JP3472466B2 - Frame relay subscriber concentrator - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a frame relay subscriber line concentrator for concentrating a low speed line from a subscriber side and transferring it to a frame relay exchange.

In a frame relay subscriber concentrator, frame data from a plurality of subscriber lines are temporarily stored in individual buffers and transferred to one transmission buffer for multiplexing. A large amount of data may be generated depending on the subscribers of the frame relay, burst frames may be transmitted, and it may be difficult to cope with the buffer, which may affect other subscribers. .

[0003]

2. Description of the Related Art FIG. 12 shows a system configuration of a frame relay, 80 is a frame relay switch, 81 is a frame relay subscriber concentrator for multiplexing and separating a large number of low speed subscribers, and 82 to 84 are frame relay subscribers. Concentrator 81
82 is a frame relay exchange 8
A demultiplexing control device (TDCTL) for multiplexing and demultiplexing a frame with 0, a shared memory 83 for supplying a buffer used in the demultiplexing / demultiplexing, and a 84 for multiplexing and demultiplexing a frame with a subscriber side device. Demultiplexing control device (TDCTL), 85 is a multiple subscriber line terminal device (C
T) and 86 are remote subscriber line terminal units (R) equipped with a large number of network terminating units (OCU) provided corresponding to respective subscribers.
T), 87 is a subscriber data termination unit (DSU), and 88 is a subscriber terminal.

The frame relay has a flag (01111110),
Address part (data link connection identifier DLC
I, forward explicit congestion notification bit FECN, backward explicit congestion notification bit BECN, discardable indication bit DE,
Address field extension bit EA), variable length user data, frame check sequence FCS and flag.

Each subscriber terminal 88 generates a frame at a low speed (reserved speed) and a length different from time to time and transmits the frame. The upstream frame is transmitted from the subscriber data terminating device (DSU) 87 through a line. In the remote subscriber line terminal equipment (RT) 86, the frames of a large number of subscribers are multiplexed and sent to the multiple subscriber line terminal equipment (CT) 85,
Further, it is input from the multi-subscriber line terminal device (CT) 85 to the frame relay subscriber line concentrator 81. In the demultiplexing control device (TDCTL) 84 therein, each subscriber side receiving buffer that separates into frame data for each subscriber line and uses the shared memory 83 individually prepared for each subscriber side line (Shown in FIG. 13 described later). Each subscriber reception buffer is further provided with a demultiplexing controller 82.
In the above, the shared buffer 83 is moved to a transmission buffer (shown in FIG. 13 which will be described later) using the shared buffer 83, and transferred from there to the frame relay exchange 80.

On the contrary, when the downstream multiplexed frame output from the frame relay switch 80 to the frame relay subscriber concentrator 81 is received by the switch side reception buffer (not shown) of the demultiplexing control device 82, it is demultiplexed. It is stored in a subscriber-side transmission buffer (not shown) corresponding to the subscriber of the demultiplexing control device 84, and then reaches the subscriber terminal 88 by following a route opposite to that of the upstream frame.

In the frame relay subscriber concentrator using the above shared memory, when a burst frame (frame in which the amount of data suddenly increases) is generated by the subscriber, the buffer becomes insufficient. Details of the operation in that case will be described with reference to FIG. The shared memory is divided and used by a fixed-length buffer, and the shared memory is called a common buffer.

FIG. 13 is an explanatory view of a conventional operation using a common buffer, and shows a case where the upstream frames from the subscriber side to the frame relay exchange are concentrated. In the figure, reference numeral 90 denotes burst frame transmission from a plurality of subscribers # 0 to # 2, and the multi-subscriber line terminal equipment C of FIG.
It is input from the T side. Reference numeral 91 is a subscriber side reception buffer, which is provided corresponding to each subscriber # 0 to # 2, and a predetermined buffer (empty buffer) corresponding to each subscriber is allocated from the common buffer. Reference numeral 92 is a common buffer, and 93 is an exchange side transmission buffer, which multiplexes the data of a plurality of subscriber side reception buffers. Also, 80
Represents a frame relay switch like the above 12.

