JPH04259140A - Collision avoidance csma/cd type local area network - Google Patents

Abstract

PURPOSE:To implement data transmission control in response to the degree of collision without stopping data transmission in all network definitely when data collision takes place in the CSMA/CD type local area network. CONSTITUTION:When, for example, a line concentrator 2 receives a data from a MAU 4 while receiving a data from a host line concentrator 1, the line concentrator 2 sends the data from the host line concentrator 1 to connected MAUs 4, 5. Moreover, when the line concentrator 2 receives a data from the MAU 5 while receiving a data from the MAU 4, the line concentrator 2 sends the first-come data to all MAUs and the host line concentrator 1. Furthermore, when the MAU 4 receives data simultaneously from the line concentrator 2 and the terminal equipment 8 and the data from the line concentrator 2 is not a jam signal, the line concentrator 2 sends a data reception command signal to the terminal equipment 8. Moreover, when the terminal equipment 8 receives the data reception command signal from the MAU 4 while sending a data, the terminal equipment 8 stops data transmission and receives the data.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention relates to CSMA/CD (Ca
rrier Sense Multiple Acce
ss with Collision Detection
n) type local area network, particularly for star type CSMA/CD type local area networks (LAN; Local Area Network).
The present invention relates to a collision avoidance method in a network.

0002

[Prior Art] A local area network is a system that connects computers and other terminals with optical fibers or electric cables within a relatively limited area, such as a single building or a university campus, and allows data to be sent and received between the terminals. It also realizes functions such as sharing of output devices and storage devices.

[0003] A star-type LAN is one of the means for constructing a LAN, in which multiple terminals are connected to a line concentrator via a medium access unit (hereinafter referred to as MAU), and these line concentrators are arranged in a tree shape. They are connected to form a hierarchical structure.

[0004] CSMA/CD is one of the LAN access methods. Star type CSMA/CD type LAN
Currently, IEEE (Institute of Electrical and Electronics Engineers)
Institute of Electrical and
Standardization is underway at the Electronic Engineers. There is 10BASE-T. 10BASE-T has a transmission speed of 10 Mbit/s,
CSMA/CD is used as the access method, and collision detection is performed by a line concentrator. Regarding the operating principle of the CSMA/CD system, please refer to Ohmsha's "Heterogeneous Connection and LAN Picture Book", p. 11.

[0005] A terminal that intends to transmit data checks whether data is being transmitted from another terminal on the transmission path. After confirming that no data is being transmitted from another device, send your own data. Since all terminals share the transmission path, if two or more terminals start transmitting almost simultaneously, their data will collide on the transmission path and the data will be destroyed. The transmitting terminal monitors the transmission path even while transmitting, and if a collision occurs, it stops transmitting data, sends a collision reinforcement signal (jam signal), and waits for a certain period of time before retransmitting. The jam signal is used to notify all terminals on the network that a data collision has occurred on the transmission path, and to prevent them from transmitting data.

FIG. 6 shows an example of a conventional 10BASE-T configuration. The operation of 10BASE-T will be explained using FIG. 6. Regarding each component of 10BASE-T and its operation, for example, Ohmsha "Computer & Network LAN" September 1990 issue, Vol. 9, No. 9,
pp. 25-31. 1, 24, and 25 are line concentrators having a plurality of input/output terminals (hereinafter referred to as ports). The line concentrator has the function of outputting a signal coming in from one of the ports to the other port. MAUs 26 to 29 connect terminals 30 to 33 to the line concentrator. 12 is a transmission cable that connects the line concentrators, 13 is a transmission cable that connects the line concentrator and MAU, and 14 is an interface cable that connects the MAU and the terminal.

The transmission cable 12 has a TD line 12a for transmitting data from a line concentrator to the other line concentrator, and an RD line 12b for receiving data from the other line concentrator. Similarly, the transmission cable 13 includes a TD line 13a that transmits data from the MAU to the line concentrator, and an RD line 13b that transmits data from the line concentrator to the MAU. The interface cable 14 includes a cable from the terminal to the MA
DO line 14a transmits data to U, DI line 14b transmits data from MAU to terminal, CI transmits collision detection signal (hereinafter referred to as SQE signal) from MAU to terminal.
There is a line 14c. Below, using FIG. 6, the conventional 10
The operation of BASE-T will be explained.

