JPH1198142A - Method and device for controlling abr communication - Google Patents

Abstract

PROBLEM TO BE SOLVED: To previously avoid the occurrence of congestion in an exchange by detecting congestion time and non-congestion time, comparing a value obtained by increasing or decreasing a rate indication value by a prescribed amount corresponding to each detected state with the current transmission rate of a terminal and informing the terminal of the larger or smaller value as a new transmission permission rate. SOLUTION: A congestion detection control part detects the con-genstion/non- congestion of a buffer memory in accordance with the buffer memory address management state of an address management buffer memory. A transmission permission rate calculation part 45 increases or reduces an average rate value calculated by an average rate calculation part 43 in accordance with the non- congestion/congestion/double congestion information of the buffer memory which is informed of from the congestion detection control part and an input load value calculated by an input load calculation part 42. An expressional cell rate (ER) writing part control part is informed of the calculated transmission permission rate. The ER writing part control part writes the transmission permission rate in a resource management cell RM as an expressional cell rate(ER).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an ABR (Available Bit Rat) applied to packet communication using fixed-length packets or ATM communication using ATM cells.
e) The present invention relates to an ABR communication control method and an ABR communication control device for executing a communication service function.

[0002]

2. Description of the Related Art An ABR communication service is configured such that when a transmitting terminal starts communication, a peak cell rate PCR (Peak Cell Rate) as a maximum transmission rate and a minimum cell rate MCR (Mini) as a minimum required rate.
If the peak cell rate PCR and the minimum cell rate MCR are determined as a result of the declaration and negotiation with the network side with respect to the maximum cell rate PCR, the transmitting terminal is not allowed to transmit at a rate exceeding the peak cell rate PCR. On the other hand, the network side guarantees the transmission terminal side a transmission rate of at least the minimum cell rate MCR, and the transmission terminal side does not exceed the peak cell rate PCR and the minimum cell rate MCR, According to the notification of the resource use status and load status, the transmission rate ACR
By changing (Allowed Cell Rate), the network side can avoid congestion beforehand and recover from the congestion state at an early stage. This is a communication service that can transmit at a high transmission rate when the load is low, and can achieve efficient network operation and reduce cell loss.

[0003] In the ABR communication service, a resource management cell RM (Resource Management C) is used to notify information about network resources to a terminal.
ell). The transmitting terminal sends out a resource management cell RM every time it sends out a certain number of user data cells,
The resource management cell RM reaches the receiving terminal via the ATM network, where it is looped back and returns to the transmitting terminal.
In the meantime, the exchange in the ATM network notifies the transmitting terminal of the information on the network side by writing the resource information (band information or congestion information) in the exchange into the resource management cell RM that passes. The transmitting terminal that has received the resource management cell RM in which the resource information such as the band information and the congestion information is written, determines the transmission rate AC of its own terminal according to the information.
R is recalculated and communication is performed at a rate equal to or lower than the transmission rate ACR.

FIG. 12 shows a format of a resource management cell RM. The resource management cell RM includes a 5-byte header and a 48-byte payload, and has a 53-byte configuration, like the user data cell. GFC in header
/ VPI is used as a flow control GFC in the user network interface (UNI) and as a part of the virtual path identifier in the network node interface (NNI). VPI is a virtual path identifier,
VCI is a virtual channel identifier, and PT is a payload type. For example, “000” indicates a user data cell without congestion, and “110” indicates a resource management cell RM. CLP indicates cell loss priority, and HEC indicates header error control.

The 1-byte RMPROTOCOL I in the 48-byte payload of the resource management cell RM
D is an RM protocol identifier, DIR is a direction identification bit, "0" is an F-RM cell (forward cell), "1" is a B-RM cell.
An RM cell (reverse cell) is shown. Also BN (Backwa
rd Explicit CongestionNot
“infication” is a reverse congestion notification bit of a B-RM cell generated in the ATM exchange or the receiving terminal, and CI (Congestion Indication).
n) is a congestion indication bit, NI (No Increas)
e) is a cell rate non-increasing bit, RA (Request)
Acknowleg indicates a request acknowledge bit not used in the ABR communication service, and Res indicates an unused bit. ER (Explicit Cell Rat)
e) is the explicit cell rate, CCR (Current C
Cell Rate is the current transmission rate, MCR (Mini)
Mum Cell Rate is the minimum cell rate and QL (Queue Le) declared at the time of connection setup.
ngth) is the cue length not used in ABR,
SN (Sequence Number) is a sequence number, and CRC is a cyclic code check bit.

When the transmitting terminal receives the resource management cell RM, the congestion indication bit C in the resource management cell RM
If I is set to "1" (congestion), the transmitting terminal decreases the value of the transmission rate ACR by a fixed value, and if the congestion indication bit CI is set to "0" (non-congestion),
The transmitting terminal increases the value of the transmission rate ACR by a fixed value. Further, the explicit cell rate ER written in the resource management cell RM and the previously calculated transmission rate ACR
And compare the smaller value with the new transmission rate AC
Let it be R. At this time, the transmission rate ACR must be within the range of not more than the peak cell rate PCR and not less than the minimum cell rate MCR.

