CN106911593A - A kind of industrial control network array dispatching method based on SDN frameworks - Google Patents

Abstract

The invention provides a kind of industrial control network array dispatching method based on SDN frameworks.Carry out integrated data processing present invention incorporates time triggered and event trigger mechanism.Two major classes are splitted data into, a class is requirement of real-time highest industry control message；Another kind of refers to other data in industrial network, including audio, video and common monitoring data etc., and for every kind of data set priority.Odd even time triggered window is set, and alternately open, when primary sources window is opened can only transmission of control signals, the priority low transmission data high when secondary sources window is opened according to different types of data, wherein background data follows transmission mechanism of doing one's best.The design of time triggered window size concerns the performances such as the packet loss of data transfer time delay and whole network, therefore it is most important to set rational window size.The present invention has ensured the real-time and reliability of the industrial control network based on SDN frameworks.

Description

A Queue Scheduling Method for Industrial Control Networks Based on SDN Architecture

technical field

The invention relates to the field of industrial real-time control networks, in particular to an SDN architecture-based industrial control network queue scheduling method.

Background technique

With the rapid development of control, communication, network and other technologies, industrial control network technology has developed rapidly, covering not only a single factory, but also focusing on the field control of the factory to the comprehensive management of the enterprise. The web brings new technical challenges. At the same time, with the development of Internet technology, software-defined network (SDN) is more and more widely used, and an SDN-based industrial control network architecture has attracted more and more attention from the industry.

There are many types of data in the next-generation industrial network, including control data, audio data, video data, monitoring data and other background data. Each type of data has different real-time requirements, and it is necessary to propose a real-time guarantee mechanism to meet the needs of different businesses. QOS requirements. The SDN-based industrial control network uses the characteristics of separation of control and forwarding in software-defined networks, and centrally controls the data forwarding mode in the network through the controller, assigns different priorities to different data, and schedules data with different priorities.

Queue priority is to queue up the data that needs to be forwarded in order of priority, and then the scheduler gives priority to the high priority queue to be forwarded first. However, there are many scheduling mechanisms of the scheduler, and different scheduling mechanisms will lead to great changes in network performance, so the research on the scheduling mechanism is very important. Currently existing queue scheduling algorithms include SP (Strict-Priority, strict priority queue), WFQ (Weighted FairQueue, weighted fair queue) and WRR (Weighted Round Robin, weighted round robin queue).

The rapid rise of next-generation industrial networks has drawn more and more attention to the real-time issues of SDN-based industrial networks. Therefore, it is very important to propose a queue scheduling mechanism suitable for this new network to meet the real-time transmission requirements of different services.

Contents of the invention

Aiming at the SDN-based industrial real-time control network, the present invention proposes an industrial control network queue scheduling method based on the SDN architecture, which uses a scheduling mechanism combining events and time to meet the real-time requirements of data in the industrial control network.

The technical scheme that the present invention adopts for realizing the above object is: a kind of time-based and event-based dual-trigger queue scheduling method, comprising the following steps:

Step 1: After the data is sent from the publisher, the registration information is first sent to the storage unit in the controller for storage, for subsequent subscription by the subscriber;

Step 2: When a subscriber sends a subscription request to the controller, the controller checks whether there is a publisher that meets the requirements in the storage unit, and if so, returns a subscription success message to the subscriber, otherwise returns a subscription failure message;

Step 3: After the subscription is successful, the controller calculates the transmission path that meets the needs according to the information of the sender and the subscriber;

Step 4: The controller generates the flow table information and sends it to the network transmission device on the transmission path;

Step 5: The publisher starts to send messages to the subscriber. When the data enters the network transmission device, it assigns different types of data to different queues according to the flow table information;

Step 6: According to the time-triggered state of the relevant queue stored in the flow table, alternately open or close the corresponding time window to control the transmission state of the data queue exit;

Step 7: The transmission decision maker transmits data according to the data priority mechanism and the parity change of the data transmission window;

Step 8: Transfer control data/transmit other types of data according to the priority when the odd window is open, transfer other types of data/control data according to the priority when the even window is open, and repeat steps 5 to 5 to the next transmission device 8 until the subscriber acquires all required subscription information from the publisher.

