CN101764706B

CN101764706B - Link redundant control method based on EPA network bridge

Info

Publication number: CN101764706B
Application number: CN2009102510370A
Authority: CN
Inventors: 向敏; 王平; 周涛; 孙韶伟; 周川
Original assignee: Chongqing University of Post and Telecommunications
Current assignee: Chongqing University of Post and Telecommunications
Priority date: 2009-12-28
Filing date: 2009-12-28
Publication date: 2012-02-01
Anticipated expiration: 2029-12-28
Also published as: CN101764706A

Abstract

The invention seeks protection for a realizing method of link redundant control of an EPA network bridge and relates to the field of industrial field control. The invention realizes an EPA network link redundant function and a redundant managing function on the EPA network bridge. The method adopts an STP spanning tree algorithm to realize the link redundant function and to analyze network paths. If a loop exists in the network, the most robust link is selected as a communication link, the others are redundant backup links, a network bridge port which is connected with the redundant backup links in the loop is set to a blocking state, and the network is pruned to a non-loop tree topologic structure. The redundant link managing function provided by the invention uses an STP redundant managing protocol to manage the communication link automatically, thus improving the reliability, stability and robustness of the whole EPA network. The method is suitable for industrial Ethernet of high reliability and high real-time data transmission.

Description

Link redundant control method based on the EPA bridge

Technical field

The present invention relates to the network communications technology, specifically is the link redundant control method of a kind of EPA (based on the industrial automation of Ethernet) network.

Background technology

The EPA real-time ethernet is a kind of brand-new open real-time ethernet standard that is applicable to industrial field device, and the IT technology of a large amount of maturations is applied to industrial control system.The EPA system is a kind of distributed system; It utilizes agreements such as ISO/IEC8802-3, IEEE802.11, IEEE802.15 will be distributed in on-the-spot several equipment, micro network segment and control/surveillance equipment and couples together; All devices is operated together, collaborative measurement and the control of accomplishing in industrial processes and the operation.

The EPA network application is in industry spot, and reliability requirement is very harsh.The EPA bridge is the visual plant in the EPA product chain; It interconnects two or more micro network segment; The communication data of equipment is effectively isolated in should the be realistic existing micro network segment, must guarantee equipment is communicated by letter with outer network segment device data in the micro network segment rapidity and accuracy again.Therefore the reliability of EPA bridge link is very crucial for EPA network-efficient, reliability service.The link redundancy technology has good using value for the reliability that improves and improve the EPA link.Existing Ethernet link redundancy technology mainly realizes on switch; Through between each switching node, making up many physical links redundant communication path is provided; (like " design of Dual-Ethernet redundant communication system and application " Liu Lijun etc.; 2005 18 7 phases of volume of industrial control computer; Through the connection that the Socket (socket) that is based upon on TCP/IP (TCP) the agreement basis sets up the client and server end, will launch reserve link automatically if client and server detects communication failure), thus the fault-tolerant ability of network and the reliability of raising network service improved.Yet switch is different with the definition of EPA bridge function, and switch realizes that the control method of link redundancy can't realize effective isolation of micro network segment devices communicating data; Simultaneously, to the link redundant control method of EPA network solution does not preferably appear also at present.For this reason, a kind of link redundant control method based on the EPA bridge of design is to improve the reliability of EPA network.

Summary of the invention

The present invention is directed to the high reliability request of link in the EPA industrial control network, proposed a kind of industrial control network that is applicable to, is the link redundant control method of carrier with the EPA bridge.

