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DetNet                                                         H. Wang
Internet Draft                                                 P. Wang
Interned status: Standards Track                              C. Zhang
Expires: June 22, 2017                                         Y. Yang
                                               Chongqing University of
                                          Posts and Telecommunications
                                                     December 19, 2016


         Joint Scheduling Architecture for Deterministic Industrial
                          Field/Backhaul Networks
                draft-wang-detnet-backhaul-architecture-00


Abstract

   Joint scheduling of industrial field network and backhaul network is
   significant for end-to-end deterministic delay requirements of data
   flows in factories. This document describes a joint scheduling
   architecture for deterministic industrial field and backhaul
   networks. Taking WIA-PA wireless field network and IPv6-based
   backhaul network as an example, this document shows how the joint
   scheduling architecture works.

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
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   This Internet-Draft will expire on June 22, 2017.





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Copyright Notice

   Copyright (c) 2016 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
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   warranty as described in the Simplified BSD License.

Table of Contents


   1. Introduction ................................................ 2
   2. Joint Scheduling Architecture................................ 3
      2.1. Distributed Architecture................................ 4
      2.2. Centralized Architecture................................ 5
      2.3. Joint Scheduling Architecture........................... 6
   3. Joint Scheduling Scheme...................................... 8
      3.1. WIA-PA Network Joint Scheduling ........................ 9
      3.2. Protocol Conversion..................................... 9
      3.3. Industrial Backhaul Network Scheduling ................ 11
   4. Security Considerations..................................... 13
   5. IANA Considerations ........................................ 13
   6. References ................................................. 13
      6.1. Normative References................................... 13
      6.2. Informative References................................. 13

1. Introduction

   Deterministic network is an essential element of the industrial
   network. Using deterministic network in the industrial field can
   enhance the network performance and greatly reduce the network
   packet loss. Thus, it is the future development direction of
   industrial network technology to use deterministic networks in the
   whole industrial network. Deterministic networks in industrial
   networks are mainly concentrated on the industrial field networks,
   such as ISA100.11a[IEC62734], WirelessHART[IEC62591] and WIA-
   PA[IEC62601], and there is little joint scheduling scheme that can
   be applied to industrial networks.




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   Nowadays, in the use case document[draft-bas-usecase-detnet] and
   architecture document[draft-finn-detnet-architecture] submitted by
   the IETF DetNet working group, a deterministic network based on
   Ethernet has already been researched. The document proposes a
   network architecture based on SDN technology, which can accurately
   control the transmission of data streams. However, the document does
   not consider the characteristics of the industrial backhaul networks
   and the actual situation of other industrial field deterministic
   networks. First of all, the data flow of industrial backhaul network
   is highly sensitive to the uncertainty of time. Therefore, it is
   very important that how to apply the deterministic networks based on
   Ethernet to industrial backhaul networks. Secondly, the existing
   deterministic networks in the industrial field have been widely
   deployed in the factory, and Deterministic network technology is
   already very mature, and direct replacement will consume a lot of
   manpower and material resources.

   Based on existing work in the architecture document[draft-finn-
   detnet-architecture], this document proposes a joint scheduling
   architecture for deterministic industrial field networks. This
   framework will firstly replace the industrial backhaul networks and
   other non-deterministic networks of industrial networks into
   deterministic Ethernet-based network, and then on the basis of SDN
   technology, this document proposes a joint scheduler, which can be
   used for joint scheduling on other deterministic networks in
   deterministic Ethernet-based network and industrial field network.
   Through deploying the deterministic network throughout the
   industrial network based on the joint scheduling architecture, it
   can realize the end-to-end deterministic scheduling between
   different industrial field networks, and ensure data stream
   indicators as well as save manpower and material resources.

2. Joint Scheduling Architecture

   For industrial networks, there are many network controllers in the
   network, which together constitute the control plane for the whole
   industrial network. The control plane is very important in the
   entire network, especially when it comes to cross domain transfer of
   time-sensitive data. So the control plane architecture will greatly
   affect the performance of the network, therefore it is becoming a
   research hotspot on how to give full play to the performance of
   their respective networks when the multiple controllers are in the
   joint cooperation. However, there is not a unified standard of joint
   architecture of multiple controllers in the industry at present. The
   main frameworks are the following two kinds: the distributed
   architecture and the centralized architecture. The WIA-PA network,
   which is the typical of WSNs standards which has become an


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   international standard for industrial field networks approved by IEC,
   is used as an example to illustrate these architectures.

