JPH0744577B2 - Communication control device - Google Patents

Description

TECHNICAL FIELD The present invention relates to a communication control device, and more specifically, to communication for communicating with an opposite device using a high level data link protocol such as a high level data link control procedure. The present invention relates to a control system, and more particularly to a management system of a buffer for temporarily storing the information.

(Prior Art) In a conventional communication control device, a plurality of line accommodating units respectively connected to a plurality of opposite devices through lines are multiplexed and controlled by a common control system. For example, "Technology Transfer Special Seminar Text" Packet Switching Network "" published by Japan Communication Technology Co., Ltd.
Such a communication control device is described on pages 23 to 24 (March 1985). The control system is provided with a processing device and a main storage device, and these are connected to the line accommodation unit via a common bus. The right to use the bus is assigned by the arbiter.

In this type of device, information transmitted to and received from the opposite device is temporarily stored in the buffer area of the main storage device. More specifically, the information transmitted from the processing device to the specific opposite device via the line accommodation unit is temporarily stored in the buffer area of the main storage device, and after the line accommodation unit sets the link with the opposite device, the information is transmitted to the main device. The data is transmitted to the opposite device while being read from the storage device. The buffer area storing the transmitted information is released after receiving the delivery confirmation from the opposite device. Further, the specific line accommodating unit that receives the information from the opposite device requests the processing device to allocate the buffer area of the main storage device. Generally, there are many methods in which a buffer area is given in advance. When the line accommodating unit stores, for example, one frame of information in the buffer area, the management right of the area is transferred to the processing device, and the processing device then performs necessary processing on this information.

As described above, in the conventional communication control device, a buffer area for temporary storage of transmission / reception information is provided in the main storage device of the control system, which is external to the line accommodation unit for exchanging information with the opposite device, and its management is also performed by the control system. It was done in the processor.

(Problems to be Solved by the Invention) However, the temporary storage of transmission / reception information and the transmission / reception operation are essentially a series of operations closely related to each other. Therefore, as in the conventional system, in the system in which the temporary storage area of information is managed by the control system other than the line accommodating unit that actually transmits and receives information,
The function allocation between the line accommodating part and the control system, and the interface conditions between them were complicated.

In order to solve this problem, it is conceivable to simply provide a buffer in each line accommodation unit. However, in such a structure, a division loss of the buffer area occurs, and a large swarm effect on traffic cannot be expected. Therefore, the entire apparatus requires a much larger storage capacity than the conventional method in which the buffer area is concentratedly arranged in the control system.

SUMMARY OF THE INVENTION It is an object of the present invention to solve the above-mentioned drawbacks of the prior art and to provide a communication control device in which the function sharing and interface conditions between the line accommodation unit and other devices, especially higher-order devices, are simplified. .

(Means for Solving the Problems) In order to solve the above-mentioned problems, the present invention provides a buffer function for temporarily storing information to be transmitted / received to / from an opposite device to a functional portion that is actually responsible for transmission / reception. In addition to being installed, it is also installed in the shared area outside of it, and both are used properly according to predetermined conditions. This makes it possible to obtain a large effect of the buffer function unit, and eliminates the problems that may occur when the buffer management and the information transmission / reception operations are performed by different function units.

According to the present invention, a plurality of transmission / reception means that are respectively connected to the lines to the opposite apparatus and perform information transmission / reception to / from the opposite apparatus in accordance with a predetermined transmission control procedure are supported via any of the plurality of transmission / reception means. In a communication control device including a processing means for processing information transmitted / received to / from the opposite device, and a connection means for commonly connecting the plurality of transmitting / receiving means to the processing means, each of the plurality of transmitting / receiving means corresponds to the transmitting / receiving means. For temporarily storing transmission / reception information for the opposite device
The storage means has a second storage means that is commonly used by a plurality of transmission / reception means and temporarily stores transmission / reception information for any of the opposite devices, and the first storage means has a transmission / reception means. Information that satisfies a predetermined condition is temporarily stored, and transmission / reception information stored in the first storage unit that does not satisfy the predetermined condition is saved in the second storage unit. This predetermined condition is set so that the amount of transmission / reception information stored in the first storage means does not exceed the storage capacity of the first storage means.

