JPS6395750A - Data transmission control system - Google Patents

Abstract

PURPOSE:To effectively use a transmission line by applying CSMA/CD system transmission control in case of small quantity data and allowing a transmission/ reception station of lots of data to set and change the control system from the CSMA/CD system to the token system in sending lots of data. CONSTITUTION:Normally, nodes stations 1-3 use the transmission line impartially by the CSMA/CD system (Carrier Sense Mulitple Access with Collision Detection) system. When a node station desires to send lots of data, the station requests the setting change of the CSMA/CD system to the token system for the line to all node stations. Then all node stations connected to the transmission line 5 use the line 5 as the token system. In using the line 5 by the token system, since the transmission right is given to all the node stations in order, the node station sending lots of data and the node station sending a small amount of data use impartially the line 5. Since the collision by the acquisition of the transmission right of the line 5 is eliminated, the line 5 is used effectively.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a data transmission control system, and particularly to a data transmission control system suitable for performing data transmission between a plurality of node stations using the C3MA/CD system. .

[Conventional technology]

Conventionally, CSMA/CD (Carrier Sen.
se Multiple Access wjth C
There are two methods: o11ision Detection) method and token method.

In the CS MA/CD system, all node stations connected to a transmission path have equal transmission rights. A node station that wants to send data checks whether another node station is using the transmission line, and if the transmission line is free, it sends the data, and if it is not free, it waits until it becomes free. Therefore, C
In the case of the SMA/CD system, collision occurs when multiple node stations send data at the same time. When a collision is detected, each node must wait an appropriate amount of time before retransmitting data.

On the other hand, in the token system, when no node is transmitting data, a special bit pattern called a token circulates on the transmission path. A node station that wants to send data captures the token and replaces the bit pattern with a connector pattern to obtain the right to transmit. When data transmission is completed, the node station restores the original bit pattern to the original bit pattern and releases the right to transmit. Therefore, in the case of the token system, if one node captures the token, no collision occurs because other nodes cannot send data until the token is recovered.

Regarding the CSMA/CD method and token method,
Nikkei Data Pro/FDP (Nikkei McGraw-Hill 19
(February 1985), it was discussed as ``Current Status of Local Networks''.

[Problem that the invention seeks to solve]

The CS MA/CD method can perform data transmission immediately without collision with other node stations when the utilization rate of the transmission path is low. However, when the utilization rate of a transmission path increases due to a large amount of data transmission by a certain node station, collisions increase due to competition for transmission rights on the transmission path between node stations. It becomes impossible to transmit small amounts of data, and the transmission path cannot be used effectively. On the other hand, in the token method, csMA
Unlike the /CD system, collisions do not occur, but once a node obtains the right to transmit, other nodes cannot transmit data until the token is restored.

An object of the present invention is to provide a data transmission control method that effectively uses transmission paths when transmitting large amounts of data, assuming data transmission using the CSMA/CD method in which transmission rights are equal among all node stations. It's about doing.

[Means for solving problems]

The above purpose is to provide CS M to each node station connected to the transmission path.
It is equipped with an A/CD transmission control section and a token transmission control section, and for example, when transmitting a small amount of data, it is transmitted using the CSMA/CD method, and when transmitting a large amount of data, it is achieved by transmitting using the token method.

[For production]

Normally, each node station uses the transmission path equally according to the CSMA/CD method. When a certain node station wants to transmit a large amount of data, the node station instructs all node stations to change the setting of the transmission path from the CSMA/CD system to the token system. Thereafter, all node stations connected to the transmission path use the transmission path in a token manner. When a transmission line is used in a token system, the transmission right is passed to all node stations in turn, so both node stations transmitting large amounts of data and node stations transmitting small amounts of data can equally use the transmission line. Furthermore, since there is no conflict due to contention for the right to transmit on the transmission line, the transmission line can be used effectively.

After transmitting a large amount of data, the node station that issued the instruction to change the settings issues an instruction to all node stations to cancel the settings for the token system. Thereafter, all node stations connected to the transmission line use the transmission line again in the CSMA/CD system. As a result, all node stations have equal transmission rights, and there is no collision between node stations even if the utilization rate of the transmission path becomes low.

High-speed data transmission becomes possible.

〔Example〕

EMBODIMENT OF THE INVENTION Below, one embodiment of the present invention will be described in detail with reference to the drawings.

