JP3556520B2 - 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. 8 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. 9 is a diagram showing the flow of information in the client-server model. As shown in FIG. 9, 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. An object of the present invention is to provide an ATM communication network in which a port of a server is not suspended for a long time due to a bottleneck in a connection via a plurality of links.
[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, according to the prior application, when cells are transferred from a server to a client via a plurality of links, the cell transmission rate is determined in consideration of the link having the smallest bandwidth among the plurality of links through the link. Had been decided. Therefore, the port of the server may be held for a long time in a small band.
[0008]
The present invention takes this point further into consideration, and the prior application technique is to provide a buffer between the server and the client and temporarily store cells in the buffer when the actual available bandwidth is small. By adding the virtual empty band generated by the above to the actual empty band, it is possible to prevent cells from being transferred in a band smaller than a predetermined value. Therefore, cells can be transferred between the server and the buffer, or between the buffers or between the buffer and the client, with a bandwidth equal to or greater than a predetermined value. As a result, it is possible to avoid a situation in which the port of the server is held for a long time in a small band. As a result, cell transfer with the highest transfer efficiency and good QoS can be realized.
[0009]
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.
[0010]
Here, the feature of the present invention is characterized in that the client includes means for adding an OAM cell to the head of a series of cells destined for the server, 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 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 management of the remaining bandwidth. 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 a series of cells can be transferred, and temporarily storing cells transferred from the server to the client. Means, and when the band estimated by the estimating means is smaller than a predetermined value, a virtual empty band newly generated by temporarily storing cells in the temporarily storing means is added to the estimated band. Means for updating the estimated band; and means for writing information on the estimated band or the band updated by the updating unit into the OAM cell.
[0011]
This makes it possible to avoid cell transfer between the server and the client in a band smaller than the predetermined value, so that it is possible to prevent a server port from being held for a long time in a small band. it can.
[0012]
It is preferable that the means for temporarily storing includes means for reading out cells stored in the means for temporarily storing in a band smaller than the arrival band.
[0013]
Thus, the cells stored in the temporary storage unit can be transmitted according to the band in which the cells can be actually transferred.
[0014]
The server reads information on the estimated band written in the OAM cell or the band updated by the updating unit; and information on the estimated band or the band updated by the updating unit. Means for setting a transmission rate for transferring cells to the client without causing congestion according to the size information of the data requested by the client, and means for providing OAM cells at the beginning and end of a series of cells And a means for writing the transmission rate information in the first and last OAM cells. The ATM switch further comprises means for receiving the first OAM cell of a series of cells from the server to the client. Means for reading the transmission rate information written in the OAM cell; Means for storing cells in the means for securing or temporarily storing the bandwidth according to the information on the transmission rate read by the means, means for receiving the last OAM cell, and means for receiving the transmission rate written in the OAM cell. It is desirable to have a means for reading information, and a means for releasing the band according to the information on the transmission rate read by the reading means when the band is secured.
[0015]
As a result, the ATM switch secures a band in accordance with the transmission rate information written in the OAM cell added to the head of the cell from the server to the client, and further transmits the transmission written in the last OAM cell of the cell. By releasing the band secured according to the rate information, the necessary band can be secured only during the passage of the cell, so that the band can be effectively used.
[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 diagram showing the overall configuration of an embodiment of the present invention. FIG. 2 is a block diagram of a main part of the ATM switch according to the embodiment of the present invention. FIG. 3 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. 4 is a flowchart showing the operation of the ATM switch according to the embodiment of the present invention. FIG. 5 is a block diagram of a main part of the server according to the embodiment of the present invention. FIG. 6 is a flowchart showing the operation of the server according to the embodiment of the present invention. FIG. 7 is a diagram showing a configuration of an OAM cell from a server to a client according to the embodiment of the present invention.
[0017]
As shown in FIG. 1, the present invention is an ATM communication network including a client 30, a server 20, and ATM switches 10-1 to 10-5 for connecting the server 20 and the client 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, writes rate information that can be transmitted and received by itself into the OAM cell, and writes the ATM switch 10- As shown in FIG. 2, reference numerals 1 to 10-5 denote a remaining band management unit 3 for managing a remaining band of a route through which the series of cells pass, and a buffer (not shown) for temporarily storing the series of cells. , A queue length monitoring unit 2 for monitoring the current queue length, a remaining bandwidth management unit 3, a value of the remaining bandwidth obtained by the queue length monitoring unit 2, a current queue length, and a rate written in the OAM cell. A control unit 4 for estimating a band in which a series of cells can be transferred from the server 20 to the client 30 without causing congestion according to the information; A buffer 8 for temporarily storing cells to be transferred toward zero, and when the estimated bandwidth is smaller than a predetermined value, the control unit 4 generates a virtual bandwidth newly generated by temporarily storing cells in the buffer 8. Is added to the estimated band to update the estimated band, and the information writing unit 5 is to write the information of the estimated band or the updated band into the OAM cell.
