DetNet H. Wang
Internet Draft P. Wang
Intended status: Standards Track C. Zhang
Expires: December 11, 2018 Y. Yang
Chongqing University of
Posts and Telecommunications
June 9, 2018
Joint Scheduling Architecture for Deterministic Industrial
Field/Backhaul Networks
draft-wang-detnet-backhaul-architecture-03
Abstract
The joint scheduling between industrial field network and backhaul
network is important to satisfy the requirements of deterministic
delay for data flows in factories. This document describes a joint
scheduling architecture for deterministic industrial field/backhaul
networks. Taking WIA-PA, an international standard about industrial
wireless field network, and IPv6-based backhaul network as an
example, this document depicts how the joint scheduling architecture
works in detail.
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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
3.4. Bandwidth guarantee method ............................ 13
4. Security Considerations .................................... 13
5. IANA Considerations ........................................ 13
6. References ................................................. 13
6.1. Normative References .................................. 13
6.2. Informative References ................................ 13
Authors' Addresses ............................................ 15
1. Introduction
Deterministic transmission is one of essential elements of
industrial network. Thus, applying deterministic network into the
whole industrial network has attracted a lot of attention recently.
Deterministic network is also focused on the industrial field
networks, such as ISA100.11a [IEC62734], WirelessHART [IEC62591] and
WIA-PA [IEC62601]. Most industrial field networks are in a middle or
small size, and the network coverage is constant. Therefore, An
industrial backhaul network is needed to connect different types of
industrial field networks. Meanwhile, the deterministic transmission
of the industrial backhaul network should also be guaranteed.
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However, there are little considerations about joint scheduling
between industrial backhaul network and industrial field network.
The emerging Software Defined Networks (SDN) technology on the
Internet brings a new choice to solve joint scheduling problem. SDN
has been proposed as a new network architecture in recent years. The
network architecture separates the network control plane from the
forwarding plane, which brings a revolution for the network
architecture. By separating control plane from forwarding plane ,and
the open communication protocol, SDN breaks the closure of
traditional network device provider. Besides, open interfaces and
free programmability also make network management more efficient and
flexible.
In document [I-D.bas-usecase-detnet] and [I-D.finn-detnet-
architecture] submitted by the IETF DetNet working group,
deterministic network based on Ethernet has been researched already.
They propose a network architecture based on SDN technology that can
accurately control the transmission of data streams. However, the
characteristics of the industrial backhaul network and the actual
condition of industrial field deterministic networks are not
considered. Firstly, the data that transmits in industrial backhaul
network is highly sensitive to transmission delay. Secondly, the
existing deterministic networks have been widely deployed in
industrial field environment, thus the direct replacement for
original networks will consume many workers and material resources.
Based on existing research in document [I-D.finn-detnet-
architecture], this document proposes a joint scheduling
architecture for deterministic industrial networks. It will firstly
replace the industrial backhaul networks and other non-deterministic
networks located in industrial networks with deterministic Ethernet
network. Then this document proposes a joint scheduler based on SDN
technology. By deploying the deterministic network in complete
industrial network, it can realize the end-to-end deterministic
scheduling between different industrial field networks.
2. Joint Scheduling Architecture
There are many types of network controllers in industrial networks,
which constitute the control plane of the whole industrial network
together. The control plane is very important in the entire network,
especially when it refers to cross-domain transmission of time-
sensitive data. The control plane architecture affects the
performance of the network greatly. It is becoming a hot research on
how to give full play to the performance of their respective
networks when multiple controllers are in the joint work.
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However, there is no unified standard for the joint architecture of
multiple controllers in the industry presently. The mainstream of
architecture includes distributed architecture and centralized
architecture.
2.1. Distributed Architecture
Distributed architecture is known as East-West architecture. In the
architecture, the status of all network controllers are equal, these
controllers connect with each other to form an unstructured network,
and implement cross-domain transmission task by exchanging
information, as shown in Figure 1.
