JPH06152615A - Data transfer method in local area network having plural transmission lines - Google Patents

Abstract

PURPOSE:To use plural transmission lines efficiently by providing a link control function, a transmission line load measurement function, a transmission line changeover control function in a station and allocating a link to a transmission line with a lowest load. CONSTITUTION:A transmission line whose load is lightest among transmission lines 6-1-6-n measured by transmission line load measurement sections 7-1-7-n of a station 1 is selected and its number is written in a communication table 11. Then a link setting request frame is generated based on the content of the table 11 and sent through the transmission line. When a link set request frame is received by a communication destination station, the communication destination station decides its own link address and sends a link acknowledge frame to the station 1. Upon the receipt of the acknowledge frame, the station 1 writes a communication destination link address to the table 11 and then the transmission line in use is decided. Plural transmission lines are used effectively by distributing a link depending on the load of the transmission line impartially in this way.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a local area network having a plurality of transmission lines, and more particularly to a method of using the transmission lines in data transmission between stations.

[0002]

2. Description of the Related Art Generally, when a plurality of transmission lines are used for communication between computers as shown in FIG. 9, there are two methods for controlling the selection of the transmission lines. The first method is a method of controlling the selection of a transmission path by a station, and the second method is a method of controlling the selection of a transmission path by layer software (at a network level or higher) on a computer.

In the first method, the transmission transmission line is changed for each transmission access control frame (MAC frame) so that the load on each transmission line becomes equal. The original transmission access control of the local area network employs a method of confirming the response for each frame or transmitting the frame without confirming the response, and therefore the frame order control is not performed. However, when the transmission path is changed for each transmission access control frame using multiple transmission paths, when several transmission access control frames form one upper layer message, the transmission access frames that arrive at the same destination are Due to the variation of arrival time, the order of frames may be overturned and the order of assembling messages at the destination may be incorrect. Therefore, it is necessary to control the order of the transmission access control frames at the station.

On the other hand, the second method is a method of allocating the transmission path to be used for each connection of the upper layer, but the processing overhead in the upper layer software becomes large. In particular, it is necessary to constantly collect and store load information of transmission lines by software on the computer side, and allocate transmission lines in connection units so that the load of each transmission line is balanced when setting the upper layer connection.

[0005]

One of the drawbacks of the above two methods is to control the order of transmission access control frames when switching between a plurality of transmission lines at a station in order to efficiently control the uniform load of a plurality of transmission lines. It is necessary to solve the complexity of the transmission access control caused by the need of the above and the complexity of the control caused by the need for the computer side software to constantly collect the transmission line load information.

[0006]

In order to solve these problems, a station control function is provided, a link and a transmission line are made to correspond to each other, and sequence control in a transmission access control unit is not necessary, and It is necessary to perform the above function and the switching control of multiple transmission lines independently of the upper layer in the range of the lower layer.

In the present invention, in order to realize this, the station is provided with a link control function, a transmission line load measuring function, and a transmission line switching control function, and the transmission line with the least load is selected at the time of link setting. A method of assigning a link to a transmission line is adopted. Further, a communication table containing correspondence information of links and transmission paths is installed in the station and managed by the link control unit. The communication table stores the communication destination station address and the communication destination link address, which are link management information, in addition to the correspondence information between the transmission path and the link.

The method according to the present invention will be described below with reference to FIGS. In FIG. 3, first, before starting data transfer between stations, each computer sends a link setting request command to a subordinate station in order to set a link with the communication destination station and a communication destination station address and its own link address. And send. The station under the computer accepts this link setting request (the station that receives the link setting request from the computer in this way is called the sending station), and the destination station address is set in the area corresponding to its own link address in the above communication table. Is written (step S101). Further, the transmission line load measuring circuit selects the transmission line with the least load from the respective transmission lines (step S102), sets the selected transmission line as the transmission line to be used, and writes the transmission line number in the communication table (step S102). S103). Then, a link setting request frame header is generated from the contents of the communication table and transmitted using the selected transmission path (step S104).

Next, in FIG. 4, when the link setting request frame is received by the correspondent station (step S2)
01, S202), the communication destination station determines its own link address (step S203), and sends a link response frame including the link address (step S20).
4).

Referring again to FIG. 3, the station on the link setting side receives the response frame (step S105,
After S106), the communication destination link address is read from the content of the frame and the link address is written in the communication table (step S107). With this, a link is set up between the two stations, a transmission path to be used for the link is determined, and the end of link setting is reported to the computer (step S108). Computers use this link to transfer data.