To explain the normal operation, the frame from the subscriber is a receiving buffer on the subscriber side which is composed of a predetermined number of buffers (unit buffers of a fixed length) corresponding to the subscribers supplemented from the common buffer 92. Stored in 91,
The received buffer is sequentially moved (switched) to the exchange side transmission buffer 93. The contents of the exchange side transmission buffer 93 are the same as those of the frame relay exchange 80.
However, when sequentially transferred to the frame relay switch 80, the transferred buffers become empty buffers and are sequentially replenished (released) in the common buffer 92. In this way, the common buffer 92 is repeatedly released from the exchange side transmission buffer and replenished to the subscriber side reception buffer.

When a burst frame is temporarily transmitted from the subscriber # 0 during the normal operation, the subscriber side reception buffer 90 of the # 0 is switched to the exchange side transmission buffer 93.
By giving the highest priority to the process of connecting to, the common buffer 92 could absorb it. However, when the terminal of the subscriber # 0 continuously outputs the burst frame, the buffer allocated from the common buffer to the subscriber side reception buffer 91 of the subscriber # 0 is exhausted and the reception buffer cannot be replenished. The subscriber-side receiving buffer 91 overflows and cannot receive a frame from the subscriber.

[0011]

As described above, when burst frames from a subscriber continue to occur, not only the subscriber-side receiving buffer for that subscriber overflows, but also the common buffer is used for all lines. Since they are shared, the subscriber side reception buffer 91 of normal subscribers (subscribers # 1 and # 2 in FIG. 13) who are not sending burst frames cannot be refilled with a normal buffer. This will affect the subscribers and significantly degrade the communication quality of the frame relay subscriber concentrator. It should be noted that such a burst frame results in a large number of unnecessary buffers (buffers including an empty area in the buffer) being allocated due to the occurrence of a large number of frames (called short frames) shorter than the buffer length that is the unit of allocation. It often occurs.

In this way, when burst traffic communication such as short frames increases, communication other than burst traffic is affected and normal communication (communication within a predetermined traffic volume) is performed. There is a problem that the communication quality of the subscriber is deteriorated.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a frame relay subscriber concentrator capable of maintaining the communication quality of a subscriber who is performing normal communication even if a subscriber whose burst traffic communication such as a short frame increases will occur. And

[0014]

FIG. 1 is a diagram for explaining the principle of reception stop control according to the present invention, and FIG. 2 is a diagram for explaining the principle of reception restart control according to the present invention. 1 and 2 show only the main configuration for concentrating the upstream frames from the subscribers inside the frame relay subscriber concentrator to the exchange, and the demultiplexing control devices on the subscriber side and the exchange side ( TDCTL) and the structure for transmission from the exchange to the subscriber in the reverse direction (downstream) are omitted.

In FIGS. 1 and 2, 1 is a subscriber (# 0 to # 2) of the frame relay service, 2 is provided corresponding to each subscriber's line, and a frame from each subscriber is temporarily provided. Subscriber side individual receive buffers (# 0- #)
2) and 2a are provided for the respective reception buffers 2 and are provided with a plurality of individual buffer management means for managing the individual reception buffers 2, and 3 is a plurality of reception buffers 2 for storing the frames from each subscriber. Transmission buffer for converting the data into a frame relay switch, and 4 for each reception buffer 2
, A common buffer for supplying a free buffer to hold the buffer that has been transmitted in the transmission buffer 3 as a free buffer, 4a for managing a common buffer for supplementing the reception buffer with the free buffer, 5
Is connected to the individual reception buffer management means 2a and the common buffer management means 4a, and performs frame reception from subscribers, allocation of buffers from the common buffer to individual reception buffers 2, control of movement to the transmission buffer, and the like. Control unit,
6 is a frame relay exchange.

