JP3008905B2 - ABR shaper rate control method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to an ABR (Availabl)
The present invention relates to a rate control method in a shaper corresponding to (e Bit Rate), and particularly to an output cell (connection) determination method when a plurality of connections are accommodated.

[0002]

2. Description of the Related Art ABR is a service that guarantees only the quality related to discarding without guaranteeing the transmission delay, and employs a congestion control method based on feedback control. In the ABR service, CBR (Constant Bit Rat
e) A shaper is required as in the VBR (Variable Bit Rate) service. When considering the shaping operation,
In the ABR service, the transmission cell rate changes with time. For example, in a traffic shaping device for CBR and VBR as described in Japanese Patent Application Laid-Open No. 8-125668, information on a transmission cell rate of a terminal that dynamically changes is described. Therefore, there is a problem that the shaping operation corresponding to the rate change cannot be performed because the data cannot be detected.

Japanese Patent Laid-Open Publication No. Hei 8-242238 discloses that when a RM (Resource Management) cell is received and the transmission timing of a transmission VC is determined in accordance with the peak level value specified by the ATM cell, The transmission time of the transmitted VC is set to CAM (Content Addressable Memor
y) section, and describes a method in which, when the count value of the counter matches the transmission time, the VC corresponding to the address storing the coincident transmission time is determined as the transmission VC. However, in this scheme, if there are a large number of ABR connections that may be used,
An area for a connection that is not currently used must also be secured, which requires a large-capacity buffer.

[0004]

As described above, the conventional C
Since the BR shaper and the VBR shaper cannot cope with the dynamically changing ATM cell output rate of the ABR, the CB
There is a problem that an R shaper or a VBR shaper cannot be used for ABR, and the control method described in Japanese Patent Application Laid-Open No. H8-242238 requires information on all connections that may use ABR. , AB
When there are a large number of connections using R, it is necessary to have information on the connection regardless of whether it is currently used or not, and there is a problem that a large buffer is required.

An object of the present invention is to provide a shaping method for performing a cell output control corresponding to a dynamically changing ATM cell output rate in ABR.

Another object of the present invention is to reduce the amount of buffers for managing information for each connection even when there are many connections that may use ABR.

[0007]

According to the rate control method of the ABR shaper of the present invention, input cell data is stored in a buffer (cell buffer), and a cell output calculated from a cell rate for each connection determined in the source. An ideal transmission time is determined based on the interval information, and if the ideal transmission times overlap between a plurality of connections, control is performed such that the data is output in the order of registration. More specifically, means for managing the cell output interval calculated for each connection, means for calculating the ideal transmission time for each connection, and managing the ATM cell output order, and means for calculating the ideal transmission time calculated for each connection Means for outputting a cell according to the following.

Another feature is that the number of management tables for each connection can be reduced. Specifically, it has means for registering only the VCI currently in use.

According to the present invention, a dynamically changing ATM cell output rate (cell output interval) can be recognized by means for managing a cell output interval calculated for each connection, and ideal transmission is performed for each connection. Calculate the time,
The ideal output time can be determined from the cell output interval for each connection by means for managing the output order of the ATM cells. If the ideal output times overlap with a plurality of connections, the output order can be managed in the registration order. It becomes possible. Further, by means for outputting a cell in accordance with the ideal transmission time calculated for each connection, the calculated A
The TM cell output rate can be maintained.

[0010] Further, it is sufficient if there is means for registering only the VCI currently in use, and it is not necessary to have information on all connections that may use the ABR, and the buffer amount can be reduced.

[0011]

FIG. 1 is a block diagram showing an embodiment of the present invention. In FIG. 1, reference numeral 1 denotes a cell type determination unit that determines whether an input cell is valid or invalid. Data that is determined to be valid is output to a cell buffer 2, and a determination result is output to a cell buffer address management unit 3. Reference numeral 2 denotes a cell buffer for storing input valid cells, and stores the valid cells output from the cell type determination unit 1. 3 generates a write address and a read address of the cell buffer 2,
In the managing cell buffer address management unit, a read address is generated based on information from the rate control unit 4.

