JP2000269975A - Data transfer unit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To ensure transfer throughput at an application level, even when the yield of data transfer is limited due to retransmission of data. SOLUTION: An applications section 106 informs a throughput management section 105 about a communication opposite party terminal address, a request transfer throughput and a transfer control protocol in use. A reserved band quantity calculation section 110 of the throughput management section 105 transmits a communication opposite party terminal address to an RTT measurement section 108, receives its RTT, receives error rate (cell loss) from an error rate measurement section 107, and references a table of a throughput characteristic storage section 109 to calculate a normalized transfer throughput. The reserved band quantity calculation section 110 calculates throughput reduction rate on the basis of the RTT value, the cell loss rate and the normalized transfer throughput characteristic, and further calculates the reserved band quantity and informs the application section 106 of this.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a data transfer apparatus capable of reserving a transmission band of a communication network, and more particularly to a data transfer apparatus which transfers data at an application level even when the data transfer efficiency is reduced due to data retransmission. This is to guarantee the throughput.

[0002]

2. Description of the Related Art In a communication network that supports real-time communication such as voice transmission (telephone) and video simultaneously with other traffic, a transmission line band is reserved based on a report from a terminal device as a user. May provide communication services. For example, ATM (As
(ynchronous Transfer Mode)
The communication network is based on QoS (Quality of Service).
Service) Supports multiple traffic classes with different guarantee contents, one of which is CBR
In the (Constant Bit Rate) class,
A transmission path band on a transmission path can be reserved by a call connection prior to the start of data transfer. By using such a communication service, the application requiring the real-time property can secure a desired transmission rate, and it is guaranteed that the application will not be interrupted or change in the transmission rate during communication.

[0003] In a communication network that supports communication that does not require real-time properties simultaneously with other traffic, a user terminal device reports a used band and a used time, and schedules time allocation of the band based on the report. Communication network (Japanese Unexamined Patent Publication No.
No. 69921). In this network, scheduling the time allocation of the band delays the data transfer start time depending on the congestion of the communication network. In exchange for this, the used band and the used time are guaranteed after the start of data transfer. this is,
This is equivalent to guaranteeing the transfer data amount.

By the way, during a computer data transfer performed between applications on a plurality of computers via a communication network, transmission errors are not allowed.
Some of them require a certain degree of real-time performance. For example, in a network printing application that uses a page printer equipped with a drawing engine based on xerography technology, the data must be matched to the drawing processing speed of the engine in order to improve the operation efficiency of the printer and reduce the amount of buffers. It is desirable that the transfer be performed. In addition, since the data transferred at this time may be subjected to compression encoding or embedded drawing control information, there is a danger that drawing quality may be significantly reduced if transmission errors occur. Does not allow transmission errors.

[0005] In voice transmission and video transmission, real-time characteristics and responsiveness are important from the perceptual characteristics of a person who is the receiver, and transmission errors during communication are tolerated. Therefore, in such an application, error recovery is not performed, or error recovery is performed not by retransmission by a transfer control protocol but by performing error correction coding on data. Therefore, if there is no increase in the amount of transfer data due to retransmission, no overhead due to protocol processing or fluctuation thereof, and the transmission rate is guaranteed by the communication network, the application requirements are satisfied. This is shown in FIG.

[0006] On the other hand, in computer data transfer that does not allow errors, error detection coding (for example, CR
C, cyclic redundancy code) and retransmission by protocol processing recovers transmission errors. For example, the transfer control protocol T
CP (Transmission Control P)
protocol and SSCOP (Service Sp)
efficient Connection Oriente
d Protocol) provides such a service. However, in computer data transfer that performs transfer control protocol processing, the dynamic characteristics of the overhead due to the transfer control protocol and the increase in the amount of transfer data after the start of communication due to retransmission when a transmission error occurs cause a problem in the communication network. Even if the transmission rate (transmission band) is guaranteed, the transfer throughput between applications after protocol processing is reduced and fluctuates. This is shown in FIG.
(B).

