JP3087733B2 - ATM communication controller - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ATM (Asynchro
The present invention relates to a communication control device, and more particularly, to an ATM communication control device having a function of executing ABR (Available Bit Rate).

[0002]

2. Description of the Related Art In ATM communication, transmission is carried out in units of cells consisting of headers and data, and it is possible to efficiently multiplex multiple information on a line and to support a wide range of multimedia. There are features. ABR is one of the service classes of the ATM communication. This ABR is
The network node informs the terminal of the congestion status so that the terminal can adjust the cell transmission rate. To implement ABR, the ATM controller
It is necessary to be able to set a plurality of cell transmission intervals and to have a function of changing the transmission interval during transmission.

To meet this demand, for example, as disclosed in Japanese Patent Application No. 9-304599, a CAM (Content Addressable) storing a transmission time in data using a channel number as an address. Memor
y), a timer that counts the transmission time, and
There has been proposed a communication control device including a timer for searching for a CAM and capable of arbitrarily setting a cell transmission interval.

FIG. 10 shows a conventional ATM communication control device. The conventional ATM communication control apparatus includes a transmitting unit 1 for transmitting a cell transmission signal 2 and inputting a channel number 3, a channel buffer 4 connected to the transmitting unit 1, an ABR scheduler 7 connected to the channel buffer 4, a cell A transmission timer 8 activated based on the transmission signal 2 and a read timer 1 activated based on the absolute transmission time 9 from the transmission timer 8
0, information on the transmission time 11 from the read timer 10 and a schedule table 12 connected to the ABR scheduler 7. The schedule table 12 contains (CAM). The channel buffer 4 is a FIFO that holds a channel number, and writes and reads a channel number 6. F
When writing to the IFO cannot be performed (such a state is called internal congestion), the stop signal 5 is activated to stop writing.

The ABR scheduler 7 has a scheduler 1
7 and the ACR table (allowed transmission rate: Allowed Cell
Rate 18). When the channel number 20 is input from the scheduler 17, the ACR table 18 stores the currently set A corresponding to the channel number.
It outputs CR21. The scheduler 17 has a function of writing to the channel buffer 4 and a function of calculating the next transmission time. The function of writing to the channel buffer 4 is such that the CAM-Hit signal 13 (signal notifying that there is applicable data) is active and the stop signal 5
Schedule table 1 when is inactive
This is a process of outputting the channel number 16 from 2 to the channel buffer 4 as the channel number 6. The function of calculating the next transmission time is based on the channel number 16 output from the schedule table 12 when the CAM-Hit signal 13 is active and the stop signal 5 is inactive.
Is output to the ACR table 18 as the channel number 20, the current ACR 21 is read, and the read timer 1 is read.
Using the transmission time 11 output from 0, the next transmission time 15 is calculated. Equation (10) shows the calculation formula. Next transmission time = current transmission time + F1 (current ACR) (10)

[0006] The transmission timer 8 has a counter inside. This counter counts up by one when the cell transmission signal 2 becomes active. The count value is output as the absolute transmission time 9. The read timer 10 also has a counter inside. Read timer 10
When the CAM-Hit signal 13 is inactive, the counter counts up by one in synchronization with the absolute transmission time 9. The count value is, as the current transmission time 11,
Output to the schedule table 12.

The schedule table 12 switches between a RAM state and a search state based on a switching signal 14.
In the RAM state, the transmission time 15 is written as data to the address specified by the channel number 16. on the other hand,
In the search state, the transmission time 11 is searched as data, and when the corresponding data is found, the address is output as the channel number 16 and the CAM-Hit signal 13 as a signal indicating that there is the corresponding data is output. Activate.

FIG. 11 shows the processing of the ATM communication control device of FIG. 10, and FIG. 12 shows the processing following FIG. FIG.
The operation of the ATM communication control device of FIG. 10 will be described with reference to the flowchart of FIG. 11 and 12,
“S” represents a step.

The transmitting unit 1 activates a cell transmission signal 2 every time one ATM cell is processed. Transmission timer 8
Determines the cell transmission signal 2 (S401), and if the cell transmission signal 2 is active, counts up the internal counter, reads out the absolute transmission time 9, and sends it to the timer 10 (S402). When the absolute transmission time 9 counts up, the read timer 10 counts up an internal counter in synchronization with the absolute transmission time 9 and outputs the transmission time 11 to the schedule table 12 (S40).
3). At this time, the CAM-Hit signal 13 is in an inactive state. Using the transmission time 11 as data, the schedule table 12 searches for a built-in CAM (S40).
4). As a result of the search, if there is corresponding data, CAM-
The Hit signal 13 is activated (S405), and the address corresponding to the corresponding data is output as the channel number 16 (S406). The scheduler 17 outputs the stop signal 5
It is determined whether or not internal congestion has occurred in the channel buffer 4 based on the above (S407).