In FIG. 1, a subscriber side reception buffer (hereinafter, simply referred to as a reception buffer) 2 receives a frame from the subscriber 1 and a unit buffer having a fixed length from a common buffer 4 (circle in the figure is empty, ●). (Shown as received / sent unbuffered in) is allocated in number corresponding to the subscriber,
The frames received by the respective reception buffers 2 are serially arranged in the exchange side transmission buffer 3 and multiplexed, and when transmitted to the exchange 6 of the frame relay, the control is released to the common buffer 4 as an empty buffer. Do in 5.

When a burst frame is generated from the subscriber # 0, which is one of the subscribers 1, the data accumulated in the corresponding reception buffer 2 of # 0 is increased and the free space of the buffer is reduced. The buffer requests the control unit 5 to replenish the empty buffer, and the control unit 5 allocates the empty buffer from the common buffer 4 to the reception buffer 2. On the other hand, each individual buffer management means 2a determines whether or not the free buffer (unit buffer) of each reception buffer 2 becomes smaller than the preset insufficient threshold value during the reception operation. As shown in FIG. 1, the reception buffer 2 of the subscriber 1 of # 0 increases the number of buffers in the received / untransmitted state due to the occurrence of the burst frame, decreases the free buffer, and the individual buffer management means 2a uses the above-mentioned method. When it is detected that the amount is less than the insufficient threshold value, the control unit 5 is notified. At this time, when it is detected from the common buffer 4 that the free buffer has become less than the set threshold value and the control unit 5 is notified, the control unit 5 performs control to stop reception in the corresponding # 0 reception buffer 2. To do.

After the reception is stopped in this way, the common buffer management means 4a in FIG. 2 determines whether the number of free buffers in the common buffer 4 exceeds the preset normal threshold value, and it can be seen that the number has increased. Notify the control unit 5.
In response to this, the control unit 5 controls to restart the reception of the line whose reception is stopped. That is, while the reception of the frame from the subscriber of # 0 in FIG. 2 is stopped, the empty buffer is not replenished from the common buffer 4 to the reception buffer of # 0, while the received buffer of the reception buffer 2 of # 0 is Since it is transferred to the send buffer, the free buffer of the common buffer 4 increases, exceeds the normal threshold, and reception is stopped.
Reception of frames from 0 subscribers is resumed.

Therefore, while the input of the burst traffic communication such as the short frame is stopped, the abnormal buffer is not replenished to the receiving buffer, so that the capacity of the common buffer increases and other normal joining is performed. It becomes possible to replenish the receiving buffer of the user with an empty buffer, and if the number of empty buffers of the common buffer exceeds the threshold value, the reception can be resumed even for the reception stop line.

In the above, the condition for stopping the reception is that the free space in both the reception buffer and the common buffer is small, but the reception may be stopped only when the free space in the reception buffer is equal to or less than the set threshold value. Good. Further, one of the conditions for stopping the reception described above is that there is no free buffer in the common buffer, but this can be set to be less than a certain threshold value.

[0021]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 3 shows the hardware configuration of the embodiment. In the figure, 10 is a frame relay subscriber concentrator,
11 is a CPU that controls by a program, 12a is a frame control memory storing a frame control program,
12b is a line number memory, 13 is a demultiplexing control device (T
DCTL, the same as 84 in FIG. 12), 14 is a receiving buffer, 15 is a switch unit, 16 is a common buffer, 17 is a transmitting buffer, and 18 is a demultiplexing control device (TDCT).
L) and 19 are multi-subscriber line terminal equipment (CT, FIG. 12 above).
Same as 85). It should be noted that FIG. 3 shows only the configuration for concentrating the upstream frames and omits the configuration for transmitting the downstream frames to the subscriber side (shown in FIG. 5 described later).

