JP2943690B2 - Cell collision detector - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cell collision detecting device for detecting a cell collision in which cells transmitted through a transmission line overlap each other, and more particularly to a cell collision detecting device capable of detecting a cell causing a collision. About.

[0002]

2. Description of the Related Art In a local area network or the like,
Some devices perform communication in an asynchronous transfer mode to improve the transmission speed. In the asynchronous transfer mode, communication is performed in units of small packets called cells. Since a cell is transmitted from a plurality of transmitting devices on a communication cable of a network, it is necessary to control so as to avoid the collision and to reliably detect the occurrence of the collision.

[0003] Japanese Patent Application Laid-Open No. 2-37144 discloses a cell collision detection device for detecting cell collision on an optical transmission line. In this apparatus, when performing bidirectional communication in the CSMA / CD (Carrier Sense Multi-Access / Collision Detection) system, the wavelength of an optical signal for transmitting a cell for detecting collision of an uplink signal is determined for each transmitting apparatus. It is shifted to. Then, the cell collision is detected by detecting the overlap of the optical signals of the two wavelengths over a certain period or more. In this device, the transmission source device of the two colliding cells is determined based on the wavelengths of the two colliding optical signals.

[0004]

As described above, in the cell collision detecting apparatus conventionally used, the center wavelengths of the output optical signals are different from each other in order to identify the transmitting apparatus of the cell in which the collision has occurred. It is necessary to use a transmission device. For this reason, it is necessary to use a different transmission device for each,
There is a problem that the configuration of the system becomes complicated. Furthermore, although it is possible to identify the transmission source device of the two cells where the collision has occurred, there is a problem that it is not possible to recognize which device caused the cell collision.

It is an object of the present invention to provide a cell collision detection device capable of specifying a cell causing a collision.

[0006]

In [SUMMARY OF] of claim 1 wherein the invention, the arrival of a cell arriving at a substantially constant period through a transmission line
Monitor the cycle and if the cycle fluctuates more than the predetermined reference value
Phase shift before and after any of the cell collision detection means for detecting that a state resulting cell and overlap each other cell collision, incoming monitors the period of these cells of each cell via the transmission path of the cell when the Phase difference detecting means for detecting a cell collision, and when one of the two cells collides when the cell collision is detected by the cell collision detecting means, only one of the two cells collides forward or backward.
Which of the two cells collided depending on whether the phase shift of the cell detected by the phase shift detecting means occurred in the direction in which the cycle became longer or shorter in the direction in which The cell collision detection device is provided with a determination means for determining whether or not a collision has occurred due to a cell phase shift.

That is, according to the first aspect of the invention, when a cell collision occurs, whether the phase of the colliding cell is shifted in the direction of increasing the period or in the direction of shortening is determined by
It is determined which of the two cells that collided arrives first or the cell that arrives later has a phase shift. According to the first aspect of the present invention, (1) each cell
Arriving at a substantially constant period through the transmission path,
(2) When cell collision occurs due to phase shift
Indicates that only one of the colliding cells caused a phase shift
It is assumed that

According to the second aspect of the present invention, the transmission path
It monitors the arrival period of cells arriving at a substantially constant period and
Cell to detect that the period is in a state of cells arriving occurs in any cell and overlap each other cell collision before and after through multiple transmission paths identical are respectively transmitted from the transmitting apparatus when the variation predetermined reference value or more Collision detection means;
A cell collision is detected by the phase shift detecting means for monitoring the cycle of cells arriving through the transmission line for each transmitting apparatus of the transmission source and detecting a phase shift of these cells for each transmitting apparatus, and the cell collision detecting means. When the two cells collided
Only one of them is forward or backward due to the transmitter.
Under the premise that a phase shift has occurred, a determination means for determining that the transmission apparatus of the cell from which the phase shift has been detected by the phase shift detection means is the source of the cell that caused the collision. It is provided in a cell collision detection device.

That is, according to the second aspect of the present invention, the phase shift of the arriving cells is monitored for each source of the cells, and when a cell collision occurs, the source apparatus of the cell having the phase shift is determined to be the cause of the collision. It is determined that the transmitting apparatus has transmitted the cell. According to the second aspect of the invention, (1) each cell
Arrives at a substantially constant period through the transmission path, (2)
If the cell collision is caused by a phase shift,
Only one of the cells that caused the phase shift
And (3) forward or backward due to the transmitting device
The precondition is that there has been a phase shift
You.

[0010]

[0011]

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION

[0013]

FIG. 1 shows an outline of a configuration of a cell collision detecting apparatus according to an embodiment of the present invention. The uplink signal 11 from which a cell is transmitted is input to a failure detector 12 which detects cell collision. The uplink signal 11 is input to a cell phase shift determining unit 13 that determines a cell phase shift. 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 colliding cells.

The cell phase shift judging unit 13 monitors the cycle at which the cells arrive, and when the cycle changes, the number of the cell whose cycle has shifted and whether the cell has a phase shift after the cycle becomes longer. And outputs a cell phase shift number notification signal 16 indicating whether a phase shift has occurred before the cycle becomes shorter. 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 failed cell determination unit 17 determines the cell that caused the cell collision based on these signals, and outputs a failed cell detection signal 18 indicating the cell number.

