JPH09284304A - Device for detecting cell collision - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a cell collision detecting device by which cell being the cause of collision is specified. SOLUTION: A fault detecting part 12 detects whether or not the cell arrived through a transmission path 11 is in a cell collision occurrence state where the cell is superimposed with one of the cells after and before it. A cell phase deviation judging part 13 monitors the cycle of cell arrival and detects the phase deviation of the cell. A fault cell judging part 17 discriminates which of the phase deviations of the two colliding cells caused the collision, by detecting whether the detected phase deviation of the cell occurred in a cycle prolonging direction or in a cycle shortening direction when the cell collision is detected. The cell being the collision cause is discriminated by the cell phase deviation so that the cell being the collision cause is easily specified.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cell collision detection device for detecting overlapping cell collisions of cells transmitted through a transmission path, and more particularly to a cell collision detection device capable of detecting a cell causing a collision. Regarding

[0002]

2. Description of the Related Art In local area networks,
There is one that performs communication in an asynchronous transfer mode in order to improve the transmission speed. In the asynchronous transfer mode, communication is performed in units of small packets called cells. Since the cells are transmitted from a plurality of transmitters on the communication cable of the network, it is necessary to control so as to avoid the collision and surely detect the occurrence of the collision.

Japanese Unexamined Patent Publication No. 2-37144 discloses a cell collision detection device for detecting cell collision on an optical transmission line. In this device, when two-way communication of CSMA / CD (Carrier Sense Multi-Access / Collision Detection) system is performed, the wavelength of an optical signal for transmitting a cell for detecting collision of an upstream signal is set for each transmitting device. It is shifting. Then, the collision of the cells is detected by detecting the overlap of the optical signals of two wavelengths over a certain period. In this device, the device that is the transmission source of the two cells that have collided is discriminated based on the wavelengths of the two optical signals that have collided.

[0004]

As described above, in the cell collision detection apparatus conventionally used, the center wavelengths of the optical signals to be output are different from each other in order to specify the transmission source apparatus of the cell in which the collision has occurred. It is necessary to use a transmitter. Therefore, different transmitters must be used individually,
There is a problem that the system configuration becomes complicated. Furthermore, although it is possible to identify the device that is the source of the two cells in which the collision has occurred, it is not possible to recognize which device caused the cell collision.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a cell collision detection device capable of identifying a cell that is a cause of collision.

[0006]

According to a first aspect of the present invention, a cell for detecting whether or not a cell arriving through a transmission line is in a state of cell collision overlapping with one of the cells before and after the cell. Collision detecting means, phase deviation detecting means for detecting the cell phase deviation by monitoring the arrival cycle of the cell through the transmission line, and when the cell collision detecting means detects the cell collision, the phase deviation detecting means detects the cell deviation. A cell and a discriminating means for discriminating which of the two cells has collided due to the phase shift occurring in the longer period or the shorter period of the cycle and the cell causing the collision. It is equipped in the collision detection device.

That is, according to the first aspect of the present invention, when a cell collision occurs, depending on whether the phase of the colliding cell is deviated in the direction in which the cycle becomes longer or in the direction in which it becomes shorter,
It is determined which of the two cells that have collided, the cell that has arrived first or the cell that has arrived later has a phase shift.

According to the second aspect of the present invention, it is determined whether or not a cell transmitted from a plurality of transmitters and arriving through the same transmission line is in a state of cell collision overlapping with one of the cells before and after the cell. Cell collision detection means for detecting, a phase shift detection means for monitoring the cycle of cells arriving through the transmission path for each transmission device of the transmission source and detecting the phase shift of the cell for each transmission device, and the cell collision detection means When a collision is detected, the cell collision detection device includes a determination device that determines the transmission device that is the transmission source of the cell in which the phase shift is detected by the phase shift detection device, as the transmission source of the cell that caused the collision. Prepared for.

That is, according to the second aspect of the present invention, the phase shift of the incoming cells is monitored for each transmission source of the cells, and when the cell collision occurs, the device of the transmission source of the cell causing the phase shift is determined as the cause of the collision. It is determined to be the transmitting device that has transmitted the cell.

According to another aspect of the present invention, the cell collision detecting means includes a cycle monitoring means for monitoring the arrival cycle of cells.
A cycle fluctuation detecting means for detecting that the incoming cycle of cells has fluctuated by a certain amount or more, and a collision judgment means for judging that a cell collision has occurred when the cycle fluctuation detecting means detects that the cycle has fluctuated by a certain amount or more. It is equipped with.

