JPH1146197A - Shaping device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the sending of a cell having a high priority from being delayed later than an original sending time because of a cell having a low priority by providing a cell retrieval sending means, etc., which reads a cell from a cell buffer storing means and sends it when the cell to be sent is detected as a result of retrieval. SOLUTION: A read competitive circuit 5 retrieves a flag that shows the existence of a cell to be sent in each VC first from a real time system schedule table part 6 which has a high priority at a time outputted from a clocking part and recognizes the existence of a schedule. As a result of the retrieval, when a cell to be sent is detected, a cell of the stored VC number is read one cell after another from a cell buffer part 3 and outputted to a sending part 2. Also, when all of the VC retrieval at the time is completed, the circuit 5 waits until the clocking part outputs the next time, and when the next time is outputted, it starts retrieval at the time and subsequently repeats the operation.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a shaping device, and is applicable to, for example, an ATM communication system.

[0002]

2. Description of the Related Art At present, both network users and network service providers have encountered a problem that must be urgently solved. Large-scale and high-speed broadband data communications, which are far beyond expectations, have begun to be used. Behind this are the rapid spread of the Internet and the growing demand for LAN-to-LAN communications within companies, and the number of such network users is increasing at an unfamiliar rate.

[0003] With the increase in network users, network service providers are expected to cope with large-scale and high-speed broadband data communication that is far more than expected.
As one of the measures, ATM communication system is introduced,
We are implementing.

[0004] In the ATM communication system, in order to meet various needs of network users such as moving images, voices, characters, information data, etc., CBR is required in terms of bit rate.
(Continuous Bit Rate), VBR
(Variable BitRate), ABR (Av
available Bit Rate), UBR (Uns
(specified Bit Rate). ABR is a service class for dynamically changing a bit rate according to a congestion state of a network or the like.

[0005] Here, the data transmitted in the CBR and VBR service classes are mainly real-time data such as moving images and voices that require real-time transmission. The data transmitted in the ABR and UBR service classes is mainly non-real-time data such as characters and information data that does not require real-time transmission.

Reference 1: Kazuhiko Ishii, "What is" ABR "realizing a full-fledged ATM killer application?
・ ”, Magazine“ Computer & Network LAN ”19
April 1996 issue, pp. 38-42, Ohmsha, the shaping device described in the above-mentioned document 1 is mainly applied to an ABR service class for transmitting non-real-time data, and is a shaping device capable of coping with a change in bit rate. .

However, in practice, the shaping device is
It is necessary to cope with traffic in which real-time data and non-real-time data are mixed, and the method described in Document 1 cannot be applied as it is.

[0008] Non-real-time data can be handled in the same manner as real-time data, except that the bit rate (bandwidth limitation information) is changed for non-real-time data (particularly ABR data).

For this reason, a shaping device that handles traffic in which non-real-time data and real-time data are mixed can be considered as one that processes the traffic without discrimination. Even if the real-time data is prioritized, the real-time data is read first at the same cell transmission time.

[0010]

However, in the conventional shaping apparatus that can be considered as described above, the schedule management of all cells having different service classes on one time axis requires the existence of non-real-time data. Therefore, there is a problem that a shaping function of real-time data may be deteriorated. Hereinafter, the occurrence of this problem will be specifically described.

When a cell schedule is managed on one time axis, the transmission time determined for a cell of real-time data may be the same as the transmission time of another cell. In this case, if the other cell is a cell of real-time data, it is inevitable that real-time transmission is required, but if the other cell is a cell of non-real-time data, the urgency is low. Transmission of cells of high real-time data may be delayed from the original transmission time. Here, in the case of the same time, even if the cells of the real-time data are prioritized, the cells of the non-real-time data will be transmitted later,
Subsequent transmission of real-time data cells may be delayed from the original transmission time due to transmission of non-real-time data cells.

That is, the transmission of real-time data cells required for real-time transmission may be delayed from the original transmission time due to the presence of non-real-time data cells for which real-time transmission requirements are small. If the fluctuation of the delay (cell fluctuation) is large, it means that the shaping device is not functioning effectively.

