JP2000324128A - ATM communication network - Google Patents

Abstract

(57) [Problem] To perform control utilizing characteristics of a client-server model in an ATM communication network, and to efficiently transfer cells without causing congestion in client-server type traffic. SOLUTION: A client attaches an OAM cell in which rate information that can be transmitted and received by itself is written at the head of a series of cells. The ATM switch estimates a band in which a series of cells can be transferred without causing congestion, and writes the information to the OAM cell. The server sets the transmission rate for transferring the cell to the client without causing congestion according to the bandwidth information and the data size information from the OAM cell, but gives up the data transmission if the transmission rate cannot be set. Or
Alternatively, an OAM cell in which the fact is written is transmitted.
The client autonomously requests data retransmission for this.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an ATM (Asynchronou).
s Transfer Mode). The present invention is based on IP (Internet
Protocol) is used to efficiently transfer traffic on the ATM communication network.

[0002]

2. Description of the Related Art A conventional client-server model will be described with reference to FIG. FIG. 12 is a diagram showing a configuration example of a conventional client-server model. Communication from the clients 30-1 to 30-3 (hereinafter simply referred to as the client 30) to the server 20 and communication from the server 20 to the client 30 are performed by the client 30 to the server 20.
, And a response from the server 20 to the client 30 in response to the request.

FIG. 13 is a diagram showing a flow of information in a client-server model. As shown in FIG.
Since the amount of data is significantly larger than the amount of data from the client 30 to the server 20, there is a feature that congestion easily occurs. Such traffic is referred to as client-server type traffic.

[0004]

In contrast to such a client-server model, a conventional ATM communication network has considered communication between a client and a server to be completely independent of each other. For this reason, no ATM communication network utilizing the characteristics of client-server type traffic in the client-server model has been proposed.

That is, in the conventional ATM communication network, when starting communication from the server to the client, there is no information on the congestion state in the network, so that congestion may occur or redundant control such as congestion may occur. To start transmission at a low rate that does not cause
Inefficient communication is performed by performing control such as waiting for transmission to start during a TT (Round Trip Time) time.

[0006] The present invention has been made in such a background, and an object of the present invention is to provide an ATM communication network capable of performing control utilizing characteristics of a client-server model. SUMMARY OF THE INVENTION An object of the present invention is to provide an ATM communication network capable of efficiently transferring cells without causing congestion in client-server type traffic.

[0007]

[Means for Solving the Problems] The applicant of the present invention filed Japanese Patent Application No.
U.S. Pat. No. 3,326,476 (unpublished at the time of filing of the present application; hereinafter, referred to as the prior application) uses the characteristics of the client-server model without causing congestion.
We propose a technology to transfer data efficiently. However, in the prior application, when the server detects congestion, the server waits for a predetermined time before sending data. On the other hand, in the present invention, when the server detects congestion, the server gives up sending data. If the client does not receive the desired data even after waiting for a predetermined time, the client transmits a data retransmission request to the server.
As a result, the load on the server can be greatly reduced. In other words, in order for the server to send the requested data after waiting for a predetermined time, the server must manage a timer for each connection. If the number of connections to be managed is large, a large load is imposed on the server. Becomes However, if the client requests transmission of the desired data again, the server does not need to manage the timer for each connection, and the processing is greatly simplified. Thus, the present invention is different from the prior application in that the client side makes a data retransmission request autonomously. Further, when the server detects the congestion, it gives up the data transmission, but the OAM cell in which the fact is written may be transmitted to the client. In this case, upon receiving the OAM cell, the client requests the server to retransmit the data.

That is, the present invention is an ATM communication network including a plurality of clients and a server, and an ATM switch for connecting the server and the plurality of clients.