To explain the function of each main part of FIG. 3, the receiving buffer 14 has a predetermined number of buffers (unit buffers) individually provided for each line in order to secure the minimum buffer amount for the upstream frame for each line. In response to a burst-like inflow of frames from the subscriber side, the frames are temporarily accumulated and fluctuations are absorbed, and the transmission buffer 17 multiplexes the data from the reception buffer 14 and sends the frame data to the exchange side. Used for. The common buffer 16 replenishes an empty buffer so that the reception buffer has a predetermined number when the buffer is moved from the reception buffer 14 to the transmission buffer 17. The multi-subscriber line terminal equipment (CT) 19 generates a multiplexed frame (60 subscriber lines of 00 to 59 are multiplexed), and the demultiplexing control device (TDCTL) of the frame relay subscriber line concentrator 10 is generated. 1
3 separates the multiplexed frame for 60 subscriber lines into frame data for each subscriber line, and transfers the frame data to the reception buffer 14 prepared for each subscriber side line.
The frame control program memory 12a receives a frame from the demultiplexing device (TDCTL) 13, demultiplexes it for each line and transfers it to the reception buffer 14, and then demultiplexes the data in the transmission buffer 17 to the demultiplexing control device (TDCTL) 18 Specifies the procedure for multiplexing and transmitting to the frame relay exchange. Further, the line number memory 12b holds the line number when the reception buffer on the subscriber line side due to the burst frame reaches the shortage threshold and the reception is stopped.

In a normal operation, the demultiplexing control unit (TDCTL) 13 transfers the multiplex frame from the subscriber side to the receiving buffer 14 for each subscriber line, and the CPU 1
1 controls according to the procedure instructed to the frame control program memory 12a. For example, when the frame data is transferred to one reception buffer, for example, the reception buffer corresponding to the subscriber line 00 in the reception buffer 14, the CPU retrieves the individual reception buffer for one frame, and at the same time, the common buffer. The empty buffer pooled in the buffer is replenished to the reception buffer of the subscriber line 00, and the extracted reception buffer is one line in the transmission buffer 17 to the designated exchange side corresponding to the destination. (For example, number 00) is moved via the switch unit 15 to activate transmission. After that, the demultiplexing control device (TDCTL) 18 multiplexes the frame data of the transmission buffer 17 on the exchange side and sends it to the frame relay exchange side. When the transmission buffer 17 becomes already transmitted, the transmission buffer is taken out, Control to move to the common buffer.

FIG. 4 is a process flow of frame reception having the reception stop function of the first embodiment. Is the processing flow,
B. Shows the structure of the line number memory. A. In the process flow, when the frame relay subscriber concentrator receives the frame, the demultiplexing controller (TDCTL) reads the frame and detects the receiving line (S1 in FIG. 4). At this time, the frame is transferred to the individual receiving buffer corresponding to the line.
Processing for MA transfer is performed. Next, the number of common buffers (the number of free unit buffers of a fixed length) is determined (S in FIG. 4).
2) If not present, the process is terminated, and if present, the reception buffer is taken out and put into the transmission buffer (at step S3), and the common buffer is taken out and placed at the reception buffer (at step S4).
Here, it is determined whether the reception buffer has overflowed (whether the number of buffers that have been received / not transmitted has exceeded a certain allocation number) (at step S5). Previous S1
Up to S5 is a normal reception function, and when it is detected that an overflow has occurred, reception stop control by the following S6 to S8 is started, and if no overflow occurs,
Normal processing is executed. In case of overflow,
It is determined whether the number of common buffers has decreased (whether there are no free buffers or a certain threshold or less) (at step S6). If the number does not decrease, normal processing is performed. If the number decreases, the memory transfer from the demultiplexing control device (DCTL) to the individual reception buffer corresponding to the line is stopped (at step S7) and the line number is saved ( Same S8). The line number is as shown in FIG. As shown in, the position of the line number memory is indicated by the pointer, and the position of 0 to 59 can be designated. In the example of the figure, the position of each pointer is 0, 1 ...
The case where the line numbers for which reception of "0", "line number 26" ...

