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Network Working Group                                    Kwang-koog Lee
Internet Draft                                               Hosong Lee
Intended status: Informational                                       KT
Expires January 2018                                     Ricard Vilalta
                                                                   CTTC
                                                           Victor Lopez
                                                             Telefonica


                                                          July 31, 2017

      ACTN use-case for E2E network services in multiple vendor domain
                             transport networks


            draft-klee-teas-actn-connectivity-multi-domain-03.txt


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   carefully, as they describe your rights and restrictions with
   respect to this document.

Abstract

   This document provides a use-case that addresses the need for
   facilitating the application of virtual network abstractions and the
   control and management of end-to-end network services that traverse
   multiple vendor domain transport networks.

   These abstractions shall help create a virtualized environment
   supporting operators in viewing and controlling different vendor
   domains, especially for end-to-end network connectivity service for
   a single operator.



Table of Contents


   1. Introduction...................................................2
   2. End-to-End Network Services in Multi-vendor Domain Transport
   Networks..........................................................3
      2.1. Example A - Leased Line Services..........................5
      2.2. Example B - Data Center Interconnect (DCI)................6
   3. Requirements...................................................7
   4. References....................................................10
   5. Acknowledgement...............................................10
   6. Contributors..................................................11

1. Introduction

   Network operators build and operate their network using multiple
   domains (i.e., core and access networks) in different dimensions.
   Domains may be defined by a collection of links and nodes (each of a
   different technology), administrative zones under the concern of a
   particular business entity, or vendor-specific "islands" where
   specific control mechanisms have to be applied. Due to the
   technology of each vendor, the optical components cannot be
   interconnected. Even, the interconnection of components supporting
   the same technology is not easy since their control and management
   system is tightly coupled with their own devices. Therefore each
   optical domain becomes an isolated island in terms of the control
   and management of end-to-end services traversing multiple domains.

   The network operators use vendor-specific NMS implementations along
   with an operator-tailored umbrella provisioning system, which may
   include a technology specific Operations Support System (OSS).
   Thanks to the evolution of vendor specific SDN controllers, the

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   network operators require a network entity, which abstracts the
   details of the optical layer while enabling control and management
   of the end-to-end services traversing multiple domains. The
   establishment of end-to-end connections spanning several of these
   domains is a perpetual problem for operators, which need to address
   both interoperability and operational concerns at the control and
   data planes.

   The introduction of new services, often requiring connections that
   traverse multiple domains, needs significant planning, and several
   manual operations to interface multiple vendor-specific domains in
   which specific control/management mechanisms of the vendor equipment
   have to be applied (e.g., EMS/NMS, OSS/BSS, control plane, SDN
   controller, etc.). Undoubtedly, establishing an on-demand end-to-end
   connection which requires provisioning based on dynamic resource
   information is more difficult in the current network context.

   This document provides a use-case that addresses the need for
   creating a virtualized environment supporting operators in viewing
   and controlling different vendor domains, especially for end-to-end
   network services for a single operator. Surely, the use-case could
   be also available for the interconnection of end-to-end services for
   multiple operators. This will accelerate rapid deployment of new
   services, including more dynamic and elastic services, and improve
   overall network operations and scaling of existing services.

   This use-case is a part of the overarching work, called Abstraction
   and Control of Transport Networks (ACTN). Related documents are the
   ACTN Requirements [ACTN-Req], ACTN-framework [ACTN-Frame] and the
   problem statement [ACTN-PS].

2. End-to-End Network Services in Multi-vendor Domain Transport
   Networks

   This section provides an architecture example to illustrate the
   context of the current challenges and issues operators face in
   delivering end-to-end network services in operators' multi-vendor
   domain transport networks.












