JPH07303117A - Congestion prevention method and packet communication system - Google Patents

Abstract

(57) [Abstract] [Purpose] To provide a congestion prevention method and a packet communication system that prevent congestion quickly and appropriately and protect real-time communication. [Composition] The packet transmission time interval of the transmission terminal 101 is transmitted to the reception terminal 102, and the difference between the sum of the reception time intervals and the sum of the transmission time intervals of continuously received packets set by the reception terminal 102 is detected. Then, the difference is compared with a threshold value, and according to the comparison, the transmission terminal 101 is notified, and the transmission terminal 101 receives either of the packet transmission time interval and the packet length, or both, or the transmission window size. The transmission bit rate is controlled by changing.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a congestion prevention method and a packet communication system for preventing congestion in terminals and communication systems connected to a packet network.

[0002]

2. Description of the Related Art In a packet network, when congestion occurs in the network, packet transmission delay increases and packet discard occurs. If the transmission delay increases, it becomes impossible to perform communication with a small allowable delay such as real-time video communication and voice communication. Further, if the packet is discarded, the data is retransmitted, the throughput is extremely lowered, and the decoded video and the decoded audio at the receiving terminal are greatly deteriorated.

Therefore, there has been conventionally considered a method of preventing congestion from occurring by making a reservation of a communication band from a terminal to a network prior to communication. In this method, a relay node or network server receives a request for a communication band from a terminal, and if the communication band can be secured, the communication is permitted, and if not, the communication is rejected.

[0004]

In the above-mentioned conventional method, it is necessary for the terminal to protect the assigned communication band in order to prevent the occurrence of congestion, and the terminal cannot be used even when the communication band of the network has a margin. There is one problem.

Further, if there are many opportunities to reserve the communication band up to the upper limit, there is a second problem that new communication is rejected more often.

Further, in the IP (version.4) network, which is a very widely used packet network, such a communication band is not allocated. Therefore, the communication protocol for allocating the communication band is relayed with the terminal. Must be implemented on both nodes.

On the other hand, when the communication band is not reserved for the network, it is necessary to prevent congestion after the start of communication. Therefore, there is a method of detecting congestion and controlling the communication bit rate of the transmitting terminal. Congestion can be detected by a relay node or a terminal. In the relay node, when the number of stored packets exceeds a threshold value or when packets are discarded due to buffer overflow, congestion is detected and notified to the terminal (ECN: Explicit Congestion Notification). The detected congestion is transmitted to the receiving terminal by setting a flag in the packet header, and the receiving terminal further conveys the congestion by sending a control packet to the transmitting terminal (FENC: Forward ECN).
Alternatively, the relay node that has detected the congestion sends a control packet that conveys the congestion to the transmitting terminal (Backword ECN). This method has a third problem that it cannot be used unless the relay node has the ECN function.

Further, when congestion occurs due to the limit of the processing capacity of the relay node, the processing load of the relay node is increased by the ECN processing, and the congestion is further deteriorated.
I have a problem.

As a method of detecting congestion at the terminal, there are a method of detecting a discarded packet at the receiving terminal, and a method of generating a round trip packet and detecting a case where the round trip time exceeds a threshold value. When congestion occurs, packet discard occurs after the increase in transmission delay, so there is a fifth problem in that the packet discard detection cannot detect congestion early.

In the packet round-trip time measurement, if the communication path is independent for each direction, the round-trip time increases even if congestion occurs in one direction. Therefore, the direction in which congestion does not occur is also detected as congestion. There is a sixth problem of being lost.

Further, in the case of multicast communication, since there are a plurality of receiving terminals, the packet round trip time with all the receiving terminals is measured to detect congestion. There is a seventh problem that the load increases.

Further, there is an eighth problem that the traffic increases due to the generation of periodic round trip packets for measurement.

In the transmission bit rate control of the transmission terminal by congestion detection, in real-time communication of coded video and audio,
When the transmission bit rate control is performed, the coded signal cannot be transmitted, so that there is a ninth problem that the real time property cannot be maintained.

The present invention has been made in view of the above,
It is an object of the present invention to provide a congestion prevention method and a packet communication system that prevent congestion quickly and appropriately and protect real-time communication.

[0015]

In order to achieve the above object, the congestion prevention method of the present invention is such that, in a terminal connected to a packet network, the packet transmission time interval of the transmitting terminal is transmitted to the receiving terminal and set by the receiving terminal. The difference between the sum of the reception time intervals and the sum of the transmission time intervals of the consecutively received packets of the specified number is detected, and the difference is compared with the set threshold value, and the receiving terminal according to the comparison result. Notifies the sending terminal,
The gist is that the transmitting terminal controls the transmission bit rate by changing either or both of the packet transmission time interval and the packet length or the transmission window size by receiving the notification.

Further, the congestion prevention method of the present invention is such that when a terminal connected to a packet network transmits coded video or coded audio, the packet transmission time interval of the transmitting terminal is transmitted to the receiving terminal so that the receiving terminal can Detects the difference between the sum of the reception time intervals and the sum of the transmission time intervals of the set number of consecutively received packets, compares the difference with the set threshold value, and receives according to the comparison result. The terminal notifies the sending terminal,
Upon receiving the notification, the transmitting terminal changes the video or audio coding rate, changes one or both of the packet transmission time interval and the packet length according to the change, and controls the transmission bit rate. Use as a summary.

Further, in the congestion prevention method of the present invention, as a step of transmitting the packet transmission time interval of the transmitting terminal to the receiving terminal, the packet transmitting time of the transmitting terminal is notified, and the difference between the transmitting times of the packets received by the receiving terminal is notified. The gist is to calculate the transmission time interval by calculating.

According to the congestion prevention method of the present invention, when a terminal connected to a packet network transmits coded video or coded audio, the coding speed of the transmitting terminal is transmitted to the receiving terminal, and the receiving terminal stores it in the receiving buffer. The set number of packets is accumulated and decoding is started, the receiving terminal detects the number of packets in the receiving buffer, compares the number of packets with the set threshold value, and the receiving terminal transmits according to the comparison result. The sending terminal notifies the terminal, and the sending terminal changes the coding rate of video or audio by receiving the notification, changes one or both of the packet transmission time interval and the packet length according to the change, and sends the transmission bit. The point is to control the rate.