[0007] The receiving terminal terminates the user data cell transmitted from the transmitting terminal and receives the received resource management cell R.
M is returned and returned to the transmitting terminal. At this time, an explicit forward congestion indication EFCI indicating congestion in the user data cell received immediately before the received resource management cell RM.
(Explicit Forward Congest
If the “ion Indication” bit is set to “1”, the receiving terminal sets “1” to the congestion indication bit CI in the resource management cell RM to be returned, and transmits it.

[0008] There are the following two types of operations on the ATM network side, that is, on the exchange side, for a terminal performing ABR communication, which are called an EFCI mode and an ER mode, respectively. The EFCI mode is an explicit forward congestion indication in user data cells passing through the switch during congestion conditions.
This is an operation mode in which a bit is set to “1” (congestion) and cells are passed. The ER mode is an explicit cell rate ER (explicit cell) that allows the transmitting terminal to transmit according to the resource usage status or congestion status inside the exchange.
Rate) is calculated, and the calculated value is written in a forward (transmitting side → receiving side) or reverse direction (receiving side → transmitting side) resource management cell RM passing through the exchange. In the ER mode, the exchange can generate a resource management cell RM independently of the resource management cell RM transmitted from the transmission terminal and transmit the generated resource management cell RM to the transmission terminal. Cell R
An operation of setting the congestion indication bit CI in M or writing the value of the explicit cell rate ER calculated by the exchange into the resource management cell RM is performed.

Note that the ABR communication service is a communication service in which the transmission interval of cells is appropriately changed according to the congestion state or the band use state of the network. Is a communication service applied similarly. The above operation is performed by the ATM Foru.
m is an ABR communication service that has been standardized, but its specific control method and function implementation means on the network side are not subject to standardization. For example, a congestion state detection method in an exchange, an explicit The calculation procedure of the cell rate ER and the like are not subject to standardization.

[0010]

As described above, the specific operation and control method of the network-side communication control device and exchange are outside the scope of standardization, and the desired functions have not been realized.
Further, in order to provide an ABR communication service as a network, it is necessary to mount a control function for performing the above-described EFCI mode or ER mode operation in a communication control device or a switch on the network side. That is, for the ABR communication service, a new control function not implemented in the conventional ATM exchange or the like is required.

The present invention provides a concrete control method and a function realizing means of a communication control device or an exchange for executing the above-mentioned ABR communication service in an ATM network or a packet network of fixed-length packets. In the mode, the explicit cell rate ER, which is the transmission permission rate to be notified to the transmitting terminal, is set more appropriately, to avoid congestion in the exchange beforehand and to recover quickly from the congestion state, and to increase the utilization rate of the transmission line. An object of the present invention is to provide a communication control method and a communication control device for performing an ABR communication service function in the ER mode that can be achieved.

[0012]

In order to achieve the above object, an ABR communication control method according to the present invention comprises: (1) an ABR communication control method for notifying a terminal of a transmission permission rate; A value is set, and congestion and non-congestion in the buffer memory are detected. When non-congestion is detected, a value obtained by increasing the rate indication value by a predetermined value and the current transmission rate of the terminal are compared, and a larger value is newly set. To the terminal as a transmission permission rate, and at the time of congestion detection, a value obtained by reducing the rate indication value by a predetermined value and the current transmission rate of the terminal. Notification process.

(2) setting a rate indication value corresponding to a route, detecting congestion and non-congestion in the buffer memory, increasing the rate indication value by a predetermined value when non-congestion is detected, and increasing the rate indication when congestion is detected; The method includes a step of comparing a value obtained by reducing the indicated value by a predetermined value with an explicit cell rate value written in the resource management cell and notifying the terminal of a smaller value as a new transmission permission rate to the terminal.

(3) In the detection of congestion or non-congestion in the buffer memory, a congestion state is determined by a plurality of queues of a cell and a rate of change of the queue length per unit time. The method includes a step of dividing the data into levels and performing the operation of calculating the rate instruction value according to each level.

(4) Further, the input load of the buffer memory is calculated from the ratio between the input rate to the buffer memory and the target use bandwidth of the buffer memory, and the average rate of connections passing through the buffer memory is calculated. And detecting a congestion state in the buffer memory and notifying the terminal of a value obtained by increasing or decreasing the average rate according to the congestion state and the input load as a new transmission permission rate to the terminal. .

Further, the ABR communication control device of the present invention provides (5)
A congestion detection control unit for detecting the presence or absence of congestion in the buffer memory, a transmission permission rate writing control unit for notifying the terminal of a transmission permission rate, and a transmission permission rate calculation control unit for calculating the transmission permission rate The transmission permission rate calculation control unit includes a parameter storage unit that stores an increase rate for a rate indication value set for a route when non-congestion is detected by the congestion detection unit and a decrease rate for the rate indication value when congestion is detected. And, when the non-congestion is detected, the value obtained by increasing the rate instruction value by the increase rate read from the parameter storage unit is compared with the current transmission rate of the terminal, and a larger value is set as a new transmission permission rate, And when the congestion is detected, a value obtained by reducing the rate instruction value by the reduced rate read from the parameter storage unit and the current transmission of the terminal. The smaller value by comparing the rate as a new allowed transmission rate, and has a transmission grant rate calculating unit added to the explicit cell rate write control unit.