It is following that the present invention solves the problems of the technologies described above the technical scheme that is adopted:

According to the characteristics of EPA industrial control network and combine the EPA consensus standard; EPA network link disposal of Redundancy module is set in the EPA bridge; Revise the message forwarding capability of EPA bridge, adopt μ C/OS-II (real-time embedded) operating system the bridge all functions to be carried out unified management with task management mechanism.After the EPA bridge gets into the data communication state; Extract the EPA communication identifier (0x88CB) of the equipment that communicates with on the one hand; Judge the legitimacy of communication equipment and the state of current link; The bridge parsing module receives the configuration bridge protocol data unit B PDU message that other all bridges send on the network, resolves unique ID number of each entrained in each BPDU bag literary composition bridge, and the bridge of ID minimum is confirmed as the Root Bridge in the network; Root Bridge is responsible for periodically sending topological protocol Data Unit TPDU to the whole network, is about to network topology structure and informs other bridges.The network parsing module carries out analysis and judgement to network path, if current bridge is received the bridge protocol data unit B PDU message that carries own ID number, explains to have loop in the network, the network topology structure after will being confirmed to prune according to path priority by Root Bridge; And the priority judge module is confirmed the priority of bridge according to the timestamp difference; Select the most healthy and the strongest link as communication link; All the other are the redundancy backup link; The bridge port that connects the redundancy backup link in the port status module loop is set to blocked state, and network is trimmed to loop-free tree.Periodically send the link detection message through STP (Spanning TreeProtocol) spanning tree algorithm on the other hand; The communications status of identification communication link; When finding that current communication link breaks down; (STP) launches reserve link automatically by spanning tree algorithm, thereby realizes that the EPA communication link is quick, efficient, reliability service.

The appearance of loop is avoided in link redundancy control; Control method proposed by the invention is through realizing that at the EPA bridge STP (Spanning Tree Protocol) spanning tree algorithm blocks some redundant link ports; The network configuration that will have the redundant link function is trimmed to a loop-free tree topology, has avoided occurring in the network loop.When active link fails, adjust topological structure automatically and construct a tree topology again, reach the purpose of link backup thus, therefore the EPA network has also possessed certain network fault tolerance ability.This bridge adopts spanning tree algorithm (STP) to realize micro network segment link redundancy controlled function; Avoid the network segment communications loop to occur; Improved the reliability of communication link; Make the EPA network equipment carry out message in real time, in order, reliably and handle and transmit, thereby help to make up extensive EPA Control Network with high reliability.

Description of drawings

Fig. 1 EPA field apparatus or micro network segment topology diagram

Fig. 2 EPA bridge software is formed structural representation

Fig. 3 EPA bridge link redundancy control sketch map

(a) actual physics network topology structure figure

(b) tree of the generation after pruning sketch map

(c) tree of the generation after fault recovery sketch map

Embodiment

Below enforcement of the present invention is specifically described to accompanying drawing and instantiation.

Fig. 1 is the EPA network topology structure, comprises two network segment: monitoring level L ₂The network segment and field apparatus level L ₁The network segment.Field apparatus level L ₁The network segment is used to realize between the on-the-spot various field apparatuss of commercial production and field apparatus and L ₂The connection of the network segment; Monitoring level L ₂The network segment is mainly used in the connection that realizes between control room instrument, device and the man-machine interface.No matter be monitoring level L ₂The network segment still is field apparatus level L ₁The network segment all can be divided into one or several micro network segment.Each micro network segment is used to connect a plurality of EPA equipment as a control area.In a control area, mutual communication between the EPA equipment realizes specific measurement and controlled function.Interconnect through the EPA bridge between the micro network segment, a micro network segment links to each other with other micro network segment through an EPA bridge.

Shown in Figure 2ly be that the EPA bridge forms structural representation.Comprise μ C/OS-II (real-time embedded) operating system, EPA communication protocol stack module, EPA bridge safety function module, bridge bottom layer driving module, link redundancy module.The link redundancy processing module is set in the EPA bridge, revises the message forwarding capability of EPA bridge, adopt μ C/OS-II (real-time embedded) operating system the bridge all functions to be carried out unified management with task management mechanism.μ C/OS-II operating system module is that the multitask in the EPA bridge provides scheduling and the function of communicating by letter, and manages each functional module.EPA communication protocol stack module realizes the configuration and the dispatching management of EPA bridge.EPA bridge safety function module adopts firewall system, micro network segment equipment is carried out the EPA message differentiate that the communication data of non-EPA equipment abandons on the spot, thereby realizes the filtration of non-EPA data; EPA bridge bottom layer driving module realizes the reception and the forwarding of message.EPA bridge link redundancy module is guaranteed the reliability of communication link, through the backup of link redundancy control realization EPA network link, when primary link breaks down, launches backup link, thereby improves EPA network whole reliability.