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

FIG. 3 shows a state of a cell on a transmission line in a state where a cell collision occurs. The cell (S1) 31 and the cell (S2) 32 overlap each other at a hatched portion 32. Collisions are rarely caused by the two cells being out of phase together, and are usually
This is due to the phase shift of one of the cells 31 and 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 a cycle of an incoming cell and an average cycle calculation unit 42 that calculates an average value of the obtained cell cycles. A comparing unit 43 for determining whether a difference between the average cycle and the cycle of the cell detected this time is equal to or greater than a predetermined reference value; and a cell for extracting a cell number from a cell arriving when there is a difference equal to or greater than the reference value. A number extraction unit 44 is provided.

When the difference between the currently detected cycle and the average cycle is equal to or greater than the reference value, the cell number extracting section 44 determines that a cell collision has occurred, and outputs a failure signal 14 and a number notification signal 15 at this time. . The cell cycle detector 41 outputs a clock (not shown) that outputs a clock having a cycle sufficiently shorter than the cycle in which a cell arrives, and counts this clock from the arrival of one cell to the arrival of the next cell. (Not shown). This counter measures the cycle at which cells arrive.

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

On the other hand, when a cell collision occurs due to a shift of the phase of the cell 32 to the front, the period from the detection of the cell 31 to the detection of the next cell after the cell 32 becomes longer. That is, when a cell collision occurs, two cells are continuous, and one cell is missing, and the period temporarily fluctuates. Based on the fluctuation of this cycle, the failure detection unit 1
No. 2 detects cell collision. The cell number extraction unit 54 shown in FIG. 5 extracts the cell number from the header part is normal when the latter half of the cell is destroyed due to the collision, since the header part is normal. On the other hand, when the first half of the cell has been destroyed by the collision, the colliding number is determined from the cell numbers arriving 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 judging unit 13 includes a cell cycle detecting unit 51 that detects a cycle of an incoming cell, and an average cycle calculating unit 52 that calculates an average value of the detected cycles. A phase shift calculator 53 for calculating a difference between the average cell cycle and the cycle of the cell detected this time;
And a cell number extracting unit 54 for extracting the cell number from the cell arriving this time. The cell cycle detecting section 51 has the same configuration as the cell cycle detecting section 41 shown in FIG.

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

FIG. 6 shows the state of a cell input to the cell phase shift judging section. The cell phase shift determining unit 13 (FIG. 1) monitors the phase interval (period) of the arriving cell and determines whether the cell has shifted backward or forward in phase. When there is no shift in the cell phase interval (FIG. 6a), the cells arrive at a substantially constant period 61. When the cell (S1) 62 is shifted backward (b in the figure), the interval 64 between the cell (Sn) 63 and the cell (S1) 62 is longer than the period 61.

The average of the cell arrival periods is obtained by the average period calculation unit 52, and it is constantly monitored in which direction and how much the cell arrival time this time arrives deviates from the average period. Thus, it is detected that the cell (S1) 62 has shifted backward in phase.

The cell number extracting section 54 (FIG. 5) of the cell phase shift judging section 13 extracts the number of the cell in which the phase shift has been detected, and indicates the direction in which the phase shift has occurred and the number of the cell 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 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 failed cell determination unit. The failed cell determination unit 17 shown in FIG.
Has a phase shift direction determining unit 71 that determines the direction of the phase shift indicated by the cell phase shift number notification signal 16 input from the cell phase shift determining unit 13. Cell number selection section 72
, A failure signal 14 and a number notification signal 15 are input from the failure detection unit 12.

If the signal input from the phase shift direction judging unit 71 when the failure signal 14 is input indicates that the cell cycle is shifted in the direction in which the cell cycle becomes longer, the cell number selector 72 The cell number of the cell arriving earlier is selected from the cell numbers indicated by the notification signal 15, and the failed cell detection signal 18 is selected.
Output as If the signal input from the phase shift direction determining unit 71 when the fault signal 14 is input indicates that the cycle of the cell has shifted in the direction of shortening, the cell number indicated by the number notification signal 15 The number of the arriving cell is selected and output as a failed cell detection signal 18.

In the case of the example shown in FIG. 6, the cell (S1) 4
2 is notified from the cell phase shift determining unit 13 that the phase is shifted backward. Then, the colliding cell (S1)
Out of the cell and the cell (S2), the cell causing the collision is the cell (S1)
And outputs a failed cell detection signal 18 representing the number of the failed cell.

As described above, the cell causing the collision can be determined on the basis of the phase shift, so that it is not necessary to use an optical signal having a different wavelength for each transmitter, and the configuration of the system can be simplified. . In addition, since the colliding cell can be specified, it is possible to easily determine which information has been lost.

Deformability

The cell collision detecting device of the present invention can be variously modified. As an example, when a cell on a transmission path is transmitted from a plurality of transmitting devices, the transmitting device of the cell that caused the cell collision may be determined. For example, the cell (S1) shown in FIG.
It is assumed that 2) is transmitted from a different transmitting device. It is assumed that these transmitting devices alternately transmit cells at a constant same cycle shifted by a half cycle of the phase from each other.