FIG. 5 is a processing flow of frame transmission including the reception restart function of the first embodiment. The line whose reception is stopped by the processing of FIG. 4 can be restarted by this processing flow. In FIG. 5, the demultiplexing control device (TD
CTL: 18 in FIG. 3 reads the transmission buffer (the contents are transferred to the frame relay exchange), and the transmission completion line (FIG. 3)
When one of the transmission buffers 17 in FIG.
1), the transmission buffer is taken out and put in the common buffer (at step S2). Next, it is determined whether the common buffer has increased (exceeds the normal threshold value), and if it has increased, the head of the storage line number stored in S8 of FIG. 3 is extracted (S of FIG. 5).
4), restarting the reception of the line for which the reception is stopped (Same S
5), determine whether the processing has been completed for all the saved line numbers, and if there are remaining numbers, restart reception in order,
Perform normal processing. If it is determined in S3 that the number of common buffers has not increased, normal processing is performed without restarting reception. It should be noted that the above-mentioned resumption of reception is to restart the DMA transfer of the reception frame by the demultiplexing control device (TDCTL) 13 to the reception buffer 14.

FIG. 6 is a processing flow of frame reception according to the second embodiment. In the second embodiment, the function of restarting the reception, which is performed by monitoring the state of the common buffer in the frame transmission processing (see FIG. 5) of the first embodiment, is changed to the reception buffer state in the frame reception processing. It is designed to be monitored.

6, in S1 to S4 at the time of frame reception, the same normal function processing as in S1 to S4 in FIG. 4 is performed. Due to S3 (moving the receiving buffer to the transmitting buffer) and S4 (replenishing the receiving buffer with the common buffer), the reception-completed buffer on the subscriber side that has stopped receiving is moved to the transmitting buffer, and the common buffer becomes the receiving buffer. On the other hand, since the memory transfer (DMA) to the receiving buffer is stopped in the receiving line, all the receiving buffer becomes empty. In this state, in S5 of FIG. 6, it is determined whether the reception buffers of the line concerned are all free (all free buffers). Here, if it is found that all the lines are free, if the line is stored in the line number memory (12b in FIG. 3), the process of restarting reception of this line is performed (S in FIG. 6).
6). If not empty, S5 of FIG. 4 of the first embodiment
-Processing including a reception stop function similar to S8 (S8-
S10) is performed.

FIG. 7 is a processing flow of frame reception according to the third embodiment. Is a processing flow, and B. Is a timer management table used in the third embodiment. In the third embodiment, when the memory transfer is stopped (reception is stopped) in the frame receiving process, a timer having a preset fixed time is activated for each reception line, and the timer of the line whose reception is stopped is timed out after the fixed time. Then, control is performed so that reception of the stopped receiving line received by the line number corresponding to the timer that has timed out is restarted.

In FIG. 7, each processing of S1 to S8 is S1 of the processing flow (FIG. 4) of the frame reception of the first embodiment.
~ S7, but in the third embodiment, the receive buffer overflows (S5 in A. of Fig. 7), the common buffer decrease is detected (S6), and the memory transfer to the receive buffer is stopped. (At step S7), the line number is saved (at step S8). Then, the timer is started (S9 of A. in FIG. 7).

In this case, as shown in FIG. The timer management table with the structure shown in is used, and the line number is set as an accessory parameter of the timer. This timer is processed by a software timer process (generally used queue management process).

FIG. 8 is a processing flow for restarting reception in the third embodiment. After the timer is started by the processing of FIG. 7 described above, if a preset time elapses and a time-out occurs, the corresponding line number is acquired from the timer management table and the memory transfer is restarted.

FIG. 9 is a processing flow of frame reception according to the fourth embodiment. In the fourth embodiment, the burst frame monitoring function is realized by monitoring the use of a fixed number of receiving buffers within a fixed time set for each receiving buffer on the subscriber side.

In S1 to S4 at the time of frame reception in FIG. 9, the same normal function processing as S1 to S4 in FIG. 4 (Embodiment 1) is performed. After this, it is determined whether a fixed time has passed (S5 in FIG. 9). When the fixed time has not elapsed, the number of used reception buffers is incremented by 1 (S6 in FIG. 9), and when the time has elapsed, the number of used reception buffers is initialized (set to 1) (step S6
7). After this, it is judged whether the number of received buffers used is large (larger than a preset number) (S8 in FIG. 9), and if the number of used buffers is large, the memory transfer to the receive buffer is stopped (S8).
9), the receiving line number is stored in the line number memory (12 in FIG. 3).
It is stored in b) (at step S10). If the number of receive buffers used is not large, normal processing is performed.