[0008] Now, consider a case where the terminal 30 sends data. Terminal 30 transmits data on DO line 14a of interface cable 14. The MAU 26 sends this data to the TD line 13a of the transmission cable 13, and also sends this data to the DI line 1 of the interface cable 14.
4b, the data is looped back to the terminal 30. The line concentrator 24 that received the data on the TD line 13a sends the MAU
27 and the line concentrator 1. MAU2
7, data is sent on the RD line 13b of the transmission cable 13, and the MAU 27 sends this data to the terminal 31 on the DI line 14a of the interface cable 14. Furthermore, the data sent to the higher-level line concentrator 1 is sent to the line concentrator 25, and from there MAU28 and MAU29
and is sent to terminal 32 and terminal 33.

[0009] In 10BASE-T, all terminals share the transmission path between line concentrators, so two or more terminals may start transmitting almost at the same time, and the transmitted data may conflict with the line concentrator. . This is called a collision. Now, assume that the terminal 30 and the terminal 31 start transmitting data almost simultaneously, and a data collision occurs in the line concentrator 24. At this time, the line concentrator 24 that detected the collision is the MAU26, MAU27
, transmits a jam signal for collision reinforcement to the line concentrator 1. The purpose of sending a jam signal is to notify all terminals on the network that normal transmission and reception is no longer possible due to a data collision on the transmission path, and to prevent them from transmitting data. .

[0010] MAU 26 and MAU 27 detect a collision from the simultaneous presence of data on DO line 14a of each interface cable 14 and RD line 13b of transmission cable 13, and transmit data on CI line 14c of each interface cable 14. CSO for a certain period of time
A signal (a bit string of "01") is transmitted to notify each of the terminals 30 and 31 that a collision has occurred. In response to this, the terminals 30 and 31 stop transmitting data and transmit jam signals for collision reinforcement. and,
After waiting for a certain period of time, the data is retransmitted.

[0011]

[Problem to be Solved by the Invention] As mentioned above, 10B
ASE-T has a problem in that if a collision occurs, all transmitting terminals must stop transmitting. That is, for example, in the configuration example shown in FIG. 6, data from the terminal 30 and data from the terminal 33 are
5, both terminals had to stop transmitting even though terminal 30 was transmitting a larger amount of data than terminal 33.

[0012] Furthermore, since the collision reinforcement jam signal is transmitted, there is a problem in that the entire network cannot perform normal communication. That is, for example, in the configuration example shown in FIG. 6, even if data from the terminal 30 and data from the terminal 31 collide in the line concentrator 24, a jam signal is sent to the entire network, so that the terminal 30 that was transmitting the data Since not only the terminal 31 but also the terminals 32 and 33 were unable to transmit, there was a problem that the transmission path could not be used effectively.

[0013] The present invention is intended to improve the above-mentioned problems, and aims to provide a network that prevents all network communications from being univocally stopped due to the occurrence of a collision, and that reduces performance deterioration due to collisions. do.

[0014]

[Means for solving the problem] Collision avoidance C according to the present invention
In an SMA/CD type local area network, a plurality of terminals are each connected to a plurality of line concentrators via a medium access device, and the plurality of line concentrators are connected to each other to form a tree-like hierarchical structure. In a CSMA/CD type local area network where data from a terminal is transmitted to all terminals via the multiple tree-structured concentrators, data is received from two or more input/output terminals. When data is received, there is a concentrator that has the function of transmitting the first received data to the input/output terminal, and the concentrator is connected to the concentrator with a transmission cable, and while the data from the terminal is being sent to the concentrator, the data from the concentrator is A medium access device that has the function of instructing a terminal to receive data when receiving data, and a medium access device that is connected to the medium access device with an interface cable, and if there is a reception instruction from the medium access device while data is being transmitted, It is equipped with a terminal that has the function of canceling transmission and receiving data.

[0015]

[Operation] In the present invention, when a line concentrator that does not have a lower level line concentrator and only terminals are connected receives data from a terminal while receiving data from an upper level line concentrator, Transmits data from the upper line concentrator to all connected terminals. Also, when receiving data from one of the terminals connected to the concentrator,
When data is received from another terminal, the first-arrived data is transmitted to all connected terminals and the upper line concentrator.

[0016] Also, the M connecting the line concentrator and the terminal
If the AU receives data from the line concentrator while transmitting data from the terminal to the line concentrator, and the data from the line concentrator is not a jam signal, it sends a signal instructing the terminal to receive the data. Also, the terminal may use MAU while transmitting data.
When a signal instructing to receive data is received from , transmission is stopped and data is received.

