JP3296040B2 - Frame exchange - 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 exchange for exchanging a frame composed of a frame header and frame data.

In recent years, in order to efficiently communicate data, a frame network including a plurality of frame switches and transmission lines connecting the frame switches has been constructed. In this frame network, data output from a terminal is divided into data transmission units called frames, and each frame is added with frame management data called a frame header and transmitted to the network. The frame switch identifies the destination of the frame from the information of the frame header added to each frame, and sends the frame to the designated transmission path.

[0003] In such a frame network, a frame switch capable of efficiently coping with congestion is required.

[0004]

2. Description of the Related Art FIG. 11 is a block diagram for explaining a conventional example (1). In the figure, 100 is a frame exchange, 11 is a reception buffer, 12 is a congestion detection unit, 15 is a frame discard processing unit, 21 is a transmission buffer, 30 is a frame switch,
200 is a transmission path.

In the configuration shown in the figure, data received from a terminal (not shown) is temporarily stored in a reception buffer 11.
The congestion detection unit 12 constantly monitors the amount of data stored in the reception buffer 11, and when the amount of data stored in the reception buffer 11 exceeds a predetermined value, the congestion state is determined, and the congestion state is determined by the protocol of the frame relay communication. FECN (Forwar
d Explicit Congestion Notification), BECN (Ba
The congestion notification bit of ckward Explicit Congestion Notification) is set to “ON” to notify the source terminal and the destination terminal of the congestion state and limit the transmission data. Also,
In some cases, the frame switching apparatus 100 avoids congestion by discarding a part of the frames accumulated in the reception buffer 11 by the frame discard processing unit 15.

FIG. 12 is a block diagram illustrating a conventional example (2). In the figure, 100 is a frame exchange, 11 is a reception buffer, 13 is a data compression unit, 21 is a transmission buffer,
22 is a data restoration unit, 30 is a frame switch, 200
Is a transmission path.

In the configuration shown in the figure, data received from a terminal (not shown) is temporarily stored in a reception buffer 11.
The received data output from the receiving buffer 11 is all compressed by the data
, And sends out to the designated transmission line 200,
All frames transmitted from the frame switch 30 to the terminal are restored by the data restoration unit 22.

[0008]

In the above conventional example (1), when the data amount exceeds a specified value, the data discard processing unit 1
5, the frame is discarded, and necessary data may be discarded.

Further, in the above-mentioned conventional example (2), a configuration is adopted in which all data from the terminal is compressed, the hardware amount of the data compression unit 13 and the data restoration unit 22 increases, and the cost as a system increases. growing. Further, if data compression / decompression of all frames is performed, a processing delay occurs, and a delay time between terminals increases.

An object of the present invention is to realize a frame switch for a frame network which does not discard frames even if the data amount increases and can minimize the delay time.

[0011]

FIG. 1 is a block diagram for explaining the principle of the present invention. In the figure, reference numeral 100 denotes a frame exchange, and 200 denotes a transmission line 200 for connecting the frame exchanges 100 to each other.

Reference numeral 11 in the frame switch 100 is a reception buffer for temporarily storing received data received from a terminal (not shown), 21 is a transmission buffer for temporarily storing data transmitted to the terminal, and 30 is a frame buffer. This is a frame switch that performs switching to a destination specified by a header.

Further, the congestion detection unit 12 and the data compression unit 1
3. The data restoring unit 22 is a congestion switch 100 according to the present invention.
The congestion detection unit 12 detects that the amount of data received from the terminal has exceeded a predetermined amount, and the data compression unit 13 uses the congestion detection unit 12 to reduce the amount of received data to a predetermined amount. When it detects that it has exceeded, compresses the frame data and starts compression before the frame where compression started
The transmission frame is inserted and transmitted.
The compression start frame is
If detected, decompress the compressed data frame.
The problem is solved by providing the means related to the frame exchange 100. .

[0014]

The frame network comprises a plurality of frame switches 100 and transmission lines 200 connecting the frame switches 100 to each other. The frame transmitted in this is composed of a frame header and frame data, the destination is identified from the contents of the frame header, and the frame switch 30 switches to the specified destination.