That is, in the invention according to claim 3, when two cells collide with each other, these two cells are continuous,
The arrival cycle of the cell fluctuates greatly at that time. Therefore, the collision of cells is detected based on the fact that the cycle of arrival of cells fluctuates by a certain amount or more.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows an outline of the structure of a cell collision detection apparatus according to an embodiment of the present invention. The upstream signal 11 transmitted by the cell is input to the failure detection unit 12 that detects the collision of the cell. The upstream signal 11 is also input to the cell phase shift determination unit 13 that determines the phase shift of the cell. When detecting a cell collision, the failure detection unit 12 outputs a failure signal 14 indicating the fact and a number notification signal 15 indicating the cell numbers of the two cells that have collided.

The cell phase shift judging unit 13 monitors the arrival cycle of the cell, and when the cycle shift occurs, whether the cell number of the cycle shift and the phase shift in the backward direction of the cell become longer. , A cell phase shift number notification signal 16 indicating whether or not a phase shift has occurred in the front where the cycle is shortened is output. The fault signal 14, the number notification signal 15, and the cell phase shift number notification signal 16 are input to the fault cell determination unit 17. The faulty cell determination unit 17 determines a cell that has caused a cell collision based on these signals and outputs a faulty cell detection signal 18 indicating the cell number.

FIG. 2 shows a state of cells on a transmission line in a state where no cell collision occurs. Each cell from cell (S1) 21 to cell (Sn) 22 is
Data is transmitted on the transmission path at a constant cycle (phase), and there is a substantially constant free time between cells.

FIG. 3 shows a state of cells on a transmission line in a state where cell collision occurs. The cell (S1) 31 and the cell (S2) 32 overlap each other in the shaded portion 32. Collisions rarely occur when the two cells are out of phase together, and usually
The cause is the phase shift of either the cell 31 or the cell 32.

FIG. 4 shows an outline of the configuration of the fault detecting section shown in FIG. The failure detection unit 12 includes a cell cycle detection unit 41 that detects the cycle of incoming cells, and an average cycle calculation unit 42 that calculates the average value of the calculated cell cycles. Further, a comparing unit 43 that determines whether the difference between the average period and the period of the cell detected this time is greater than or equal to a predetermined reference value, and a cell that extracts a cell number from a cell that arrives when there is a difference equal to or greater than the reference value The number extraction unit 44 is provided.

When the difference between the cycle detected this time and the average cycle is equal to or greater than the reference value, the cell number extraction section 44 determines that a cell collision has occurred, and outputs the fault signal 14 and the number notification signal 15 at this time. . The cell cycle detection unit 41 counts this clock between the arrival of one cell and the arrival of the next cell, and a clock unit (not shown) that outputs a clock having a cycle sufficiently shorter than the arrival cycle of the cell. A counter (not shown) is provided. This counter measures the period of arrival of cells.

As shown in FIG. 2, the cells arrive in a substantially constant cycle in a normal state. Therefore, the failure detection unit 12
Monitors the arrival of cells at regular intervals,
When the cycle fluctuates by more than the reference value, it is determined that a cell collision has occurred. For example, if the collision of the cells shown in FIG. 3 is caused by the backward shifting of the phase of the cell 31, the cycle from the cell immediately before the cell 31 to the cell 31 becomes long. Further, since the cell 31 and the cell 32 are continuous due to the collision, the cell detected after the cell 31 is the cell next to the cell 32, and the period therebetween is also long.

On the other hand, when a cell collision occurs due to the phase shift of the cell 32, the cycle from the detection of the cell 31 to the detection of the cell next to the cell 32 becomes long. That is, when a cell collision occurs, two cells are continuous and one cell is missing, and the cycle temporarily fluctuates. Fault detection unit 1 based on the fluctuation of this cycle
2 detects a cell collision. When the latter half of the cell is destroyed by the collision, the cell number extraction unit 54 shown in FIG. 5 extracts the cell number from here because the header portion is normal. On the other hand, when the first half of the cell is destroyed by the collision, the colliding number is calculated from the cell numbers that arrive before and after the collision.

FIG. 5 shows an outline of the configuration of the cell phase shift judging section shown in FIG. The cell phase shift determination unit 13 includes a cell period detection unit 51 that detects the period of an incoming cell and an average period calculation unit 52 that obtains an average value of the detected periods. Further, a phase shift calculation unit 53 that obtains a difference between the average cell cycle and the cell cycle detected this time,
The cell number extracting unit 54 that extracts the cell number from the cell that has arrived this time. The cell cycle detection unit 51 has the same configuration as the cell cycle detection unit 41 shown in FIG.

