JPH0522331A - Multi-port repeater and communication control system - Google Patents

Abstract

PURPOSE:To realize the high speed and highly reliable data exchange system. CONSTITUTION:When a transmission request takes place in plural stations 111-114, a transmission enable request frame including identification information of its own station is sent respectively from the stations 111-114. When a multi- port repeater 101 is already in the relay operation, the transmission of a transmission enable frame is extended. As soon as the relay of the current data frame is finished, the transmission enable frame is sent to one of the stations 111-114 to which the transmission of the transmission enable frame is extended. A station among the stations 111-114 receiving the transmission enable request frame from the repeater 101 sends a data frame.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a multiport relay device which is a constituent device of a star type network, and a communication control system using the same.

[0002]

2. Description of the Related Art IE is a standard for star networks.
EE 802.3 10BASE-T is widely known. The multiport relay device defined in this standard has the following features.

(1) When a data frame arrives at an arbitrary input port, if there is no other data frame being relayed, the data frame that arrives immediately is relayed.

(2) When there is a data frame currently being relayed when a data frame arrives at an arbitrary input port, both the currently relaying frame and the arriving frame fail. In this case, the relay of the current data frame is stopped, and a signal called "jam" is transmitted to all output ports in order to notify the relay failure.
Such a situation is referred to as "collision (of transmission frame)".

The communication control system defined in this standard has the following features.

(1) When a transmission request is generated at an arbitrary station, that station performs a protocol process for data transmission, constructs a data frame, and then detects an output port of a relay device for a certain period of time. When the output port is empty over the above, the data frame is transmitted. If the output port is not empty, the output port becomes empty, and the data frame is transmitted after waiting for a certain interval or more to remain empty.

(2) When the output is detected at the output port of the relay device during the transmission of the data frame, it is considered that the data frame collides with another data frame during the relay, and the jam is transmitted to the input port. .

(3) When transmission of a data frame fails, each station attempts retransmission after a predetermined time has elapsed.

[0009]

However, the star type network based on the IEEE802.3 10BASE-T standard having the above characteristics has the following problems.

(1) Increasing Arrival Delay Due to Collision When there is a collision of transmission frames, the transmission of both the frame currently being relayed and the frame arriving later fails. Therefore, when the transmission throughput increases and the collision of the transmission frames increases, the arrival delay extremely increases.

(2) Lack of priority control mechanism When two or more data frames are transmitted to the relay device at the same time, both data transmissions fail. Therefore, it is based on the importance or urgency of the transmission data. Relay control cannot be performed.

(3) Complex communication control It is necessary for each station to implement complex communication control such as collision detection, jam transmission, and retransmission.

(4) Transmission delay Since the output port needs to be detected over a certain interval after the protocol processing for data transmission is performed and the preparation for the transmission of the data frame is completed, the transmission path can be used immediately. Even in this case, the data transmission is delayed.

An object of the present invention is to provide a multi-port relay device and a communication control system for a star type network that can solve the above problems.

[0015]

In order to achieve the above object, the multi-port relay apparatus of the present invention, when a transmission permission request frame arrives at an arbitrary input port, when there is no data frame being relayed, Immediately suspends the transmission permission frame to the transmission permission requesting station and delays transmission of the transmission permission frame if there is a frame already being relayed, and permits transmission as soon as the relay of the data frame currently being relayed is completed. According to the priority of the transmission permission request frame from the requesting station, means for transmitting the transmission permission frame to these stations one by one is provided.

Further, according to the communication control method of the present invention, prior to the transmission of the data frame, the multiport relay apparatus transmits the transmission permission request frame including the identification information of its own station, and in response thereto, The data frame is transmitted after waiting for the arrival of the transmission permission frame returned from the multiport relay device.

[0017]

When a transmission permission request frame arrives at a multiport relay device from a plurality of stations, if the relay device is already relaying, the transmission of the transmission permission frame is postponed and the relay of the current data frame is continued. To do. After that, as soon as the current relay ends, transmission permission frames are transmitted to the transmission permission requesting stations one by one. The transmission permission requesting station transmits the data frame when the transmission permission frame is received from the relay device.