[0019]
The buffer 8 performs speed conversion for reading out cells stored in the buffer 8 in a band smaller than the arrival band.
[0020]
The server 20 includes, as shown in FIG. 5, an information reading unit 12 that reads information on the estimated band or the updated band written in the OAM cell, and the estimated band or the updated band. A transmission data size management unit 15 and a determination unit 13 for setting a transmission rate for transferring a cell to the client 30 without causing congestion in accordance with the information of the cell and the size information of the data requested by the client 30; And a transmitting unit 14 for adding OAM cells to the beginning and end of the OAM cell and writing the information of the transmission rate to the beginning and end OAM cells.
[0021]
Further, the ATM switches 10-1 to 10-5 receive the first OAM cell and the last OAM cell of a series of cells from the server 20 to the client 30 as shown in FIG. A cell identifying unit 6 for reading the information on the transmission rate; and a band securing unit 7 for securing a band or accumulating cells in the buffer 8 in accordance with the information on the transmission rate read from the head OAM cell by the cell identifying unit 6. When the cell identification unit 6 receives the last OAM cell, the band securing unit 7 releases the band according to the read information on the transmission rate if the band is secured.
[0022]
Next, the operation of the embodiment of the present invention will be described. As already described with reference to FIG. 9, 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, if the ATM switch receives data from the client to the server, then it also receives data from the server to the client.
[0023]
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.
[0024]
First, when transmitting data from the client 30 to the server 20 shown in FIG. 1, as shown in FIG. 3, an OAM cell is added to the beginning of normal data. 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.
[0025]
Next, when the OAM cell arrives at the ATM switch 10-1, the cell identification unit 1 shown in FIG. 2 determines that the cell is an OAM cell, reads the included identifier CLIENT, and continues the operation. It determines that the data is client-server type traffic and that it is a communication from client 30 to server 20. Then, the control unit 4 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) is determined by 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 passes, and the series of cells. The queue length of a buffer (not shown) temporarily stored is estimated by referring to the value of the queue length monitoring unit 2 which monitors the queue length, and a series of cells is transmitted from the server 20 to the client 30 without causing congestion. Is calculated. As shown in FIG. 4, when the bandwidth written in the current OAM cell is smaller than the idle bandwidth of the node (ATM switch 10-1) (S1), the control unit 4 determines whether the upstream node (ATM switch) is active. The OAM cell is sent to 10-2) (S2). If the band written in the current OAM cell is larger than the idle band of the node (ATM switch 10-1) and the band at this time is smaller than a certain threshold Bth (S1), the ATM switch At 10-1, the downlink cells are buffered in the buffer 8, thereby virtually increasing the downlink free bandwidth. With the thus obtained free band, free band information in the ATM switch 10-1 is calculated. The information writing unit 5 compares the calculated value with the value included in the band information of the OAM cell, and if the calculated value is smaller, writes and transfers the value to the band information of the OAM cell (S3).
[0026]
In the server 20, the cell identification unit 11 shown in FIG. 5 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. 6, and starts transmission at that rate.
[0027]
In the transmission rate determination algorithm shown in FIG. 6, if the value written in the OAM cell is equal to or more than C (requested data size (cell) / a certain time T (second)) (S4), the transmission rate is set to α × C (where 0 <α ≦ 1) (S5). If the value written in the OAM cell is less than C and equal to or more than the lower limit LB (S6), the transmission rate is set to α × (the value written in the OAM cell) (S7). If the value written in the OAM cell is less than C and less than the lower limit LB, no data is transmitted (S8).
[0028]
As shown in FIG. 7, 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.
[0029]
Next, when an OAM cell having the identifier SERVER1 arrives at the ATM switch 10, the cell identification unit 6 shown in FIG. 2 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 7 secures a bandwidth equal to the bandwidth information included in the OAM cell. At this time, if the bandwidth cannot be actually secured, the cells are temporarily stored in the buffer 8 to virtually secure the bandwidth. Further, if the bandwidth securing unit 7 secures the bandwidth when the OAM cell having the identifier SERVER2 arrives at the ATM switch 10, the bandwidth securing unit 7 secures a value equal to the bandwidth information of the arriving OAM cell. Release from the band you are using.
