JPH0951341A - Communication equipment and communication network performing control of path capacity - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a communication equipment and a communication network which reduce the frequency of change of path capacity and improve the use efficiency of a transmission line. SOLUTION: In the communication equipment executing communication with plural opposite devices, different values are used for a threshold parameter used for judging whether the capacity of a path 14 is to be changed or not and a parameter for deciding the change quantity of capacity. Furthermore, a control parameter is adaptively controlled based on the idle capacity of the transmission line and congestion information. Thus, capacity change frequency is reduced and the capacity change load of a controller is reduced.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a communication device and a communication network for controlling a path capacity, and more particularly to a path capacity control capable of reducing a capacity change processing load and efficiently using a transmission line in a digital switching network. The present invention relates to a communication device and a communication network to perform.

[0002]

2. Description of the Related Art Conventionally, in a digital switching network such as an ATM switching network, a plurality of exchanges are connected by a transmission line and a cross-connect device, and a desired amount of communication capacity of the transmission line is virtualized between specific exchanges. Transmission line (virtual path = V
P). Furthermore, VP capacity change control has been performed to increase or decrease the capacity of the VP in response to the increase or decrease in the required communication volume. For example, IEICE Transactions 1
The July 1993 issue, pages 465-473, discloses a VP capacity control method for adaptively controlling the capacity change step width according to traffic.

[0003]

As described above, in the conventional communication capacity allocation control method, when the VP free space runs out, the capacity is added by the capacity change step width, and the VP free space is changed by the capacity change step. When the width exceeds the width, the capacity was reduced by the capacity change step width.
When the actual usage amount (connection capacity) repeatedly increases and decreases in the vicinity of the change threshold, the communication capacity changing process frequently occurs, and the capacity changing process load increases. An object of the present invention is to provide a communication device and a communication network that solve the above-mentioned problems of the prior art, reduce the frequency of changing the path capacity, and improve the use efficiency of the transmission path.

[0004]

SUMMARY OF THE INVENTION According to the present invention, in a communication device that communicates with a plurality of partner devices, a threshold parameter used for determining whether or not to change the capacity of a path and the amount of change in capacity are determined. It is characterized in that different values are used for the parameters for performing. According to the present invention, different values are used for the threshold parameter used for determining whether to change the capacity of a path and the parameter for determining the amount of change in capacity. It is also possible to change the capacity so as to be in the middle of the upper and lower change thresholds, and it is possible to prevent the capacity changing process from occurring frequently even if the communication amount fluctuates oscillatingly. Further, since the threshold value and the change amount can be individually controlled according to the communication amount of the entire transmission line and the call occurrence state, it is possible to further reduce the frequency of capacity change and improve the utilization factor of the transmission line.

[0005]

DETAILED DESCRIPTION OF THE INVENTION The present invention will be described in detail below with reference to the drawings. FIG. 1 is a block diagram showing a communication network to which the present invention is applied. Communication terminals 1, 2, 8, 9, 12, 13 such as telephones, facsimiles, computers, etc. are respectively housed in ATM exchanges 3, 7, 11 to which the present invention is applied. The ATM exchange A3 is connected to the cross-connect device 5 by the transmission line 4, and the ATM exchange B7 is connected to the cross-connect device 5 by the transmission line 6. The cross-connect device 5 can connect between accommodated arbitrary transmission paths. VPs 14, 15 and 16 are virtual transmission lines set on physical transmission lines,
For example, the VP 14 logically connects the ATM exchange A3 and the ATM exchange B7.

FIG. 2 is a block diagram showing the structure and function of an ATM exchange to which the present invention is applied. The line terminators 20 and 22 interface with the lines and transmission lines from the terminals, respectively, and send and receive connection control signals. The ATM switch 21 is an ATM between line termination devices.
It consists of an ATM switch circuit that exchanges cells. Various types of proposed switches can be used as the switch circuit. The control unit 23 controls the entire exchange 3, and includes, for example, a CPU, a memory, an external storage device, a bus, and the like. The connection control unit 24, which is a functional block in the control unit 23, exchanges connection control information with the terminal and the transmission path, and if the VP of the target route has a vacancy, the terminal, the transmission path, and the other terminal. A virtual connection path (VC) between them is formed. Note that, for example, a transmittable bandwidth (communication capacity) designated by the connection control information during or during connection is assigned to each VC in advance.

