JP2981203B2 - Cell scheduler - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to cell scheduling for determining which cell should be transmitted next in consideration of required quality for each connection or service class in an ATM network. The present invention guarantees a minimum bandwidth for a connection or service class for which the minimum bandwidth is guaranteed, and a remaining bandwidth (available bandwidth minus the sum of the minimum bandwidth of the connection or service class in communication). Related to the technology of fairly assigning. In the following description, for simplicity, only "connection" is shown, but it means "connection or service class".

[0002]

2. Description of the Related Art The following standards are cited as fairness standards for bandwidths allocated to connections in which a minimum bandwidth MCR (Minimum Cell Rate) is guaranteed (ATM Forum, "Tr.
afficManagement Specification Version 4.0 ", April 1
996).

A = sum of available bandwidths of all connections on a given link U = sum of bandwidths of bottlenecked connections on links other than a given link B = AU, given N = sum of active connections N ′ = number of active connections that are bottlenecks on links other than the given link n = N −N ′, the number of active connections that are bottlenecks on a given link M = sum of MCRs of active connections within n = B (i) = fair allocation for connection i MCR (i) = connection i Where i is an integer from 1 to n. Reference 1 Bandwidth allocation for connection Band B to the MCR
And the share obtained by removing the amount used for the MCR from the above is added.

B (i) = MCR (i) + [(BM) / n] Reference 2 The bandwidth allocation for a connection is either its MCR or the bandwidth B
Divided by n, whichever is greater.

B (i) = max (MCR (i), B / n) Reference 3 The bandwidth allocation for the connection is weighted in proportion to the MCR.

B (i) = B × (MCR (i) / M) Next, the conventional Weighted Fair Queue
A cell scheduling method called ing (WFQ) will be described. The WFQ is a control in which a fixed read ratio is provided for each connection, and a bandwidth proportional to the read ratio is assigned to each connection. Therefore, if the read ratio of each connection is made proportional to the guaranteed minimum bandwidth, the remaining bandwidth is allocated to each connection at a rate proportional to the guaranteed minimum bandwidth. For example, the available bandwidth is 12 (cell / S), the number of connections is 3,
The guaranteed minimum bandwidth of each connection is 3 (cells /
S), 2 (cell / S), 1 (cell / S), each connection always has cells to be transmitted, and if the readout ratio is 3, 2, 1, respectively, the remaining bandwidth is (12− (3 + 2 +
1)), it becomes 6 (cell / S), and the remaining bands distributed to each connection are 3 (cell / S), 2 (cell / S), and 1 (cell / S), respectively.

As described above, in the conventional FWQ, the remaining bandwidth can be distributed only at a rate proportional to the guaranteed minimum bandwidth. That is, only the above-described fairness criterion 3 can be satisfied.

A method that satisfies the above criterion 1 of fairness has been proposed (KYSiu et.al. "Virtual Queuing").
Techniques for UBR + Service in ATM With Fair Acces
s and Minimum Bandwidth Guarantee ", IEEE GLOBECOM ''
97, Nov. 1997). In the proposed method, first, a fixed time T of a fixed length such that T × MCR _i ≧ 1 is set for connection i. This means that each connection can transmit at least one cell at time T.

FIG. 13 shows a conventional cell scheduling. Conventionally, the time T is divided into two phases as shown in FIG. The first phase is the MCR guarantee phase, in which connection i is guaranteed to transmit T × MCR _i cells. The second phase is a phase for distributing the remaining bandwidth to B / n, and is scheduled by round robin or the like.

That is, connection i is T × MCR _i
Has a readout ratio equal to Then, when determining a cell to be transmitted, a cell of a connection having a read ratio of “0” or more and having a cell in the cell buffer is transmitted, and “1” is subtracted from the read ratio. If there is no connection, the cell to be transmitted is determined from connections having cells in the cell buffer by round robin. The read ratio of each connection is initialized every time T.

However, in the proposed method, T is T × M
Since the selection must be made so that CR _i ≧ 1, T may need to be changed when a connection having a low MCR starts communication halfway. This places a heavy burden on the system. To prevent this, if T is set to a large value, T × MCR _{i of the} connection with a large MCR becomes a large value, and the cells of those connections are transmitted in bursts,
This can cause performance degradation. Further, a cell scheduling method that satisfies the above criterion 2 of fairness has not been proposed.