If the stop signal 5 is inactive, no internal congestion has occurred in the channel buffer 4 and the cell of the channel number whose transmission time is the present can be transmitted.
The scheduler 17 performs a transmission process. First, the channel number 20 that is the current transmission time is output to the ACR table 18, and the current A number set in the channel number 20 is output.
The CR 21 is read (S409). Next, the next transmission time 15 is calculated (S410). Next, the calculated transmission time is output as the transmission time 15 (S411). next,
The switching signal 14 is set to the RAM state (S412),
The channel number 16 and the next transmission time 15 are output, the calculation result is written to the CAM in the schedule table 12 (S413), and the switching signal 14 is returned to the search state (S413).
414). Finally, the channel number 16 input from the schedule table 12 to the scheduler 17 is output to the channel buffer 4 as the channel number 6 (S4).
15). The schedule table 12 stores the scheduler 1
7, when the data is rewritten, the transmission time 11
Is searched using the data as a CAM (S404).

When the stop signal 5 is active and the scheduler 1
If writing to the channel buffer 4 cannot be performed from Step 7 (internal congestion state), the processing is stopped until writing becomes possible (S407). Therefore, writing to the CAM in the schedule table 12 is not performed, and the CAM-H
Since the it signal 13 does not become inactive, the read timer 10 stops. The channel buffer 4 has F
The state of the IFO is determined (S416), and if writing to the FIFO is possible, the stop signal 5 is made inactive (S417).
After 418), the process proceeds to S104.

As a result of searching the schedule table 12 in S104, if there is no corresponding data and the CAM-Hit signal 13 becomes inactive (S406), the read timer 10 compares the absolute transmission time 9 with the transmission time 11 (S419). ), If not equal, increment the counter by one and output the transmission time 11 (S42)
0). The schedule table 12 indicates that the transmission time 11 is 1
Since the count has been increased, the CAM is searched again using the transmission time 11 as data (S404). If the absolute transmission time 9 and the transmission time 11 match, the process proceeds to S401. When the cell transmission signal 2 is determined by the transmission timer 8 and the cell transmission signal 2 becomes active, the processing after S402 is repeated as described above, and the transmission processing is performed.

FIG. 13 shows the state of execution of transmission during normal times and when internal congestion occurs, and the contents of the schedule table 12 and the ACR table 18. (A) shows a normal transmission interval, (b) shows a transmission interval when internal congestion occurs,
(C) is the content of the schedule table 12, (d) is A
The content of the CR table 18 is shown.

In the normal transmission interval shown in FIG. 13A, the ACR (allowable transmission rate) is set so that one channel of the ABR service class exists and the cell is output in the "1/3" band. In the case where the cell transmission is specified and no internal congestion occurs, the state of cell transmission in which the transmission time 11 starts from “0” is shown. In this case, since the ACR is set to be transmitted at “１ ／”, the transmission interval is “3”, and the transmission cell is transmitted with a transmission time that is a multiple of three.

FIG. 13B shows a transmission interval at the time of occurrence of internal congestion. There is one channel of the ABR service class, and the ACR is specified by the ACR so as to output a cell in a band of “１ ／”. FIG. 6 is a diagram showing a state of cell transmission in which transmission time 11 starts from “0” when internal congestion occurs when the transmission is in progress.

FIG. 13C shows the change of the transmission time recorded in the CAM of the schedule table 12 in FIG.
(B) corresponds to the transmission interval at the time of occurrence of internal congestion. FIG. 13D shows the ACR table 18.
13A and 13B correspond to the transmission interval at the time of occurrence of the internal congestion shown in FIG. 13B.

A description will be given of the time of occurrence of internal congestion.
3 (b), when the transmission time 11 is “0”, C
The AM-Hit signal 13 becomes active, and transmission of the transmission cell “1” starts. At this time, since no internal congestion has occurred in the channel buffer 4, the stop signal 5 is inactive. The scheduler 17 writes the channel number 6 in the channel buffer 4 and calculates the “next transmission time”. As set in the ACR table of FIG. 13D, the ACR is “１ ／”. The current transmission time is “0”. Therefore, "next transmission time"
Is “3” from equation (10). In the schedule table of FIG. 13B, “3” is set as “next transmission time”.
Is set. When the transmission time 11 is “3”, the transmission cell “2” is processed in the same manner as when the transmission time 11 is “0”. Since the current ACR is “１ ／”, the “next transmission time” is “6” according to equation (10). The “next transmission time” is displayed in the schedule table of FIG.
Is set as “6”.

In FIG. 13B, when the transmission time 11 is "4", internal congestion occurs in the channel buffer 4 and the stop signal 5 becomes active. When the transmission time 11 becomes "6", the CAM-Hit signal 13 becomes active and attempts to process the transmission cell "3", but the stop signal 5 remains active because internal congestion has occurred. . The scheduler 17 suspends the processing until the stop signal 5 becomes inactive. Therefore, the read timer 10 stops, and the transmission time 11 remains “6”.

