JP3549766B2 - ATM communication network - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention is used for an ATM (Asynchronous Transfer Mode). INDUSTRIAL APPLICABILITY The present invention is suitable for utilizing for efficiently transmitting and receiving IP (Internet Protocol) traffic on an ATM communication network.
[0002]
[Prior art]
A conventional client-server model will be described with reference to FIG. FIG. 7 is a diagram showing a configuration example of a conventional client-server model. The communication from the clients 30-1 to 30-3 to the server 20 and the communication from the server 20 to the clients 30-1 to 30-3 are requests from the clients 30-1 to 30-3 to the server 20, and corresponding requests thereto. There is a feature that they are closely related to each other such as a response from the server 20 to the clients 30-1 to 30-3.
[0003]
FIG. 8 is a diagram showing the flow of information in the client-server model. As shown in FIG. 8, communication from the server 20 to the clients 30-1 to 30-3 has a data amount of the client 30--1. Since the amount of data from 1 to 30-3 to the server 20 is remarkably large, congestion is easily generated. 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 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.
[0008]
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 data cells, and means for writing rate information that can be transmitted and received by itself to the OAM cell, The ATM switch has means for managing the remaining bandwidth, means for monitoring the current queue length, means for managing the remaining bandwidth, and the value of the remaining bandwidth and the current queue obtained by the means for monitoring the current queue length. Means for estimating a band in which cells can be transferred from the server to the client without causing congestion in accordance with the length value and the rate information written in the OAM cell, and a bandwidth of the band estimated by the estimating means. Means for writing information to the OAM cell.
[0009]
In this manner, the ATM switch writes in advance the information of the bandwidth that can be used when transferring the packet from the server to the client that will be transmitted from the client to the server in advance. It can be done smoothly.
[0010]
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 by the client. Means for setting a transmission rate for transferring cells, means for adding OAM cells to the beginning and end of a series of data, means for writing the transmission rate information to the beginning and end OAM cells, It is desirable to provide.
[0011]
As described above, the server sets the transmission rate for transferring cells to the client according to the information on the available bandwidth written in the packet by the ATM switch, thereby setting the transmission rate without causing congestion. be able to.
[0012]
The ATM switch includes means for receiving a head OAM cell of a series of data 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, means for receiving the last OAM cell, means for reading the information on the transmission rate written in the OAM cell, and information on the transmission rate read by the reading means Means for releasing a band according to the following.
[0013]
As described above, the ATM switch secures a band in accordance with the information on the transmission rate written in the OAM cell added to the head of the packet from the server to the client, and further writes the bandwidth in the last OAM cell of the packet. By releasing the band secured according to the transmission rate information, the necessary band can be secured only during the passage of the packet, and the band can be effectively used.
[0014]
Incidentally, the applicant of the present application has developed a congestion utilizing the characteristics of the client-server model in the "ATM communication network" proposed in Japanese Patent Application No. 9-326476 (not disclosed at the time of filing the present application, hereinafter referred to as a prior application). A technique for efficiently transmitting and receiving data without causing the data to be transmitted has been disclosed. However, in the prior application, the ATM switch calculates the congestion information based on the value of the remaining bandwidth, the current queue length and the information written in the OAM cell, and the end of a series of data sent from the server to the client. When an ATM switch receives an OAM cell added to the end of a series of data from a server to a client, the ATM switch reads the information written in the OAM cell and equals the read information. No technique for releasing the band is disclosed.
[0015]
The technique applied last time is that the ATM switch calculates congestion information based on the value of the remaining bandwidth, the current queue length and the information written in the OAM cell, and the end of a series of data sent from the server to the client. The point that an OAM cell is added to the tail, and the point that when the ATM switch receives the OAM cell added to the end of a series of data from the server to the client, a band equal to the value of the band information of the OAM cell is released. Are different.
[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. 4 is a block diagram of a main part of the server according to the embodiment of the present invention.
