JP3556522B2 - ATM communication network - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention is used for an ATM (Asynchronous Transfer Mode). The present invention is used for efficiently transferring IP (Internet Protocol) traffic over an ATM communication network.
[0002]
[Prior 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 a request from the client 30 to the server 20, and a request from the server 20 to the server 20. There is a feature that they are closely related to each other such as a response to the client 30.
[0003]
FIG. 13 is a diagram showing the flow of information in the client-server model. As shown in FIG. 13, the communication from the server 20 to the client 30 has a data amount from the client 30 to the server 20. Since the number is significantly larger than that of the above, there is a feature that congestion easily occurs. Such traffic is referred to as client-server type traffic.
[0004]
[Problems to be solved by the invention]
In contrast to such a client-server model, in a conventional ATM communication network, communication between a client and a server has been considered 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.
[0005]
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 does not occur or redundant control, for example, congestion does not occur. Control such as starting transmission at such a low rate or waiting for transmission to start for one RTT (Round Trip Time) time to secure a band is performed, and inefficient communication is performed.
[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 It is an object of the present invention to provide an ATM communication network that can efficiently transfer cells without causing congestion in client-server type traffic.
[0007]
[Means for Solving the Problems]
The applicant of the present application utilizes the characteristics of the client-server model by using the "ATM communication network" of Japanese Patent Application No. 9-326476 (not disclosed at the time of filing the application, hereinafter referred to as a prior application) 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. Then, if the desired data does not arrive 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 significantly 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 managed connections is large, the server has a large load. It becomes. However, if the client requests the transmission of the desired data again, the server does not need to manage the timer for each connection, and the processing is greatly simplified. As described above, 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.
[0008]
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.
[0009]
Here, it is a feature of the present invention that the client is a means for adding an OAM cell to the head of a series of cells going to the server for requesting the server to transmit desired data, and Means for writing possible rate information to the OAM cells, the ATM switch comprising means for managing the remaining bandwidth of the route through which the series of cells pass, and a current buffer in a buffer in which the series of cells are temporarily stored. Means for monitoring the queue length, means for managing the remaining bandwidth, and the value of the remaining bandwidth and current queue length obtained by the means for monitoring the current queue length and the rate information written in 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; and Means for writing area information to the OAM cell, the server comprising: means for reading the estimated bandwidth information written to the OAM cell; and information required by the estimated bandwidth information and the client. Means for setting a transmission rate for transferring a series of cells to a client without causing congestion according to the data size information, and transferring the series of cells to the client without causing congestion by the setting means Means for withholding data transmission when the transmission rate cannot be set.
[0010]
At this time, it is preferable that the client includes a unit for transmitting a data transmission request to the server again when the requested desired data does not arrive within a predetermined time.
[0011]
In this way, the ATM switch writes in advance a series of cells going from the client to the server with information on a band that can be used when transferring a series of cells going from the server to the client. Communication of the model can be performed smoothly. Furthermore, 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.
[0012]
Alternatively, the server may include means for transmitting, to the client, an OAM cell in which information indicating that data transmission has been withheld by the withholding means is written. 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.
[0013]
In this way, transmitting an OAM cell in which information indicating that data transmission has been withheld from the server to the client does not significantly increase the load on 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 predetermined time has elapsed after receiving the OAM cell in which the information indicating that the data transmission has been withheld is written. That is, when the OAM cell is received, only a short time has elapsed since the server detected congestion and the OAM cell was transferred to the client. By transmitting the data transmission request, the probability of avoiding congestion can be improved.
[0015]
Further, it is preferable that the client has a means for issuing an alarm when 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. . 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 withdrawn 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 cause, it is possible to notify the user of the occurrence of an abnormal situation by issuing an alarm.
[0016]
BEST MODE FOR CARRYING OUT THE INVENTION
An embodiment of the present invention will be described with reference to FIGS. 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 the 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 the 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 the 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.
[0017]
As shown in FIG. 12, the present invention is an ATM communication network including a plurality of clients 30 and a server 20, and an ATM switch 10 for connecting the server 20 and the plurality of clients 30.
[0018]
Here, the feature of the present invention is that the client 30 adds an OAM cell to the head of a series of cells going to the server 20 for requesting the server 20 to transmit desired data, and the client 30 can transmit and receive itself. As shown in FIG. 1, the ATM switch 10 writes rate information into the OAM cell, and the ATM switch 10 manages the remaining bandwidth of the route through which the series of cells pass, and temporarily stores the series of cells. Length monitoring unit 2 for monitoring the current queue length of a buffer (not shown), a remaining bandwidth management unit 3, the value of the remaining bandwidth obtained by the queue length monitoring unit 2, the current queue length, According to the rate information written in the OAM cells, a band in which a series of cells can be transferred 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. The server 20 reads the information of the estimated band written to the OAM cell as shown in FIG. And setting a transmission rate for transferring a series of cells to the client 30 without causing congestion in accordance with the information of the estimated bandwidth and the size information of the data requested from the client 30, and without causing congestion. And a determination unit 13 that withholds data transmission when the transmission rate for transferring cells to the client 30 cannot be set.
