KR20140021305A - Communication system and real time frame switching method - Google Patents

Abstract

A communication network system and a real time frame switching method are disclosed. One or more network nodes among a plurality of network nodes included in the communication network system comprise a frame filter for determining whether a frame received from a network node arranged on direct front side of a data transmission path is targeted to the corresponding network node as a destination node and for transmitting the frame to a receive first-in first-out or a forward first-in first-out according to the result of determination; a frame processing unit for transmitting the frame stored in the received first-in first-out to a transfer first-in first-out by processing the stored frame according to the determined method; and a forward switch for transmitting the frame stored in the forward first-in first-out and the transfer first-in first-out to the network node arranged on direct rear side of the data transmission path based on the priority.

Description

Communication system and real time frame switching method

The present invention relates to a communication network system and a real-time data transmission method.

A network-based control system based on Ethernet communication is mainly used to transmit high-speed real-time data such as synchronous motion control. In this system, the clock synchronization standard IEEE 1588 is used for synchronization, and IEEE 1588 is also used in EtherCAT, PowerLINK, and the like.

In connection with the real-time data communication method, U.S. Patent Application Publication No. 2009/0129395 (Method, communication network and control unit for the cyclical transmission of data) generates a frame by one master and the other slave processes the received frame And then forwarding the data.

However, the prior art patent has a limitation in that it can not provide a method for performing an efficient function when a plurality of masters exist in the communication system.

Patent Document 1: US 2009/0129395 (Method, communication network and control unit for the cyclical transmission of data)

The present invention provides a communication network system and a real-time frame switching method that can be applied without limitation in a communication network system in which a plurality of masters exist, and can transmit a frame having a high priority to a receiving end even in the middle of frame transmission in priority order .

Other objects of the present invention will become readily apparent from the following description.

According to an aspect of the present invention, there is provided a communication network system, comprising: a plurality of network nodes sequentially connected to form a data transmission path for frame transmission / reception, wherein one or more network nodes A frame filter for determining whether a frame received from the network node is a destination of the network node, and delivering the frame to the receiving first selector or the transmitting first selector according to the determination result; A frame processing unit for processing the frame stored in the receiving first selector according to a designated method and transmitting the processed frame to the first selector for transmission; And a forward switch for forwarding the frames stored in the forwarding selector and the forwarding selector to a network node arranged immediately following the data transmission path on a priority basis.

Wherein the forward switch stops transmission of the first frame and performs transmission of the second frame when a second frame of a higher priority is generated during transmission of the first frame of a lower priority, Lt; RTI ID = 0.0 > transmission / reception < / RTI >

The frame includes at least one of information relating to connection or non-connection of a frame, switching information about switchingability, information about a priority of a corresponding frame, and identification information for distinguishing a transmission / reception message You can have included headers.

The frame may have a tail including at least one of information relating to frame connection or connection and size information (size) of a frame or data.

When one frame is switched to be separately transmitted, the size information included in the tail corresponding to the resumed transmission data may be information indicating the size of the residual data.

The frame processing unit may combine the incompletely separated frames by the switching process into one complete frame, and then perform the designated processing.

The frame is composed of a header, data, and a tail, and the data may be stuffed into one of COBS (Consistent Overhead Byte Stuffing), bit stuffing, and byte stuffing.

The frame processing unit may include a decoder for destuffing the stuffed data, and an encoder for stuffing the processed data again.

The forward switch may first transmit the frames stored in the transfer first-in first-out selector when the frames stored in the transfer first-in-first-out and the first-in-first-out selector have the same priority.

The plurality of network nodes may be interconnected to form an Ethernet-based communication network.

Other aspects, features, and advantages will become apparent from the following drawings, claims, and detailed description of the invention.

According to the embodiment of the present invention, it is possible to apply without limitation to a communication network system in which a plurality of masters exist, and it is possible to transmit a frame having a high priority to a receiving end preferentially even during frame transmission according to the priority.

