JP2009278532A - Transmission apparatus and congestion control method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce the number of transmission packets to be discarded at a transmission apparatus. <P>SOLUTION: A transmission apparatus includes: a control section for generating a transmission packet to be transmitted to an external device on the basis of a request from a host device; and a transmission processing section for storing in a buffer transmission packets supplied from the control section, scheduling the transmission packets and transmitting them to the external device. The transmission apparatus further includes a transmission threshold setting means which variably sets a transmission threshold, for determining whether to discard the transmission packet to be supplied to the transmission processing section, to be compared with the number of signals of the transmission packet. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a transmission apparatus and a congestion control method.

  In a mobile communication system, when an RNC (Radio Network Controller) receives a transmission request from an MSC (Mobile Switching Center), which is a host device, the RNC (Radio Network Controller) receives the transmission request from a BS (external device). (Base Station: radio base station).

  FIG. 1 is a functional block diagram illustrating an example of a transmission device unit in a conventional wireless network control device. In FIG. 1, the wireless network control device 10 includes a control unit (CPU) 11, a relay unit 12, a transmission processing unit (DSP) 13, and a buffer 14.

  The control unit 11 receives a transmission request from the host device 15 and performs a congestion check, divides the transmission data attached to the transmission request, maps it to a transmission packet of a predetermined format, and generates a transmission request for the transmission processing unit 13 The data is transferred to the transmission processing unit 13 via the relay unit 12.

  The transmission processing unit 13 temporarily stores the supplied transmission packet in the buffer 14, reads the transmission packet from the buffer 14 and transmits it to the external device 16 when the transmission timing according to scheduling is reached.

Note that normal operation is performed when the buffer data volume is smaller than the low level threshold value, and the flow rate is regulated when the buffer data volume is between the high level threshold value and the low level threshold value. There is a buffer control technique for stopping the inflow of data to the buffer when is larger than a high level threshold (see Patent Document 1).
JP-A-10-327168

  The congestion check, that is, congestion control in the conventional control unit 11 monitors the transmission amount (number of transmission packets) transferred to the transmission processing unit 13 per unit time, and when the transmission amount exceeds a threshold value (fixed value), The transmission packet is discarded without being transferred to the transmission processing unit 13.

  In such congestion control, since the threshold is set to about 80% of the maximum capacity of the transmission processing unit 13, the control unit 11 transmits the transmission packet before the transmission processing unit 13 exhibits the maximum capacity (100%). It will be discarded. For this reason, when the load temporarily increases and exceeds a threshold value, there is a problem that a call loss occurs due to the discard of the transmission packet, and the communication quality is immediately deteriorated.

  Further, when the threshold value for the congestion control is set to the maximum capacity (100%), the transmission amount is in a state where the transmission amount continues to be in the state of the limit load (the instantaneous maximum capacity of the transmission processing unit 13). If the maximum capacity (100%) is exceeded momentarily, there is a problem that malfunction occurs due to the capacity of the transmission processing unit 13 being over.

  An object of the disclosed transmitting apparatus is to reduce the number of discarded transmission packets.

A transmission device according to an embodiment of the disclosure includes a control unit that generates a transmission packet to be transmitted to an external device based on a request from a higher-level device, and stores the transmission packet supplied from the control unit in a buffer and schedules the transmission packet. In a transmission apparatus having a transmission processing unit for transmitting to the apparatus,
Transmission threshold setting means for variably setting a transmission threshold to be compared with the number of signals of the transmission packet for determining whether or not to discard the transmission packet to be supplied to the transmission processing unit.