The types of data include control data, audio data, video data, monitoring data, background data and other data.

The data is divided into two categories according to the type, one is control data, which has the highest real-time requirements; the other includes all data except control data, and the order of priority from high to low is: audio data , video data, monitoring data, background data and other data.

The alternate time-triggered states in step 6 correspond to the scheduling states of the two queues:

One is q1:q2:q3:q4=1000, which means that only the first time triggers the door to open and transmits control data;

The other is q1:q2:q3:q4=0111, which means that all time-triggered gates except the first time-triggered gate are open, and data other than control data are transmitted.

The alternation of the time-triggered states occurs alternately at the same time interval.

The trigger mechanism of the decision maker includes time trigger or event trigger.

The time trigger refers to controlling the alternate sending of different types of data by controlling the sending time windows of different types of data.

The event triggering refers to putting data into different queues according to service types, and setting the priorities of different services as the basis for scheduling within the non-control data time window.

The control data has the same priority, label the control data, mark the sending time slot and receiving time slot of the control data, and then determine the order in which the control data is sent; the sending time slot and receiving time slot are a cycle at the publishing end The time slot under time, the sending time slot is the cycle time label at which the sending end sends the data, and the receiving time slot refers to the cycle time label at which each forwarding device in the network sends the data.

The sending order of determining the control data follows the following rules: in the case of different sending time slots, the control data with earlier sending time slots is transmitted preferentially; in the case of the same sending time slots, the control data with earlier receiving time slots is sent .

The size of the time window and the size of the data frame can affect the end-to-end delay of data transmission.

The present invention has the following advantages and beneficial effects:

1. Solved the real-time queue scheduling problem of the industrial control network based on the SDN architecture, and realized the real-time and reliable transmission of different types of services.

2. The present invention adopts the dual trigger mechanism of time and event, sets different transmission queues for different services, and sends data through alternate time windows to realize real-time reliable transmission.

3. Through the real-time queue scheduling method, the data transmission delay and delay jitter are reduced, and the real-time requirements of different services are met.

4. Through the delay analysis of the network transmission model, determine the target point to reduce the delay, and realize the first-receive-first-send mechanism for high-priority data by labeling the data, so as to reduce the delay of data services with high real-time requirements as much as possible , to meet the application requirements of industrial scenarios.

Description of drawings

Fig. 1 is a schematic diagram of queue scheduling in the forwarding device of the present invention;

Fig. 2 is a schematic diagram of time delay analysis of the transmission model of the present invention;

Fig. 3 is a multi-service transmission network topology diagram of the present invention;

FIG. 4 is a data frame sequence diagram of multi-hop transmission data queue scheduling of the present invention;

Fig. 5 is a flowchart of queue scheduling in the present invention.

detailed description

The following will clearly and completely describe the technical solutions in the embodiments of the present invention with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only some, not all, embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by persons of ordinary skill in the art without making creative efforts belong to the protection scope of the present invention.

The present invention realizes a queue scheduling method with real-time guarantee in the field of industrial control network. The industrial control network is based on a software-defined network architecture. The schematic diagram of queue scheduling in a forwarding device is shown in FIG. 1 . The SDN-based industrial control network supports the openflow protocol, and realizes data entry and exit, storage and forwarding, etc. through the flow table. The controller centrally stores the network topology, registration subscription information, etc., and calculates the forwarding path of the publisher and subscriber. In order to ensure the real-time performance of multi-service data, after the data enters the forwarding device, it needs to be loaded into different types of queues. How to schedule the data in the queues at the exit is the focus of the present invention.

The queue scheduling method proposed in the present invention reduces the end-to-end time delay of data by minimizing the dwell time of the data frame in the switch, thereby satisfying the real-time performance of control data. This method divides the time axis into odd and even scheduling slots with the same length, and the received data is marked with the receiving slot serial number, and the residence time of the data frame in the switching device is related to the scheduling slot width, which in turn depends on Control the maximum frame length and maximum end-to-end delay of data. According to the relevant protocol requirements of the industrial control network, the maximum delay of control data is not greater than 20 microseconds.