1 illustrates a real-time communication architecture of Ethernet-based communication protocols;
2 is a diagram illustrating a frame structure of a real-time communication protocol according to the prior art;
3 illustrates a configuration of a network-based control system according to an embodiment of the present invention.
4 illustrates a frame structure according to an embodiment of the present invention.
5 is a diagram schematically illustrating the structure of a frame processor according to an embodiment of the present invention;
6 is a diagram illustrating a frame process of a frame processor according to an embodiment of the present invention.
FIG. 7 illustrates a frame process according to a priority of a frame processor according to an exemplary embodiment of the present invention; FIG.

While the invention is susceptible to various modifications and alternative forms, specific embodiments thereof are shown by way of example in the drawings and will herein be described in detail. It is to be understood, however, that the invention is not to be limited to the specific embodiments, but includes all modifications, equivalents, and alternatives falling within the spirit and scope of the invention.

When a component is referred to as being "connected" or "connected" to another component, it may be directly connected to or connected to that other component, but it may be understood that other components may be present in between. Should be. On the other hand, when an element is referred to as being "directly connected" or "directly connected" to another element, it should be understood that there are no other elements in between.

The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. Singular expressions include plural expressions unless the context clearly indicates otherwise. In this specification, the terms "comprises" or "having" and the like refer to the presence of stated features, integers, steps, operations, elements, components, or combinations thereof, But do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, or combinations thereof.

The terms first, second, etc. may be used to describe various components, but the components should not be limited by the terms. The terms are used only for the purpose of distinguishing one component from another.

In addition, the terms "part," "unit," "module," "device," and the like described in the specification mean units for processing at least one function or operation, Lt; / RTI >

It is to be understood that the components of the embodiments described with reference to the drawings are not limited to the embodiments and may be embodied in other embodiments without departing from the spirit of the invention. It is to be understood that although the description is omitted, multiple embodiments may be implemented again in one integrated embodiment.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Reference will now be made in detail to the preferred embodiments of the present invention, examples of which are illustrated in the accompanying drawings, wherein like reference numerals refer to the like elements throughout. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the following description, well-known functions or constructions are not described in detail since they would obscure the invention in unnecessary detail.

1 is a diagram illustrating a real-time communication architecture of Ethernet-based communication protocols.

Various communication techniques have been developed for real-time communication, and international standards IEC 61158 and IEC 62026 have been enacted in 2000. In order to overcome the disadvantage that the conventional fieldbus using RS485 or CAN is slow, real-time communication is gradually evolving on the basis of Ethernet. Such Ethernet-based real-time communication protocol is classified into 3 Lt; / RTI > architecture.

The first architecture separated by (a) is a real-time communication method defined on the existing TCP / UDP stack, and the second architecture separated by (b) is a real-time communication method for separately processing data to be processed in real time under the IP stack , and (c) are real-time communication methods that provide a separate scheduling function.

Considering the real-time performance among the three architectures shown, the third architecture shows the best performance, but there are many features added in the standard IEEE 802.

2 is a diagram illustrating a frame structure of a real-time communication protocol according to the related art. 2 (a) shows the frame structure of the Ethernet communication protocol, and FIG. 2 (b) shows the frame structure of the Ethernet communication protocol.

The Ethernet-based real-time communication uses a method of inserting a frame suitable for each communication protocol into a payload area in the frame structure of the Ethernet communication protocol shown in FIG. 2 (a). This can be easily understood with reference to (b) of the frame structure of the Ethernet communication protocol as a kind of Ethernet-based real-time communication method.

In the ethernet communication method using the frame structure shown in FIG. 2 (b), only one master has a frame transmission right, and the remaining nodes connected to the network process frames received from the master or another node, The frames processed by all nodes are returned to the master.

Since the Ethernet communication method minimizes the time required for each node to process a frame, time required for the master to transmit the frame and receive the frame again can be minimized, so that the real time transmission performance is evaluated as the best communication method have.

However, the Ethernet communication method does not effectively utilize excellent real-time performance for master-to-master communication, and communication methods such as Ethernet-based UDP / IP are used. In addition, if one master fails with two or more masters, there is also a limitation that the ether communication method can not be utilized in a plant requiring hot-backup in which another master replaces the existing master function.