[0017]
The present invention is an ATM communication network, as shown in FIG. 7, comprising a plurality of clients 30-1 to 30-3 and a server 20, and the server 20 and the plurality of clients 30-1 to 30- 3 is an ATM communication network including an ATM switch 10 for connecting the ATM switch 3 to an ATM switch.
[0018]
Each of the clients 30-1 to 30-3 adds an OAM cell to the head of a series of data cells, writes rate information that can be transmitted and received by itself to the OAM cell, and transfers the cell to the ATM switch 10.
[0019]
Here, a feature of the present invention is that the ATM switch 10 shown in FIG. 1 includes a remaining bandwidth management unit 3 for managing the remaining bandwidth, a queue length monitoring unit 2 for monitoring the current queue length, and a management of the remaining bandwidth. Unit 3 and the client 30-1 to the client 30-1 without causing congestion in accordance with the value of the remaining bandwidth obtained by the queue length monitoring unit 2, the current queue length value and the rate information written in the OAM cell. An information writing unit 4 for estimating a band in which cells can be transferred toward 30-3 and writing information of the estimated band to the OAM cell is provided.
[0020]
The server 20 shown in FIG. 4 includes an information reading unit 12 that reads the information of the estimated band written in the OAM cell, and a request from the information of the estimated band and the clients 30-1 to 30-3. A transmission data size management unit 15 and a determination unit 13 for setting a transmission rate for transferring cells to the clients 30-1 to 30-3 without causing congestion in accordance with the received data size information; A transmission unit 14 is provided with OAM cells at the beginning and end, and writes the information of the transmission rate into the beginning and end OAM cells.
[0021]
As shown in FIG. 1, the ATM switch 10 receives the head OAM cell of a series of data from the server 20 to the clients 30-1 to 30-3, and writes the transmission rate information written in the OAM cell. And a band securing unit 6 for securing a band according to the information on the transmission rate read by the cell identifying unit 5. Further, the cell identification unit 5 receives the last OAM cell, reads the information of the transmission rate written in the OAM cell, and the band securing unit 6 determines the band according to the read information of the transmission rate. release.
[0022]
【Example】
An embodiment of the present invention will be described with reference to FIGS. 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 diagram showing an algorithm for determining congestion information according to the embodiment of the present invention. FIG. 5 is a diagram showing a transmission rate determining algorithm according to the embodiment of the present invention. FIG. 6 is a diagram showing the structure of the first and last OAM cells from the server to the client according to the embodiment of the present invention.
[0023]
As already described with reference to FIG. 8, the characteristic of the client-server type traffic is that the server 20 responds to the requests from the clients 30-1 to 30-3 to the server 20 to the clients 30-1 to 30-3. Is returned, the communication from the clients 30-1 to 30-3 to the server 20 and the communication from the server 20 to the clients 30-1 to 30-3 are always paired.
[0024]
The amount of data transmitted from the server 20 to the clients 30-1 to 30-3 is significantly larger than the amount of data transmitted from the clients 30-1 to 30-3 to the server 20. Therefore, the network is likely to be congested by communication from the server 20 to the clients 30-1 to 30-3. That is, if the ATM switch 10 receives data from the clients 30-1 to 30-3 to the server 20, then it also receives data from the server 20 to the clients 30-1 to 30-3.
[0025]
Therefore, when the ATM switch 10 receives data from the clients 30-1 to 30-3 to the server 20, it adds congestion information in the network to the ATM switch 10 and transmits data using the information. If this is the case, the possibility that communication from the server 20 to the clients 30-1 to 30-3 will cause congestion can be reduced, and the network can be operated efficiently.
[0026]
First, when data is transmitted from the clients 30-1 to 30-3 to the server 20, as shown in FIG. 2, an OAM cell is added to the beginning of normal data. In the OAM cell, the following traffic is client-server type traffic, and it is an identifier CLIENT indicating that the traffic is from the clients 30-1 to 30-3 to the server 20; Band information including rate information that can be received by 1 to 30-3 is included.