  Preferably, the transmission threshold setting means is capable of transmitting, by the transmission processing unit, the accumulated signal number obtained by integrating the number of transmission packet signals supplied to the transmission processing unit during the past predetermined time. When the transmission packet number is less than the integrated value that can be transmitted, the transmission processing unit sets a transmission threshold value that is the number of signals that can be continuously processed by the transmission processing unit, and the integrated signal number can be transmitted. When the accumulated value exceeds a transmission margin signal number that is a difference between the accumulated signal number and the transmittable integrated value is less than a margin value that is a difference between the operation limit threshold and the transmittable threshold of the transmission processing unit. A value obtained by adding the number of transmission margin signals to the transmission threshold is set as the transmission threshold, and when the number of transmission margin signals exceeds the margin value, a previous operation limit threshold is set as the transmission threshold.

A congestion control method according to an embodiment of the disclosure includes a control unit that generates a transmission packet to be transmitted to an external device based on a request from a host device, and a transmission packet supplied from the control unit is stored in a buffer and scheduled. In a congestion control method for a transmission device having a transmission processing unit for transmission to an external device,
A transmission threshold value to be compared with the number of signals of the transmission packet for determining whether or not to discard the transmission packet supplied to the transmission processing unit is variably set.

  According to the disclosed transmission device, the number of discarded transmission packets can be reduced.

  Embodiments will be described below with reference to the drawings.

<Configuration of transmitter>
FIG. 2 is a functional block diagram of an embodiment of a transmission device unit in the radio network control device. In FIG. 1, the wireless network control device 20 includes a control unit (CPU) 21, a relay unit 22, a transmission processing unit (DSP) 23, a timer 24, a memory 25, and a buffer 26.

  The control unit 21 includes a transmission request processing unit 31 and a transmission processing unit 32. In the transmission request processing unit 31, the request reception unit 31 a receives a transmission request from the higher-level device (MSC) 27.

  The congestion check unit 31b performs a congestion check by comparing the number of transmission requests generated by the transmission request unit 31d with the transmission threshold value read from the memory 25, and discards the transmission request when the number of transmission requests exceeds the transmission threshold value. To do.

  The transmission data setting unit 31 c divides the transmission data associated with the transmission request, maps the transmission data to a transmission packet of a predetermined format having a fixed length, for example, and generates a transmission packet to be transferred to the transmission processing unit 13. The transmission request unit 31 d transfers the transmission packet generated by the transmission data setting unit 31 c to the transmission processing unit 23 via the relay unit 22.

  The timer 24 measures a unit time such as 1 second, for example, generates a timeout for each unit time, and notifies the transmission number calculation unit 32 a of the transmission processing unit 32.

  In the memory 25, a hardware operation limit threshold value α, a hard transmission possible threshold value β, and a hard bufferable signal number γ are preset, and in addition to this, a past transmission number, a transmission threshold value, and the like are stored. The values α, β, and γ are input and set from a control console (not shown) attached to the wireless network control device 20 or the host device 27.

  The transmission number calculation unit 32 a of the transmission processing unit 32 calculates the number of transmissions of transmission packets transferred from the transmission request unit 31 d to the transmission processing unit 23 every time a timeout is notified from the timer 24, and stores it in the memory 25.

  The congestion determination unit 32b performs congestion determination based on the hardware operation limit threshold value α, the hard transmission threshold value β, the hard bufferable signal number γ, and the transmission packet transmission number read from the memory 25. The transmission threshold setting unit 32 c sets a transmission threshold based on the determination result of the congestion determination unit 32 b and stores the transmission threshold in the memory 25.

  The reception unit 33 a in the transmission processing unit 23 receives the transmission packet supplied via the relay unit 22. The buffer determination unit 33b determines whether or not the buffer 26 is full. If the buffer 26 is full, the received transmission packet is discarded. If the buffer 26 is not full, the transmission packet received by the buffer storage unit 33c is stored in the buffer 26.

  The scheduling unit 33d performs scheduling of transmission packets to be transmitted according to the order in which the transmission packets are received, the priority of the transmission packets, and the like. When the transmission timing by the scheduling is reached, the buffer extraction unit 33e stores the transmission packets in the buffer 26. The transmission packet is taken out from the transmission unit 33f and transmitted from the transmission unit 33f to the external device (BS) 28.