When the transmission time 11 is "6" immediately before "7", the internal congestion is released, the stop signal 5 becomes inactive, and the transmission cell is transmitted in the same manner as when the transmission time is "0". "3" is processed. Originally, this cell "3" is a cell that had been calculated at the transmission interval "3" at the time of transmission of the transmission cell "2" and should have been transmitted at the transmission time "6". However, due to the occurrence of internal congestion, the transmission interval has been extended from “3” to “5”. Current AC
Since R is “１ ／”, the “next transmission time” is given by the equation (1).
0) to “9”. As shown in FIG. 13C, “9” is set as the “next transmission time” in the schedule table 12. When the absolute transmission time 9 is "9", since the difference between the absolute transmission time 9 and the transmission time 11 is open, the read timer continues counting up until it catches up with the absolute transmission time. When the transmission time reaches “9”, the transmission cell “4” is processed. Here, since the transmission cell “3” is processed with the absolute transmission time “8”, the transmission interval between the transmission cells “3” and “4” has been reduced to “1”. Since the current ACR is “１ ／”, the “next transmission time” is “12” according to Expression 10. In the schedule table 12, “12” is set as “next transmission time”.

[0020]

However, the conventional ATM
According to the communication control device, when the internal congestion occurs in the channel buffer 4, the channel whose transmission time is reached while the scheduler 17 is stopped is not transmitted at the transmission time, and the transmission interval is extended until the internal congestion is resolved. Would. For this reason,
The transmission is performed at a transmission interval longer than the interval specified by the ACR. Further, after the internal congestion state is resolved, the transmission time 11 advances earlier, so that the transmission time is longer than the specified transmission interval.
Cells are transmitted at short intervals.

Therefore, an object of the present invention is to provide an ATM which can always transmit cells at intervals specified by the ACR even when internal congestion occurs and the read timer stops.
A communication control device is provided.

[0022]

According to the present invention, in order to achieve the above object, as a first feature, a current cell is transmitted.
After that, the allowable transmission rate ACR (Allowed Cell Rate)
Calculate next cell transmission time based on the corresponding transmission interval
And stores the next transmission time in the schedule table
Transmitting the next cell based on the schedule table.
To ATM communication controller using asynchronous transfer mode
The internal congestion state that occurred on the transmitting side
Transmission side stop signal output means for outputting a signal, and the next cell
The stop signal is not released even when
ACR reset to reset the ACR of the next cell at the time
ATM communication control device, comprising:
Provide a replacement .

In order to achieve the above object, the present invention has, as a second feature, a transmission section for transmitting a cell according to a channel number and activating a cell transmission signal after the transmission, A transmission timer that counts up each time it becomes active and outputs this as an absolute transmission time, a read timer that counts the absolute transmission time and outputs the transmission time, a RAM state and transmission time that stores the transmission time as data And a ACR table for recording the currently set ACR for each channel, and calculating the next transmission time based on the ACR stored in the ACR table. An ABR scheduler, and a stop signal that becomes active when internal congestion occurs. And a channel buffer for reading out the channel number from the ABR scheduler and sending out the channel number to the transmitting unit, wherein the ABR scheduler calculates the next transmission time, and A scheduler having a function of writing the channel number into the channel buffer; and a rescheduling unit for lowering an ACR recorded in the ACR table when the internal congestion occurs, and calculating a transmission time of the next cell from the new ACR. An ATM communication control device characterized by comprising:

[0024]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows a first embodiment of an ATM communication control device according to the present invention. In the figure, the same reference numerals are used for the same elements as those shown in FIG.

The ATM communication control apparatus according to the present invention constitutes an ABR scheduler 30 by adding a rescheduling unit 25 and a switch 28 to the ABR scheduler 7 of FIG. 10, as described later. Accompanying this, transmission time 1
1 is assigned to the ABR scheduler 7.

FIG. 2 shows the detailed configuration of the ABR scheduler 30. A rescheduling unit 25 is connected to the scheduler 17 and the ACR table 18. The rescheduling unit 25 is provided with the recalculation request signal 24 from the scheduler 17, and at the same time, the switch 28 is switched by the recalculation request signal 24. The switch 28 selects one of the transmission time 26 from the scheduler 17 and the transmission time 27 from the rescheduling unit 25. The output of the switch 28 is transmitted to the schedule table 12 as the transmission time 15.

The rescheduling unit 25 functions to lower the ACR recorded in the ACR table 18. Then, the transmission time is recalculated in consideration of the transmission interval extended by lowering the ACR, and the transmission time recorded in the CAM in the schedule table 12 is updated. With this function, the ACR is changed for the channel that has become the transmission time at the time of internal congestion in consideration of the time when transmission becomes impossible due to internal congestion, and when transmitting cells after internal congestion is released, the transmission interval specified by the ACR Can transmit the cell.

The ABR scheduler 30 has a function of writing to the channel buffer 4, a function of calculating the “next transmission time”, and a request for a recalculation request signal 2
4 is provided. CAM-
When the Hit signal 13 becomes active, the stop signal 5 is determined. If the stop signal 5 is inactive, the channel number 6 is written to the channel buffer 4. Then, the “next transmission time” of the channel is calculated with reference to the transmission time 11 and is output as the transmission time 15. Next, the switching signal 14 is switched to the RAM state, the calculated next transmission time 26 is written in the schedule table 12, and the switching signal 14 is returned to the search state. If the stop signal 5 is active, writing to the channel buffer 4 is not performed. Then, the transmission time of the channel is recalculated with reference to the transmission time 11. Next, the ABR scheduler 30 switches the switching signal 14 to the RAM state, writes the recalculated next transmission time 26 to the schedule table 12 via the switch 28, and returns the switching signal 14 to the search state.