(Operation) According to the present invention, the buffer function for temporarily storing the information to be transmitted / received to / from the opposite device is provided not only in the transmitting / receiving means which actually takes charge of the transmitting / receiving but also in common to the processing means outside thereof. Has been done. The transmission / reception information is temporarily stored in the first storage means, but if the predetermined condition is not satisfied, the first
Is stored in the second storage means.

In this specification, the term “transmission / reception” is to be interpreted as a selective meaning including at least one of transmission and reception.

(Embodiment) Before describing an embodiment of the present invention, an example of a conventional method will be described with reference to FIG. 3 in order to facilitate understanding. This is the communication control device described on pages 23 to 24 of "Packet Switching Network" published by Nippon Communication Technology Co., Ltd. In the communication control device 10, a plurality of N line accommodating units LU1 to LUN, which accommodate the lines 12 to a plurality of opposite devices, are multiplexed and controlled by a common control system. The line accommodating units LU1 to LUN are line termination devices that are oppositely connected to the part corresponding to the line accommodating unit of the opposite device and perform control for setting a data link by a sophisticated transmission control procedure such as HDLC.

The control system includes a processing device CP and a main memory device MM, and these are connected to the line accommodation units LU1 to LUN via a common bus 14.
The right to use the bus 14 is the arbiter 16 and the line accommodation units LU1 to LUN,
Allocated between the processor CP and the main memory MM.
The main storage device MM not only stores the program of the processing device CP, but also has a buffer area for temporarily storing the information transmitted / received to / from the opposite device.

When the information processed by the processing device CP is transmitted to the opposite device via the line accommodation unit LU1, for example, the information is temporarily stored in the buffer area of the main storage device MM and the information transmission is performed by the line accommodation unit. Request to LU1. This request is written in the form of a command on the main memory MM in this conventional example. When the line accommodation unit LU1 reads this command, it sets a link with the opposite device according to the HDLC procedure, reads this information from the main storage device MM, and sends it to the opposite device. When the transmission is completed and the delivery confirmation signal from the opposite device is received, the line accommodation unit LU1 notifies the processing device CP to that effect. In response to this, the processing device releases the buffer area storing the transmitted information to another.

For example, when the line accommodation unit LU1 receives information from the opposite device, the line accommodation unit LU1 sends the information to the processing device CP to the main storage device M.
Request allocation of M buffer space. Generally, in this way, a buffer area is allocated in advance in this way. When the line accommodation unit LU1 receives information from the opposite device and accumulates one frame of information in the buffer area, it notifies the processing device CP of that fact and transfers the management right of the area to the processing device CP. The processing device CP then carries out the necessary processing on this information.

As described above, in the conventional communication control device 10, a buffer area for temporarily storing transmission / reception information is provided in the main storage device MM of the control system, which is external to the line accommodation units LU1 to LUN for exchanging information with the opposite device. , Its management was also done by the processor CP.

Next, an embodiment of the communication control device according to the present invention will be described in detail with reference to FIG. The communication control device in this embodiment constitutes the lower three layers of the seven layers (layers) of the open system interconnection (OSI), that is, the physical layer L1, the data link layer L2 and the network layer L3.
In this embodiment, the physical layer L1 and the data link layer L2 are arranged in a one-to-one correspondence with the opposite device, and constitute a transmission / reception function unit corresponding to the line. However, the network layer L3 is arranged in common for a combination of a plurality (n + 1) sets of layers L1 and L2, and is in the form of a processing function unit for performing multiple processing on them.

Of such a configuration, the part particularly targeted by the present invention is a part including (n + 1) data link layers L2 and an L3 processing device 50 interfacing with them. Hereinafter, these parts will be described in detail.

The data link layer L2 has a transmission / reception unit 52 and has a corresponding physical layer.
It is connected to the opposite device by a line 12 via L1.
The transmission / reception unit 52 is a functional unit that performs transmission / reception operations of information with the opposite device via the physical layer L1 in accordance with a sophisticated transmission control procedure such as HDLC. The data link layer L2 has a buffer memory that temporarily stores this transmitted / received information.
54 is provided. The buffer memory control unit (BMC) 56 performs necessary control such as allocation of the buffer area. Transmitter / receiver 52 and buffer memory controller
Each component of the data link layer L2 such as 56 is controlled by the L2 control unit 58, which is responsible for high-level processing such as order control of the data link layer L2.