FIG. 1 shows a network system according to an embodiment of the present invention. Node stations 1, 2, 3, and 4 are each connected to a transmission line 5. The node station 1 includes a transmitting/receiving unit 11 that performs transmission and reception with other node stations 2 to 4, a CSMA/CD transmission control unit 111 that performs CSMA/CD transmission control, and a token transmission control unit 112 that performs token system transmission control. , a buffer 12 for storing transmitted and received data, a data length register 14 for storing a flag when the transmitted data length is longer than a certain length, and a local address register 13 for storing the local address. The same applies to the other node stations 2 to 4. The contents of the local station address register 13 are set in advance prior to data transmission. At the time of transmission, the node station 1 stores the transmission data in the buffer 12 prior to data transmission, checks the transmission data length, and if it is longer than a certain length, sets It in the data length register 14.
Set I It, and if the length is shorter than a certain value but equal, set "O".

First, an overview of the transmission control of the general C, SMA/CD system and problems when the utilization rate of the transmission path is high, such as when transmitting a large amount of data, will be explained.

FIG. 2 shows transmission and reception data 6 of node station 1, and similarly transmission and reception data 7 to 9 of node stations 2 to 4. This example shows a timing chart when a small amount of data 15 is transmitted from station 1 to station 2. There is. In this case, without colliding with data transmissions of other node stations.

Data transmission occurs normally.

The transmitting/receiving unit 11 of the node station 1 senses the carrier wave to check whether other node stations 2 to 4 are using the transmission path 5.

If other node stations 2 to 4 are using the transmission line 5, the system waits until the transmission line 5 becomes free. Other node stations 2 to 4 are transmission path 5
If the transmitting/receiving section 11. is the preamble (hereinafter referred to as P) 16 and buffer 1 that I generated myself.
Destination address read from 2 (hereinafter referred to as A)
17 and data (hereinafter referred to as D) 18 are transmitted data 15
It is transmitted to the transmission path 5 as PI3. A17 and Dl, 8
It is assumed that the length of is specified between node stations 1-4.

Node stations 2 to 4 receive the transmission data 15 from node station J in their transmitting/receiving units, and if A7 is the address of their own station, take it into the buffer of D1.8 as data addressed to their own station, A. If ]7 is not the address of the local station, the transmission data ]5 from node station 1 is discarded.

In this example, data 15 is transmitted from node station 1 to node station 2.
Since the address of the node station 2 is transmitted, A17 contains the address of the node station 2. Therefore, the node station 2 receives the transmission data 15 of the node station ]7 at the transmitter/receiver unit [2], and since A17 is its own address, Dl8 is sent to the buffer 2 as the data addressed to the own station.
Store in 2. Node stations 3 and 4 similarly receive transmission data 15 from node station 1, but since the address A7 is not addressed to their own station, they discard transmission data 15 from node station 1.

In this way, data is transmitted from the node station 1 to the node station 2. A response from the node station 2 to the node station 1 is also made in the same manner.

Generally, in the C3MAlCD system, the node stations 1 to 4 can start transmission whenever the transmission path 5 is free, and therefore there is a possibility that a collision will occur when starting transmission between multiple node stations. In FIG. 1, when node station 2 starts transmitting, node station 2 also starts transmitting at the same time, and a case will be described with reference to FIG. 73, where a collision occurs. It is assumed that the node stations 3 and 4 do not use the transmission line 5 during this time.

Since the transmission line 5 of the node station 1- is vacant, the transmitting/receiving section]
, ] - starts transmitting P31. Similarly, since the transmission path 5 of the node station 2 is vacant, the transmitter/receiver 21 transmits P4]
- starts sending. The transmitting/receiving unit 11 receives data from the transmission path 5 even during the transmission of P31, and compares the data received during the transmission of P:31- with the data of the P31 being transmitted.

For this reason, the transmitting/receiving unit 11 receives P;
31 and P41 of node station 2 overlap, P3J being transmitted
and the received data do not match, and a collision is detected. When a collision is detected, the transmitter/receiver 1-1 transmits P31. Stop sending.

Node j6'y 2 is also detected in the same way as node station 1, and P4
Stop sending 1+1-. The above P31 and P41 take into consideration the time required to reach all stations. Furthermore, the timing of stopping P31 and P41 after a collision is detected is determined by all stations.