Further, according to the congestion prevention method of the present invention, when a packet discard is detected at the receiving terminal, a dummy packet is inserted into the buffer when the packet discard is detected, and the accumulated number in the buffer is detected, the dummy packet is not counted. That is the summary.

Further, according to the congestion prevention method of the present invention, when a terminal connected to a packet network transmits coded video or coded audio, the coding speed of the transmitting terminal is transmitted to the receiving terminal, and the receiving terminal uses a buffer. Starts decoding by accumulating the encoded signal of the amount set to, the receiving terminal detects the amount of the encoded signal of the buffer, and compares the amount of the encoded signal with the set threshold value, The receiving terminal notifies the transmitting terminal according to the comparison result, and the transmitting terminal changes the coding rate of video or audio by receiving the notification, and according to the change, one of the packet transmission time interval and the packet length, or The point is to change both and control the transmission bit rate.

According to the congestion prevention method of the present invention, when a packet discard is detected at the receiving terminal, a dummy coded signal is inserted into the buffer when the packet is discarded, and the accumulated amount in the buffer is detected, the dummy coded signal The point is not to count the amount.

Further, the packet communication system of the present invention is
In a communication system connected to the packet network, means for notifying the receiving terminal of the packet transmission time interval of the transmitting terminal,
The difference between the sum of the reception time intervals and the sum of the transmission time intervals of continuously received packets set by the receiving terminal is detected, and the difference is compared with the set threshold value. And a means for controlling the transmission bit rate by changing either or both of the packet transmission time interval and the packet length, or the transmission window size upon receipt of the notification. Having it is the gist.

Further, the packet communication system of the present invention is
When transmitting coded video or coded audio in a communication system connected to a packet network, a means for notifying the receiving terminal of the packet transmission time interval of the transmitting terminal and a continuous reception of the number set by the receiving terminal A means for detecting a difference between the sum of the reception time intervals and the sum of the transmission time intervals of the packets, comparing the difference with a set threshold value, and the receiving terminal notifying the transmitting terminal according to the comparison result; The transmitting terminal changes the video or audio coding rate by receiving the notification, changes either or both of the packet transmission time interval and the packet length according to the change, and controls the transmission bit rate. It is a gist to have.

In the packet communication system of the present invention, as means for notifying the receiving terminal of the packet transmitting time interval of the transmitting terminal, the difference between the means for notifying the packet transmitting time of the transmitting terminal and the transmitting time of the packet received by the receiving terminal. And a means for determining a transmission time interval by calculating

Also, the packet communication system of the present invention is
When transmitting coded video or coded audio in a communication system connected to a packet network, the means for transmitting the coding speed of the transmitting terminal to the receiving terminal and the receiving terminal accumulating the number of packets set in the receiving buffer And means for starting decoding, the receiving terminal detecting the number of packets in the receiving buffer, comparing the number of packets with a set threshold value, and notifying the transmitting terminal according to the comparison result, and the transmitting terminal Means for changing the video or audio coding rate upon receipt of the notification, and changing either or both of the packet transmission time interval and the packet length according to the change to control the transmission bit rate. Having it is the gist.

Further, the packet communication system of the present invention comprises:
It is characterized in that it has means for detecting packet discard at the receiving terminal, inserting dummy packets in the buffer when packet discard is detected, and means for controlling so as not to count the dummy packets when detecting the accumulated number in the buffer. To do.

In the packet communication system of the present invention, in the communication system connected to the packet network, when transmitting encoded video or encoded audio, the means for transmitting the encoding speed of the transmitting terminal to the receiving terminal and the receiving terminal Means for accumulating a coded signal of a set amount in the buffer and starting decoding,
The receiving terminal detects the amount of encoded signals in the buffer, compares the amount of encoded signals with a set threshold value, and the receiving terminal notifies the transmitting terminal according to the comparison result; And a means for controlling the transmission bit rate by changing the video or audio coding rate by receiving the notification and changing either or both of the packet transmission time interval and the packet length according to the change. Is the gist.

Further, the packet communication system of the present invention is
When the receiving terminal detects packet discard and means for inserting the dummy coded signal into the buffer when the packet is discarded, and when detecting the amount of accumulation in the buffer, control is performed so that the amount of the dummy coded signal is not counted. The gist is to have means.

[0029]

According to the congestion prevention method of the present invention, the packet transmission time interval of the transmission terminal is transmitted to the reception terminal, and the sum of the reception time intervals of the continuously received packets of the number set by the reception terminal and the transmission time interval The difference from the sum is detected, compared with a threshold, and the transmission terminal is notified.

Further, in the congestion prevention method of the present invention, when transmitting coded video or coded voice, the packet transmission time interval of the transmitting terminal is transmitted to the receiving terminal, and the number of packets set by the receiving terminal is continuously set. The difference between the sum of the reception time intervals of the received packets and the sum of the transmission time intervals is detected, compared with a threshold value, and the transmission terminal is notified, and the transmission terminal receives the notification to encode video or audio. Change speed.

Further, in the congestion prevention method of the present invention, in the above, the transmission time interval is obtained by notifying the packet transmission time of the transmitting terminal and calculating the difference in the transmission time of the packets received by the receiving terminal. .

In the congestion prevention method of the present invention, when transmitting coded video or coded voice, the coding speed of the transmitting terminal is transmitted to the receiving terminal, and the receiving terminal accumulates the number of packets set in the receiving buffer. Then, the receiving terminal detects the number of packets in the receiving buffer, compares it with a threshold value, notifies the transmitting terminal, and the transmitting terminal changes the video or audio coding rate by receiving the notification. Let

Further, in the congestion prevention method of the present invention, when the packet discard is detected at the receiving terminal, the dummy packet is inserted into the buffer when the packet discard is detected, and the accumulated number in the buffer is detected, the dummy packet is not counted. .

Further, according to the congestion prevention method of the present invention, when transmitting coded video or coded voice, the coding speed of the transmitting terminal is transmitted to the receiving terminal, and the receiving terminal receives the encoded signal of the amount set in the buffer. , And starts decoding, the receiving terminal detects the amount of coded signal in the buffer, compares it with a threshold value, notifies the transmitting terminal, and the transmitting terminal receives video or audio by receiving the notification. Change the coding rate.