The path capacity table 25 stores the communication capacity CP currently assigned to each VP, as shown in FIG. 4 (a). Control parameter table 2
7 shows each V as shown in FIG. 4B, which shows the contents of the control parameter table 27 in the first embodiment.
A capacity addition (upper) threshold TI, a capacity reduction (lower) threshold TD, a capacity addition margin MI, and a capacity reduction margin MD, which are parameters used for path capacity control, are stored for each P, and these values are set as parameters. It can be changed from the part 28. The path capacity control unit 26 constantly monitors the current usage amount, performs capacity change processing by a method described below to update the path capacity CP, and issues a path capacity change request to the connection control unit 24. .

FIG. 3 is an explanatory diagram for explaining the concept of VP and VC in the transmission path. The transmission line is actually a time division multiplex transmission line such as a plurality of optical fibers. Then, of the total transmission capacity, for example, the capacity CP1 is VP.
Assigned to 1. If a plurality of virtual connection paths VC currently in communication are logically present in VP1 and the total communication capacity is U1, VP1 still has an empty space E1 =
CP1-U1 is logically present. It should be noted that there is an empty E0 that has not been assigned to any VP yet on the transmission path.

FIG. 5 is a flow chart showing a first embodiment of the path capacity control processing in the path capacity control section 23. In step S1, the usage amount U for each VP
Is determined, and if the result is affirmative, the process proceeds to step S2. Note that the path capacity change control method is a method (sequential change type) in which the capacity change process is activated when the connection state of a call changes, that is, when a call arrives or ends.
There is a method (periodic change type) in which the capacity changing process is activated periodically by a timer or the like provided in the control device, and in the case of the sequential changing type, this step S1 is unnecessary. In step S2, the VP relating to the changed VP
The free space E = CP-U is calculated. In step S3, it is determined whether E is smaller than the capacity addition threshold value TI, and if the result is affirmative, the process proceeds to step S4. The threshold and margin are based on CP as shown in FIG. After step S4, since the usage amount U exceeds the capacity addition threshold value TI, capacity addition processing is performed. In step S4, the change amount Di of the allocated capacity is obtained. The old CP is the old CP = U + E, and the new CP after the change is changed to the new CP = U + MI if there is a free space, so the change amount Di is Di = new C.
P-old CP = MI-E.

In step S5, the free capacity E0 on the transmission path is obtained. For example, in the case of the VP 14 shown in FIG. 1, since it passes through the transmission lines 4 and 6, it is necessary to check the free capacity in both transmission lines. Therefore, the exchange A4
A free space search request is transmitted to the cross-connect device 5 or the exchange B7. The free space search request is sequentially processed by each device on the VP, and finally the minimum value of the free space on each transmission path through which the VP passes is notified to the path capacity control unit 26.

In step S6, it is determined whether E0 is greater than or equal to Di, that is, whether or not there is a space for the addition request (Di). If the result is negative, the process proceeds to step S8, but if the result is affirmative, step S8 is performed.
Move to 7. In step S7, the VP capacity CP
Is increased by Di. Specifically, the path capacity control unit 26
Changes the path capacity in the path capacity table 25 and issues a capacity increase request for the path to the connection control unit 24. The connection control unit 24 changes the allocated capacity of the VP based on the request. Note that the connection control unit 24, for example, if there is a vacant VP for the route for a new call,
A new VC is set inside to connect the call, but if there is no free space, a bypass route is selected or the connection is rejected.

When there is no required amount of free space in step S6, the process proceeds to step S8, and it is determined whether the free space E0 is larger than 0, that is, whether or not there is a free space. Then, when there is no free space, the processing is ended, but when there is free space, the process proceeds to step S9, and the entire free space is added to the capacity of the path. In step S10, it is determined whether or not the free space E of the VP is larger than the capacity reduction threshold value TD, and if the result is affirmative, the process proceeds to step S11.
In step S11, the change amount Dd of the assigned capacity
Ask for. Old CP = U + E, new CP after change is
Since it is changed so that the new CP = U + MD, Dd
Becomes Dd = new CP-old CP = MD-E. In step S12, the VP capacity is reduced by Dd.