2.1. Distributed Architecture

   Distributed architecture is also known as East-West architecture. In
   the architecture, the status of all network controller is equal,
   these controllers are connected to each other to form an
   unstructured network, and achieve cross domain transfer task
   deployment through the mutual transmission of information, as shown
   in Figure 1.

   In the distributed architecture, the controller can exchange
   different network topologies and the accessibility of information
   through the east-west interface, and each controller can build a
   global network topology. In the access to the global network
   topology, since each controller is equal, it can serve as a server
   role at the same time, as well as has the service capacity of
   starting deterministic cross-network transmission.

             +-------------------------------------------------------------+
             |                                                             |
Application  |     +--------+         +--------+          +-------+        |
Plane        |     |   APP  |         |   APP  |          |  APP  |        |
             |     +----+---+         +----+---+          +---+---+        |
             |          |                  |                  |            |
             +----------+------------------+------------------+------------+
                        |                  |                  |
   ---------------------------------------------------------------------------------
                        |                  |                  |
             +----------+------------------+------------------+------------+
             |          |                  |                  |            |
Control      |     +----+-----+       +----+-----+       +----+-----+      |
Plane        |     |Controller|------>|Controller|------>|Controller|      |
             |     |          |<------|          |<------|          |      |
             |     +----------+       +----------+       +----------+      |
             |          |                  |                  |            |
             +----------+------------------+------------------+------------+
                        |                  |                  |
   ---------------------------------------------------------------------------------
                        |                  |                  |
                   +----+-----+       +----+-----+       +----+-----+
Forwarding         |  WIA-PA  |------>| backhaul |------>|  WIA-PA  |
Plane              |  network |<------|  network |<------|  network |
                   +----------+       +----------+       +----------+
                   Figure 1. Distributed Architecture



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2.2. Centralized Architecture

   Centralized architecture is also known as vertical multi-level
   architecture. In this architecture, the control plane is divided
   into two parts, one is the basic control plane composed of a variety
   of network controllers; another part is a network controller
   composed of the main controller, which is responsible for
   controlling the basic control plane, as shown in Figure 2.

             +-------------------------------------------------------------+
             |                                                             |
Application  |     +--------+         +--------+          +-------+        |
Plane        |     |   APP  |         |   APP  |          |  APP  |        |
             |     +--------+         +----+---+          +-------+        |
             |                             |                               |
             +-----------------------------+-------------------------------+
                                           |
      --------------------------------------------------------------------------------
                                           |
             +-----------------------------+-------------------------------+
             |                             |                               |
             |                      +------+-----+                         |
             |          +-----------|    Main    |------------+            |
             |          |           | Controller |            |            |
Control      |          |           +------+-----+            |            |
Plane        |          |                  |                  |            |
             |     +----+-----+       +----+-----+       +----+-----+      |
             |     |Controller|       |Controller|       |Controller|      |
             |     +----+-----+       +----+-----+       +----+-----+      |
             |          |                  |                  |            |
             +----------+------------------+------------------+------------+
                        |                  |                  |
      --------------------------------------------------------------------------------
                        |                  |                  |
                   +----+-----+       +----+-----+       +----+-----+
Forwarding         |  WIA-PA  |------>| backhaul |------>|  WIA-PA  |
Plane              |  network |<------|  network |<------|  network |
                   +----------+       +----------+       +----------+

                   Figure 2. Centralized Architecture


   The centralized architecture needn't to expand the east-west
   interface. It only needs to establish a connection with the basic
   controllers through the southbound interface. After the connection


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   is established, the main controller obtains the every domain network
   topology through the API interface provided by the basic controllers,
   and storages global network topology on its own. It can also assign
   tasks to basic controllers through the API interface.


2.3. Joint Scheduling Architecture

   In the practical application, distributed architecture not only
   needs to extend the east-west interface, but also maintains a global
   network topology in each controller. Only each controller maintains
   such a global network topology, it can ensure the deterministic
   control of the control plane for the whole network.