In the congestion prevention method of the present invention, when a packet discard is detected at the receiving terminal, a dummy coded signal is inserted into the buffer when the packet is discarded, and the amount of accumulation in the buffer is detected, the dummy coded signal Do not count the amount.

Further, in the packet communication system of the present invention, the packet transmission time interval of the transmission terminal is transmitted to the reception terminal, and the sum of the reception time intervals of continuously received packets and the transmission time of the number set by the reception terminal. The difference from the sum of the intervals is detected, compared with a threshold value, and the transmission terminal is notified.

Further, in the packet communication system of the present invention, when transmitting coded video or coded voice, the packet transmission time interval of the transmitting terminal is transmitted to the receiving terminal, and the number of packets set by the receiving terminal is continuously set. The difference between the sum of the reception time intervals of the received packets and the sum of the transmission time intervals is detected, compared with a threshold value, and the transmission terminal is notified, and the transmission terminal receives the notification to encode video or audio. Change speed.

In the packet communication system of the present invention, the transmission time interval is obtained by notifying the packet transmission time of the transmitting terminal and calculating the difference between the transmission times of the packets received by the receiving terminal.

Further, in the packet communication system of the present invention, when transmitting coded video or coded audio, the coding speed of the transmitting terminal is transmitted to the receiving terminal, and the receiving terminal transmits the number of packets set in the receiving buffer. After accumulating and starting decoding, the receiving terminal detects the number of packets in the receiving buffer,
The threshold value is compared, and the transmission terminal is notified, and the transmission terminal changes the video or audio coding rate by receiving the notification.

Further, in the packet communication system of the present invention, when the packet discard is detected by the receiving terminal, the dummy packet is inserted into the buffer when the packet discard is detected, and the accumulated number in the buffer is detected, the dummy packet is not counted. .

In the packet communication system of the present invention, when transmitting encoded video or encoded audio, the encoding speed of the transmitting terminal is transmitted to the receiving terminal, and the receiving terminal accumulates the encoded signal of the amount set in the buffer. Then, the receiving terminal detects the amount of coded signal in the buffer, compares it with a threshold value, notifies the transmitting terminal, and the transmitting terminal receives the notification to encode video or audio. Change speed.

Further, in the packet communication system of the present invention, when the packet discard is detected at the receiving terminal, the dummy coded signal is inserted into the buffer when the packet is discarded, and the accumulated amount in the buffer is detected, the dummy coding is performed. Do not count the amount of signal.

[0043]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram showing the configuration of the first embodiment of the present invention. In FIG. 1, 101 is a transmission terminal, 110 is a transmission line interface control unit, 120 is a connector, 123 is a transmission line, 300 is a packet transmission unit, 40
Reference numeral 0 is a congestion notification receiving unit, 102 is a receiving terminal, 130 is a transmission line interface control unit, 121 is a connector, 500 is a packet receiving unit, and 700 is a congestion notification transmitting unit. In addition,
The transmission path 123 may include a relay node.

In this embodiment, the packet transmission time interval of the communication terminal is transmitted to the receiving terminal in the packet network,
Detects the difference between the sum of the reception time intervals of the number of continuously received packets set on the receiving side and the sum of the packet transmission time intervals, and if this difference is larger than a predetermined threshold, congestion It is intended to notify the transmitting terminal that it has occurred, and thereby control the transmission bit rate in the transmitting terminal to prevent congestion. The packet transmission time interval and the reception time interval described above are set as shown in FIG. 13, and the sum of the reception time intervals (ΣT _r ) in this case is set.
And the sum of the transmission time intervals (ΣT _p ) is equal to the increase in the amount of transmission delay. Further, when congestion occurs, the amount of increase in transmission delay increases. Note that FIG. 13 shows the case of three packets for simplification of description, but the same applies to the case of N packets.

Next, the operation of the embodiment shown in FIG. 1 will be described with reference to the flow chart shown in FIG.

The connectors 120/121 of the transmitting terminal 101 and the receiving terminal 102 supply the signals on the transmission path 123 to the transmission path interface control section 110/130, respectively. The transmission path interface control unit 110/130 performs a process of fetching a packet whose destination address matches its own address. In addition, the transmission line interface control unit 110
/ 130 is a packet transmission unit 300 / congestion notification transmission unit 70
The own address is added to the packet transferred from 0, the packet is sent to the connector 120/121, and is supplied onto the transmission path 123.

The packet transmission unit 300 of the transmission terminal 101 generates a packet, and the transmission path interface control unit 110
Transfer to. Further, the generation time interval is set to the transmission time interval T _p.
As the address of the transmission line interface control unit 130, the packet information is added to the packet information, transferred to the transmission line interface control unit 110, and transmitted from the transmission line interface control unit 110 to the transmission line 123 via the connector 120. It is transmitted (step 1100).

The packet transmitted from the transmission terminal 101 to the transmission path 123 is taken in by the transmission path interface control section 130 of the reception terminal 102 and transferred to the packet reception section 500 (step 1110). Packet receiver 50
At 0, from the packet reception time interval T _r transmitted by the transmission terminal 101 and the packet transmission time interval T _p notified by the transmission terminal 101, N consecutive packets (N is 2
The total sum (ΣT _r −ΣT _p ) of the above natural numbers is calculated (step 1120). It is checked whether the sum is larger than a preset threshold T _th (step 11
30) If the sum exceeds a preset threshold value T _th, it is determined that congestion has occurred, and a signal is transmitted to the congestion notification transmission unit 700 (step 1140). Upon receiving the signal, the congestion transmission unit 700 generates a congestion notification packet for notifying congestion (step 1150). The generated congestion notification packet is added with the address of the transmission line interface control unit 110 as a destination address, transferred to the transmission line interface control unit 130, and transmitted to the transmission line 123 via the connector 121 (step 1160).

The transmission path interface control unit 110 of the transmitting terminal 101 receives the congestion notification packet transmitted by the receiving terminal 102 via the connector 120, and the congestion notification receiving unit 40
0 (step 1170). Congestion notification receiving unit 4
In 00, when the congestion notification packet is received, the signal is transferred to the packet transmission unit 300. Upon receiving the signal, the packet transmitter 300 controls the transmission bit rate (step 1180).

Next, a method of notifying the transmission time interval described above will be described.

