JPH0774765A - Hub equipment for csma/cd system - Google Patents

Abstract

PURPOSE:To obtain the hub equipment for the CSMA/CD access system utilizing effectively a transmission line band by preferentially sending a transmission signal of a node of a higher priority when a transmission line load is high in the LAN of the CSMA/CD access system. CONSTITUTION:In the hub equipment accommodating terminal equipments of CSMA/CD access system, a transmission line utilizing rate measurement circuit 9 always monitors a utilizing rate of a transmission line 30 and a transmission signal gate circuit 12 prevents relay of a transmission signal of a relevant terminal equipment to a LAN transmission line when a maximum transmission line utilizing rate set to each terminal equipment is exceeded. Simultaneously a collision signal generating circuit 10 reports occurrence of collision in a pseudo-way to stop transmission tentatively and to make re-transmission.

Description

Detailed Description of the Invention

[0001]

This invention relates to CSMA / CD (Ca
rlier Sense Multiple Acces
In a local area network (hereinafter referred to as LAN) of the s / Collision Detection access method, when the load of the transmission line is high, the packet transmission of the node with high priority is preferentially transmitted and the bandwidth of the transmission line is effectively used. The present invention relates to a LAN hub device for performing.

[0002]

2. Description of the Related Art A prior art communication system in the conventional CSMA / CD access system is disclosed in, for example, JP-A-59-204347.
As disclosed in Japanese Laid-Open Patent Publication No. 60-24747, the back-off time that determines the start of retransmission of each terminal when a collision occurs is changed according to the priority and urgency of transmission,
In this method, high-priority transmission is started with a short back-off time for general retransmission and is preferentially transmitted to a LAN transmission line.

Further, as disclosed in Japanese Patent Laid-Open No. 2-149041, in a privileged mode, a jam signal forcibly causing a collision on a transmission line is transmitted even when another node is using the transmission line. Then, a method of transmitting with the minimum back-off time is also proposed.

[0004]

As described above, in the conventional access method, the CSMA / CD access mechanism on the terminal side is provided with the function standardized by the international standard (IEEE, etc.) and the nonstandard remodeling procedure. Therefore, there is a problem that a commercially available CSMA / CD access controller LSI chip or the like cannot be used to improve the function.

In the conventional access method, the standard L
As a result of connecting a nonstandard device to the AN, there is a problem that confusion occurs.

An object of the present invention is to solve the conventional problem and to allow the terminal side to use the standard CSMA / CD access method as it is, which has a priority access control function.
It is to provide a D type hub device.

Another object of the present invention is to provide a hub device which makes it possible to efficiently use the LAN transmission line to the maximum extent.

[0008]

The present invention is a CSMA / C
In a hub device for concentrating and connecting a plurality of terminals to a D access type LAN transmission line, a transmission line utilization rate measuring means for measuring a utilization rate of the LAN transmission line, and a transmission line measured by the transmission line utilization rate measuring means. If the usage rate exceeds the maximum transmission path usage rate that allows access to the LAN transmission path preset for each subordinate terminal, prohibit the relay of the transmission signal of the corresponding terminal to the LAN transmission path. With
Means for sending a pseudo collision occurrence signal to the corresponding terminal to temporarily prohibit access to the LAN transmission path of the corresponding terminal.

[0009]

[Function] In recent years, CSMA / using a twisted cable
Hub equipment (LA
N concentrators) have been widely introduced. Such a hub device is provided between the LAN transmission line and the terminal.

According to the present invention, this hub device is provided with an LA on the backbone side.
The traffic state of the N transmission line is constantly monitored, and depending on the congestion of the transmission line, a pseudo collision state is generated for the transmission of the terminal to a terminal with a low priority, and the standard CSMA / CD access method is used. Transmission from terminals is temporarily suppressed according to the protocol, and the transmission path is opened to terminals with high priority.

[0011]

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

FIG. 1 shows an embodiment of the present invention. This hub device includes a plurality of (three in the figure) terminals 40-1, 40-2, 40- on the LAN 20 of the CSMA / CD access method.
Concentrate and connect 3. The terminal is a terminal that can use the standard CSMA / CD access method.

The hub device includes a circuit 50 common to each terminal,
It is provided with circuits 60-1, 60-2, 60-3 corresponding to each terminal. Since the configurations of the circuits 60-1, 60-2, and 60-3 are the same, only the configuration of the circuit 60-1 is shown.

First, the structure of the common circuit 50 will be described. The common circuit 50 includes the receiver circuits 4, 5 connected to the collision indication signal lines 1a and 1b, the reception signal lines 2a and 2b, and the transmission signal lines 3a and 3b from the transceiver circuit 30 connected to the LAN transmission line 20, respectively. Signal transmission transceiver circuit 6, collision detection circuit 7, and carrier detection circuit 8
And a transmission line utilization rate measuring circuit 9.

On the other hand, each circuit 60-1, 60-corresponding to the terminal
2, 60-3 each include a collision signal generation circuit 10, a transmission control circuit 11, a transmission signal gate circuit 12, and a media conversion circuit 13.

The receiver circuit 4 is connected to the collision detection circuit 7, the collision detection circuit 7 is connected to the collision signal generation circuit 10, and the collision signal generation circuit 10 is connected to the media conversion circuit 13.