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                                                                   |
     | /                    End-to-End Connection                \ |
     |/-----------------------------------------------------------\|
     |\-----------------------------------------------------------/|
     | \                                                         / |
     |                                                             |
     |                      +----------------+                     |
     |                      |                |                     |
     |                      |    Converged   |                     |
     |                      |  Packet-Optical|                     |
     |     +-------------+  |    Core Domain |  +-------------+    |
     |     |             |--|   (Vendor A)   |--|             |    |
   +----+  |    Access   |  +----------------+  |    Access   |  +----+
   | CE1|--|   Domain 1  |     |          |     |   Domain 3  |--| CE2|
   +----+  |  (Vendor B) |-----            -----|  (Vendor C) |  +----+
           +-------------+                      +-------------+


                      Figure 1. Multi-vendor Domains


   As an illustrative example, consider a multi-domain transport
   network consisting of three domains: one core converged packet-
   optical domain (Vendor A) and two access domains (Vendors B and C).
   Each access domain is managed by its domain control/management
   mechanism which is often a proprietary vendor-specific scheme. The
   core domain is also managed by Vendor A's proprietary
   control/management mechanism (e.g., EMS/NMS, OSS/BSS, Control Plane,
   SDN Controller, or any combination of these entities, etc.) that may
   not interoperate with access domain control/management mechanisms or
   at best partially interoperate if Vendor A is same as Vendor B or
   Vendor C.

   Due to these domain boundaries, facilitating end-to-end connections
   (e.g., Ethernet Virtual Connections, etc.) that traverse multi-
   domains is not readily achieved. These domain controls are optimized
   for its local operation and in most cases not suited for controlling
   the end-to-end connectivity services. For instance, the discovery of
   the edge nodes that belong to other domains is hard to achieve
   partly because of the lack of the common API and its information
   model and control mechanisms thereof to disseminate the relevant
   information.

   Moreover, the path computation for any on-demand end-to-end
   connection would need abstraction of dynamic network resources and
   ways to find an optimal path that meets the connection's service
   requirements. This would require knowledge of both the domain level
   dynamic network resource information and the inter-domain


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   connectivity information including domain gateway/peering points and
   the local domain policy.

   From an end-to-end connection provisioning perspective, in order to
   facilitate a fast and reliable end-to-end signaling, each domain
   operation and management elements should ideally speak the same
   control protocols to its neighboring domains. However, this is not
   possible for the current network context unless a folk-lift green
   field technology deployment with a single vendor solution would be
   done. Although each domain applies the same protocol for the data
   plane, an end-to-end connectivity traversing multiple vendor domains
   might not be provided due to a management and control mechanism
   focusing only on its own domain.

   In addition, the end-to-end connection provisioning via multiple
   domains might not be treated by a single layer but the control and
   management of multi-layer should be necessary. In this case, the
   control plane of an upper layer first interacts with its lower layer
   in order to check whether the lower layer can provide network
   resources to meet service-level requirements such as SLA (Service
   Level Agreement) and user-defined policies. Then, the upper layer
   could proceed to provision its own layer referring to provisioning
   results provided from its lower layer. However, vendor-specific
   management systems have no awareness of adjacent layers of network
   resources. Even, a single vendor management system covering multi-
   layer avoids the interaction with control planes of the multi-layer
   due to the complexity of implementation.

   From a network connectivity management perspective, it would require
   a mechanism to disseminate any connectivity issues from the local
   domain to the other domains whenever the local domain cannot resolve
   a connectivity issues. This is hard to achieve due to the lack of
   the common API and its agreed-upon information model and control
   mechanisms thereof to disseminate the relevant information.

   From an operation's perspective, the current network environments
   are not conducive to offering end-to-end connectivity services in
   multi-vendor domain transport networks. For instance, when the
   performance monitoring inquiry is requested, operators manually
   monitor each domain and aggregate the performance results. However,
   it may not be precise because of the different measurement timing
   employed by each domain.

2.1. Example A - Leased Line Services

   Service providers offer to customers a leased line service
   connecting geographically distant two or more locations.
   Traditionally, leased lines have been offered using SONET/SDH
   networks in speed ranging from E1 to STM64 to meet specific business

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   needs. But, as demand grew on data network, service providers
   started to offer Ethernet-based leased line services in speed
   ranging from 10Mbps and 10Gbps. Especially, MPLS-TP defined by IETF
   is mainly used to achieve the carrier-grade characteristics (high-
   level availability, guaranteed bandwidth, and OAM capabilities) of
   SONET/SDH.