(6) a congestion detection control unit for detecting the presence or absence of congestion in the buffer memory; an explicit cell rate write control unit for notifying the terminal of a transmission permission rate;
A transmission permission rate calculation control unit that calculates the transmission permission rate, wherein the transmission permission rate calculation control unit includes an increase rate and a congestion detection rate with respect to a rate instruction value set for a route when non-congestion is detected by the congestion detection unit. Sometimes the parameter storage unit storing the decrease rate for the rate instruction value, and the rate instruction value is increased by the increase rate read from the parameter storage unit at the time of non-congestion detection, read from the parameter storage unit at the time of congestion detection A value obtained by comparing the value obtained by reducing the rate indication value by the reduced rate with an explicit cell rate value written in a resource management cell from a terminal, and using the smaller value as a new transmission permission rate, the explicit cell rate And a transmission permission rate calculating unit to be added to the writing control unit.

(7) The transmission permission rate calculation control section classifies the congestion state into a plurality of levels according to a queue length of a cell and a change rate of the queue length per unit time. A storage unit that stores the operation of calculating the rate instruction value for each level, and a transmission permission rate calculation unit that calculates a rate instruction value by an operation that is calculated according to the level of the congestion state read from the storage unit. is there.

(8) a congestion detection control unit for detecting a congestion state in the buffer memory, a transmission permission rate writing control unit for notifying the terminal of a transmission permission rate, and a transmission for calculating the transmission permission rate. A permission rate calculation control unit, wherein the transmission permission rate calculation control unit includes a parameter storage unit storing parameters corresponding to a route and corresponding to congestion or non-congestion, an input rate to a buffer memory for a predetermined period, and a buffer memory. An input load calculator for calculating an input load of the buffer memory from a ratio with a target use bandwidth; an average rate calculator for calculating an average rate of connections passing through the buffer memory; and the buffer memory input load by the input load calculator. New transmission by the average rate calculated by the average rate calculation unit and the congestion state detection signal by the congestion detection control unit. Those having a transmission grant rate calculating section for calculating a variable rate.

(9) The average rate calculator for calculating an average rate of connections passing through the buffer memory selects a connection for which an average rate is to be calculated in accordance with a congestion status detection signal from the congestion detection controller. The average rate can be calculated by using the above-mentioned configuration.

(10) The input load calculating section sets a plurality of target use bands in the parameter storage section as the target use bands according to a congestion state detection signal from the congestion detection control section, and sets each target use band. A configuration for calculating an input load for a band can be provided.

(11) The transmission permission rate calculation unit includes:
The average rate calculated by the average rate calculation unit,
A configuration may be provided in which a value obtained by dividing by the input load calculated by the input load calculation unit is calculated as a transmission permission rate.

(12) The transmission permission rate calculation unit includes:
When the congestion status detection signal by the congestion detection control unit indicates a congestion state, the average rate calculated by the average rate calculation unit, and a value obtained by dividing the average rate by the input load calculated by the input load calculation unit. , And using the smaller value as the transmission permission rate.

[0024]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention is implemented in a communication control device or an exchange used in an ATM network and a packet network of fixed-length packets. Here, an ATM exchange having a common buffer configuration will be described as an example. ATM switch
A switching unit for switching cells from an incoming side route to a plurality of outgoing routes in units of cells as shown in FIG. 2, and switching a cell from a low-speed subscriber line incoming side route as shown in FIG. A multiplexing unit for multiplexing the switching unit or a demultiplexing unit for performing the reverse operation as shown in FIG. 3 is provided. The present invention is applied to any of the switching unit, the multiplexing unit, and the demultiplexing unit shown in FIGS.

The switching unit shown in FIG. 1 includes a common buffer memory 11, a transmission permission rate calculation control unit 12 corresponding to each output route, and a congestion detection control unit 1 corresponding to each output route.
3. Address management buffer memories 14-1 to 14-n corresponding to the respective outgoing routes, an explicit cell rate ER writing control unit corresponding to the outgoing route, which writes the transmission permission rate into the resource management cell RM as the explicit cell rate ER. 15 (route) after the name of each part indicates that the device has a configuration corresponding to the route.

The cells arriving from the incoming route are stored in the common buffer memory 11, and the address information for storing the cells in the common buffer memory 11 is stored in the address management buffer memory 14- corresponding to each outgoing route. 1-14-n
Is managed by The congestion detection control unit 13 controls the buffer memory 1 based on the address management status of the buffer memory 11 by the address management buffer memories 14-1 to 14-n.
1 to detect congestion and non-congestion. The transmission permission rate calculation control unit 12 selects a transmission permission rate in accordance with the congestion / non-congestion detection information from the congestion detection control unit 13 and transfers the calculation result to the explicit cell rate ER write control unit 15. The explicit cell rate ER write control unit 15 writes the explicit cell rate ER in the resource management cell RM.