[0019]
In the first embodiment of the present invention, as shown in FIG. 7, if the requested desired data does not arrive within the predetermined time set by the timer unit 31, the client 30 sends a data transmission request to the server 20 again. It includes a data management unit 33 and a data transmission unit 32 for transmitting.
[0020]
In the second embodiment of the present invention, the determination unit 13 of the server 20 shown in FIG. 4 withholds data transmission when a transmission rate for transferring a cell to the client 30 cannot be set without causing congestion. At the same time, an OAM cell in which information indicating that data transmission has been withheld is written is transmitted to the client 30. At this time, as shown in FIG. 10, when the client 30 receives the OAM cell in which the information indicating that the data transmission has been withdrawn is written by the cell identification unit 34, the client 30 transmits the data transmission request to the server 20 again. A management unit 33 and a data transmission unit 32 are provided. The data transmission unit 32 transmits a data transmission request to the server 20 again after a predetermined time set by the timer unit 31 has elapsed after receiving the OAM cell.
[0021]
Further, the data management unit 33 issues an alarm when desired data has not arrived even though the OAM cell has not been received, thereby notifying the user of the occurrence of an abnormal situation.
[0022]
The server 20 shown in FIG. 4 includes an information reading unit 12 that reads the information of the estimated bandwidth written in the OAM cell, the information of the estimated bandwidth, and the size information of the data requested by the client 30. And a transmission data size management unit 15 and a determination unit 13 for setting a transmission rate for transferring a series of cells to the client 30 without causing congestion, and adding OAM cells to the beginning and end of the series of cells. And a transmission unit 14 for writing the information of the transmission rate in the first and last OAM cells.
[0023]
As shown in FIG. 1, the ATM switches 10-1 to 10-8 each include a cell identification unit 5 for receiving a head OAM cell and a tail OAM cell of a series of cells from the server 20 to the client 30; A band securing unit 6 for reading the information on the transmission rate written in the 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 bandwidth securing unit 6 releases the bandwidth secured according to the information on the transmission rate written in the last OAM cell.
[0024]
Next, the operation of the embodiment of the present invention will be described. As described above 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 that the server returns a response to the client in 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, if the ATM switch receives data from the client to the server, then it also receives data from the server to the client.
[0025]
Therefore, when the ATM switch receives data from the client to the server, it adds congestion information in the network to the data, and if the server transmits the data using the information, the communication from the server to the client may cause congestion. The possibility of occurrence can be kept low, and the network can be operated efficiently.
[0026]
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. In the OAM cell, the following traffic is client-server type traffic, which is an identifier CLIENT indicating that the communication is from the client 30 to the server 20, and information on a rate at which the client 30 can transmit and receive as an initial value. Is included.
[0027]
Next, when this OAM cell arrives at the ATM switch 10, the cell identification unit 1 shown in FIG. 1 determines that the cell is an OAM cell, reads the included identifier CLIENT, and reads the subsequent data. It is client-server type traffic, and it is determined that the communication is from the client 30 to the 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 for managing the remaining bandwidth of a route through which a series of cells from the client 30 to the server 20 pass, and the series of cells are temporarily stored. A series of cells can be transferred from the server 20 to the client 30 without causing congestion by estimating by referring to the value of the queue length monitoring unit 2 that monitors the queue length of the buffer (not shown) to be stored. Band information is calculated, the calculated value is compared with the value included in the band information of the OAM cell, and if the calculated value is smaller, the value is compared to the OAM cell. To write transfer to the band information.
[0028]
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 equal to or more than the upper limit value HB, “0” is written as the band information. When it is less than the upper limit value HB and larger than the lower limit value LB, the band information is R / (HB-P) / (HB-LB).
Write. Here, P: current queue length / buffer length, R: value of remaining bandwidth managed by remaining bandwidth management unit 3, HB: upper limit of (current queue length / buffer length), LB: (current queue length) Length / buffer length).
[0029]
The information writing unit 4 compares the calculated value with the value included in the bandwidth information of the OAM cell, and if the calculated value is smaller, writes the value into the bandwidth information of the OAM cell.
[0030]
In the server 20, the cell identification unit 11 shown in FIG. 4 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. The information reading unit 12 reads the band information written in the OAM cell, checks the size of the data requested by the client 30 by the transmission data size management unit 15, and divides the data size by a predetermined time T. 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.
[0031]
FIG. 5 shows a transmission rate determining algorithm in the server 20 according to the first embodiment of the present invention. If the value written in the OAM cell is equal to or more than C (the requested data size (cell) / a certain time T (second)). If (S6), the transmission rate is set to α × C (where 0 <α ≦ 1) (S7). 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).
[0032]
As shown in FIG. 6, an OAM cell is added at the beginning of the transmission data, and the OAM cell has traffic following the client-server type, which is a communication from the server 20 to the client 30. , And band information holding the transmission rate as information. An OAM cell is also provided at the end of the transmission data, and the OAM cell includes an identifier SERVER2 that is the end of the transmission data and band information for holding a transmission rate as information.
