JPH10210107A - Communication controlling method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a communication controlling method which maintains a communication speed that is needed by an application even when the delay time of a network becomes long. SOLUTION: A transmitter records a round trip time to a receiver, derives the next round trip time by using the recorded round trip time, decides a receiving buffer size based on the derived round trip time and notifies the receiver of the decided buffer size. In such cases, a sending time is recorded together with the round trip time at the time recording it, and the next round trip can be derived by using the round trip time and the sending time. Furthermore, while the receiver responds to the transmitter for sending back, an expandable buffer memory amount of the receiver is written at the point of time and sent back to the transmitter.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a communication control method for a multimedia communication system for transmitting and receiving high-quality information such as video or audio that needs to be received and reproduced in real time over a connectionless communication network such as the Internet.

In the case of a conventional multimedia communication system, when the network starts to be crowded, data is accumulated in a buffer such as a router or a bridge on the way, so that a delay occurs in data transmission. Conversely, when the network is free, the data delay time is reduced. As described above, the delay time of the network changes every moment.

[0003] In this case, conventionally, a large buffer is prepared in advance on the receiving side so that the data can be reproduced without interruption even when the network is congested. A method of applying flow control to stop is used.

When the rate control is performed using such conventional flow control, when the delay time of the network increases, the time required for the response to return to the transmission side becomes longer, and the next data transmission is performed. Is delayed. for that reason,
A situation occurs in which the communication speed required by the application cannot be obtained. In order to avoid such a situation, a buffer as large as possible has been prepared in the past, but considering transmission and reception of high-quality video such as HDTV, a buffer of several tens of megabytes is only used for communication. Must be prepared.

[0005]

SUMMARY OF THE INVENTION An object of the present invention is to provide a communication control method capable of maintaining a communication speed required by an application by using a minimum necessary buffer even when a network delay time increases. Is to provide.

[0006]

According to the communication control method of the present invention, in order to achieve the above object, a round trip time (a data transmission from a transmission device to a reception device and a response Recording the time until it returns from the receiving device), deriving the next round trip time using the recorded round trip time, and a receiving buffer based on the derived round trip time. The method further comprises a step of determining the size and a step of notifying the receiving apparatus of the determined buffer size.

According to the communication control method of the present invention, in order to prevent the buffer on the receiving side from overflowing, the receiving side always returns an acknowledgment to the transmitting side when receiving data for the buffer, and the transmitting side sets the round trip time. Record for the past several times for each communication destination or connection, predict the next delay time based on the record, and if the predicted delay time is long, and the communication speed requested by the application If it is not possible to secure the same communication speed, a buffer expansion request is transmitted to the receiving side, the reception buffer is expanded, and the number of reception acknowledgments is reduced to maintain the same communication speed.

In this case, in the present invention, when recording the round trip time, the transmission time is recorded together with the round trip time, and the next round trip time is derived using the round trip time and the transmission time. it can. In this way, the round trip time can be regarded as a function of the transmission time, and a functional relationship can be derived from the values of the last several times, and extrapolated to derive a more accurate next round trip time. it can.

Further, in the present invention, during the response returned by the receiving device to the transmitting device, the amount of buffer memory that can be expanded at the time of the receiving device can be written and returned to the transmitting device. The transmitting side can obtain information on the buffer amount of the receiving side at the time of starting transmission / reception, but if the information on subsequent changes is obtained as described here, the transmitting side can momentarily The change in the available buffer amount on the receiving side can be accurately known, and the buffer memory on the receiving side can be used efficiently especially when communicating with a plurality of terminals.

By using the communication control method of the present invention, communication can be performed without lowering the communication speed even when the network delay time changes. Further, by estimating from the past several round trip times, even when the delay time increases due to a temporary increase in traffic such as WWW, the network delay amount can be correctly estimated.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, embodiments of the present invention will be described with reference to the drawings. FIG. 1 shows an example of a general communication system. The transmission device 10 temporarily stores the data received from the application in the transmission buffer 11, packetizes the data, and transmits the packet to the reception device 20 via the network 30.
The receiving device 20 temporarily stores the data received from the transmitting device 10 in the receiving buffer 21, and when the data is full, passes the data to the receiving application and returns a response to the transmitting device 10. The transmission time (transmission time) and the round trip time are stored in the time data storage memory 12 of the transmission device 10.

FIG. 2 is a flowchart for explaining the outline of the processing of the transmitting apparatus and the receiving apparatus according to the present invention. The transmitting apparatus 10 first calculates a round trip time for data to be transmitted before transmitting the data. As a calculation method, for example, a difference T2−T1 of a previously observed round trip time from a previously observed round trip time T2 and a previously measured round trip time T1 can be calculated immediately before. In addition to the round-trip time T2, the next round-trip time is set to 2T2 -T1, the round-trip time is regarded as a function of the transmission time, and the round-trip time and transmission time observed several times immediately before are considered. , A method of obtaining a predicted value of the next round trip time by extrapolating the function to a linear function using, for example, the least squares method can be used.

[0013] Then, the round trip time thus obtained is compared with the previous one, and if the predicted round trip time becomes longer, a buffer size for obtaining the required communication speed is calculated. . As a result, when it is necessary to extend the buffer, the data packet to be transmitted next is loaded with the new buffer size and transmitted to the receiving device 20. If the calculated buffer size is larger than the buffer size written in the previous response,
The application is notified that the required speed is not achieved, and the application is encouraged to take measures such as increasing the video compression ratio. The time at that time is recorded in the time data storage memory 12 as the transmission time. Thereafter, data packets of the previously calculated buffer size are transmitted.

Conversely, if the buffer can be made smaller, the data packet to be transmitted is loaded with the new buffer size and transmitted to the receiving device 20, as in the case of expansion.
Upon receiving the data packet, the receiving device 20 changes the buffer size to the buffer size specified by the received data packet, and after receiving the data packet of the buffer size,
A response is returned to the transmitting device 10. When the transmission device 10 receives the response, it calculates and records a round trip time from the transmission time of the last transmitted data packet and the time at which the response was received. The above procedure is repeated until there is no more data to be transmitted.

[0015]

Conventionally, when a delay caused by a network during transmission of video or audio has been large, the communication speed has been interrupted due to a decrease in the communication speed. However, if the communication control method according to the present invention is used, the communication speed is reduced. This has a remarkable effect that continuous reproduction can be performed without dropping.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating an example of a general communication system.

FIG. 2 is a flowchart illustrating an outline of processing of a transmitting device and a receiving device according to the present invention.

[Explanation of symbols]

 REFERENCE SIGNS LIST 10 transmission device 11 transmission buffer 12 time data storage memory 20 reception device 21 reception buffer 30 network

Claims (3)

[Claims] 1. A recording apparatus for recording a round trip time, a step of deriving a next round trip time using the recorded round trip time, and a receiving buffer based on the derived round trip time. A communication control method comprising: determining a size; and notifying the receiving device of the determined buffer size. 2. A step of recording a transmission time together with a round trip time in a transmitting apparatus, a step of deriving a next round trip time using the round trip time and the transmission time, and a step of deriving a round trip time based on the derived round trip time. A communication control method, comprising: determining a receiving buffer size; and notifying the receiving device of the determined buffer size. 3. The communication control method according to claim 1, further comprising: writing a scalable buffer memory amount of the receiving device at the time during the response returned by the receiving device to the transmitting device; A communication control method comprising a step of returning.