JP2003023455A - Rate controller - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a rate controller that is installed in a communication network and impartially distributes an extra band between connections in a normal state (in a non-congested state) while warranting a minimum contracted band, even in a congestion state for each connection established in the communication network so as to more efficiently utilize a network resource, economically realizes efficient utilization, even in a high-speed channel, and is installed in a node so as to realize a simple hardware configuration, thereby realizing congestion avoidance in a node, with high efficiency. SOLUTION: The rate controller is provided with a means of discriminating reception propriety, on the basis of a permissible arrival rate ACRi calculated by each period for a prescribed period, where the phase of the prescribed period is set differently for different connections.

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for guaranteeing the minimum bandwidth of each connection accommodated in a communication network.
The present invention provides an ATM (Asy) for handling cells that are fixed-length packets.
nchronous Transfer Mode) Used for communication networks. 2. Description of the Related Art In recent years, data traffic such as IP traffic has been increasing exponentially due to the rapid spread of the Internet and LANs. As a result, the frequency of occurrence of congestion on the network is increasing, and the quality of service for users is becoming a problem. For example, the best-effort service that does not guarantee the transfer quality was the mainstream in the conventional Internet, but the case where the best-effort service alone cannot provide sufficient throughput is increasing, and the ISP (Internet Service Provider) and the company In the case of connecting with high-speed lines, demand for services that guarantee the minimum bandwidth and delay quality for each line is expected to increase more and more in the future. There is a GFR (Guaranteed Frame Rate) service as a service that guarantees the minimum bandwidth contracted for each user. At the time of non-congestion, each user can share and use the available bandwidth (remaining bandwidth). [0004] Many proposals have been made for a system for realizing the GFR service, one of which is WRR (Wei).
ghted Round Robin) method. FIG. 14 is a diagram schematically illustrating the WRR method. The WRR method has a queue for each connection and is weighted for each connection.
By performing read control according to the weight for each queue, the bandwidth is distributed between the connections. [0005] By accommodating all the connections sharing the band in the WRR, the band can be distributed according to the weight of the accommodated connection. With the WRR scheme, it is possible to distribute the surplus bandwidth fairly among the connections according to a certain rule while guaranteeing the minimum bandwidth. However, the complexity of the hardware of the WRR system is proportional to the number of connections to be accommodated, and becomes a bottleneck for speeding up. Also, since it is necessary to have a queue for each connection, the amount of hardware in the buffer unit also becomes a problem. In other words, when the WRR system is operated at high speed and the number of accommodated connections increases, it is difficult to economically realize the GFR service. Therefore, there is a demand for a method for realizing the GFR service with a simple hardware configuration. As a method for realizing the GFR service with a simple hardware configuration, a FIFO-Tagging method is known. In this method, it is not necessary to have a buffer for each connection, but it is sufficient to have one buffer for each line. FI
In the FO-Tagging method, the input rate to the network is observed at the entrance of the network for each connection, and if the measured rate is equal to or less than MCR (Minimum Cell Rate), the cell of the connection passes as it is and exceeds the MCR. Then, Tag is added to the header of the cell. Where MCR
A band is a band for which the network guarantees transfer for a connection. [0008] A threshold value is provided in the FIFO buffer, and whether or not the queue length exceeds the threshold value is constantly monitored. If the queue length exceeds the set threshold value, the cell with the tag in the header is FIFO
Discarded before entering buffer, T
cell without ag, that is, the input rate to the network is M
Only cells with connections below CR are passed. [0009] In the FIFO-Tagging method, the FI
MC of the connection that accommodates the output speed of the FO buffer
By making the total R or more, it is possible to guarantee the MCR at the time of congestion. Also, when there is no congestion, M
If there is a portion of the band exceeding the sum of the CRs and a surplus band, the band is shared by a plurality of connections. [0010] However, in this method, a buffer is shared by a plurality of connections. Therefore, the bandwidth of the portion exceeding the sum of the MCRs of each connection and the surplus bandwidth are not changed by the input rate to the FIFO buffer. Is distributed between each connection in proportion to