Reference numeral 4 denotes a rate control unit which manages a cell read time for each VCI, and determines a cell read time based on an output cell interval from the rate information processing unit 5. 5 is BRM (Backwa
(rd Resource Management) A rate information processing unit that calculates an output cell interval from information in a cell, and 6 is a BRM cell detection unit that detects a BRM cell.

FIG. 2 shows a buffer (including the cell buffer 2) managed by the rate control unit 4. Reference numeral 7 denotes a next address management buffer for storing area information in which the next cell of the same VCI is stored, corresponding to the area of the cell buffer 2. Reference numeral 8 denotes information of the cell stored in the cell buffer 2 in units of VCI. Reference numeral 9 denotes a cell output interval management buffer storing the cell output interval for each VCI.

The VCI information management buffer 8 stores a VCI
Number, Readpointer of cell buffer 2, Writepointer of next address management buffer 7, number of cells stored, ideal transmission time, head cell flag indicating that the reading order between VCIs at the same ideal transmission time is first, and similarly last And the last cell flag indicating that the VCI stores the information of the VCI to be read next.
Read next address information indicating the area of the CI information management buffer 8 is stored.

For example, for VC0, Readpointer in cell buffer 2 is area 0, Writ
“epointer” is an area 9 and indicates that the number of cells stored in the cell buffer 2 is 3. In addition, the ideal transmission times of VC0, VC8, and VC3 are all three, and the transmission order is as follows. First, the VC0 cell to which the head cell flag is attached, and then the readout address is stored at the next read address. The "area 2" is referred to, and then the VC8 cells, and then the "area 3" stored at the next read address is referred to, and the VC3 cells are ordered. Then, based on the last cell flag in the area 3, it is confirmed that there is no other cell in the cell buffer 2 where the ideal transmission time overlaps.

The VCI information management buffer 8 also stores free space information of the cell buffer 2 and stores free space management information of the cell buffer 2 and the next address management buffer 7.

Next, the operation of the embodiment of the present invention will be described.
This will be described with reference to FIG. In FIG. 1, an input cell is determined by a cell type determination unit 1 and written into a cell buffer 2. The write address to the cell buffer 2 at that time is generated by the cell buffer address management unit 3. The cell buffer address management unit 3 outputs information (write address, VCI) of the cell written in the cell buffer 2 to the rate control unit 4. Upon detecting the BRM cell, the BRM cell detection unit 6 passes the BRM cell to the rate information processing unit 5, and the rate information processing unit 5 calculates a cell output interval from the information in the BRM cell, and outputs the calculated cell output interval to the rate control unit 4.

The rate controller 4 calculates the ideal transmission time for each VCI from the input cell information and the cell output interval for each VCI, determines and manages the cell transmission time. The ideal transmission time is a time obtained by adding the cell output interval to the time at which the cell was previously transmitted. However, if the ideal transmission time is
If they overlap in, they are managed so that they are read out in the order of registration. When the cell transmission time comes, a read instruction is issued to the cell buffer address management unit 3 and the cell is output from the cell buffer 2.

FIGS. 3 and 4 are processing flowcharts when the buffer shown in FIG. 2 is used for the rate control unit 4. FIG. Hereinafter, this processing will be described. FIG. 3 is a flowchart of the processing on the writing side of the cell buffer 2 for determining the VCI to be read. In step 10, the arrival cell is checked. If it is a valid cell, the process proceeds to the next process. If it is another invalid cell, the process ends. In step 11,
The free area of the cell buffer 2 is obtained from the free area management information of the VCI information management buffer 8, and the received data is written.

At step 12, the VC of the received valid cell is
A search of the registration status of the I information is performed. (Because the VCI information management buffer 8 is assumed to be constituted by a CAM (Content Addressable Memory), the VCI is searched by the CAM search.
Search). In step 13, the new VCI of the received valid cell is registered in the VCI information management buffer 8. In step 14, output registration of the newly received VCI is performed. The reception time is set as an ideal transmission time. In step 15, a search is made as to whether the ideal transmission time overlaps with the ideal transmission time of another VCI using the ideal transmission time + the last cell flag as a search key.