Accordingly, the present applicants have filed Japanese Patent Application No.
No. 12,894 (not disclosed at the time of filing the present application) proposed a technique for solving this problem. The purpose of this technique is to provide a cell scheduler that can satisfy all of the above fairness criteria 1, 2, and 3 for a connection whose minimum bandwidth is guaranteed in an ATM communication network.
Still another object of the present invention is to provide a cell scheduler that can satisfy all of the above fairness criteria 1, 2, and 3 with the same system configuration.

That is, the prior application (Japanese Patent Application No. 10-01289)
No. 4) guarantees the minimum bandwidth for each connection by generating a token indicating the right to send out the connection at a time interval inversely proportional to the minimum guaranteed bandwidth for each connection. By performing the cell transmission order determination control for each connection according to the determined readout ratio, the remaining bandwidth is fairly allocated to each connection while guaranteeing the minimum bandwidth.

Various known methods can be applied to the cell transmission order determination control when a token does not exist. In such a case, the device configuration is the same.
Various methods can be applied simply by exchanging control algorithms.

[0015] On the other hand, as a technique for guaranteeing the minimum bandwidth for a connection guaranteed for a certain minimum bandwidth MCR, ATM Forum ("ATM Forum," Traffic Ma
nagement Working Group Living List, "ATMF / LTD-TM-0
1.07Dec.1997) shows the following technology as an example.

First, a cell transmitted from a user is transmitted to a UPC (Usage Parameter Control) device at the entrance of the network.
It is determined whether the CR is satisfied or not, and a cell that does not satisfy the MCR is tagged. FIG. 14 is a diagram for explaining the operation of the UPC device. As shown in FIG. 14, in the UPC device, the CPCS-PDU of AAL type 5 is used.
(Common Part Convergence Sublayer Protocol Data Un
it: The length of the CPCS-PDU is hereinafter referred to as a frame, which is twice as large as MBS (Maximum Burst Size).

Then, a token is generated for each MCR, and if the number of tokens in the bucket storing the tokens is less than MBS, the token is put in the bucket. When the number of tokens in the bucket is equal to or greater than MBS / 2, as shown in FIG. 14 (a), when the first cell constituting the frame arrives at the UPC device section, all cells constituting the frame are tagged. , The tag is added to all the cells constituting the frame if it is equal to or smaller than MBS / 2, as shown in FIG. If no tag is attached to the arriving cell, one token is removed from the bucket.

FIG. 15 is a diagram showing a relationship between a cell to which a tag is added and a cell to which no tag is added, and processing in a cell buffer in the ATM switch. In the ATM switch, as shown in FIG. 15 (a), when the first cell constituting the tagged frame arrives, if the queue length exceeds the threshold value TH1, the frame is constituted. Force discard all cells, otherwise enter buffer. Also, as shown in FIG.
When the first cell constituting the untagged frame arrives, if the queue length exceeds the threshold value TH2, all the cells constituting the frame are forcibly discarded. To enter.

[0019]

As described above, in the prior art, when a cell arrives at the ATM switch, information indicating whether or not the cell is tagged is used only when the cell is discarded. It is not used for cell scheduling directly.

However, in addition to the cell scheduling based on the required quality preset for each connection, the cell scheduling based on the priority of communication set in real time according to the situation of the remaining bandwidth that changes every moment should be considered at the same time.

For example, when a cell of a connection with a high required quality and a cell of a connection with a low required quality are mixed, a tag is added to a cell of a connection with a high required quality by the UPC device shown in FIG. It is assumed that no tag is given to a cell having a low connection. That is, it is assumed that a cell of a connection with a high required quality does not satisfy the MCR and a cell of a connection with a low required quality satisfies the required quality. In this case, since the MCR is satisfied even in a cell having a connection with a low required quality, there may be a case where a cell having a high required quality that does not satisfy the MCR has a higher priority than a cell having a high required quality. However, in the conventional cell scheduler, the presence / absence of a tag is not considered, and a cell of a connection with a high required quality has priority over a cell of a connection with a low required quality in any case. This makes it difficult to maintain fairness.

Therefore, if the pursuit of maintaining fairness is pursued, not only the cell scheduling based on the required quality preset for each connection, but also the communication priority set in real time in accordance with the situation of the remaining bandwidth that changes every moment. It is necessary to realize a cell scheduler that can simultaneously consider cell scheduling.

The present invention has been made in such a background, and it is a communication which is set in real time in accordance with the situation of the remaining bandwidth which changes with time, together with the cell scheduling based on the required quality preset for each connection. It is an object of the present invention to provide a cell scheduler that can simultaneously consider cell scheduling based on the priority of a cell. An object of the present invention is to provide a cell scheduler capable of guaranteeing the minimum bandwidth for each connection and fairly allocating the remaining bandwidth.