When the transmitting/receiving unit 1 of the node station 1 detects a collision, it determines the waiting time Tl for retransmission from the random number table in the transmitting/receiving unit.
32, and attempts to retransmit the transmission data 33 after Tl 32 from the stop of transmission. In this example, T132 is better than T23.
Since it is smaller than 4, node 1- succeeds in retransmission first. The node station 2 retransmits after the transmission is stopped T242, but since TUDOL1 is in use, it will be after the node station transmits.

The above is a general CSMA/CD transmission control system, and when the utilization rate of the transmission path 5 becomes high, collisions occur frequently and the transmission path cannot be used effectively. For this reason, in the second aspect of the invention, the transmission control method in the case of transmitting a large amount of data, for example, is changed from the CSMA/CD method to the token method.

In the 1--Kun system, only node stations designated by transmission data containing a token (specific bit pattern) called a go-ahead can obtain successive transmission rights. In this example, the addresses of node stations 1 to 4 are 1 to 4, respectively.
Then, the token-based transmission right goes from node station 1 to node station 2.
→Node station 3→Node station 4→Node station 1→... When transmitting a small amount of data, the node stations 1 to 4 perform data transmission using the C3MA/CD method.

However, in the case of transmitting a large amount of data, the node stations 1 to 4 change the transmission control method of the transmission path 5 from the CSMA/CD method to the token method, and transmit the large amount of data.

The operation of changing the setting of the transmission control method of the transmission path 5 from the CSMA/CD method to the token method will be described below.

Figure 4 is a timing chart in this case, where node station 1
The transmitted and received data from node station 1 to node station 4 are represented by 36 to 39, and the transmitted data from node station 1 to node station 4 are represented by 50 to 90.

The transmission data 50 is a token called go-ahead (hereinafter referred to as G) 51. Instruction bit (hereinafter referred to as "F") 52 for changing the transmission control method from the CSMA/CD method to the token method, own station address (hereinafter referred to as "F") 5
3, destination address (hereinafter referred to as T) 54, and D55. In addition.

G51. I52. F1a, T54. It is assumed that the length of D55 and the timing of starting transmission are agreed upon between the node stations 1 to 4. The transmission data 60 to 90 are also similar, so the explanation will be omitted.

The value of I52 specifies the transmission control method of transmission path 5 as CSMA/C.
When changing from the D method to the token method, it is set from O to 1, and when changing from the token method to the CSMA/CD method, it is reset from 1 to 0. I52. T53
．． F54. D55 is stored in the buffer 12.

FIG. 4 shows a case where a large amount of data is divided into blocks and transmitted from the node station 1 to the node station 3, and at this time, the data transmitted from the other node stations 2 to 4 is a small amount. Further, in this example, when the node station 1 transmits, the other node stations 2 to 4 do not use it and there is no collision. If there is a collision, the retransmission process described above is performed.

The transmission control method of the transmission path 5 before the transmission of the transmission data 50 of the node station 1 is the C3MAlCD method, and since a large amount of data is transmitted when the transmission right is handed over to the node station 1, the token method will be used hereinafter. Data transmission is performed according to the transmission control method. When the transmission path 5 is empty, the transmitter/receiver 11 transmits G5.
1 and the value 1'1'' read from the data length register 14 to I52, and F1 read from the buffer 12.
a, T54, and D55 are transmitted to the transmission path 5 as transmission data 50. At this time, if the content read into the data length register 14 is "1", the transmitter/receiver 11 transfers transmission control from the CSMA/CD controller 111 to the token controller 11.
2, and transmit using the token method. If the content of the data length register 14 is “0”, the C3MA
The data is transmitted using the C5MA/CD method, which is the transmission control of the /CD control unit 111. Further, the transmitter/receiver 11 performs the above-mentioned transmission until there is no more data to read from the buffer 12, and when there is no more data to be read from the buffer 12,
Send the transmission data 50 set to I+.

When the node stations 2 to 4 receive I52, they stop competing for the transmission right by controlling the transmission line 5 using the C3MA/CD method, and switch to the token-based transmission control method. Also, the node stations 2 to 4.

The message “52” indicates that the node station 1 has finished transmitting large amounts of data.
0", the transmission control method is switched from the token method to the CS MA/CD method. In this example, F1a is set to 1 in order to transmit from node 1 to node 3.
In this case, T54 is set to 3. Therefore, the transmission right can only be used by the next node station, that is, node station 2, at F1a according to the token-based schedule. As a result,
Since the node station 2 has been able to obtain the transmission right, it can start transmitting immediately as soon as the transmission path 5 becomes vacant.