The phase shift calculation unit 53 obtains the difference between the cycle of the cell that has arrived this time and the average cycle, and outputs information indicating whether this cycle is shorter or longer than the average cycle. The cell number extraction unit 54 outputs the cell phase shift number notification signal 16 in which the information indicating the direction of the change in the cycle input from the phase shift calculation unit 53 is added to the cell number extracted from the cell that has arrived this time.

FIG. 6 shows the state of cells input to the cell phase shift judging section. The cell phase shift determination unit 13 (FIG. 1) monitors the phase interval (cycle) of the incoming cells and determines whether the cell has a phase shift in the rear or a phase shift in the front. When there is no shift in the phase spacing of the cells (FIG. 6a), the cells arrive with a substantially constant period 61. When the cell (S1) 62 is displaced rearward (FIG. 11B), the interval 64 between the cell (Sn) 63 and the cell (S1) 62 becomes longer than the cycle 61.

The average period calculation unit 52 calculates the average of the period of arrival of cells, and constantly monitors in which direction and how much the period of the cell that has arrived this time deviates from the average period. Thereby, it is detected that the phase of the cell (S1) 62 is shifted backward.

The cell number extracting section 54 (FIG. 5) of the cell phase shift determining section 13 extracts the cell number in which the phase shift is detected, and indicates the direction in which the phase shift has occurred and the cell number in which the phase shift has occurred. The cell phase shift number notification signal 16 is output. The cell number is extracted from the header part of the cell. The failed cell determination unit 17 (FIG. 1) identifies the cell that caused the cell collision from the failure signal 14, the number notification signal 15 and the cell phase shift number notification signal 16.

FIG. 7 shows an outline of the configuration of the faulty cell determination section. Faulty cell determination unit 17 shown in FIG.
Has a phase shift direction discriminating section 71 for discriminating the direction of the phase shift represented by the cell phase shift number notification signal 16 input from the cell phase shift determining section 13. Cell number selection unit 72
A fault signal 14 and a number notification signal 15 are input from the fault detector 12.

If the cell number selection unit 72 indicates that the signal input from the phase shift direction determination unit 71 when the fault signal 14 is input is shifted in the direction in which the cell cycle becomes longer, the cell number selection unit 72 The cell number that arrives first is selected from the cell numbers indicated by the notification signal 15, and the failed cell detection signal 18 is selected.
Output as When the signal input from the phase shift direction determining unit 71 when the fault signal 14 is input indicates that the signal is shifted in the direction in which the cell cycle becomes shorter, the cell number indicated by the number notification signal 15 The number of the arriving cell is selected and output as the faulty cell detection signal 18.

In the case of the example shown in FIG. 6, the cell (S1) 4
The cell phase shift determination unit 13 notifies that the number 2 is shifted backward. Then, the collision cell (S1)
And the cell (S2), the cell causing the collision is the cell (S1).
Then, the faulty cell detection signal 18 representing the number of the faulty cell is output.

Since the cell causing the collision can be discriminated based on the phase shift in this way, it is not necessary to use optical signals of different wavelengths for each transmitter, and the system configuration can be simplified. . Further, since the colliding cell can be specified, it is possible to easily determine which information has been lost.

Deformability

The cell collision detection device of the present invention can be variously modified. As an example, when a cell on the transmission path is transmitted from a plurality of transmitters, the transmitter of the sender of the cell that caused the cell collision may be determined. For example, the cell (S1) and the cell (S
2) is transmitted from a different transmitting device. It is assumed that these transmitting devices alternately transmit cells at a constant same cycle with a phase difference of half cycle.

The cell collision is detected in the same manner as in the embodiment. On the other hand, the cell phase shift determination unit 13 detects the cell phase shift for each transmission device. For example, assuming that cells are alternately transmitted from the first and second transmission devices, the cycle of arrival of cells from the first transmission device and the cycle of arrival of cells from the second transmission device are respectively set. Detect individually. Then, the tendency of the phase shift such that the phase of the cell from the first transmitter tends to shift backward and the phase of the cell from the second transmitter hardly shifts is always known.