<Control image>
FIG. 3 shows a control image of this embodiment. In the figure, the horizontal axis represents time, and the vertical axis represents load (the number of transmission requests transmitted by the transmission request unit 31d).

  The transmission processing unit 23 performs buffering of transmission packets using the buffer 26. The transmission processing unit 23 can continuously process the hardware transmission possible threshold value β and the instantaneous maximum capacity of the transmission processing unit 23. When a further transmission request is made, there is a hardware operation limit threshold value α that causes the malfunction of the transmission processing unit 23 to cause malfunction.

  In the present embodiment, the integrated flow rate within a predetermined time retroactive from the present time is monitored, and thereby the congestion is controlled by changing the transmission threshold in the control unit 21 so that the transmission processing unit 23 can exert its full capacity.

  That is, when the integrated flow rate is small and the buffer 26 has an empty space, the transmission threshold value is raised to the hardware operation limit threshold value α of the transmission processing unit 23, and when the load continues and the integrated flow rate is large and the buffer 26 has no empty space, the transmission threshold value is increased. By reducing the transmission processing unit 23 to the hard transmission possible threshold value β, it is possible to reduce discarding of the transmission packet in the transmission request processing unit 31 while remaining the capability of the transmission processing unit 23.

<Value definition>
In this embodiment, each value is defined as follows. The number of transmitted packets is represented by TB (Transfer Block).

  Hard operation limit threshold value α [TB / sec]: The instantaneous maximum capacity of the transmission processing unit 23, and if a transmission request higher than this is made, the capacity of the transmission processing unit 23 is exceeded and a malfunction occurs per unit time. Number of packets.

  Hard transmission possible threshold β: [TB / sec]: The number of packets per unit time that the transmission processing unit 23 can continuously process using the buffer 26. However, β <α.

  Hard bufferable signal number γ [TB / sec]: This is the number of packets per unit time that can be buffered to allow a certain amount of burst (temporary load increase).

  Accumulated time s [sec] retroactive from the threshold calculation time: This is the time that the transmission processing unit 23 can tolerate without discarding the transmission packet even if the maximum load continues, and is expressed as γ / (α−β) [sec]. The

  Number of signals t (i) [TB]: the number of packets supplied to the transmission processing unit 23 in unit time i, and a value for estimating the load status (transmission number, buffering number) of the transmission processing unit 23 .

  Hard capacity margin value u: The number of packets per unit time that is acceptable if stored in the buffer 26 is temporary, and is expressed by α-β [TB / sec].

  Accumulated signal number A: The total number of packets per unit time for the accumulated time s, and is represented by A = t (1) +... + T (s) [TB].

  Hardware transmittable integration value B: The number of packets that can be transmitted in hardware for the integration time s at the time of threshold calculation, and is represented by s × β [TB].

  Number of remaining transmission signals C: The number of packets considered to have a margin within the retroactive time, and is represented by C = B−A [TB].

<Transmission threshold control process>
FIG. 4 shows a flowchart of an embodiment of a transmission threshold value control process executed by the transmission processing unit 32. This process is started when there is a time-out notification from the timer 24.

  In step S11, the transmission number calculation unit 32a calculates the integrated signal number A. Next, in step S12, it is determined whether the accumulated signal number A is equal to or greater than the hard-transmittable accumulated value B and is congested.

  If the accumulated signal number A is greater than or equal to the hard-transmittable integrated value B, the transmission threshold value setting unit 32c sets the hard-transmittable threshold value β as the transmission threshold value and writes it in the memory 25 in step S13. In step S14, the time i for managing the transmission cycle is updated, and the process is terminated.

  On the other hand, if the integrated signal number A is less than the hard-transmittable integrated value B and is not congested, the process proceeds to step S15, and the transmission threshold setting unit 32c calculates the transmission surplus signal number C. In step S16, the transmission threshold value setting unit 32c determines whether or not the number C of remaining transmission power signals is smaller than the hardware capability margin value u.