In addition, in the method of procuring an additional capacity, when there is not enough free space in the common spare capacity that does not belong to any VP, the allocated capacity of another VP having a relatively large margin can be obtained. There is also a method of performing capacity procurement processing, and in this case, capacity procurement processing is performed in step S5. In this case, a capacity division method in which the capacity reduction processing in steps S10 to S12 in FIG. 5 is omitted (or the capacity reduction threshold is decreased to 0) is also conceivable. In the case of this capacity division method,
Initially, the allocated capacity of each VP only increases, so the free capacity that does not belong to any VP becomes zero. After that, if there is insufficient free space in any VP,
In step S5 of FIG. 5, another V with a relatively large margin is provided.
A capacity procurement process is performed to secure a free capacity by reducing the allocated capacity of P. Therefore, if there is a margin in the capacity of the transmission path, the frequency of capacity change will decrease, but at the time of capacity change, it is necessary to investigate all the free capacity of other VPs, and the processing load becomes heavy.

FIG. 6A is an explanatory diagram showing an example of the change of the allocated capacity CP with the change of the usage amount U in the first embodiment. When the usage amount U, which was between the additional threshold value and the reduction threshold value at the time t0, exceeds the additional threshold line (the CP-TI line on the upper side of the shaded portion) at the time t1, the capacity adding process (step S4 in FIG. 5) is performed. After that, CP is increased by Di so that the difference between the new CP and U at that time is MI. Actually, there is a slight delay in the capacity addition process from the increase in the usage amount U to the increase in the capacity CP, and the free capacity remains E during that time.

At time t2, the capacity is added again, and when U falls below the reduction threshold line (the CP-TD line below the dotted portion) at time t3, the capacity reduction processing is executed. CP is reduced by Dd so that the difference between the new CP and U at that time is MD. Capacity addition margin MI and capacity reduction margin MD are TI and TD
Within the range, each can be independently set to an arbitrary value, and the frequency of capacity change processing can be reduced or the free capacity in the VP can be reduced to enable the transmission line depending on how each parameter is set. Can be used for.

In the first embodiment, the following modifications can be considered. First, the capacity addition margin MI and the capacity reduction margin MD may be equal, and in this case, 1
Only one margin parameter needs to be stored. Further, MI may be larger than MD, and in this case, the change width of the capacity becomes large, so that the change processing frequency for a change with a long cycle is reduced.

In the capacity change processing, it is necessary to search and confirm the free capacity when adding the capacity, but when the capacity is reduced, it is sufficient to simply notify the capacity reduction. Therefore, the capacity reduction margin MD may be deleted and the CP may be changed during the capacity reduction processing so that the new capacity CP = U + TD. In this case, the frequency of the capacity reduction process is higher than that in the first embodiment.

Next, the second embodiment will be described.
In the first embodiment, the threshold value and the margin are used as parameters, but in the second embodiment, the change amount is calculated from the threshold value and the used amount and used. FIG. 4C is an explanatory diagram showing the contents of the control parameter table 27 in the second embodiment. The table stores the capacity addition threshold value TI, the capacity reduction threshold value TD, the capacity addition parameter mi, and the capacity reduction parameter md for each VP. In addition, mi and md are
It is an offset parameter that determines how much the usage U after the capacity change deviates from the intermediate value of the upper and lower thresholds, and both may be 0.

In the second embodiment, the processing of steps S4 and S11 of the processing of FIG. 5 is different from that of the first embodiment. In the second embodiment, when the usage amount U exceeds the threshold value, the change amount Di is obtained by the following calculation in step S4. First, xi, which is the difference between the usage amount U and the capacity addition threshold value TI, is obtained. xi = TI- (old CP-U) Next, the change amount Di is calculated by the following equation. Di = (TD-TI) / 2 + xi + mi That is, Di = U + (TD + TI) / 2 + mi-old CP.

When the usage amount U is below the threshold value, Dd is calculated by the following equation in step S11. xd = (old CP-U) -TD Dd = (TD-TI) / 2 + xd-md That is, Dd = old CP- {U + (TD + TI) /
2} -md. When the change amount is determined in this way, if mi and md are 0, the intermediate value between the upper and lower threshold values after the change matches the use amount U. Therefore, if the change in the use amount U is random, the next capacity is changed. The expected value of the time interval until the change process becomes the maximum.