[0007] Further, in a communication network that allocates a transmission band time, the end of data transfer must be completed within the allocated use time due to an increase in the amount of transfer data after the start of communication due to retransmission when a transmission error occurs. There is a danger in time.

[0008]

As described above, in the conventional computer data transfer, even if the transmission path bandwidth reservation provided by the communication network is used, the transfer between applications is caused by the error recovery control. There is a problem that throughput is not guaranteed. Therefore, an object of the present invention is to guarantee transfer throughput with high accuracy.

[0009]

The present invention will be described below.

[0010] By including a margin in the reserved amount of the transmission band declared to the communication network, the transfer throughput between applications can be made closer to a desired value. By reflecting the transmission error rate characteristic of the communication network and the throughput characteristic of the transfer control protocol in the margin, the transfer throughput can be guaranteed with high accuracy.

However, since the application has no way of knowing the transmission error rate characteristics of the communication network or the throughput characteristics of the transfer control protocol, it cannot determine the optimal amount of transmission bandwidth to be declared to the communication network.

According to the present invention, when a transfer throughput required by an application is given, a correction is performed in consideration of a throughput characteristic of a transfer control protocol process.
Determine the used bandwidth reservation amount.

The present invention will be further described. According to the present invention, in order to achieve the above object, a data transfer device for controlling data transfer between applications performed via a communication network includes means for determining a transmission error rate of the communication network; A means for determining a transfer throughput characteristic of a transfer control protocol used for data transfer, and a transfer control means for controlling data transfer between the applications based on the transmission error rate and the transfer throughput characteristic are provided.

[0014] The transfer control means may determine a transmission bandwidth used by the application based on, for example, a transfer throughput designated by the application, a transfer throughput of a transfer control protocol used for data transfer by the application, and the transmission error rate. Determined and notified to the application, and the application secures the notified transmission band and performs data transfer. In this way, the transfer throughput between the applications is secured with a high probability.

[0015] The transfer control means may further include a transfer bandwidth used by the application based on a transfer throughput specified by the application, a transfer throughput characteristic of a transfer control protocol used for data transfer by the application, and the transmission error rate. And secure a transmission band for the application. Also in this case, a band with a margin is secured according to the transfer throughput specified by the application, and the transfer throughput between the applications is secured with a high probability.

In this configuration, the means for determining the transmission error rate may continuously measure the transmission error rate in parallel with normal data transfer. Further, the means for determining the transmission error rate may hold a transmission error rate value set in advance according to the transmission medium. Also,
The means for determining the transmission error rate may be provided in the network or may be provided in the receiving host computer.

The means for obtaining the transfer throughput characteristic may hold the theoretical characteristic of the transfer throughput with respect to the transmission error rate for each transfer control protocol as a table in advance, or may be provided for each combination of each host computer. The transfer throughput characteristics may be tested, and the test results may be held in advance as a table.

[0018]

Embodiments of the present invention will be described below. [First Embodiment] FIG. 1 shows the entire network environment of a first embodiment of the present invention. In this embodiment, a band is determined on the terminal (application) side using an ATM switch.

In FIG. 1, terminal devices 10 and 11 are AT
It is connected to the M switch 12. Terminal devices 10, 11
Communicates after performing a call connection according to the procedure shown in FIG. 2, and releases the call after the communication is completed. That is, a setup request is issued from the calling terminal device 10 and the ATM switch 1
2 and a call connection between the transmitting terminal device 10 and the receiving terminal device 11 (SETUP, CALL PROC, CON
N, CONN ACK). After the communication, the calling terminal device 10
Sends a release request to the ATM switch 12, the call between the calling terminal device 10 and the ATM switch 12 is released, and
The M switch 12 sends a release request to the receiving terminal device 11,
The call between the ATM switch 12 and the terminating terminal device 11 is released (REL, REL COMP). FIG. 3 shows a configuration example of the terminal devices 10 and 11 in detail. In this figure, the terminal device 10 includes a cell receiving unit 101, a cell transmitting unit 102, a transfer control protocol unit 103, a signaling protocol unit 104, a throughput The configuration includes a management unit 105 and an application unit 106.