3 is a block diagram of a network-based control system according to an embodiment of the present invention.

Referring to FIG. 3, the communication network system according to the present embodiment includes at least one master 310 and a plurality of slaves 320a, 320b, 320c, and 320d (hereinafter collectively referred to as 320 when no separate distinction is required) And is sequentially connected by a cable between the master 310 and each of the slaves 320.

The master 310 transmits any data (i. E., Frame and data for robot control, for example) to the slaves 320. [

The master 310 periodically calculates and transmits offset values and delay values generated between the devices on the network (i.e., the master 310 and the slaves 320) The system time of the master 310, which is a device, is periodically distributed on the network. The offset value may be a difference between an internal clock value of the master 310 when the master 310 transmits data and an internal clock value of the slave 320 when the slave 320 receives the data. And the delay value may be a delay time that occurs in the process of transmitting data at the master 310 and the slave 320 receiving the data or vice versa.

The slave 320 receives data from the master 310 or receives data from the slave 320 located at the previous stage on the data transmission path.

When the received data is data targeted for the slave 320, the processing unit included in the slave 320 reads the data and performs the process specified by the data, and if necessary, And transmits the data to the slave 320 or the master 310 located at the rear end on the transmission / return path (which will be collectively referred to as a data transmission path in the case where no distinction is necessary in this specification). The data transmitted from the slave 320 to the slave 320 or the master 310 at the subsequent stage may include data transmission time and data processing time, for example.

The slave 320 is also synchronized using the system time received from the master 310 and is synchronized with the clock 310 by correcting its local system time based on the offset value and delay value calculated and provided by the master 310, .

The communication network system according to the present embodiment is characterized in that one or more frame transmission nodes (for example, a master) exist in the system so that distributed processing is possible and priority-based frame switching can be performed to guarantee real-time performance. That is, the system may be configured to operate as if there are a plurality of masters in the system by including a frame transmission function in a processing unit included in one or more nodes included in the communication network system.

4 is a diagram illustrating a frame structure according to an embodiment of the present invention.

4, the frame structure of the communication network system according to the present embodiment is basically composed of a header (header), data D and data, and a tail T as a separator S, And has a repeated structure.

In the header (H, Header), information on connection or non-connection of a frame, information on switching availability (i.e., whether frame separation transmission is possible), information on a priority of a corresponding frame (Priority) And identification information for distinguishing between the user and the user. For example, the information on whether or not the frame is connected may be designated as S (Start) for a frame that starts independently and C (Connection) when the frame is connected to a preceding frame. For example, it may be designated as S (Switchable) for a switchable frame or N (Not Switchable) for a switchable frame.

Herein, the information on whether or not the switching is possible may be included in order to take account of the fact that switching may not be possible according to the frame. Even if a high priority frame is generated during transmission of a frame designated as not switching (N) in the network node, since the frame being transmitted is designated as not switchable in the header, the frame is not switched. The reason for using the information on whether or not the switching is possible is that if a frame is switched, a header and a tail are added. This causes a problem of overhead, which reduces overall lending width. to be.

The T (Tailer) may include at least one of information relating to frame connection or connection and size information (size) of a frame or data. Here, the information on whether or not the frame is connected may be designated as E (End) for a frame completed with the corresponding frame, or C (Connection) when the frame is connected to a subsequent frame.

In the dashed box shown in Fig. 4, there are three frames: a first frame which is S1, H1, D1 and T1, a second frame which is S2, H2, D2 and T2 and a third frame which is S3, H3, D3 and T3 Are illustrated.

However, if only two frames (i.e., the first frame and the second frame) are transmitted in the frame transmission node (for example, the master), in the process of passing through the network nodes constituting the data transmission path, If a second frame having a relatively high priority is received during transmission of a first frame designated to be switchable to another network node located immediately after the transmission path, the corresponding network node stops transmission of the first frame, It may transmit the second frame first and then transmit the rest of the first frame (i.e., residual data) in the form of a third frame.

In this case, although the frame is physically divided into three frames, since the first frame and the third frame are actually one frame in the receiver, two frames are received as a result.