In step 16, it is determined whether or not there is a search result. If there is no search result, step 17
At the same time, the start cell flag and the end cell flag are set simultaneously with the registration of the ideal transmission time (in the example of FIG. 2, VC2 and V2 are set).
C5 corresponds to this). If there is a search result, in step 18, the last cell flag of the searched data is withdrawn, and the last cell flag is set for newly registered data. In step 19, the newly registered area number is written in the next address to read the searched data.

In step 20, if the VCI is registered, the information of the next address management buffer 7 and the write pointer of the cell buffer 2 of the VCI information management buffer 8 are updated. Read of cell buffer 2 at the time of new registration
The area number written to the cell buffer 2 is written to the pointer, and the unregistered area is written to the Writepointer. Further, the information of the area of the next address management buffer 7 corresponding to the area where the received data is written to the cell buffer 2 is stored in VC
The free area management information of the I information management buffer 8 is written in the Writepointer area of the cell buffer 2. In step 21, the number of cells of the corresponding data in the VCI information management buffer 8 is updated. If the registration was originally made, 1 is added to the written number, and if not, 1 is newly written.

FIG. 4 is a flowchart of a process of reading data from the cell buffer 2 for determining the VCI to be read.
In step 2, a search for a read VCI is performed. This search is determined from the ideal transmission time of the VCI data output in the previous processing and the read next address information. If the next read address information is set, the VCI in the area indicated by that information is the read VCI. If the next read address has not been set, a search is performed using the result of adding 1 to the ideal transmission time + the head cell flag as a search key. If there is no search result, 1 is added to the ideal transmission time until it is found. Continue searching. If there is no search result even if the ideal transmission time of the search target is equal to the current cell time, the process proceeds to the next process as "no search result". In step 23, the search result of the read VCI is determined. Step 24 is a process in a case where there is no search result. Step 25 is a process in the case where there is a search result, and the head cell flag and the end cell flag of the data of the read VCI are withdrawn.

In step 26, the number of cells in the cell buffer 2 of the read VCI is checked to determine whether there is data to be read. If not, the registration of the corresponding VCI is deleted, and the process is repeated from step 22. If there is, the following processing is performed. In step 27, the read VCI cell buffer 2
, And instructs cell reading. In step 28, the read point of the VCI from which the information of the area of the next address management buffer 7 corresponding to the area of the cell buffer 2 from which the cell has been read is read.
Write as r. Also, the write of the next address management buffer of the free area management information of the VCI information management buffer 8 is performed.
The area number of the cell buffer 2 from which the cell has been read is written to the area indicated by the epointer. Further, the area number of the cell buffer 2 from which the cell has been read is also written to the Writepointer of the next address management buffer 7 of the free area management information of the VCI information management buffer 8.

In step 29, 1 is subtracted from the read cell number of the VCI to write. In step 30, the next ideal transmission time of the read VCI is determined. The cell output interval of the corresponding VCI read from the cell output interval management buffer is read and added to the current cell time to obtain an ideal transmission time. As a result, the ideal transmission time may again overlap with the ideal transmission time of another VCI.
At 35, step 1 of the write-side flow in FIG.
The same processing as 5 to 19 is performed.

FIG. 5 shows a second embodiment of the buffer managed by the rate control unit 4 of the present invention. In FIG. 5, the first cell flag, the last cell flag, and the read next address in the VCI information management buffer 8 shown in FIG. 2 are deleted. FIG. 6 shows a processing flow on the write side to the cell buffer 2 for determining the VCI to be read in this case. The processing up to step 14 in FIG. 6 is the same as the processing in FIG. Step 37 is processing for registering the determined ideal transmission time in the VCI information management buffer 36. Unlike the processing in FIG. 3, the processing in this embodiment does not use the first cell flag or the last cell flag, so that the registration is performed as it is when the ideal transmission time is determined.