The link redundancy module specifically comprises: initialization module, Root Bridge select module, bridge parsing module, priority that module, port status module are set.Behind each bridge electrifying startup; Initialization module is Root Bridge (Root Bridge) with the setting state of bridge self; And through all of the port on the bridge (the two-port bridge port is made as A, B; Three port bridge ports are made as A, B, C) send configuration bridge protocol data unit B PDU (Bridge Protocol Data Unit) to network; The timestamp that sends the self ID number (each ID whole network is unique) and the information of transmission provides timestamp for network competition Root Bridge (Root Bridge) provides to choose with optimal path for ID number to network.The bridge parsing module receives the BPDU message that other all bridges send on the network, resolves ID number entrained in each BPDU message, and sends it to Root Bridge selection module; Root Bridge selects module that ID number in all other bridges BPDU messages that receive with oneself ID number compared, if in all reception BPDU messages ID number all than self ID number greatly, then setting this bridge oneself is Root Bridge.If in the BPDU message that certain bridge receives ID number of entrained ID ratio oneself little, then changing the present state of this bridge is non-Root Bridge.

The port status module is provided with the bridge port state according to the different task of bridge work at present, bridge port can be set for blocking (Blocking), intercept (Listening), study (Learning), transmitting one of them state in (Forwarding) or forbidding (Disabled) 5 states according to the task of bridge.The port status module is provided with the port status of bridge according to different task: when working on power, port is set is the state of intercepting, receive entrained ID number of external BPDU message; Through the size of relatively the institute ID that receives number and self ID number, if exist an ID number littler than self ID, then this bridge is set to non-Root Bridge; If all ID that this bridge receives are big than self ID number, it is Root Bridge that this bridge then is set, and is responsible for periodically sending topological protocol Data Unit TPDU to the whole network; With other bridges of network topology structure information notification; And send the BPDU message to network, and this root bridge port state is changed to learning state, port is in normal reiving/transmitting state.The network parsing module is analyzed network path; If current bridge is received the bridge protocol data unit B PDU message that carries own ID number; Explain and have loop in the network; Then according to the topology information in the TPDU message that Root Bridge sent, the redundancy backup link port that this bridge port block of state is connected in the loop is set to blocked state; When the port status module detected one 3 port or more the certain port cisco unity malfunction occurs in the bridge of multiport, putting these ports was disabled status.