[0017]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is an overall configuration diagram of an embodiment of a star local area network according to the present invention. Figure 1
6, the same reference numerals as in FIG. 6 indicate the same or corresponding parts. The line concentrators 2 and 3 are line concentrators according to the invention. 4 to 7 are MAUs according to the present invention, and 8 to 11 are terminals according to the present invention.

FIG. 2 is an internal configuration diagram of the line concentrator according to this embodiment. In Figure 2, MAU2b is the conventional MAU2
6, 27, 28, 29, and there is one MAU for each input/output port. Repeater unit 2a is MAU2b
When any MAU is receiving data, it sends the data to other MAUs. Also, multiple MAU2b at the same time
When receiving data, determines whether to give priority to first-arriving data to avoid data collisions.

[0019] Priority processing means selecting only one data from multiple MAU2b and transmitting it to other MAU2b.
The data from the MAU2b that was not selected is discarded. When a plurality of MAUs 2b simultaneously receive data and priority processing is not performed, collision processing is performed. In the collision process, a jam signal is sent to all MAUs 2b in order to notify all terminals that a collision has occurred.

FIG. 3 shows the internal configuration of the MAU according to this embodiment. In FIG. 3, a simultaneous transmission/reception detector 8a monitors the DO line 14a and the RD line 13b to detect whether data is present at the same time. The jam signal detector 8b detects whether the data sent through the RD line 13b is a jam signal.

The route controller 8c includes a simultaneous transmission/reception detector 8a.
Based on the notification from the DI line selector 8f, which data from the DO line 14a or the RD line 13b should be sent to the DI line 14b. Also, based on the notifications from the simultaneous transmission/reception detector 8a and the jam signal detector 8b,
An instruction is issued to the control signal generator 8g to notify the terminal of detection of a collision or execution of priority processing. At this time, the buffer 2 (8e) is installed or removed from the RD line 13b as necessary.

FIG. 4 shows an operation flowchart of the line concentrator according to this embodiment. In addition, FIG. 5 shows an MAU according to the present invention.
The operation flowchart is shown below. The notation method of the flowchart will be explained using FIG. In FIG. 8, 34 is a block indicating an operation, 34a is the name of the block, and 34
b shows the actual operation. 35 is a line representing a transition between operation blocks. The condition 36 that causes the transition is attached next to 35.

In FIG. 5, DO, DI, CI, RD,
TD is DO line 14a and DI line 14b, respectively.
, CI line 14c, RD line 13b, TD line 1
3a represents. Also, ON indicates that there is some data,
OFF indicates that there is no data. Therefore, for example, the notation DO=ON indicates that some data is being received on the DO line 14a. Furthermore, the notation TD=DO indicates that data on the DO line 14a is transmitted to the TD line 13a. In the figure, JAM is the jam signal,
PRIOR each represents a priority processing notification signal.

Using FIGS. 1 to 5, ■ When there is no simultaneous arrival data, ■ When data from the upper line concentrator and data from the terminal arrive at the same time, and the data from the upper line concentrator is earlier, ■ The following describes the operations when data from the upper line concentrator and data from a terminal arrive at the same time, and the data from the terminal is earlier; (2) When data from two terminals arrive at the same time.

[0025] ■If there is no simultaneous arrival data, now the terminal 8
Suppose that you are trying to send data. First, terminal 8
sends data to DO line 14a of interface cable 14. MAU4 RDs buffer 2 (8d)
19, which has been disconnected from the line 13b and is waiting for reception. R
Since data is not being received on the D line 13b but data is being received on the DO line 14a, output processing 20 is executed. In the output process, the data on the DO line 14a is
It is transmitted to the D line 13a and DI line 14b.

The line concentrator 2 is initially in a standby state 15. It is detected that the MAU 2b to which the terminal 8 is connected has received data, and the process moves to relay processing 16. In relay processing 16, the received data is output to all ports other than the receiving port.

The data sent to the upper line concentrator 1 is sent to the line concentrator 3 through the normal line concentrator processing described in the conventional example. The line concentrator 3 transmits this data to MAU6 and MAU7. The MAU 6 disconnects the buffer 2 (8e) from the RD line 13b and waits for reception 19. Then, it is determined that there is data on the RD line 13b, and input processing 21 is performed. In the input process, data on the RD line 13b is output to the DI line 14b. This output continues until data is no longer received on the RD line 13b, and then returns to the reception wait 19. Similar processing is performed in MAU7.

■If data from the upper line concentrator and data from the terminal arrive at the same time, and the data from the upper line concentrator is earlier, in this case, data from the upper line concentrator 1 is sent to line concentrator 3. An example will be explained in which data from the terminal 11 arrives first and arrives at the line concentrator 3 immediately after that.