The function of writing to the channel buffer 4 in the ABR scheduler 30 corresponds to the CAM-Hit signal 13.
Is active and the stop signal 5 is inactive. A process of outputting the channel number 16 as the channel number 6 and writing it to the channel buffer 4 is performed.

The function for calculating the “next transmission time” is provided by CA
When the M-Hit signal 13 is active and the stop signal 5 is inactive, the channel number 16 output from the schedule table 12 is stored in the ACR table 18.
Output as channel number 20, and based on this, the current A
The CR 21 is read, and the next transmission time 26 is calculated using the transmission time 11 output from the read timer 10. The calculation formula is represented by formula (1). Next transmission time 26 = transmission time 11 + F1 (current ACR) (1) (F1 is a function for obtaining a transmission interval from the ACR, and in this example, is a reciprocal of the ACR)

Next, the switching signal 14 is switched to the RAM state, the calculated next transmission time 26 is output as the transmission time 15, written into the schedule table 12, and the switching signal 14 is returned to the search state. Also, the current ACR 21 used for the calculation is output as the previous ACR 19, and the previous ACR recorded in the table 18 is used as the previous ACR.
Replace with 9.

The function of outputting the recalculation request signal 24 to the rescheduling unit 25 of the scheduler 17 is provided by a CAM-
This is a process to be output when the stop signal 5 is active and the process of writing to the channel buffer 4 cannot be performed although the Hit signal 13 becomes active and there is data to be written to the channel buffer 4. The rescheduling unit 25 performs the following calculation.

(I) The previous transmission interval is set to the previous ACR 23
Calculate from Previous transmission interval = F1 (previous ACR 23) (2) (ii) Find a new transmission interval. New transmission interval = previous transmission interval + delay interval (3) (iii) A new ACR 22 is calculated from the new transmission interval. New ACR22 = F2 (new transmission interval) (4) (F2 is a function for calculating the ACR from the transmission interval, and in this example, is the reciprocal of the transmission interval)

The current and previous ACRs recorded in the ACR table 18 are replaced with new ACRs 22.
The function of calculating the new transmission time 27 is to read the previous ACR 23 from the ACR table 18, read the transmission time 11 from the read timer 12, and read the new transmission time 2
7 is calculated by equation (5). New transmission time = transmission time 11 + delay interval ... (5)

Next, the ATM having the configuration shown in FIGS.
The operation of the communication control device will be described. FIG. 3 shows the operation of the ATM communication control device of the present invention. “S” in the figure means a step. Hereinafter, the same applies to each flowchart. After processing one ATM cell, the transmission unit 1 activates the cell transmission signal 2. The transmission timer 8 determines the cell transmission signal 2 (S101). If the cell transmission signal 2 is active, the internal counter counts up by one and outputs the absolute transmission time 9 (S10).
2). When the absolute transmission time 9 counts up, the read timer 10 counts up an internal counter in synchronization with the absolute transmission time 9 and outputs the transmission time 11 (S103). At this time, the schedule table 12
The CAM-Hit signal 13 output from is inactive.

The schedule table 12 contains the transmission time 11
CAM is searched by using as data (S104). As a result of the search, if there is corresponding data, the CAM-Hit signal 1
3 is activated (S105), and the address corresponding to the corresponding data is output as the channel number 16 (S107).

The ABR scheduler 30 has a CAM-Hi
When the t signal 13 becomes active, the transmission time is calculated (S108 in FIG. 2). Then, the switching signal 14 is set to RA
In the M state (S109 in FIG. 2), the transmission time 15 to be recorded in the schedule table 12 is output (S11).
0), the switching signal 14 is returned to the search state (S11).
1). Next, it is determined whether or not the stop signal 5 is active (S112). If it is inactive, the channel number 6 is written in the channel buffer 4 (S113). The channel buffer 4 determines the state of the internal FIFO (S1).
14) If still write to FIFO, stop signal 5
Is made inactive (S115), and if writing is not possible, it is made active (S116).

Since the data in the schedule table 12 has been rewritten by the ABR scheduler 30, the CAM is searched again using the transmission time 11 as data (S1).
04). As a result of the search, if there is applicable data, CAM
Activate the Hit signal 13 (S105), and output the address corresponding to the data as the channel number 16 (S107). Then, ABR scheduler 3
The transmission time is calculated based on 0 (S108). After this, A
The BR scheduler 30 sets the switching signal 14 to the RAM state (S109), outputs the channel number 16 and the next transmission time 15 to the schedule table 12, writes the calculation result in the CAM in the schedule table 12 (S110), Thereafter, the switching signal 14 is returned to the search state (S111). The scheduler 17 determines whether the stop signal 5 is active (S112). If active, the channel number 16 input to the scheduler 17 from the schedule table 12 is output as the channel number 6 from the ABR scheduler 30 to the channel buffer 4 (S113). Channel buffer 4
Determines the state of the FIFO (S114). If the state can be written to the FIFO, the stop signal 5 is made inactive (S115). If the state cannot be written, the stop signal 5 is made active (S116), and the process proceeds to S104.