[0024]

According to the present invention, when a cell without an tag arrives at an ATM switch, a token for the connection having the cell that has arrived is generated, and the scheduler sends out which cell next. When deciding whether to do so, the cell to be transmitted is determined from the connection having the token, and if there is no token, the cell is transmitted from the connection having the cell in the cell buffer according to the required quality predetermined for each connection. The method is characterized in that cells are determined.

That is, according to the present invention, there are provided a plurality of cell buffers provided for each connection and storing cells classified according to the priority of communication, and a plurality of cell buffers provided from the cell buffer according to the required quality set for each connection. And a means for determining the order of transmitting cells.

Here, it is a feature of the present invention that the determining means includes means for generating a token indicating the right to send out the connection, a token buffer for storing the tokens in the order of generation, and Read control means for giving the connection a transmission right different from the token in accordance with the read ratio of the cell corresponding to the required quality; and, when there is a token in the token buffer, giving the transmission right to the connection indicated by the token and giving the token buffer Means for giving a transmission right to the connection according to the read control means when there is no token.

Preferably, the means for generating a token includes means for generating a token indicating a transmission right of the connection to a cell having a higher priority according to the priority of the communication of the cell arriving at the cell buffer. .

The read control means includes a bandwidth allocation token buffer for storing a number of bandwidth allocation tokens corresponding to the read ratio, and a connection indicated by the bandwidth allocation token at the head of the bandwidth allocation token buffer. When the transmission right is given, it is desirable that the bandwidth allocation token is re-stored at the end of the bandwidth allocation token buffer.

The read ratio may be uniform for a plurality of connections, or the read ratio may be set in proportion to the minimum guaranteed bandwidth of each of the plurality of connections.

A first and a second counter are provided for each connection, and each time a token is stored in the token buffer, there is provided means for adding the value of the first counter of the connection indicated by the token, When there is no token in the token buffer, the read control means refers to the value of the first counter of the connection to which the transmission right is to be given, and if the value is not "0", subtracts the value instead of giving the transmission right. It is preferable to include means for giving a transmission right to the connection whose first counter value is “0” and adding the value of the second counter of the connection that has given the transmission right.

The means for generating the token includes means for referring to the value of the second counter of the connection for which the token is to be generated, and when the value is not "0", subtracting the value instead of generating the token. It is desirable.

The connection corresponds to a service class, and the connection described above can be read as a service class.

With this, it is possible to simultaneously consider the cell scheduling based on the priority of communication set in real time according to the situation of the remaining bandwidth which changes every moment, in addition to the cell scheduling based on the required quality preset for each connection. Therefore,
The remaining bandwidth can be allocated fairly while guaranteeing the minimum bandwidth for each connection.

The applicant of the present application has filed a prior application (Japanese Patent Application No. 10-012).
No. 894, unpublished at the time of filing of the present application) discloses a technique that can satisfy all fairness standards cited as examples in the ATM forum with the same system configuration. However, in the earlier application,
It does not assume cell scheduling in cooperation with a UPC device, and does not disclose a technology that uses a cell to which a tag has not been added in a UPC device.

Therefore, the prior application does not mean that the ATM switch generates a token at a time interval inversely proportional to the minimum guaranteed bandwidth for each connection, but rather, when an untagged cell arrives at the ATM switch. The difference is that the token of the connection having the changed cell is generated and the token generation algorithm is simplified, so that the amount of hardware can be reduced.

[0036]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described with reference to FIGS.
This will be described with reference to FIGS. FIG. 1 is a block diagram of a main part of a cell scheduler according to a first embodiment of the present invention. FIG. 2 is a block diagram for explaining the operation of the cell scheduler according to the first embodiment of the present invention. FIG. 7 is a block diagram of a main part of a cell scheduler according to a fourth embodiment of the present invention.
FIG. 8 is a block diagram illustrating the operation of the cell scheduler according to the fourth embodiment of the present invention.

According to the present invention, as shown in FIG. 1, a plurality of cell buffers CB1 to CB1 are provided for each of the connections 1 to n and store cells classified according to the priority of communication.
The cell scheduler includes a CBn and a transmission order determination unit D that determines a transmission order of cells from the cell buffers CB1 to CBn according to the required quality set for each of the connections 1 to n.