  If the transmission capacity signal number C is smaller than the hardware capability margin value u (slightly congested), the value obtained by adding the transmission capacity signal number C to the hard transmission enable threshold value β is set as the transmission threshold value in step S17 and written to the memory 25. Include. In step S14, the time i for managing the transmission cycle is updated, and the process is terminated.

  On the other hand, if the number C of remaining transmission power signals is equal to or greater than the hardware capability margin value u (non-congested), the hardware operation limit threshold value α is set as the transmission threshold value and is written in the memory 25 in step S18. In step S14, the time i for managing the transmission cycle is updated, and the process is terminated.

<Transmission control process>
FIG. 5 shows a flowchart of an embodiment of a transmission control process executed by the transmission request processing unit 31. This process is started when the request receiving unit 31a receives a transmission request from the host device 27.

  In step S21, the congestion check unit 31b determines whether or not the number of transmissions transmitted from the transmission request unit 31d to the transmission processing unit 23 is less than the transmission threshold read from the memory 25. The transmitted number is reset to zero every unit time.

  When the transmitted number is less than the transmission threshold value, the process proceeds to step S22, and the number of transmission packets generated from the transmission request from the host device 27 is added to the transmitted number to be updated. In step S23, the transmission request unit 31d transmits the transmission packet generated by the transmission data setting unit 31c to the transmission processing unit 23, and ends the process.

  On the other hand, if the transmitted number is equal to or greater than the transmission threshold value, the process proceeds to step S24, where the transmission packet generated from the transmission request from the higher-level device 27 is discarded, and log information indicating that this transmission packet is discarded is stored in, for example, the higher-level device 27. The log is collected by notification or stored in the memory 25, and the process ends.

<Description of Transmission Threshold Variable Example>
Here, for example, when the hardware operation limit threshold value α = 10000 [TB / sec], the hard transmission possible threshold value β = 8000 [TB / sec], and the hard bufferable signal number γ = 4000 [TB] are set in the memory 25. explain. In this case, the integration time s = 4000 / (10000−8000) = 2 [sec].

  The transmission threshold calculation in each case in this situation will be described.

  FIG. 6 shows a control image of the first case where the number of signals t (2) = 5000 [TB] and t (1) = 8500 [TB].

From the condition of t (2) + t (1) <2 × β and 2 × β− (t (2) + t (1)) ≧ α−β,
5000 + 8500 <2 × 8000 and 2 × 8000− (5000 + 8500) ≧ 10000−8000,
Since the condition is satisfied when 13500 <16000 and 16000-13500 ≧ 2000,
Transmission threshold = α
= 10000
Set.

  FIG. 7 shows a control image of the second case where the number of signals t (2) = 7000 [TB] and t (1) = 8500 [TB].

From the condition of t (2) + t (1) <2 × β and 2 × β− (t (2) + t (1)) <α−β,
7000 + 8500 <2 × 8000 and 2 × 8000− (7000 + 8500) <10000−8000,
Since the condition is satisfied when 15500 <16000 and 16000-15500 <2000,
Transmission threshold = β + {2 × β− (t (2) + t (1))}
= 8000 + {2 × 8000− (7000 + 8500)}
= 8500
Set.

  FIG. 8 shows a control image of the third case where the number of signals t (2) = 8500 [TB] and t (1) = 1000 [TB].

From the condition of t (2) + t (1) ≧ 2 × β,
Since the condition is satisfied when 8500 + 10000 ≧ 16000,
Transmission threshold = β
= 8000
Set.

<Operation example during congestion control>
FIG. 9 shows an operation example during congestion control. Here, for example, when the hardware operation limit threshold value α = 10000 [TB / sec], the hard transmission possible threshold value β = 8000 [TB / sec], and the number of hard bufferable signals γ = 4000 [TB] are set in the memory 25. explain. In this case, the integration time s = γ / (α−β) = 2 [sec]. In the horizontal bar shown in the figure, the number of remaining power signals is indicated by right-down hatching, and the number of discarded signals is indicated by left-down hatching.