If the corresponding data is not found in the schedule table 12, the CAM-Hit signal 13 is made inactive (S106). Next, the read timer 10 compares the absolute transmission time 9 with the transmission time 11 (S117). If the result of the comparison is a mismatch, the counter is counted up by one and the transmission time 11 is output (S118). The schedule table 12 indicates that the transmission time 11 has been counted up by one.
The CAM is searched again using the as the data (S104). If the absolute transmission time 9 is equal to the transmission time 11, the transmission timer 8 determines the cell transmission signal 2 (S101).

Next, the operation of the ABR scheduler 30 having the configuration shown in FIG. 2 will be described. FIG. 4 shows the operation of the ABR scheduler 30. The operation of the ABR scheduler 30 according to the present invention will be described with reference to the flowchart of FIG. 4 and the flowchart of FIG.

The scheduler 17 determines the stop signal 5, and
It is determined whether internal congestion has occurred (S201). If the stop signal 5 is inactive, no internal congestion has occurred and the cell of the channel number whose transmission time is the current transmission time can be transmitted, so that the transmission processing is performed. First, the channel number 20 that has become the current transmission time is output to the ACR table 18, and the current ACR2 set in the channel number 20 is output.
1 is read (S202). Next, read the current A
CR21 is output as the previous ACR19 (S20)
3). Next, the next transmission time is calculated from the current ACR 21 and the transmission time 11 (S204). Finally, the calculated transmission time is output as the transmission time 26 (S205). The transmission time 26 passes through the switch 28 and is output to the schedule table 12 as the transmission signal 15 (S206).
In the ABR table 18, the previous ACR corresponding to the channel number 20 is updated to the ACR 19 (S207).

If the stop signal 5 is active, internal congestion has occurred, so that the cell of the channel number whose transmission time is the current transmission time cannot be transmitted. Therefore, the scheduler 17
Outputs the recalculation request signal 24 to the rescheduling unit 25 to start recalculation of the ACR set for the channel and the transmission time recorded in the schedule table 12 (S208). Upon receiving the recalculation request signal 24, the rescheduling unit 25 reads the previous ACR 23 from the ACR table 18 (S209). Next, the previous transmission interval is calculated using the previous ACR 23 (S22).
210). Next, a new transmission interval is calculated from the calculated previous transmission interval (S211). Next, a new ACR is calculated from the calculated new transmission interval (S212), and the calculated ACR is used as the ACR 22 in the ACR table 18.
(S213). Next, the read timer 10
The transmission time is recalculated from the transmission time 11 given from (S214). Finally, the recalculated transmission time is output as the transmission time 27 (S215). The transmission time 26 is output as the transmission signal 15 (S216).

The ABR table 18 has a channel number 20
Is updated to the ACR 22 with the current ACR and the previous ACR corresponding to (S217). When the calculation of the transmission time is completed, the switching signal 14 is set to the RAM state (S10 in FIG. 3).
9) The channel number 16 and the next transmission time 15 are output, the calculation result is written into the CAM in the schedule table 12 (S110 in FIG. 3), and the switching signal 14 is returned to the search state (S111 in FIG. 3). The scheduler 17
The stop signal 5 is determined (S112 in FIG. 3). Stop signal 5
Is inactive, the schedule table 12
Channel number 16 output from channel number 6
(S113 in FIG. 3).

FIG. 5 shows the output time of the transmission cell and the contents of the schedule table 12 and the ACR table 18 in the ATM communication control apparatus of the present invention shown in FIG. (A)
Indicates the output time of the transmission cell. That is, ABR
The figure shows the state of cell transmission from transmission time 11 "0" when there is one service class channel and the ACR specifies to output cells in the band of "1/3". (B) shows the contents of the schedule table 12, and shows a change in the transmission time recorded in the CAM of the schedule table 12 corresponding to the output time of the transmission cell in (a). (C) shows the contents of the ACR table 18 and the current ACR recorded in the ACR table 18.
The changes in the CR and the previous ACR are shown in association with the output time in (a).

When the transmission time 11 is "0", the CAM-H
The it signal 13 becomes active and starts transmitting the transmission cell “1” as shown in FIG. At this time, since no internal congestion has occurred, the stop signal 5 is inactive. The scheduler 17 writes the channel number 6 in the channel buffer 4 and calculates the “next transmission time”. The current ACR as set in FIG.
Is "1/3", the current transmission time is "0",
The next transmission time calculated by equation (1) is “3”. In the schedule table 12, "3" is set as the "next transmission time" as shown in (b). Also, as shown in (c), “1 /
When the transmission time 11 is "3", the transmission cell "2" is processed in the same manner as when the transmission time 11 is "0". Is "6". In the schedule table 12,
As shown in (b), “6” is set as “next transmission time”. Also, as shown in (c), "1/3" is set in the previous ACR of the ACR table 18.