There was a problem in that. In the FIFO-Tagging method, when there is a surplus bandwidth, there is no regulation on how to distribute the bandwidth among the connections, and in an extreme case, an unfair situation in which one connection occupies the surplus bandwidth. There was a problem that occurs. [0011] The present invention has been made in such a background, and by installing it in a communication network, each connection accommodated in the communication network has a minimum contracted contract even at the time of congestion. In normal times (when there is no congestion), surplus bandwidth is distributed fairly among connections while guaranteeing bandwidth,
It is an object of the present invention to provide a rate control device which can enable more efficient use of network resources and can be economically realized even on a high-speed line. Further, it is another object of the present invention to provide a rate control device which can realize a simple hardware configuration by being installed in a node such as a cell switching switch or the like and which can realize efficient congestion avoidance in the node. According to the present invention, a connection 1 to k to which an arriving cell belongs is identified, and a connection i
Means for detecting a cell arrival rate Ri for each (i is any of 1 to k), setting a permitted arrival rate ACRi of the cell according to the detection result,
Means for determining whether or not to accept an arrival cell based on Ri. Here, it is a feature of the present invention that the determining means includes means for determining acceptability based on the permissible arrival rate ACRi calculated for each predetermined period, and the predetermined period is determined. Is set so that the phase is different for each different connection. [0014] Thus, the congestion control is not performed or released for all the connections at the same time, and stable control can be performed. According to this, by installing in the communication network, each connection accommodated in the communication network is
While guaranteeing the minimum bandwidth contracted even during congestion,
In normal times (when there is no congestion), the surplus bandwidth can be distributed fairly among connections, enabling more efficient use of network resources, and at a rate economically feasible even on high-speed lines. A control device can be realized. further,
By installing in a node such as a cell exchange switch,
A simple hardware configuration can be realized, and efficient congestion avoidance in a node can be realized. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A multiplexing apparatus to which an allowed arrival rate calculation section and a reception judgment section as a rate control apparatus according to the present invention will be described with reference to FIG. FIG. 1 is a block diagram of a multiplexing apparatus according to an embodiment of the present invention. As shown in FIG. 1, the multiplexing apparatus includes a connection 1 to a cell to which an arriving fixed length packet belongs.
k, a connection determination unit 5 for determining whether or not the cell can be received, a FIFO buffer 6 for temporarily storing cells according to the determination result of the reception determination unit 5, and a connection for each connection i. Cell arrival rate Ri
And a connection information storage unit 2 that holds a value of a predetermined weight Wi for each connection i, and a maximum rate serving as a threshold is set in advance for the cell arrival rate Ri, The arrival rate Ri of the cell which becomes almost zero when the maximum rate is exceeded.
The continuous function of the sum ΣRi is β (ΣRi), the sum of the weights of the connections i in which one or more cells are stored in the buffer 6 of the buffer unit 11 is Wact, and the permitted arrival rate calculation unit 4 The rate ACRi is calculated as ACRi = β (ΣRi) · Wi / Wact, and the reception determining unit 5 permits the cell belonging to the connection where the arrival rate Ri of the cell for each connection i is equal to or lower than the permissible arrival rate ACRi. Is determined. In this embodiment, when a plurality of connections are mixed and accumulated in one buffer 6, the queue length monitoring unit 7 and the virtual queue management unit 3 use the connection i for the actual queue length of the buffer 6. Each time the queue length Xi of the buffer 6 is detected is referred to as a virtual queue length. FIG. 13 is a configuration diagram of a network that provides a minimum bandwidth guarantee service by applying the present invention. The calling user sends out the cell to the called user through the network. The network guarantees the transfer rate up to the contracted minimum bandwidth for the user. Each link of the network accommodates a plurality of users, and the surplus bandwidth is distributed among the users according to a weight determined based on a fee, a minimum guaranteed bandwidth, and the like. As described above, the multiplexing device provided with the rate control device of the present invention is provided in a network as shown in FIG.