Information on the transmission time interval is added to the transmission packet, but a change flag indicating a change in the transmission time interval may be further added to reduce the processing of the receiving terminal.
If there is no change by this, the receiving terminal only needs to confirm the flag.

As another method of notifying the transmission time interval, the packet generator 3 is changed every time the transmission time interval is changed.
The notification may be made by generating a control packet containing information on the transmission time interval at 00. In this case, for example, if the transmission time interval is not changed during communication, it is sufficient to transmit the control packet at the start of communication.

Further, as a method of notifying the transmission time interval, information on the transmission time may be added. In this case, the transmission time interval is obtained by calculating the time difference at the receiving terminal. In particular, this method is suitable when the transmission time interval is not preset. Further, the transmission time may be given for every N packets.

Next, a method of calculating the above-mentioned total sum (ΣT _r −ΣT _p ) will be described. This calculation method includes a method of calculating each time a packet is received, a method of calculating every N packets received, and a method of using a timer timeout.

First, a method of calculating each packet reception will be described.

In this method, each time a packet is received,
The packet receiving unit 500 uses an internal clock to check and store the reception time. Sum of packet reception time intervals T _r ΣT
_r is obtained by calculating the difference between the latest packet reception time and the packet reception time N-1 or earlier.

On the other hand, the sum ΣT of the packet transmission time intervals T _{p
In the} case of obtaining _p , if the information of the transmission time interval is added to the packet, the sum of the latest N notified T _p is calculated. At this time, if there is no change in the transmission time interval,
It is only necessary to multiply the notified transmission time interval by N. Also,
When the transmission time is notified, the difference between the transmission time of the latest received packet and the transmission time of N-1 or earlier received packets is obtained. In the case of this method, it is necessary to store the reception time and the transmission time interval or the transmission time of the latest N received packets.

Next, a method of calculating each time N packets are received will be described.

ΣT for every N consecutively received packets
It is also possible to calculate _r −ΣT _p . When N pieces are received,
ΣT _r −ΣT _p is calculated and it is checked whether the threshold value T _th is exceeded. In this case, the arrival time need only store the time when N pieces were received and the time N-1 pieces before. This method is used when the packet transmission unit 300 adds the transmission time to every N packets.

Next, a method of utilizing the timeout of the timer will be described.

If the transmission time interval is not changed during communication, a timer of (N × T _p + T _th ) is started every N times received, and congestion occurs when the timer times out before N times are received. May be detected. In this case, when N packets have timed out before reception, congestion is detected at that point and a new timer is started. With this method, it is not necessary to check the time.

When packet discard occurs,
Since the discarded packets are not received, an error may occur in the calculation of the total sum, but it is possible to ignore the packet discard and calculate only the arrived packets. Alternatively, a sequence number may be given to the transmitted packet, packet discard may be detected on the receiving side, and the reception time interval of the discarded packet may be calculated as equal to the transmission time interval.

Next, the comparison between the above-mentioned total sum (ΣT _r −ΣT _p ) and the threshold value T _th will be described.

The sum (ΣT _r −ΣT _p ) and the threshold value T
The comparison with _th is performed every time (ΣT _r −ΣT _p ) is calculated. Then, the threshold value T with the latest (ΣT _r −ΣT _p ).
As a result of comparison with _th , when (ΣT _r −ΣT _p )> T _th , the congestion state is set, and when (ΣT _r −ΣT _p ) ≦ T _th , the congestion release state is set.

The packet receiving unit 500 receives (ΣT _r −Σ
When T _p )> T _th occurs, the signal indicating the congestion notification is continuously transmitted to the congestion notification receiving unit 700, but (ΣT _r −Σ
When T _p ) ≦ T _th , the congestion is released, so the transmission of the signal indicating the congestion notification is terminated.

Also, two types of threshold values T _th are given, and T _th and T _th 2 (T _th 1> T _th 2) are set to detect congestion (ΣT
_r −ΣT _p )> T _th 1 to detect the decongestion (ΣT
_r −ΣT _p ) <T _th 2.

In the second and third embodiments described later, the number of stored packets is compared with the threshold value of the set number of packets, or the amount of encoded signals stored is set. The comparison method is the same as that of the threshold value of the amount of the encoded signal.

Further, when the time-out of the timer is used, the congestion notification is started when the time-out occurs, and when the time-out does not occur next, the congestion is released and the congestion notification is ended.

Next, the interval of generation of the congestion notification packet will be described.

A case where only congestion notification is performed will be described.

When a signal from the congestion notification unit 700 is received during the time T _s set as shown in FIG. 2, a congestion notification packet is generated every time T _s . As shown in FIG. 2, even if the signal reception is interrupted, if the signal is received during the time T _s , a congestion notification packet is generated.

As another method, as shown in FIG. 3, when the congestion notification packet is not generated for the time T _s or more, (a) the packet receiving unit 500 in order to quickly notify the congestion. When receiving the signal from, the congestion notification packet is immediately generated. (B) After that, the set time T
_When a signal from the congestion notification transmitting unit 700 is received during _s , a congestion notification packet is generated every time T _s .

Further, the case of performing the congestion notification and the congestion release notification will be described.

As shown in FIG. 4, when a signal from the congestion notifying section 700 is received during the set time T _s , a congestion notifying packet is generated, and thereafter, the congestion notifying section 700 outputs at every time T _s. May be monitored and a congestion release notification packet may be generated if no signal is received during the time T _s . The congestion notification packet is generated either when the last packet generated before that is the congestion cancellation notification packet or when the congestion notification packet is not generated even once. The congestion release notification packet is generated when the last generated packet before that is the congestion notification packet.

As another method, as shown in FIG. 5, (a) when a signal from the packet receiving unit 500 is received, a congestion notification packet is immediately generated. (B) After that, when the signal from the congestion notifying unit 700 is not received once at every set time T _s , the congestion release packet is generated.

The congestion notification packet is generated by
Either the last packet generated before that is a congestion release notification packet, or the congestion notification packet has never been generated.

The congestion release notification packet is generated when the last generated packet before that is the congestion notification packet.