FIG. 6B is an explanatory diagram showing an example of the change of the allocated capacity CP with the change of the usage amount U in the second embodiment. When the usage amount U that was between the additional threshold value and the reduction threshold value at time t10 exceeds the additional threshold line (shown by the dotted line) at time t11, the capacity adding process is executed, and the CP is increased by the above-mentioned change amount Di. It At time t12, U fell below the reduction threshold line, so
The capacity reduction processing is executed, and the CP is reduced by the above Dd.

As described above, the parameters mi and md are offset parameters for determining how much the usage amount U after the capacity change deviates from the intermediate value of the upper and lower threshold values,
Each takes a value in the range of-(TD-TI) / 2 to (TD-TI) / 2. By controlling this parameter, it is possible to control the ratio of the capacity addition processing frequency and the capacity reduction processing frequency and the free capacity of the path. For example, mi,
When both md have a positive value, the allocated capacity and the threshold value increase by that amount, so the frequency of capacity addition decreases and the frequency of capacity reduction increases. Then, the average free space increases. On the contrary, if mi and md are both negative values, the allocated capacity and the threshold value are decreased accordingly, so that the capacity addition frequency increases and the capacity reduction frequency decreases. Then, the average free space decreases. Therefore, by controlling mi and md, it becomes possible to control the capacity change load to the minimum and to control the free capacity.

The following modified examples can be considered for the second embodiment. The example in which the change amounts Di and Dd are calculated from other measured values and parameters has been disclosed, but Di and Dd may be stored as fixed parameters. Even with this,
If the thresholds can be controlled independently, the effect of reducing the change processing frequency is achieved, and it is not necessary to calculate the change amount.

The function of the expected value of the usage amount may be used to control the amount of change by predicting that the value will return in the direction of the expected value when the value deviates from the expected value. For example, instead of mi, md,
The amount of change may be calculated as follows using the weighting functions Fi (U, Ua) and Fd (U, Ua).
However, Ua is a weighted constant for each path corresponding to the expected value of the current usage amount obtained from the observation result or the like, or the importance degree of the VP.

Di = (TD-TI) / 2 + xi + Fi (U, Ua) Dd = (TD-TI) / 2 + xd-Fd (U, Ua) For example, Fi = Fd = -K (U-Ua), where K Is a constant that determines the control gain, and is determined by simulation, etc. Also,-(TD-TI) / 2≤Fi, Fd≤
It takes a value in the range of (TD-TI) / 2. ), If the current used capacity U is larger than the expected value Ua, the increase amount is decreased, and the reduction amount is increased.
If it is smaller, the opposite is true. Therefore, the capacity change frequency is further reduced.

Next, a modified example common to the first and second embodiments will be described. Each parameter in the first and second embodiments, for example, a threshold value, a margin, an offset parameter, etc., is applied and controlled according to the free capacity of the transmission path through which the VP passes, the overall communication capacity of the exchange, and the congestion or failure condition of the network. Good. For example, when the free space in the transmission path decreases, the upper and lower thresholds or margins are reduced, or the offset parameter is set to a negative value, and the free space in the VP is reduced. The state of the communication network can be obtained from, for example, network condition monitoring devices distributed or centrally arranged in the network.

When a failure or congestion occurs, the unused capacity occupied by each VP can be distributed evenly and the communication capacity can be reduced, or the unused capacity of a path with a low priority can be reduced and specified. The parameters of each VP may be changed in order to maintain the quality of a path having a high priority.

Although the embodiment has been disclosed above, the following modified examples are also conceivable. The capacity of the VC is fixed in advance at the time of contract for each terminal,
It may be determined or changed by exchanging connection control information between the terminal and the network at the time of connection (when making a call) or during connection. The usage amount of the VP may be the sum of the capacities allocated to the VCs currently in communication, or may be the communication amount actually measured for each VP. In this case, the communication volume to be measured is not only the maximum bandwidth (peak cell rate) but also the communication bandwidth in consideration of the statistical multiplexing effect in the path and the temporal variation of the transmission volume, such as the average bandwidth for the immediately preceding one minute. Good.

The parameters such as the threshold value and the margin in the embodiment are so-called free capacity parameters with the allocated capacity CP as a reference. In addition to these, a parameter indicating the communication capacity itself with the reference as 0 is stored. You may In this way, the parameter needs to be updated when the capacity is changed, but the free capacity calculation process in step S2 is unnecessary.