With Fig. 3 is that example specifies, and Fig. 3 is the schematic block diagram that EPA bridge redundant module is realized link redundancy control.Fig. 3 utilizes spanning tree algorithm (STP) for the link redundancy module and adjusts the sketch map that topological structure constructs a tree topology again automatically.Suppose that for shown in Fig. 3 (a), there is unallowed winding network (shown in annular arrow) in the actual physics network in the network.Behind system's power-up initializing; The IEEE1588 agreement that adopts bridge in the access network realizes the clock synchronization of bridge, obtains the topology information of network and selects the most healthy and the strongest link as " branch " that generate tree according to the priority of link through sending and transmit the BPDU message each other between the bridge.Each bridge receives the BPDU message that other bridges send, and extracts the timestamp information T that carries in the BPDU message ₁, receive that the bridge of BPDU message is noted the time stamp T when receiving this BPDU message ₂, depositing in the memory, stab tabulation settling time in the memory, the poor (T of the time of reception stamp when calculating the timestamp that carries in the BPDU message that other bridges send and oneself receiving ₂-T ₁), the difference of timestamp is stored in the memory tabulation, confirm path priority with this time extent, the priority judge module is according to the poor (T of timestamp ₂-T ₁) confirm the priority of bridge, the bridge priority that the timestamp difference is more little is high more.Judged bridge 1 when supposing initialization and be Root Bridge, joined bridge 3 and bridge 5 in the network.Each port that is operated in bridge 3 and bridge 5 respectively in network other bridges send the BPDU message; Bridge receives that BPDU message post analysis goes out to exist loop; Then send message and in bridge 3 and bridge 5, carry out path priority selection, bridge 3 and bridge 5 difference logging timestamps, and according to timestamp difference judgement path priority; Keep the path satisfy priority conditions, and with the non-priority path as the redundancy backup path.The bridge port that the port status module connects the redundancy backup path is set to blocked state; Should be set to blocked state like the port B that determines bridge 3 in this example and the port A of bridge 5; Link between the port blocked is the link that gets clogged (dotting among the figure); Make Fig. 3 (a) become the no winding network shown in Fig. 3 (b), make the link that gets clogged as the redundancy backup link.Root Bridge periodically scans bridge port, if do not receive the BPDU message that respective bridge is sent on the path at the appointed time, judges that then respective bridge breaks down.Root bridge port block of state transmitting control commands recovers the port get clogged, and according to the priority principle reselect satisfy priority conditions optimal path as communication path.If bridge 4 does not send the BPDU message to Root Bridge in cycle time; Can know that then this bridge breaks down and can not work; The E network segment will be temporarily can't with other network segment communicating, Root Bridge sends a command to bridge 3, bridge 3 is recovered the port B that gets clogged automatically by spanning tree algorithm (STP) according to this order; Again prune out unobstructed communication link, the network of pruning out again is shown in Fig. 3 (c).

More than just the preferred embodiments of the present invention explanation, protection scope of the present invention combines claim to limit based on those skilled in the art's understanding.

Claims

1. based on the link redundant control method of EPA bridge; The link redundancy processing module is set in the EPA bridge; Revise the message forwarding capability of EPA bridge, adopt real-time embedded operating system the bridge all functions to be carried out unified management, extract the EPA communication identifier of the equipment that communicates with task management mechanism; Judge the legitimacy of communication equipment and the state of current link; It is characterized in that the link redundancy processing module comprises that specifically initialization module, Root Bridge select module, bridge parsing module, priority that module and port status module are set; It is Root Bridge that initialization module is provided with this bridge, and other bridge all of the ports send configuration bridge protocol data unit B PDU message in network; The bridge parsing module receives the BPDU message that other all bridges send, and resolves ID number entrained in each BPDU message; Root Bridge selects module that ID number in all BPDU messages that receive with this bridge oneself ID number compared; If all receive in BPDU messages ID number all do not have own ID number greatly; Then confirm oneself to be Root Bridge; If ID number of the ID ratio in the BPDU message that receives oneself is big, then changing the present state of this bridge is non-Root Bridge; The bridge parsing module is analyzed network path; If current bridge is received the bridge protocol data unit B PDU message that carries own ID number; Explain there is loop in the network that if there is loop in the network, priority is provided with module is confirmed bridge according to the timestamp difference priority; Promptly; Stab tabulation settling time in the memory, and it is poor that the time of reception when calculating the timestamp that carries in the BPDU message of other bridges transmissions and oneself receiving the BPDU message stabs, and priority is provided with module and confirms that the more little bridge priority of timestamp difference is high more; Keep the path of satisfying priority conditions, all the other are the redundancy backup link, and the bridge port that connects the redundancy backup link in the port status module loop is set to blocked state, and network is trimmed to loop-free tree topology structure.

2. link redundant control method according to claim 1; It is characterized in that; If do not receive the BPDU message that bridge sends at the appointed time; Judge that then respective bridge breaks down, port status module transmitting control commands recovers the port get clogged, priority be provided with module reselect satisfy priority conditions optimal path as communication link.