ring topology-based redundancy ethernet

1. INTRODUCTION Nowadays, almost of the distributed control systems

use high safety network system to communicate between its objects from a sensor to sub-control system. Therefore the importance of high safety network system is swing upward steadily. The use of Ethernet system in high safety network system with standardized protocols is getting very high attention these days because of its several advantages like as high performance, flexible connectivity, interoperability and low price. [1][2][8][9]

In industrial network, on the other hand, the Ethernet technology should overcome the dependency on switch or hub to decrease risk from troubles of central system as switch. In order to escape from the dependency on switch and implement high safety network system, the switch should be eliminated from the network system. So the switch function is internalized network modules based on Dual-Port Ethernet to configure daisy-chained line topology network. However the daisy-chained line topology is unstable against link-fault caused by cutting media cable or power off. Therefore the ring topology that can support redundancy path has been considered like as token ring [7] and ring switch. [3][4][5]

In ring topology network, there are two issues to make high safety network system. One is how to

prevent unexpected packet-storm in ring topology network. And another is how to minimize the path recovery time against link-fault.

In ring network topology, the broadcast packets can fall in unlimited loop, if they are not blocked or consumed by some network station. The major ring control scheme is logical polling [3] between master and slave and logical token pass [7] to prevent unexpected packet-storm in network.

In order to guarantee packet transmission using redundant paths, new packet path have to be recovered to guarantee packet transmission as soon as possible. Therefore path recovery time is very important in ring topology network. Most of todays intelligent ring switches use a protocol known as fast spanning tree to address redundant paths and assist in directing data in the proper direction. However this fast spanning tree has minimum 250ms recovery time because they frequently send management packets to check network status, they can find out the link-fault after checking response time-out on the remote modules in network. [2][5] This recovery time is not suitable for industrial network but suitable for office network.

Measurement and control applications are increasingly using distributed system technologies such as high safety network system, local computing, and

Ring Topology-based Redundancy Ethernet for Industrial Network

Geon Yoon1 , Dae Hyun Kwon2 ,

Soon Chang Kwon3 , Yong Oon Park4 and Young Joon Lee5

1 Advanced Platform Team, Central R&D Center, LS Industrial Systems.Co.,Ltd. Korea

(Tel : +82-31-450-7585; E-mail: [email protected]) 2 Advanced Platform Team, Central R&D Center, LS Industrial Systems.Co.,Ltd. Korea



(Tel : +82-31-450-7627; E-mail: [email protected]) 5 Automation Lab, Central R&D Center, LS Industrial Systems.Co.,Ltd. Korea

(Tel : +82-31-450-7628; E-mail: [email protected])

Abstract: Recently Ethernet system is getting very high attention for industrial network. Industrial customers are no longer satisfied with RS232 or RS485 data transmission; rather they are demanding the benefits of Ethernet connectivity. However the star topology of Ethernet is not flexible and not reliable for industrial network because of dependency on switch or hub.

This paper proposes the redundancy Ethernet system based on ring topology without switch or hub. And also proposes the new topology adaptation network management protocol (TANMP). The topology of the proposed redundancy Ethernet system can be flexibly changed from the ring topology to the line (daisy-chained) topology or opposite case. And also guarantees packet-transmission to its destination in spite of a link-fault. TANMP supports the simple hop count based routing function with high performance and manages network topology with minimum recovery time. In this paper, we implement the proposed TANMP and analysis performance of the proposed ring topology based redundancy Ethernet system for industrial network. Keywords: Ethernet, Ring Topology, Network Management Protocol, Industrial Network

SICE-ICASE International Joint Conference 2006Oct. 18-21, 2006 in Bexco, Busan, Korea

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distributed objects. Many of these applications will be enhanced by having an accurate system-wide sense of time achieved by having local clocks in each sensor, actuator, or other system device.

Therefore we propose ring topology Ethernet system and topology adaptation network management protocol (TANMP) with time synchronization based on full duplex flow control. [6] The topology of the proposed redundancy Ethernet system can be flexibly changed from the ring topology to the line (daisy-chained) topology or opposite case. And also guarantees packet-transmission to its destination in spite of a link-fault. TANMP supports the simple hop count based routing function with high performance and manages network topology with minimum recovery time.

Finally, we analysis the performance of the proposed ring topology based redundancy Ethernet system.

2. FULL DUPLEX FLOW CONTROL

The most important idea of this paper is full duplex flow control scheme. Todays, there are many kinds of switches with high performance. Their most important idea is also full duplex flow control scheme shown as figure 1.

Fig 1. Block diagram of Realtek 8305 switch controller

In full duplex flow control system, packet transmission and reception are simultaneously possible without any interruption. We employ this full duplex flow control scheme into our network interface module shown as figure 2.

Fig 2. Full duplex control.

The MAC controller has a bridge function to relay the received Ethernet frames to another Ethernet port. This hardware technology can considerably increase

performance of the central process unit (CPU) because of independent direct memory access function for only packet buffering. If the CPU has to move the packets from an Ethernet port to another one, the interrupt overhead time from Ethernet port will be considerably increased. Therefore this Dual-Port Ethernet hardware architecture increases the performance of the network by reducing packet delay per hop. 3. RING TOPOLOGY BASED REDUNDANCY

NETWORK SYSTEM 3.1 Ring switch based network system

Todays ring topology network system is composed of ring switch shown as figure 3. Each control system communicates other control systems via intelligent ring switches.