The multiplexing and demultiplexing units shown in FIGS. 2 and 3 include common buffer memories 21 and 31, transmission permission rate calculation control units 22 and 32 corresponding to each route, and congestion detection control corresponding to each route. Sections 23 and 33, address management buffer memories 24-1 to 24-n and 34-1 to 3 corresponding to respective routes.
34-n, Explicit cell rate E for resource management cell RM
Explicit cell rate ER writing control unit 25 for writing R,
35. The configuration of each unit of the multiplexing unit and the demultiplexing unit is the same as the function of writing the explicit cell rate ER into the resource management cell RM in the switching unit shown in FIG.

FIG. 4 shows a transmission permission rate calculation control unit according to the first embodiment of the present invention. The cell arriving from the incoming side route passes through the cell information extraction unit 41 and then enters the input load calculation unit 4.
2 is input. The cell information extraction unit 41 checks the current transmission rate CCR (Curre) in the arrived resource management cell RM.
ntCell Rate) value, and sends the value to the average rate calculation unit 43. The current transmission rate CCR value is
This is a value in which the transmission rate of the terminal device itself is written when the terminal device transmits the resource management cell RM.

The average rate calculating section 43 calculates the average rate of the passing connection for the respective outgoing routes based on the current transmission rate CCR value transmitted from the cell information extracting section 41 by the following formula. Assuming that the average rate of the connection passing through the egress route i is MRi (i is the egress route number), MRi (new) = a × CCR + (1-a) × MRi (old) (1) , MRi (new) is the average rate calculated this time,
MRi (old) indicates the average rate calculated last time. a
Is a parameter that is stored in the parameter storage unit 44 and that represents the averaging coefficient, has a value of 1 or less, and can be changed by software control. An example of the configuration of the parameter storage unit 44 is shown in FIG.

In FIG. 5, the exit route i (= 1, 2 ·
.. N) correspondingly, average coefficient ai and observation period ti
, Congestion target usage rate ρci, and non-congestion target usage rate ρ
nci is stored. Note that the observation periods ti can all be the same.

Here, the average rate MRi will be described. The purpose of calculating the average rate MRi is to find a rate that is one index for calculating an appropriate transmission permission rate. Giving the average rate MRi as the transmission permission rate for all the connections that pass through is one of the fair bandwidth allocation methods, but simply giving the average rate MRi as the transmission permission rate gives the network congestion state. And the load state is not reflected, either the state is congested or the bandwidth is not used effectively. Therefore, if a value obtained by increasing or decreasing the average rate according to the congestion state or the load state is set as the transmission permission rate, congestion can be avoided and the network can be used efficiently.

Further, even when the transmission permission rate is determined from the average rate according to the congestion state or the load state, it is desirable that the average rate itself is also changed according to the congestion state or the load state. For example, at the time of congestion, it is desired to reduce the transmission permission rate to a lower value. Therefore, it is faster to remove the connection transmitting at a rate higher than the average rate from the target of the average rate calculation, and to converge to the lower value more quickly.
Conversely, when there is no congestion, it is desired to increase the transmission permission rate, so that connections that are transmitting at a rate lower than the average rate are excluded from the target of the average rate calculation, and converge to a higher value sooner. By selecting the connection for which the average rate is to be calculated according to congestion / non-congestion in this way,
It is possible to avoid network congestion or effectively use the network.

That is, when the current transmission rate CCR value is notified to the average rate calculation section 43, the buffer memory is in a congested state and the current transmission rate CCR value <MRi (old)
Or only when the buffer memory is in a non-congested state and the current transmission rate CCR value> MRi (old), the average rate MRi is calculated by the above equation (1).

On the other hand, the input load calculating section 42 calculates the input rate of each output route by counting the number of cells input in a predetermined observation period for each output route. Further, by calculating the ratio between the calculated input rate and a value obtained by multiplying the band of the corresponding output route by the target usage rate (that is, the target usage band), the input load for each output route is calculated. I do. Assuming that the input rate to the outgoing route i is IRi, the bandwidth of the outgoing route i is BWi, and the target usage rate is pi, the input load Li is: IRi = (input cells to the outgoing route i) / (observed Period) (2) Li = IRi / (BWi × ρi) (3)

The unit of each parameter is the number of input cells: “cell”, the observation period: “second”, the input rate: “cell / second”,
The bandwidth of the egress route: “cell / sec, target utilization rate:“ no unit ”, input load:“ no unit. ”If the calculated input load Li is 1 or more, the target of the egress route is It indicates that cells exceeding the used band have arrived, and conversely, the input load Li
Is equal to or less than 1, it indicates that the arriving cell is equal to or less than the target use band of the egress route.

In calculating the input load Li, the target usage rate during congestion and the target usage rate during non-congestion are set to different values, for example, the target usage rate is set to 1 during non-congestion. This makes it possible to set the value of the input load Li to a lower value, and conversely, at the time of congestion, set the target usage rate to 1 or less and set the value of the input load Li to a higher value. That is, the input load Li can have a plurality of values instead of one value for each output side route.

The target usage rate at the time of congestion corresponding to the outgoing side route i is ρ
ci, when the target usage rate at the time of non-congestion is pnci, the input load Lci at the time of congestion and the input load Lnci at the time of non-congestion are:
It is calculated as follows. Lci = IRi / (BWi × ρci) (4) Lnci = IRi / (BWi × ρnci) (5) Each parameter, observation period, target usage rate ρci, ρnci
Are stored in the parameter storage unit 44 as shown in FIG.