Therefore, there is a need for a shaping device that can appropriately cope with traffic in which non-real-time data and real-time data are mixed and that does not impair real-time transmission of real-time data.

[0014]

SUMMARY OF THE INVENTION In order to solve this problem, the present invention stores an incoming cell in a cell buffer storage means, extracts an address of the incoming cell, and uses a predetermined address for the address. A shaping device that determines the transmission time of the arriving cell in accordance with the permitted band, reads out the cell from the cell buffer storage unit when the transmission time comes, and has the following units.

[0015] That is, (1) a plurality of cell transmission schedule storage means for each priority determined corresponding to the cell address, which stores the transmission time schedule of the arrival cell, and (2) the arrival cell is stored in the cell. While storing in the buffer storage means, the address of the arriving cell is extracted, and the transmission time of the arriving cell is determined according to the priority-based clock in accordance with the use permission band and priority predetermined for the address. A cell transmission schedule control means for setting a predetermined cell transmission time in the cell transmission schedule storage means having the determined and identified priority; and (3) transmitting a cell having a higher priority when a new cell transmission timing comes. The schedule storage means is searched to determine whether there is a cell to be transmitted, and the cell transmission schedule storage means having the higher priority is searched. If the cell transmission schedule cannot be retrieved from the cell buffer, the cell transmission schedule storage means having a lower priority is searched, and when a cell to be transmitted is found as a result of the search, the cell is read from the cell buffer storage means and transmitted. A search sending unit.

By configuring the present invention as described above, schedule management is performed on a time axis for each priority, so that transmission of a cell with a higher priority by a cell with a lower priority is greatly delayed from the original transmission time. Can be prevented.

[0017]

BEST MODE FOR CARRYING OUT THE INVENTION

(A) First Embodiment Hereinafter, a first embodiment of a shaping device according to the present invention will be described with reference to the drawings.

As shown in FIG. 1, a shaping device according to the first embodiment comprises a cell receiving section 1 and a cell transmitting section 2.
, A cell buffer unit 3, a management table unit 4, a read contention circuit 5, and a real-time schedule table unit 6.
And a non-real-time schedule table section 7.

The cell receiving unit 1 has a function of extracting a VC number and a priority from the header of an input cell, and refers to the management table unit 4 based on the extracted VC number and the priority to check the cell. , A function of calculating the transmission time and setting the same in the real-time schedule table section 6 or the non-real-time schedule table section 7, a function of updating the management table section 4 as necessary, and And a function to write to

In the first embodiment, a case where a cell address is managed by a VC number will be described.
Of course, it may be managed by a combination of the VC number and the VP number.

The cell transmission section 2 has a function of queuing the search result for the cell to be transmitted provided from the read contention circuit 5 in an internal output cell queue, and is queued at each new cell transmission timing. It has a function of reading and transmitting cells corresponding to the search result from the cell buffer unit 3 one by one.

The cell buffer unit 3 is a buffer for temporarily storing cells written by the cell receiving unit 1 until the cells are transmitted by the cell transmitting unit 2. Note that the cell buffer unit 3 is actually a common RAM that can be shared by each VC, so that the buffer capacity can be changed according to the need of each VC, and schematically, as shown in FIG. An image having a variable-length buffer is provided for each VC.

The management table unit 4 stores a VC number of an established connection, a minimum cell interval, a previously calculated transmission time, and a priority for each VC. As mentioned above,
This stored content is used when the cell receiving unit 1 calculates the transmission time of the input cell. The previously calculated transmission time is the transmission time calculated at the time of the previous calculation, and the transmission time calculated this time is written as the previous calculated transmission time for the next input cell of the same VC number. .

The above-mentioned minimum cell interval is used bandwidth information and is a parameter determined when a user previously declares a bandwidth, and transmits each VC cell to the network at least with an interval of this value or more. This is the setting that must be made.
The minimum cell interval is set in advance by the system for each VC. The management table unit 4 is constituted by, for example, a RAM.