Here, a feature of the present invention is that the transmission order determination unit D includes a token generation unit G for generating a token indicating the transmission right of the connections 1 to n, And a control unit CO which is a read control unit for giving a transmission right different from the token to the connections 1 to n in accordance with a read ratio of a cell corresponding to the required quality.
N, if there is a token in the token buffer TB1, the transmission right is given to the connection indicated by the token, and if there is no token in the token buffer TB1, the control unit C
The determination unit J is a means for giving a transmission right to the connections 1 to n in accordance with the transmission right controlled by ON.

The token generator G is provided with a cell buffer CB1
.. CBn, a token indicating the transmission right of the connection is generated to a cell having a higher priority according to the priority of the communication.

Further, as shown in FIG.
Comprises a bandwidth allocation token buffer TB2 for storing the number of bandwidth allocation tokens corresponding to the readout ratio, and the transmission right is given to the connection indicated by the bandwidth allocation token at the head of the bandwidth allocation token buffer TB2. When the bandwidth allocation token is received, the bandwidth allocation token is stored again at the end of the bandwidth allocation token buffer TB2.

The read ratio is determined for a plurality of connections 1 to n.
May be uniform, or the read ratio may be set in proportion to the minimum guaranteed bandwidth of each of the plurality of connections 1 to n.

As shown in FIGS. 7 and 8, in the fourth embodiment of the present invention, the first and second counters CU1 and CU2 are provided for each of the connections 1 to n by the counter management unit C.
U, every time a token is stored in the token buffer TB1, the value of the counter CU1 of the connection indicated by the token is incremented by "1", and the token buffer TB1
If there is no token, the control unit CON refers to the value of the counter CU1 of the connection to which the transmission right is to be given, and if the value is not "0", decrements the value by "1" instead of giving the transmission right and decrements the counter CU1. A transmission right is given to the connection whose value is "0", and the value of the counter CU2 of the connection j to which the transmission right is given is incremented by "1".

Further, the token generator G refers to the value of the counter CU2 of the connection for which a token is to be generated, and when the value is not "0", decrements the value by "1" instead of generating a token.

[0044]

DESCRIPTION OF THE PREFERRED EMBODIMENTS (First Embodiment) A first embodiment of the present invention will be described with reference to FIGS. 1 and 2 are as described above. FIG. 3 is a diagram showing an example of a cell arrival pattern for explaining the first embodiment of the present invention. FIG. 4 is a diagram showing a specific example of the transmission order determination algorithm according to the first embodiment of the present invention. FIG. 5 is a flowchart showing a token generation algorithm according to the first embodiment of the present invention. FIG. 6 is a flowchart showing the transmission order determination algorithm according to the first embodiment of the present invention.

As shown in FIG. 2, there are three connections 1 to 3 in communication, there is no token in the token buffer TB1, and the cell buffer CB of each connection 1 to 3
It is assumed that there are no cells in 1 to CB3. The cell identification unit CD
Read the VCI and CLP (Cell Loss Priority) of the arriving cell. The cell arriving from the VCI is determined to which connection cell, and the cells arriving at the cell buffers CB1 to CB3 corresponding to the connection are input.

If the CLP is "0", no tag is assigned. If the CLP is "1", a tag is assigned. Therefore, it is known whether a tag has been added to the cell arriving by the CLP. If the tag has not been added, the cell identification unit CD notifies the token generation unit G to generate a token for the connection.

When the token generation unit G receives the notification from the cell identification unit CD, it generates a token of the notified connection and inputs the generated token to the token buffer TB1. The control unit CON allocates an available bandwidth to each of the connections 1 to 3 in proportion to a weight set in advance for each of the connections 1 to 3, but here, the weights are respectively 1: 2: 1.

In the control unit CON, the number of bandwidth allocation tokens equal to the weight is stored in the bandwidth allocation token buffer TB.
2 and has bandwidth allocation tokens in order from the beginning to the end of the bandwidth allocation token buffer TB2. When the transmission order of the cells is determined by the control unit CON, if the cells are stored in the cell buffer of the connection indicated by the head band allocation token of the band allocation token buffer TB2, the cells are transmitted to the cell of the connection. Right is granted. When the transmission right is given in this manner, the head band allocation token is moved to the end of the band allocation token buffer TB2.

The judging unit J monitors the token buffer TB1, the control unit CON and the cell buffers CB1 to CB3, respectively. If there is a token in the token buffer TB1, the cell buffer CB1 to C
The cell transmission order from B3 is determined. Further, if there is no token in the token buffer TB1 even though cells are accumulated in the cell buffers CB1 to CB3, the cell buffers CB1 to CB3 are instructed according to the instruction of the control unit CON.
The cell transmission order from B3 is determined.

