JP2005012488A - Communication system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a communication system capable of providing a more sophisticated function to an existing communication system resource. <P>SOLUTION: The communication system including a server computer 6 and a plurality of client computers 20 to 23 for receiving the provision of information from the server computer adopts a communication protocol TCP/IP as a communication protocol and utilizes a subnet mask so that the server computer can make broadcast communications to a plurality of the client computers. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a communication system, and in particular, an existing communication system resource, for example, an existing system that is constructed so as to provide information for a railway operator to manage the operation status of a train in real time to a terminal installed in a station through a dedicated in-house line. The present invention relates to a communication system useful for enhancing the functions of communication system resources.
[0002]
[Prior art]
For example, a railroad operator abbreviated as JRXX is provided with an operation status display system so that the operation status of a train can be displayed on a terminal installed at a station. The operation status display system is an information collection and management system consisting of a device (PRC) that receives and manages train operation status in real time, a device that performs automatic control of the train and grasps the position of the line (station control device), etc. Based on the information obtained from the system and this information collection and management system, the train line information and delay information are transferred from the server computer to the terminal (client computer) installed in the station through a communication network using a dedicated in-house line (JR line). The communication system is provided. In the communication system, HDLC (High-Level Data Link Control) is used as a communication protocol, and information provision from the server computer to each client computer can be performed by broadcast communication. Although not directly related to such a communication system, examples disclosed in Patent Documents 1 to 3 are known as communication technologies related to broadcast communication and multicast communication.
[0003]
[Patent Document 1]
Japanese Patent Publication No. 2002-232477 [Patent Document 2]
JP 2000-354063 A [Patent Document 3]
JP-A-9-107390 [0004]
[Problems to be solved by the invention]
In the communication system in the operation status display system used by the railway operator, HDLC is used as the communication protocol as described above, and information can be provided from the server computer to each client computer by broadcast communication. Therefore, efficient communication can be performed in terms of providing information from the server computer to each client computer. However, on the other hand, the communication between the server computer and the client computer is a one-way communication only for unilaterally providing information from the server computer to the client computer. That is, the server computer cannot obtain the survival information from the client computer side and monitor the state of the client computer, for example, and there are some functions that are insufficient.
[0005]
The present invention has been made against the background of the above circumstances, and is intended to make existing communication system resources such as communication systems in the above-described railway operator operation status display system more sophisticated. It aims at providing the communication system which enables.
[0006]
[Means for Solving the Problems]
For the above purpose, in the present invention, in a communication system including a server computer and a plurality of client computers receiving information from the server computer, TCP / IP is used as a communication protocol and a subnet mask is used. Thus, broadcast communication from the server computer to the plurality of client computers can be performed.
[0007]
In the present invention, as described above, by using a port in the communication system, broadcast communication can be performed only for a specific client computer or client computer group in the plurality of client computers.
[0008]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below. FIG. 1 shows a configuration example of an operation status display system for a railway operator to which a communication system according to the present invention is applied. The operation status display system is a PRC1 that receives and manages the train operation status in real time, a monitoring console 2 that monitors the operating state of the components of the system, a control console 3 that is used for manual control of the train route, and a change in the train diagram. Information collection management system consisting of the GD4 used in the system, and the station control device 5 that performs automatic control of the train and grasps the position of the on-line, and on-track information and delay of the train based on the information obtained by this information collection management system It consists of a communication system that provides information and the like from information CS (server computer) 6 to station TIDs (client computers) 20 to 23 installed in the station through a dedicated in-house line N that is a communication network.
[0009]
The configuration of the information CS6, the dedicated in-house line N, and the station TIDs 20 to 23 is the same as the communication system in the conventional operation status display system. In the present invention, the upper router 7 is provided on the information CS6 side of the communication system, and a segment (subnet) including the information CS6 and the upper router 7 is formed. Further, the lower routers 16 to 19 are provided on the station TIDs 20 to 23 side, and the lower routers 16 to 19 provide a plurality of segments related to the station TIDs 20 to 23 (in the example of the figure, the segment including the lower router 16 and the station TID20, the lower routers). 17, a segment including the station TID 21, a segment including the lower router 18 and the station TID 22, and a segment including the lower router 19 and the station TID 23). Also, because the signal formats are different, modems 8 to 11 and modems 12 to 15 are interposed between each segment and the dedicated in-house line N. In the example shown in the figure, one subordinate router is subordinate to one station TID, but there is naturally a case where one subordinate router is subordinate to a plurality of station TIDs.