Next, the transmission permission rate calculator 45 will be described. The transmission permission rate calculator 45 calculates the average rate calculator according to the information of the non-congestion, congestion, and heavy congestion of the buffer memory notified from the congestion detection controller and the value of the input load calculated by the input load calculator 42. The value of the average rate calculated in 43 is increased or decreased, and the average rate is calculated as a transmission permission rate, and the explicit cell rate ER writing section control sections 15, 25,
Notify 35. The explicit cell rate ER writing unit control units 15, 25, and 35 write the transmission permission rate as the explicit cell rate ER in the resource management cell RM. Note that heavy congestion is a congestion state in which the degree of congestion is particularly severe among congestion states and may be severe enough to cause a system down.

The calculation of the transmission permission rate in the transmission permission rate calculation unit 45 is performed in the case of non-congestion or normal congestion.
A value obtained by dividing the average rate MRi by the input load Li is set as a transmission permission rate. In the case of heavy congestion, the minimum cell rate MCR value of each connection is set as the transmission permission rate. That is, the transmission permission rate Ri for the egress route i is Ri = MRi / Li (6) in the case of non-congestion or normal congestion. Ri = MCR (7) in the case of heavy congestion. .

As in the case of calculating the input load, the target usage rate of the outgoing route is given a different value between normal congestion and non-congestion, and the transmission permission rate Ri differs between non-congestion and congestion. It can have a value. The transmission permission rate Ri in that case is calculated using the input load Lci at the time of congestion or the input load Lnci at the time of non-congestion, in the case of normal congestion Ri = MRi / Lci (8) In the case of non-congestion Ri = MRi / Lnci (9)

When the input load is 1 or less and in a congested state,
The transmission permission rate Ri obtained by the above equation (8) increases from the average rate MRi. Increasing the transmission allowed rate during congestion can further congestion. Therefore, the calculated transmission permission rate is compared with the average rate, and the smaller value is used as the transmission permission rate, so that it is possible to prevent the transmission permission rate from increasing during congestion. That is, in the case of avoiding an increase in the transmission permission rate during congestion, the transmission permission rate Ri is set to Ri = min (MRi, MRi / Lci) (10). Note that min (X, Y) indicates that the smaller of X and Y is selected.

With the above functions, the transmission permission rate is appropriately adjusted according to the congestion state or the input load state, and congestion can be avoided or a quick recovery can be made even if the state becomes congested.

FIG. 6 shows the configuration of a transmission permission rate calculation control unit according to the second embodiment of the present invention. In FIG. 6, a cell arriving from an incoming side route is input to a cell information extracting unit 61. The cell information extraction unit 61 determines that the incoming resource management cell R
Current transmission rate CCR value in M and explicit cell rate ER
The value is extracted and transmitted to the transmission permission rate calculation unit 62. The current transmission rate CCR value is determined by the transmitting terminal when the resource management cell R
When transmitting M, the transmission rate of the transmitting terminal itself is written, and the explicit cell rate ER value is a value written as a transmission permission rate by an exchange in the network on the way. The transmission permission rate calculation unit 62 calculates the transmission permission rate Ri based on these values and information from the parameter storage unit 63 and the congestion detection control unit.

FIG. 7 shows a flowchart of the first calculation of the transmission permission rate calculation control unit according to the second embodiment of the present invention. Hereinafter, the first calculation operation in the transmission permission rate calculation control unit of FIG. 6 will be described with reference to FIG. Each time the resource management cell RM arrives (see FIG. 7), the transmission permission rate calculating section 62 uses the information from the congestion detection control section (see FIGS. The non-congestion information is determined (see FIG. 7), and the fixed rate is subtracted from the preset rate indication value CRi at the time of congestion (see FIG. 7), and the fixed rate is added to the preset rate indication value CRi at the time of non-congestion. (See FIG. 7), or at the time of congestion, 1 is added to the preset rate indication value CRi.
The rate indication value CRi is calculated by multiplying it by the following coefficient and decreasing it by one or more coefficients during non-congestion. These increase parameter and decrease parameter are stored in the parameter storage unit 63 and can be changed by software control.

Next, the transmission permission rate Ri is calculated by the following equation with respect to the rate indication value CRi calculated according to the congestion / non-congestion. In the case of congestion (see FIG. 7) Ri = min (CCR, CRi) (11) In the case of non-congestion (see FIG. 7) Ri = max (CCR, CRi) (12) The transmission permission rate Ri calculated by the equations (11) and (12) is compared with the explicit rate ER written in the arriving resource management cell RM, and the transmission permission rate Ri is further calculated as Ri = min (Ri, Ri, ER in RMcell) (13) (see FIG. 7). Note that min (X,
Y) indicates that the smaller of X and Y is selected, and max (X, Y) indicates that the larger of X and Y is selected.