The receiver circuit 5 is connected to a carrier detection circuit 8 and a media conversion circuit 13, the carrier detection circuit 8 is connected to a transmission line utilization rate measuring circuit 9, and the transmission line utilization rate measuring circuit 9 is connected to a transmission control circuit 11. The transmission control circuit 11 is connected to the media conversion circuit 13.

The transceiver circuit 6 is connected to the transmission signal gate circuit 12, and the transmission signal gate circuit 12 is connected to the media conversion circuit 13.

The transmission control circuit 11 includes a collision signal generation circuit 1
0 and the signal gate circuit for transmission 12 are connected.

The collision detection circuit 7 includes a transceiver circuit 30.
The presence / absence of signals from the collision display signal lines 1a and 1b is detected and the level is output.

The carrier detection circuit 8 monitors the reception signal lines 2a and 2b from the transceiver circuit 30, detects an effective carrier on the transmission line 20, and outputs the output to the transmission line utilization rate measurement circuit 9. .

The transmission line utilization rate measuring circuit 9 measures the transmission line utilization rate in order to open the transmission line to a terminal having a high priority,
The measurement result is output to the transmission control circuit 11.

The transmission control circuit 11 compares the transmission path usage rate measured by the transmission path usage rate measuring circuit 9 with the maximum transmission path usage rate permitted for LAN access set for each terminal, and measures the measured transmission path. When the usage rate exceeds the maximum transmission path usage rate, the transmission signal gate circuit 12 is controlled to suppress the transmission signal from the terminal so that it is not transmitted to the LAN side transmission path 20. When it is detected that the transmission operation from the terminal is started, the collision signal generation circuit 10 is instructed.

The collision signal generation circuit 10 includes a transmission control circuit 1
When the instruction from 1 is received, a pseudo collision state is displayed on each terminal, and each terminal is prompted to stop the transmission and to retransmit. In this case, the number of retransmissions is a predetermined number k (k <N), which is equal to or less than the maximum number of retransmissions, so that the terminal does not detect a transmission path failure exceeding the maximum number N of retransmissions specified by the CSMA / CD access protocol. To do.

The media conversion circuit 13 converts the signal interface into the interface of the cable medium of each terminal.

The operation of this embodiment will be described below.

Corresponding to the occurrence of a high load on the LAN transmission line 20, the collision display signal for collision monitoring from the transceiver circuit 30 of the LAN transmission line is the collision signal display lines 1a, 1
The signal is received by the receiver circuit 4 via b. The presence / absence of the received collision display signal is detected by the collision detection circuit 7, the level is output, and then sent to the collision signal generation circuit 10 and sent to the terminal through the media conversion circuit 13 of each terminal. The terminal stops transmission according to the standard CSMA / CD access method, and resumes transmission when the collision state is released.

The carrier detecting circuit 8 detects an effective carrier on the transmission line, and the output is input to the transmission line utilization rate measuring circuit 9 to measure the utilization rate of the transmission line. The result is input to the transmission control circuit 11, and when the maximum usage rate set for each terminal is exceeded, the transmission signal from the terminal port is suppressed using the transmission signal gate circuit 12, and the transmission path on the LAN side is controlled. When the transmission operation from the terminal is detected, the instruction is sent to the collision signal generation circuit 10 and the media conversion circuit 1 is transmitted to the terminal side.
A pseudo collision state is displayed via 3 and the terminal is prompted to stop the transmission and to retransmit. In this case, the transmission is stopped until the retransmission circuit continues k times.

[0029]

According to the present invention, the hub device responds to the priority of each terminal and the traffic state of the LAN, and when the traffic is high (when the load is high), the transmission of the terminal having the low priority is transmitted to the LAN.
It is possible to suppress the transmission to the transmission path, preferentially perform the high-priority terminal transmission, and to effectively use the LAN transmission path to the maximum.

In addition, since the hub device side deals with the realization thereof, the terminal side has an effect that the standard CSMA / CD access method can be used as it is.

[Brief description of drawings]

FIG. 1 is a block diagram of an embodiment of the present invention.

[Explanation of symbols]

 1a, 1b LAN side collision display line 2a, 2b LAN side reception signal line 3a, 3b LAN side transmission signal line 4,5 Receiver circuit 6 Transceiver circuit 7 Collision detection circuit 8 Carrier detection circuit 9 Transmission path utilization rate measurement circuit 10 Collision signal Generation circuit 11 Transmission control circuit 12 Transmission signal gate circuit 13 Media conversion circuit 20 LAN transmission line

Claims (2)

[Claims] 1. In a hub device for concentrating and connecting a plurality of terminals to a LAN transmission line of the CSMA / CD access system, a transmission line utilization rate measuring means for measuring the utilization rate of the LAN transmission line, and this transmission line utilization rate measurement. If the transmission path usage rate measured by the means exceeds the maximum transmission path usage rate that permits access to the LAN transmission path set in advance for each subordinate terminal, LAN transmission of the transmission signal of the corresponding terminal And a means for prohibiting relay to the route, sending a pseudo collision occurrence signal to the relevant terminal, and temporarily inhibiting access to the LAN transmission line of the relevant terminal. Hub device of CSMA / CD system characterized by. 2. The CSMA according to claim 1, wherein the access prohibition period is within a time period corresponding to a predetermined maximum number of retransmissions defined by the CSMA / CD access protocol in the corresponding terminal. / CD hub device.