two
   virtual networks. The first one has with VN identifier 9 between AP1



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   and AP2 with and bandwidth of 1Gbps, while the second one with VN id
   5, again between AP1 and AP2 and bandwidth 2Gbps.

   The customer view would evolve as follows:

   +---------+----------+-------------+----------+
   |AP/VNAPid| MaxResBw | AvailableBw | PE,port  |
   +---------+----------+-------------+----------+
   |AP1      |  10Gbps  |    7Gbps    |PE1,portW |
   | -VNAP1.9|   1Gbps  |     N.A.    |          |
   | -VNAP1.5|   2Gbps  |     N.A     |          |
   +---------+----------+-------------+----------+
   |AP2      |   40Gb   |    37Gb     |PE2,portY |
   | -VNAP2.9|   1Gbps  |     N.A.    |          |
   | -VNAP2.5|   2Gbps  |     N.A     |          |
   +---------+----------+-------------+----------+

  Table 3: AP and VNAP - provider view after VN creation

     5.1. Dual homing scenario

   Often there is a dual homing relationship between a CE and a pair of
   PE. This case needs to be supported also by the definition of VN, AP
   and VNAP. Suppose to have CE1 connected to two different PE in the
   operator domain via AP1 and AP2 and the customer needing 5Gbps of
   bandwidth between CE1 and CE2.


            AP1    --------------    AP3
           -------(PE1)       (PE3) -------
        W /      -                -        \X
   +---+ /      (                  )        \ +---+
   |CE1|       (                    )         |CE2|
   +---+ \      (                  )        / +---+
        Y \      -                -        /Z
           -------(PE2)       (PE4) -------
            AP2    --------------   AP4


                    Figure 10  : Dual homing scenario

   In this case the customer will request for a VN between AP1, AP2 and
   AP3 specifying a dual homing relationship between AP1 and AP2. As a
   consequence no traffic will be flowing between AP1 and AP2. The dual
   homing relationship would then be mapped against the VNAPs (since
   other independent VNs might have AP1 and AP2 as end points).



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   The customer view would be as follows:

   +---------+----------+-------------+----------+-----------+
   |AP/VNAPid| MaxResBw | AvailableBw | CE,port  |Dual Homing|
   +---------+----------+-------------+----------+-----------+
   |AP1      |  10Gbps  |    5Gbps    |CE1,portW |           |
   | -VNAP1.9|   5Gbps  |     N.A.    |          | VNAP2.9   |
   +---------+----------+-------------+----------+-----------+
   |AP2      |  40Gbps  |    35Gbps   |CE1,portY |           |
   | -VNAP2.9|   5Gbps  |     N.A.    |          | VNAP1.9   |
   +---------+----------+-------------+----------+-----------+
   |AP3      |  40Gbps  |   35Gbps    |CE2,portZ |           |
   | -VNAP3.9|   5Gbps  |     N.A.    |          |   NONE    |
   +---------+----------+-------------+----------+-----------+

   Table 4: Dual homing - customer view after VN creation



6. End point selection & mobility

   Virtual networks could be used as the infrastructure to connect a
   number of sites of a customer among them or to provide connectivity
   between customer sites and virtualized network functions (VNF) like
   for example virtualized firewall, vBNG, storage, computational
   functions.

     6.1. End point selection & mobility

   A VNF could be deployed in different places (e.g. data centers A, B
   or C in figure below) but the VNF provider (=ACTN customer) doesn't
   know which is the best site where to install the VNF from a network
   point of view (e.g. latency). For example it is possible to compute
   the path minimizing the delay between AP1 and AP2, but the customer
   doesn't know a priori if the path with minimum delay is towards A, B
   or C.












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                    -------            -------
                   (       )          (       )
                  -         -        -         -
   +---+         (           )      (           )        +----+
   |CE1|---+----(  Domain X   )----(  Domain Y   )---+---|DC-A|
   +---+   |     (           )      (           )    |   +----+
           AP1    -         -        -         -    AP2
                   (       )          (       )
                    ---+---            ---+---
                   AP3 |              AP4 |
                    +----+              +----+
                    |DC-B|              |DC-C|
                    +----+              +----+

                     Figure 11  : End point selection

   In this case the VNF provider (=ACTN customer) should be allowed to
   ask for a VN between AP1 and a set of end points. The list of end
   points is provided by the VNF provider. When the end point is
   identified the connectivity can be instantiated and a notification
   can be sent to the VNF provider for the instantiation of the VNF.

     6.2. Preplanned end point migration

   A premium SLA for VNF service provisioning consists on the offering
   of a protected VNF instantiated on two or more sites and with a hot
   stand-by protection mechanism. In this case the VN should be
   provided so to switch from one end point to another upon a trigger
   from the VNF provider or an automatic failure detection mechanism.
   An example is provided in figure below where the request from the
   VNF provider is for connectivity with given constraint and
   resiliency between CE1 and a VNF with primary installation in DC-A
   and a protection in DC-C.