  1st: The transmission request number of the transmission data setting unit 31c is 6000 [TB], the transmission number of the transmission request unit 31d is 6000 [TB], and the discard number of the congestion check unit 31b is 0 [TB], and t (2) + t (1 ) = 0, so transmission threshold = 10000.

  Second time: transmission request number 9500, transmission number 9500, discard number 0, and t (2) + t (1) = 6000, so transmission threshold = 10000.

Third time: 10000 transmission requests, 8500 transmissions, 1500 discards,
Since t (2) + t (1) = 15500, transmission threshold = 8500
4th: Since the number of transmission requests is 9000, the number of transmissions is 8000, the number of discards is 1000, and t (2) + t (1) = 18000, the transmission threshold value is 8000.

  5th: Transmission request number 5000, transmission number 5000, discard number 0, and t (2) + t (1) = 16500, so transmission threshold = 9500.

  Sixth: Since the number of transmission requests is 12000, the number of transmissions is 10000, and the number of discards is 2000, and t (2) + t (1) = 13000, the transmission threshold is 10000.

  7th: The transmission request number is 10000, the transmission number is 9000, and the discard number is 1000. Since t (2) + t (1) = 15000, the transmission threshold value is 9000.

  Eighth: The transmission request number is 9000, the transmission number is 8000, and the discard number is 1000. Since t (2) + t (1) = 19000, the transmission threshold value is 8000.

  Ninth: Since the number of transmission requests is 7000, the number of transmissions is 7000, the number of discards is 0, and t (2) + t (1) = 17000, the transmission threshold value is 8000.

10th: Since the number of transmission requests is 8500, the number of transmissions is 8500, the number of discards is 0, and t (2) + t (1) = 15000, the transmission threshold value is 9000.
In this case, the total number of discards from the first time to the 10th time is 6500 [TB].

On the other hand, when the transmission threshold value is set to 8000 and fixed as in the prior art,
1st: Transmission request number 6000 [TB], transmission number 6000 [TB], discard number 0 [TB]
Second time: 9500 transmission requests, 9500 transmissions, 1500 discards
Third time: 10000 transmission requests, 8500 transmissions, 2000 discards
4th: 9000 transmission requests, 8000 transmissions, 1000 discards
5th: 5000 transmission requests, 5000 transmissions, 0 discards
6th: Transmission request number 12000, transmission number 10,000, discard number 4000
7th: Transmission request number 10000, transmission number 9000, discard number 2000
8th: Number of transmission requests 9000, number of transmissions 8000, number of discards 1000
9th: Transmission request number 7000, transmission number 7000, discard number 0
10th: The number of transmission requests is 8500, the number of transmissions is 8500, and the number of discards is 500.
In this case, the total number of discards from the first time to the 10th time is 12000 [TB].

  That is, in the operation example shown in FIG. 9, the number of discarded transmission packets can be reduced to about ½ of the conventional number.

  As described above, in this embodiment, when there is a margin in the capacity of the transmission processing unit 23, the burst load equal to or higher than the hard transmission threshold value β is absorbed to enable transmission, and the load continues and the hardware operation of the transmission processing unit 23 continues. When the limit is reached, the control unit 21 restricts transmission to prevent malfunction of the transmission processing unit 23 in advance, so that stable communication is achieved and the transmission processing unit 23 is also capable of handling burst loads. It is possible to operate up to the maximum capacity and reduce the number of discarded transmission packets.

  Further, the control unit 21 can predict the congestion state of the transmission processing unit 23 without providing the transmission processing unit 23 with a congestion detection circuit that detects the congestion state from the number of transmission packets stored in the buffer 26 and notifies the control unit 21 of the congestion state. However, congestion control can be performed according to the situation. Furthermore, compared with the case where a congestion detection circuit is provided on the transmission processing unit 23 side, the control unit 21 can quickly perform congestion control without waiting for a notification from the congestion detection circuit.

