JP2738639B2 - Cell number counting method and circuit thereof - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for processing cells in an ATM (Asynchronous Transfer Mode) network in which information constituting a call to be communicated is divided into fixed-length cells and transferred. , A method of counting the number of cells passing through a line, and a circuit thereof.

[0002]

2. Description of the Related Art In a communication network using an ATM, information constituting a call to be communicated is divided into fixed-length cells and transferred, so that media having different communication bit rates can be processed uniformly. . In this ATM network, the traffic can be grasped by counting the number of cells. In this case, if the total traffic from the start to the end of the communication of a certain logical channel is required, the number of cells of the channel may be simply counted and its accumulated value may be obtained. In the case of monitoring the use status of the network, the communication traffic at regular time intervals, that is, the number of cells may be measured. Further, in the case of pay-as-you-go billing in which a communication fee proportional to the number of transfer cells is paid, for example, when the charging unit price differs depending on the time zone such as daytime / nighttime, the number of cells is counted for each time zone. The need comes out.

[0003] On the other hand, in an ATM network, the number of logical channels multiplexed on the same line is large, for example, on a 156 Mbit / s line.
64 kbit / s communication can multiplex about 2,000 channels. In a cell number counting circuit on a line in which a large number of channels are multiplexed as described above, in a case where the number of cells is to be counted in a certain time zone, as a method of counting the number of cells by directly using a conventional counter value, There is a method of once reading the count value at the start time of the time zone.

FIG. 4 shows the configuration of a counting circuit according to this method.
When a cell arrives on a line 31 in which a plurality of logical channels are multiplexed, a cell detector 32 detects a logical channel number (VCI) of the cell, and a detected VCI value together with a cell count signal indicating the detection. Is sent to the selector 33.
When the cell arrives, the selector 33 fetches the VCI of the arriving cell as an address of the count value table 34, reads out the count value of the logical channel number, and inputs the value to the arithmetic unit 35.
After that, the value is stored in the count value table 34 again. On the other hand, when the count value is read, the VCI to be read from the control unit 36 is read.
At the same time, it sends a read signal to the selector 33. When reading the count value, the selector 33 takes in the VCI to be read as the address of the count value table 34 and
Is read out and stored in the control unit 36 as a count value read result.

Here, an example of the counting operation is shown in FIG. FIG.
Before the first cell arrives, the contents of the count value table corresponding to each VCI are all zero. Thereafter, every time a cell arrives, the count value, which is the content of the count value table corresponding to the VCI value of the cell, is incremented by one. The "@k" mark shown on the left of the time t axis in the figure indicates that the cell of VCI = k has arrived at that time. Here, it is assumed that the counting time zone switches at time t0,
At tn, the contents of the count value table are sequentially read for the logical channels of VCI = 1 to n, and the count value, which is the content, is rewritten to zero. By this reading process, the count value table holds the number of arriving cells after the reading process. If this reading time is completed between the time t0 and the arrival of the next cell, there is no counting error. However, as shown above, when thousands of logical channels are multiplexed on the same line, Is generally required to read the count value for all the channels.
Since it takes longer than about 2.7 μs on a t / s line), counting errors may occur for each channel. In the example of FIG. 5, since the cell of the VCI does not arrive from the time t0 to the reading time t1 for the VCI = 1, the count value "1" read at the time t1 is the VCI of the counting time zone 1.
= 1. On the other hand, VCI
= 2 from time t0 to reading time t2.
A cell, a cell of the same VCI has arrived. This one cell should be counted as an arrival cell in the counting time zone 2. However, since the contents of the count value table are continuously added until the reading process is performed, the count value read result for VCI = 2 at time t2 is the number of arriving cells “1” of VCI = 2 in the count time zone 1. And the number of arriving cells "1" from time t0 to time t2 is added. The control unit processes the added value as a result of counting the number of cells in the counting time zone 1, so that the time from time t0 to time t
The number of arriving cells “1” up to 2 is a counting error. VCI =
Similarly, for cell n, the number of arriving cells "2" from time t0 to the count reading time tn for VCI = n is added to the number of arriving cells "1" of the VCI in the counting time zone 1, and the cell number is counted. This results in a numerical error.

[0006]

As described above, it is difficult for the cell number counting circuit using the prior art to count the passing cells for each time zone with high accuracy without error. SUMMARY OF THE INVENTION It is an object of the present invention to eliminate the above-mentioned drawbacks and to realize a cell counting circuit which does not depend on the number of counting time zones and has a small amount of hardware and no counting errors.