As a UPC device, a device for assigning a tag to each cell (ATM Forum, "Traffic Management Speci
Although a device for adding a tag in units of frames shown in FIG. 14 and fication Version 4.0, "April 1996) has been proposed so far, either device can be used in the present invention.

As shown in FIG. 4A, tokens have not yet been stored in the token buffer TB1. At this time, as shown in FIG.
, A cell with no tag arrives, and connections 2 and 3 arrive with cells to which a tag has been added. The cell identification unit CD identifies the arriving cell and grasps this situation. Subsequently, the cell identification unit CD notifies the token generation unit G to generate a connection 1 token, and the token generation unit G generates a connection 1 token.

At t = 2, as shown in FIG. 4B, since the token of the connection 1 is at the head of the token buffer TB1, the judgment unit J sends out the cell of the connection 1 and removes the used token.

At t = 2, as shown in FIG. 3, a cell having no tag attached to connection 2 arrives.
A cell with a tag attached to connections 1 and 3 arrives. The cell identification unit CD identifies the arriving cell and grasps this situation. The cell identification unit CD notifies the token generation unit G to generate a connection 2 token, and the token generation unit G generates a connection 2 token.

At t = 3, as shown in FIG. 4C, since the token of the connection 2 is at the head of the token buffer TB1, the judgment unit J sends out the cell of the connection 2 and removes the used token.

At t = 3, as shown in FIG. 3, a cell having no tag attached to connection 3 arrives.
A cell with a tag attached to connections 1 and 2 arrives. The cell identification unit CD identifies the arriving cell and grasps this situation. The cell identification unit CD notifies the token generation unit G to generate a connection 3 token, and the token generation unit G generates a connection 3 token.

At t = 4, as shown in FIG. 4D, since the token of the connection 3 is at the head of the token buffer TB1, the judgment unit J sends out the cell of the connection 3, and removes the used token.

At t = 4, as shown in FIG. 3, cells with tags attached to connections 1 to 3 arrive. The cell identification unit CD identifies the arriving cell and grasps this situation. The cell identification unit CD does not notify the token generation unit G because a cell to which no tag has been added has not arrived.

At t = 5, as shown in FIG. 4 (e), since there is no token in the token buffer TB1, the determination unit J determines the cell transmission order according to the instruction of the control unit CON. In the control unit CON, the token buffer T for band allocation
Since the first bandwidth allocation token of B2 is for connection 1, and connection 1 has cells in cell buffer CB1, it instructs determination unit J to transmit the cells of connection 1. The bandwidth allocation token of the connection 1 used is a bandwidth allocation token buffer TB2.
And the bandwidth allocation tokens of the connections 2, 3, 2, 1 are arranged in order from the top as shown in FIG. 4 (f).

At t = 5, as shown in FIG. 3, a cell without a tag arrives at connections 2 and 3, and a cell with a tag arrives at connection 1. The cell identification unit CD identifies the arriving cell and grasps this situation. The cell identification unit CD notifies the token generation unit G to generate tokens for the connections 2 and 3, and the token generation unit G generates tokens for the connections 2 and 3.

At t = 5, as shown in FIG. 4 (f), since the token of the connection 2 is at the head of the token buffer TB1, the judgment unit J sends out the cell of the connection 2 and removes the used token. Further, since the token of the connection 3 comes to the head of the token buffer TB1, the cell of the connection 3 is transmitted, and the used token is removed.

As shown in FIG. 5, the token generation algorithm of the token generation unit G is such that when a cell to which a tag of connection i is not added arrives at the ATM switch (S
1) Generate a token for connection i (S2).

As shown in FIG. 6, when the token is present in the token buffer TB1 (S3), the scheduling algorithm of the judging unit J sends out the cell of the connection having the first token of the token buffer TB1 (S3).
4). There is no token in the token buffer TB1 (S
3) If there is a cell in the cell buffer (S5), the control unit C
The cell to be transmitted is determined according to the ON instruction (S
6). If there is no cell in the cell buffer, no cell is transmitted (S7).

(Second Embodiment) The difference between the second embodiment of the present invention and the first embodiment of the present invention resides in that the reading ratio preset by the control unit CON is set to "1" uniformly. Therefore, a specific operation can be easily inferred from that described in the first embodiment of the present invention, and a description thereof will be omitted. The method of equally allocating the available bandwidth for each connection is not limited to the method of the second embodiment of the present invention, and a known method such as round robin may be used. By performing such control, it is possible to allocate a band to each connection so as to satisfy the above-described fairness criterion 1.