In the embodiment, the distributed control method for controlling the capacity change of the VP for each exchange is disclosed. However, the capacity of each exchange is changed by collecting the usage amount of each VP in one or several places. The processing may be centrally performed by one or several control devices. It should be noted that the present invention is applicable not only to a network using the asynchronous transfer mode, but also to a circuit switching type communication network using other virtual circuits or physical circuits in which a transmission medium is divided into a plurality of paths and operated. It can also be applied when dynamically controlling the capacity. For example,
Examples include controlling the number of lines in a circuit switching network such as a telephone network, controlling the capacity of an SDH transmission path network using a cross-connect device, or controlling the channel capacity of a communication network using a synchronous time division multiplexer (TDM).

[0031]

As described above, according to the present invention,
Call arrival while keeping the average path capacity equivalent to the existing method,
It is possible to suppress the occurrence of the capacity change processing for small fluctuations within a relatively short time due to the end, and to significantly reduce the processing load caused by the capacity change control as compared with the existing method. Further, by selecting the control parameter, it becomes possible to control the ratio of the capacity addition processing and the capacity reduction processing. As a result, since the calculation of the transmission path free space is indispensable in the capacity addition processing, the load on the capacity addition processing is larger than that of the capacity reduction processing. For example, the processing load as a whole can be minimized. Furthermore,
Compared with the existing method, the number of control parameters is increased, the degree of freedom is increased, and more detailed control is possible. Therefore, by changing the control parameters based on changes in network conditions such as failures and congestion, the operation policies of network operators such as maximizing network utilization efficiency and ensuring the quality of specific paths are reflected.
Detailed operation becomes possible.

[Brief description of drawings]

FIG. 1 is a block diagram showing a communication network to which the present invention is applied.

FIG. 2 is a block diagram showing a configuration and functions of an ATM exchange to which the present invention is applied.

FIG. 3 is an explanatory diagram for explaining the concept of a VP and a virtual connection path.

FIG. 4 is an explanatory diagram showing the contents of a control information storage unit.

FIG. 5 is a flowchart showing a first embodiment of a path capacity control process in the path capacity control unit 23.

FIG. 6 is an explanatory diagram showing an example of a change in assigned capacity CP due to a change in usage amount U.

[Explanation of symbols]

1, 2, 8, 9, 12, 13 ... Terminal, 3, 7, 11 ... A
TM switch, 4, 6, 10 ... Transmission line, 5 ... Cross-connect device, 14, 15, 16 ... Virtual path (VP)

Claims (6)

[Claims] 1. In a communication device that communicates with a plurality of partner devices, different values are used for the threshold parameter used to determine whether or not to change the capacity of a path and the parameter for determining the amount of change in capacity. A communication device characterized by being used. 2. In a communication device for communicating with a plurality of partner devices, a storage means for respectively storing at least an upper threshold parameter and an upper margin parameter corresponding to a path set for each partner device, and communication within the path. A detection unit that detects the amount of traffic, a determination unit that determines whether the detected communication amount exceeds the upper threshold value, and a predetermined upper margin is secured when the communication amount exceeds the upper threshold value. And a path capacity changing means for changing the allocated communication capacity for the path. 3. In a communication device for communicating with a plurality of partner devices, a storage means for storing at least an upper threshold value parameter corresponding to a path set for each partner device, and a detection for detecting a communication amount in the path. Means, a determining means for determining whether or not the detected communication amount exceeds the upper threshold value, a calculating means for calculating the change amount based on at least the current assigned communication capacity, the used amount, and the upper threshold parameter, and the communication amount A communication device comprising path capacity changing means for changing the allocated communication capacity for the path by the calculated change amount when the upper threshold is exceeded. 4. The storage means also stores a lower threshold value, and the calculation means calculates the change amount so that the used amount after the capacity change is in the middle of the upper and lower threshold values. Item 3. The communication device according to Item 3. 5. At least one of the parameters is adaptively set in accordance with at least one of a free space of a transmission line, communication amount information in a communication device, information on a usage state of an entire communication network, or failure information. The communication device according to claim 1, wherein the communication device performs control for changing. 6. A communication network including the communication device according to claim 1.