As described above, even if the transmission permission request frame arrives at the relaying multiport relay device, the issuance of the transmission permission to the transmission permission requesting station is postponed, and the data frame currently being relayed is relayed without any trouble. To be done. Therefore, the collision of the transmission frames is eliminated, and the increase of the arrival delay can be avoided. Moreover, by eliminating the collision of the transmission frames, it is possible to reduce the communication control procedure for handling the collision, and it is possible to greatly simplify the communication control.

When a plurality of stations request transmission at substantially the same time, the relay device issues one transmission permission to each station in accordance with the priority of the transmission permission request frame from these stations. The transmission order can be controlled, and priority control of data transmission can be realized.

Furthermore, each station transmits a transmission permission request frame prior to the preparation for data frame transmission, so that data transmission preparation can be performed between the transmission of the transmission permission request frame and the reception of the transmission permission frame. ,
Data can be transmitted immediately after the preparation for transmission is completed.

[0021]

Embodiments of the present invention will be described below with reference to the accompanying drawings.

FIG. 1 shows a basic configuration example of a system in which the present invention is used. This system includes a central multi-port relay device 101 and a plurality of stations 111, 112, 11
Bidirectional links 121, 122, which connect with 3, 114
123 and 124, which serve to exchange data between these stations. The signals exchanged between the stations 111 to 114 may be analog data, digital bit string data, or digital octet string data. The bidirectional links 121 to 124 may be pairs of twisted wires, coaxial cables, wiring on a board, circuits for exchanging electrical signals such as circuits, or wireless links, waveguides, optical waveguides, optical fibers. In addition, it may be one that exchanges signals by electromagnetic waves. Here, an optical fiber is used as a medium, and a system for exchanging digital bit string data will be described.

FIG. 2 shows an example of the data transmission process of each station 111-114.

Prior to transmitting a data frame, each station 111-114 first transmits a transmission permission request frame including its own identification information and transmission priority information. The format of this transmission permission request frame is fixed, and the relay device 101 can transmit other frames even while relaying. Therefore, the process of transmitting the transmission permission request frame is relatively simple and can be performed by dedicated hardware such as a communication control LSI. In this case, in the data transmission process, it is only necessary to issue the transmission request of the transmission permission request frame (202 in the figure), which can reduce the load of the data transmission process. After the transmission request for the transmission permission request frame is issued in this way, a protocol process for data transmission and a process for assembling the data frame are performed (203 in the figure). When these processes are completed and the data frame is ready for transmission,
Check if the transmission permission frame for the previously transmitted transmission permission request frame has arrived (204 in the figure)
. If the transmission permission frame has already arrived, the data frame is immediately transmitted (205 in the figure). If the transmission permission frame has not arrived, the transmission is postponed.

3 and 4 show examples of the relay control process of the multiport relay apparatus 101.

FIG. 3 shows a transmission permission acceptance process in the relay device 101. When a transmission permission request frame is received by an arbitrary input port (302 in the figure), it is determined whether the transmission permission has been issued (303 in the figure). If the transmission permission is not issued, the transmission permission completion is set to Yes, and the transmission permission frame is transmitted from the output port corresponding to the station identification information in the transmission permission request frame to the transmission permission requesting station (30 in the figure).
5). If the transmission permission has already been issued when the transmission permission request frame is received (when the transmission permission completion is Yes), the transmission permission request is permitted based on the priority (priority information in the transmission permission request frame). Register in the queue (30 in the figure)
4).

FIG. 4 shows a data frame relay process in the relay device 101. When a data frame arrives at any input port after issuing the transmission permission (40 in the figure)
3), relaying the data frame (40 in the figure)
4). Then, when this relay is completed, it is determined whether or not there is another transmission permission waiting by looking at the queue (405 in the figure). As a result, if there is a transmission permission wait, the transmission permission frame is transmitted to the transmission permission request station at the head of the queue (407 in the figure), the transmission permission request is canceled, and then the data frame to be relayed arrives. Wait
(403 in the figure). The above procedure is repeated to cause each transmission permission requesting station to sequentially output data frames, and these data frames are relayed one by one. Then, when there is no transmission permission request in the queue, the transmission permission completion is set to NO and it is judged whether or not the transmission permission is completed (402 in the figure).