The read contention circuit 5 has a function of searching for a cell to be transmitted from the real-time schedule table section 6 or the non-real-time schedule table section 7;
And a function of outputting the search result to the cell transmission unit 2.

Here, the read contention circuit 5 searches the real-time schedule table section 6 prior to the non-real-time schedule table section 7.

Real-time schedule table section 6
Is a table corresponding to a high priority, and in which a transmission time calculated by the cell receiving unit 1 is set when the current input cell is for real-time data. As shown in FIG. 1, the real-time schedule table section 6 is assigned to each VC number at each transmission time (a plurality of times constituting a sufficiently large time are circulated). A flag indicating the existence of a cell to be transmitted is set in the table. In the first embodiment, a flag "1" indicates the presence of a cell to be transmitted at the transmission time, and a flag "0" indicates that there is no cell to be transmitted at the transmission time. The real-time schedule table section 6 is constituted by, for example, a RAM.

The non-real-time schedule table section 7 corresponds to the low priority, and sets the transmission time calculated by the cell receiving section 1 when the current input cell is for non-real-time data. It is a table. The structure of the table unit 7 is the same as that of the real-time schedule table unit 6. Furthermore, the non-real-time schedule table section 7
Is constituted by the same RAM as the real-time schedule table unit 6, for example.

Further, the operation of the first embodiment composed of the above-described components will be described with reference to FIGS.

First, the write operation will be described with reference to FIG.
This will be described with reference to FIG.

When a cell is input to the cell receiving section 1 (step 100), the input cell extracts the VC number and priority from the header of the cell, and the cell buffer section 3 for each extracted VC number. (Step 10
1). Further, the cell receiving unit 1 refers to the previously calculated transmission time and the minimum cell interval of the VC number from the management table unit 4 and calculates the transmission time of the cell based on these values (step 102). The calculated transmission time is updated to the calculated transmission time, and the information of the calculated transmission time is stored in the real-time schedule table 6 when the extracted priority is high, and in the non-real-time schedule table 7 when the priority is low. It is set (step 103).

Next, the operation of the reading process will be described with reference to FIG.
This will be described with reference to FIG.

In the read contention circuit 5, the time output from the clock unit (not shown) first comes from the real-time schedule table unit 6 having the highest priority first (FIG. 1).
Then, a flag indicating the existence of a cell to be transmitted at the transmission time "A") is searched for each VC, and the presence or absence of a schedule is confirmed (step 110). The search method is, for example, a search method in the order of VC # 1, VC # 2,..., VC # n. As a result of the search, if a cell to be transmitted is detected, the VC number of the cell is output to the cell transmission unit 2 (step 111). When the search for all VCs at that time is completed (step 112),
It waits until the next time (transmission time “A + 1” in FIG. 1) is output from a clock unit (not shown), and when the next time is output, the search at that time is started, and this operation is repeated thereafter.

In the read contention circuit 5, when a cell to be transmitted is not detected at the time outputted from the clock unit (not shown), the non-real-time counter from the low-priority non-real-time schedule table unit 7 is used. The flag of the cell to be transmitted at the indicated time (the transmission time “B” in FIG. 1) is searched (step 11).
3). The search method is, for example, VC # 1, VC # 2,
.., VC # n. If a cell to be transmitted is detected as a result of the search, the VC of that cell is detected.
The number is output to cell transmitting section 2 (step 114).
When the search of all VCs at that time is completed (step 115), 1 is added to the time indicated by the counter (step 116) (in FIG. 1, the transmission time “B +
1)), when the next next time (the transmission time “A + 2” in FIG. 1) is output from a clock unit (not shown), the process returns to the search for the next next time in the real-time schedule table 6 again. That is, non-real-time cells are not transmitted until there is no cell to be transmitted to all VCs in the next real-time schedule table section 6.