[0007]

FIG. 1 shows an outline of a cell counting circuit according to the present invention. The present invention includes a counting table for the A and B2 surfaces and a counting surface identifier for displaying the counting surface of the time period so that the number of passing cells for each time period can be counted separately. When the cell arrives, the count value of the surface indicated by the counting surface identifier is incremented by one. By rewriting the value of this identifier, the counting surface can be switched for all logical channels at the same time.

According to the method of the present invention, information constituting a call is decomposed into fixed-length cells, and a logical channel number (VCI) for identifying the call is added to the cell header of each fixed-length cell, and a plurality of fixed-length cells are assigned on the same line. In a method of counting the number of passing cells for each VCI in an ATM network for multiplexing and transferring calls and counting the number of passing cells for each VCI, a two-sided count value table (A side, B), and a counting surface identifier indicating which counting value table is currently used, that is, which counting surface Xj is used, where the counting surface identifier takes a value of A or B and a predetermined counting time. When the cell arrives at the band j, the count value CA corresponding to the contents of the count value table of the VCI on the count surface Xj indicated by the count surface identifier.
(VCI) (when Xj = A) or count value CB (VC
I) Arrival processing for incrementing (when Xj = B) by +1
At the time of reading the count value of CI, the count value CA (V
CI) and CB (VCI) are simultaneously read, and then the count values CA (VCI) and CB (VCI) are cleared to zero, and a switching time from the count time zone j to the next count time zone j + 1 is performed. At tj, the value of the counting surface identifier is rewritten from A or B to B or A, respectively, to perform a counting surface switching process for switching the counting surface Xj upon arrival of the cell, and start counting at the counting surface A or B in the counting time zone j. After that, at the time of switching to the next counting time zone j + 1, the counting value reading process is being counted during the same time zone until the value of the counting surface identifier is rewritten to B or A, respectively, and the counting surface is switched. 1 for VCI
To calculate the total number of cells arriving in the counting time zone j by adding the count values of the counting surface Xj read in the counting time zone j and the counting time zone j + 1 one or more times as needed. It is characterized by.

In the counting circuit for realizing the above counting method, two count value tables (sides A and B) for holding the count value for each VCI, a count surface display register for holding the value of the count surface identifier, A selector for selecting a counting surface based on the value of the surface identifier; an arithmetic unit for incrementing the counting value of the selected counting surface by +1; upon arrival of the cell, receiving the VCI value stored in the cell header of the arriving cell; A cell count function for selecting a count value table on the count surface indicated by a selector with a selector, reading the count value for the VCI, incrementing the count value by an arithmetic unit, and storing the count value again in the count value table; Upon receiving an instruction to read the count value of the specific VCI, the values stored in the count value tables on both the A and B sides of the VCI to be read are simultaneously notified to the read control unit, and then the VCI is read. A count value reading function for writing zero to the count value tables on both sides A and B and clearing the count value to zero has a function of simultaneously switching the count surfaces of all VCIs by simply rewriting the count surface identifier value from the control unit. The number of passing cells before and after the identifier value rewriting instruction is counted separately, and the control unit identifies and processes each count value.

[0010]

By using the above-mentioned cell counting circuit, the switching error of the counting time zone for each logical channel, which is a problem in the prior art, is eliminated, and the hardware amount is small even for a plurality of counting time zones. It is possible to deal with it. Further, after switching the counting planes, the counting values of all the logical channels being communicated are temporarily read into the counting value table until the next switching, so that the two counting planes can cope with three or more types of counting time zones. is there.

[0011]

Embodiments of the present invention will be described below in detail with reference to the drawings. One embodiment of the present invention is shown in FIG. The cell number counting circuit 20 of the present invention includes a count value table A surface 11, a count value table B surface 12, a count surface display register 13 for holding a count surface identifier value, and a count surface based on the value of the register 13. It is composed of a selector 14, an operation unit 15 for incrementing the count value of the selected counting surface by +1 and a selector 16. The count value tables 11 and 12 hold the count value for each logical channel using the logical channel number as an address for each surface.

Count value table A side 11, count value table B
The switching of the plane 12 is performed by rewriting the value of the counting plane display register 13 from the control unit 19 which holds the time information of the counting time zone and the corresponding information of each counting time zone and the counting plane. In a series of counting time zones, A is used as a counting surface.
Plane and plane B are used alternately. That is, if the counting surface in a certain counting time zone j (time tj to tj + 1) is the surface A, the value of the counting surface display register 13 is changed from A to B at time tj + 1.
To the next counting time zone j + 1 (time tj + 1 to tj +
In 2), control is performed to count on the B side.