rameter Control). Also,
By providing it in the cell exchange switch, it can also be used to avoid congestion of buffers in the switch. First, when the originating user sends a cell to the network, the rate observing device located at the ingress edge of the network measures the cell sending rate to the user's network. If the cell transmission rate exceeds the minimum guaranteed bandwidth, a tag is added to the cell header, and cells transmitted below the minimum guaranteed bandwidth are transmitted to the network as they are. The minimum bandwidth is assured by transferring cells without tags to the destination user without discarding them in the network. The multiplexing apparatus of the present invention is located in a relay node and performs processing of distributing a link band shared by a plurality of users to each user according to weight. As shown in FIG. 1, the multiplexing apparatus according to the present invention comprises a connection identifying unit 1, a band control unit 10, and a buffer unit 11. The connection identification unit 1 identifies a connection from the header of the arriving cell. The band control unit 10 performs a process related to band control based on the connection information. The buffer unit 11 is a simple FI
The FO type buffer 6 is shared by all users accommodated in the link. The buffer 6 is connected to a queue length monitoring unit 7, which transmits information on the queue length of the buffer 6 and input / output cells at the time of cell input / output to the virtual queue management unit 3 at the preceding stage. Here, the information regarding the input / output cells includes the cell length of the cell input to or output from the buffer 6 and the identification number of the connection to which the cell belongs. Since the cell length is constant, the input / output information of the cell with respect to the buffer 6 can be simply included without including the cell length information. When a cell arrives from the input line side, the connection identification unit 1 identifies the connection of the cell, is sent to the subsequent band control unit 10, determines whether or not to input to the buffer 6, and determines whether to discard the cell. The determined cell is discarded on the spot, and the cell not determined to be discarded is input to the buffer unit 11 at the subsequent stage and output to the output line according to the FIFO standard. In the present invention, band control based on cell discard in band controller 10 plays an important role. Therefore, the processing of the band control unit 10 will be described in detail. The bandwidth control unit 10 includes a rate detection unit 8, a virtual queue management unit 3, an allowed arrival rate calculation unit 4, a connection information storage unit 2, and an acceptance determination unit 5. The virtual queue manager 3 calculates the queue length of the buffer 6 and the queue length of each connection based on the information from the queue length monitor 7. The virtual queue management unit 3 is connected to the connection information storage unit 2, and the calculated virtual queue length for each connection is recorded in the connection information storage unit 2. A method for calculating each queue length will be described.
First, regarding the calculation of the queue length of the buffer 6, the queue length information transmitted from the queue length monitoring unit 7 is simply stored in the virtual queue management unit 3 as it is. Next, a method of calculating the virtual queue length for each connection is as follows. Since the buffer 6 is empty in the initial state, the virtual queue length of each connection is zero. When a cell is input to the buffer 6,
The cell length of the cell and the connection identification number are transmitted through the queue length monitoring unit 7. Based on the information, the virtual queue management unit 3 accesses the connection identification unit 1 and performs a process of adding the transmitted cell length to the virtual queue length of the connection. On the other hand, at the time of cell output, processing is performed to subtract the transmitted cell length from the virtual queue length. Note that, since the cell length is constant, the queue length monitoring unit 7 does not transmit the cell length when a cell is input / output to / from the buffer 6 but simply informs that the cell has been input / output to / from the buffer 6. May be transmitted. FIG. 2 shows an example of the connection information storage unit 2 in which information on the virtual queue length for each connection calculated by the virtual queue management unit 3 and information on the weight of the connection are stored. Next, the permitted arrival rate calculation unit 4 receives information on the cell arrival rate Ri and information on the virtual queue length and weight for each connection from the rate detection unit 8 and the connection information storage unit 2, and also receives them. And a function for calculating the permitted arrival rate ACRi. Here, the permitted arrival rate ACRi of the connection i indicates the maximum arrival rate at which cell arrival is permitted. Permitted arrival rate ACRi for connection i
The calculation method of is specifically described. Assuming that the weight of the connection is Wi and the current arrival rate is ΣRi, ACRi = β (ΣRi) · Wi / Wact. β (ΣRi) is a continuous function, and the graphs of FIGS. 3 to 9 show functions β (ΣRi) of the arrival rate Ri.