In this embodiment, the transmission terminal and the reception terminal are separated for simplification of description. However, if the terminal performs simultaneous transmission and reception, congestion notification information may be added to the transmission packet. Good. In this case, congestion notification information is added between the shaded lines shown in FIGS. That is, thereafter the time corresponding to the transmission of the congestion notification packet, the packet to be transmitted during the T _s times adding information of congestion notification (FIGS. 2 and 3). Alternatively, congestion notification information is added to the packet transmitted between the generation of the congestion notification packet and the generation of the congestion release packet (FIGS. 4 and 5).

The generation of the congestion notification packet is also performed in the second and third embodiments described later, but the method is the same.

Next, the control of the transmission bit rate will be described.

A case where the congestion notification only notifies will be described.

The basic control is as follows. As shown in FIG. 6, when the packet transmitter 300 receives a signal from the congestion notification receiver 400 during the time T ₀ , the packet transmitter 300 reduces the transmission bit rate. Conversely, during time T ₁ ,
If no signal is received from the congestion notification receiving unit 400,
Increase the transmission bit rate. The times T ₀ and T ₁ are provided to adjust the control sensitivity. However, as shown in FIG. 7, after the transmission bit rate is reduced by one step, the notification receiving unit 400 is operated within the time T ₀ or more and T ₁ or less.
Immediately after receiving the signal, the transmission bit rate is reduced by one step. The number of control steps of the transmission bit rate is an integer of 2 or more. Further, when the transmission bit rate is reduced, it may be reduced by two steps or more at a time. Further, the time T ₀ may be a function of the magnitude of the transmission bit rate, which is the time T ₁ .

In addition to the control shown in FIGS. 6 and 7, the following control may be performed in order to adjust the control sensitivity.

As shown in FIG. 8, when the transmission bit rate is the maximum rate, as soon as the signal is received from the congestion notification receiving section 400, the transmission bit rate is reduced by one step.

Further, as shown in FIG. 9, after the transmission bit rate is increased, the congestion notification receiving unit 4 is not more than time T _1.
Immediately after receiving the signal from 00, the transmission bit rate is reduced by one step.

When the bit rate control shown in FIGS. 7, 8 and 9 is performed, when the signal is received from the notification receiving section 400 at the next time T ₀ as shown in FIG. 10, the signal is ignored. , The control is started after the time T ₀ .

Next, the case where the congestion notification performs both notification and cancellation notification in the control of the transmission bit rate will be described.

The transmission line interface control section 110 of the transmitting terminal 101 transmits a signal indicating congestion to the congestion notification receiving section 400 from the reception of the congestion notification packet transmitted by the receiving terminal 102 to the reception of the congestion release notification packet. Keep doing

Next, a method of changing the transmission bit rate will be described.

To change the transmission bit rate, a method of changing the packet length, a method of changing the packet transmission interval, or a method of performing both of them at the same time is used.

Next, the case of performing real-time video / audio communication will be described.

The transmission bit rate is changed by changing the bit rate of the encoded video / audio. The bit rate of the coded video can be changed by changing the quantization width and the coded frame rate. Also, the voice coding rate is, for example, ITU TS G.264. 6 in the case of 722 encoding
The coding rate can be changed in three steps of 4, 56 and 48. In addition, ITU TS G. 711 (64 kbps) to G.711. It is possible by changing to 728 (16 kbps). In the case of video / audio communication, in order to minimize packetization delay, rather than changing the packet transmission interval,
Change the packet length. Alternatively, the packet transmission interval is changed within a range in which the packetization delay does not exceed the allowable value.

Next, a second embodiment of the present invention will be described.

FIG. 11 is a block diagram showing the configuration of the second embodiment of the present invention. The embodiment shown in FIG. 11 differs from the first embodiment shown in FIG. 1 only in that an encoder 310 is added to the transmitting terminal 101 and a decoder 510 is added to the receiving terminal 102. Yes, the other configurations are the same, and the same reference numerals are given to the same components.

FIG. 15 shows the operation of the embodiment shown in FIG.
This will be described with reference to the flowchart shown in FIG.

The connectors 120/121 of the transmitting terminal 101 and the receiving terminal 102 supply signals on the transmission path 123 to the transmission path interface control section 110/130. The transmission path interface control unit 110/130 carries out a process of fetching a packet whose destination address matches its own address. The transmission path interface control unit 110/130 adds its own address to the packet transferred from the packet transmission unit 300 / congestion notification transmission unit 700, and the connection unit 120/12
1 and supplies it to the transmission path 123.

The encoded signal is supplied from the encoder 310 to the packet transmitter 300. The packet transmission unit 300 packetizes the encoded signal at a set time interval and transfers it to the transmission path interface control unit 110. Further, the transmission time interface Tp is _defined as the transmission time interval T _p , the coding time of the encoder and the destination address as the generation time interval.
The address of 30 is added as packet information and transferred to the transmission line interface control unit 110, and the transmission line 1 is transmitted from the transmission line interface control unit 110 via the connector 120.
23 (step 1200). Note that the other method of notifying the receiving terminal of the transmission time interval T _p has been described in the first embodiment, but in the case of this embodiment, the value of T _p is not changed during communication. The method of notifying the coding rate is the same as the method of notifying the transmission time interval of the first embodiment.

The packet transmitted from the transmission terminal 101 is taken into the transmission path interface control unit 130 of the reception terminal 102 via the connector 121 and transferred to the packet reception unit 500 (step 1210). The packet receiving unit 500 temporarily stores the transferred packet in the buffer. The number stored in the buffer is a set value. When the set number of packets are accumulated in the buffer, the packet receiving unit 500 starts to transfer the encoded signal to the decoder 510 at the same rate as the encoding rate (step 1220). When the transmission delay increases, the arrival of packets is delayed and the number of packets stored in the buffer decreases. Each time a packet is received, the packet receiving unit 500 detects the number of accumulated packets, compares the number with a preset threshold value, and transmits a signal to the congestion notification transmitting unit 700 (step 1230). Upon receiving the signal, the congestion notification transmitter 700 generates a congestion notification packet to notify the congestion (step 1240). The generated congestion notification packet is added with the address of the transmitting terminal 101 as a destination address, transferred to the transmission path interface control unit 130, and transmitted to the transmission path 123 via the connector 121 (step 1250). The method of comparing the number of accumulated packets and the threshold value is the same as the method of comparing (ΣT _r −ΣT _p ) and the threshold value T _th in the first embodiment. Also, the interval of generation of the congestion notification packet is the same as in the first embodiment.