The cell receiving section 101 receives an ATM cell,
The cell transmission unit 102 transmits an ATM cell.
The transfer control protocol 103 performs retransmission control, order control, and the like. The signaling protocol unit 104 controls call connection and the like. Throughput management unit 10
Reference numeral 5 is for determining a network transmission band so that the data transfer throughput between applications becomes a desired one, and notifying the application unit 106.
The application unit 106 sends this transmission band to the ATM switch 12 and reserves the band.

FIG. 4 shows an example of the configuration of the throughput management unit 105. In this figure, the throughput management unit 105 includes an error rate measurement unit 107, an RTT (Run)
It includes a (trip time) measuring unit 108, a throughput characteristic holding unit 109, a reserved bandwidth amount calculating unit 110, and the like. The error rate measuring unit 107 calculates cells that cannot be recovered by error correction (lost cells, must be retransmitted).
Is to measure the occurrence rate. RTT measuring unit 108
Is the time that traffic travels back and forth through the network,
That is, the time RTT from when a retransmission request is made to when a retransmission cell arrives is measured. Since the RTT differs depending on the location of the communication partner terminal device in the network, the address of the terminal is supplied to the RTT measuring unit 108. The throughput characteristic holding unit 109 uses the RTT
And characteristic data indicating how the throughput of data transfer between applications changes according to the cell loss rate. This characteristic data is, for example, as shown in FIG. 5, and shows how the throughput changes according to the cell loss using the RTT and the protocol type as parameters. The throughput characteristic storage unit 109 is stored as a table as shown in FIG. 6, for example.

Note that the RTT measuring unit 108 is, for example, as shown in FIG.
The table as shown in the table below is stored, and the RTT is
And the measured (actually measured) value. After the call connection, the initial value is used, and thereafter, the measured value is used.

Next, the operation of this embodiment will be described. FIG. 8 shows the operation of the embodiment. In this figure, first, the application unit 106 notifies the throughput management unit 105 of the address of the communication partner terminal device, the requested transfer throughput value, and the transfer control protocol to be used (S1). ).

Next, the throughput management unit 105 outputs the normalized transfer throughput characteristics (S2). That is, reserved bandwidth amount calculation section 110 of throughput management section 105 sends the communication partner terminal address to RTT measurement section 108 and receives the RTT. Further, the reserved bandwidth amount calculation unit 110 receives the error rate (cell loss) from the error rate measurement unit 107. Then, the reserved bandwidth amount calculation unit 110
The normalized transfer throughput is calculated by referring to the table of the throughput characteristic holding unit 109 based on the RTT value and the error rate.

After that, the reserved bandwidth amount calculation unit 110
The throughput reduction rate is calculated based on the T value, the cell loss rate, and the normalized transfer throughput characteristic (S3).

Thereafter, the reserved bandwidth amount calculation unit 109 calculates the reserved bandwidth amount based on the following equation (S4).

[0027]

## EQU1 ## The reserved bandwidth amount = requested transfer throughput value / throughput decrease rate The reserved bandwidth amount calculated as described above is notified to the application unit 106, and the application unit 106
Reserved in the TM switch 12.

Embodiment 2 Next, Embodiment 2 of the present invention will be described. In this embodiment, the bandwidth is set adaptively in the network so that the data transfer throughput between the applications becomes desired. In this example, the band itself is also reserved.

FIG. 9 shows the network environment of this embodiment. In this figure, the terminal devices 10 and 11
It is connected to the communication node device 13. In this network, as shown in FIG.
Makes a reservation to the communication node device 13. The communication node device 13 manages reservation of communication with the receiving terminal device 12 and requests a reservation (RES) from the transmitting terminal device 10.
V), it responds (RESV ACK), and if reservation is possible, the transmitting terminal device 10 and the receiving terminal device 1
Assigned to 1 (ALLOC). The assignment designation is, for example, a start time, a band, and the like. The terminal devices 11 and 12 return a response (ALLOC ACK).

