JP3556521B2 - 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. 9 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. 10 is a diagram showing the flow of information in the client-server model. As shown in FIG. 10, the communication from the server 20 to the client 30 has a data amount of 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 earlier application, the route between the client and the server is proposed as unique. The present invention proposes a technique in which a plurality of routes between a client and a server are proposed, and an optimum route is selected from the plurality of routes. As a result, cell transfer with the highest transfer efficiency and good QoS can be realized using a plurality of routes.
[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, 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 means for writing information of the estimated band to the OAM cell. Means for reading the information of the estimated bandwidth written in the OAM cell for each of the OAM cells arriving from a plurality of routes, information of the estimated bandwidth collected within a predetermined time, 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 requested from the plurality of routes, and the transmission set by the setting means. Means for selecting one of the plurality of routes according to a rate, means for adding OAM cells to the head and tail of a series of cells, and means for selecting the head and tail OAM cells. Means for writing information on the transmission rate of the route.
[0010]
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. Further, the server can improve the utilization efficiency of the route over the entire network by selecting the optimal route according to the information of the OAM cells arriving from the plurality of routes.
[0011]
At this time, the selecting unit is configured to include a unit that selects a route having the maximum transmission rate among the plurality of routes, or the selecting unit is configured to include And means for selecting a route that minimizes the transmission rate.
[0012]
When selecting a route with the maximum transmission rate from among the plurality of routes, a route with the lowest congestion occurrence probability can be selected. Further, when selecting a route having the required minimum transmission rate from the plurality of routes, a large amount of empty bandwidth can be left, so that a situation in which data transfer suddenly occurs frequently occurs. In this case, this can be flexibly dealt with.
[0013]
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, 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 the band secured by the securing means according to the above.
[0014]
As described above, the ATM switch secures a band in accordance with the transmission rate information written in the OAM cell added to the head of a series of cells from the server to the client, and further, the OAM cell at the end of the series of cells. By releasing the bandwidth secured in accordance with the transmission rate information written in, the required bandwidth can be secured only during the passage of a series of cells, so that the bandwidth can be effectively used.
[0015]
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 a transmission rate and a route determination algorithm in the server of the first 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 flowchart showing a transmission rate and a route determination algorithm in the server of the second embodiment of the present invention.
[0016]
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 10-8 for connecting the server 20 and the client 30. .
[0017]
Here, the feature of the present invention is that the client 30 attaches an OAM cell to the head of a series of cells going to the server 20 and writes rate information that can be transmitted and received by itself to the OAM cell, as shown in FIG. As described above, the ATM switches 10-1 to 10-8 each include a remaining bandwidth management unit 3 for managing the remaining bandwidth of the route through which the series of cells pass, and a buffer (not shown) in which the series of cells are temporarily stored. , 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. According to the information, 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 the information of the estimated band is referred to as the OAM cell. And an information writing unit 4 for writing the estimated bandwidth information written in the OAM cell for each of the OAM cells coming from a plurality of routes, as shown in FIG. 12 to transfer a series of cells to the client without causing congestion in accordance with the information of the estimated bandwidth and the size information of the data requested by the client 30 within a fixed time set by the timer processing unit 17. And a determination unit 13 for selecting one of the plurality of routes according to the set transmission rate, and adding an OAM cell to the beginning and end of a series of cells. The transmission rate information of the route selected by the determination unit 13 is added to the first and last OAM cells. Some at having a transmission unit 14 for writing.
[0018]
In the first embodiment of the present invention, the determination unit 13 selects a route having the maximum transmission rate from the plurality of routes. On the other hand, in the second embodiment of the present invention, the determination unit 13 selects a route having the required minimum transmission rate from the plurality of routes.
[0019]
As shown in FIG. 2, 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.
[0020]
Next, the operation of the embodiment of the present invention will be described. As described above with reference to FIG. 10, the characteristic of the client-server type traffic is that, in response to a request from the client to the server, the server returns a response to the client. 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.
[0021]
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.
[0022]
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.
[0023]
Next, when the OAM cell arrives at the ATM switches 10-1 to 10-8, the cell identification unit 1 shown in FIG. 2 determines that the cell is an OAM cell, and reads the included identifier CLIENT. Then, it is determined that the subsequent data is client-server type traffic and that it is a communication from the client 30 to the server 20. Then, the information writing section 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) to be processed is set to the remaining bandwidth management unit 3 that manages 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. It is estimated by referring to the value of the queue length monitoring unit 2 that monitors the queue length of the buffer (not shown) to be accumulated, and the bandwidth of the band in which cells can be transferred from the server 20 to the client 30 without causing congestion. Information is calculated, and the calculated value is compared with the value included in the bandwidth information of the OAM cell. If the calculated value is smaller, the value is changed to the bandwidth of the OAM cell. To write transfer to the broadcast.