Here, a feature of the present invention is that the client assigns an OAM cell to a head of a series of cells to the server for requesting the server to transmit desired data, Means for writing rate information which can be transmitted and received by itself to the OAM cell, wherein the ATM switch manages a remaining bandwidth of a route through which the series of cells pass, and a buffer for temporarily storing the series of cells. Means for monitoring the current queue length, the means for managing the remaining bandwidth, and the value of the remaining bandwidth obtained by the means for monitoring the current queue length, the current queue length, and the rate written to the OAM cell. Means for estimating a band in which a series of cells can be transferred from the server to the client without causing congestion according to information; Wherein the information of the estimated band OAM
Means for writing to a cell, the server comprising:
Means for reading the information of the estimated bandwidth written in the M cell; and transmitting a series of cells to the client without causing congestion according to the information of the estimated bandwidth and the size information of the data requested by the client. Means for setting a transmission rate for transfer, and means for withholding data transmission if the transmission rate for transferring a series of cells to the client cannot be set without causing congestion by the setting means. It is located with.

[0010] At this time, it is preferable that the client has means for transmitting a data transmission request to the server again when the requested desired data does not arrive within a predetermined time.

As described above, the ATM switch writes in advance, in a series of cells from the client to the server, information on a band that can be used when a series of cells from the server to the client is generated. Client-server model communication can be performed smoothly. Further, as processing of the server, when congestion is detected, it is only necessary to give up data transmission, and the load on the server can be reduced.

Alternatively, the server may include means for transmitting an OAM cell in which information indicating that data transmission has been withdrawn by the withholding means is sent to the client. At this time, it is preferable that the client further includes means for transmitting a data transmission request to the server again when receiving the OAM cell in which the information indicating that the data transmission has been withheld is written.

As described above, the OA in which the server has written information to the client indicating that data transmission has been withheld.
Transmitting M cells does not add significant load to the server. By using such an OAM cell, the client can determine whether the server has not transmitted data due to detection of congestion, or whether data has not arrived at the client due to a transmission line failure or other reasons. can do. Therefore, it is possible to prevent the client from meaninglessly sending the retransmission request to the server.

[0014] Further, it is possible to include means for transmitting a data transmission request to the server again after a lapse of a predetermined time from the reception of the OAM cell in which the information indicating that the data transmission has been withheld. That is, the O
At the time when the AM cell is received, only a short time has elapsed since the server detected congestion until the OAM cell was transferred to the client. , The probability of avoiding congestion can be improved.

The client further comprises means for issuing an alarm when desired data has not arrived despite receiving no OAM cell in which information indicating that the data transmission has been withheld is written. It is desirable. That is, if the desired data has not arrived even though the OAM cell in which the information indicating that the data transmission has been withheld is not received, the desired data has not arrived because the server has detected congestion. However, since the desired data has not arrived due to some other reason, it is possible to notify the user of the occurrence of an abnormal situation by issuing an alarm.

[0016]

1 to 11 show an embodiment of the present invention.
This will be described with reference to FIG. FIG. 1 is a block diagram of a main part of an ATM switch according to an embodiment of the present invention. FIG. 2 is a diagram showing a configuration of an OAM cell from a client to a server according to an embodiment of the present invention. FIG. 3 is a flowchart showing the operation of the ATM switch according to the embodiment of the present invention. FIG. 4 is a block diagram of a main part of the server according to the embodiment of the present invention. FIG. 5 is a flowchart showing the operation of the server according to the first embodiment of the present invention.
FIG. 6 is a diagram showing a configuration of an OAM cell from a server to a client according to the embodiment of the present invention. FIG. 7 is a block diagram of a main part of a client according to the first embodiment of the present invention. FIG.
5 is a flowchart showing the operation of the client according to the first embodiment of the present invention. FIG. 9 is a flowchart showing the operation of the server according to the second embodiment of the present invention. FIG. 10 is a block diagram of a main part of a client according to the second embodiment of the present invention. FIG.
1 is a flowchart showing the operation of the client according to the second embodiment of the present invention.

The present invention comprises a plurality of clients 30 and a server 20 as shown in FIG.
1 and an ATM switch 10 for connecting the plurality of clients 30 to each other.