   However, unlike the SONET/SDH networks, there are some limitations
   to provide an end-to-end connectivity on top of telco infrastructure
   with multi-vendor domains, because the EMS/NMS system of each vendor
   does not communicate with each other in order to operate the multi-
   vendor MPLS-TP networks due to the lack of common API. Each vendor
   devices can support the same OAM and protection mechanisms, but end-
   to-end connections are only created through data planes manually
   configured from operators. Operators should manually give specific
   MPLS label values to network elements acting as LSRs/LERs
   considering the collision of used label values. In addition, the
   exchange of specific OAM and protection switching information should
   be achieved for appropriate end-to-end OAM and protection switching
   operations. Even, it is hard to operate such kinds of connections
   because of network elements non-visible from each vendor's EMS/NMS
   system. As a result, operators might have difficulties in terms of
   execution of on-demand OAM functions and manual protection switching
   commands.

   To achieve an end-to-end connectivity, each vendor domain creates
   their own MPLS-TP tunnels by their EMS/NMS systems and then, MEF-
   based ENNIs are used at the interconnection links. But, this
   solution still requires manual configurations from operators for S-
   VLAN handling and various ENNI parameters (connectivity information,
   and bandwidth profile).

2.2. Example B - Data Center Interconnect (DCI)

   Enterprise customer data centers are consolidating, growing and
   becoming more redundant and dynamic. Thereby, service providers
   provide a new data center interconnect (DCI) service connecting
   geographically separate data centers to their customers to extend
   their computing resources or enhance the service availability
   between data centers or main sites.

   DCI supports two possible transport scenarios over metro and
   regional area networks.

   - DWDM or CWDM: This is a Layer 1 type of DCI service using optical
     WDM equipment between data centers to meet the highest bandwidth
     and lowest latency requirements. Depending on distance and
     capacity requirements between data centers, provider choose a
     short-reach CWDM or long-reach DWDM technology. Then, customers

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     are provided a private optical network using an optical
     wavelength.

   - L2VPN: This is a Layer 2 type of DCI service using Ethernet-based
     L2VPN technologies for customers requiring seamless LAN extension.
     Two kinds of L2VPN technologies are applicable where one is
     carrier Ethernet transport technology and another is L2VPN
     solutions based on IP/MPLS or overlay network technologies such as
     VxLAN, NVGRE or GRE. The Carrier Ethernet technology provides
     predictable performance in terms of various Ethernet services
     (i.e., E-Line, E-Tree, E-LAN) defined by MEF (Metro Ethernet
     Forum). In the meantime, L2VPN based on IP technologies cover less
     stringent latency and bandwidth requirements.

   The scenarios are mapped into networking technologies that can meet
   the underlying requirements. From the provider perspectives, the
   providers should support a number of different network technologies
   metro and regional area network between data centers in order for
   offering appropriate virtual private networks depending on the
   customer requirements. Unlike the case of Example A in this section,
   some of IP-based overlay solutions only provide SDN-based interface
   technologies such as NetConf, RestConf, OpenFlow and SNMP without
   any EMS/NMS systems. Therefore, it is necessary to implement an
   integration system for the control and management of the L1 and
   L2/L3 devices. Resource discovery and control throughout the
   multiple layers should be achieved in provider networks to offer
   more rapid service agility and efficiency of the DCI service.



3. Requirements

   In the previous section, we discussed the current challenges and
   issues that prevent operators from offering end-to-end connectivity
   services in multi-vendor domain transport networks.

   This section provides a high-level requirement for enabling end-to-
   end connectivity services in multi-vendor domain transport networks.

   Figure 2 shows information flow requirements of the aforementioned
   context.









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            +-------------------------------------------------+
            |                                                 |
            |         Customer On-demand Network Service      |
            |                                                 |
            +-------------------------------------------------+
                                    /|\
                                     |
                                    \|/
            +-------------------------------------------------+
            |                                                 |
            |               Abstracted Global View            |
            |                                                 |
            +-------------------------------------------------+
                                    /|\
                                     |
                                    \|/
            +-------------------------------------------------+
            |                                                 |
            |        Single Integrated E2E Network View       |
            |                                                 |
            +-------------------------------------------------+
                  /|\              /|\               /|\
                   |                |                 |
                  \|/              \|/               \|/
            +-------------+   +-------------+   +-------------+
            |             |   |             |   |             |
            |  Domain A   |   |  Domain B   |   |  Domain C   |
            | Control(NMS)|   | Control(NMS)|   | Control(Dev)|
            +-------------+   +-------------+   +-------------+


      Figure 2. Information Flow Requirements for Enabling End-to-End
       Network Connectivity Service in Multi-vendor Domain Networks

   There are a number of key requirements from Figure 2.