The transmission line interface control unit 110 of the transmission terminal 101 receives the congestion notification packet transmitted by the reception terminal 102 via the connector 120, and the congestion notification reception unit 40
0 (step 1260). Congestion notification receiving unit 4
In 00, when the congestion notification packet is received, the signal is transferred to the packet transmission unit 300. Upon receiving the signal, the packet transmission unit 300 controls the coding rate of the encoder (step 1270) (the control of the coding rate is the same as the control of the transmission bit rate of the first embodiment).

The buffer of the packet receiving unit 500 may store the coded signal extracted from the received packet instead of storing the packet unit. In this case, when the set amount of coded signals is accumulated in the buffer, the coded signals are transferred to the decoder at the same speed as the coding speed. As the transmission delay increases, the amount of coded signals in the buffer decreases due to the delayed arrival of packets. Each time the packet reception unit 500 newly stores the coded signal extracted from the received packet in the buffer, the packet storage amount is detected and compared with the set threshold value.

Next, a third embodiment of the present invention will be described.

FIG. 12 is a block diagram showing the configuration of the third embodiment of the present invention. The third embodiment shown in FIG. 12 is
In the embodiment shown in FIG. 1, the video encoder 320 and the audio encoder 330 are added to the transmitting terminal 101, and the video decoder 520 and the audio decoder 53 are added to the receiving terminal 102.
Only the addition of 0 is different, the other configurations are the same, and the same components are denoted by the same reference numerals.

Next, the operation of the third embodiment shown in FIG. 12 will be described with reference to the flowchart of FIG.

The connectors 120/121 of the transmitting terminal 101 and the receiving terminal 102 supply the signals on the transmission path 123 to the transmission path interface control section 110/130. The transmission path interface control unit 110/130 performs a process of fetching a packet whose destination address matches its own address. The transmission path interface control unit 110/130 adds its own address to the packet transferred from the packet transmission unit 300 / congestion notification transmission unit 700, and the connection unit 120/12
1 and supplies it to the transmission path 123.

Video encoder 320 and audio encoder 330
Supplies the video coded signal and the audio coded signal to the packet transmitter 300. The packet transmission unit 300 packetizes the coded video signal and the coded audio signal at a set time interval and transfers them to the transmission path interface control unit 110. When packetized, the coded video signal and the coded audio signal may be multiplexed or separated. The packet generation time interval is given as the transmission time interval T _p of the voice packet, the coding rate of the voice encoder and the address of the transmission line interface control unit 130 are added as packet information as the destination address, and the transmission line interface control unit 1 is added.
10 and transmits to the transmission path 123 via the connector 120 (step 1300). The transmission time interval T _p
The method of notifying the receiving terminal of the above is described in the first embodiment, but in the case of the present embodiment, it is assumed that the value of T _p is not changed during communication. The method of notifying the audio coding rate is the same as the method of notifying the transmission time interval of the first embodiment.

The packet fetched by the transmission line interface control unit 130 of the receiving terminal 102 from the transmission line 123 via the connector 121 is transferred to the packet receiving unit 500 (step 1310). In the packet receiving unit 500,
The transferred packets are temporarily stored in a buffer. The number stored in the buffer is a set value. When the video and audio are separately packetized, when the set number of audio packets is accumulated in the buffer in the packet receiving unit 500, the audio decoder 530 receives the audio encoded signal at the encoding rate. The transfer is started at the same speed as (step 1320). When the transmission delay increases, the number of voice packets stored in the buffer decreases because the arrival of packets is delayed. Each time the packet receiving unit 500 receives a voice packet, the number of voice packets accumulated in the buffer is detected and compared with a preset threshold value.
(Step 1330). Upon receiving the signal, the congestion notification transmission unit 700 generates a congestion notification packet to notify the congestion (step 1340). In the generated congestion notification packet, the sending terminal 1 is used as the destination address.
The address of 01 is added, transferred to the transmission path interface control unit 130, and transmitted to the transmission path 123 via the connector 121 (step 1350). The method of comparing the number of accumulated packets and the threshold value is (ΣT _r −Σ in the first embodiment.
The same method as the comparison between T _p ) and the threshold value T _th . Also, the interval of generation of the congestion notification packet is the same as in the first embodiment.

The transmission line interface control unit 110 of the transmission terminal 101 receives the congestion notification packet transmitted by the reception terminal 102 via the connector 120, and the congestion notification reception unit 4
00 (step 1360). When the congestion notification receiving unit 400 receives the congestion notification packet, it transfers a signal to the packet transmitting unit 300 (step 1370). Upon receiving the signal, the packet transmitter 300 receives the signal from the video encoder 3
The coding rate of 30 is controlled (step 1380) (control of the coding rate is the same as the control of the transmission bit rate in the first embodiment). The voice coding speed is not changed.

When the coded video signal and the coded audio signal are multiplexed and packetized, the buffer of the packet receiving unit 500 does not accumulate the data in units of packets but receives the coded audio signal. Accumulate the signal. In this case, when the set amount of coded audio signals is accumulated in the buffer, the coded signals are started to be transferred to the audio decoder 530 at the same speed as the coding speed. As the transmission delay increases, the arrival of packets is delayed and the amount of voice coded signals in the buffer decreases. Each time the packet receiving unit 500 newly stores the coded signal extracted from the received packet in the buffer, the packet storage amount is detected and compared with a preset threshold value, and the congestion notification transmitting unit 700 is notified of the signal. To send.

[0110]

As described above, according to the present invention,
In a packet communication network, a terminal can detect congestion early and for each direction, the processing load for detecting congestion is small, and the traffic for detecting congestion is small.

Further, when congestion is detected, the transmission bit rate of the transmission terminal is controlled so that the increase amount of the transmission delay amount does not exceed the threshold value, so that the increase of the transmission delay can be suppressed. Particularly, for real-time video / audio communication, it is possible to secure real-time property because the coding rate is controlled and the transmission bit rate is controlled.

Further, according to the present invention, even if the transmission bit rate is increased more than when the communication band is reserved, the transmission bit rate can be controlled to the reserved value when congestion is detected. , It is possible to effectively use the communication band of the network. Even if the reservation of the communication band is the upper limit, new communication can be permitted, and the upper limit of the reservation can be increased. Furthermore, since congestion prevention at the terminal can be expected, the congestion control load on the network is reduced.