This is an example. The horizontal axis indicates the arrival rate ΣRi, and the vertical axis indicates the value of the function β (ΣRi). Wact is the sum of the weights of active connections. Here, the active connection is a connection in which the virtual queue length is larger than zero, that is, a connection in which at least one cell is in the buffer 6. The function β (ΣRi) becomes zero when the arrival rate Ri exceeds a certain threshold value (Rmax in the figure). That is, when the arrival rate Ri exceeds a certain threshold, it is determined that congestion has occurred, and the permitted arrival rate ACR of each connection is determined.
i becomes zero. For example, in the example of FIG. 3, the function β (ΣRi) takes a constant value in a range not exceeding the threshold value Rmax, and becomes zero when the threshold value Rmax is exceeded. That is, the permitted arrival rate ACRi is distributed in proportion to the connection weight within a range not exceeding the threshold value Rmax. In the example of FIG. 4, the function β (ΣRi) decreases gradually from the arrival rate Ri to zero to a predetermined value less than the threshold value Rmax, and decreases rapidly as the arrival rate Ri approaches the threshold value Rmax. , The threshold value Rmax is zero.
That is, when the arrival rate Ri is small, the permitted arrival rate ACRi is distributed to the weight of the connection i or more, but when the arrival rate Ri exceeds a predetermined value, the distribution rate of the permitted arrival rate ACRi decreases sharply. In the example of FIG. 5, the arrival rate Ri and the function β
The value of (ΣRi) is inversely proportional to linear. That is, the allowed arrival rate ACRi is linearly inversely proportional to the arrival rate Ri. This is the simplest and basic control example. In the example of FIG. 6, the arrival rate Ri and the function β
The value of (ΣRi) is inversely proportional to the quadratic function.
In other words, the permitted arrival rate ACRi is large when the arrival rate Ri is low, but suddenly starts decreasing as the arrival rate Ri increases, and the arrival rate Ri becomes equal to the threshold Rmax.
Decreases gradually as it approaches. As a result, it is possible to strongly suppress an increase in traffic when the arrival rate Ri starts to increase. In the example of FIG. 7, the arrival rate Ri and the function β
The value of (ΣRi) is inversely proportional to the quadratic function inverted from the quadratic function shown in FIG. In other words, the permitted arrival rate ACRi is large when the arrival rate Ri is low, but gradually starts decreasing as the arrival rate Ri increases, and decreases rapidly as the arrival rate Ri approaches the threshold value Rmax. Thereby, the arrival rate Ri becomes equal to the threshold value Rm.