Here, when the cell detector 18 detects the arrival of a cell, it issues a cell count signal to the cell number counting circuit 20 and passes the logical channel number of the cell to the cell number counting circuit 20. When the cell arrives, the selector 16 fetches the logical channel number (VCI) of the arriving cell as an address of the count value tables 11 and 12, and the two count surfaces 11 and 12 of the count value table indicate the surface indicated by the count surface display register 13. (Surface A or B) is selected by the selector 14, and the count value CA (CVI) or CB (CVI) of the VCI of the arrival cell on the count surface is incremented by 1 in the arithmetic unit 15, and stored again in the same count value table. I do. Thus, the control unit 19 can simultaneously switch the count plane for all logical channels only by rewriting the value of the count plane display register 13.

On the other hand, when reading the count value, a read signal is sent to the selector 16 together with the logical channel number (VCI) to be read from the control unit 19. The selector 16 fetches the VCI to be read as an address of the count value tables 11 and 12 when reading the count value. Cell counting circuit 20
Then, when receiving a count value reading instruction from the control unit 19,
Regardless of the value of the counting surface display register 13, the values stored in the counting value tables 11 and 12 on both sides A and B of the VCI are simultaneously read and notified to the control unit 19. Count value table 1
After reading the count value, zero is stored in 1 and 12.

FIG. 2 shows a transition example of the count value in the cell counting circuit 20. Here, only the counting operation of the cell number of VCI = i is extracted and described, and the count value table is also
Only CI is shown. In the example of FIG. 2, the counting surface identifier indicates the counting on the A side in the counting time zone 1, and the count value of the number of arriving cells in this counting time zone is held in the counting value table on the A side. The “■” mark shown on the left of the time t axis in the figure indicates that the cell of VCI = i has arrived at that time. Here, at a certain time t0 in the counting time zone 1, the contents of the count value tables of the A and B surfaces corresponding to VCI = i are each set to zero. Thereafter, when a cell of VCI = i arrives during the counting time period 1, the count value which is the content of the count value table on the A side is incremented by one. In FIG. 2, six cells of VCI = i have arrived during the counting time zone 1, and the counting value, which is the content of the counting value table of VCI = i at the end time t1 of the counting time zone 1, is "A side". 6 "and the B side are" 0 ". When the control unit 19 rewrites the value of the count value identifier from A to B at time t1, cells arriving after time t1 are counted on the B side.

Thereafter, at a certain time in the counting time zone 2, the control unit
From 19, the values of the count value tables for both A and B planes with VCI = i are read. At this time, of the read count values, the value on the A side is the number of cells arriving at the cell of the VCI in the immediately preceding counting time zone 1 "6", and the value on the B side is counted from the time t1 at which the counting plane was switched. The number of cells arrived at the time of reading the numerical value is “3”. Since the content of the count value is set to zero upon reading and the count value is cleared, after the count value is read, the content of the count value table in the counting time zone 2 is zero on the A side, B on the B side.
The surface indicates the number of arriving cells after the reading process.

In this state, the next counting surface switching time t2
When the value of the counting surface identifier is rewritten from B to A, the number of arriving cells "4" until the time t2 after reading the counting value is held on the B surface, and the number of arriving cells in the counting time zone 3 after the time t2 is again A. Counted on the surface. Then, during counting time zone 3, VC
When the reading process of I = i is performed, the count value of the surface A (time t
The number of cells arriving after 2) "2" and the count value "4" of the B side counted up to time t2 are read.

At this time, the contents of the count value table at the time of reading the count value are such that if the value of the count surface identifier at the time of reading is A (or B), the count value of the A surface (or B surface) is the count time. The number of arriving cells in the band means the arriving cell in the counting time zone in which the count value of the B side (or the A side) is one immediately before. That is, the VC arriving at the counting plane Xj in a certain counting time zone j
When counting the total number of cells of I = i, once in time zone j,
Once in the next time zone j + 1, a count value reading operation is performed for the VCI, and the count value of each count surface Xj is controlled by the control unit.
It is sufficient to add up in 19. In the example of FIG. 2, the total number of arriving cells at VCI = i in the counting time zone 2 (counting surface: surface B) is “7”, which is the count value “3” of the surface B read in the counting time zone 2 And the count value “4” of the B side read in the next counting time zone 3 is calculated.

FIG. 3 shows the algorithm for counting the number of cells according to the present invention described above. In FIG. 3, a certain VCI (VCI
= I) only. Where VCI
= I, the content of the count value table for the A surface is represented by A (i), and the content of the count value table for the B surface is represented by B (i). The counting time zone j is switched to the next counting time zone j + 1 at time tj. In FIG. 2, the count value of each VCI is 1 for each counting time zone.
Although an example of reading the count value is shown, the operation algorithm of FIG. 3 is extended to a case where the count value is read a plurality of times in the same time zone.