The function of resuming the reception of the line whose reception is stopped in this way can be performed by the above-mentioned FIG. 5 (frame transmitting process of the first embodiment) or FIG. 6 (frame receiving process of the second embodiment).

In each of the above-described first to fourth embodiments, the demultiplexing control device (T
Although it is performed by stopping the memory transfer from the DCTL) to the reception buffer, it can also be realized by stopping the movement from the reception buffer to the transmission buffer.

10 and 11 are explanatory views (No. 1) and (No. 2) of the configuration and operation of the entire apparatus according to the present invention. 10 and 11 are connected by lines (1) to (3) to form a frame relay subscriber concentrator as a whole. Figure 10
3, 11, 12a, 12b, 13, 14, 16 correspond to the respective symbols in FIG. 3, 11 is a CPU, 12a is a frame control memory storing a frame control program,
Reference numeral 12b is a line number memory, 13 is a demultiplexing control device (TDCTL) for receiving transmission frames from a plurality of subscribers (24 in FIG. 11, which will be described later), and 14 is a reception buffer (# 0 to # 59) on the subscriber side. , 16 are reception buffers 14 on the subscriber side for receiving the frames transmitted from the subscriber side.
And a common buffer for supplying an empty buffer to the reception buffer 22 on the exchange side for receiving a frame from the exchange side, 17 is a transmission buffer (# 0 to # 4) on the exchange side for transmitting a frame to the exchange, 18 Is a demultiplexing control device (TDCT) that multiplexes and transmits frames to the exchange side.
L). The switch unit 15 shown in FIG. 3 is not shown.

In FIG. 11, reference numeral 20 is an exchange (frame relay exchange), 21 is a demultiplexing control unit (TDCTL) for separating the frames from the exchange, and 22 is the same structure as a buffer for sequentially storing the frames from the exchange. Reception queues (# 0 to # 4), 23 are transmission buffers (# 0 to # 59) on the subscriber side for storing the frames moved from the reception queue 22 individually for each subscriber, and 24 is a plurality of subscribers. A demultiplexing control device (TDCTL) that multiplexes and transmits the frames of the transmission buffer 23 of each subscriber toward
25 represents a plurality of subscribers.

The demultiplexing control device (TDCTL) 13 transfers the multiplexed frame from the subscriber 25 side to the receiving buffer 14 for each subscriber, and the receiving buffer 14
Is moved to the transmission buffer 17, and the demultiplexing control device (T
DCTL) 18 transmits to the exchange side after multiplexing.
The transmitted buffer is released, put into the common buffer 16, and supplied to the receiving buffer 14. CPU11 is
By any of the processes shown in the above-described first to fourth embodiments, the number of received buffers or the number of free buffers in each reception buffer 14 is monitored, the number of free common buffers is monitored, or a burst is generated by a process using a timer. When a frame is detected, reception is stopped for that line, and reception restart control is performed if the conditions for reception restart are met.

On the other hand, the multiplexed frame from the exchange 20 is demultiplexed by the demultiplexing control device (TDCTL) 21 and transferred to the plurality of reception queues 22 in the memory. In this case, since the frame from the exchange 20 is output via the exchange, burst frames are suppressed, so that the reception queue 22 is received without overflow due to the steady acquisition of a free buffer from the common buffer 16. It The frames in the receive queue 22 are moved to the individual transmit buffers 23 on the subscriber side, and then the demultiplexing controller (T
The frame of each transmission buffer 23 is multiplexed by the DCTL) 24 and transmitted to the subscriber side.

[0040]

According to the present invention, when a receive buffer overflows, the memory transfer to the receive buffer is stopped for a line that carries out burst traffic communication such as a short frame. By increasing the number, it becomes possible to capture the common buffer from other lines and prevent the influence on other lines. As a result, the traffic inside the line interface can be suppressed, and the communication quality of the subscriber who performs normal traffic communication can be maintained.

[Brief description of drawings]

FIG. 1 is a diagram illustrating the principle of reception stop control according to the present invention.