Next, FIG. 5 shows a processing flow of data transfer using the set link. This data transfer accepts a data transfer command, an address corresponding to its own link address, and transmission path information from a computer (step S301), assembles a header in accordance with these, and sends it to a specified transmission path together with transfer data, as in the conventional method. (Step S302). Then, the reception of a data response frame is waited for (step S303), and if there is a reception addressed to the computer (that is, if the judgment result of step S304 is "Yes"), a data transfer end report is sent to the computer (step S305). ).

[0012]

According to the above method, since the upper layer telegram is transmitted in the link unit, that is, in one transmission path, the frame order inversion in one telegram does not occur, and the transmission access control frame order control is required. There is no. Further, since the link and the transmission path are managed in association with each other by the link control function in the station, it is not necessary for the software of the computer upper level to be aware of the transmission path selection.

[0013]

Embodiments of the present invention will be described below with reference to the drawings. The present invention can be applied to any transmission line topology, but in the following description, a ring topology will be used.

FIG. 1 is a schematic diagram of a station configuration of an embodiment of the present invention. The information frame and the token frame used in this embodiment are shown in FIG.

First, with reference to FIG. 1, an outline of the station configuration will be described. In the station 1, the computer interface section 2 has an interface function with the computer 3, such as an input / output interface. The link setting command and the data transfer command from the computer 3 are sent to the computer interface unit 2.
Accepted by. Transmission access control units 4-1 to 4-
n are provided corresponding to the transmission lines 6-1 to 6-n, respectively, and each fulfills a transmission access control function. The physical level protocol units 5-1 to 5-n also have transmission lines 6-, respectively.
It is provided corresponding to 1 to 6-n and has a physical level protocol conversion function of a transmission line, a transmitter / receiver, and the like. 7-1
7-n are transmission line load measuring circuits, each of which has a transmission line 6-n.
It has a function of measuring each transmission line load of 1 to 6-n.

Next, the communication control unit 8 mainly comprises a control unit 9, a link control unit 10, a communication table 11 and a transmission line switching unit 1.
It consists of two. Of these, the control unit 9 controls the entire communication control unit 8. The link controller 10 also manages links between stations using the communication table 11. Here, the communication table 11 is a table for setting and managing address information for links and transmission line numbers. FIG. 6 shows an example thereof. As shown in the figure, as the information managed for each link, the own link address SL, the destination station address DA, the destination link address DL,
The transmission line link address TL, the transmission line number transmission line TL, and the link free / busy display FV information are provided. The switching unit 12 connects the communication control unit 8 to the set transmission line (that is, the transmission access control unit, the physical level protocol unit or the transmission line) according to the transmission line number corresponding to the own link address in the communication table 11. The transmission line load measuring units 7-1 to 7-n measure the load of the transmission line corresponding to each by counting the number of frames received or relayed by the station per unit time. When the token passing method is used as the transmission path access method, it is also possible to measure the number of arrivals of the token frame on the transmission path per unit time at the station. In this way, the loads on the transmission lines are measured and the loads on the transmission lines are compared with each other, and it is determined that the transmission line with the shortest time is the freest.

FIG. 7 and FIG. 8 show an operation example and a data transfer operation example, respectively, in which a link and a transmission path are set in correspondence with each other according to the method of the present invention. The operation of this embodiment will be described below with reference to these figures and FIG. 1 showing an example of the configuration of the station and FIG. 6 showing the contents of the communication table. First, before starting data transfer between each station,
First, in order to set a link with the communication destination station, the computer 3 sends a LINK command of a link setting request to the subordinate station 1 under its own link address SL.
(= A) and communication destination station address DA (=
Send to station with B). Sending station A
At (station address A), a LINK command or the like is received by the computer interface and sent to the communication control unit 8. The link control unit 10 of the communication control unit 8 writes the communication destination station address B in the area where the own link address SL is a in the communication table 11.

Next, the transmission path is selected. Here, the selection of the transmission line refers to the load of each of the transmission lines 6-1 to 6-n measured by the transmission line load measuring circuits 7-1 to 7-n, and the load of the most of the transmission lines is selected. This is performed by selecting a transmission line having a small number (that is, a small token circulation time) and writing the transmission line number (“2” in FIG. 7) in the communication table 11-a.

Next, a link setting request frame is generated from the contents of the communication table 11, the transmission line switching circuit 12 is switched to the selected transmission line side, the transmission access control unit 4-2 corresponding to the second transmission line, the physical level. Protocol part 5
-2 and then to the transmission line 6-2.