According to the present invention, the packet transmission time interval of the transmission terminal is transmitted to the reception terminal, and the sum of the reception time interval and the sum of the transmission time intervals of the continuously set number of packets set by the reception terminal are calculated. Difference is detected, compared with a set threshold value, and the transmission terminal is notified according to the comparison,
The receiving terminal can detect that the increase amount of the transmission delay exceeds the set threshold value and notify the transmitting terminal of the detection, so that the terminal can detect the congestion early.
Also, it is possible to detect congestion for each direction. Furthermore, the detection processing is performed by the receiving terminal, does not concentrate on the transmitting terminal, and the increase in packets for congestion detection is limited to notification packets,
Little traffic increase for congestion detection.

Further, according to the present invention, when transmitting encoded video or encoded audio, the encoding speed of the transmitting terminal is transmitted to the receiving terminal, and the number of packets set in the receiving buffer is accumulated in the receiving terminal. Then, decoding is started, the number of packets accumulated in the reception buffer is detected, the number of packets is compared with a threshold value, and the transmitting terminal is notified according to the comparison. That is, the receiving terminal decodes at a rate equal to the encoding rate of the transmitting terminal,
When the amount of transmission delay increases, the number of packets accumulated in the receive buffer decreases because the packets do not arrive. Therefore, when the number of packets accumulated in the receive buffer falls below the set threshold value. To the sending terminal. Therefore, the terminal can detect congestion early. Also, it is possible to detect congestion for each direction. Further, the detection processing is performed by the receiving terminal, is not concentrated on the transmitting terminal, the increase of packets for congestion detection is limited to the notification packets, and the traffic increase for congestion detection is small.

Further, according to the present invention, the packet discard is detected at the receiving terminal, the dummy packet is inserted into the buffer when the packet is discarded, and the packet is accumulated when the accumulated number in the buffer is compared with the set threshold value. Do not count dummy packets as a number. In other words, when packet discard occurs, the number of packets accumulated in the receive buffer remains reduced because the packet does not arrive.
Insert a dummy packet. However, since dummy packets are not counted when congestion is detected, early congestion detection is possible.

According to the present invention, when transmitting encoded video or encoded audio, the encoding speed of the transmitting terminal is transmitted to the receiving terminal, and the receiving terminal accumulates the encoded signal of the amount set in the buffer. Decoding is started, the amount of coded signals accumulated in the buffer is detected, the amount is compared with a threshold value, and the transmitting terminal is notified according to the comparison. That is, the receiving terminal decodes at a rate equal to the encoding rate of the transmitting terminal, but when the transmission delay amount increases, the packet does not arrive, so the amount of encoded signal stored in the buffer decreases. When the amount of coded signals held in the buffer becomes equal to or less than the set threshold value, it is possible to notify the transmitting terminal. Therefore, it is possible to detect congestion at the terminal at an early stage.
Also, it is possible to detect congestion for each direction. Further, the detection processing is performed by the receiving terminal, is not concentrated on the transmitting terminal, and the increase in the number of packets for detecting congestion is only the congestion notification packet, and the increase in traffic for detecting congestion is small.

Further, according to the present invention, when the packet discard is detected at the receiving terminal, the dummy coded signal is inserted into the buffer when the packet is discarded, and the accumulated amount in the buffer is compared with the set threshold value. Does not count the dummy coded signals as the storage amount. That is, when packet discard occurs, since the packet does not arrive, the amount of the coded signal accumulated in the reception buffer remains reduced, so that a dummy coded signal is inserted. However, the amount of dummy encoded signals is not counted when detecting congestion, so that early detection of congestion is possible.

Further, according to the present invention, the transmitting terminal can change one or both of the packet transmission time interval and the packet length, or the window size by receiving the congestion detection notification from the receiving terminal. Since the transmission bit rate is controlled by, the congestion can be prevented and the increase in transmission delay can be suppressed by controlling the transmission bit rate.

Further, according to the present invention, by receiving the notification of the congestion detection from the receiving terminal, the transmitting terminal changes the coding rate of video or audio, and the packet transmission time interval and packet Since either or both of the lengths are changed to control the transmission bit rate, congestion can be prevented, increase in transmission delay of coded video or audio signals can be suppressed, and real-time performance can be secured. can do.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration according to a first exemplary embodiment of the present invention.

[Fig. 2] Fig. 2 is a diagram for explaining a time for notifying congestion.

[Fig. 3] Fig. 3 is a diagram for describing a time for notifying congestion.

[Fig. 4] Fig. 4 is a diagram for explaining a time for notifying congestion.

[Fig. 5] Fig. 5 is a diagram for explaining a time for notifying congestion.

FIG. 6 is a diagram illustrating control of a transmission bit rate of a transmission terminal.

FIG. 7 is a diagram illustrating control of a transmission bit rate of a transmission terminal.

FIG. 8 is a diagram illustrating control of a transmission bit rate of a transmission terminal.

FIG. 9 is a diagram illustrating control of a transmission bit rate of a transmission terminal.

FIG. 10 is a diagram illustrating control of a transmission bit rate of a transmission terminal.

FIG. 11 is a block diagram showing a configuration according to a second exemplary embodiment of the present invention.

FIG. 12 is a block diagram showing a configuration according to a third exemplary embodiment of the present invention.

FIG. 13 is a diagram showing that the sum of the delays of the reception time interval and the transmission time interval is equivalent to the increase amount of the transmission delay.

FIG. 14 is a flow chart showing the operation of the first embodiment shown in FIG.

15 is a flowchart showing the operation of the second embodiment shown in FIG.

16 is a flowchart showing the operation of the third embodiment shown in FIG.