As described above, if the reading of all the logical channel numbers (VCIs) being counted in each counting time zone is performed at least once for each VCI, the counting value table of A2 and B2 shown in FIG. As described above, it is possible to distinguish and count the number of arriving cells in any of three or more types of counting time zones. At this time, the reading of each VCI does not have a counting error due to the difference between the reading times as in the conventional method. For example, even when the number of cells is separated and counted every hour on a line multiplexed with 2,000 channels, one V
That is, the count value reading process should be performed on the CI.

[0021]

As described above, in the cell number counting circuit of the present invention, the number of passing cells for each logical channel number (VCI) on a line on which a large number of logical channels are multiplexed is distinguished and counted for each time zone. If there is no error in the counting time zone,
Moreover, it is possible to correspond to an arbitrary time zone with a small amount of hardware.

[Brief description of the drawings]

FIG. 1 shows a configuration example of a cell number counting circuit of the present invention.

FIG. 2 shows an operation example of the cell number counting circuit of the present invention.

FIG. 3 shows an operation algorithm of the cell number counting circuit of the present invention.

FIG. 4 shows a configuration example of a conventional cell number counting circuit.

FIG. 5 shows an operation example of a cell count value according to the related art.

[Explanation of symbols]

 11 Count value table A side 12 Count value table B side 13 Count plane display register 14 Selector 15 Operation unit or calculator 16 Selector 17 Line 18 Cell detection unit 19 Control unit 20 Cell count circuit 31 Line 32 Cell detection unit 33 Selector 34 Count value table 35 Operation unit 36 Control unit

Claims (2)

(57) [Claims] 1. A method for decomposing information constituting a call into fixed-length cells, adding a logical channel number (VCI) for identifying the call in a cell header of each fixed-length cell, and multiplexing a plurality of calls on the same line. In a method of counting the number of passing cells for each VCI in an ATM network for transmitting and transferring data by counting each time period, a two-sided count value table (sides A and B) for holding the value of the number of passing cells for each VCI ) And a counting plane identifier indicating the current counting plane Xj, where the counting plane identifier takes the value A or B. When a cell arrives in a predetermined counting time zone j, it is indicated by this counting plane identifier. Count value CA (VCI) (when Xj: A) or count value CB (VCI) (when Xj: B) corresponding to the contents of the count value table of the VCI on the counting surface Xj.
At the time of arrival processing of reading the count value of the corresponding VCI and the count values CA (VCI) and CB (VCI) of both sides A and B corresponding to the VCI regardless of the value of the count surface identifier.
Are read simultaneously, the counts CA (VCI) and C
Count value reading processing for clearing the value of B (VCI) to zero, and rewriting the value of the counting plane identifier from A or B to B or A at the switching time tj from the counting time zone j to the next counting time zone j + 1 Performs the counting plane switching process for switching the counting plane Xj upon arrival of the cell, starts counting on the counting plane A or B in the counting time zone j, and then switches the counting plane identifier at the switching time to the next counting time zone j + 1. During the same time period from when the value is rewritten to B or A and the counting surface is switched, the above-described count value reading process is performed once or as necessary at least once for the VCI being counted. j and counting time zone j + 1
A total number of cells arriving in the counting time zone j is calculated by adding up the count values of the counting surface Xj read in the step (b). 2. A counting circuit for realizing the counting method according to claim 1, wherein the two-sided count value table (A) holds a count value for each VCI.
Cell, surface B), a counting surface display register for holding the value of the counting surface identifier, a selector for selecting the counting surface based on the value of the counting surface identifier, and a calculator for incrementing the counted value of the selected counting surface by +1. Upon arrival, a VCI value stored in the cell header of the arriving cell is received, the count value table on the count surface indicated by the count value identifier is selected by the selector, the count value for the VCI is read, and the count value is calculated by the arithmetic unit. A cell number counting function for incrementing the count value by one and storing the count value in the count value table again, and a value stored in the count value table on both sides A and B of the VCI to be read when an instruction to read the count value of the specific VCI is received from the control unit. At the same time to the reading control unit,
By providing a count value reading function for writing zero to the count value tables on both the A and B sides of the VCI and clearing the count value to zero, the control unit can simultaneously switch the count surfaces of all VCIs simply by rewriting the value of the count surface identifier. A cell counting circuit which separates and counts the number of passing cells before and after a counting surface identifier value rewriting instruction, and identifies and processes each count value in a control unit.