In the cell transmitting section 2, when the VC number of the cell to be transmitted is input from the read contention circuit 5, the VC number is temporarily stored in an internal output cell queue. Also,
According to the time output from the clock unit (not shown), the cell of the stored VC number is set to 1 from the cell buffer unit 3.
The cells are read and transmitted one by one (step 111 or 114).

Further, an operation image of the above-described write processing and read processing will be described with reference to FIG. In FIG. 4, the VC number of the input cell is "#
x, the minimum cell interval is "5", the previously calculated transmission time is "T", and the priority is "high".

The cell receiving unit 1 extracts the VC number “#x” and the priority “high” of the input cell, and writes the input cell in the area of the cell buffer unit 3 with the VC number “#x”. It is.

In the cell receiving section 1, the previously calculated transmission time "T" of the VC number "#x" and the minimum cell interval "5" are referred from the management table section 4, and based on these, the cell is referred to. Is calculated as “T + 5”, and the previously calculated transmission time is updated to the calculated transmission time. Further, in the cell receiving unit 1, since the extracted priority is “high”, the flag of VC # x at time “T + 5” of the real-time schedule table 6 whose priority is “high” is set to “1”. Is done.

In the read contention circuit 5, when this flag is detected, the VC number "#x" of the flag is transmitted to the cell transmission unit 2.
Is output to

In the cell transmitting section 2, when the VC number “#x” is input from the read contention circuit 5, the cell buffer section 3
, A cell is read from the area of the VC number “#x”, and the cell is transmitted.

In the read competition circuit 5, the time "T +
When the table “5” is retrieved and the time “T + 6” is output from a clock unit (not shown), the time “T +
The cell to be transmitted is searched for. However, in FIG. 4, since all the flags at time “T + 6” are “0”, the process shifts to the search of the non-real-time schedule table unit 7 having the priority “low”, and the time indicated by the non-real-time counter is indicated. When a cell to be transmitted is detected, the VC number of the cell is output to the cell transmission unit 2. When all tables at the time indicated by the non-real-time counter are searched and transmission of cells to be transmitted is completed, 1 is added to the time indicated by the counter, and "T + 7" is output from a clock unit (not shown). Then, the process returns to the search for the time "T + 7" in the real-time schedule table section 6.

As described above, according to the first embodiment,
The input cells are identified as high-priority real-time data cells and low-priority non-real-time data cells, and a schedule table is provided for each priority so that scheduling can be performed on a time axis for each priority. Since the management is performed, it is possible to prevent the cell of the real-time data from being greatly delayed by the cell of the non-real-time data. Further, since cells of non-real-time data are transmitted when cells of real-time data are not transmitted, network resources can be effectively used as a whole.

(B) Second Embodiment Hereinafter, a second embodiment of a shaping device according to the present invention will be briefly described with reference to the drawings.

As shown in FIG. 5, in the second embodiment, a cell receiving unit 1, a cell transmitting unit 2, a cell buffer unit 3, a management table unit 4, a read contention circuit 5, a real-time system It comprises a schedule table section 6, a non-real-time schedule table section 7, and a cell arrival time management table section 8.

The cell arrival management table section 8 is a table in which when a cell is input to the cell receiving section 1, the cell receiving section 1 writes the arrival time of the cell for each VC.

As in the first embodiment, the read contention circuit 5 has a function of searching the real-time schedule table section 6 or the non-real-time schedule table section 7, and outputs the search result to the cell transmission section 2. And a function of deleting the arrival time of the cell to be transmitted from among the arrival times of the cells written in the cell arrival time management table section 8 and referencing it if necessary.

Reference numerals 1 to 4, 6, and 7 are the same as those of the first embodiment, and are denoted by the same reference numerals as in FIG. Therefore, it is as having described above, and the explanation here is omitted.

Therefore, the read contention circuit 5 and the cell arrival time management table section 8 will be described in detail below.