In this embodiment, the processing of one network layer L3 provided in common to (n + 1) data link layers L2 is responsible.
An L3 processor 50 is provided. L3 processor 50 has L3
Large capacity buffer 62 and L2 via the processing system (P) bus 60
/ L3 transfer device 64 is connected, L2 / L3 transfer device 64 is L2 / L3
(N + 1) data link layers L20 by the transfer bus 66
~ Commonly connected to L2n. The large capacity buffer 62 is
It is a buffer device that temporarily stores information transmitted and received to and from the opposite device. L2 / L3 transfer device 64 is a data link layer L
It is a functional unit that controls the transfer of information between the network layer 2 and the network layer L3.

As can be seen from this, in the present embodiment, the buffer memory 54, which is individually arranged for the opposite device in the data link layer L2, and the (n + 1) data link layer L2 are commonly used as a temporary storage place of the transmission / reception information. And a large-capacity buffer 62 provided in the network layer L3.

The information transmission / reception operation to / from the opposite device is actually performed in the data link layer L2. Therefore, basically, it is preferable that the data link layer L2 be responsible for managing the buffer that temporarily stores the transmission / reception information. However, in this embodiment,
The two buffers 54 and 62 are selectively used as follows. That is, the information of the property that the scale of the information to be buffered is uniquely determined in the system is stored in the buffer memory 54 of the data link layer L2, the type of the communication protocol to be supported, the result of the negotiation of the communication setting with the opposite device, etc. The information of the property determined by is stored in a buffer outside the data link layer L2, that is, in the large capacity buffer 62 in this embodiment.

Originally, when transmitting information to the opposite device, the information to be buffered includes not only the information to be transmitted and the information being transmitted, but also information which has been transmitted but whose delivery confirmation signal has not been returned.

As is well known, it is generally accepted that the delivery confirmation signal is transmitted collectively for a plurality of received units of information. The scope of the summarization is determined by the initial negotiation in link establishment. CCITT Recommendation X.25 for example
According to the protocol, it is allowed to send back the acknowledgment signals collectively up to 127 frames. In that case, for example, if 4 Kbytes are included in one frame, a situation may occur in which a delivery confirmation signal is waited for up to about 500 Kbytes of information. In addition, for example, in LAP-D conforming to CCITT Recommendation I series, it is permitted to set a plurality of links, theoretically up to about 8,000, on one line. As described above, it is necessary to secure a buffer area having a considerably large capacity for the information waiting for receipt of the delivery confirmation signal.

As can be seen, the size of the transmission information buffer is uniquely determined depending on the system, and it depends on individual conditions such as the type of communication protocol supported and the result of negotiation of communication settings with the other device. In the latter case, the size of the buffer to be prepared greatly differs depending on the determined parameters. In this embodiment, paying attention to this feature, the former information is stored in the buffer memory 54 in the data link layer L2, that is, the functional portion that actually takes charge of transmission and reception, and the latter information is outside the data link layer L2. A buffer, that is, a large-capacity buffer 62 is configured to be saved and stored.

In this case, the problems are the information saving time, the buffer releasing time, and the range of information to be saved. In this embodiment, as one solution to this problem, a large-capacity buffer is used for information sent to the opposite device that is not confirmed to arrive at the opposite device for a predetermined period defined by the timer described above.
The method is to evacuate to 62.

For example, for an opposite device that is configured to collectively send back acknowledgment signals for received information up to 127 frames, 127 such timers are prepared in the L2 processing unit 58 of the data link layer L2 connected thereto. It As shown in FIG. 2, the L2 processing unit 58 sequentially activates the corresponding timer each time one frame of information is transmitted. Opposite device is 12
When all the information of 7 frames is received, the arrival confirmation signal is sent back, but in the example of FIG. 2, the corresponding timers have timed up to the k-th frame, which is smaller than this, before that. .

When the time is up, the L2 processing unit 58 notifies the L3 processing unit 50 to that effect, and the L3 processing unit 50 secures a storage area for the timed-out information in the large capacity buffer 62. The timed-out information is sequentially read from the buffer memory 54 and stored in L2 / L
3 Transferred by the transfer device 64 to the large capacity buffer 62 and stored. Those areas of the buffer memory 54 are freed up elsewhere. In this way, the timed-out information is saved in the large capacity buffer 62.