As the distance approaches ax, an increase in traffic can be strongly suppressed. In the example of FIG. 8, the arrival rate Ri and the function β
The value of (ΣRi) is inversely proportional to the stepwise. That is, the permitted arrival rate ACRi is large when the arrival rate Ri is small, but starts to decrease gradually as the arrival rate Ri increases, starts to decrease suddenly from a predetermined arrival rate Ri, and decreases again as the arrival rate Ri approaches the threshold value Rmax. Becomes gradual. This makes it possible to strongly suppress an increase in traffic when the arrival rate Ri is near the middle point between zero and the threshold value Rmax. In the example of FIG. 9, the arrival rate Ri and the function β
The value of (ΣRi) is inversely proportional to the example of FIG. That is, the permitted arrival rate ACRi is large when the arrival rate Ri is low, but starts to decrease rapidly as the arrival rate Ri increases, starts to decrease gradually from a predetermined arrival rate Ri, and suddenly decreases as the arrival rate Ri approaches the threshold value Rmax. Begins to decrease. This makes it possible to strongly suppress an increase in traffic between the time when the arrival rate Ri starts increasing from zero and the time when the arrival rate Ri approaches the threshold value Rmax. Although the present arrival rate (instantaneous value) is used as the arrival rate Ri, the arrival rate R
The average value of the arrival rate within a certain time may be adopted as i. The reception determining unit 5 determines whether cells arriving from the permitted arrival rate ACRi and the arrival rate Ri for each connection are input to the buffer 6 or discarded. FIG.
Is a flowchart showing a processing flow upon arrival of a cell in which a definite discarding process is performed. As shown in FIG. 10, if the arrival rate Ri is equal to or lower than the permitted arrival rate ACRi, it is input to the buffer 6 and the permitted arrival rate ACRi Is exceeded, the cells with the tag are discarded, and the cells without the tag are input to the buffer 6, so that the minimum bandwidth of each connection is always guaranteed, and the occupancy of the buffer 6 is reduced. Control to be fair. The arrival rate Ri is equal to the permitted arrival rate A.
When CRi is exceeded, it is also possible to stochastically discard cells instead of deterministically discarding cells as described above. FIG. 11 is a flowchart showing a processing flow at the time of arrival of a cell in which a stochastic discard process is performed. As shown in FIG. 11, the permitted arrival rate ACRi and the arrival rate are set to R.
If i, the discard probability P is given by P = (Ri−ACRi) / Ri. In other words, when the arrival rate Ri exceeds the permitted arrival rate ACRi, the rate is reduced by the excess rate. By controlling the bandwidth by stochastic discarding, when attention is paid to one connection, even when the arrival rate Ri exceeds the permitted arrival rate ACRi, the phenomenon that cells are continuously discarded is definitely determined. Since it is smaller than the case of discarding, it can be said that the affinity with TCP rate control becomes higher. The cells input to the buffer 6 are output to an output line according to a FIFO standard. The generation of the pseudo random number Rand in FIG. 11 is performed every time a cell arrives, and the discard probability P and the pseudo random number Ran are generated.
By executing the discard based on the result of comparison with d, it is possible to actually realize the discard with the discard probability P. For example, when the discard probability P is 0.5, the probability that the pseudo-random number Rand takes a value larger than 0.5 is also 0.5, and when the pseudo-random number Rand is larger than 0.5, discarding is performed. By executing, the discard is performed according to the discard probability P. The multiplexing device of the present invention estimates the congestion state of the network based on the arrival rate Ri, and when it is determined that the network is congested, the allowed arrival rate ACRi becomes equal to zero, and the rate is lower than the minimum guaranteed bandwidth. The network transfers only cells that have been sent to the network. When the arrival rate Ri is equal to or less than a certain threshold, it is determined that there is a surplus bandwidth, and each connection can distribute the bandwidth fairly among the connections according to the permitted arrival rate ACRi proportional to the weight. Further, according to the above-described embodiment, the GFR service is realized by the FIFO buffer having a simple hardware configuration, and the cell read control is performed by individually holding the buffer for each connection such as the WRR system. As with the method, it is possible to distribute the surplus bandwidth fairly among the connections. Further, since one buffer is shared by many connections, there is an advantage that the required buffer amount can be reduced due to the statistical multiplexing effect as compared with a system having a buffer for each connection. As a function of the reception judging unit 5, when the cell of the connection j to be judged as rejection does not exist in the buffer 6, the cell to be judged as rejection is judged to be admitted. That is, the absence of the cell of the connection j in the buffer 6 indicates that the cell of the connection j is sporadic. Even if such sporadic cells are rejected and discarded, the effect of avoiding congestion is extremely low compared to the case where continuous cells are discarded. Therefore, such sporadic cells should not be discarded in a meaningless manner. As a function of the rate detecting section 8, the arrival rate Ri is detected for a change cycle shorter than a predetermined change cycle of the arrival rate Ri. Thus, the instantaneous arrival rate R
By absorbing the change in i, it is possible to avoid a malfunction of the traffic control due to a disturbance. Further, the detection timing can be set sparsely such that the detection of the arrival rate Ri is divided for each unit time, and every other or every two unit time intervals. This makes it possible to output a detection result of the gradual arrival rate Ri. Alternatively, as a function of the rate detection unit 8,
The maximum value of the arrival rate Ri within the unit time is calculated as the arrival rate Ri.