[0033]
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, reads the included identifier SERVER1, and 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, the bandwidth securing unit 6 secures a bandwidth equal to the bandwidth information included in the OAM cell. Further, when the OAM cell having the identifier SERVER2 arrives at the ATM switch 10, the band securing unit 7 releases the band securing the value equal to the band information of the arrived OAM cell.
[0034]
In the first embodiment of the present invention, as shown in FIGS. 7 and 8, the client 30 makes a data transmission request to the server 20 (S11), and then a predetermined time set by the timer unit 31 elapses. In the meantime (S12), if the desired data does not arrive from the server 20 (S13), the data management unit 33 detects this and the data transmission unit 32 sends a data transmission request to the server 20 again (S13). 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 data transmission request as necessary.
[0035]
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. 9, if the value written in the OAM cell is equal to or more than C (the requested data size (cell) / a certain time T (second)) (S15), 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 greater than the lower limit LB (S17), 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, the data is not transmitted, and the back-off request OAM cell in which the fact is written is transmitted (S19).
[0036]
In the second embodiment of the present invention, as shown in FIG. 10 and FIG. 11, the client 30 transmits a data transmission request to the server 20 (S20), and then the cell identification unit 34 does not transmit data. When the back-off request OAM cell in which the information is written is received (S21), after a predetermined time set by the timer unit 31 has elapsed (S22), the data transmission unit 32 transmits the 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 data transmission request as necessary. If data does not arrive even though the back-off request OAM cell has not been received (S23), the data management unit 33 issues an alarm (S25).
[0037]
In the first embodiment of the present invention, the processing load of the server 20 is reduced as much as possible, and the data retransmission request to the server 20 is left to the autonomous judgment of the client 30. On the other hand, 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 information indicating that data transmission is not to be performed is written. This is a slight processing load on the server 20. Accordingly, in the second embodiment of the present invention, whether the reason why data from the server 20 does not arrive is due to the server 20 detecting congestion, or a failure in the transmission path in the middle or other reasons. Can be determined on the client 30 side. Therefore, as shown in FIG. 11, if 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]
【The invention's effect】
As described above, according to the present invention, it is possible to perform cell transfer control using characteristics of the client-server model. That is, cell transfer can be efficiently performed 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 reservation 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)

In 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,
The client adds an operation and maintenance (OAM) cell to a head of a series of cells to the server for requesting the server to transmit desired data, and transmits rate information that the client can transmit and receive to the OAM. Means for writing to the cell,
The ATM switch includes means for managing a remaining bandwidth of a route through which the series of cells pass, means for monitoring a current queue length of a buffer in which the series of cells are temporarily stored, and means for managing the remaining bandwidth. And from the server to the client without causing congestion according to the value of the remaining bandwidth obtained by the means for monitoring the current queue length and the current queue length and the rate information written in the OAM cell. Means for estimating a band in which cells can be transferred, and means for writing information of the estimated band to the OAM cell,
The server is means for reading the information of the estimated bandwidth written in the OAM cell, and the client is configured not to cause congestion according to the information of the estimated bandwidth and the size information of the data requested from the client. Means for setting a transmission rate for transferring a series of cells to the client, and data transmission when the transmission rate for transferring a series of cells to the client cannot be set without causing congestion by the setting means. Means for withholding the ATM communication network. 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. In 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,
The client adds an operation and maintenance (OAM) cell to a head of a series of cells to the server for requesting the server to transmit desired data, and transmits rate information that the client can transmit and receive to the OAM. Means for writing to the cell,
The ATM switch includes means for managing a remaining bandwidth of a route through which the series of cells pass, means for monitoring a current queue length of a buffer in which the series of cells are temporarily stored, and means for managing the remaining bandwidth. And from the server to the client without causing congestion according to the value of the remaining bandwidth obtained by the means for monitoring the current queue length and the current queue length and the rate information written in the OAM cell. Means for estimating a band in which cells can be transferred, and means for writing information of the estimated band to the OAM cell,
The server is means for reading the information of the estimated bandwidth written in the OAM cell, and the client is configured not to cause congestion according to the information of the estimated bandwidth and the size information of the data requested from the client. Means for setting a transmission rate for transferring a series of cells to the client, and data transmission when the transmission rate for transferring a series of cells to the client cannot be set without causing congestion by the setting means. An ATM communication network comprising: means for withholding data, and means for transmitting, to the client, an OAM cell in which information indicating that data transmission has been withheld by the withholding means. 4. The ATM communication network according to claim 3, wherein said client further comprises means for transmitting a data transmission request to said server again when said client receives an OAM cell in which information indicating that said data transmission has been withheld. 5. The ATM communication network 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. 4. The device according to claim 3, wherein the client is configured to issue an alarm when desired data has not arrived even though an OAM cell in which information indicating that the data transmission has been withheld is not received. ATM communication network.

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