JPH01236843A - Communication buffer device - Google Patents

Abstract

PURPOSE:To realize the priority control of an effective packet with a small buffer capacity by accumulating a packet to an area regardless of a priority unconditionally when an empty area is present at a storing means. CONSTITUTION:When an empty area is present at a storing means 12, a packet is accumulated into the area regardless of the priority unconditionally. When the abolition of the packet is necessary, a packet abolishing means 13 determines the packet abolished from the priority of respective packets and the abolishing processing is executed. When the output action of the packet is necessary, a packet output means 14 determines the packet outputted from the priority of respective packets and fetches the packet. Consequently, a wasteful empty area does not occur at the memory area and the memory area can be effectively used. Thus, the priority control of the effective packet is realized by a small buffer capacity.

Description

[Detailed Description of the Invention] [Object of the Invention] (Industrial Application Field) The present invention relates to a communication buffer device that is provided at an input section of a communication path in a packet communication system and temporarily stores information packets. In particular, the present invention relates to a communication buffer device that implements a packet priority control system.

(Prior Art) In recent years, with the development of digital communication networks, packet communication systems have become widely used.

As is well known, in the packet communication method, a destination address is attached to each information packet, so a communication channel can be used only for evening information communication, and a communication channel with the same capability can be used by more users. There is an advantage that they can be used simultaneously, and as a result, communication efficiency can be improved and communication costs can be reduced.

By the way, in the packet communication method, because many users use the same communication channel at the same time, a phenomenon occurs in which information that exceeds the capacity of the communication channel is concentrated on the communication channel, that is, a congestion phenomenon occurs, and the packet There is a problem in that it causes a lack of information. Therefore, in order to solve this problem, in a packet communication system, a communication buffer is provided at the input part of the communication path, and packets to be sent are temporarily stored until the congestion condition of the communication path is resolved. being done. By using this communication buffer, it is possible to prevent packet loss within a certain limit in a congestion situation.

However, since the capacity of the communication buffer is finite,
If a particular communication path continues to be congested for a long time, it becomes impossible to store new packets in the communication buffer, which may cause packet loss. Furthermore, when such a long-term congestion state occurs, there is also the drawback that the time from when a certain packet is accumulated in the buffer until it is output increases.

Conventionally, in order to solve these drawbacks, a packet priority control method is known in which each packet is assigned a priority and the packet with a higher priority is outputted before the packet with a lower priority. According to this method, packet loss is
Packets are generated in order of priority. In a system where there is a mixture of communication where packet loss has a large impact and communication with a small impact, if packet loss occurs in the order of packet loss starting with the packet that has the least impact, an effective method for sharing the communication path can be realized. .

FIG. 5 shows the configuration of a communication buffer device for realizing this method. A plurality of FIFOs (First in F) provided between the first communication path 51 and the second communication path 52
irst out) buffer y531.532.

. . , 53n are buffers that store packets according to priority. The demultiplexer 54 that receives the packet to be transmitted from the first communication path 51 distributes the received packet to a specific FIFO buffer 531 according to the priority. The multiplexer 55 selects the FIFO with the highest priority among the FIFO buffers 53i storing packets.
Select the FO buffer 53i and save the FIFO buffer 5
31 and outputs it to the second communication path 52.

In such systems, packets are sent to the FIF according to their priority.
The packets are stored in the O buffer 531, and when the multiplexer 55 outputs the packets, the FIF in which the packets are stored is
Since packets are taken out from the FIFO buffer 531 assigned to the highest priority among the O buffers 531, packet loss will eventually occur from packets with a low priority.

However, in a conventional communication buffer device in which FIFO buffers 531 are provided for each priority, if the priority of packets to be communicated is biased towards a certain priority, the number of packets stored in each FIFO buffer 53i will vary. Therefore, there is a problem in that the usage efficiency of the storage area of the FIFO buffer 53i decreases.

(Problem to be Solved by the Invention) As described above, the conventional communication buffer device that implements a packet priority control method by providing a buffer for each priority has the problem of inefficient use of the buffer storage area. .

The present invention has been made in view of the above-mentioned problems, and it is possible to improve the usage efficiency of storage area in a communication buffer device that implements a packet priority control method, thereby making it possible to effectively manage packets with less storage space. An object of the present invention is to provide a communication buffer device that can realize priority control.