When a cell collision is detected by the fault detection unit 12, the faulty cell determination unit 17 determines which transmission device to use based on the tendency of the cell phase shift recognized by the cell phase shift determination unit 13. Is the cause of cell collision. For example, if the cells from the first transmitting device tend to be out of phase backward and the cells from the second transmitting device tend to be out of phase almost, the first transmitting device is considered to be the cause of the collision. Then, the cell transmission source is determined.

As described above, the temporary phase shift when a cell collision occurs is not the first judgment based on the tendency of the phase shift.
It is also possible to detect which of the above-mentioned transmitting device and the second transmitting device has occurred in the cell and to identify the device that is the source of the cell causing the collision based on this.

[0035]

As described above, according to the first aspect of the present invention, since the cell causing the collision is determined based on the phase shift of the cells, the cell causing the collision can be easily specified. You can Further, since it is sufficient to detect the phase shift, it is possible to simplify the configuration of the cell collision detection device.

According to the second aspect of the present invention, the phase shift of the incoming cells is monitored for each transmission source of the cells, and when the cell collision occurs, the transmission source of the cell having the phase deviation is detected as the cause of the collision. It is determined that the transmitting device has transmitted the cell of. As a result, it is possible to easily identify the transmission source of the cell causing the collision, and it is possible to quickly and appropriately take a countermeasure for avoiding the cell collision.

Further, according to the third aspect of the invention, the collision of cells is detected based on the fact that the cycle of arrival of cells fluctuates by a certain amount or more. When two cells collide with each other, these two cells are continuous and the cycle of arrival of the cells fluctuates greatly temporarily. Therefore, the collision of cells can be easily detected based on the fluctuation of the cycle of arrival of cells. .

[Brief description of drawings]

FIG. 1 is a block diagram showing an outline of a configuration of a cell collision detection device according to an embodiment of the present invention.

FIG. 2 is an explanatory diagram showing a state of cells on a transmission line in a state where cell collision does not occur.

FIG. 3 is an explanatory diagram showing a state of cells on a transmission line in a state where cell collision occurs.

FIG. 4 is a block diagram showing an outline of a configuration of a fault detection unit shown in FIG.

5 is a block diagram showing an outline of a configuration of a cell phase shift determining unit shown in FIG.

FIG. 6 is an explanatory diagram showing states of cells input to a cell phase shift determination unit.

7 is a block diagram showing an outline of a configuration of a failed cell determination unit shown in FIG.

[Explanation of symbols]

 11 Transmission Line 12 Failure Detection Unit 13 Cell Phase Shift Judgment Unit 14 Fault Signal 15 Number Notification Signal 16 Cell Phase Shift Number Notification Signal 17 Fault Cell Judgment Unit 18 Fault Cell Detection Signal 41, 51 Cell Cycle Detection Unit 42, 52 Average Cycle Calculation Part 43 Comparing part 44, 54 Cell number extracting part 53 Phase deviation calculating part 71 Phase deviation direction discriminating part 72 Cell number selecting part

Claims (3)

[Claims] 1. A cell collision detection means for detecting whether or not a cell arriving through a transmission line is in a state of cell collision overlapping with one of the cells before and after the cell, and arrival of the cell through the transmission line. A phase shift detecting means for monitoring the cycle and detecting the phase shift of the cell, and a direction in which the phase shift of the cell detected by the phase shift detecting means becomes longer when the cell collision is detected by the cell collision detecting means. Cell collision detection apparatus, which comprises a discrimination means for discriminating which of the two cells has collided due to the phase shift of the two cells colliding with each other depending on whether the collision has occurred in the first direction or in the direction of shortening. . 2. A cell collision detection means for detecting whether or not a cell transmitted from a plurality of transmitters and arriving through the same transmission line is in a state in which a cell collision overlaps with any cell before or after the cell. And a phase shift detecting means for detecting a cell phase shift for each transmitting device by monitoring the period of cells arriving through the transmission path for each of the transmitting source transmission devices, and detecting a cell collision by the cell collision detecting means. When this occurs, the phase shift detecting means is provided with a discriminating means for discriminating the transmitter of the source of the cell whose phase shift has been detected as the source of the cell causing the collision. Cell collision detection device. 3. The cell collision detection means, a cycle monitoring means for monitoring a cell arrival cycle, a cycle fluctuation detection means for detecting that the cell arrival cycle fluctuates by a certain amount or more, and the cycle fluctuation detection means. The collision determining means for determining that a cell collision has occurred when it is detected that the cycle has changed by a certain amount or more.
Alternatively, the cell collision detection device according to claim 2.