[Explanation of symbols]

 101 Transmitting terminal 102 Receiving terminal 110,130 Transmission line interface control unit 120,121 Connector 123 Transmission line 300 Packet transmitting unit 310 Encoder 320 Video encoder 330 Voice encoder 400 Congestion notification receiving unit 500 Packet receiving unit 510 Decoder 520 Video decoder 530 Audio decoder 700 Congestion notification transmission unit

Claims (14)

[Claims] 1. In a terminal connected to a packet network, the packet transmission time interval of the transmission terminal is transmitted to the reception terminal, and the sum of the reception time intervals of continuously received packets of the number set by the reception terminal and the transmission are transmitted. The difference between the time interval and the sum is detected, the difference is compared with the set threshold value, the receiving terminal notifies the transmitting terminal according to the comparison result, and the transmitting terminal receives the notification and the packet transmission time A congestion prevention method characterized by controlling a transmission bit rate by changing either or both of an interval and a packet length or a transmission window size. 2. When a terminal connected to a packet network transmits coded video or coded audio, the packet transmission time interval of the transmitting terminal is transmitted to the receiving terminal, and the number of consecutive packets set by the receiving terminal is continuously transmitted. The difference between the sum of the reception time interval and the sum of the transmission time interval of the packet received by the above is detected, the difference is compared with the set threshold value, and the receiving terminal notifies the transmitting terminal according to the comparison result, Upon receiving the notification, the transmitting terminal changes the video or audio coding rate, changes one or both of the packet transmission time interval and the packet length according to the change, and controls the transmission bit rate. Congestion prevention method characterized. 3. The step of notifying the receiving terminal of the packet transmitting time interval of the transmitting terminal notifies the packet transmitting time of the transmitting terminal and calculates the difference between the transmitting times of the packets received by the receiving terminal to obtain the transmitting time. The congestion prevention method according to claim 1, wherein the interval is obtained. 4. When a terminal connected to a packet network transmits coded video or coded audio, the coding speed of the sending terminal is transmitted to the receiving terminal, and the receiving terminal receives the number of packets set in the receiving buffer. Is stored and decoding is started, the receiving terminal detects the number of packets in the receiving buffer, compares the number of packets with the set threshold value, and the receiving terminal notifies the transmitting terminal according to the comparison result, and transmits. Upon receiving the notification, the terminal changes the encoding rate of video or audio, changes either or both of the packet transmission time interval and the packet length according to the change, and controls the transmission bit rate. Congestion prevention method characterized. 5. The dummy packet is not counted when the packet discard is detected at the receiving terminal, the dummy packet is inserted into the buffer when the packet discard is detected, and the accumulated number in the buffer is detected. The described congestion prevention method. 6. When a terminal connected to a packet network transmits coded video or coded audio, the coding speed of the transmitting terminal is transmitted to the receiving terminal, and the receiving terminal encodes the amount set in the buffer. The signal is accumulated and decoding is started, the receiving terminal detects the amount of coded signal in the buffer, compares the amount of coded signal with the set threshold value, and the receiving terminal transmits according to the comparison result. The sending terminal notifies the terminal, and the sending terminal changes the video or audio coding rate by receiving the notification, and changes either or both of the packet transmission time interval and the packet length according to the change, and the transmission bit rate. A method for preventing congestion, which is characterized by controlling 7. When the packet discard is detected at the receiving terminal, the dummy coded signal is inserted into the buffer when the packet is discarded, and the accumulated amount in the buffer is detected, the amount of the dummy coded signal is not counted. The congestion prevention method according to claim 6, which is characterized in that. 8. In a communication system connected to a packet network, a means for transmitting a packet transmission time interval of a transmitting terminal to a receiving terminal, and a receiving time interval of packets received continuously by a number set by the receiving terminal. Means for detecting the difference between the sum and the sum of the transmission time intervals, comparing the difference with the set threshold value, and notifying the receiving terminal of the transmitting terminal, and the transmitting terminal transmitting the packet by receiving the notification. And a means for controlling a transmission bit rate by changing either or both of a time interval and a packet length, or a transmission window size. 9. In a communication system connected to a packet network, when transmitting coded video or coded voice, a means for notifying a receiving terminal of a packet transmission time interval of the transmitting terminal, , The difference between the sum of the reception time intervals of the packets received continuously and the sum of the transmission time intervals is detected, and the difference is compared with the set threshold value, and the reception terminal transmits to the transmission terminal according to the comparison result. The means for notifying and the transmitting terminal change the encoding speed of video or audio by receiving the notification, change either or both of the packet transmission time interval and the packet length according to the change, and transmit bit rate And a means for controlling the packet communication system. 10. The means for notifying the receiving terminal of the packet transmitting time interval of the transmitting terminal, by notifying the packet transmitting time of the transmitting terminal and calculating the difference between the transmitting times of the packets received by the receiving terminal, 10. The packet communication system according to claim 8 or 9, further comprising means for determining a transmission time interval. 11. In a communication system connected to a packet network, when transmitting encoded video or encoded audio, a means for transmitting the encoding speed of a transmitting terminal to a receiving terminal and a receiving buffer set in the receiving terminal are set. A means for accumulating the number of packets and starting decoding, and the receiving terminal detecting the number of packets in the receiving buffer, comparing the number of packets with a set threshold value, and notifying the transmitting terminal according to the comparison result. And the transmitting terminal changes the video or audio coding rate by receiving the notification, changes one or both of the packet transmission time interval and the packet length according to the change, and changes the transmission bit rate. A packet communication system comprising: means for controlling. 12. A method of detecting packet discard at a receiving terminal, inserting dummy packets into a buffer when packet discard is detected, and detecting the accumulated number in the buffer,
The packet communication system according to claim 11, further comprising means for controlling the dummy packets so that they are not counted. 13. In a communication system connected to a packet network, when transmitting encoded video or encoded voice, a means for transmitting the encoding speed of a transmitting terminal to a receiving terminal, and an amount set in a buffer at the receiving terminal. Means for accumulating the encoded signal of and starting decoding, and the receiving terminal detecting the amount of the encoded signal in the buffer, comparing the amount of the encoded signal with the set threshold value, and comparing the result The receiving terminal notifies the transmitting terminal according to the above, and the transmitting terminal changes the video or audio coding rate by receiving the notification, and either or both of the packet transmission time interval and the packet length are adjusted according to the change. And a means for controlling the transmission bit rate, the packet communication system. 14. A method of inserting a dummy coded signal into a buffer at the time of detecting packet discard at the receiving terminal and detecting the accumulated amount in the buffer when the packet is discarded,
14. The packet communication system according to claim 13, further comprising means for controlling the quantity of the dummy coded signals so as not to count them.