The frame transmitted from the terminal to the frame network is transmitted to the reception buffer 11 of the frame switch 100.
Is temporarily stored. The amount of data accumulated in the reception buffer 11 is compared with a threshold value for determining congestion in the congestion detection unit 12, and when it is determined that the data is congested, the data compression unit 1
3 together and compresses the frame data in, starting with compression
Is transmitted before the frame indicating the start of compression . On the other hand, the transmission data compression start transfer off of the terminal
Judgment of the presence or absence of a frame, and there is a compression start transmission frame
After that, the data restoring unit 22 restores the frame data of the subsequent frames .

Therefore, the frame can be efficiently transmitted by compressing the frame data only when congestion occurs.

[0017]

FIG. 2 shows an example of a compressed display flag according to an embodiment of the present invention. Here, the first two octets of the frame are the frame header (DLCI, Data Link Connection Identif).
ier), and the fourth and subsequent octets are frame data. The third octet is one octet inserted to indicate that compression has been performed. In this example, when bit 1 of the octet is “1”, the bit is compressed, and when bit 1 is “0”, the bit is uncompressed. is there.

FIG. 3 is a diagram for explaining an example of the congestion detecting section of the present invention. The figure shows a congestion detection unit 12 that detects congestion in the reception buffer 11, in which 12A is a read pointer, 12B is a write pointer, 12C is a set value register (shown as a set value in the figure), and 12D is It is a comparator.

In the configuration shown in the figure, frames received from a terminal (not shown) are stored in a reception buffer 11. At this time, the write pointer 12B indicates the last address of the stored frame. The frames stored in the reception buffer 11 are transferred by a frame switch (not shown) according to the address of the frame header. At this time, the read pointer 12A indicates the start address of the stored frame. The write pointer 12B and the read pointer 12
The difference A indicates the amount of frames stored in the reception buffer 11. The accumulated amount of the reception buffer 11 is calculated by the comparator 12
D constantly compares the set value with the set value of the set value register 12C.

When the number of frames received from the terminal temporarily increases and the amount of data stored in the reception buffer 11 exceeds a set value, the comparator 12D turns on the signal line to the data compressor to compress the frame data. Instruct to start. Receive buffer 1
When the accumulated amount of 1 decreases below the set value, the comparator 12D
Turns off the signal line to the data compressor (not shown) and instructs to stop the compression of the frame data. At this time, the set value of the compression start and the set value of the compression stop may be different values in order to provide the hysteresis characteristic.

FIG. 4 is a diagram for explaining an example of the data compression section of the present invention. 13A of the data compression unit 13 is a frame header detection unit, 13B is a frame data compression unit, 13C
Is a switch, 13D is a compression display flag adding unit, 13E, 1
3F is a buffer.

In the configuration shown in the figure, a frame received from a terminal (not shown) is input to a buffer 13E, separated into a frame header and frame data, and processed separately. First, the frame header is detected by the frame header detector 1.
3A and passed to the compressed display flag adding unit 13D. As described with reference to FIG.
Insert one octet and display it there.

When the signal from the congestion detection unit 12 is "OFF", the compression display flag addition unit 13D adds a flag "0" indicating non-compression to the header and writes the flag to the buffer 13F. At this time, the frame data is not passed through the frame data compressor 13B by the switch 13C, and
Handed over to 3F.

When the signal from the congestion detection unit 12 is turned "ON", the compression display flag addition unit 13D adds a flag "1" indicating compression to the header, and writes it to the buffer 13F.
The frame data is passed to the frame data compressor 13B by the switch 13C, and the data compression algorithm (for example, Zi
v Lempel method, which is a well-known technique and will not be described here).
After being written into F and reconstructed into a frame, it is transferred to a frame switch (not shown).

FIG. 5 is a diagram for explaining an example of the data restoration unit of the present invention. 22A in the data restoring unit 22 is a frame header detecting unit, 22B is a frame data restoring unit, 22C
Is a switch, 22D is a compressed display flag detection and removal unit, 22D
E and 22F are buffers.

In the configuration shown in the figure, a frame from a frame switch (not shown) is input to a buffer 22E, and a frame header and frame data are processed separately. First, the frame header is separated by the frame header detection unit 22A and passed to the compressed display flag detection and removal unit 22D.
The compressed display flag detection and removal unit 22D reads the value of the compressed display flag and removes one octet inserted between the frame header and the frame data.