   Though the centralized architecture does not have the above
   requirements, for the deterministic industrial network, the scale of
   the network is not very large, in the industrial backhaul network, a
   single SDN controller is sufficient to meet the control demands of
   industrial backhaul network. If centralized architecture is directly
   applied to an industrial network, it will not only be unable to give
   full play to the advantages of the architecture in multi controllers
   collaboration, but also cause meaningless information interaction
   between the controllers, which will waste network resource.

   In view of the problems existing in these two architectures, this
   document takes the WIA-PA network as an example and proposes a joint
   scheduling architecture based on the architecture document[draft-
   finn-detnet-architecture]. The architecture is optimized according
   to the characteristics of deterministic industrial network, so that
   a single SDN controller can unite the WIA-PA network systems manager
   to manage the entire industrial network, and provide support for the
   deterministic scheduling of data streams across network transmission
   through industrial backhaul network located in different domains of
   WIA-PA network.














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             +-------------------------------------------------------------+
             |                                                             |
Application  |     +--------+         +--------+          +-------+        |
Plane        |     |   APP  |         |   APP  |          |  APP  |        |
             |     +--------+         +----+---+          +-------+        |
             |                             |                               |
             +-----------------------------+-------------------------------+
                                           |
   ---------------------------------------------------------------------------------------
                                           |
             +-----------------------------+-------------------------------+
             |                             |                               |
Control      |  +--------------+      +----+-----+      +--------------+   |
Plane        |  |    WIA-PA    |------|   SDN    |------|   WIA-PA     |   |
             |  |System Manager|      |Controller|      |System Manager|   |
             |  +------+-------+      +----+-----+      +-------+------+   |
             |         |                   |                    |          |
             +---------+-------------------+--------------------+----------+
                       |                   |                    |
   ---------------------------------------------------------------------------------------
                       |                   |                    |
                  +----+-----+        +----+-----+        +-----+----+
Forwarding        |  WIA-PA  |------->| backhaul |------->|  WIA-PA  |
Plane             |  network |<-------| network  |<-------|  network |
                  +----------+        +----------+        +----------+

                  Figure 3. Joint scheduling architecture

   As shown in Figure 3, joint scheduling architecture can be mainly
   classified into three planes:

   o Forwarding plane: this plane contains various types of network
      equipment in different networks. It is the physical entities of
      the network transmission. In general, to achieve the desired
      network functions for the network manager, these devices are
      specific factors of management control operation, which makes
      their own resources abstract for their own control elements to
      manage and configure.

   o Control plane: this plane is formed by the WIA-PA System Manager
      and the SDN controller. Joint scheduler is integrated into the
      SDN controller in the form of plugin, and other WIA-PA System
      Managers accept joint management scheduler by establishing a
      connection with the SDN controller. Meanwhile, inside the SDN
      controller, joint scheduler achieves the management of industrial
      backhaul network by directly calling the corresponding module of
      SDN controller.


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   o Application plane: this plane provides users with a unified
      interface about a variety of resources for the whole network. At
      the same time, it also provides users with an intuitive, user-
      friendly interface, which can shield the complex network
      information of the original.

   Joint Scheduling Architecture defines an architecture that when
   industrial networks contain other deterministic networks, these
   deterministic networks and deterministic Ethernet-based networks are
   jointly scheduling. On the basis of this architecture, control and
   scheduling for the entire industrial network can be realized by
   joint scheduler, so as to provide a real-time protection for each
   data stream.

3.  Joint Scheduling Scheme

   Taking WIA-PA wireless field network and IPv6-based backhaul network
   as an example, this section shows how the joint scheduling
   architecture works. Existing WIA-PA scheduling scheme only applies
   to WIA-PA field network. Scheduling scheme will fail once the data
   is transferred to backhaul networks. Joint scheduling scheme is
   innovation and expansion of WIA-PA scheduling scheme.

   Firstly, scheduling scheme based on SDN in industry backhaul network
   is added to the original scheduling scheme, so that data can flow in
   the industrial backhaul network, and the data can be identified and
   assigned existing backhaul network resource according to their
   requirements for the network resources.

   Secondly, conducting an optimization for original WIA-PA scheduling
   scheme enables scheduling scheme based on WIA-PA networks plays
   together joint scheduler, and scheduling scheme can simultaneously
   apply to two non-adjacent domains so that it can be adapt to the
   cross-border joint operation based on SDN.