In order to meet the real-time requirements of the business, that is, to reduce the network delay as much as possible, the present invention analyzes the delay model from the publishing end to the subscribing end, as shown in FIG. 2 . As can be seen from Figure 2, the data is sent from the sender to the subscriber, and the delay factors include: the data processing delay in the release end from the application layer to the MAC layer ΔP, and the physical layer delay Δt _x ; the release end Propagation delay _Δtrans to the switch; delay ΔS _in from the physical layer receiving data to the MAC layer port in the switching device; internal flow table query and relay forwarding delay ΔS _prop in the switching device; output port delay ΔS _out and Δt _x ; the propagation delay Δ _trans from the switching device to the subscriber; the processing delay ΔS from the physical layer to the application layer at the subscriber. The time delay concerned in the present invention mainly refers to the time delay between data entering the switching device and sending out from the switching device.

The data types involved in the present invention include control data, audio data, video data, test data and background data, etc. In order to simplify the description of the case, the data is divided into 4 types, namely control data, audio data, video data and other data, Other data adopt best-effort service mechanism. The maximum frame size of various data and the maximum allowable end-to-end delay are given in Table 1.

Table 1 Various business information table

type of data Maximum frame size Maximum end-to-end delay control data 128bytes 100us/5hops audio data 256bytes 2ms/7hops video data 256bytes 50ms/7hops other data 256bytes n.a.

Then use the multi-service transmission case shown in Figure 3 to analyze the information exchange form in the multi-service industrial control network macroscopically. There are 4 kinds of services listed in Table 1 in accompanying drawing 3, pub1 to sub3 are video data services; pub2 to sub0 and pub4 to sub2 are control data services; pub3 to sub1 are audio data services; other data use best effort The transport mechanism, regardless of its real-time requirements. It can be seen from Fig. 3 that S2 is a core node, and multiple service flows pass through this node. The schematic diagram of the scheduling process of data packets in S2 is shown in Fig. 1 .

The scheduling sequence diagram shown in Figure 4 is the N2-S1-S2-N4 stream in Figure 3. Assume that the data timing sequence when the data flows through link1 is shown in the first row of the figure. When the data passes through S1 to the first row When there are two links, the timing is shown in the second row in Figure 3. Comparing the first two lines, it is found that when the control data (1,1) reaches the second link after passing through S1, the label becomes (2,1). The general structure of the two-digit expression in the brackets is (x, y), y represents the time slot where the data is sent out, and x represents the time slot where the data is received. The purpose of adding tags is to prevent out-of-sequence data transmission and cause some data transmission lags. By adding tags, it is clear which time slot the data packet comes from and the processing progress compared with other data packets, so it can be The data packets with slow processing progress enter the queue in advance after entering the switching device, so that the processing speed of the same kind of business is roughly the same. In Figure 4, the time window sizes of the processing queues of the switching devices S1 and S2 are different. The size of the time window affects the residence time of the data packet in the switching device, which in turn affects the delay of the data packet. Therefore, the setting of the time window size is very important. . It can be generally seen from Figure 4 that the control data can be transmitted reliably, and the transmission delay is within two cycle time intervals, which can meet the real-time requirements of transmitting industrial control data.

The whole process from registration to successful transmission of the service is analyzed, and a detailed flow chart of the scheduling method is given, as shown in Figure 5.

Step 1: After the data is sent from the publisher, the registration information is first sent to the storage unit in the controller for storage, for subsequent subscription by the subscriber;

Step 2: When a subscriber sends a subscription request to the controller, the controller checks whether there is a publisher that meets the requirements in the storage unit, and if so, returns a subscription success message to the subscriber, otherwise returns a subscription failure message;

Step 3: After the subscription is successful, the controller calculates the transmission path that meets the needs according to the information of the sender and the subscriber;

Step 4: The controller generates the flow table information and sends it to the network transmission device on the transmission path;

Step 5: The publisher starts to send messages to the subscriber. When the data enters the network transmission device, it assigns different types of data to different queues according to the flow table information;

Step 6: According to the time-triggered state of the relevant queue stored in the flow table, alternately open or close the corresponding time window to control the transmission state of the data queue exit;

Step 7: The transmission decision maker transmits data according to the data priority mechanism and the parity change of the data transmission window;

Step 8: Transfer control data/transmit other types of data according to the priority when the odd window is open, transfer other types of data/control data according to the priority when the even window is open, and repeat steps 5 to 5 to the next transmission device 8 until the subscriber acquires all required subscription information from the publisher.