By calculating the transmission permission rate, the transmission permission rate Ri at the time of congestion is suppressed to the lower value of the current transmission rate CCR and the rate indication value CRi. Conversely, the transmission permission rate Ri at the time of non-congestion is: Current transmission rate CC
A value that is changed to the higher value of R and the rate indication value CRi and that does not exceed the explicit rate ER value written in the arriving resource management cell RM is the explicit cell rate ER write control as the transmission permission rate Ri. The explicit cell rate ER write control unit writes the transmission permission rate Ri as an ER value to the RM cell (see FIG. 7).

In the above-described calculation of the transmission permission rate Ri, the current transmission rate CCR value in the resource management cell RM transmitted by the transmitting terminal is used as the current transmission rate. , And the transmission permission rate can be calculated using the transmission rate of the measurement result.

FIG. 8 is a flowchart of the second calculation of the transmission permission rate calculation control unit according to the second embodiment of the present invention. Each time the resource management cell RM arrives (see FIG. 8), the transmission permission rate calculation unit 62 determines congestion / non-congestion information based on information from the congestion detection control unit (FIG. 8).
At the time of congestion, the preset rate indication value CR
i is subtracted by a fixed rate (see FIG. 8), and when there is no congestion, the fixed rate is added to a preset rate indication value CRi (see FIG. 8). The rate indication value CRi is calculated by multiplying it by a factor of 1 or less and decreasing it, and increasing it by a factor of 1 or more when there is no congestion. The above calculation of the rate instruction value CRi is the same as the above-described first calculation described with reference to FIG.

Next, the calculated rate indication value CRi is compared with the explicit rate ER written in the arriving resource management cell RM, and the transmission permission rate Ri is calculated as Ri = min (CRi, ER in RMcell). ) (14) (see FIG. 8). Then, the calculated transmission permission rate Ri is sent to the explicit cell rate ER writing control unit, and the explicit cell rate ER writing control unit writes the transmission permission rate Ri as an ER value in the RM cell (FIG. 8).
reference).

Using the transmission permission rate Ri calculated according to the second embodiment of the present invention, when the transmitting terminal transmits the resource management cell RM, the transmitting terminal sets the peak cell rate PCR and transmits the cell to the network. However, the explicit cell rate ER value is reduced to an appropriate transmission permission rate in the network on the way. That is, when the exchange receives the resource management cell RM, the explicit cell rate ER value written in the resource management cell RM indicates the rate at which transmission is permitted in the network that has been passed. Only when the calculated rate indication value CRi is lower than the explicit cell rate ER specified elsewhere in the network, a new transmission permission rate is set. Equations (13) and (14)
According to the calculation, the transmission permission rate Ri is not set to a value higher than the explicit cell rate ER value even during non-congestion, so that the probability of congestion becomes lower and congestion can be avoided beforehand.

FIG. 9 shows the parameter storage section 63 described above. Increase rate pi and decrease rate m for the outgoing route i
i is stored. In this case, the increase rate pi and the decrease rate mi can be set to the same value, that is, the value to be decreased during congestion and the value to be increased during non-congestion can be set to the same value. Are the same, the increase rate and the decrease rate can be set to the same value.

In the second embodiment of the present invention, the rate indication value CRi is calculated by increasing or decreasing the increase rate pi or the decrease rate mi according to two states of congestion and non-congestion, as shown in FIG. In addition, the degree of congestion and the tendency of congestion are divided into a plurality of levels to determine the congestion state, and the rate indication value CRi is calculated according to each level, so that the transmission permission rate can be set more finely. Hereinafter, a method of determining the congestion state in a plurality of levels and calculating the rate instruction value CRi according to each level will be described.

FIG. 10 shows the congestion state at the queue length level (Q
LL) and the queue length change rate level (QDL) in a matrix form.
LL) indicates the level of the queue length of the cells in the buffer memory, and the queue length change rate level (QDL) indicates the level of the rate of change of the queue length per unit time. When the queue length level (QLL) is divided into m and the queue length change rate level (QDL) is divided into n, a total of m × n congestion states can be determined corresponding to each level. The calculation of the rate instruction value CRi can employ at most m × n different calculations for each of the m × n congestion states. In the following, n is used to simplify the description.
= 3, m = 3, the calculation of the rate instruction value CRi will be described.

FIG. 11 shows a congestion state operation matrix.
The congestion state operation matrix is obtained by adding the operation of calculating the rate indication value CRi in each congestion state to a state in which the congestion state is arranged in a matrix of the queue length level (QLL) and the queue length change rate level (QDL). And stored in the parameter storage unit 63 as a congestion state operation matrix. The queue length level (QLL) is determined by two queue length thresholds QL1 and QL2.
1), queue length level 2 (QLL2), and queue length level 3 (QLL3). Queue length level 1 (QL
L1) is a state where the queue length is short, queue length level 2 (QL
L2) is a state where the queue length is appropriate, queue length level 3
(QLL3) indicates a state where the queue length is long.

The queue length change rate level (QDL) is based on two queue length change rate thresholds QD1 and QD2, and the queue length change rate level 1 (QDL1) and the queue length change rate level 2
(QDL2) and queue length change rate level 3 (QDL3). Queue length change rate level 1 (QDL1) indicates that the queue length tends to decrease, and queue length change rate level 2
(QDL2) indicates that the queue length is settled to a constant value, and the queue length change rate level 3 (QDL3) indicates that the queue length tends to increase.