[Structure of the Invention] (Means for Solving the Problems) The present invention includes a storage means for accumulating information packets, an input of information packets to be transmitted, detecting free space in the storage means, packet input means for storing information packets stored in the free area in the free area; packet discard means for selecting and discarding information packets to be discarded from the storage means based on the priority of each information packet stored in the storage means; Similarly, the present invention is characterized by comprising a packet output means for selecting and outputting information packets to be output from the storage means based on the priority of each information packet stored in the storage means.

Here, the packet priority refers to information such as the magnitude of the impact that discarding a packet has on communication (discard priority) and the magnitude of the influence that packet delay has on communication (output priority). In particular, it is based on the nature of the packet, the type of transmitting/receiving terminal, the order of storage in the communication buffer device, etc. This priority can be associated with the packet in various ways, such as being carried as information in the packet itself, being added when the packet is stored in a buffer, or being provided as management information of the storage means. can.

In a preferred aspect of the present invention, the packet discarding means selects and discards the information packets stored in the storage device in a time shorter than the time required to transfer the information packets on the communication path, and The packet output means selects and outputs the information packets stored in the storage device in a time shorter than the time required to transfer the information pieces on the communication path.

Further, the storage means is provided, for example, with a plurality of registers for storing each information packet, and is provided corresponding to each of these registers, so that while the information packet is stored in the corresponding register, the packet discarding means Discarding information packets and reducing the output of information packets by the packet output means (including a counting means (the counted value serves as a priority standard) that performs an increment operation each time one of the information packets is discarded. It has become a thing.

(Operation) According to the present invention, if there is q free area in the storage means, packets are unconditionally accumulated in that area regardless of priority. When it is necessary to discard a packet, the packet discard means determines the packet to be discarded based on the priority of each packet, and performs the discard process. Further, when a packet output operation is required, the packet output means determines the packet to be output based on the priority of each packet and extracts the packet. Therefore, according to the present invention, the storage area can be used effectively without creating unnecessary free space in the storage area. Therefore, effective packet priority control can be achieved with a small buffer capacity.

Note that if the packet discarding means performs the packet discarding operation in a time shorter than the time required to transfer the packets on the communication path, the packets to be transmitted that are continuously input to the packet inputting means can be If the packets can be stored in the storage means without stagnation, and if the packet output operation is performed by the packet output means in a shorter time than the time required to transfer the packets on the communication path, there will be no idle time on the communication path. Packets can be transmitted continuously without any occurrence of

Furthermore, if a counting means is provided corresponding to the register storing each packet, and this counting means is made to count up each time a packet is discarded or output, the counted value of the counting means indicates the accumulation order of the packet. Therefore,
Packets can be output to a transfer path based on their accumulation time, and packet waiting time can be reduced.

(Example) Hereinafter, an example of the present invention will be described based on the drawings.

FIG. 1 is a block diagram showing the configuration of a communication buffer device according to an embodiment of the present invention.

A communication buffer device 3 provided between a first communication path 1 and a second communication path 2 is configured to prioritize packets input via the first communication path 1 while transferring them to the second communication path 2. At the same time, the packet is discarded as appropriate. This communication buffer device 3 includes a packet input device 11, a storage device 12, a packet discard device 13, and a packet output device 14.

The packet human power device 11 is configured as shown in FIG. 2, for example. The input buffer 21 temporarily stores packets to be transmitted that are input via the first communication path 1 . The priority adding circuit 22 determines the priority of the packet stored in the input buffer 21 based on the type of the packet, etc., and outputs information indicating the priority. This priority is determined by, for example, the magnitude of the impact that discarding a packet has on communication (
Discard priority) and the magnitude of the impact that packet delay has on communication (output priority), etc. Specifically, it includes information such as the nature of the packet (for example, broadcast transfer, general communication, etc.), the type of sending and receiving terminal, It is determined based on the order of accumulation in the communication buffer device, etc.

The free space detection circuit 23 searches for a free space in the storage device 12 based on a free space flag (described later) given from the storage device 12, and if no free space is detected, outputs an overflow signal to the packet discard device 13. However, if a free area is detected, it outputs the address of that area and also outputs a write signal to the input buffer 21. The input buffer 21 receives this write signal and outputs the stored packet to the storage device 12. At this time, priority information from the priority addition circuit 22 is added to the packet.