When the transmitting/receiving unit 21 of the node station 2 detects a non-transmission state on the transmission line 5, it transmits G61 and I62 read from the buffer 22.
, F1a, T64, and D65 are transmitted to the transmission path 5.

When the node station 2 receives I52 set to 1 in the transmission data 50 of the node station 1 prior to transmitting the transmission data 50, it stores I62 to the same value as I52 in the cellar 1-shibaranoa 22. Similarly to the above, when node station 3.4 receives the transmission right, it transmits transmission data 70.80 with I72.82 set to 1.

As described above, transmission and reception of large amounts of data and small amounts of data and transfer of transmission rights are performed. From node station J- to node station 3
If there is still a large amount of data to be sent to the node station, the same process as for sending the transmission data 50 is performed, but if the large amount of data has been sent from the node station 1 to the node station 3, , performs the following processing.

After the transmission from node station 4 to node station 1 is completed, node station 1
When the transmission right comes to , the transmitter/receiver 11 sends G91 and
A transmitting/receiving unit that transmits the transmission data 90 consisting of T92, 1?93, T94, and D95 reset to the transmission path 5]
-1, reads the length of the data to be transmitted from the buffer 1-2 prior to the transmission data of the transmission data 90, and changes the transmission control method of the transmission path 5 from the token method to the CSMA/CD method because there is no data to be transmitted. Set I52 to 0 to change
is reset and stored in buffer J2. Node stations) 2 to 4 receive I92 which has been reset to 0.

Until then, the transmission right had been transferred by controlling the transmission line 5 to the 1-m-kun system, but the transmission right was changed to the 1-m-kun system, but the transmission right was transferred to the transmission line using the same CSMA/CD transmission control system as before receiving the transmission data 50. The situation returns to the state where the transmission right of No. 5 is contested.

As described above, even if the station to which the transmission right has been designated is unable to transmit, the next station automatically transmits, so that the transfer of the transmission right can be continued.

Although one embodiment of the present invention has been described above, the following may be considered as other embodiments. In the above embodiment, the transmission control method of the transmission path 5 is set and canceled by the node station itself that transmits a large amount of data, but all stations connected to the transmission path 5 monitor the utilization rate of the transmission path 5. , when a certain value is exceeded, the above-mentioned steps 52 to 92 are set, and the transmission control method of the transmission line 5 is changed from the CS MAlCD method to the 1 to -kun method. Further, when the utilization rate of the transmission line 5 falls below a certain value, the above-mentioned switch 52-92 is reset and the transmission control method of the transmission line 5 is changed from the token method to the CSMA/CD method.

〔Effect of the invention〕

As is clear from the above description, according to the present invention, in the case of a small amount of data, data transmission can be performed at high speed since transmission control is performed using the CS MAlCD method. Furthermore, when transmitting a large amount of data, the transmitting/receiving station of the large amount of data changes the setting of the transmission control method of the transmission path from the CSMA/CD method to the token method, thereby eliminating transmission collisions between node stations.

The transmission path can be used effectively, and since the transmission rights of stations connected to the transmission path are equally served, there is an effect that there is no drop in service.

[Brief explanation of the drawing]

Fig. 2 is a diagram showing a network system according to an embodiment of the present invention, Fig. 2 is a timing chart illustrating transmission control when there is no collision according to the CS MAlCD method, Fig.
Figure 3 is a timing chart when a collision occurs using the CSMA/CD method, and Figure 4 is a timing chart from the CSMA/CD method.
- It is a timing chart explaining transmission control when changing to a mode. ]~4... Node station, 5... Transmission line, 11.2F
...Transmission/reception unit, 12.22...Buffer, 1
3.23... Own station address register, 14.24...
・Data length register, 111.211...CSMA1CD transmission control section, 11
2.212...Token transmission control unit.

Claims (1)

[Claims] (1) In a network system in which multiple node stations are connected via transmission paths, each node station has CSMA/
A CD control unit and a token control unit are provided, and normally each node station uses the transmission path in the CSMA/CD method, and a certain node station receives an instruction to change the setting of the transmission path from the CSMA/CD method to the token method. 1. A data transmission control system characterized in that when the data transmission control method is performed for a node station, each node station thereafter uses a transmission path in a token system until an instruction is given from the node station to cancel the setting of the token system.