   Thirdly, due to the specificity of cross-border transmission
   services, the joint scheduling scheme for WIA-PA network VCR_ID and
   Route ID is reclassified.

   Finally, since the system manager allocates a short address to the
   field device on the basis of the network address information about
   its own domain in WIA-PA networks. Thus resulting in the entire
   network short address field device is uncertain. In order to
   identify the field device on different network domains and domain,
   the network identifier (PAN_ID) is applied to the joint scheduling
   scheme to identify WIA-PA network.



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   After the SDN controller initiates joint scheduling module, WIA-PA
   system manager will actively establish a connection with the united
   scheduler. After the scheduler receives a cross-border transmission
   request, joint scheduler will send a request for obtaining topology
   information and node information to WIA-PA System Manager. Then, the
   scheduler will assign paths and network resources according to this
   information by pre-defined scheduling algorithm.

   After the routing and network resources have been calculated, joint
   scheduler will configure and deploy networks by the corresponding
   network controller.

3.1. WIA-PA Network Joint Scheduling

   In the united scheduling process, path deployment and resource
   allocation for WIA-PA network are performed by calling the WIA-PA
   network system manager API interface. System manager will query the
   corresponding information of the field device in the network upon
   receiving the acquisition command of joint operation for the network
   information, and then return the received information to the united
   scheduler. The system manager will configure communication resources
   for the corresponding gateway device, routing equipment and field
   equipment if the system manager receives configuration commands from
   joint scheduler. After receiving a successful response, it will send
   a successful reply to the united scheduler.

3.2. Protocol Conversion

   In the process of cross-border transmission, since industrial
   backhaul network is different from WIA-PA network, which is not an
   IP-based Ethernet. Protocol conversion of gateway for WIA-PA packet
   is needed when the data of WIA-PA network needs to transmit to
   another network through cross-border industrial backhaul. Meanwhile,
   according to the joint scheduling scheme, SDN controller is able to
   identify the WIA-PA Ethernet data stream, and allocate resources
   according to the data stream type and level of the data stream.
   Therefore, in the protocol conversion process of gateway, scheduling
   and control of WIA-PA data flow can be realized by SDN controller
   unless the VCR of WIA-PA data stream and the priority are filled in
   the IPv6 header.








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         +-------+
         | Start |
         +-------+
             |
      +-------------+
      |  Receiving  |
      |data packets |
      +-------------+
             |
      /-------------\           +--------------+
     /Whether is the \          | Forwarded to |
     |  management   |-- Yes -->|  the system  |
     \     data      /          |    manager   |
      \-------------/           +--------------+
             |
            No
             |
       +-----------+
       | Resolution|
       |   Packet  |
       +-----------+
             |
       /------------\             /------------\          +-------------+
      /   Find the   \           /   Find the   \         | Encapsulate |
      |corresponding |-- Yes -->| corresponding |-- Yes-->|   and sent  |
      \     VCR      /           \ IPv6 address /         |  IPv6 packet|
       \------------/             \------------/          +-------------+
             |                           |                        |
             No                          No                       |
             |                           |                        |
         +--------+                      |                        |
         |  End   |<---------------------+------------------------+
         +--------+

            Figure 4. The conversion process of gateway protocol

   As shown in Figure 4, according to the above section, the gateway
   will receive the address mapping of joint scheduler configure when
   configuration WIA-PA network. After that, VCR tables and IPv6
   address-mapping tables will be formed according to this information.
   When the gateway receives WIA-PA packets, it will firstly parse out
   Route ID, Object ID and Instance ID, and find corresponding VCR from
   VCR tables. Meanwhile, the gateway finds the corresponding IPv6
   address according to Route ID in IPv6 address mapping table. Then,
   the gateway begins to encapsulate WIA-PA packets based on IPv6
   format, fill VCR_ID in IPv6 header flow label field, and fill the
   priority of WIA-PA packet in communication category of IPv6 header


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   fields, zero is used to fill up insufficient bytes. Then, the
   protocol conversion for WIA-PA data is completed.

   When the gateway receives IPv6 packets from the industrial backhaul
   networks, the gateway will make out VCR_ID from IPv6 packet header,
   and find packets VCR in the domain WIA-PA network according to the
   VCR ID in its own maintenance VCR table, and replace it with the
   information of original packet. Then, the protocol conversion for
   IPv6 packet is completed.