Further, even if there is a difference in the resources such as the capacity of the buffer 26, the hard operation limit threshold value α, the hard transmission possible threshold value β, the hard bufferable signal number γ, etc. set in the memory 25 are changed. The transmission threshold value can be calculated and congestion control can be performed without changing the processing shown in FIG.
(Appendix 1)
A transmission unit having a control unit that generates a transmission packet to be transmitted to an external device based on a request from a host device, and a transmission processing unit that stores the transmission packet supplied from the control unit in a buffer, schedules the transmission packet, and transmits the transmission packet to the external device In the device
A transmission apparatus comprising transmission threshold setting means for variably setting a transmission threshold to be compared with the number of signals of the transmission packet for determining whether or not to discard the transmission packet to be supplied to the transmission processing unit.
(Appendix 2)
In the transmission device according to attachment 1,
The transmission threshold setting means includes:
The total number of transmission signals obtained by integrating the number of transmission packet signals supplied to the transmission processing unit in the past predetermined time and the number of transmission packet signals that can be transmitted by the transmission processing unit in the past predetermined time. When the transmission threshold value is less than the value, the transmission threshold value, which is the number of signals that can be continuously processed by the transmission processing unit, is set as the transmission threshold value.
When the number of integrated signals exceeds the transmittable integrated value, an operation limit threshold value that is a transmission surplus signal number that is a difference between the integrated signal number and the transmittable integrated value is an instantaneous maximum capacity of the transmission processing unit; When the transmission threshold is less than a margin value that is a difference from the transmission threshold, a value obtained by adding the transmission margin signal number to the transmission threshold is set as the transmission threshold, and the transmission margin signal number exceeds the margin value Setting the operation limit threshold to the transmission threshold;
A transmission apparatus characterized by the above.
(Appendix 3)
In the transmission device according to attachment 2,
The transmission apparatus according to claim 1, wherein the predetermined time is obtained by dividing the number of bufferable signals that can be stored in the buffer by a difference between the operation limit threshold and the transmission threshold.
(Appendix 4)
A transmission unit having a control unit that generates a transmission packet to be transmitted to an external device based on a request from a host device, and a transmission processing unit that stores the transmission packet supplied from the control unit in a buffer, schedules the transmission packet, and transmits the transmission packet to the external device In the device congestion control method,
A congestion control method characterized by variably setting a transmission threshold value to be compared with the number of signals of the transmission packet for determining whether or not to discard the transmission packet supplied to the transmission processing unit.
(Appendix 5)
In the congestion control method according to appendix 4,
The transmission threshold variable setting is:
The total number of transmission signals obtained by integrating the number of transmission packet signals supplied to the transmission processing unit in the past predetermined time and the number of transmission packet signals that can be transmitted by the transmission processing unit in the past predetermined time. When the transmission threshold value is less than the value, the transmission threshold value, which is the number of signals that can be continuously processed by the transmission processing unit, is set as the transmission threshold value.
When the number of integrated signals exceeds the transmittable integrated value, an operation limit threshold value that is a transmission surplus signal number that is a difference between the integrated signal number and the transmittable integrated value is an instantaneous maximum capacity of the transmission processing unit; When the transmission threshold is less than a margin value that is a difference from the transmission threshold, a value obtained by adding the transmission margin signal number to the transmission threshold is set as the transmission threshold, and the transmission margin signal number exceeds the margin value Setting the operation limit threshold to the transmission threshold;
A congestion control method characterized by the above.
(Appendix 6)
In the congestion control method according to appendix 5,
The congestion control method, wherein the predetermined time is obtained by dividing the number of bufferable signals that can be stored in the buffer by the difference between the operation limit threshold and the transmittable threshold.