When the value of the flag is "0", the frame data is passed to the buffer 22F without passing through the frame data restoration unit 22B by the switch 22C. When the flag is "1", the frame data is passed to the frame data restoration unit 22B by the switch 22C, restored in accordance with the data restoration algorithm, written into the buffer 22F, reconstructed into a frame, and then sent to a terminal (not shown). Will be transferred.

FIG. 6 is a block diagram for explaining an embodiment of the present invention. The configuration shown in the figure is such that the congestion detection unit 12, the data compression unit 13, and the data restoration unit 22 described in FIGS. 3 to 5 are provided on the transmission line 200 side of the frame switch 30. In the configuration shown in the figure, the congestion detection unit 12 measures the amount of data to be transmitted to the transmission line 200 and compares it with a specified value. When the data amount exceeds the specified value, the data is compressed by the data compression unit 13 and then transmitted, and when the data amount becomes smaller than the specified value, the data compression is stopped. Data compression unit 13
Then, when receiving a data compression instruction from the congestion detection unit 12,
According to the data compression algorithm, the data portion of the frame is compressed, the compressed data is written as frame data, and the compression display flag of the frame header is turned on. The data restoring unit 22 is connected to the transmission path 2
Monitor the frame header of the frame input from 00,
The frame data of the frame whose flag is “1” is restored according to the data restoration algorithm, and the restored data is written to the frame data section.

FIG. 7 is a block diagram for explaining another embodiment (1) of the present invention. The figure measures the amount of data to the transmission line 200, compares it with a specified value, and when the data amount exceeds the specified value, congestion occurs on the terminal that is the source of data passing through the link and the terminal that is receiving data. It is for a system that notifies the status. As described in the conventional example of FIG. 11, in frame relay communication, FECN, BEC
A protocol for performing the congestion notification is defined by the N bits. When the congestion notification detection unit 23 of the frame switch 100 at the network edge detects that the congestion notification bit is “1”, it issues a compression instruction for the data of the path to the data compression unit 13. The data compression unit 13 reads the frame header, reads the data part of the frame of the path, compresses the frame data, writes the compressed data in the frame data part, and sets the compression display flag of the frame header to “1”. Send it out vertically. The data decompression unit 22 monitors the compression display flag of the frame header, and when detecting a frame with the flag “1”, reads the data portion of the frame, decompresses the data, and writes the decompressed data to the data portion of the frame. .

The congestion detecting unit 12 is provided with a receiving buffer 11
The congestion notification sending unit 14 sends a congestion notification in the upstream direction when the data amount of the data is monitored and the congestion state is determined. FIG. 8 is a diagram for explaining another example of the data compression unit of the present invention. FIGS. 1, 6, and 7 show examples of performing the congestion notification using the congestion display flag. However, it is also possible to perform the congestion notification using the data compression unit 13 having the configuration shown in FIG. . In the figure, when a signal from a congestion detection unit (not shown) is turned "ON", a compression start / transmission frame creating unit 13G creates a compression start / transmission frame. On the other hand, the frame is input to the frame data compression section 13B via the buffer 13E by the switch 13C and compresses the frame data. The compression start transmission frame is inserted and transmitted before the frame that started compression.

When the signal from the congestion detection unit is turned off, the compression start / end transmission frame creating unit 13G creates a compression end / end transmission frame. The frame is directly transmitted without switching and compression by the switch 13C. At this time, the compression end transmission frame is inserted before the non-compression frame and transmitted.

FIG. 9 is a diagram for explaining another example of the data restoration unit of the present invention. The figure shows an example in which restoration is performed using a compression start / end transmission frame. In the figure, a frame from a frame switch is written into a buffer 22E, and a compression start / end frame detection unit 22G detects a compression start / end transmission frame. When the compression start frame is detected, the frame is input to the frame data restoration unit 22B by the switch 22C, decompressed, and output via the buffer 22F. Further, after the compression end frame is detected, there is no need to perform decompression, so that the data is switched by the switch 22C and output as it is.

