Joint Scheduling Architecture for Deterministic Industrial Field/Backhaul Networks
draft-wang-detnet-backhaul-architecture-00
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draft-wang-detnet-backhaul-architecture-00
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
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This Internet-Draft will expire on June 22, 2017.
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Copyright Notice
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This document is subject to BCP 78 and the IETF Trust's Legal
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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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