Inside the line concentrator 3, received data from the upper line concentrator 1 is detected, and the process shifts from the standby state to relay processing. Thereafter, data from the terminal 11 is received, and an SQE signal notifying a collision is sent from the MAU connected to the terminal 11 to the repeater unit 2a. The repeater unit 2a then moves to priority processing 17. In priority processing,
Send first-arrival data to other MAUs. That is, in the present case, data from the upper line concentrator 1 is transmitted to other MAUs. After this, when data is no longer received from the higher level line concentrator 1, the transmission ends.

The operation of MAU7 at this time is as follows. The MAU that was in the reception waiting state receives data from the terminal 11 and moves to output processing 20. In output processing, the data on the DO line 14a is transferred to the TD line 13a and DI.
to line 14b. In output processing, DO line 1
4a is transmitted to the TD line 13a and the DI line 14b. During this transmission, priority processing is performed in the concentrator 3, data from the terminal 11 is discarded, and data from the upper concentrator 1 is sent to the MAU 7. Therefore, MAU
7 receives data on RD line 13b, and RD line 1
It is determined that the data 3b is not a jam signal, and the process moves to priority processing 23. In priority processing 23, buffer 2 (8e) is incorporated into RD line 13b. As a result, the data on the RD line 13b is delayed by a certain amount of time.

[0031] This transmits a signal notifying priority processing to terminal 1.
RD line 1 until 1 is ready to receive and receive data.
This is to delay sending the data of 3b to the terminal 11. Then, a signal notifying priority processing is sent to the terminal 11 via the CI line 14c. The signal notifying priority processing is any signal different from the signal notifying collision. Then, the data on the RD line 13b is output to the DI line 14b. The output continues until data is no longer received on the RD line 13b, and the process returns to the reception wait 19.

At this time, the terminal 11 connects M on the CI line 14c.
The user learns from the signal sent from the AU6 that priority processing is being performed. Therefore, it stops transmitting its own data to the DO line 14a, and at the same time processes the data on the DI line 14b as normal received data. Then, after waiting for a certain period of time, the data is retransmitted.

■If data from the upper line concentrator and data from the terminal arrive at the same time, and the data from the terminal is earlier, in this example, data from terminal 11 arrives first at line concentrator 3, An example will be explained in which data from the higher-level line concentrator 1 arrives at the line concentrator 3 immediately after that.

Inside the line concentrator 3, data received from the terminal 11 is detected, and the standby state is shifted to relay processing. After that, S receives data from the upper line concentrator 1 and notifies the collision from the MAU 2b connected to the upper line concentrator 1.
A QE signal is sent to repeater unit 2a. The repeater unit 2a then moves to collision processing 18. In collision processing, a jam signal is transmitted 18 to all MAUs connected to the repeater unit 2a. Thereafter, when no SQE signal is received from any MAU connected to the repeater unit 2a, the collision process ends.

The operation of MAU7 at this time is as follows. The MAU that was in the reception waiting state receives data from the terminal 11 and moves to output processing 20. In output processing, the data on the DO line 14a is transferred to the TD line 13a and DI.
to line 14b. During this transmission, collision processing is performed in the concentrator 3, and a sham signal is also sent to the MAU 7 via the RD line 13b.

Therefore, the MAU receives the data on the RD line 13b, determines that the data on the RD line 13b is a jam signal, and moves to collision processing 22. In the collision processing 22, an SQ is sent to notify that a collision has occurred on the CI line 14c.
Send the E signal to the terminal 11. The SQE signal used to notify a collision is the same as before. It also outputs the data on the RD line 13b, that is, the jam signal, to the DI line 14b. Then, the data on the DO line 14a is output to the TD line 13a.

After this, if no data is received on the DO line 14a, the process returns to input processing 21. If there is received data on the DO line 14a and no data is received on the RD line 13b, the process returns to the output process 20. At this time, the terminal 11 learns that a collision has occurred from the SQE signal sent from the MAU 6 on the CI line 14c. Therefore,
In order to stop sending its own data to the DO line 14a and strengthen the collision, it transmits a jam signal for a certain period of time, and after waiting for a certain period of time, retransmits the data.