3.3. Industrial Backhaul Network Scheduling

   In deterministic network based on SDN, joint scheduler can recognize
   WIA-PA data stream through matching on IPv6 flow label field.
   According to priority of IPv6 and VCR_ID type, joint scheduling can
   allocate the necessary resources to communication, and ensure that
   the key data flow is not affected when adding new data flow in the
   existing network. It can also monitor the real-time data flow of the
   network. To protect critical data flows from affected, switching
   paths is also considered when necessary. The scheduling process of
   industrial backhaul network is shown in Figure 5.



























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                  +-------+
                  | Start |
                  +-------+
                      |
               +--------------+
               |Obtain network|
               |   topology   |
               +--------------+
                      |
            +-------------------+
            |    Calculate the  |
            | path and allocates|<----------------+
            |    resources      |                 |
            +-------------------+                 |
                      |                           |
                +----------+                      |
                |Query path|                      |
                +----------+                      |
                      |                           |
              /---------------\         +----------------+
             /whether the path \        |  Calculate the |
             |meets the resource|- No ->|   weight and   |
             \  requirements   /        | adjustment path|
              \---------------/         +----------------+
                      |
                      Yes
                      |
                +------------+
                | Deployment |
                | flow table |
                +------------+
                      |
                   +-----+
                   | End |
                   +-----+

      Figure 5. The scheduling process of Industrial backhaul network

   After receiving the request for service, the joint scheduler will
   calculate the route information and network resource allocation.
   Once the path information and resource allocation are determined,
   joint dispatcher will confirm whether the resource path is capable
   of meeting business requirements through the inside module of SDN
   controller. If it meets business requirements, then the flow table
   is deployed by SDN controller. Otherwise, the path information and
   resource allocation are recalculated to choose the other paths to
   transmit data flow.


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4. Security Considerations

5. IANA Considerations

   This memo includes no request to IANA.

6. References

6.1. Normative References

6.2. Informative References

[IEC62734]
           ISA/IEC, "ISA100.11a, Wireless Systems for Automation,
           also IEC 62734", 2011, <http://www.isa100wci.org/enUS/
           Documents/PDF/3405-ISA100-WirelessSystems-Future-brochWEB-
           ETSI.aspx>.

[IEC62591]
           IEC, "Industrial Communication Networks -
           Wireless Communication Network and Communication Profiles
           - WirelessHART - IEC 62591", 2010,
           <https://webstore.iec.ch/p-
           preview/info_iec62591%7Bed1.0%7Den.pdf>

[IEC62601]
           IEC, "Industrial networks - Wireless communication network
           and communication profiles - WIA-PA - IEC 62601", 2015, <
           https://webstore.iec.ch/preview/info_iec62601%7Bed2.0%7Db.pdf>

[I-D.finn-detnet-problem-statement]
           Finn, N. and P. Thubert, "Deterministic Networking Problem
           Statement", draft-finn-detnet-problem-statement-04 (work in
           progress), October 2015.

[I-D.finn-detnet-architecture]
           Finn, N., Thubert, P., and M. Teener, "Deterministic
           Networking Architecture", draft-finn-detnetarchitecture-03
           (work in progress), March 2016.

[I-D.bas-usecase-detnet]
           Kaneko, Y., Toshiba and Das, S, "Building Automation Use
           Cases and Requirements for Deterministic Networking", draft-
           bas-usecase-detnet-00 (work in progress), April 2016.





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Authors' Addresses

   Heng Wang
   Chongqing University of Posts and Telecommunications
   2 Chongwen Road
   Chongqing, 400065
   China

   Phone: (86)-23-6248-7845
   Email: wangheng@cqupt.edu.cn


   Ping Wang
   Chongqing University of Posts and Telecommunications
   2 Chongwen Road
   Chongqing, 400065
   China

   Phone: (86)-23-6246-1061
   Email: wangping@cqupt.edu.cn


   Chang Zhang
   Chongqing University of Posts and Telecommunications
   2 Chongwen Road
   Chongqing, 400065
   China

   Phone: (86)-23-6246-1061
   Email: zc910522@126.com


   Yi Yang
   Chongqing University of Posts and Telecommunications
   2 Chongwen Road
   Chongqing, 400065
   China

   Phone: (86)-23-6246-1061
   Email: 15023705316@163.com









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