Here, the feature of the present invention is that the client 30 adds an OAM cell to the head of a series of cells directed to the server 20 for requesting the server 20 to transmit desired data, and The ATM switch 10 writes the transmittable / receivable rate information in the OAM cell, and as shown in FIG. 1, the ATM switch 10 manages the remaining bandwidth of the route through which the series of cells pass, and A queue length monitoring unit 2 for monitoring a current queue length of a buffer (not shown) temporarily stored; a remaining bandwidth management unit 3; a value of a remaining bandwidth obtained by the queue length monitoring unit 2; According to the length and the rate information written in the OAM cells, a band capable of transferring a series of cells from the server 20 to the client 30 without causing congestion is estimated. And an information writing unit 4 for writing the information of the estimated band to the OAM cell, and the server 20 reads the information of the estimated band written to the OAM cell as shown in FIG. The information reading unit 12 sets a transmission rate for transferring a series of cells to the client 30 without causing congestion in accordance with the information on the estimated bandwidth and the information on the size of data requested from the client 30, When the transmission rate for transferring the cell to the client 30 cannot be set without generating the data, the determination unit 13 withholds the data transmission.

In the first embodiment of the present invention, the client 30
As shown in FIG. 7, when the requested desired data does not arrive within the predetermined time set by the timer unit 31, the data management unit 33 and the data transmission unit that transmit the data transmission request to the server 20 again. 32.

In the second embodiment of the present invention, the determination unit 13 of the server 20 shown in FIG. 4 performs data transmission when the transmission rate for transferring cells to the client 30 without causing congestion cannot be set. The OAM cell in which the information indicating that the data transmission has been withdrawn is transmitted to the client 30. At this time, the client 30
As shown in FIG. 10, when the OAM cell in which the information indicating that the data transmission has been withdrawn is written by the cell identification unit 34, the data transmission request is again sent to the server 20.
Data management unit 33 and data transmission unit 32 for transmission to
Is provided. The data transmission unit 32 transmits a data transmission request to the server 20 again after a lapse of a predetermined time set by the timer unit 31 after receiving the OAM cell.

Further, the data management unit 33 includes the OAM
If the desired data has not arrived even though no cell has been received, an alarm is issued to notify the user of the occurrence of an abnormal situation.

The server 20 shown in FIG.
An information reading unit 12 for reading the information on the estimated bandwidth written in the M cell; and a client 30 that does not cause congestion according to the information on the estimated bandwidth and the size information of the data requested from the client 30.
, A transmission data size management unit 15 and a determination unit 13 for setting a transmission rate for transferring a series of cells, an OAM cell is added to the head and tail of the series of cells, and the head and tail OAM cells are added to the head and tail OAM cells. A transmission unit 14 for writing the information on the transmission rate.

The ATM switches 10-1 to 10-8
Is, as shown in FIG.
0 and O at the end of a series of cells toward
A cell identification unit 5 for receiving an AM cell; and a band securing unit 6 for reading information on the transmission rate written in the head OAM cell and securing a band according to the read information on the transmission rate. When the cell identification unit 5 receives the last OAM cell, the band securing unit 6 releases the reserved band according to the information on the transmission rate written in the last OAM cell.

Next, the operation of the embodiment of the present invention will be described. As already described with reference to FIG. 13, the characteristics of the client-server type traffic include the communication from the client to the server and the communication from the server, such as the server returning a response to the request from the client to the server. Communication to clients is always paired. At this time, the amount of data transmitted from the server to the client is significantly larger than the amount of data transmitted from the client to the server. Therefore, the network is likely to be congested by communication from the server to the client. That is, A
If the TM switch receives data from the client to the server, then it also receives data from the server to the client.

Therefore, when the ATM switch receives data from the client to the server, it adds congestion information in the network to the ATM switch, and if the server transmits the data using the information, communication from the server to the client is performed. Can reduce the possibility of causing congestion, and can operate the network efficiently.