As described above, it is possible to perform separate transmission of frames (i.e., a switching process in which a frame transmitted by a high-priority frame is divided into a plurality of frames and transmitted) (Connection) information indicating whether or not a previous frame of the same priority is connected, Switching information indicating whether or not the frame is switchable, information about a priority of the frame and a receiver for identifying the frame, (Tailer) includes information indicating whether there is a frame to be transmitted next and size information (size) of the frame or data transmitted at this time .

The manner in which the header and tail of the frame include the above information may be included in its own form or may be coded in any coding manner. Here, it is needless to say that the method of coding the information is not limited.

As described above, each frame is separated by a delimiter identifier consisting of one byte, for example, called a separator (S, Separator). Here, the delimiter identifier can be selected as one of 256 numbers that can be represented by a byte. To distinguish a frame using a delimiter, the delimiter in the byte unit data (for example, the data area) between the delimiters The defined number should not appear. As described above, there are bit stuffing, byte stuffing, and the like to prevent a specific number from being displayed.

For example, when 01111110 is selected as a separator, a bit stuffing method is adopted in which 0 is inserted when 1 is 5 consecutive in order to prevent the 01111110 pattern from appearing in the data area so that the same pattern as the designated separator does not appear.

As the byte stuffing method, for example, a method using Flag and Escape used in the PPP (Point to Point Protocol) method may be used. It goes without saying that various methods may be additionally or alternatively used as a byte stuffing method (for example, a COBS (Consistent Overhead Byte Stuffing) method).

In the frame structure shown in FIG. 4, a stuffing method such as the byte stuffing and the bit stuffing is used for the data area. However, different stuffing methods described below may be applied to the header and the tail only.

A different stuffing scheme that can be applied for the header and tail may be a method that utilizes a number less than 255 out of 256 that can be represented by bytes.

For example, assuming that the information (Connection) about whether or not a frame is included in the header and the information about switching availability (Switching) are each a variable occupying one bit, and that the identifier is a variable occupying two bits , And the priority information (Priority) is a method of using only 15 except for one of the 16 numbers that can be represented by the remaining 4 bits.

In this case, since the number of representations of the priority information and the number of representable bits of the remaining 4 bits are 240 (that is, 15 * 2 ⁴ = 240), 255 separable expressors Lt; / RTI > bytes. Therefore, when using the above-described method, desired header information can be expressed within one byte without adding extra bits or bytes.

In the case of the tail, since the number of 256 or more can be included in the size information of the frame or the data, the connection information and the size information (size) can be represented by 2 bytes (i.e., 256 256 numbers) ) Can be limited.

In this case, if the connection information is represented by 1 bit, the size information may have a number of 0 to 32384 (i.e., 127 * 255 = 32385 branches since 2 bits of connection information are excluded).

5 is a diagram schematically showing the structure of a frame processor according to an embodiment of the present invention.

Referring to FIG. 5, a frame processor included in one or more network nodes configuring a data transmission path includes a frame filter 510, forward FIFOs 520, receive FIFOs, A frame processor 535, a transmit FIFO 570 and a forward switch 580. The frame processor 535 may include a decoder 540, an upper layer processor 550 And an encoder 560. [0050]

When a frame is received, the frame filter 510 refers to the identifier included in the header of the frame and determines whether the received frame is for the corresponding node. If the received frame is for the node, the frame filter 510 stores the received frame in the acceptor 530, but if the received frame is not for that node, 510 stores the received frame in the forwarding selector 520 for transmission to the network node disposed immediately after the data transmission path.

The decoder 540 removes the header and the tail from the frame stored in the reception first-in first-out selector 530 and provides the data and the identification information included in the header to the upper layer processor 550.

The upper layer processor 550 may correspond to, for example, an application layer processing unit of the OSI 7 layer of a general fieldbus system.

The encoder 560 adds a header and a tail to the data processed by the upper layer processor 550 and reconstructs the frame into a frame to be transmitted to a network node disposed immediately after the data transmission path and then transmits the frame to the transmission first- And stores the reconstructed frame.