Cell collision is detected in the same manner as in the embodiment. On the other hand, the cell phase shift judging unit 13 detects a cell phase shift for each transmission device. For example, assuming that cells are transmitted alternately from the first and second transmitting devices, the period at which cells arrive from the first transmitting device and the period at which cells arrive from the second transmitting device are respectively defined. Detect individually. Then, the tendency of the phase shift such that the phase of the cell from the first transmitting apparatus tends to shift backward and the phase of the cell from the second transmitting apparatus hardly shifts is always grasped.

When a cell collision is detected by the failure detecting unit 12, the failed cell determining unit 17 determines which transmitting device is used based on the tendency of the cell phase shift recognized by the cell phase shift determining unit 13. Is the cause of cell collision. For example, if the cells from the first transmitter tend to shift backward in phase and the cells from the second transmitter tend to shift little in phase, the first transmitter may be the source of the collision. Is determined as the cell transmission source.

As described above, instead of the determination based on the tendency of the phase shift, the temporary phase shift at the time of occurrence of the cell collision is the first phase shift.
It is also possible to detect which cell has been transmitted from which of the transmitting device and the second transmitting device, and identify the device that has transmitted the cell causing the collision based on this.

[0035]

As described above, according to the first aspect of the present invention, the cell causing the collision is determined based on the phase shift of the cell, so that the cell causing the collision can be easily specified. Can be. Further, since it is only necessary to detect the phase shift, it is possible to simplify the configuration of the cell collision detecting device. Furthermore, in the present invention, the cell arrival period is not less than a certain value.
The cell collision is detected based on the above fluctuation.
If two cells collide, these two cells will continue
The period at which the cell arrives temporarily fluctuates greatly,
Easier cell collision based on fluctuations in cell arrival cycle
Can be detected.

According to the second aspect of the present invention, the phase shift of the arriving cell is monitored for each source of the cell, and when the cell collision occurs, the source of the cell having the phase shift is determined as the cause of the collision. Is determined to be the transmitting apparatus that has transmitted the cell of the above. This makes it possible to easily identify the source of the cell that caused the collision, and to take quick and appropriate measures to avoid cell collision. Further, in the present invention,
Based on the fact that the cycle at which the
Has detected a collision. When two cells collide,
Since the two cells are consecutive, the cycle at which the cells arrive is temporarily
Large fluctuations, the fluctuations of the cell arrival cycle
Based on this, it is possible to easily detect cell collision.

[0037]

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating 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 a cell on a transmission path in a state where no cell collision occurs.

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

FIG. 4 is a block diagram illustrating an outline of a configuration of a failure detection unit illustrated in FIG. 1;

FIG. 5 is a block diagram illustrating an outline of a configuration of a cell phase shift determining unit illustrated in FIG. 1;

FIG. 6 is an explanatory diagram illustrating a state of a cell input to a cell phase shift determining unit.

FIG. 7 is a block diagram illustrating an outline of a configuration of a failed cell determination unit illustrated in FIG. 1;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 11 Transmission path 12 Fault detection part 13 Cell phase shift judgment part 14 Fault signal 15 Number notification signal 16 Cell phase shift number notification signal 17 Fault cell determination part 18 Fault cell detection signal 41, 51 Cell cycle detection part 42, 52 Average cycle calculation Unit 43 comparison unit 44, 54 cell number extraction unit 53 phase shift calculation unit 71 phase shift direction determination unit 72 cell number selection unit

Claims (2)

(57) [Claims] The present invention monitors an arrival period of a cell arriving at a substantially constant period through a transmission line, and sets the period to a predetermined reference value.
I weight and any of the cells before and after the cell when you change more
A phase shift detection means for monitoring a cell collision detection means, the incoming cycle of each cell through the transmission path to detect the phase shift of these cells detected to have occurred in the cell collision fit Ri, wherein When a cell collision is detected by the cell collision detection means, only one of the two cells that collided moves forward or backward.
Of any cell of the two cells of a collision by either occurred in the direction of the phase shift of the detected cell in the phase shift detection means under the assumption that caused the phase shift is shortened or occurred become longer direction of the period A cell collision detection device comprising: a determination unit configured to determine whether a collision has occurred due to a phase shift. 2. Arrival at a substantially constant period through a transmission line.
The arrival period of the cell is monitored and the period is set to a predetermined reference value.
A cell collision detection means for detecting that the cell which arrives through the transmission path are respectively transmitted the same from a plurality of transmitting apparatuses when varied over a state resulting before and after any cell and overlap each other cell collision, the transmission A period of cells arriving through a path is monitored for each of the transmitting devices as their transmission sources, and a phase deviation detecting unit for detecting a phase deviation of these cells for each transmitting device; and a cell collision is detected by the cell collision detecting unit. Only one of the two cells that collided when
Or a rearward phase shift. <br/> The phase shift detector detects the phase shift of the cell from which the transmitting apparatus is to be transmitted to the cell source that caused the collision. A cell collision detection device comprising: a determination unit that determines that there is a cell collision.