Analyses of Subway BAS System Network Framework and IP Address Allocation Xin-hong YANG 1,* and Yuan GAO 2

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1 2016 International Conference on Applied Mechanics, Electronics and Mechatronics Engineering (AMEME 2016) ISBN: Analyses of Subway BAS System Network Framework and IP Address Allocation Xin-hong YANG 1,* and Yuan GAO 2 1 Shenyang Polytechnic College, No.32 Laodong Road, Shenyang City, College of Information Engineering Shenyang University, No.21 Dadong District Wanghua South Street, Shenyang City, 1100 *Corresponding author Keywords: Network structure, BAS, IP address planning. Abstract. This paper takes Shenyang subway BAS system as the background and introduces the BAS system network architecture. The price of star structure is better than the price of ring structure by comparing the backbone network real-time with security. Propose distribute scheme of subway station IP address and reasonable allocation of IP address, which can improve the efficiency of BAS system implementation and reduce risk. This allocation schemes of IP address which designs the same kind of subway station has a higher degree of referential significance. Introduction Network communication is the main part of forming BAS system and support three layer structure of BAS system. It is the basic platforms which transmit all kinds of data. Desirable SP network structure is the key which can realize the BAS system performance indicators. At the same time, in order to conveniently manage and monitor. Reasonable distribution of terminal device network address of each station is necessary. A good pattern of network distribution can greatly reduce the workload of equipment maintenance and raise working efficiency. Network Structure Analysis of BAS System The network system of Subway BAS system [1] adopts the distributed network structure which is composed of backbones (communication network), Central LAN and station-level LAN. Network Devices Control center set up two kits three layers of industrial Ethernet switch which have network management and they are connected by the way of Redundant and Hot-Standby. It realize the center redundancy connect the Ethernet with backbone. In order to effectively prevent the broadcast storm in LAN. It has a subnetting [2] control center and station with VLAN technology. But the sub-division prevents exchange between control center and station. So it need adopt three layers equipment in control center. Although three-ply switches and routers are able to realize communication of between the subnet, but three-ply switches combine packet processing function of router with speed advantage of switch. It can implement high-speed forwarding of packets and solve the bottleneck problem of network which low speed and complex of traditional router cause. Each station set two second floor of industrial Ethernet switches which has NM s functions in station control room, A side ring control room, B side ring control room (as shown in Figure 1). es use bottom allied RJ5 electricity mouth joint station network equipment and use top allied redundant optical fiber interface constitute fiber redundant ring net. The communication equipment of station is relatively scattered.twisted-pair connects each switches cannot satisfy requirement of communication distance (as far as 100 m) and communication rate.the fiber optics transmission can effectively solve this problem. Using rapid spanning tree technology of loop network and switch

2 accelerate the rate which make Ethernet loop fault convergence. That the network healing time less than 100ms improve reliability of network when the network node has a failure. Control Room of station Access to the backbone optical fiber ring network A side ring control room B side ring control room Figure 1. Network structure of station. LAN LAN is a set of computer and other equipment which are connected by communication line and distribute in limited region. Among devices can realize data transmission by network. Common LAN include the Ethernet, token-ring and Token Bus. The central level and the station-level adopt Dual redundant star or Ring Ethernet. Each termination is inserted backbones by switch with redundant mode. With long time development of Ethernet, whether improvement of agreement or research of transport and transceiver have grown pretty mature, it s reliability and stability can meet the requirement of BAS system. Now almost all of monitoring equipment can support Ethernet. Node of different speeds can seamless connectivity and needn t transform equipment. So networking is very easy. BAS system requires response time of communication which is between the central control system and the station monitoring system less than 2 seconds. Real-time doesn t require very high; it s easy to satisfy the requirement with 100M high speed Ethernet. Backbone Backbone is multi-service network. It doesn t only have data but also have voice and video image. Coverage areas can get dozens of kilometers. Backbone is provided the required whole line channel by BAS system which is communication system. Monitoring information of each site is loaded into transport layer devices of communication system (such as OTN and SDH and RPR, etc.). It achieves data transmission of between control center and station. Communication system can provide two kinds of networks topology of redundant star or ring. Star-Topology is regarded as central node by switch of control center. The switch of other station which are regarded as children nodes connect central node spotting. Loop structure is a closed loop which is formed by central switch and switch of each station through point-to-point laid end to end. This construction make shared medium compose circular connection. The data which travel in one direction transfer among various nodes in the loop. Message transfer one node from the other node (as shown in Figure 2).