[0030]
In the example of FIG. 1, the client 30 writes 50 Mbps (Mbps is shown as M) in the OAM cell as a rate at which the client 30 can transmit and receive, and transfers it to the ATM switch 10-1. The ATM switch 10-1 calculates the rate of 30 Mbps according to the rate information of 50 Mbps written in the OAM cell and the information of the remaining bandwidth management unit 3 and the queue length monitoring unit 2, and writes this to the OAM cell. Transfer to ATM switch 10-2. Hereinafter, similarly, the data in which the OAM cell is written at the head reaches the server 20. The server 20 calculates the cell transfer band according to the information written in the arrived OAM cell.
[0031]
At this time, according to the related art, the server 20 determines the cell transfer bandwidth to be 10 Mbps or less according to the link of 10 Mbps, which is the minimum bandwidth serving as a bottleneck among the links interposed between the client 30 and the server 20. Inevitably, in the present invention, the server 20 can transfer cells to the buffer 8 provided in the ATM switch 10-4 with a transfer bandwidth of 40 Mbps. Therefore, the server 20 can quickly complete the cell transfer without suspending the cell transfer port for a long time.
[0032]
At this time, the ATM switches 10-4 and 10-2, which temporarily store cells in the buffer 8, adapt the cell transfer band to the band of the downstream link by performing speed conversion using the buffer 8. be able to. Thus, even when a plurality of links are used, smooth communication can be performed without the port of the server being held for a long time due to the bottleneck link.
[0033]
【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. In particular, it is possible to realize an ATM communication network in which a port of a server is not suspended for a long time due to a bottleneck even in a connection via a plurality of links.
[Brief description of the drawings]
FIG. 1 is a diagram showing an overall configuration of an embodiment of the present invention.
FIG. 2 is a block diagram of a main part of the ATM switch according to the embodiment of the present invention.
FIG. 3 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. 4 is a flowchart showing the operation of the ATM switch according to the embodiment of the present invention.
FIG. 5 is a block diagram of a main part of a server according to the embodiment of the present invention.
FIG. 6 is a flowchart showing the operation of the server according to the embodiment of the present invention.
FIG. 7 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. 8 is a diagram showing a communication network of a client-server model.
FIG. 9 is a diagram showing client-server type traffic.
[Explanation of symbols]
1, 6, 11 Cell identification unit 2 Queue length monitoring unit 3 Remaining bandwidth management unit 4 Control unit 5 Information writing unit 6 Cell identification unit 7 Band securing unit 8 Buffer 10, 10-1 to 10-5 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

Claims (4)

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 comprises: means for adding an OAM (Operation And Maintenance) cell to the head of a series of cells toward the server; and means for writing rate information that can be transmitted and received by the client to the OAM 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 the band in which cells can be transferred, means for temporarily storing a series of cells transferred from the server to the client, and when the band estimated by the estimating means is smaller than a predetermined value. A virtual empty band newly generated by temporarily storing cells in the temporarily storing means is added to the estimated band. Means for updating the serial estimated bandwidth, ATM communication network, comprising the means for writing bandwidth information updated by the estimated bandwidth or wherein the means for updating the OAM cell. 2. The ATM communication network according to claim 1, wherein said means for temporarily storing comprises means for reading out cells stored in said means for temporarily storing in a band smaller than its arrival band. The server is configured to read information of the estimated band written in the OAM cell or the information of the band updated by the updating unit, and information of the estimated band or the band updated by the updating unit. Means for setting a transmission rate for transferring cells to the client without causing congestion according to the size information of the data requested by the client, and means for adding OAM cells to the beginning and end of a series of cells 2. The ATM communication network according to claim 1, further comprising: means for writing the information on the transmission rate in the first and last OAM cells. The ATM switch includes means for receiving a head OAM cell of a series of cells from the server to the client, means for reading the transmission rate information written in the OAM cell, and means for reading the transmission rate read by the reading means. Means for securing a band in accordance with the information of the above or storing cells in the means for temporarily storing, means for receiving the last OAM cell, means for reading the information of the transmission rate written in this OAM cell, 4. The ATM communication network according to claim 3, further comprising means for releasing the band in accordance with the information on the transmission rate read by the reading means when the information is secured.

Images