The forward switch 580 refers to the priority information stored in the header of each frame with respect to the frames stored in the transfer first-in first-out selector 520 and the transfer first-in-first-out selector 570, And transmits the frame to the network node immediately after the route. At this time, the forward switch 580 may perform switching processing.

Hereinafter, the operation of the frame processor will be briefly described.

The frame filter 510 of the frame processor determines whether the received frame is for the corresponding node by referring to the identification information included in the header of the received frame, and if the received frame is a frame for the corresponding node, (530) to the decoder (540). The frame provided to the decoder 540 is provided to the upper layer processor 550 after performing a process such as byte destuffing. However, if it is determined that the received frame is not for the node, the frame is forwarded to forward switch 580 via forwarding selector 520 for forwarding.

The forward switch 580 is processed by the upper hierarchical processor 550 and is supplied to the transmission first-in-first-out selector 570 and the transfer first-in-first-out selector 520 The frame having the highest priority is preferentially transmitted.

If the priority of the frames stored in the transmission first selector 570 and the transmission first selector 520 is the same, the forward switch 580 selects the frame stored in the transmission selector 520, for example, And transmit the data.

However, if a high priority frame is stored in the transmission first-in-first-out selector 570 and / or the transmission first-in-first-out selector 520 during transmission of any frame for which the forward switch 580 is set to be switchable, The switch 580 stops transmission of the currently transmitted frame, transmits the frame tail first, and then transmits the stored high priority frame.

Here, the frame tail is transmitted so that the network node on the data transmission path can recognize that the frame in which the transmission is stopped is not due to the completion of the transmission. Also, in order to allow the network node to recognize how many bytes have been transmitted to be. The network node can determine whether the frame is normal by using the size information included in the frame tail. When the frame is switched, the network node can determine whether the frame is normal by comparing the size information with the size information of the corresponding frame .

When the high priority frame transmission is completed, the forward switch 580 first transmits the header for the frame in which the transmission is stopped, and resumes the remaining data transmission after the transmission is stopped. When resuming transmission and transmitting the residual data, the header added to the residual data should include a connection to be associated with the previous specific frame.

6 is a diagram illustrating a frame process of a frame processor according to an embodiment of the present invention.

In FIG. 6, RX denotes a frame to be received, FF denotes a frame transmitted to the forwarding selector 520 since it is not a frame transmitted to the corresponding node, SF denotes a frame delivered to the corresponding node, A frame that is destuffed by the decoder 540 and is connected to a frame to be interconnected and transmitted to the upper layer processor 550. [

S denotes a separator, H denotes a header, D denotes data, and T denotes a tail. A frame of a bold solid line box indicates a frame that can not be switched, a frame of a thick outline dotted line box indicates a frame capable of switching, a thick outline dotted box and a solid line segment indicate a frame stored in the first-in first-out selector.

In addition, HS1 shown in the figure is a header H, and indicates that connection information is connection start (S, Start) and priority is 1. Likewise, TE1 and TC2 indicate the tail (T) and the connection information (Connection) is the end (E, End) or the connection (C, Connected) and the priority is 1 or 2 respectively.

As shown in the figure, the decoder 540 refers to the header of the frame received and received by the receiver selector 530, and if the frame is one independent frame, the decoder 540 transmits the corresponding data to the upper layer processor 550, And transmits the corresponding data to the upper layer processor 550. The upper layer processor 550 receives the data from the upper layer processor 550,

7 is a diagram illustrating a frame process according to a priority order of a frame processor according to an embodiment of the present invention.

Referring to FIG. 7, the decoder 540 reconfigures a complete frame by interconnecting frames (i.e., fragmented frames) having a connection relationship between frames stored in the reception first-in-first-out selector 530, ). ≪ / RTI >

Referring to FIG. 7, it can be confirmed that a frame having a higher priority (that is, a lower number indicating a priority) is received first. In other words, the nodes arranged immediately before on the data transmission path can confirm the high-priority data by first transmitting them.