[0010]
In the present invention, the hardware configuration of the communication system is as described above, and TCP / IP is used as the communication protocol. That is, by using TCP / IP communication, two-way communication can be performed between the information CS6 and the station TIDs 20 to 23, and the information CS6 is transmitted, for example, from each of the station TIDs 20 to 23 using the bidirectional communication function. The communication system is highly functionalized by acquiring information and monitoring the status of each of the station TIDs 20-23.
[0011]
For TCP / IP communication, it is necessary to set individual network addresses for each segment on the network. In the present invention, the network address is set using a subnet mask so that broadcast communication can be performed under TCP / IP communication. This will be described below.
[0012]
In TCP / IP, for example, in the case of class A regarding the IP address, the first 1 byte (1 octet) is the network address, and in the case of class B, the network address is up to the first 2 bytes (2 octets). It is a principle. FIG. 2 shows an example in which an individual network address is set as a class B for each segment based on this principle. As shown in the example in the figure, the subnet mask is 255.255.0.0, the network address of the segment including the information CS6 and the upper router 7 is 173.11, and the network address of the segment including the lower router 16 and the station TID20 173.12, the network address of the segment including the lower router 17 and the station TID21 is 173.13, the network address of the segment including the lower router 18 and the station TID22 is 173.14, and the network of the segment including the lower router 19 and the station TID23 The address is set individually as 173.15.
[0013]
In contrast to the setting based on such a principle, in the present invention, the subnet mask is used so that the first 3 bytes (3 octets) can be used as the network address of the segment on the station TID 20-23 side. To do. That is, for the station TID side segment formed by the lower routers 16 to 19, a local network address is set by using a subnet mask so that up to 3 octets can be used as a network address. An example is shown in FIG. In this example, the subnet masks of the lower routers 16 to 19 and the station TIDs 20 to 23 are set to 255.255.255.0, and up to 3 octets are used as the network address. The network address of the segment including the lower router 16 and the station TID 20 is 173. .11.57, the network address of the segment including the lower router 17 and the station TID21 is 173.11.58, the network address of the segment including the lower router 18 and the station TID22 is 173.11.59, the lower router 19 and the station TID23 The network address of the segment to be included is individually set as 173.11.60. That is, the IP address of each segment on the station TID side is 173.11 common to 2 octets. Therefore, when viewed from the information CS6, each segment on the station TID side has the same network address, thus forming a single network.
[0014]
FIG. 4 is an explanatory diagram of a case where a message (information) having the same content is transmitted to the station TIDs 20 to 23 by the class B network address set as shown in FIG. In the network address setting as shown in FIG. 2, the network address of each segment of the transmission destination is different. Accordingly, it is necessary to individually transmit the telegrams 24 to 27 to each segment, and the processing load of the information CS6 increases accordingly, and the transmission time becomes longer and the communication efficiency also decreases.
[0015]
FIG. 5 is an explanatory diagram of a case where a message having the same content is transmitted to the station TIDs 20 to 23 by the class B network address set by using the subnet mask as shown in FIG. With the network address setting of FIG. 3, broadcast transmission is possible. That is, since the network address of each segment of the transmission destination is 173.11 when viewed from the information CS6 and is the same, the transmission destination address is 173.11.25.255 from the information CS6, that is, the network address portion is 173. .11 and the host address part is 255.255, and one telegram 28 is transmitted, the telegram 28 can be transmitted simultaneously to each segment. Therefore, the processing load on the information CS6 can be reduced and the transmission time can be shortened compared to the case of FIG.
[0016]
The provision of information from the information CS6 to the station TIDs 20 to 23 may not only provide the same content information to all the station TIDs 20 to 23 but also limit the station TID to be provided according to the type of information. . That is, the information provided from the information CS6 to the stations TID20 to 23 includes information commonly used by all the stations TID20 to 23 and information used by a specific station TID or station TID group in the stations TID20 to 23. Yes, it is necessary to control the provision of information from the information CS6 to the stations TID20 to 23 according to the type of information. In this regard, the present invention uses a port. FIG. 6 shows an example in which the information providing station TID is allocated using a port. In the example of the figure, five ports with port numbers 40101 to 40105 are used, the port with port number 40101 is for information common to all stations of station TID20 to 23, and the port with port number 40102 is information common to only stations TID20 and 21 The port number 40103 is for information common only to the station TIDs 20, 22, 23, the port number 40104 is for information common only to the station TIDs 22, 23, and the port number 40105 is only for the station TIDs 21, 23 It is for common information.