Is output for each unit time as a detection result. As a result, the instantaneous change in the arrival rate Ri can be absorbed, and malfunction of the traffic control due to disturbance can be avoided. The detection timing can be set sparsely such that the detection of the arrival rate Ri is divided every unit time, and every other or every two unit time divisions. This makes it possible to output a detection result of the gradual arrival rate Ri. The reception determining unit 5 as a feature of the rate control device of the present invention makes a reception determination based on the permitted arrival rate ACRi calculated for each predetermined period, and the predetermined period is as shown in FIG. As shown, the phase is set to be different for each different connection. As a result, the congestion control is not performed or released for all connections at the same time, and stable control can be performed. As described above, according to the present invention,
By installing in the communication network, the minimum bandwidth contracted for each connection accommodated in the communication network is guaranteed even during congestion, and the surplus bandwidth is connected during normal times (when there is no congestion). Fair distribution among the network resources, enabling more efficient use of network resources. Further, it is possible to realize a rate control device that can be economically realized even on a high-speed line. Furthermore, by installing the switch in a node such as a cell switching switch, a simple hardware configuration can be realized, and congestion in the node can be efficiently avoided.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram of a multiplexer according to an embodiment of the present invention. FIG. 2 is a diagram showing a table example of a connection information storage unit. FIG. 3 is a diagram showing an example of a function β (ΣRi). FIG. 4 is a diagram showing an example of a function β (ΣRi). FIG. 5 is a diagram showing an example of a function β (ΣRi). FIG. 6 is a diagram showing an example of a function β (ΣRi). FIG. 7 is a diagram showing an example of a function β (ΣRi). FIG. 8 is a diagram showing an example of a function β (ΣRi). FIG. 9 is a diagram showing an example of a function β (ΣRi). FIG. 10 is a flowchart showing a processing flow at the time of arrival of a cell for performing a definite discarding process. FIG. 11 is a flowchart showing a processing flow upon arrival of a cell in which a stochastic discard process is performed. FIG. 12 is a diagram for explaining a band control method according to the present invention. FIG. 13 is a diagram showing an example of a network configuration to which the present invention has been applied. FIG. 14 is a view for explaining an outline of a conventional WRR system. [Description of Signs] 1 Connection identification unit 2 Connection information storage unit 3 Virtual queue management unit 4 Permitted arrival rate calculation unit 5 Acceptance judgment unit 6 Buffer 7 Queue length monitoring unit 8 Rate detection unit 10 Band control unit 11 Buffer unit

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Claims (1)

Claims: 1. A connection 1 to which an arriving cell belongs.
k, and connection i (i is any of 1 to k)
A rate control comprising means for detecting a cell arrival rate Ri every time and setting a permitted arrival rate ACRi of the cell according to the detection result, and means for determining whether or not to accept an arrival cell based on the permitted arrival rate ACRi In the apparatus, the means for determining comprises: an allowed arrival rate AC calculated for each predetermined cycle for each cycle.
A rate control device comprising means for determining acceptability based on Ri, wherein the predetermined cycle is set so that the phase is different for each different connection.