FIG. 7 shows a flow of processing for reading from the cell buffer 2 for determining the VCI to be read. The processing in steps 26 to 30 is the same as the processing in FIG. In step 38, the read VCI is searched. In this process, unlike the process shown in FIG. 4, a search is performed using only the ideal transmission time as a search key. Step 3
In step 9, it is confirmed whether the ideal transmission time used for the search when there is no search result is the same value as the current cell time. In step 40, as a result of the processing in step 39, if the ideal transmission time of the search target is not the same value as the current cell time, the processing of updating the ideal transmission time of the search target is performed. In the processing in this mode, in order to determine the output VCI by searching the VCIs in the order of the registered ideal transmission time, the output VCI is maintained until the ideal transmission time to be searched becomes equal to the current cell time.
The search for the CI will be continued.

[0028]

According to the present invention, a dynamically changing AT
The cell output interval calculated from the M cell output rate is
Since the processing referred to in the er processing is performed, it is possible to cope with a dynamically changing ATM cell output rate (cell output interval).

Further, since control is performed such that only the connection in use is registered, the buffer capacity for managing information for each connection can be reduced.

[0030]

[Brief description of the drawings]

FIG. 1 is a block diagram showing an embodiment of a rate control method of an ABR shaper according to the present invention.

FIG. 2 is a diagram illustrating a buffer managed by a rate control unit 4 according to the first embodiment of the present invention.

FIG. 3 is a flowchart showing a first embodiment (a write process to a cell buffer) of a rate control method of an ABR shaper according to the present invention.

FIG. 4 is a flowchart showing a first embodiment (a process of reading from a cell buffer for determining a read VCI) of a rate control method of an ABR shaper of the present invention.

FIG. 5 is a diagram illustrating a buffer managed by a rate control unit 4 according to the second embodiment of the present invention.

FIG. 6 is a flowchart illustrating a rate control method of an ABR shaper according to a second embodiment of the present invention (write processing to a cell buffer).

FIG. 7 is a flowchart showing a second embodiment of the rate control method of the ABR shaper of the present invention (a process of reading from a cell buffer for determining a read VCI).

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Cell type determination part 2 Cell buffer 3 Cell buffer address management part 4 Rate control part 5 Rate information processing part 6 BRM cell detection part 7 Secondary address management buffer 8 VCI information management buffer 9 Cell output interval management buffer 36 Second Embodiment Information management buffer in the embodiment

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-9-121210 (JP, A) JP-A-9-214527 (JP, A) JP-A 8-242238 (JP, A) US Patent 5,338,859 US, A US Patent 5,649,110 (US, A) US Patent 5,706,288 (US, A) 1996 General Meeting of IEICE B-636 (58) Fields investigated (Int. Cl. ⁷ , DB name) H04L 12/56 H04L 12/28

Claims (3)

(57) [Claims] 1. An ATM (Asynchro) that dynamically changes according to the state of a network.
nous Transfer Mode) ABR with changing cell transmission rate
(Available Bit Rate) In the shaper in the service, only the currently used ABR connection is
VCI information management by t Addressable Memory)
A means for providing a buffer and managing connections using ABR; and a BRM (Backward Resource Manager) for each connection.
detects nt) cells, the BRM calculates the cell output interval than the cell transmission rate information in the cell, and means for managing the VCI to calculate the ideal transmission time than the cell output interval and the cell arrival time for each connection Information management buffer
Register to manage ATM cell output order and
If the ideal transmission time overlaps with another connection,
In this case, a rate control unit that outputs cells in the order of registration
Controlled by means for managing the output order of the ATM cells provided, and means for managing the output order of the ATM cells ;
An ABR shaper rate control method comprising means for outputting the arriving cell for each connection . 2. The VCI information management buffer according to claim 1, wherein:
For each VCI of the ABR connection in use,
Read area of the cell buffer that stores the
Pointer, the cell bar for storing the next input cell.
Write pointer indicating the write area of the buffer, the cell
Number of cells stored in the buffer and the ideal transmission time
2. The rate control method for an ABR shaper according to claim 1, further comprising an area for storing time information . 3. The VCI information management buffer further comprises:
First, the reading order between the VCIs at the ideal transmission time is first.
First cell flag indicating head and last
And the last cell flag indicating the VCI to be read next
Area of the VCI information management buffer in which information is stored
3. A rate control method for an ABR shaper according to claim 2, further comprising an area for storing read next address information indicating the following .