[0017]
FIG. 7 is an explanatory diagram of a case where the same telegram is transmitted only to a specific station TID or a station TID group in the stations TID20 to 23 using the port. For example, it is assumed that a message is transmitted from the information CS6 with the destination address set to 173.11.25255 and the port number set to 40103. This message is sent to all the stations TID20 to 23 as broadcast communication. However, the ports with port number 40103 are open at station TIDs 20, 22, and 23, and the port with port number 40103 at station TID21 is not open. For this reason, only station TID20,22,23 will receive this message | telegram. On the other hand, at the station TID21, since the port of port number 40103 is not open, a message is not received, and an error notification (ICMP: Internet Control Message Protocol) 29 is issued. In the present invention, the error notification 29 is discarded by the upper router 7. In the table attached to FIG. 7, the circles and crosses indicate that the ports are open (O) and non-open (X).
[0018]
In this way, by using a port, it is possible not only to broadcast transmission to all the stations TID20 to 23 but also to broadcast transmission only to a specific station TID or station TID group in the stations TID20 to 23. It becomes. For station TIDs that do not need to receive broadcast transmission from information CS6, the corresponding ports are not opened so that reception can be avoided at the hardware level. It is not necessary to perform a discarding process by software, and the processing load on the station TID can be reduced accordingly. Also, since the error notification from the station TID is discarded by the upper router 7, the processing load on the information CS6 can be reduced. Here, in order to use the port as described above, the upper router 7 needs to have a port forwarding function in addition to the IP forwarding function. Therefore, a router having such a function is used as the upper router 7.
[0019]
【The invention's effect】
As described above, according to the present invention, bidirectional communication can be performed between a server computer and a plurality of client computers receiving information from the server computer by using TCP / IP as a communication protocol. As a result, the server computer can monitor the state of the client computer, and so on, and the communication system can be enhanced. In the present invention, broadcast communication is enabled by using a subnet mask under the TCP / IP protocol. For this reason, communication efficiency can be improved by shortening the transmission time when providing the same information to a plurality of client computers. Further, with respect to this broadcast communication, selective broadcast communication to a plurality of client computers can be performed by using a port. Therefore, broadcast communication according to the type of information becomes possible, and the functionality of the communication system can be further enhanced. Therefore, according to the present invention, it is possible to construct a communication system with higher functionality by utilizing existing communication system resources such as a communication system in an operation status display system of a railway operator.
[Brief description of the drawings]
FIG. 1 is a diagram showing a configuration example of an operation status display system for a railway operator to which a communication system according to the present invention is applied.
FIG. 2 is a diagram showing an example when a network address is set for each segment using up to 2 octets.
FIG. 3 is a diagram illustrating an example in which a network address is set for each segment using up to 3 octets by using a subnet mask.
FIG. 4 is an explanatory diagram of a case where a telegram having the same content is transmitted to a station TID using the network address set as shown in FIG.
FIG. 5 is an explanatory diagram of a case where a telegram having the same content is transmitted to a station TID using the network address set as shown in FIG. 3;
FIG. 6 is a diagram showing an example of assigning information providing station TID using a port;
FIG. 7 is an explanatory diagram of a case where the same telegram is transmitted only to a specific group in the station TID using a port.
[Explanation of symbols]
6 Information CS (server computer)
7 Higher routers 8 to 15 Dedicated line modems 16 to 19 Lower routers 20 to 23 Station TID (client computer)
N Dedicated company line (communication network)

Claims (2)

In a communication system including a server computer and a plurality of client computers receiving information from the server computer,
A communication system, wherein TCP / IP is used as a communication protocol and broadcast communication from the server computer to the plurality of client computers can be performed by using a subnet mask. The communication system according to claim 1, wherein broadcast communication can be performed only for a specific client computer or client computer group in the plurality of client computers by using a port.

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