The storage device 12 is a random access memory that stores packets input manually from the packet input device 11, and includes a plurality of registers 311, 312 . . . as shown in FIG. 3, for example.
..., 31n. Each register 311
(i-1 to n) are the address part 32. Priority information section 33
．． It is composed of a data section 34 and a free space flag 35. The address field 32 contains the register number (address).
The priority information section 33 stores, for example, about 4 bits of priority information added to the packet by the priority adding circuit 22. Further, the data section 34 stores the contents of a packet to be transmitted, and the free space flag 35 stores a 1-bit flag indicating whether a packet is stored in the register 311.

The packet discard device 13 is a circuit that receives an overflow signal from the packet input device 11, inputs the priority information of each packet in the storage device 12, and discards the packet with the lowest priority among these priority information. . For example, as shown in FIG. 3, this packet discarding device 13 includes a plurality of comparators 361, 362° .・・・
・.

37m, and a comparator 36j (j −
Based on the comparison results of the priority information of items 1 to m), the register number with the lower priority is sequentially selected in a tournament manner. As a result, the number of the register 311 storing the packet with the lowest priority is taken out from the highest selector 37m. The packet discard device 13 resets the free space flag of the register 311 specified by this number to "0".

When the second communication path 2 becomes communicable, the packet output device 14 inputs the priority information of each packet to the storage device 12, and outputs the packet with the highest priority among these priority information to the second communication path 2. This is a circuit that outputs data onto the communication path 2.

This packet output device 14 also has the above-mentioned packet discard device 13.
The packet discard device 13 has almost the same configuration as the packet discard device 13
The difference is that each selector 37j selects the register number of the packet with the highest priority, and that the priority information in the register selected after outputting the packet is given the lowest priority.

Next, the operation of the communication buffer device 3 having the above configuration will be explained.

When a packet to be transmitted via the first communication path 1 is input to the packet input device 11, a free space in the storage device 12 is searched based on the free space flag. If the free space flag is "0" and the register 311 is detected, the register number is specified as the address of the storage device 12, and the packet is stored in the data section 34 of the register 311. At this time, priority information is added to the packet by the priority adding circuit 22, and the information is stored in the priority information section 33 of the register 311.

On the other hand, the packet output device 14 controls the transmission of packets stored in the storage device 12 while monitoring the second communication path 2 . That is, if a congestion situation occurs where traffic on the second communication path 2 is concentrated, the transmission of packets to the second communication path 2 is interrupted, and while checking the availability of the second communication path 2, the packets with the highest priority are The packets with higher values are selected and sequentially output to the communication path 2 of the node 2.

When the congestion state of the second communication path 2 continues for a long time and the free space flags 35 of each register of the storage device 12 are all "1", that is, the storage device 12 is full, new When a packet is input to the packet input device 11, the packet input device 11 outputs an overflow signal to the packet discard device 13. In response to this, the packet discard device 13 selects the packet with the lowest priority and discards the packet by setting its free space flag to "0". As a result, the new packet is stored in the register 361 where the packet was discarded.

In this way, according to the communication buffer device 3 of this embodiment,
Since the storage area of the storage device 12 is unrelated to the priority of the packet, the storage area can be used effectively.

Furthermore, in this embodiment, a comparator 36j and a selector 37j configured in a tree shape are used in the packet discard device 13 and the packet output device 14, and packets with the lowest priority or the highest priority are processed in a hardware-based batch tournament system. Since the search is performed using , the discard process and the output process can be performed in a shorter time than the time required to transfer the packet. Therefore, even if packets are continuously input to the packet input device 11,
By quickly discarding packets from the storage device 12, new packets can be accumulated in the storage device 12 one after another.
Likewise, even when packets are read from the storage device 12 and successively sent to the second communication path 2, no idle time occurs between packets.

Note that the present invention is not limited to the above embodiments. In the above embodiment, the speed of the packet discard device 13 and the packet output device 14 is increased by a batch comparison method using a comparator, but in a system where the speed of discard processing and output processing is not a big issue, software Processing may be performed using a method.