+------------------------------------------------------+
| |
Application +--------+ +--------+ +-------+ |
Plane | APP | | APP | | APP | |
| +----+---+ +----+---+ +---+---+ |
| | | | |
+--------+-----------------+------------------+--------+
| | |
----------------------------------------------------------------
| | |
+-------+-----------------+------------------+--------+
| | | | |
Control | +----+-----+ +----+-----+ +----+-----+ |
Plane | |Controller|----->|Controller|------>|Controller| |
| | |<-----| |<------| | |
| +----------+ +----------+ +----------+ |
| | | | |
+-------+-----------------+-------------------+-------+
| | |
----------------------------------------------------------------
| | |
+----+-----+ +----+-----+ +----+-----+
Forwarding | WIA-PA |----->| backhaul |------->| WIA-PA |
Plane | network |<-----| network |<-------| network |
+----------+ +----------+ +----------+
Figure 1. Distributed Architecture
In distributed architecture, controller can exchange different network
topologies and the accessibility of information by east-west interface,
and each controller can establish a global network topology. From a
global network perspective, each controller is equal, thus it can serve
as a server role as well as the ability to start deterministic cross-
network transmission task.
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2.2. Centralized Architecture
Centralized architecture is also called a vertical multi-level
architecture. In this architecture, the control plane is divided
into two parts, one part is the basic control plane, which is
composed of a variety of network controllers, and another is a main
network controller, which is responsible for controlling the basic
control plane. The detailed description of centralized architecture
is 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 does not need to expand east-west
interface. It only needs to establish a connection with the basic
controllers using southbound interface. After the connection is
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established, the main controller obtains the every topology of
network domain by the API interface provided by the basic
controllers, and storages global network topology. Main controller
can also assign tasks to basic controllers by API interface.
2.3. Joint Scheduling Architecture
In 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, can it ensure the deterministic control of
whole network.
For deterministic industrial network, the scale of network is not
very large. Besides, in industrial backhaul network, a single SDN
controller is sufficient to meet the demands of control. If
centralized architecture is directly applied to an industrial
network, it will not only be unable to make full use of advantages
of the multi-controller architecture, but also cause unnecessary
information interaction between controllers wasting network resource.
Considering the problems existing in above two architectures, this
document proposes a joint scheduling architecture based on the
architecture document [I-D.finn-detnet-architecture]. The
architecture is a semi-distributed structure in which the main
controller can manage and control the basic controller, but the
basic controller also has local network management capabilities, and
the east-west interface between the controllers is also reserved.
The joint scheduling architecture is optimized according to the
characteristics of deterministic industrial network. A single SDN
controller can unite the WIA-PA network system manager to manage the
entire industrial network, and provide support for the deterministic
scheduling of cross-network data transmission through industrial
backhaul network located in different WIA-PA networks.
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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
Figure 3 depicts the joint scheduling architecture. The architecture
can be mainly classified into three planes:
o Forwarding plane: this plane contains various types of network
equipment belonged to different networks. It is the physical
entities for network transmission. To obtain the desired network
functions from network manager, devices should abstract their own
resources to provide to its network manager respectively.
o Control plane: this plane is composed by WIA-PA system manager
and SDN controller. Joint scheduler is integrated into the SDN
controller by a way of plugin, and other WIA-PA system managers
communicate with joint scheduler by establishing a connection
with the SDN controller. Meanwhile, joint scheduler implement the
management of industrial backhaul network by directly invoking
the corresponding module of SDN controller.
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o Application plane: this plane provides users with a unified
interface about many variety of resources for the whole network.
At the same time, it also provides an intuitive and user-friendly
interface, which shields the complex network information of the
original.
When application plane triggers a joint scheduling task, SDN
controller calculates path and allocates resource according to the
task request from the application plane. Upon finishing calculation,
SDN controller sends them using the unified joint scheduling
interface to corresponding network manager, and then the network
manager sends them to the industrial field network.
Based on joint scheduling architecture, joint scheduler can realize
control and scheduling for the entire industrial network, thus it
can provide a real-time guarantee for each data stream.
3. Joint Scheduling Scheme
Taking WIA-PA network and IPv6-based backhaul network as an example,
this section describes how the joint scheduling architecture works.
Existing WIA-PA scheduling scheme only applies to WIA-PA field
network. Scheduling scheme will fail once data transfers to backhaul
networks. Joint scheduling scheme is an innovation and expansion
compared to WIA-PA scheduling scheme.
Firstly, in order to enable WIA-PA data to be transmitted and
identified in industrial backhaul networks, joint scheduling scheme
need to support deterministic scheduling to industrial backhaul
networks.
Secondly, by conducting an optimization for original WIA-PA
scheduling scheme, original scheduling scheme can work with joint
scheduler, and simultaneously be applied to cross-domain network.
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, due to system manager allocates short address to field
device based on WIA-PA network address information independently.