(Third Embodiment) The difference between the third embodiment of the present invention and the first embodiment of the present invention is that the read ratio preset in the control unit CON is proportional to the guaranteed minimum bandwidth of each connection. The place to set things. Therefore, a specific operation can be easily inferred from that described in the first embodiment of the present invention, and a description thereof will be omitted. As a method of allocating an available band in proportion to a predetermined readout ratio, many control methods have already been proposed, and any control method may be used in the third embodiment of the present invention. By performing such control, it is possible to perform band allocation that satisfies the above-described fairness criterion 3 for each connection.

(Fourth Embodiment) A fourth embodiment of the present invention will be described with reference to FIGS. 7 and 8 are as described above. FIG. 9 is a diagram showing an example of a cell arrival pattern for explaining the fourth embodiment of the present invention. FIG. 10 is a diagram showing a specific example of the transmission order determination algorithm according to the fourth embodiment of the present invention. FIG. 11 is a flowchart showing a token generation algorithm according to the fourth embodiment of the present invention. FIG. 12 is a flowchart showing the transmission order determination algorithm according to the fourth embodiment of the present invention.

It is assumed that the connections 1 to 3 are in communication, the token buffer TB1 has no token, and the cell buffers CB1 to CB3 of the connections 1 to 3 have no cells. Also, the counter CU of all connections 1 to 3
1, the counter CU2 is set to "0".

The cell discriminating unit CD stores the VCI of the arriving cell.
And CLP are read. The cell arriving from the VCI is identified as the cell of the connection, and the cell arriving at the cell buffer corresponding to the connection is input. CLP
If “0”, no tag is assigned, and if “1”, a tag is assigned. Therefore, CLP
You can see if the tag has been added to the cell that arrived,
If no tag is assigned, the cell identification unit CD notifies the token generation unit G to generate a token for the connection.

When the token generation unit G receives the notification from the cell identification unit CD, the token generation unit G reads the counter CU of the counter management unit CU.
1 and CU2, and counters CU1 and CU2
Determines whether to generate a connection token according to the value of. The control unit CON allocates a bandwidth that can be used equally for each connection for each connection.

In the control unit CON, one band allocation token is arranged in the band allocation token buffer TB2 for each connection, and the band allocation token buffer TB
2 has a bandwidth allocation token in order from the beginning to the end. If the control unit CON determines the cell transmission order, the bandwidth allocation token buffer TB2
Are stored in the cell buffer of the connection indicated by the leading bandwidth allocation token, and the transmission right is given to the cell of the connection when the value of the counter CU1 of the connection is "0". When the transmission right is given in this manner, the head band allocation token is moved to the end of the band allocation token buffer TB2.

The judgment unit J monitors the token buffer TB1, the control unit CON and the cell buffers CB1 to CB3, respectively. If there is a token in the token buffer TB1, the cell buffer CB1 to C
The cell transmission order from B3 is determined. If there is no token in the token buffer TB1, the order of transmitting cells from the cell buffers CB1 to CB3 is determined according to the instruction of the control unit CON.

As a UPC device, a device for assigning a tag to each cell (ATM Forum, "Traffic Management Speci
Although a device for adding a tag to each frame shown in FIG. 14 and fication Version 4.0, "April 1996) has been proposed so far, either device can be used in the present invention.

As shown in FIG. 10A, tokens have not yet been stored in the token buffer TB1. Connections 1 to 3 (illustrated as CN1 to CN3)
Counters CU1 and CU2 are “0”. At this time, as shown in FIG. 9, at t = 1, a cell without a tag attached to connection 1 arrives and connection 2
At 3 and 3, a cell with a tag arrives. The cell identification unit CD identifies the arriving cell and grasps this situation. The cell identification unit CD notifies the token generation unit G to generate a connection 1 token, and the token generation unit G generates a connection 1 token. Further, the value of the counter CU1 of the connection 1 is incremented by "1".

At t = 2, as shown in FIG.
Since the token of the connection 1 is at the head of the token buffer TB1, the determination unit J sends out the cell of the connection 1 and removes the used token.

At t = 2, as shown in FIG. 9, a cell having no tag attached to connection 2 arrives.
A cell with a tag attached to connections 1 and 3 arrives. The cell identification unit CD identifies the arriving cell and grasps this situation. The cell identification unit CD notifies the token generation unit G to generate a connection 2 token, and the token generation unit G generates a connection 2 token. Further, the value of the counter CU1 of the connection 2 is incremented by "1".