Fig 3. Ring switch based network system

When the intelligent ring switches are initializing, they elect the blocking switch, which blocks packet-relay to prevent from unlimited packet loop. However if one of switches fall in fault status like as power problem or halt, whole nodes that connected to the faulted switch can not communicate other control systems. 3.2 Proposed ring topology network system

We remove the switch from control network system to overcome dependency on switch. We internalize the of switchs functions to our Dual-Port Ethernet module shown as figure 4. Each Ethernet port is exactly independent. This module can control packet relay between two ports based on topology adaptation network management protocol (TANMP) described sub clause.

Fig 4. Dual-Port Ethernet module

In this paper, we implement new ring topology based redundancy Ethernet system for industrial network


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shown as figure 5. And we support ring topology as well as line (daisy-chained) topology and star topology shown as figure 6.

Fig 5. Proposed ring topology network system

Fig 6. Line(daisy-chained) topology

3.3 One-Fault tolerance scenarios in ring topology

Whole network nodes in ring topology network have same priority to access medium. Therefore network nodes can transmit packet when they want because they use full duplex control scheme.

We have two major scenarios to consider how to control ring topology network. One is local link-fault and another is remote link-fault.

Fig 7. Local link-fault

Local link-fault means that the link between local node and adjacent node is faulted. When the node senses local link-fault in the proposed ring topology network system, it broadcasts the message of The network status is changed from ring to line. And then it recovers the path another redundant path immediately. The figure 7 shows local link-fault. No.1 path of figure

7 means the proper path based on hop count. When local link-fault is sensed as No.2, newly redundancy path is recovered as No.3 in figure 7.

Fig 8. Remote link-fault

Remote link-fault means that the link between remote node and its adjacent node is faulted. After link-fault shown as figure 8, whole nodes in network receive the message of The network status is changed. So whole nodes can rearrange its routing table and then send packet to newly recovered path.

4. TOPOLOGY ADAPTATION NETWORK MANAGEMENT PROTOCOL (TANMP)

4.1 Stack of TANMP

The proposed topology adaptation network management protocol (TANMP) manages network status and node status. It controls the ring topology network to eliminate the unlimited loop packets. When network topology is changed from ring to line (daisy-chained) or opposite case, TANMP rearranges the routing table for the destination address of Ethernet frames. TANMP is composed of TANMP core, Transmitter controller, routing manager, packets relay controller and four data base shown as figure 9.

Fig 9. TANMP stack


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TANMP core manages node state machine according local hardware event and network event.

The transmitter controller controls packet-transmit according destination of packet by referring to simple routing table.

The routing manager manages the position of the other nodes except itself based on hop counter in redundancy Ethernet system.

Packet relay controller is worked by TANMP. TANMP core controls whether blocks packet relay or not.

If the node is elected as the ring manager node, it logically blocks to eliminate unlimited loop packets. The other nodes which are not elected as a ring manager, rearrange its routing table through the routing manager object because of the logical blocking path.

4.2 Path Recovery Time

When link-fault caused by cutting media cable or power off is occurred during communication between nodes, the packet path should be rearranged to get minimum response time as soon as possible.

Figure 10 shows path recovery time when local link fault event is occurred. TANMP core change its state and network state from ring to line (daisy-chained) and then recovers path through routing manager. The recovery time is the time interval from the link-fault to new data reception. We can find the recovery time is about 1ms.

Fig 10. Path Recovery Time

5. Conclusion

The paper proposes the redundancy Ethernet system based on ring topology without switch or hub. And also proposes the new topology adaptation network management protocol (TANMP). The topology of the proposed redundancy Ethernet system can be flexibly changed from the ring topology to the line (daisy-chained) topology or opposite case. And also guarantees packet-transmission to its destination in spite of a link-fault with minimum recovery time. Therefore we hope to this new ring topology Ethernet network system will replace traditional ring topology network system. And in coming days, it will be base technology for redundant based high safety network system.

REFERENCES [1] Kai Hansen. Redundancy Ethernet in Industrial

Automation, Emerging Technologies and Factory Automation, Vol. 2, pp. 941-947, 2005. Sept

[2] A white paper Delivery of Data in industrial Applications, MICREL.

[3] Hirschman Ring Switch www.hirschmann.com [4] Hilscher netX, www.hilscher.com [5] Profinet, Industrial Ethernet, SCALANCE,

www.automation.siemens.com/net/index_00.htm, Siemens.

[6] IEEE Standard 1588 Precision Clock Synchronization Protocol

[7] IEEE Standard 802.5 Token Ring [8] IEC PAS 62407, Real-time Ethernet control

automation technology(EtherCAT) [9] IEC PAS 62408, Real-time Ethernet

Powerlink(EPL) [10] IEC PAS 62409, Real-time Ethernet for Plant

Automation(EPA) [11] IEC PAS 62401, Real-time Ethernet SERCOSIII [12] IEC PAS 62413, Real-time Ethernet -

EtherNet/IP with time synchronization.


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ring topology-based redundancy ethernet

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