Nine types of congestion states are determined according to each queue length level (QLL) and queue length change rate level (QDL), and a maximum of nine types of rate indication values CRi are calculated in accordance with each congestion state. For example, the following three types of calculation operations can be set. Operation 1: CRi = CRi + pi (14) Operation 2: CRi = CRi (15) Operation 3: CRi = CRi-mi (16) Here, pi and mi are shown in FIG. The increase rate and the decrease rate stored in the parameter storage unit. or,
Operation 2 indicates that the rate indication value CRi is not changed.

Each calculation operation is performed by, for example, the congestion level (1, 1) by the operation set for each congestion level shown in FIG.
, Ie, the queue length level 1 (QLL1) and the queue length change rate level 1 (QDL1), that is, the “queue length is short and the queue length is decreasing” state, the rate indication value CRi is obtained by the operation 1. Will be increased. The state of the congestion level (3, 3), that is, the queue length level 3 (QLL3), the queue length change rate level 3 (QDL3)
3) In other words, in the state of “the queue length is long and the queue length is increasing”, the rate indication value CR
Decrease i. State of congestion level (2, 2), ie, queue length level 2 (QLL2), queue length change rate level 2
(QDL2), that is, in the state of “the queue length is appropriate and the queue length has not changed”, the operation 2 does not change the rate instruction value CRi. In this way, the rate indication value CRi can be more finely adjusted by analyzing the congestion situation more finely and setting different calculation operations according to each congestion situation.

[0058]

The ABR communication control method and ABR of the present invention
According to the communication control device, the ER mode in which the communication control device or the switch calculates the transmission permission rate of the transmitting terminal among the operations of the communication control device or the switch performing the ABR communication service, the band on the communication control device or the switch side. Calculates an appropriate transmission permission rate in detail according to the information and the congestion information, notifies the transmitting terminal of the calculated transmission permission rate, and the transmitting terminal transmits according to the notified transmission permission rate. Congestion can be avoided. Also, even when the transmission terminal is in a congestion state, it can be recovered at an early stage, and the transmitting terminal can transmit at a high transmission rate in the non-congestion state and the input light load state. Can be enhanced. The present invention can be similarly applied to an ABR communication service in a packet network using fixed-length packets in addition to an ATM network, to avoid network congestion beforehand, to recover quickly from a congestion state, and to improve transmission path use efficiency. Can be improved.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram of a switching unit according to an embodiment of the present invention.

FIG. 2 is an explanatory diagram of a multiplexing unit according to the embodiment of the present invention.

FIG. 3 is an explanatory diagram of a demultiplexing unit according to the embodiment of the present invention.

FIG. 4 is an explanatory diagram of a transmission permission rate calculation control unit according to the first embodiment of this invention.

FIG. 5 is an explanatory diagram of a parameter storage unit in the transmission permission rate calculation control unit according to the first embodiment of this invention.

FIG. 6 is an explanatory diagram of a transmission permission rate calculation control unit according to the second embodiment of this invention.

FIG. 7 is a flowchart of a first calculation of a transmission permission rate calculation control unit according to the second embodiment of the present invention.

FIG. 8 is a flowchart of a second calculation of a transmission permission rate calculation control unit according to the second embodiment of the present invention.

FIG. 9 is an explanatory diagram of a parameter storage unit in a transmission permission rate calculation control unit according to the second embodiment of this invention.

FIG. 10 is an explanatory diagram of a congestion state matrix in a transmission permission rate calculation control unit according to the second embodiment of this invention.

FIG. 11 is an explanatory diagram of a congestion state operation matrix in a transmission permission rate calculation control unit according to the second embodiment of this invention.

FIG. 12 is an explanatory diagram of a format of a resource management cell RM.

[Explanation of symbols]

 11 Common Buffer Memory 12 Transmission Permission Rate Calculation Control Unit 13 Congestion Detection Control Unit 14-1 to 14-n Address Management Buffer Memory 15 Explicit Cell Rate ER Write Control Unit

Claims (12)