First, when transmitting data from the client 30 to the server 20 shown in FIG. 12, an OAM cell is added to the beginning of normal data as shown in FIG. The OAM cell has an identifier CLIENT indicating that the subsequent traffic is client-server type traffic, which is a communication from the client 30 to the server 20, and the client 30 as an initial value.
Includes band information including information on rates at which transmission and reception are possible.

Next, this OAM cell is connected to the ATM switch 10.
, The cell identification unit 1 shown in FIG. 1 determines that the cell is an OAM cell and includes the identifier C
Reading LIENT determines that the data that follows is client-server type traffic, and that it is a communication from client 30 to server 20. The information writing unit 4 then temporarily stores the band information written in the OAM cell, the value of the remaining band of the route through which a series of cells from the server 20 to the client 30 pass in the reverse direction, and the series of cells. The value of the queue length in a buffer (not shown) to be processed is set to the remaining bandwidth management unit 3 that manages the remaining bandwidth of the route through which a series of cells from the client 30 to the server 20 pass, and the series of cells are temporarily stored. Buffer to be stored (not shown)
The bandwidth is estimated by referring to the value of the queue length monitoring unit 2 that monitors the queue length, and information on the band in which a series of cells can be transferred from the server 20 to the client 30 without causing congestion is calculated and calculated. The value is compared with the value included in the band information of the OAM cell. If the calculated value is smaller, the value is written to the band information of the OAM cell and transferred.

As shown in FIG. 3, the congestion information determination algorithm first determines whether (current queue length / buffer length) is equal to or more than its upper limit HB (S1).
At this time, if it is not less than the upper limit value HB, “0” is written as the band information. If the value is smaller than the upper limit value HB and larger than the lower limit value LB, R / (HB-P) / (HB-LB) is written as band information. Where P is the current queue length / buffer length, R is the value of the remaining bandwidth managed by the remaining bandwidth management unit 3, HB is the upper limit of (current queue length / buffer length),
LB: Lower limit of (current queue length / buffer length).

In the information writing section 4, the calculated value and OA
The value included in the bandwidth information of the M cell is compared, and if the calculated value is smaller, the value is written in the bandwidth information of the OAM cell.

In the server 20, the cell identification unit 1 shown in FIG.
1 determines that the cell is an OAM cell, reads the included identifier CLIENT, and the subsequent data is client-server type traffic;
And it is determined that the communication is from the client 30 to the server 20. Then, the band information written in the OAM cell is read by the information reading unit 12, the size of the data requested by the client 30 is checked by the transmission data size management unit 15, and a value obtained by dividing the size by a predetermined time T is obtained. C (cell / S) is sent to the determination unit 13. The determination unit 13 determines the transmission rate using an algorithm as shown in FIG. 5, and starts transmission according to the transmission rate.

FIG. 5 shows a transmission rate determining algorithm in the server 20 according to the first embodiment of the present invention, in which the value written in the OAM cell is C (the requested data size (cel).
l) / a certain time T (second)) or more (S6), the transmission rate is set to α × C (where 0 <α ≦ 1) (S
7). If the value written in the OAM cell is less than C and equal to or more than the lower limit LB (S8), the transmission rate is set to α × (the value written in the OAM cell) (S9). If the value written in the OAM cell is less than C and less than the lower limit LB, no data is transmitted (S10).

As shown in FIG. 6, at the beginning of transmission data, O
An AM cell is provided, and the OAM cell holds an identifier SERVER1 indicating that the subsequent traffic is client-server type traffic, which is communication from the server 20 to the client 30, and a transmission rate as information. Band information to be included. Also,
An OAM cell is also added at the end of the transmission data,
The AM cell has an identifier S that is the last of the transmitted data.
ERVER2 and band information that holds the transmission rate as information.

Next, when an OAM cell having the identifier SERVER1 arrives at the ATM switch 10, the cell identification unit 5 shown in FIG. 1 determines that the cell is an OAM cell, and reads the included identifier SERVER1. hand,
The subsequent data is client-server type traffic, and it is determined that the communication is from the server 20 to the client 30. Then, a band equal to the band information included in the OAM cell is set to the band securing
To secure. Also, an OAM having an identifier SERVER2
When the cell arrives at the ATM switch 10, the band securing unit 7 releases the band that has secured a value equal to the band information of the arrived OAM cell.