When a cell is input to the cell receiving unit 1, the cell arrival time management table unit 8
This is a table in which the arrival time of the cell is written for each VC. The cell arrival time is stored for each VC in order from the earliest arrival time. The cell arrival time is referred to by the read contention circuit 5 if necessary.
When the read conflict circuit 5 detects the VC number of the cell to be transmitted, the cell is deleted in order from the earliest arrival time of the VC number.

As in the first embodiment, the read contention circuit 5 searches the real-time schedule table section 6 or the non-real-time schedule table section 7 and, as a result of the search, detects a cell to be transmitted. The VC number of the cell is output to the cell transmission unit 2, and the cell arrival time of the cell number which is the earliest in the cell arrival time management table unit 8 is deleted. However,
As a result of the search, when cells to be transmitted to a plurality of VCs are detected at the same time, the cell arrival time management table unit 8
, The cell arrival time is referred to before the cell arrival time of the detected VC number is deleted, and the VC numbers are output to the cell transmission unit 2 in order from the earliest arrival time.

Further, the operation of the second embodiment composed of the above components will be described with reference to FIG.

In the cell receiving section 1, when a cell is input,
The VC number and the priority are extracted from the header of the input cell, and are written into the cell buffer unit 3 for each extracted VC number. In the cell receiving unit 1, the management table unit 4
, The transmission time of the cell is calculated, and the real-time schedule table section 6 or the non-real-time schedule table section 7 is set based on the calculated transmission time. Further, in the cell receiving unit 1, the input arrival time of the cell is written in the cell arrival time management table unit 8 for each VC number.

In the read contention circuit 5, first, the real-time system schedule table unit 5 having a higher priority first comes next to the time output from the clock unit (not shown) ("A + 1" in FIG. 5). The flag of the cell to be transmitted in ()) is searched for each VC, and the presence or absence of a schedule is confirmed in advance. The search method may be, for example, the search in the order of VC # 1, VC # 2,..., VC # n described in the first embodiment, or the search may be performed in any other appropriate order. . What is important in this search is to search for a transmittable cell at the next time in advance.

Further, in the read contention circuit 5, all cells to be transmitted at the next time are searched, and as a result of the search, if one cell to be transmitted is detected, the clock unit (not shown) outputs the next cell. Is output, the VC number of the detected cell is output to the cell transmitting section 2 and the VC number in the cell arrival time management table section 8 is output.
The earliest arrival time of the number is deleted, and the search for the next next time ("A + 2" in FIG. 5) is started. When a plurality of cells to be transmitted are detected as a result of the search, when the next time is output from a clock (not shown), the earliest arrival time of the VC number of the detected cell is set to the cell. The VC number of the cell is output to the cell transmission unit 2 in order from the earliest arrival time, and the cell arrival time management table unit 8 refers to the arrival time management table unit 8.
, The earliest arrival time of that VC number is deleted,
A search for the next next time (“A + 2” in FIG. 5) is started.

Further, as a result of the search, when the cell to be transmitted is not detected, the time indicated by the non-real-time counter from the non-real-time schedule table unit 7 having a low priority (transmission time "B" in FIG. 1). Are searched for the flag of the cell to be transmitted. When all cells to be transmitted at the time indicated by the counter are searched, 1 is added to the time indicated by the counter ("B + 1" in FIG. 1). The search method, the output method to the cell transmission unit 2, and the deletion method of the cell arrival time management table unit 8 are the same as those of the real-time schedule table unit 6, and the next time is output from a clock (not shown). Then, the process returns to the search for the next next time (“A + 2” in FIG. 5) in the real-time schedule table section 6 again. That is, non-real-time cells are not transmitted until there is no cell to be transmitted to all VCs in the next real-time schedule table section 6.

In the cell transmitting section 2, when the VC number of the cell to be transmitted is input from the read contention circuit 5, the VC number is temporarily stored in an internal output cell queue. Also,
According to the time output from the clock unit (not shown), the cell of the stored VC number is set to 1 from the cell buffer unit 3.
The cells are read and transmitted one by one.