Thereafter, when the reservation time arrives, a call connection is made (SETUP, CONN, CONN ACK),
After the communication ends, the call is released (REL, REL COM)
P).

FIG. 11 shows an example of the configuration of the communication node device 13. In this figure, the communication node device 13
It is configured to include a line interface 131, a switching unit 132, a trunk line interface 133, and a connection control unit 134. Line interface 131, switching unit 13
2. The trunk interface 133 is a normal one.

FIG. 12 shows an example of the configuration of the connection control unit 134. In this figure, the connection control unit 134 includes a cell reception unit 135, a cell transmission unit 136, a band management unit 137, a processor 138, and a route information management table. 139 and the like.

FIG. 13 shows an example of the configuration of the bandwidth management section 137. In this figure, the bandwidth management section 137 includes a reservation application receiving circuit 141, an error rate measurement section 142, a bandwidth allocation amount calculation section 143, a throughput characteristic. Holder 144, RTT
It is configured to include a holding table 145, a reservation management table 146, a scheduler 147, a bandwidth management table 148, and the like.

The reservation request receiving circuit 141 receives a reservation request from the transmitting terminal device 10. The error rate measuring unit 142 measures a cell loss rate. RT
The T holding table 145 holds the RTT value for each communication terminal device address. The throughput characteristic holding unit 144 holds data of characteristics indicating how the throughput changes according to the RTT value and the cell loss rate. The bandwidth allocation calculator 143 calculates the cell loss rate,
Based on the RTT value, the bandwidth is calculated by referring to the throughput characteristic holding unit 144, and the scheduler 147 is reserved. The scheduler 147 performs scheduling with reference to the bandwidth management table 148, registers the result of the scheduling in the reservation management table 146, and rejects the reservation. The control cell generation circuit 149 transmits control information to the transmitting terminal device 10 and the receiving terminal device 11 by cells.

FIG. 14 shows an example of the RTT holding table 145.

FIG. 15 shows the operation of this embodiment. In this figure, first, the bandwidth allocation amount calculation unit 143
Receives, from the scheduler 147, the address (pair) of the terminal device that performs communication, the reserved transmission bandwidth value, and the type of transfer control protocol to be used (S11).

Next, the operation of this embodiment will be described. FIG. 8 shows the operation of the embodiment. In this figure, first, the application unit 106 notifies the throughput management unit 105 of the address of the communication partner terminal device, the requested transfer throughput value, and the transfer control protocol to be used (S11). ).

Next, the bandwidth allocation calculator 143 outputs the normalized transfer throughput characteristics (S12). That is, the bandwidth allocation calculator 143 sends the address of the communication partner terminal to the RTT holding table 145 and receives the RTT. Further, the reserved bandwidth amount calculation unit 108 receives the error rate (cell loss) from the error rate measurement unit 142. Then, the bandwidth allocation amount calculation unit 143 refers to the table of the throughput characteristic storage unit 144 based on the RTT value and the error rate, and calculates the normalized transfer throughput.

After that, the bandwidth allocation amount calculation unit 143
The throughput reduction rate is calculated based on the T value, the cell loss rate, and the normalized transfer throughput characteristics (S13).

Thereafter, the bandwidth allocation calculator 143 calculates the reserved bandwidth based on the following equation (S14).

[0041]

## EQU00002 ## Band allocation amount = reserved transmission bandwidth value / throughput reduction rate Thereafter, the band allocation amount calculation unit 143 sends the band allocation amount to the scheduler 147, and the scheduler 147 performs scheduling. Thereafter, data transmission is performed according to the schedule.

[0042]

As described above, according to the present invention, transfer throughput can be guaranteed with high accuracy for computer data transfer and the like that does not allow transmission errors. As a result, an application that requires both reliability and real-time processing can be realized on a computer with a relatively small amount of buffer.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating a network environment according to a first embodiment of this invention.