FIG. 10 is a view for explaining another embodiment (2) of the present invention. 1 in the figure is a frame exchange 101-
A frame network 104 includes transmission lines 201 to 204, where R is a router, T1 to T3 are terminals, and NW is another network.

Each of the frame exchanges 101 to 104 in the figure is provided with a next link determination unit (not shown). When transmitting data from the terminal T1 accommodated in the frame exchange 101 to the terminal T3 accommodated in the frame exchange 103, when the congestion state is detected by the frame exchange 101, the frame data is compressed and transmitted to the frame exchange 102 through the link L1. Send out. In the frame switch 102, the next link determination unit determines whether there is a next link. In this case, since the next link L2 exists, the frame switch 102 does not restore the frame data, and sends the compressed data to the frame switch 103 as it is. Since the frame switch 103 is at the end of the link, it restores the frame data and transmits the frame to the terminal T3 via the router R and the network NW. When transmitting data to the terminal T2, the data is restored by the frame switch 102 and sent to the terminal T2.

[0035]

According to the present invention, a congestion detection unit for detecting congestion of transmission data is provided in a frame switch, and when a congestion state is detected,
While compressing the data portion of the frame, the frame is transmitted with a compressed display flag added. When the receiving side detects that the compressed display flag is added in the frame, the data portion of the frame is compressed. Perform a restore. If there is a next link, data is not restored at the frame switch in the middle of the path, but data is restored at the frame switch at the edge of the frame network, so that frames can be transmitted efficiently. Can be.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating the principle of the present invention.

FIG. 2 shows an example of a compressed display flag according to the embodiment of the present invention.

FIG. 3 is a diagram illustrating an example of a congestion detection unit according to the present invention.

FIG. 4 is a diagram illustrating an example of a data compression unit according to the present invention.

FIG. 5 is a diagram illustrating an example of a data restoration unit according to the present invention.

FIG. 6 is a block diagram illustrating an embodiment of the present invention.

FIG. 7 is a block diagram illustrating another embodiment (1) of the present invention.

FIG. 8 is a view for explaining another example of the data compression section of the present invention.

FIG. 9 is a view for explaining another example of the data restoration unit of the present invention.

FIG. 10 is a view for explaining another embodiment (2) of the present invention.

FIG. 11 is a block diagram illustrating a conventional example (1).

FIG. 12 is a block diagram illustrating a conventional example (2).

[Explanation of symbols]

 100, 101-104 Frame switch 11 Reception buffer 12 Congestion detector 12A Read pointer 12B Write pointer 12C Setting value register 12D Comparator 13 Data compressor 13A, 22A Frame header detector 13B Frame data compressor 13C, 22C Switch 13D compression Display flag adding unit 13E, 13F, 22E, 22F Buffer 13G Compression start / end transmission frame creation unit 14 Congestion notification sending unit 15 Frame discard processing unit 21 Transmission buffer 22 Data restoration unit 22B Frame data restoration unit 22D Compression display flag detection / removal unit 22G Compression start / end frame detection unit 23 Congestion notification detection unit 30 Frame switch 200, 201-204 Transmission line 1 Frame network L1, L2 Link T1, T2, T3 Terminal R Router N Network

Claims (1)

(57) [Claims] 1. A receiving device for temporarily storing received data from a terminal.
Transmission buffer and transmission to temporarily store transmission data to the terminal
Buffer and switch to the destination specified by the frame header.
And a frame switch that performs switching.
For exchanging frames consisting of header and frame data.
Detected that the amount of input data from the terminal exceeded a predetermined amount at the frame exchange
The input data amount exceeds a predetermined amount.
Frame data is compressed when the
When it is detected that the data amount has fallen below a predetermined amount.
A data compression unit for stopping compression of frame data; and a data compression unit provided in the data compression unit for compressing frame data.
Creates a compression start transmission frame before the start frame
And compress before the frame where data compression is stopped.
Compression start end transmission that creates and sends an end transmission frame
A frame creation unit, the compression start transmission frame from the transmission frame to the terminal compression
Compression start and end frame detection to detect end transmission frame
Output frame, and when a compression start transmission frame is detected,
Decompresses the frame data and detects the compression end transmission frame
A data restoring unit that stops restoring when it is executed.