   - A single integrated end-to-end network view is necessary to be
     able to provision the end-to-end paths that traverse multiple
     vendor domains. In this approach the scalability and
     confidentiality problems are solved, but new considerations must
     be taken into account:

        o Limited awareness, by the VNC, of the intra-domain resources
          availability.

        o Sub-optimal path selection.



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   - The path computations shall be performed in two stages: first on
     the abstracted end-to-end network view (happening at VNC), and on
     the second stage it shall be expanded by each PNC.

   - In order to create a single integrated end-to-end network view,
     discovery of inter-connection data between domains including the
     domain border nodes/links is necessary. (The entity to collect
     domain-level data is responsible for collecting inter-connection
     links/nodes)

   - The entity to collect domain-level data should recognize
     interoperability method between each domain. (There might be
     several interoperability mechanisms according to technology being
     applied.)

   - The entity responsible to collect domain-level data and create an
     integrated end-to-end view should support push/pull model with
     respect to all its interfaces.

   - The same entity should coordinate a signaling flow for end-to-end
     connections to each domain involved. (This entity to domain
     control is analogous to an NMS to EMS relationship)

   - The entity responsible to create abstract global view should
     support push/pull model with respect to all its interfaces. (Note
     that the two entities (an entity to create an integrated end-to-
     end view and an entity to create an abstracted global view) can be
     assumed by the same entity, which is an implementation issue.

   - Hierarchical composition of integrated network views should be
     enabled by a common API between NorthBound Interface of the Single
     Integrated End-to-End view (handled by VNC) and Domain Control
     (handled by PNC).

   - There is a need for a common API between each domain control to
     the entity that is responsible for creating a single integrated
     end-to-end network view. At the minimum, the following items are
     required on the API:

        o Programmability of the API.

        o The multiple levels/granularities of the abstraction of
          network resource (which is subject to policy and service
          need).

        o The abstraction of network resource should include customer
          end points and inter-domain gateway nodes/links.

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        o Any physical network constraints (such as SRLG, link
          distance, etc.) should be reflected in abstraction.

        o Domain preference and local policy (such as preferred peering
          point(s), preferred route, etc.)

        o Domain network capability (e.g., support of push/pull model).

   - The entity responsible for abstraction of a global view into a
     customer view should provide a programmable API to allow the
     flexibility. Abstraction might be provided by representing each
     domain as a virtual node (node abstraction) or a set of virtual
     nodes and links (link abstraction). Node abstraction creates a
     network topology composed by nodes representing each network
     domain and the inter-domain links between the border nodes of each
     domain.

        o Abstraction of a global view into a customer view should be
          provided to allow customer to dynamically request network on-
          demand services including connectivity services.

        o What level of details customer should be allowed to view
          network is subject to negotiation between the customer and
          the operator.



4. References

   [ACTN-Frame] D. Ceccarelli, L. Fang, Y. Lee and D. Lopez, "Framework
             for Abstraction and Control of Transport Networks," draft-
             ceccarelli-actn-framework, work in progress.

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

   [ACTN-Req] Y. Lee, D. Dhody, S. Belotti, K. Pithewan, D. Ceccarelli,
             "Requirements for Abstraction and Control of Transport
             Networks", draft-lee-teas-actn-requirements, work in
             progress.


5. Acknowledgement

   The authors wish to thank Young Lee for the discussions in the
   document.


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6. Contributors

Authors' Addresses

   Kwang-koog Lee

   KT
   Email: kwangkoog.lee@kt.com

   Hosong Lee

   KT
   Email: hosong.lee@kt.com

   Ricard Vilalta
   CTTC
   Email: ricard.vilalta@cttc.es

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

























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