[0027]
Next, when the 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 determined that the traffic is of the client-server type, and that the traffic is from the clients 30-1 to 30-3 to the server 20. Then, the value of the remaining bandwidth of the route through which the transmission data from the server 20 to the clients 30-1 to 30-3 passes in the reverse direction and the value of the queue length in the buffer are stored in the remaining bandwidth management unit 3, the queue length monitoring unit 2, And calculates the congestion information according to the algorithm shown in FIG.
[0028]
In the congestion information determination algorithm shown in FIG. 3, first, it is determined 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]
When an OAM cell arrives at 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 sets the subsequent data to the client / server type. Is determined to be communication from the clients 30-1 to 30-3 to the server 20. Then, the band information written in the OAM cell is read by the information reading unit 12 and sent to the determination unit 13. The server 20 checks the size of the data requested by the clients 30-1 to 30-3 by the transmission data size management unit 15, and determines a value C (cell / S) obtained by dividing the data size by a predetermined time T. Send to section 13. The determination unit 13 determines a transmission rate according to an algorithm as shown in FIG. 5, and starts transmission at that rate.
[0031]
In the transmission rate determination algorithm shown in FIG. 5, 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)) (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]
After the transmission rate is determined in this way, it is written into the OAM cell as band information. At this time, as shown in FIG. 6, an OAM cell is added to the beginning of the transmission data, and the subsequent traffic is traffic of a client server type, which is transmitted from the server 20 to the client 30-1. Identifier SERVER1 indicating that the communication is to -30 to -3, 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, which is the end of the transmission data, and band information holding the 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 clients 30-1 to 30-3. Then, the bandwidth securing unit 6 secures a bandwidth equal to the bandwidth information included in the OAM cell.
[0034]
Further, when the OAM cell having the identifier SERVER2 arrives at the ATM switch 10, the bandwidth securing unit 6 releases the bandwidth securing the value equal to the bandwidth information of the arrived OAM cell.
[0035]
【The invention's effect】
As described above, according to the present invention, when transmitting client-server type traffic over an ATM communication network, communication from the server to the client starts transmission at an appropriate rate according to the network usage. be able to. Therefore, the network can be maintained in an appropriate state without falling into a congestion state. That is, control using characteristics of the client-server model can be performed. This allows efficient cell transfer without causing congestion in the client-server model.
[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 diagram showing a congestion information determination algorithm 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 diagram showing a transmission rate determination algorithm according to the embodiment of the present invention.
FIG. 6 is a diagram showing the configuration of the first and last OAM cells from the server to the client according to the embodiment of the present invention.
FIG. 7 is a diagram showing a configuration example of a conventional client-server model.
FIG. 8 is a diagram showing a flow of information in a client-server model.
[Explanation of symbols]
1, 5, 11 Cell identification unit 2 Queue length monitoring unit 3 Remaining bandwidth management unit 4 Information writing unit 6 Bandwidth reservation unit 10, 10-1, 10-2 ATM switch 12 Information reading unit 13 Judgment unit 14 Transmission unit 15 Transmission data Size management unit 20 Server 30-1 to 30-3 Client

Claims (3)

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 includes means for providing an OAM (Operation And Maintenance) cell at the beginning of a series of data cells, and means for writing rate information that can be transmitted and received by the client to the OAM cell,
The ATM switch has a means for managing the remaining bandwidth, a means for monitoring the current queue length, a means for managing the remaining bandwidth, and a value of the remaining bandwidth and the current value obtained by the means for monitoring the current queue length. Means for estimating a band in which cells can be transferred from the server to the client without causing congestion according to a value of a queue length and rate information written in the OAM cell; and a band estimated by the estimating means. Means for writing the above information in 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 by the client. Means for setting a transmission rate for transferring cells to the cell, means for adding OAM cells to the beginning and end of a series of data, means for writing the information on the transmission rate to the beginning and end OAM cells, The ATM communication network according to claim 1, comprising: The ATM switch includes means for receiving a head OAM cell of a series of data 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 according to the information of the above, means for receiving the last OAM cell, means for reading the transmission rate information written in the OAM cell, and information for the transmission rate read by the reading means 3. The ATM communication network according to claim 2, further comprising means for releasing a band according to the following.

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