When the transmission time 11 is "4", internal congestion occurs and the stop signal 5 becomes active. Next, when the transmission time 11 becomes “6”, the CAM-Hit signal 13
Becomes active and attempts to process transmission cell "3". However, since internal congestion has occurred, the stop signal 5
Is active. Therefore, the scheduler 17 issues a recalculation request signal 24 to the rescheduling unit 25, and causes the rescheduling unit 25 to recalculate the ACR.
As set in FIG. 5C, the previous ACR is “１ ／”. Therefore, the previous transmission interval is “3” according to equation (2). Assuming that the interval to be delayed is “2”, the new transmission interval becomes “5” according to equation (3). Further, the new ACR becomes “１ ／” from equation (4).
As a result, (b) shows the current ACR and the previous AC
R is set to “１ ／”.

When the transmission time 11 becomes "7", the internal congestion is released and the stop signal 5 becomes inactive. When the transmission time opening 11 becomes “8”, the transmission cell “3” is processed as in the case where the transmission time 11 is “0”. This is a cell that should have been transmitted as the transmission time “6” at the time of transmitting the transmission cell “2”. "Next transmission time"
Becomes “13” (calculated by equation (1)). In the schedule table 12, "13" is set as the "next transmission time" as shown in (b). Also, as shown in (c), the previous ACR in the ACR table 18 has "1/5"
Is set. When the transmission time 11 is "13", the transmission cell "4" is processed in the same manner as when the transmission time 11 is "0". “Next transmission time” is calculated by equation (1),
It becomes "18". In the schedule table 12,
As shown in (b), “18” is set as the “next transmission time”.
Is set. In the previous ACR of the ACR table 18, "1/5" is set as shown in (c).

In the above-described embodiment, when calculating the extension of the transmission interval when the internal congestion occurs, the extension interval is fixed at "2", but may be changed by setting from the outside. Alternatively, it may be calculated from the state of the device. Further, in order to recalculate the transmission time when internal congestion occurs, the previous ACR is recorded in the ACR table 18, but this previous ACR is necessary for obtaining the transmission time 11 at which the cell was transmitted last time. Information
Transmission time 11 at which the last cell was transmitted to the ACR table 18
May be recorded and used when recalculating the transmission time. In this case, the calculation of Expression (2) becomes unnecessary, and Expression (3) for calculating the transmission time is as follows. New transmission interval = transmission time 11-transmission time recorded in ACR table + delay time interval ... (6)

Next, another embodiment of the present invention will be described. FIG. 6 shows a second embodiment of the ATM communication control device according to the present invention. FIG. 7 shows the ABR scheduler 31 of FIG.
The detailed configuration of is shown. As shown in FIG. 6, in the present embodiment, the absolute transmission time 9 output from the transmission timer 8 is A
It is input to the BR scheduler 31. This absolute transmission time 9 is input to the scheduler 17 and the rescheduling unit 25 as shown in FIG. In the ABR scheduler 31, the switch 28 is deleted as shown in FIG.

The scheduler 17 includes the channel buffer 4
And a function of calculating a “next transmission time”, and a function of outputting a recalculation request signal 24 to the rescheduling unit 25. First, channel buffer 4
The function of writing to is the same as in the above embodiment.
The function for calculating the “next transmission time” is that when the CAM-Hit signal 13 is active and the stop signal 5 is inactive, the channel number 16 output from the schedule table 12 is used as the channel number 20 in the ACR table 18. The output and the current ACR 21 are read, and the next transmission time 15 is calculated by the equation (7) using the absolute transmission time 9 output from the transmission timer 8. Next transmission time = absolute transmission time 9 + F1 (current ACR) (7)

Next, the scheduler 17 outputs the switching signal 1
4 is switched to the RAM state and the calculated next transmission time 15
Is written into the schedule table 12, and the switching signal 14 is returned to the search state. Also, the current AC used for the calculation
R21 is output as ACR19, and the previous ACR recorded in the table 18 is replaced with ACR19. CA
When the M-Hit signal 13 is active and the stop signal 5 is active, the transmission processing stops until the writing processing becomes possible. Therefore, schedule table 1
2 is not written to CAM, CAM-Hit
The signal 13 remains active and the read timer 10 stops.

Next, the function of outputting the recalculation request signal 24 to the rescheduling unit 25 of the scheduler 17 will be described. CAM-Hit signal 13 is active,
When the stop signal 5 is inactive, the scheduler 1
7 compares the absolute transmission time 9 with the transmission time 11. When the absolute transmission time 9 is not equal to the transmission time 11, that is, when the reading timer 10 is stopped due to internal congestion and the count is not incremented in synchronization with the absolute transmission time 9, a recalculation request is sent to the rescheduling unit 25. The signal 24 is output. The rescheduling unit 25 has a function of calculating a new ACR 22 with a wider transmission interval. Upon receiving the recalculation request signal 24 from the scheduler 17, A
The previous ACR 23 is read from the CR table 18 and a new ACR 22 is calculated. The recalculation is as follows.
(I) The previous transmission interval is calculated from the previous ACR 23. Previous transmission interval = F1 (previous ACR 23) (2) (ii) An interval delayed from the difference between the absolute transmission time 9 and the transmission time 11 is obtained. Delayed interval = absolute transmission time 9−transmission time 11 (8) (iii) Find a new transmission interval. New transmission interval = previous transmission interval + delayed interval (9) (iv) A new ACR 22 is calculated from the new transmission interval. New ACR22 = F2 (new transmission interval) (4) The current ACR and the previous ACR recorded in the ACR table 18 are replaced with the ACR22.