In the first embodiment of the present invention, as shown in FIGS. 7 and 8, after the client 30 makes a data transmission request to the server 20 (S11), the timer 30
During the elapse of the predetermined time set by (S12),
If the desired data does not arrive from the server 20 (S
13), the data management unit 33 detects this, and the data transmission unit 32 transmits a data transmission request to the server 20 again (S11). At this time, the data transmission request is held in the data management unit 33, and the data transmission unit 32 copies and transmits the request as necessary.

Next, a transmission rate determining algorithm in the server 20 according to the second embodiment of the present invention will be described with reference to FIG. In the second embodiment of the present invention, as shown in FIG.
If the value written in the M cell is equal to or more than C (requested data size (cell) / a certain time T (second)), (S1
5) The transmission rate is set to α × C (where 0 <α ≦ 1) (S16). If the value written in the OAM cell is less than C and equal to or more than the lower limit LB, (S1
7), the transmission rate is set to α × (the value written in the OAM cell) (S18). If the value written in the OAM cell is less than C and less than the lower limit value LB, no data is transmitted, and the back-off request OAM cell in which the fact is written is transmitted (S19).

In the second embodiment of the present invention, FIGS.
As shown in FIG. 1, after transmitting a data transmission request to the server 20 (S20), the client 30 transmits the back-off request OAM cell in which information indicating that data is not transmitted is written by the cell identification unit 34. When receiving (S2
1) After a predetermined time set by the timer unit 31 has elapsed (S22), the data transmission unit 32 transmits a data transmission request to the server 20 again (S20). At this time, the data transmission request is held in the data management unit 33, and the data transmission unit 32 copies and transmits the request as necessary. If data does not arrive even though the back-off request OAM cell has not been received (S2
3), the data management unit 33 issues an alarm (S25).

In the first embodiment of the present invention, the processing load on the server 20 is reduced as much as possible, and the data retransmission request to the server 20 is left to the client 30 for autonomous judgment. In contrast, in the second embodiment of the present invention, the server 20
Transmits to the client 30 only the back-off request OAM cell in which the information indicating that data transmission is not to be performed is written. This is a slight processing load on the server 20. Thereby, in the second embodiment of the present invention, the server 20
The client 30 can determine whether the data does not arrive from the server 30 because the server 20 has detected congestion, or because of a failure in a transmission line on the way or other reasons. Therefore, as shown in FIG. 11, when the desired data has not arrived from the server 20 even though the OAM cell of the back-off request has not been received, it is determined that some abnormal situation has occurred, and an alarm is issued. To notify the user of the occurrence of an abnormal situation.

[0038]

As described above, according to the present invention,
Cell transfer control using characteristics of the client-server model can be performed. That is, cell transfer can be performed efficiently without causing congestion in client-server type traffic.

[Brief description of the drawings]

FIG. 1 is a block diagram of a main part of an ATM switch according to an embodiment of the present invention.

FIG. 2 is a diagram showing a configuration of an OAM cell from a client to a server according to an embodiment of the present invention.

FIG. 3 is a flowchart showing the operation of the ATM switch according to the embodiment of the present invention.

FIG. 4 is a block diagram of a main part of a server according to the embodiment of the present invention.

FIG. 5 is a flowchart showing the operation of the server according to the first embodiment of the present invention.

FIG. 6 is a diagram showing a configuration of an OAM cell from a server to a client according to the embodiment of the present invention.

FIG. 7 is a block diagram of a main part of a client according to the first embodiment of the present invention.

FIG. 8 is a flowchart showing the operation of the client according to the first embodiment of the present invention.

FIG. 9 is a flowchart showing the operation of the server according to the second embodiment of the present invention.