FIG. 2 is a diagram illustrating the operation of the network environment of FIG. 1;

FIG. 3 is a block diagram illustrating a configuration of a terminal device of FIG. 1;

FIG. 4 is a block diagram illustrating a configuration example of a throughput management unit in FIG. 3;

FIG. 5 is a diagram illustrating a throughput characteristic holding unit shown in FIG. 4;

FIG. 6 is a diagram illustrating a table of a throughput characteristic holding unit shown in FIG. 4;

FIG. 7 is a diagram illustrating an error rate measurement unit 106 of FIG.

FIG. 8 is a flowchart illustrating an operation of a main part of the first embodiment.

FIG. 9 is a diagram illustrating a network environment according to a second embodiment of this invention.

FIG. 10 is a diagram illustrating the operation of the network environment in FIG. 9;

FIG. 11 is a block diagram illustrating a configuration of a communication node device in FIG. 9;

FIG. 12 is a block diagram illustrating a configuration example of a connection control unit in FIG. 11;

13 is a block diagram illustrating a configuration example of a band management unit in FIG.

FIG. 14 is a diagram illustrating the RTT holding table of FIG. 12;

FIG. 15 is a flowchart illustrating an operation of a main part of the second embodiment.

FIG. 16 is a diagram illustrating a conventional problem.

[Explanation of symbols]

 Reference Signs List 10 originating terminal device 11 terminating terminal device 12 ATM switch 13 communication node device 101 cell receiving unit 102 cell transmitting unit 103 transfer control protocol unit 104 signaling protocol unit 105 throughput managing unit 106 application unit 107 error rate measuring unit 108 RTT measuring unit 109 throughput Characteristics holding unit 110 Reserved bandwidth amount calculation unit 131 Line interface 132 Switching unit 133 Trunk line interface 134 Connection control unit 135 Cell reception unit 136 Cell transmission unit 137 Band management unit 138 Processor 139 Route information management table 141 Reservation application receiving circuit 142 Error rate Measuring unit 143 Bandwidth distribution amount calculating unit 144 Throughput characteristic holding unit 145 RTT holding table 146 Reservation management table 147 Scheduler 148 Bandwidth tube Table 149 control cell generation circuit

Claims (9)

[Claims] 1. A data transfer apparatus for controlling data transfer between applications performed via a communication network, comprising: means for determining a transmission error rate of the communication network; and transfer throughput of a transfer control protocol used by the application for data transfer. A data transfer apparatus, comprising: means for obtaining characteristics; and means for controlling data transfer between the applications based on the transmission error rate and the transfer throughput characteristics. And means for controlling data transfer between the applications based on a transfer throughput specified by the application, a transfer throughput of a transfer control protocol used for data transfer by the application, and the transmission error rate. Determine the transmission band used by the application, notify the application,
2. The data transfer device according to claim 1, wherein the application secures the notified transmission band and performs data transfer. And means for controlling data transfer between the applications based on a transfer throughput specified by the application, a transfer throughput of a transfer control protocol used by the application for data transfer, and the transmission error rate. The data transfer device according to claim 1, wherein a transmission band used by the application is determined, and a transmission band is reserved for the application. 4. The data transfer apparatus according to claim 1, wherein said means for calculating the transmission error rate continuously measures the transmission error rate in parallel with normal data transfer. 5. The data transfer device according to claim 1, wherein said means for calculating the transmission error rate holds a transmission error rate value set in advance according to a transmission medium. 6. The data transfer device according to claim 1, wherein the means for determining the transmission error rate is provided in a network. 7. The method according to claim 1, wherein the means for determining the transmission error rate is provided in a receiving host computer.
6. The data transfer device according to 4 or 5. 8. The method according to claim 1, wherein said means for calculating the transfer throughput characteristic holds in advance a theoretical characteristic of the transfer throughput with respect to the transmission error rate for each transfer control protocol as a table. A data transfer device according to claim 1. 9. The method according to claim 1, wherein the means for determining the transfer throughput characteristics tests the transfer throughput characteristics for each combination of the host computers and holds the test results in advance as a table. , 6 or 7.