FIG. 8 shows the operation of the second embodiment of the ATM communication control apparatus according to the present invention. The operation of the ATM communication control device having the configuration shown in FIGS. 6 and 7 will be described with reference to the flowchart shown in FIG.

If the CAM-Hit signal 13 is active, the scheduler 17 judges the stop signal 5 (S
301). If the stop signal 5 is active, it means that it is in an internal congestion state, so it waits until it becomes inactive. At this time, writing to the CAM in the schedule table 12 is not performed. Since the CAM-Hit signal 13 does not become inactive, the read timer 10 is stopped.

If the stop signal 5 is inactive and the channel buffer 4 can be written, the absolute transmission time 9
And the transmission time 11 (S302). As a result of the comparison,
If they match, the channel number 20 indicating the current transmission time is output to the ACR table 18, the current ACR 21 set for the channel is read (S303), and this is output as the previous ACR 19 (S304). Next, the scheduler 17 calculates the next transmission time 15 based on the current ACR 21 and the absolute transmission time 9 (S30).
5). The ABR table 18 updates the previous ACR corresponding to the channel number 20 to the ACR 19 (S306),
All processing ends.

On the other hand, if it is determined in S302 that the absolute transmission time 9 and the transmission time 11 do not match, a recalculation request signal 24 is output to the rescheduling unit 25 to recalculate the ACR set for the channel ( S307). The rescheduling unit 25 first reads the previous ACR 23 recorded from the ACR table 18 in order to calculate a delay due to internal congestion (S308). Next, the previous transmission interval is calculated using the previous ACR 23 (S309). Further, the absolute transmission time 9 and the transmission time 11
Is calculated (S310). Next, a new transmission interval is obtained from the calculated previous transmission interval and the delayed interval (S311). Next, a new ACR is calculated from the calculated new transmission interval (S312). Next, the calculated ACR is output to the ACR table 18 as the ACR 22 (S313). The ABR table 18 updates the current ACR corresponding to the channel number 20 to the ACR 22 (S314).

FIG. 9 shows the output time of the transmission cell and the contents of the schedule table 12 and the ACR table 18 in the ATM communication control device shown in FIGS. (A)
Indicates the output time of the transmission cell. That is, ABR
FIG. 11 is a diagram illustrating a state of cell transmission from a transmission time 11 of “0” when one channel of a service class exists and a cell is specified by an ACR to output a cell in a band of “１ ／”. . (B) shows the contents of the schedule table 12, and the change of the transmission time recorded in the CAM of the schedule table 12 is made to correspond to the output time of the transmission cell of (a). (C) shows the contents of the ACR table 18 and the current ACR recorded in the ACR table 18.
And the previous ACR change corresponding to the output time of (a).

As shown in FIG. 9, the internal congestion state occurs when the absolute transmission time 9 is "4". When the absolute transmission time 9 at which the stop signal 5 becomes active becomes “6”, C
The AM-Hit signal 13 becomes active and attempts to process the transmission cell “3”. However, the stop signal 5 is active because internal congestion has occurred. The scheduler 17 suspends the processing until the stop signal 5 becomes inactive. Therefore, the reading timer 10 stops, and the transmission time 11 does not change. When the absolute transmission time 9 becomes “7”, the internal congestion is released. As a result, the stop signal 5 becomes inactive.

When the absolute transmission time 9 becomes "8", the scheduler 17 resumes the processing. The transmission cell "3" is processed in the same manner as when the transmission time 11 is "0". But,
Originally, the cell “3” is a cell that should have been transmitted at the transmission time “6” when the transmission interval was calculated at “3” when the transmission cell “2” was transmitted. However, the transmission interval has been extended to "5" due to the occurrence of internal congestion. Therefore, the scheduler 17 compares the absolute transmission time 9 with the transmission time 11. Since the difference between the two is open, a recalculation request signal 24 is issued, and the rescheduling unit 25 is activated.

The rescheduling 25 executes the recalculation of the ACR. As set in FIG. 9 (c),
The current ACR is “１ ／”, and the current transmission interval is obtained as “3” according to equation (2). Next, an interval delayed by internal congestion is calculated. The delayed transmission interval is “2” according to equation (7). Further, the new transmission interval is obtained as “5” by equation (7). In addition, a new A
CR becomes “１ ／” according to equation (4). As shown in FIG. 9C, the current ACR and the previous ACR are:
“1/5” is set. The scheduler 17 calculates the “next transmission time”. The “next transmission time” is “13” according to equation (6). As shown in FIG. 9B, “13” is newly set in the schedule table 12 as the “next transmission time”.

As described above, in the second embodiment, the transmission interval delayed due to internal congestion is calculated. If the delay interval is fixed as in the first embodiment, the ACR may be lowered more than necessary. However, according to the second embodiment, since the ACR is recalculated when transmitting a cell, the delayed interval can be accurately calculated by the AC.
R can be reflected.

[0062]

As is clear from the above, the ATM of the present invention
According to the communication control device, the internal congestion generated on the transmitting side is transmitted.
The stop signal output means detects the stop signal and generates a stop signal.
Since the transmission interval is extended by changing the ACR based on the stop signal, the ACR can be changed without delay.
When the cell transmission starts after the internal congestion is released, the actual cell transmission interval can be matched with the interval specified by the ACR.