In other words, referring to the SF (i.e., the frame stored in the first-in-first-out selector 530), the reception of the frame of priority 3 is stopped while the frame of priority 3, which is the second frame, The frame having priority 2 is being received. In this case, a priority 2 frame (i.e., a third frame) is generated in a network node immediately preceding the data transmission path for transmitting a frame to the corresponding node, so that a low priority frame transmission .

Similarly, while the frame of priority 2, which is the third frame, is received, the reception of the frame of priority 2 is stopped (see the tail having the connection information of C) and the frame of priority 1 is being received. This is also because the priority 1 frame (i.e., the fourth frame) is generated in the network node immediately preceding the data transmission path and the low priority frame transmission is stopped to transmit the high priority frame first .

Thereafter, the frames for which transmission has been stopped are received in the order of higher priority, respectively, and stored in the receiving input selector. The decoder 540 reconstructs incomplete frames into one frame and transfers the frames to the upper layer processor 550 , The reconstructed data in one frame is transmitted to the node immediately disposed on the data transmission path through the forward switch 580 after the processing of the upper layer processor 550 or the like is completed.

If a frame having a higher priority than a transmitting frame is generated in the course of transmitting a frame to a node immediately disposed on a data transmission path, transmission of the corresponding frame can be switched.

It is a matter of course that the real-time frame switching method of the communication network system described above may be performed by an automated procedure in a time series sequence by a built-in or installed program in the digital processing apparatus. The codes and code segments that make up the program can be easily deduced by a computer programmer in the field. In addition, the program is stored in a computer readable medium readable by the digital processing apparatus, and is read and executed by the digital processing apparatus to implement the method. The information storage medium includes a magnetic recording medium, an optical recording medium, and a carrier wave medium.

It will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the spirit or scope of the invention as defined in the following claims And changes may be made without departing from the spirit and scope of the invention.

510: frame filter 520: first-in-first-out transmitter
530: First-in-first-out selector 535:
540: Decoder 550: Upper layer processor
560: Encoder 570: First-in-first-out transmitter
580: Forward switch

Claims (10)

In a communication network system,
A plurality of network nodes sequentially connected to form a data transmission path for frame transmission / reception,
The one or more network nodes,
A frame filter for determining whether a frame received from a network node arranged immediately before on the data transmission path is a destination of the corresponding network node and delivering the frame to a receiving first selector or a forward selector according to a determination result;
A frame processing unit for processing the frame stored in the first-in, first-out and first-in-first-out to transmit to the first-in-first-out for transmission; And
And a forward switch for transmitting the frames stored in the first-in first-out for delivery and the first-in first-out for transmission to a network node disposed immediately after the data transmission path based on priority. The method of claim 1,
The forward switch stops transmitting the first frame and transmits the first frame when the second frame of the high priority occurs while transmitting the first frame of low priority. A communication network system that performs a switching process to resume transmission of the remaining data of the. 3. The method according to claim 1 or 2,
The frame includes at least one of information relating to connection or non-connection of a frame, switching information about switchingability, information about a priority of a corresponding frame, and identification information for distinguishing a transmission / reception message A communication network system having an embedded header. 3. The method according to claim 1 or 2,
Wherein the frame has a tail including at least one of information relating to frame connection or connection and size information (size) of a frame or data. 5. The method of claim 4,
Wherein size information included in a tail corresponding to remaining data resumed from transmission is information indicating a size of the residual data when switching processing is performed so that one frame is separately transmitted. 3. The method of claim 2,
Wherein the frame processing unit combines the incompletely separated frames by the switching processing into one complete frame, and then performs the specified processing. The method of claim 1,
Wherein the frame comprises a header, data and a tail,
Wherein the data is stuffed into one of COBS (Consistent Overhead Byte Stuffing), bit stuffing, and byte stuffing. The method of claim 7, wherein
Wherein the frame processing unit includes a decoder for destuffing the stuffed data, and an encoder for stuffing the processed data again. The method of claim 1,
And the forward switch preferentially transmits the frames stored in the first-in, first-out and first-out-first-outs when the frames stored in the first-in, first-out and first-out first-outs have the same priority. The method of claim 1,
Wherein the plurality of network nodes are interconnected to configure an Ethernet-based communication network.

Images