Claims (9)

1. a kind of industrial control network queue scheduling method based on SDN framework, it is characterized in that, may further comprise the steps: Step 1: After the data is sent from the publisher, the registration information is first sent to the storage unit in the controller for storage, for subsequent subscription by the subscriber; Step 2: When a subscriber sends a subscription request to the controller, the controller checks whether there is a publisher that meets the requirements in the storage unit, and if so, returns a subscription success message to the subscriber, otherwise returns a subscription failure message; Step 3: After the subscription is successful, the controller calculates the transmission path that meets the needs according to the information of the sender and the subscriber; Step 4: The controller generates the flow table information and sends it to the network transmission device on the transmission path; Step 5: The publisher starts to send messages to the subscriber. When the data enters the network transmission device, it assigns different types of data to different queues according to the flow table information; Step 6: According to the time-triggered state of the relevant queue stored in the flow table, alternately open or close the corresponding time window to control the transmission state of the data queue exit; Step 7: The transmission decision maker transmits data according to the data priority mechanism and the parity change of the data transmission window; Step 8: Transfer control data/transmit other types of data according to the priority when the odd window is open, transfer other types of data/control data according to the priority when the even window is open, and repeat steps 5 to 5 to the next transmission device 8 until the subscriber acquires all required subscription information from the publisher. 2. A kind of SDN framework-based industrial control network queue scheduling method according to claim 1, is characterized in that, the type of described data comprises control data, audio data, video data, monitoring data, background data and other data. 3. A queue scheduling method for industrial control networks based on SDN architecture according to claim 1 or 2, wherein the data is divided into two categories according to types, one is control data, which has the highest real-time performance requirements; the other category includes all data except control data, and the order of priority from high to low is: audio data, video data, monitoring data, background data and other data. 4. a kind of industrial control network queue scheduling method based on SDN architecture according to claim 1, is characterized in that, the time triggering state alternately in described step 6 is corresponding to the scheduling state of two kinds of queues: One is q1:q2:q3:q4=1000, which means that only the first time triggers the door to open and transmits control data; The other is q1:q2:q3:q4=0111, which means that all time-triggered gates except the first time-triggered gate are open, and data other than control data are transmitted. 5. A queue scheduling method for an industrial control network based on an SDN architecture according to claim 1 or 4, wherein the alternation of the time-triggered states occurs alternately at the same time interval. 6. A kind of industrial control network queue scheduling method based on SDN framework according to claim 1, is characterized in that, the trigger mechanism of described decision maker comprises time trigger or event trigger; The time trigger refers to controlling the alternate sending of different types of data by controlling the sending time windows of different types of data; The event triggering refers to putting data into different queues according to service types, and setting the priorities of different services as the basis for scheduling within the non-control data time window. 7. A kind of industrial control network queue scheduling method based on SDN architecture according to claim 6, characterized in that, the control data has the same priority, the control data is labeled, and the sending time slot and receiving time slot of the marking control data time slot, and then determine the sequence of control data transmission; the sending time slot and receiving time slot are time slots under the cycle time of the issuing end, and the sending time slot is the cycle time label where the sending end sends the data, The receiving time slot refers to the cycle time label at which each forwarding device in the network sends the data. 8. A method for scheduling queues in an industrial control network based on an SDN architecture according to claim 7, wherein the determination of the sending order of the control data follows the following rules: in the case of different sending time slots, priority transmission is sent Control data with an earlier time slot; in the case of the same sending time slot, send and receive control data with an earlier time slot. 9. A queue scheduling method for industrial control networks based on SDN architecture according to claim 1, wherein the size of the time window and the size of the data frame can affect the end-to-end delay of data transmission.