At t = 3, as shown in FIG.
Since the token of the connection 2 is at the head of the token buffer TB1, the determination unit J sends out the cell of the connection 2 and removes the used token.

At t = 3, as shown in FIG. 9, cells with tags attached to connections 1 to 3 arrive. The cell identification unit CD identifies the arriving cell and grasps this situation. The cell identification unit CD does not notify the token generation unit G because a cell to which no tag has been added has not arrived.

At t = 5, as shown in FIG.
Since there is no token in the token buffer TB1, the determination unit J determines the cell transmission order according to the instruction of the control unit CON. In the control unit CON, the first band allocation token of the band allocation token buffer TB2 is that of the connection 1, and the connection 1 is the cell buffer CB1.
, The cell of connection 1 is a transmission candidate. When the value of the counter CU1 of the connection 1 is recognized as "1" by referring to the value of the counter CU1 of the counter management unit CU, the value of the counter CU1 is decremented by "1" without transmitting a cell. . Then, the used bandwidth allocation token of the connection 1 moves to the end of the bandwidth allocation token buffer TB2.

Thus, the bandwidth allocation token of connection 2 comes to the head of the bandwidth allocation token buffer TB2. The connection 2 is a cell buffer CB2
, The connection 2 cell is a transmission candidate. Here, when the value of the counter CU2 of the connection 2 is recognized as “1” by referring to the value of the counter CU1 of the counter management unit CU, the value of the counter CU1 is decremented by “1” without transmitting the cell. . Then, the used bandwidth allocation token of the connection 2 moves to the end of the bandwidth allocation token buffer TB2.

Thus, the bandwidth allocation token of connection 3 comes to the head of the bandwidth allocation token buffer TB2. The connection 3 is a cell buffer CB3
, The cell of connection 3 is a transmission candidate. Here, by referring to the value of the counter CU1 of the counter management unit CU and recognizing that the value of the counter CU1 of the connection 3 is "0", the cell of the connection 3 is transmitted. Then, the connection 3 of the counter CU2
Is added to "1", and the used bandwidth allocation token of connection 3 moves to the end of the bandwidth allocation token buffer TB2.

At t = 4, as shown in FIG. 9, a cell without a tag arrives at connections 2 and 3 and a cell with a tag arrives at connection 1. The cell identification unit CD identifies the arriving cell and grasps this situation. The cell identification unit CD notifies the token generation unit G to generate the tokens of the connections 2 and 3. At this time, the token generator G
Is generated, but for connection 3,
Since the value of the counter CU2 is "1", no token is generated and "1" is subtracted from the value of the counter CU2.

At t = 4, as shown in FIG.
Since the token of the connection 2 is at the head of the token buffer TB1, the determination unit J sends out the cell of the connection 2 and removes the used token.

As shown in FIG. 11, when the untagged cell of the connection i arrives at the ATM switch (S8), the value of the counter CU2 of the connection i is set to "1". If it is larger than "0" (S9), "1" is subtracted from the value of the counter CU2 (S11). If the value of the counter CU2 of the connection i is "0" (S9), a token of the connection i is generated, and "1" is added to the value of the counter CU1 (S10).

As shown in FIG. 12, the cell scheduling algorithm of the judgment section J is based on the token buffer TB1.
If there is a token (S12), the token buffer TB
The cell of the connection having the first token is transmitted (S13). If there is no token in the token buffer TB1 (S12), a cell to be transmitted is determined by round robin (S14). If the value of the determined connection counter CU1 is "0" (S15), the cell of the determined connection is transmitted and the counter C
"1" is added to the value of U2 (S17). If the value of the counter CU1 of the determined connection is not "0" (S15), "1" is subtracted from the counter CU1 (S15).
16).

[0084]

As described above, according to the present invention,
In addition to the cell scheduling based on the required quality preset for each connection, the cell scheduling based on the priority of communication set in real time according to the situation of the remaining bandwidth that changes every moment can be considered at the same time. As a result, the remaining bandwidth can be allocated fairly while guaranteeing the minimum bandwidth for each connection.

[Brief description of the drawings]

FIG. 1 is a block diagram of a main part of a cell scheduler according to a first embodiment of the present invention.

FIG. 2 is a block diagram for explaining the operation of the cell scheduler according to the first embodiment of the present invention.

FIG. 3 is a diagram showing an example of a cell arrival pattern for explaining the first embodiment of the present invention.

FIG. 4 is a diagram showing a specific example of a transmission order determination algorithm according to the first embodiment of the present invention.

FIG. 5 is a flowchart showing a token generation algorithm according to the first embodiment of the present invention.