[Claims] 1. An ABR communication control method for notifying a terminal of a transmission permission rate, comprising setting a rate indication value corresponding to a route, detecting congestion and non-congestion in a buffer memory, and detecting the congestion or non-congestion in a buffer memory. By comparing the value obtained by increasing the rate indication value by a predetermined value with the current transmission rate of the terminal, the larger value is notified to the terminal as a new transmission permission rate, and when congestion is detected, the rate indication value is decreased by a predetermined value. An ABR communication control method, comprising comparing the calculated value with a current transmission rate of the terminal and notifying the terminal of a smaller value as a new transmission permission rate. 2. An ABR communication control method for notifying a terminal of a transmission permission rate, comprising setting a rate indication value corresponding to a route, detecting congestion and non-congestion in a buffer memory, and detecting the congestion and non-congestion in a buffer memory. The rate indication value is increased by a predetermined value, and when congestion is detected, the value obtained by decreasing the rate indication value by a predetermined value is compared with the explicit cell rate value written in the resource management cell, and a smaller value is newly transmitted. An ABR communication control method, comprising a step of notifying the terminal as an allowed rate. 3. A method for detecting congestion and non-congestion in said buffer memory, wherein a congestion state is set to a plurality of levels according to a queue length of a cell and a rate of change of the queue length per unit time. 3. The ABR communication control method according to claim 1, further comprising a step of dividing and performing an operation of calculating the rate instruction value according to each level. 4. An ABR communication control method for notifying a terminal of a transmission permission rate, comprising: calculating an input load of the buffer memory from a ratio between an input rate to the buffer memory and a target use bandwidth of the buffer memory; Calculate the average rate of the connection passing through the buffer memory, and detect the congestion state in the buffer memory, and add a value obtained by increasing or decreasing the average rate according to the congestion state and the input load to a new value. An ABR communication control method comprising a step of notifying the terminal as a transmission permission rate. 5. An ABR communication control device for notifying a terminal of a transmission permission rate, comprising: a congestion detection control unit for detecting presence / absence of congestion in a buffer memory; and an indication for notifying the terminal of the transmission permission rate. A static cell rate write control unit, and a transmission permission rate calculation control unit that calculates the transmission permission rate, wherein the transmission permission rate calculation control unit sets a rate instruction set for a route when non-congestion is detected by the congestion detection unit. A parameter storage unit storing an increase rate for a value and a decrease rate for the rate instruction value when congestion is detected, and a value obtained by increasing the rate instruction value by an increase rate read from the parameter storage unit when the non-congestion is detected, and the terminal The larger value compared to the current transmission rate is used as the new transmission permission rate, and when congestion is detected, A value obtained by reducing the rate indication value by the reduced rate read from the storage unit and the current transmission rate of the terminal are compared, and a smaller value is added to the explicit cell rate write control unit as a new transmission permission rate. An ABR communication control device, comprising: a transmission permission rate calculation unit. 6. An ABR communication control device for notifying a terminal of a transmission permission rate, comprising: a congestion detection control unit for detecting the presence or absence of congestion in a buffer memory; and an indication for notifying the terminal of a transmission permission rate. A static cell rate write control unit, and a transmission permission rate calculation control unit that calculates the transmission permission rate, wherein the transmission permission rate calculation control unit sets a rate instruction set for a route when non-congestion is detected by the congestion detection unit. A parameter storage unit storing an increase rate for a value and a decrease rate for the rate instruction value at the time of congestion detection, and increasing the rate instruction value by an increase rate read from the parameter storage unit at the time of non-congestion detection, at the time of congestion detection,
The value obtained by reducing the rate indication value by the reduced rate read from the parameter storage unit is compared with the explicit cell rate value written in the resource management cell from the terminal. An ABR communication control device, comprising: a transmission permission rate calculation unit added to the explicit cell rate write control unit as a rate. 7. The transmission permission rate calculation control unit divides a congestion state into a plurality of levels according to a queue length of a cell and a rate of change of the queue length per unit time. A parameter storage unit that stores a calculation operation of the rate instruction value for each, and a transmission permission rate calculation unit that calculates a rate instruction value by a calculation operation according to the level of the congestion state read from the parameter storage unit. The ABR communication control device according to claim 5 or 6, wherein 8. An ABR communication control device for notifying a terminal of a transmission permission rate, a congestion detection control unit detecting a congestion state in a buffer memory, and a transmission permission for notifying the terminal of a transmission permission rate. A rate writing control unit; and a transmission permission rate calculation control unit that calculates the transmission permission rate. The transmission permission rate calculation control unit includes a parameter storage unit that stores parameters corresponding to a route and corresponding to congestion and non-congestion. ,
An input load calculator for calculating an input load of the buffer memory from a ratio of an input rate to the buffer memory for a predetermined period and a target use bandwidth of the buffer memory, and an average rate calculator for calculating an average rate of connections passing through the buffer memory With the input load of the buffer memory by the input load calculation unit, the average rate by the average rate calculation unit and the congestion status detection signal by the congestion detection control unit,
An ABR communication control device, comprising: a transmission permission rate calculation unit that calculates a new transmission permission rate. 9. The average rate calculation unit that calculates an average rate of connections passing through a buffer memory selects a connection to be subjected to an average rate calculation in accordance with a congestion state detection signal from the congestion detection control unit and averages the connections. 9. The apparatus according to claim 8, further comprising a configuration for calculating a rate.
The ABR communication control device according to claim 1. 10. The input load calculation unit sets a plurality of target use bands in the parameter storage unit as the target use bands according to a congestion state detection signal from the congestion detection control unit, and sets each target use band to The ABR communication control device according to claim 8, further comprising a configuration for calculating an input load. 11. The transmission allowed rate calculating section calculates a value obtained by dividing the average rate calculated by the average rate calculating section by the input load calculated by the input load calculating section as a transmission allowed rate. The ABR communication control device according to claim 8, comprising: 12. When the congestion status detection signal from the congestion detection control unit indicates a congestion state, the transmission allowed rate calculation unit calculates the average rate calculated by the average rate calculation unit and the average rate based on the input load. 9. The ABR communication control device according to claim 8, wherein a configuration is provided in which a value divided by the input load calculated by the calculation unit is compared, and the smaller value is used as a transmission permission rate.