However, in this example, 127 from the (k + 1) th frame
Information up to the second frame is held in the buffer memory 54, and a delivery confirmation signal is returned from the opposite device before the timer times out. So buffer memory
Those areas of 54 are released upon receipt of the acknowledgment signal, which also resets their timers.

As described above, the case where the latter is used as the undelivered confirmation information is considered as the condition for selectively using the buffer memory 54 and the large-capacity buffer 62, but the following cases are also possible.

As described above, in the case of LAP-D, multiple links can be set on the same line, and they are distinguished by the value of the address part. For example, in a system in which two links are established, one link per frame, and the other link collectively confirms delivery up to a plurality of frames, for example, up to 7 frames. Large buffer for all information
Information that is saved in 62 and does not significantly affect the buffer size like the former may be saved in the buffer memory 54. Further, it may be configured to save the information of a link using a frame of a large size among a plurality of links. For example, if the frame of one link is 260 bytes and the frame of the other link is 4 kbytes, only the latter may be saved.

As for the buffer outside the data link layer L2, that is, the large-capacity buffer 62, it is preferable to provide one system in common for a plurality of (n + 1) data link layers L2 as in the present embodiment, and the management thereof is a large group effect. The expected dynamic method is desirable. However, dynamic management introduces control complexity. Therefore, in the end, it depends on the trade-off between both features.

In the present embodiment, the L2 / L3 transfer bus 66, the L3P bus 60, and each device are in the form of a bus connection. In the case of these bus couplings, particularly in the former case, the L2 / L3 transfer device 64 having an arbiter function is used to manage the bus use right.

As described above, in this embodiment, in addition to providing a buffer function for temporarily storing information to be transmitted / received to / from the opposite device in each data link layer L2 which is actually in charge of transmission / reception, a plurality of data link layers are provided outside thereof. It is also deployed in the network layer L3 shared by L2. This allows the data link layer
The capacity of the buffer memory 54 in the L2 can be reduced, and the simplicity of the interface between the data link layer L2 and the network layer L3 can be maintained.

(Effect of the invention) As described above, according to the present invention, a buffer function for temporarily storing information to be transmitted / received to / from the opposite device is provided in the transmitting / receiving means which is actually in charge of transmitting / receiving, and the processing means which is a shared portion outside thereof In addition, a buffer function is provided for saving information that cannot be confirmed for delivery for a predetermined time or longer by the transmitting / receiving means. Therefore, the amount of information storage between the transmission / reception function unit and the processing unit can be shared in an appropriate amount, and the buffer capacity of both function units is smaller than when concentrated in one,
Moreover, an excellent effect that the simplicity of the interface between the two parts is maintained can be achieved.

[Brief description of drawings]

FIG. 1 is a system configuration diagram showing an embodiment in which the communication control device according to the present invention is applied to the lower three layers of an open system interconnection, and FIG. 2 is an example of buffer saving in the embodiment shown in FIG. A sequence diagram shown in FIG. 3 is a system configuration diagram showing an example of a conventional communication control buffer management system. Explanation of main part code 50 …… L3 processor 52 …… Transceiver 54 …… Buffer memory 56 …… Buffer memory controller 58 …… L2 processor 60,66 …… Bus 62 …… Large-capacity buffer 64 …… L2 / L3 transfer device

Claims (1)

[Claims] 1. A plurality of transmitting / receiving means, each connected to a line to the opposite device, transmitting / receiving information to / from the opposite device according to a predetermined transmission control procedure, and one of the plurality of transmitting / receiving means. In a communication control device including processing means for processing information transmitted / received to / from a corresponding counterpart device, and a connection means for commonly connecting the plurality of transmission / reception means to the processing means, each of the plurality of transmission / reception means includes: A first storage unit for temporarily storing transmission / reception information for the opposite device corresponding to the transmission / reception unit, wherein the processing unit is commonly used by the plurality of transmission / reception units and temporarily stores the transmission / reception information for one of the opposite devices. The first storage means stores the transmission / reception information from the time when the transmission / reception information is generated until the reception confirmation signal from the opposite device is received. When the delivery confirmation signal to be returned from the opposite device among the transmission / reception information accumulated in the first accumulation means is not returned to the transmission / reception means in the second accumulation means, A communication control device, wherein transmission / reception information corresponding to the delivery confirmation signal is saved from the first storage means.