As described above, according to the second embodiment,
Input cells are identified as high-priority real-time data cells and low-priority non-real-time data cells, and by having a schedule table for each priority, the time axis for each priority Since the schedule management is performed, it is possible to prevent the cell of the real-time data from being greatly delayed by the cell of the non-real-time data. Further, since cells of non-real-time data are transmitted when cells of real-time data are not transmitted, network resources can be effectively used as a whole.

Further, according to the second embodiment, when a plurality of cells to be transmitted are set at the same time as compared with the first embodiment, the arrival time of the cells to be transmitted is determined from the earlier arrival time. By transmitting the cells in order, it is possible to maintain the fairness of the cell transmission order among the real-time data.

(C) Other Embodiments In each of the above-described embodiments, cells of input data are identified as cells of high priority data and cells of low priority data. However, by adding an appropriate number of schedule tables and adding a function to identify the priority of the added schedule table, the priority can be further subdivided and processed. Each of the above embodiments can be applied even when the priority classification is increased due to the service expansion.

In the above-described embodiment, the present invention is applied to an ATM.
Although the present invention is applied to the communication system, the present invention can be applied to other communication systems employing the same cell communication method as the ATM communication system.

Furthermore, in the above embodiment, if the minimum cell interval and the priority are set in advance in the management table section, it is not necessary to extract the priority when a cell is input, and the VC number is not required. By extracting
By referring to the priority of the VC number from the management table section, the priority of the cell can be identified.

[0062]

As described above, according to the present invention, the schedule management is performed on the time axis for each priority, so that the transmission of the cell with the higher priority by the cell with the lower priority becomes shorter than the original transmission time. It is possible to prevent a large delay. In addition, a low-priority cell is transmitted when a high-priority cell is not transmitted, so that network resources can be effectively used as a whole.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a first embodiment according to the present invention.

FIG. 2 is a flowchart of a write process according to the first embodiment of the present invention.

FIG. 3 is a flowchart of a read process according to the first embodiment of the present invention.

FIG. 4 is an operation image diagram of a write process and a read process according to the first embodiment of the present invention.

FIG. 5 is a configuration diagram of a second embodiment according to the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Cell reception part, 2 ... Cell transmission part, 3 ... Cell buffer part, 4 ... Management table part, 5 ... Reading competition part, 6 ... Real-time schedule table part, 7 ... Non-real-time schedule table part.

Claims (2)

[Claims] 1. An incoming cell is stored in a cell buffer storage means, an address of the incoming cell is extracted, and a transmission time of the incoming cell is determined corresponding to a use permission band predetermined for the address. When the transmission time arrives, the shaping device that reads out the cell from the cell buffer storage means and transmits the cell, stores a transmission time schedule of the arriving cell, and stores a plurality of cells for each priority defined according to the cell address. A cell transmission schedule storing means, and storing the arriving cell in the cell buffer storing means, extracting an address of the arriving cell, and setting a priority level corresponding to a predetermined permitted band and priority for the address. The transmission time of the arriving cell is determined according to another clock, and the cell transmission schedule of the identified priority is determined. A cell transmission schedule control means for setting a predetermined cell transmission time in the storage means; and when a new cell transmission timing comes, whether or not there is a cell to be transmitted from the cell transmission schedule storage means having a higher priority. If it is not possible to search from the cell transmission schedule storage means of higher priority,
A cell search and transmission means for performing a search on the cell transmission schedule storage means having a lower priority and finding a cell to be transmitted as a result of the search, reading the cell from the cell buffer storage means and transmitting the cell; A shaping device characterized by that: 2. The cell search and transmission means further comprising: cell arrival time detection storage means for detecting an arrival time of an arrival cell by a clock corresponding to the priority of the arrival cell, and storing the detected arrival time for each address. In the present cell transmission timing, when a plurality of cells having the same priority are detected as being transmittable, the arrival time of the detected transmittable cell is referred to from the cell arrival time detection storage means, and the arrival time 2. The shaping device according to claim 1, wherein an early cell is read from said cell buffer storage means first.