[0024]
As shown in FIG. 4 , 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).
[0025]
The information writing unit 4 compares the calculated value with the value included in the band information of the OAM cell, and if the calculated value is smaller, writes the value into the band information of the OAM cell.
[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. Then, the band information written in the OAM cell is read by the information reading unit 12 and sent to the determination unit 13. In the determining unit 13, route information arriving from a plurality of routes for a certain period of time determined by the timer processing unit 17 is accumulated in the route information managing unit 16, and an optimum route is determined among the routes. At this time, the server 20 checks the size of the data requested by the client 30 by the transmission data size management unit 15, and sends a value C (cell / S) obtained by dividing the data size by a predetermined time T to the determination unit 13. The determination unit 13 determines a transmission rate for each of the plurality of routes by an algorithm as shown in FIG. 6, selects one of the plurality of routes according to the transmission rate, and starts transmission.
[0027]
FIG. 6 shows the transmission rate and the route determination algorithm in the server 20 according to the first embodiment of the present invention. The maximum value of the values written in the OAM cells in a plurality of routes is C (the requested data size (cell) / a certain time). If T (second)) or more (S6), the transmission rate is set to α × C (where 0 <α ≦ 1), and a route that maximizes α × C is selected (S7). If the value written in the OAM cell is less than C and equal to or more than the lower limit value LB (S8), the transmission rate is set to α × (the maximum 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).
[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 5 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 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.
[0030]
Next, a transmission rate and a route determination 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. 8, the values (B1, B2,..., Bn) written in the OAM cells through a plurality of routes are changed to C (requested data size (cell) / time T (Second)) or more (S11), the transmission rate is α × C (where 0 <α ≦ 1), and the value (Bi, i is any of 1 to n) written in the OAM cell is The route i having the smallest value exceeding C is selected (S12). If the value written in the OAM cell is less than C and equal to or greater than the lower limit LB (S13), the transmission rate is set to α × (the maximum value written in the OAM cell) (S14). If the value written in the OAM cell is less than C and less than the lower limit LB, no data is transmitted (S15).
[0031]
When the transmission rate and route determination algorithm of the first embodiment of the present invention shown in FIG. 6 is used, the route having the lowest transmission rate is selected by selecting the route having the highest transmission rate from a plurality of routes. Can be selected. When the transmission rate and route determination algorithm according to the second embodiment of the present invention shown in FIG. 8 is used, a route having the minimum required transmission rate is selected from a plurality of routes, so that a lot of empty bandwidth is left. This makes it possible to flexibly cope with a situation in which data transfer suddenly occurs frequently.
[0032]
【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 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 a transmission rate and a route determination algorithm in the server of the first 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 flowchart showing a transmission rate and a route determination algorithm in the server according to the second embodiment of the present invention.
FIG. 9 is a diagram showing a communication network of a client-server model.
FIG. 10 is a diagram showing client-server type traffic.
[Explanation of symbols]
1, 5, 11 Cell identification unit 2 Queue length monitoring unit 3 Remaining bandwidth management unit 4 Information writing unit 5 Cell identification unit 6 Bandwidth reservation unit 10, 10-1 to 10-8 ATM switch 12 Information reading unit 13 Judgment unit 14 Transmission Unit 15 transmission data size management unit 16 route information management unit 17 timer processing 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 a band in which cells can be transferred, and means for writing information of the estimated band to the OAM cell,
Means for reading the information of the estimated bandwidth written in the OAM cell for each of the OAM cells arriving from a plurality of routes; and information of the estimated bandwidth collected within a certain time and the client. Means for setting a transmission rate for transmitting a series of cells to a client without causing congestion according to the requested data size information for each of the plurality of routes, and the transmission rate set by the setting means Means for selecting any one of the plurality of routes according to the above, means for adding OAM cells to the head and tail of a series of cells, and the route selected by the means for selecting the head and tail OAM cells. Means for writing the transmission rate information. 2. The ATM communication network according to claim 1, wherein the selecting unit includes a unit that selects a route having the maximum transmission rate among the plurality of routes. 2. The ATM communication network according to claim 1, wherein said selecting means includes means for selecting a route that minimizes the transmission rate among the plurality of routes. 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 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 2. The ATM communication network according to claim 1, further comprising means for releasing a band secured by said securing means in accordance with the following.

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