Thus the short address of field device in entire industrial network
is uncertain. In order to identify the field device belonged to
different network domains, the network identifier (PAN_ID) is
applied to the joint scheduling scheme to identify different WIA-PA
networks.
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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 path 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 joint scheduling process, the joint scheduler communicates with
WIA-PA system manager by invoking the east-west interfaces to
implement route deployment and resource allocation to the WIA-PA
network. The system manager will configure communication resources
for the corresponding gateway device, router and field equipment
when it receives configuration commands from joint scheduler. Then
the system manager constructs a reply message based on the relevant
network information and returns it to the joint scheduler by the
east-west interface. It is worth noting that both the WIA-PA system
manager and the joint scheduler need to support the parsing and
construction of network messages in the east-west interface.
3.2. Protocol Conversion
For cross-domain transmission, industrial backhaul network is
different from WIA-PA network which is not an IP-based Ethernet.
Protocol conversion for WIA-PA packet in gateway is needed when data
generated from WIA-PA network needs to transmit to another field
network through industrial backhaul. In this scheme, the WIA-PA
gateway will translate the WIA-PA frames into IPv6 packets, and fill
the VCR of WIA-PA frames and the priority information into the IPv6
header. Meanwhile, according to the joint scheduling scheme, joint
scheduler is able to recognize the WIA-PA data stream and allocate
resources according to the types of WIA-PA frame.
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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 process of protocol conversion in gateway
As shown in Figure 4, the WIA-PA gateway will receive the address
mapping configuration command from joint scheduler. Then VCR tables
and IPv6 address-mapping tables will be formed according to this
information. When gateway receives WIA-PA packets, it will firstly
parse 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, gateway begins to encapsulate WIA-PA packets based on IPv6
format, fill VCR_ID in IPv6 header flow label field and the priority
of WIA-PA packet in IPv6 header fields.
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When receiving IPv6 packets from industrial backhaul networks,
gateway will recognize VCR_ID from IPv6 packet header, and obtain
packet VCR according to the VCR ID in VCR table, then replace it
with the information of original packet.
3.3. Industrial Backhaul Network Scheduling
In deterministic network based on SDN, in order to achieve
communication with gateway, joint scheduler needs to configure the
paths for SDN switches in the industrial backhaul network. Meanwhile,
joint scheduler can classify different types of WIA-PA data streams
by matching IPv6 flow label field. Meanwhile, according to the
priority information in IPv6 header field and VCR_ID type, joint
scheduling can allocate the necessary resources to communication and
ensure that important data flow is not affected when adding new data
flows in existing network. It can also monitor the real-time data
flow. To guarantee the real-time performance of critical data flows,
redundant paths are 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
When receiving the request for service, the joint scheduler will
calculate route information and resource allocation. Once the path
and resource allocation are determined, joint scheduling will
confirm whether the resource and path are capable of meeting
business requirements by the inside module of SDN controller. If it
meets, then the flow table is deployed by SDN controller. Otherwise,
the path information and resource allocation are recalculated to
choose the correct paths to transmit data flow.
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3.4. Bandwidth guarantee method
Bandwidth guarantee method is implemented on the basis of joint
scheduling mechanism, in order to solve the problem that industrial
backhaul networks can not identify fine-grained and cross-network
data transmission. By filling the priority information and the
RouteID defined in WIA-PA network into the IPv6 header, the SDN
controller can not only identify cross-network transmission of the
WIA-PA data stream, but also obtain priority information about the
WIA-PA data stream. In industrial backhaul network, the SDN switch
employs the mechanism of priority queue to allocate network
bandwidth. Thus SND switch can distribute WIA-PA data streams into
corresponding queues of ports according to the received flow table
from SDN controller. Therefore, the bandwidth of data stream is
guaranteed.
By using the above methods, joint scheduling mechanism can
distinguish data streams in a fine-grained way and guarantee
bandwidth when data transmits in industrial backhaul network. For
example, real-time data in WIA-PA network is sensitive to delay,
thus it should be allocated more bandwidth to reduce transmission
delay. For not urgent data, it can be assigned less bandwidth to
reserve bandwidth for real-time data. Meanwhile, SDN controller can
flexibly adjust bandwidth allocation strategy to relieve network
congestion.
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>.
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[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-05 (work in
progress), March 2016.
[I-D.finn-detnet-architecture]
Finn, N., Thubert, P., and M. Teener, "Deterministic
Networking Architecture", draft-finn-detnet-architecture-08
(work in progress), August 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), October 2015.
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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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