FIG. 2 is a diagram illustrating the principle of reception restart control according to the present invention.

FIG. 3 is a diagram showing a hardware configuration of an embodiment.

FIG. 4 is a diagram illustrating a processing flow of frame reception having a reception stop function according to the first embodiment.

FIG. 5 is a diagram illustrating a processing flow of frame transmission including a reception restart function according to the first embodiment.

FIG. 6 is a diagram illustrating a processing flow of frame reception according to the second embodiment.

FIG. 7 is a diagram illustrating a processing flow of frame reception according to the third embodiment.

FIG. 8 is a diagram showing a processing flow for restarting reception according to the third embodiment.

FIG. 9 is a diagram illustrating a processing flow of frame reception according to the fourth embodiment.

FIG. 10 is an explanatory diagram (part 1) of the configuration and operation of the entire device according to the present invention.

FIG. 11 is an explanatory diagram (part 2) of the overall configuration and operation of the device according to the present invention.

FIG. 12 is a diagram showing a system configuration of a frame relay.

FIG. 13 is a diagram illustrating a conventional operation using a common buffer.

[Explanation of symbols]

1 subscribers (# 0 to # 2) 2 Receive buffer (# 0 to # 2) 2a Individual buffer management means 3 Send buffer 4 common buffer 4a Common buffer management means 5 control unit 6 exchanges

─────────────────────────────────────────────────── ─── Continuation of the front page (72) Koichiro Fukumoto, Inventor 4-1-1 Kamiotanaka, Nakahara-ku, Kawasaki-shi, Kanagawa Fujitsu Limited (72) Inventor Mitsunori Takahashi 4-chome, Ueodaanaka, Nakahara-ku, Kawasaki-shi, Kanagawa 1-1 In Fujitsu Limited (72) Inventor Shuichi Kuniyoshi 4-1-1 Kamiodanaka, Nakahara-ku, Kawasaki-shi, Kanagawa Fujitsu Limited (72) Inventor Abe Shin 3-19 Nishi-Shinjuku, Shinjuku-ku, Tokyo No. 2 Nihon Telegraph and Telephone Corporation (56) Reference JP 63-209347 (JP, A) JP 9-261238 (JP, A) JP 1-286548 (JP, A) JP 57-87261 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) H04L 12/56 H04Q 3/60

Claims (4)

(57) [Claims] 1. A frame buffer provided between a plurality of frame relay subscribers and a frame relay exchange, wherein a common buffer is used to temporarily store frames received from a plurality of subscriber lines and the frame relay exchange in a buffer. In a frame relay exchange and a frame relay subscriber concentrator for sending to a subscriber respectively, individual buffer management means for managing a reception buffer provided for each line of a plurality of subscribers, and a buffer for supplying a buffer to the reception buffer A common buffer management unit that manages a common buffer to which the buffer is replenished from, and the control unit,
When the common buffer management means detects that the number of free spaces in the common buffer is less than or equal to a predetermined threshold value, and the individual buffer management means detects that the number of free spaces in the reception buffer is less than or equal to a predetermined threshold value. , The reception of only the line corresponding to the reception buffer is stopped, and when the common buffer management means detects that the number of free spaces in the common buffer is equal to or more than a preset threshold value, the reception of the line of which the reception is stopped is restarted. A frame relay subscriber line concentrator characterized by the above. 2. The control unit according to claim 1, when the control unit detects that all the reception buffers managed by the individual buffer management unit are empty, restarts reception on a line accommodating a subscriber of the reception buffer. Frame relay subscriber concentrator characterized by. 3. The frame relay subscriber concentrator according to claim 1, wherein the control unit restarts reception for a line accommodating the subscriber whose reception is stopped after a lapse of a certain time after the reception is stopped. . 4. The control unit according to claim 2 or 3, wherein when the control unit detects that the usage amount of the reception buffer managed by the individual buffer management unit within a predetermined time exceeds a predetermined threshold value, A frame relay subscriber concentrator, wherein reception is stopped only on a line accommodating the subscriber.