JPS63238743A - Data link control device - Google Patents

Abstract

PURPOSE:To decrease the load of a processor by providing the dividing means of transmission request data and an identification number generating/giving means to respective divided transmission data in a data link control device. CONSTITUTION:A dividing means 2 divides transmission request data 10 and an identification number generating/giving means 3 gives an identification number to respective divided data. A transmission means 4 adds information necessary to a physical layer and a data link layer to the data which are divided and to the identification is given and transmits through a transmission line system 12 as a frame. On the other hand, a receiving means 9 sends the data part including an identification number excluding the information part necessary to a physical layer and a data link layer to a synthesizing means 7. The synchronizing means 7 obtains reception completion data 11 with the identification number. Thus, since it is not necessary for a processor itself to divide and synthesize the transmission data in a communication control procedure, the decrease in the load of the processor and the high speed of the communication can be executed.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a data link control device connected to a local area network.

[Summary of the invention]

The present invention divides data exceeding the maximum transmission unit determined by the characteristics of the transmission path and the access method to the transmission path, which are characteristics of the physical layer and data link layer, within the data link control device, and uses the identification number necessary for combining. This is a data link control device that has four means: a means for generating, assigning, and transmitting an identification number, and a means for synthesizing received data using an identification number.

By using the present invention, it is possible to reduce the load on a processor for performing communication procedures.

[Conventional technology]

In conventional local area networks, when transmitting and receiving data in an amount exceeding the physical maximum transmission unit, it is necessary to divide and combine the data.

The maximum transmission unit, which is a standard for division-1 combining, is determined by the characteristics of the physical layer and data link layer, such as the nature of the transmission path and the means of accessing the transmission path. Therefore, in many conventional communication control procedures, the processor often performs division and synthesis according to the communication procedure of the network layer located above the data link layer.

For example, in the communication control procedure used in ARPANET, in the Internet protocol, transmission request data from the upper layer is divided and combined according to the maximum transmission unit of each data link according to the communication control procedure of the network layer. Conventionally, division and synthesis have been performed as part of communication control means performed by a processor.

[Problem that the invention seeks to solve]

Conventionally, division and combination of data exceeding the maximum transmission unit has been performed by a processor as part of a communication control procedure. In particular, it is often incorporated into the communication control procedure of the network layer, and is extremely complex because it is necessary to take into account complex network shapes, unreliable communication media, and data link procedures.

Therefore, there is a problem that a large amount of processor processing time is required, which further impedes the high-speed performance of the local area network.

An object of the present invention is to provide a data link control device having means for dividing and transmitting and receiving and combining data in order to speed up communication and reduce processor load without changing conventional communication control procedures.

[Means for solving problems]

In order to solve the above problems, the present invention adds a dividing means for dividing transmission request data and an identification number generating means for assigning an identification number to each divided transmission data into a data link control device. It is now possible to divide the transmission request data and send it.

Furthermore, when divided transmission data is received, it is possible to synthesize and restore it into the form of transmission request data using the identification number assigned by the identification number generation and assignment means.

Furthermore, in order to prevent the receiving side from retaining received data to be combined with the already received missing transmission data for a longer period of time when transmission data is lost, a monitoring means is provided for monitoring the completion of combination with a timer.

[Effect]

By incorporating automatic synthesis and automatic division of data using identification numbers into the data link control device as in the above-mentioned means, the communication control procedure performed by the processor to control the data link becomes simple.

〔Example〕

Hereinafter, a preferred embodiment of the present invention will be described with reference to the accompanying drawings.

As shown in the block diagram of FIG. 1, the data link control device 1 of the present invention includes dividing means 2. Identification number generation and assignment means 3. Transmitting means 4 and transmitting side 1b
receiving means 91 included in combining means 7. It has monitoring means 8.

The dividing means 2 divides the transmission request data 10 according to the maximum transmission unit, which is a constant determined by the characteristics of the transmission line system 12, such as 1514 bytes in the case of Ethernet, and sends it to the identification number generating means 3. For each divided data, the identification number generation and assignment means 3 includes an MF indicating whether the divided data is the last of the transmission request data and the number of each divided data, as shown in FIG. Sequence number 0. An identification number 34 including SA, which is a unique value, is assigned to the FF and each data link control device.