It is a functional block diagram of an example of the transmission apparatus part in the conventional wireless network control apparatus. It is a functional block diagram of one Embodiment of the transmission apparatus part in a wireless network control apparatus. It is a figure which shows the control image of this embodiment. It is a flowchart of one Embodiment of a transmission threshold value control process. It is a flowchart of one Embodiment of transmission control processing. It is a figure which shows the control image of a 1st example. It is a figure which shows the control image of a 2nd example. It is a figure which shows the control image of a 3rd example. It is a figure which shows the operation example at the time of congestion control.

Explanation of symbols

20 wireless network control device 21 control unit 22 relay unit 23 transmission processing unit 24 timer 25 memory 26 buffer 27 host device 28 external device 31 transmission request processing unit 32 transmission processing unit 31a request reception unit 31b congestion check unit 31c transmission data setting unit 31d Transmission request unit 32a Transmission number calculation unit 32b Congestion determination unit 32c Transmission threshold setting unit 33a Reception unit 33b Buffer determination unit 33c Buffer storage unit 33d Scheduling unit 33e Buffer read unit 33f Transmission unit

Claims (5)

A transmission unit having a control unit that generates a transmission packet to be transmitted to an external device based on a request from a host device, and a transmission processing unit that stores the transmission packet supplied from the control unit in a buffer, schedules the transmission packet, and transmits the transmission packet to the external device In the device
A transmission apparatus comprising transmission threshold setting means for variably setting a transmission threshold to be compared with the number of signals of the transmission packet for determining whether or not to discard the transmission packet to be supplied to the transmission processing unit. The transmission device according to claim 1, wherein
The transmission threshold setting means includes:
The total number of transmission signals obtained by integrating the number of transmission packet signals supplied to the transmission processing unit in the past predetermined time and the number of transmission packet signals that can be transmitted by the transmission processing unit in the past predetermined time. When the transmission threshold value is less than the value, the transmission threshold value that is the number of signals that can be continuously processed by the transmission processing unit is set as the transmission threshold value,
When the number of integrated signals exceeds the transmittable integrated value, an operation limit threshold that is a transmission surplus signal number that is a difference between the integrated signal number and the transmittable integrated value is an instantaneous maximum capability of the transmission processing unit; When the transmission threshold value is less than a margin value that is a difference from the transmission threshold value, a value obtained by adding the transmission margin signal number to the transmission threshold value is set as the transmission threshold value, and the transmission margin signal number exceeds the margin value Setting the operation limit threshold to the transmission threshold;
A transmission apparatus characterized by the above. The transmission device according to claim 2, wherein
The transmission apparatus according to claim 1, wherein the predetermined time is obtained by dividing the number of bufferable signals that can be stored in the buffer by a difference between the operation limit threshold and the transmission threshold. A transmission unit having a control unit that generates a transmission packet to be transmitted to an external device based on a request from a host device, and a transmission processing unit that stores the transmission packet supplied from the control unit in a buffer, schedules the transmission packet, and transmits the transmission packet to the external device In the device congestion control method,
A congestion control method characterized by variably setting a transmission threshold value to be compared with the number of signals of the transmission packet for determining whether or not to discard the transmission packet supplied to the transmission processing unit. The congestion control method according to claim 4,
The transmission threshold variable setting is:
The total number of transmission signals obtained by integrating the number of transmission packet signals supplied to the transmission processing unit in the past predetermined time and the number of transmission packet signals that can be transmitted by the transmission processing unit in the past predetermined time. When the transmission threshold value is less than the value, a transmission threshold value that is the number of signals that can be continuously processed by the transmission processing unit is set as the transmission threshold value,
When the number of integrated signals exceeds the transmittable integrated value, an operation limit threshold that is a transmission surplus signal number that is a difference between the integrated signal number and the transmittable integrated value is an instantaneous maximum capability of the transmission processing unit; When the transmission threshold value is less than a margin value that is a difference from the transmission threshold value, a value obtained by adding the transmission margin signal number to the transmission threshold value is set as the transmission threshold value, and the transmission margin signal number exceeds the margin value Setting the operation limit threshold to the transmission threshold;
A congestion control method characterized by the above.

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