3 OCC Control Center OCC Control Center A A B C BAS Backbone B C BAS Backbone Station C Station A Station B Station Station C Station A Station Station B Star Network Topologies Ring Topology Figure 2. Topological structure chart of star and circle. Performance of two kinds of topological structure can be compared and analyzed through the following two points: Real-time: BAS system request that the time of BAS control response less than 2.8s (the time of BAS control response is the time which is from central BAS workstation issue orders to station controller outputs action). According to communication system provide bandwidth for BAS system. Response time of data tag is tested in control center monitoring work-station. The label value will be accumulated one time when data response one time. It finally can get accumulated time for 1000 times. As shown in Figure 1.through response-time results of two kinds of topological structure could see that response time of star-topology is 0.59s for once time and response time of DT-Ring is 0.88s. Because of information sources of DT-Ring serially across every node in the loop. Transfer rate of information will be influenced under the condition of equal network bandwidth when ring nodes are too much and response time of network is extended. As shown in table 1. Table 1. Compare response time of star topology with response time of ring topology. Topology Total bandwidth(m) Count Time(s ) Star 230l Ring Security: Star topology is adopted. The entire network is divided into subnet by the center three-layer of switch through VLAN technology. Among the subnets are separated from each other. The three-layer of switch of control center is regarded as general node of loop networks. Under the premise which assures communication between every station and control center, each station couldn t be isolated from each other by WLAN technology [3]. All of station will be influenced when Cyber Storm assault a station. Based on the analysis of the above performance, ring type structure and star structure can be enough to meet the performance requirements of the BAS in real time. Under the same configuration, although ring structure can save network cost, but the network security performance is far below the star structure. If you want to improve their safety, they must be configured three layers switch in each station, which will certainly increase the higher cost, so the performance price ratio of the star structure is better than that of ring structure. IP Address Assignment of BAS System This model adopts subway lines of the star network topology structure. Its center is the three layer switch and its station adopts the two layers switches. IP address planning for the entire line[], and the use of three VLAN technology, make the station isolate logicality.

4 Site Planning Principles Good or bad planning for a system network directly affect the network performance, network expansion and network management and also will affect the further expansion of network applications. In the BAS system, planning IP address network generally follows the following principles: (1) Uniqueness: The serial number only exists in the BAS system. (2) Simplicity: Easy management of address assignment avoid the complex way of mask in the trunk (3) Scalability: Address assignment have allowance in each level for taking into full consideration to the needs of the future line extension and station extension. () Unitarity: The same terminal IP address of the same equipment for different stations is beneficial to realize allocation and management of IP address. The Way of Site Planning Because of relatively fixed the subway station network equipment and point-to-point connections of each station and control center through the switch port, VLAN divisions based on the port is a reasonable choice. Each station network adopted redundant configuration and one active plus one standbys. When it comes to communication failure, can realize the dual network redundancy switching. Comprehensive the above consideration, each station of subway are classified into different VLAN. In order to avoid the occurrence of broadcast storm, the station is isolated from each other. At the same time, each station's main/standby network was isolated. Using the function of control center three layers switch VLAN, each station is divided into two VLAN. According to the practical application of the subway BAS system [5] and demand, can use the following address planning mode: Address planning method with the station and line as the leading, the main / auxiliary network as a means, uses bit IP address mask. For example: IP address format: A.B.C.D/, A represents different subway lines. B represents different stations. C represents the distinguish of Active/Standby network. D represents the terminal address number. For example, the terminal equipment IP address of Shenyang Metro Line 1 is shown in Table 2. Table 2. The IP address planning of the part of station terminal equipment. Station number Device name IP 1 master control PLC NOE(master) / 2 master control PLC NOE(Standby) / 3 A-end PLC NOE(master) / A-end PLC NOE(Standby) / 5 B-end PLC NOE(master) / Gateway / IP address planning is an important part of BAS system network design [6]. Good IP address planning can effectively control network conflict and the spread speed of the virus, reduce unnecessary management and maintenance work, and improve work efficiency. Using three layers switches of VLAN function to realize network address planning, can effectively limit the broadcast. VLAN was divided the thinner, the smaller the range of radio, while it was located more easily after problems.

5 Conclusion In this paper, through the research on the network structure of Metro BAS system, an economic and effective network structure was determined according to field test and analysis. Selecting Ethernet LAN for center and station can better meet the performance index of the BAS system. Backbone adopts star structure.this structure on performance/price ratio is better than that of ring structure. According to IP network planning principles and the actual demand of BAS system, realize reasonable planning of the BAS system network address. References [1] Qu Lidong, The subway station structure design of BAS, Urban rapid rail transportation, [2] Gan Yongmei, etc., The fieldbus technology and its application, Mechanical industry publishing house, [3] Ma Sugang, Research and simulation of VALN technology, Manufacturing automation, [] Han Junhao, Research and implementation of IP address management system, Beijing University of posts and telecommunications, [5] Anonymous, Introduction of Subway BAS system, China transport technology net, [6] Wang Yixin, Power wireless virtual private network networking architecture and IP address assignment, The power of information and communication technology, 201.

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