FIG. 10 is a block diagram of a main part of a client according to a second embodiment of the present invention.

FIG. 11 is a flowchart showing the operation of the client according to the second embodiment of the present invention.

FIG. 12 is a diagram showing a communication network of a client-server model.

FIG. 13 is a diagram showing client-server type traffic.

[Explanation of symbols]

 1, 5, 11, 34 Cell identification unit 2 Queue length monitoring unit 3 Remaining bandwidth management unit 4 Information writing unit 6 Bandwidth securing unit 10, 10-1 to 10-3 ATM switch 12 Information reading unit 13 Judgment unit 14 Transmission unit 15 Transmission data size management unit 20 Server 30, 30-1 to 30-3 Client 31 Timer unit 32 Data transmission unit 33 Data management unit

Claims (6)

[Claims] 1. An ATM communication network comprising a plurality of clients and a server, and an ATM switch for connecting the server and the plurality of clients, wherein the client transmits desired data to the server. A means for providing an OAM (Operation And Maintenance) cell at the head of a series of cells toward the server for requesting, and means for writing rate information that can be transmitted and received by itself to the OAM cell, The ATM switch comprises: Means for managing the remaining bandwidth of the route through which the series of cells pass, means for monitoring the current queue length of a buffer in which the series of cells are temporarily stored, means for managing the remaining bandwidth, and the current queue Value of the remaining bandwidth obtained by the means for monitoring the length, the current queue length, and the rate information written in the OAM cell Therefore, means for estimating a band in which a series of cells can be transferred from the server to the client without causing congestion, and means for writing the information of the estimated band to the OAM cell, the server comprising: Means for reading the estimated bandwidth information written in the OAM cell; and a series of cells to the client without causing congestion according to the estimated bandwidth information and the size information of the data requested by the client. Means for setting a transmission rate for transferring a series of cells, and means for withholding data transmission when a transmission rate for transferring a series of cells to a client without causing congestion by the setting means cannot be set. An ATM communication network comprising: 2. The ATM communication network according to claim 1, wherein said client further comprises means for transmitting a data transmission request to said server again when the requested desired data does not arrive within a predetermined time. 3. An ATM communication network including a plurality of clients and a server, and an ATM switch for connecting the server and the plurality of clients, wherein the client transmits desired data to the server. A means for providing an OAM (Operation And Maintenance) cell at the head of a series of cells toward the server for requesting, and means for writing rate information that can be transmitted and received by itself to the OAM cell, The ATM switch comprises: Means for managing the remaining bandwidth of the route through which the series of cells pass, means for monitoring the current queue length of a buffer in which the series of cells are temporarily stored, means for managing the remaining bandwidth, and the current queue Value of the remaining bandwidth obtained by the means for monitoring the length, the current queue length, and the rate information written in the OAM cell Therefore, comprising means for estimating a band in which a series of cells can be transferred from the server to the client without causing congestion, and means for writing the information of the estimated band to the OAM cell, the server comprising: Means for reading the estimated bandwidth information written in the OAM cell; and a series of cells to the client without causing congestion according to the estimated bandwidth information and the size information of the data requested by the client. Means for setting a transmission rate for transferring a series of cells, and means for withholding data transmission when a transmission rate for transferring a series of cells to a client without causing congestion by the setting means cannot be set. The OAM cell in which information indicating that data transmission has been withheld by the withholding means is written to the client. ATM communication network, characterized in that a means for transmitting to the addressed cement. 4. The ATM communication system according to claim 3, wherein said client further comprises means for transmitting a data transmission request to said server again when receiving an OAM cell in which information indicating that the data transmission has been withheld is written. network. 5. The ATM according to claim 4, wherein said transmitting means includes means for transmitting a data transmission request to said server again after a predetermined time has elapsed after receiving said OAM cell.
Communication network. 6. The client includes means for issuing an alarm when desired data has not arrived despite receiving no OAM cell in which information indicating that the data transmission has been withheld is written. The ATM communication network according to claim 3.