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                    -------            -------
                   (       )          (       )
                  -         -    __  -         -
   +---+         (           )      (           )        +----+
   |CE1|---+----(  Domain X   )----(  Domain Y   )---+---|DC-A|
   +---+   |     (           )      (           )    |   +----+
           AP1    -         -        -         -    AP2    |
                   (       )          (       )            |
                    ---+---            ---+---             |
                   AP3 |              AP4 |         HOT STANDBY
                                       +----+              |
                                       |DC-C|<-------------
                                       +----+

                Figure 12  : Preplanned endpoint migration



     6.3. On the fly end point migration

   The one the fly end point migration concept is very similar to the
   end point selection one. The idea is to give the provider not only
   the list of sites where the VNF can be installed, but also a
   mechanism to notify changes in the network that have impacts on the
   SLA. After an handshake with the customer controller/applications,
   the bandwidth in network would be moved accordingly with the moving
   of the VNFs.

7. Security

   TBD

8. References

    8.1. Informative References

   [PCE]    Farrel, A., Vasseur, J.-P., and J. Ash, "A Path
             Computation Element (PCE)-Based Architecture", IETF RFC
             4655, August 2006.

   [RFC4026] L. Andersson, T. Madsen, "Provider Provisioned Virtual
             Private Network (VPN) Terminology", RFC 4026, March 2005.







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   [RFC4208] G. Swallow, J. Drake, H.Ishimatsu, Y. Rekhter,
             "Generalized Multiprotocol Label Switching (GMPLS) User-
             Network Interface (UNI): Resource ReserVation Protocol-
             Traffic Engineering (RSVP-TE) Support for the Overlay
             Model", RFC 4208, October 2005.



   [PCE-S]   Crabbe, E, et. al., "PCEP extension for stateful
             PCE",draft-ietf-pce-stateful-pce, work in progress.



   [GMPLS]   Manning, E., et al., "Generalized Multi-Protocol Label
             Switching (GMPLS) Architecture", RFC 3945, October 2004.



   [NFV-AF]  "Network Functions Virtualization (NFV); Architectural
             Framework", ETSI GS NFV 002 v1.1.1, October 2013.



   [ACTN-PS] Y. Lee, D. King, M. Boucadair, R. Jing, L. Contreras
             Murillo, "Problem Statement for Abstraction and Control of
             Transport Networks", draft-leeking-actn-problem-statement,
             work in progress.

   [ONF]    Open Networking Foundation, "OpenFlow Switch Specification
             Version 1.4.0 (Wire Protocol 0x05)", October 2013.

   [TE-INFO] A. Farrel, Editor, "Problem Statement and Architecture for
             Information Exchange Between Interconnected Traffic
             Engineered Networks", draft-ietf-teas-interconnected-te-
             info-exchange, work in progress.

   [ABNO]   King, D., and Farrel, A., "A PCE-based Architecture for
             Application-based Network Operations", draft-farrkingel-
             pce-abno-architecture, work in progress.

   [ACTN-Info] Y. Lee, S. Belotti, D. Dhody, "Information Model for
             Abstraction and Control of Transport Networks", draft-
             leebelotti-teas-actn-info, work in progress.

   [Cheng] W. Cheng, et. al., "ACTN Use-cases for Packet Transport
             Networks in Mobile Backhaul Networks", draft-cheng-actn-
             ptn-requirements, work in progress.


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   [Dhody] D. Dhody, et. al., "Packet Optical Integration (POI) Use
             Cases for Abstraction and Control of Transport Networks
             (ACTN)", draft-dhody-actn-poi-use-case, work in progress.

   [Fang] L. Fang, "ACTN Use Case for Multi-domain Data Center
             Interconnect", draft-fang-actn-multidomain-dci, work in
             progress.

   [Klee] K. Lee, H. Lee, R. Vilata, V. Lopez, "ACTN Use-case for On-
             demand E2E Connectivity Services in Multiple Vendor Domain
             Transport Networks", draft-klee-actn-connectivity-multi-
             vendor-domains, work in progress.

   [Kumaki] K. Kumaki, T. Miyasaka, "ACTN : Use case for Multi Tenant
             VNO ", draft-kumaki-actn-multitenant-vno, work in
             progress.

   [Lopez] D. Lopez (Ed), "ACTN Use-case for Virtual Network Operation
             for Multiple Domains in a Single Operator Network", draft-
             lopez-actn-vno-multidomains, work in progress.

   [Shin] J. Shin, R. Hwang, J. Lee, "ACTN Use-case for Mobile Virtual
             Network Operation for Multiple Domains in a Single
             Operator Network", draft-shin-actn-mvno-multi-domain, work
             in progress.

   [Xu] Y. Xu, et. al., "Use Cases and Requirements of Dynamic Service
             Control based on Performance Monitoring in ACTN
             Architecture", draft-xu-actn-perf-dynamic-service-control,
             work in progress.


















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9. Contributors

Authors' Addresses

   Daniele Ceccarelli (Editor)
   Ericsson
   Torshamnsgatan,48
   Stockholm, Sweden
   Email: daniele.ceccarelli@ericsson.com


   Young Lee (Editor)
   Huawei Technologies
   5340 Legacy Drive
   Plano, TX 75023, USA
   Phone: (469)277-5838
   Email: leeyoung@huawei.com

   Luyuan Fang
   Email: luyuanf@gmail.com

   Diego Lopez
   Telefonica I+D
   Don Ramon de la Cruz, 82
   28006 Madrid, Spain
   Email: diego@tid.es

   Sergio Belotti
   Alcatel Lucent
   Via Trento, 30
   Vimercate, Italy
   Email: sergio.belotti@alcatel-lucent.com

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

   Dhruv Dhoddy
   Huawei Technologies
   dhruv.ietf@gmail.com

   Gert Grammel
   Juniper Networks
   ggrammel@juniper.net





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