When the link request setting frame is received by the communication destination station (station address B), the station B looks at each FV area of the communication table 11-b and searches for an empty link. That is, the area where the link free / busy display FV is V (empty link) is searched for, and the FV
To F (link in use). The own link address SL (= b) which is the address of the link changed from this empty link to the used link is set as the set link address of the station B requested by the station A. Then, from the header information of the received link request frame, the destination station address DA (= B) and the destination link address DL (=
b) Write the contents of the transmission line number TL (= 2). Further, in order to convey the link address of the station B side to the A side, a link response frame addressed to the station A is assembled,
It is sent to the transmission path 6-2 designated by the content “2” in the TL column of the communication table.

At the station A, when the link response frame is sent, the communication destination link address is written in the communication table 11-a. As a result, the link between the station A and the station B is set, and the transmission path used for the link is determined. The above link setting process is called a link phase.

Next, referring to FIG. 8, the data transfer phase for transferring data using the link thus set up will be described. First, a computer sends a SEND command to a station under its control together with its own link address and transfer data. At station A, the computer interface 2
Then, the command is received and sent to the communication control unit 8. In the communication control unit 8, the header is assembled by looking at the area of the own link address of the communication table 11, the transfer data frame is generated,
The transmission access control unit 4-corresponding to the transmission line 6 (transmission line 6-2 in the case of FIG. 8) indicated by TL of the communication table 11
2, the transmission line 6 via the physical level protocol unit 5-2
-2.

[0023]

The link control function, the table storing the correspondence between the links and the transmission lines, the transmission line load measuring function, and the transmission line switching control function are provided in the station so that the load is the least when setting the links. By selecting a transmission line, assigning a link to that transmission line, and evenly distributing the links to the transmission lines according to the load of the transmission lines, it has become possible to use multiple transmission lines efficiently. . By adopting this method, it is not necessary to control the order of the MAC frames, and it is not necessary to constantly collect the transmission line load information in the computer upper layer software.

[Brief description of drawings]

FIG. 1 is a schematic diagram of a configuration of a station that realizes a data transfer method according to an embodiment of the present invention.

FIG. 2 is a frame format of a transmission frame and a token frame flowing on a transmission path.

FIG. 3 is a processing flow in a station for setting a link between stations so as to correspond to a transmission path.

FIG. 4 is a processing flow in a station for setting a link between stations so as to correspond to a transmission path.

FIG. 5 is a flow chart of a station for data transfer using a link set for a transmission path.

FIG. 6 is a configuration diagram of a communication table in a station in this embodiment.

FIG. 7 is an explanatory diagram of a link setting phase for setting links between stations so as to correspond to transmission paths.

FIG. 8 is an explanatory diagram of an operation example of data transfer using the link set in the link setting phase.

FIG. 9 is a local area network system having a plurality of ring-shaped transmission lines.

[Explanation of symbols]

3 ... Computer, 8 ... Communication control unit, 4-1 to 4-n ... Transmission access control unit, 7-1 to 7-n ... Transmission line load measuring unit, 5-1 to 5-n ... Physical level protocol unit, 6-1 to 6-n ... Transmission line, 9 ... Control unit, 10 ... Link control unit, 11 ... Communication table, 12 ... Transmission line switching unit.

Claims (1)

[Claims] 1. A plurality of stations are provided, one computer is connected to each computer side connection port, and a plurality of transmission lines are connected to each transmission line side connection port. The stations are connected via these plural transmission lines, and the control for data transfer between computers via these transmission lines is shared by the computer and the station, and each station is subordinate. A local level that allows a computer to access multiple transmission lines via a station by performing physical level control and transmission access control, which are layer control, while controlling a network layer or higher, which is a higher layer control. In the area network, each station should be A link control function for controlling connection-oriented communication that performs data transfer after completing the link setting phase for setting a logical link, a function for associating a link with a transmission path, a destination station address, The communication table stores link information consisting of a destination link address and the number of the transmission path used by the link, and a circuit for switching a plurality of transmission paths in correspondence with the used link is provided. When starting, each computer sends a command for link setting to the stations under its control in advance, and the station writes address information in the communication table as a transmission path used for communication with the communication destination. The unit time of a frame received or relayed by the station 'S select the lowest transmission path of the load represented by the number, the updates the corresponding transmission path and link communication table to create and send link setting request frame, the station which has received the link setting request frame,
Selects a vacant link of the station, writes address information from the header of the link setting request frame to the communication table, sends a link response frame to the link request source station, and the station receiving the link response frame changes the link response When the partner link address in the header of the frame is written to the communication table, link setting is completed, and then data is transmitted using this link, a write command is issued to the own link where the destination link is set. Simply, the station creates a ring transmission header by referring to the communication table, selects the transmission path to be used, sends the frame to be sent to the partner station using the selected transmission path, and sends it to the partner computer. Local area network having multiple transmission lines characterized by transmitting Data transfer method for network.