The transmitting means 4 transmits the divided data to which identification numbers 34 have been assigned to the physical layer, as shown in FIG.

Receiving station address 31, which is a header section necessary for the data link layer. Transmitting station address 32. A type 33 indicating the frame format is added, and the frame is transmitted as a frame through the transmission path system 11.

When receiving the frames transmitted by the transmitting means 4 in the format shown in FIG. 3 one after another, the receiving means 9 receives the receiving station address 31. which is a header part necessary for the physical layer and the data link layer. Transmitting station address 32. The portion excluding type 33 is sent to the synthesizing means 7.

The synthesizing means 7 separates the identification number 34 and the data part 35,
As shown in the flowchart of FIG. 4, it is determined whether the data 35 is a continuation of the previously received data 35 or not using the separated identification number 34.

If the SA in the identification number 32 of the previously received frame is not equal to the SA in the identification number 32 of the received frame, as shown at 42 in FIG. 4, then this data 35 is not a continuation of the previously received data 35.

Also, the sequence number next to OFF in the identification number 32 of the previous received frame is OFF in the identification number 32 of the received frame.
If it is not equal to FF, this received data 35 is not a continuation of the previous received data 35.

If the received data 35 is not a continuation of the previous received data 35, the previous received data 35 is discarded, the current received data 35 and identification number 34 are retained, and a monitoring request signal 6 is output to the monitoring means 8. .

In this case, a frame is lost on the data link, but normally the data link itself is not required to be reliable, and the upper communication control procedure retransmits the lost data, so there is no problem.

If the received data 35 is a continuation of the previous received data 35, the received data 3
5 is held connected to the previously received data 35, and the identification number 34 is held for the next comparison.

Furthermore, when the MF in this identification number 34 indicates that it is the last received data, the data that has been held and combined up to the present is output as reception completion data 11.

Furthermore, the monitoring means 8 has the purpose of monitoring the synthesis with a timer in case a part of the divided and transmitted frame is lost. If some frames are missing, all data 35 that should follow that frame must be discarded.

Therefore, the monitoring means 8 has a synthesis monitoring timer with a length that does not affect the communication control procedure of the upper layer, and the synthesis means 7
The timer is started by the monitoring request signal 6 from
When a timeout occurs, a timeout signal 5 is output. In response to this timeout signal, the combining means receives the received data 35. The identification signal 34 is discarded and initialized.

(Effects of the Invention) By using the data link control device of the present invention, the communication control procedure performed by the processor can be handled as if the maximum transmission unit had become larger. This reduces the need for the processor itself to divide and combine transmission data in the communication control procedure, reducing the load on the processor and increasing the speed of communication.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing a data link control device of the present invention. FIG. 2 is a diagram showing the format of the identification number. FIG. 3 is a diagram showing the frame format on the medium. FIG. 4 is a flowchart of frame identification by the combining means. FIG. 5 is a flowchart of the combining means to frontiture 1 during correct frame reception. 1...Data link control device 2...Dividing means 3...Identification number generation and assigning means 4...Transmitting means 5...Timeout signal 6...Monitoring request signal 7...Synthesizing means 8. ... Monitoring means 9 ... Receiving means 31 ... Receiving station address 32 ... Transmitting station address 33 ... Type code 34 ... Identification number 35 ... Data SA ... Unique to the data link control device The value of MF
... Code indicating the last data 0FF - ... Sequence number indicating the order of data ¥ 1 Figure Identification Figure supporting each number C shape 2' ¥) 2 Figures

Claims (1)

[Claims] In a data link control device connected to a local area network, a) dividing means for dividing transmission request data according to a maximum transmission unit; b) for transmission data divided by the dividing means,
an identification number generating and assigning means for generating and assigning an identification number; c) a transmitting means for transmitting transmission data to which an identification number has been assigned by the identification number generating and assigning means through a physical layer; and d) a physical layer for transmitting data transmitted by the transmitting means. receiving means for receiving data through the layer; e) combining means for combining received data using the identification number assigned by the identification number generation and assignment means in the received data received by the receiving means; f) composition of the combining means. A data link control device comprising a monitoring means for monitoring completion using a timer.