FIG. 6 is a flowchart showing a transmission order determination algorithm according to the first embodiment of the present invention.

FIG. 7 is a block diagram of a main part of a cell scheduler according to a fourth embodiment of the present invention.

FIG. 8 is a block diagram illustrating the operation of a cell scheduler according to a fourth embodiment of the present invention.

FIG. 9 is a diagram showing an example of a cell arrival pattern for explaining a fourth embodiment of the present invention.

FIG. 10 is a diagram showing a specific example of a sending order determination algorithm according to a fourth embodiment of the present invention.

FIG. 11 is a flowchart illustrating a token generation algorithm according to a fourth embodiment of the present invention.

FIG. 12 is a flowchart showing a sending order determination algorithm according to a fourth embodiment of the present invention.

FIG. 13 is a diagram showing conventional cell scheduling.

FIG. 14 is a diagram for explaining the operation of the UPC device.

FIG. 15 is a diagram showing a relationship between a cell to which a tag is added, a cell to which no tag is added, and processing in a cell buffer in the ATM switch.

[Explanation of symbols]

 1 to n connection CB1 to CBn cell buffer CD cell identification unit CON control unit CU counter management unit CU1, CU2 counter D transmission order determination unit G token generation unit J determination unit TB1 token buffer TB2 bandwidth allocation token buffer

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-9-93256 (JP, A) JP-A-5-83284 (JP, A) JP-A-4-94237 (JP, A) JP-A-11-93 215142 (JP, A) IEICE Technical Report SSE 97-166 IEICE Technical Report SSE 98-1 (58) Fields investigated (Int. Cl. ⁶ , DB name) H04L 12/28 H04L 12 / 56 H04J 3/00-3/26

Claims (7)

(57) [Claims] 1. Priority of communication provided for each connection
Cells that accumulate cells classified according to
Buffer and the required products set for each connection
Sending order of cells from the cell buffer according to quality
And a means for determining the transmission right of the connection.
Means for generating tokens and the order in which they are generated
A token buffer to store according to the order and the request
The connection according to the cell readout ratio corresponding to the quality
Read control to give the application a sending right different from the token
Means and when there is a token in said token buffer
Gives transmission right to the connection indicated by the token and
When there is no token in the token buffer,
Grants the transmission right to the connection according to the control means
With means, The means for generating the token arrives at the cell buffer.
Priority of the incoming cell according to the priority of said communication
Token indicating the transmission right of the connection to the higher
Including means for generating A cell schedule characterized by the following:
La. 2. The bandwidth control apparatus according to claim 2, wherein said read control means includes a bandwidth allocation token buffer for storing a number of bandwidth allocation tokens corresponding to said read ratio, and indicates a bandwidth allocation token at the head of said bandwidth allocation token buffer. 2. The cell scheduler according to claim 1, wherein when the transmission right is given to the connection, the bandwidth allocation token is re-stored at the end of the bandwidth allocation token buffer. 3. A process according to claim 1 or 2 cell scheduler, wherein said read ratio and uniform for a plurality of connections. Wherein said read ratio cell scheduler of claim 1 or <br/> other 2 wherein is set in proportion to their minimum guaranteed bandwidth of the plurality of connections. (5)Communication priority provided for each connection
Cells that accumulate cells classified according to
Buffer and the required products set for each connection
Sending order of cells from the cell buffer according to quality
And a means for determining The determining means indicates a transmission right of the connection.
Means for generating tokens and the order in which they are generated
A token buffer to store according to the order and the request
The connection according to the cell readout ratio corresponding to the quality
Read control to give the application a sending right different from the token
Means and when there is a token in said token buffer
Gives transmission right to the connection indicated by the token and
When there is no token in the token buffer,
Grants the transmission right to the connection according to the control means
And means,  First and second counters are provided for each connection
Every time a token is stored in the token buffer.
The first count of the connection indicated by this token.
Means for adding the value of the
When there is no token, the reading control means
The value of the first counter of the connection to give
Refers to and gives the right to send when the value is not "0".
Instead, the value is subtracted and the value of the first counter is set to "0".
Given a transmission right to the connection that is
Means for adding the value of the second counter of the connection
includingCharacterized byCell scheduler. 6. The means for generating a token refers to a value of the second counter of a connection in which a token is to be generated, and when the value is not "0", subtracts the value instead of generating a token. The cell scheduler according to claim 5, comprising: 7. A cell scheduler according to any one of claims 1 to 6 wherein the connection corresponding to the service class.