In this way, the present multiport relay apparatus 101
Then, when the transmission permission request frame arrives when not relaying, it issues a transmission permission to the transmission permission requesting station, and when it is already relaying, it registers the transmission permission request in a queue (FIG. 3). And a relay means for relaying a data frame when it arrives at an arbitrary input port (4 in FIG. 4).
02-404) and means for issuing a transmission permission according to the order of the queue after relaying the data frame (405-405 in the figure).
407). Therefore, even if the transmission permission request frame arrives from the other station to the multi-port relay device 101 that is already relaying, the relaying of the data frame being relayed is continued, and the collision of the transmission frames can be eliminated. Therefore, even if the transmission throughput increases, a high-speed system can be realized without increasing the data arrival delay. Moreover, since the collision of the transmission frames is eliminated, the communication control procedure related to the collision can be reduced and the reliability of the system can be improved. For comparison, FIG. 5 shows a flow chart of a frame transmission process defined by IEEE 802.3 10BASE-T described in the prior art. By comparing FIG. 2 with FIG. 5, in this frame transmission process, collision detection during frame transmission in IEEE 802.3 10BASE-T, jam transmission at the time of collision detection, retransmission, etc. are not required at all, and communication control is greatly performed. You can see that it has been simplified.

Since each station 111 to 114 transmits the transmission permission request frame prior to the preparation of the data frame transmission, the data transmission preparation is performed from the transmission of the transmission permission request frame to the reception of the transmission permission frame. It can be performed. In particular, if the system is configured so that the processing time for preparing the transmission of the data frame and the time from the transmission of the transmission permission request frame to the return of the transmission permission frame have the same value as much as possible, the transmission permission frame The preparation for transmission can be completed almost at the same time as the reception, and the data can be transmitted immediately after the reception of the transmission permission frame. Therefore, the data transmission delay can be dramatically reduced, and the relay device 101 and the transmission paths 121 to 124 can be used more efficiently.

In the multiport relay apparatus 101 of the above embodiment, transmission priority information is included in the transmission permission request frames from the stations 111 to 114, and the transmission permission frames are sent to the stations 111 to 114 according to this priority. I sent it,
The order of transmission of these stations may be controlled simply according to the arrival order of the transmission permission request frames.

[0031]

As described above, by using the multi-port relay device and the communication control system of the present invention, the data arrival delay and the transmission delay can be reduced by a simple communication control procedure, and high-speed and highly reliable data can be obtained. A switching system can be realized.

[Brief description of drawings]

FIG. 1 is a system configuration diagram of a star network in which the present invention is used.

FIG. 2 is a flowchart showing an example of a communication control process performed by each station that transmits data in the present invention.

FIG. 3 is a flowchart showing an example of a transmission permission acceptance process of the multiport relay apparatus of the present invention.

FIG. 4 is a flowchart showing an example of a data frame relay process of the multi-port relay device of the present invention.

FIG. 5 is a flow chart of a frame transmission process defined in IEEE 802.3.

[Explanation of symbols]

101 Multi-port relay device 111-114 stations 121-124 bidirectional link

Claims (2)

[Claims] 1. When a transmission permission request frame arrives at an arbitrary input port and has no data frame being relayed, the input port has a plurality of input ports and an output port paired with the input port. Means to immediately send a transmission permission frame to the transmission permission requesting station, and if there is a frame that is already being relayed, delays transmission of the transmission permission frame and transmits it as soon as the relay of the data frame currently being relayed is completed. A multiport relay apparatus comprising: a means for transmitting transmission permission frames to these stations one by one according to the priority of the transmission permission request frames from the permission requesting stations. 2. Each station transmits a transmission permission request frame including identification information of its own station to the multiport relay device according to claim 1 before transmitting the data frame, and the multiport relay apparatus transmits the transmission permission request frame. A communication control method characterized in that a data frame is transmitted after waiting for the arrival of a transmission permission frame returned from a port relay device.