Further, at the time of occurrence of internal congestion, the channel which has become the transmission time recalculates the transmission time and writes the new transmission time into the CAM, so that the CAM-Hit signal becomes inactive. As a result, there is no need to stop the read timer due to internal congestion, and the read timer shows the same value as the transmission timer even after internal congestion is released, and can be counted up at the same timing as the transmission timer.

Also, by calculating the transmission interval delayed due to internal congestion, the ACR is recalculated when transmitting a cell, so that the ACR is not lowered unnecessarily, and the delayed interval can be accurately calculated. It can be reflected in ACR.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a first embodiment of an ATM communication control device according to the present invention.

FIG. 2 is a block diagram illustrating a detailed configuration of an ABR scheduler in FIG. 1;

FIG. 3 is a flowchart showing the operation of the ATM communication control device of the present invention.

FIG. 4 is a flowchart illustrating an operation of the ABR scheduler of FIG. 2;

FIG. 5 is an explanatory diagram showing the output time of a transmission cell, the contents of a schedule table and an ACR table according to the first embodiment of the present invention.

FIG. 6 is a block diagram showing another embodiment of the ATM communication control device of the present invention.

FIG. 7 is a block diagram illustrating a detailed configuration of an ABR scheduler in FIG. 6;

FIG. 8 is a flowchart showing the operation of the embodiment of FIG. 6;

FIG. 9 is an explanatory diagram showing the output time of a transmission cell, the contents of a schedule table and an ACR table according to the first embodiment of the present invention.

FIG. 10 is a block diagram showing a conventional ATM communication control device.

FIG. 11 is a flowchart showing a process of the ATM communication control device of FIG. 10;

FIG. 12 is a flowchart illustrating processing subsequent to the processing in FIG. 11;

FIG. 13 is an explanatory diagram showing the execution status of transmission and the contents of a schedule table and an ACR table during normal times and when internal congestion occurs.

[Explanation of symbols]

 Reference Signs List 1 transmission unit 4 channel buffer 7 ABR scheduler 8 transmission timer 10 read timer 12 schedule table 17 scheduler 18 ACR table 25 rescheduling unit 28 switch 30, 31 ABR scheduler

Claims (6)

(57) [Claims] An allowed transmission rate after transmitting a current cell.
Based on the transmission interval corresponding to ACR (Allowed Cell Rate)
Calculate the transmission time of the next cell based on the
Is stored in the schedule table, and the schedule
In the ATM communication control device in the asynchronous transfer mode that transmits the next cell based on the table , the internal congestion state generated on the transmitting side is detected and a stop signal is output.
Transmitting side stop signal output means, and the stop signal is output even when the next cell reaches the scheduled transmission time.
Reset the ACR of the next cell when not released
An ATM communication control device, comprising: ACR resetting means . 2. A transmission unit for transmitting a cell according to a channel number and activating a cell transmission signal after transmission, counts up each time the cell transmission signal becomes active, and outputs this as an absolute transmission time. A transmission timer, a readout timer that counts the absolute transmission time and outputs the transmission time, a RAM state that stores the transmission time as data, and a schedule table that can switch a search state that searches the transmission time as data,
ACR (Allowed Cel) currently set for each channel
l Rate) is recorded, and this ACR
An ABR (Available Bit Rate) scheduler for calculating the next transmission time based on the ACR stored in the table, and a stop signal that becomes active when internal congestion occurs,
An ATM (Asynchronous Transfer Modulator) having a channel buffer for transmitting to the scheduler, reading out the channel number from the ABR scheduler, and transmitting the channel number to the transmitting unit.
e) In the communication control device, the ABR scheduler has a function of calculating the next transmission time, and a function of writing the channel number in the channel buffer, and the ABR scheduler is recorded in the ACR table when the internal congestion occurs. An ATM communication control device, comprising: a rescheduling unit that lowers an existing ACR and calculates a transmission time of the next cell from the new ACR. 3. The rescheduling unit calculates a previous transmission interval from a previous ACR, calculates a new transmission interval based on the previous transmission interval, and calculates the new ACR from a calculated value of the transmission interval. The AT according to claim 2,
M communication control device. 4. The re-scheduling unit, wherein:
The previous transmission interval is calculated using the previous ACR recorded in the R table, and the delayed interval is calculated based on the absolute transmission time from the transmission timer and the transmission time from the read timer. The ATM communication according to claim 2, further comprising a rescheduling unit that calculates a new transmission interval based on the delayed interval and the calculated previous transmission interval, and calculates the new ACR from the new transmission interval. Control device. 5. The scheduler outputs a recalculation request signal to the rescheduling unit when the stop signal from the channel buffer becomes active, and causes the rescheduling unit to calculate the new transmission time. 5. The ATM according to claim 3, wherein:
Communication control device. 6. The scheduler calculates the next transmission time based on a transmission time given from the read timer and a current ACR read from the ACR table when the internal congestion does not occur. 3. The ATM communication control device according to claim 2, wherein a transmission time is calculated from the transmission time.