■When data from terminals arrive at the same time, an example of this case is when data from terminal 10 arrives at line concentrator 3 first, and data from terminal 11 arrives at line concentrator 3 immediately after that. Let's explain using an example. Inside the line concentrator 3, data from the terminal 10 is detected and the standby state is shifted to relay processing. Thereafter, data from the terminal 11 is received, and an SQE signal notifying a collision is sent from the MAU 2b connected to the terminal 11 to the repeater unit 2a. The repeater unit 2a then moves to priority processing 17. In priority processing, data that arrives first is sent to other MAUs. That is, in this case, data from the terminal 10 is transmitted to another MAU 2b. After this, when no data is received from the terminal 10, the transmission ends.

The operation of the MAU 2b at this time is as follows. The MAU that was in the reception waiting state receives data from the terminal 11 and moves to output processing 20. In output processing, the data on the DO line 14a is transferred to the TD line 13a and D
It is transmitted to I line 14b. During this transmission, the line concentrator 3
Then, priority processing is performed, data from terminal 11 is discarded, and data from terminal 10 is sent to MAU 7. Therefore, the MAU receives data on the RD line 13b and
It is determined that the data on line 13b is not a jam signal,
The process moves to priority processing 23. In priority processing, Huffer 2 (8e
) is incorporated into the RD line 13b.

[0040] As a result, the data on the RD line 13b is delayed by a certain amount of time. This is to delay sending the data on the RD line 13b to the terminal 11 until the terminal 11 receives a signal notifying priority processing and prepares to receive data. Then, a signal notifying priority processing is sent to the terminal 11 via the CI line 14c. The signal notifying priority processing is any signal different from the signal notifying collision. Then, RD line 13 to DI line 14b
Output the data of b. The output continues until data is no longer received on the RD line 13b, and the process returns to the reception wait 19.

[0041] At this time, the terminal 11 connects M on the CI line 14c.
It is learned from the signal sent from AU6 that priority processing was being performed. Therefore, it stops transmitting its own data to the DO line 14a, and at the same time processes the data on the DI line 14b as normal received data. Then, after waiting for a certain period of time, the data is retransmitted.

In this embodiment, there are three line concentrators and the line concentrator hierarchy is two levels, but as shown in FIG. 7, the number of line concentrators may be increased to increase the number of levels. In Figure 7,
The line concentrator 1 is a conventional line concentrator, and the line concentrator 2 is a line concentrator according to the present invention. In addition, 4 relates to the present invention,
8 is a terminal according to the present invention.

[0043]

Effects of the Invention According to the present invention described above, when receiving data is received from two or more ports, a line concentrator having a function of transmitting the first received data to the port, and a line concentrator that concentrates the data from the terminal. MAU has the function of instructing the terminal to receive data when data is received from the concentrator while transmitting data to the device, and MAU has the function of instructing the terminal to receive data while transmitting data. By providing a terminal with the function of receiving data, it is possible to effectively utilize the transmission path of the local area network.

[Brief explanation of the drawing]

FIG. 1 is an overall configuration diagram of an embodiment of a star local area network according to the present invention.

FIG. 2 is an internal configuration diagram of a line concentrator according to the present invention.

FIG. 3 is an internal configuration of the MAU according to the present invention.

FIG. 4 is a processing flowchart of the line concentrator according to the present invention.

FIG. 5 is a flowchart of MAU processing according to the present invention.

FIG. 6 is an overall configuration diagram of an embodiment of a conventional star local area network.

FIG. 7 is a diagram showing an example of the configuration of a star local area network according to the present invention.

FIG. 8 is a diagram showing a notation method of a flowchart.

[Explanation of symbols]

1. Line concentrator 2. Line concentrator 3. Line concentrator 4 Media access device 5 Medium access device 6 Medium access device 7 Medium access device 8 Terminal 9 Terminal 10 Terminal 11 Terminal 12 Transmission cable 13 Transmission cable 14 Interface cable

Claims (1)

[Claims] Claim 1: A plurality of terminals are each connected to a plurality of line concentrators via a medium access device, and the plurality of line concentrators are connected to each other to form a tree-like hierarchical structure, and data from one terminal is CSMA/C is transmitted to all terminals via the plurality of tree-structured line concentrators.
In a D-type local area network, a line concentrator that has multiple input/output terminals and has a function of transmitting the first received data to the input/output terminal when receiving data from two or more input/output terminals, and a line concentrator A medium access device that is connected to the device by a transmission cable and has the function of instructing the terminal to receive data when data is received from the concentrator while transmitting data from the terminal to the concentrator, and an interface to the medium access device. - Collision avoidance CSMA/CD characterized by being connected by a cable and equipped with a terminal that has the function of canceling transmission and receiving data if there is a reception instruction from the medium access device during data transmission. type local area network.