Further, the storage means for storing packets is not particularly limited to a random access memory, but may be a sequential memory. In this case, sequential selection of output packets or discarded packets will be performed.

Furthermore, in the above embodiment, information indicating the priority of the packet is added at the time of inputting the packet, but this priority may be assigned to the packet data itself or managed within the storage device. You may keep it as information. For example, FIG. 4 is a diagram showing an example in which the order of packet accumulation is used as the priority information. Each register 421, 422, -. Counting units 431, 432, . . . , 43n are added to 42n, respectively.

After the packet is stored in the register 421, the counting unit 431 (i-1 to n) calculates, for example, the packet output device 1.
Each time the output operation in step 4 is performed, a count-up operation is performed, and it is reset when a packet is output. Thereby, the count value of the counting unit 431 indicates the input order of the packets. Therefore, using this as priority information,
For example, priority control can be performed such as outputting old packets first and discarding new packets. Note that the counting operation of the counting unit 431 may be performed each time a packet is discarded, or may be performed each time a packet is discarded and outputted.

Alternatively, discard priority and output priority (urgency information) as priority information may be distinguished and determined separately.

The criteria for packets to be discarded can also be determined as follows.

■ The packet with the longest buffer accumulation time among the group of packets with the highest discard priority.

■ The packet with the shortest buffer accumulation time among the group of packets with the highest discard priority.

■ All packets in the group of packets with the highest drop priority.

(2) Among packets in the states (1) to (2) above, the packet discard priority is determined based on the packet type (content).

Furthermore, among the group of packets with the highest output priority, the packet with the longest buffer storage time may be used as the reference for the packet to be output.

Furthermore, when the packet output means is composed of a packet selection means and an output packet sending means, these can be arranged side by side and operated in a pipeline. In this case, the output packet selection means is activated in anticipation of the selection time so that the selection of the packet is completed by the expected time when the packet can be delivered to the output packet transmission means. Increases speed.

[Effects of the Invention] As described above, according to the present invention, if there is a free area in the storage means, packets are unconditionally accumulated in that area irrespective of the priority. The storage area can be used effectively without creating any wasted free space. Therefore, effective packet priority control can be achieved with a small buffer capacity.

[Brief explanation of the drawing]

Fig. 1 is a block diagram of a communication buffer device according to an embodiment of the present invention, Fig. 2 is a block diagram of a packet input device in the same device, and Fig. 3 shows a part of the storage device and packet discard device in the same device. FIG. 4 is a block diagram of a storage device in a communication buffer device according to another embodiment of the present invention, and FIG. 5 is a block diagram of a communication buffer device using a conventional priority control method. 1.51...First communication path, 2,52...Second communication path, 3...Communication buffer device, 11...Packet input device, 12...Storage device, 13... -Packet discard device, 14...Packet output device. Applicant's agent Patent attorney Takehiko Suzue Figure 4 Figure 5 Procedural amendment December 28, 1988 1, Indication of the case Patent application No. 1983-64056 2, Name of the invention Communication buffer device 3, Person making the amendment Relationship to the incident Patent applicant (307) Toshiba Corporation

Claims (3)

[Claims] (1) a storage means for storing information packets, a packet input means for inputting information packets to be transmitted, detecting an empty area of the storage means, and storing the inputted information packets in the empty area; packet discarding means for selecting and discarding information packets to be discarded from the storage means based on the priority of each information packet stored in the storage means; 2. A communication buffer device comprising: packet output means for selecting and outputting information packets to be output from said storage means. (2) The packet discarding means selects and discards the information packets stored in the storage device in a time shorter than the time required to transfer the information packets on the communication path, and the packet outputting means 2. The communication buffer device according to claim 1, wherein the information packets stored in the storage device are selected and outputted in a time shorter than the time required to transfer the information packets on a communication path. (3) The storage means is provided with a plurality of registers for storing each information packet, and is provided corresponding to each of these registers, and while the information packet is stored in the corresponding register, the information generated by the packet discarding means is and counting means that performs an increment operation each time a packet is discarded and/or an information packet is output by the packet output means, and the priority of the packet is determined based on the counted value of the counting means. The communication buffer device according to claim 1, wherein the communication buffer device is determined.