JP5049869B2 - Address allocation capacity control device and program - Google Patents

Description

  The present invention relates to an address allocation capacity control device and a program.

Currently, an IP (Internet Protocol) address allocation service (hereinafter referred to as a DHCP service) by a DHCP (Dynamic Host Configuration Protocol) server is effective in reducing host management load and is essential for a corporate network. DHCP is a protocol that automatically assigns connection information such as an IP address to a host (client) that is temporarily connected to an IP network (see, for example, Non-Patent Document 1).
Also, a VLAN that combines a plurality of widely distributed Ethernet (registered trademark) broadcast segments (hereinafter referred to as LAN (Local Area Network)) into a single virtual LAN (hereinafter referred to as VLAN (Virtual LAN)). With the spread of technology, there is a demand for high reliability of DHCP services in VLANs.

Accordingly, there is a technique in which DHCP servers are made redundant, each DHCP server is assigned a non-overlapping IP address range, and arranged in a VLAN as part of high reliability. Redundancy means that IP addresses in one address space (subnet) can always be assigned without duplication from a plurality of DHCP servers. For example, in the technique described in Non-Patent Document 2, the assigned IP address range of each DHCP server (hereinafter, referred to as “remaining allocation”) is equalized so as to equalize the remaining number of IP addresses that can be assigned to each DHCP server (hereinafter referred to as “allocation remaining amount”). Readjust the size of the allocation range (hereinafter referred to as allocation capacity) during operation.
However, in the VLAN, communication between the host and the DHCP server necessary for the DHCP service may be hindered due to the link disconnection between the LANs. Further, the frequency of link disconnection may vary depending on wide area connection or local connection. For this reason, it is not always possible to provide the DHCP service with high reliability simply by equalizing the remaining allocation amount.

In response to this problem, the address allocation capacity control device that manages the configuration information of the DHCP server takes into consideration the allocation disconnection excess / underestimation value for each LAN in consideration of the level of link disconnection probability between LANs in addition to the remaining allocation amount. There is a technique for obtaining a service outage risk ratio (SOR) that is, and readjusting the allocated capacity so that the average value and the variance value of the SOR fall within a certain range (see, for example, Non-Patent Document 3).
Ralph Droms, “Dynamic Host Configuration Protocol,” IETF RFC2131, March 1997. Ralph Droms, et al, “DHCP Failover Protocol,” draft-ietf-dhc-failover-12.txt, March 2003. Kenji Hori, et al, “Extension of DHCP for Reliable IP Address Assignment Service in Wide-area VLANs,” In Proc. Of the 10-th Asia-Pacific Network Operations and Management Symposium (APNOMS2007), IS.2-5, October 2007.

However, in the technique described in Non-Patent Document 3, since there is no restriction on the adjustment range of the allocated capacity once, there is a risk of address depletion when address allocation requests increase locally and temporarily in some LANs. There is a problem that there is. Specifically, as a result of over-optimization, that is, allocation capacity is biased to LANs that have increased address allocation requests, and the allocation capacity of other LANs is excessively reduced, the risk of address exhaustion increases when link disconnection occurs. End up.
The present invention has been made in view of the above points, and an object of the present invention is to increase the reliability of the DHCP service by suppressing an excessive increase / reduction of the allocation capacity with respect to a local and temporary increase in address allocation requests. It is an object of the present invention to provide an address allocation capacity control device and a program that can be realized.

The present invention has been made to solve the above-described problems, and one aspect of the present invention provides an address of the segment in a network in which a plurality of segments including at least one DHCP server are configured by one address space. An address allocation capacity control device for controlling allocation capacity, wherein an allocation remaining amount monitoring unit for acquiring the address allocation remaining amount of the DHCP server, and the DHCP for each segment based on the address allocation remaining amount of the DHCP server A stop risk rate calculation unit for calculating a service stop risk rate for address allocation by the server, and an allocation capacity calculation unit for calculating an address allocation capacity for each segment by setting a limit on the increase / decrease amount according to the service stop risk rate; An address allocation capacity control device comprising:

Another embodiment of the present invention is the above address assignment capacity control device, the allocated capacity calculation unit and constraints that place limits on the amount of change in address allocated capacity, the average value of the outage risk rate The address allocation capacity of each segment is calculated using a linear programming method so as to minimize.

Another embodiment of the present invention is the above address assignment capacity control device, the allocated capacity calculation unit and constraints that place limits on the amount of change in address allocated capacity, dispersion value of the outage risk rate The address allocation capacity of each segment is calculated using a quadratic programming method so as to minimize.

Further, according to one aspect of the present invention, in a network in which a plurality of segments including at least one DHCP server are configured by one address space, the address allocation remaining of the DHCP server is stored in a computer that controls the address allocation capacity of the segment. A step of obtaining an amount, a step of calculating a service outage risk rate of address assignment in the DHCP server for each segment based on the remaining address assignment amount of the DHCP server, and an increase / decrease according to the service outage risk rate and assigned capacity calculating step of a limit on the amount to calculate the address assignment capacity of each segment, a program for execution.

Another embodiment of the present invention, in the above-mentioned program, the allocated capacity calculation step, a constraint condition that limits on increase or decrease the amount of address allocated capacity, to minimize the mean value of the service stop hazard ratio Thus, the address allocation capacity of each segment is calculated using linear programming.

Another embodiment of the present invention, in the above-mentioned program, the allocated capacity calculation step, and that the limits on increase or decrease the amount of address allocated capacity and constraints, to minimize the variance of the outage risk rate Thus, the address allocation capacity of each segment is calculated using the quadratic programming method.

  According to the present invention, the address allocation capacity control device calculates the service stoppage risk rate for each segment, and determines the allocation capacity of each DHCP server according to the calculated service stoppage risk rate. At this time, the address allocation capacity control device limits the adjustment range of the allocation capacity. For this reason, the allocated capacity of the DHCP server can be dynamically readjusted during operation while suppressing over-optimization. As a result, an excessive increase / reduction in the allocated capacity with respect to a local and temporary increase in the address allocation request is suppressed, and high reliability of the DHCP service can be achieved under various conditions.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
For ease of explanation, terms are defined as follows for the entire specification.
Allocation capacity: Number of allocatable IP addresses of each DHCP server Allocation number: Number of IP addresses already allocated to clients Allocation remaining capacity: Allocation capacity-number of allocation Allocation range: IP address range that each DHCP server can allocate

[Network configuration]
FIG. 1 is a schematic diagram showing a network configuration of a DHCP service system according to an embodiment of the present invention.
In the DHCP service system, a plurality of LANs 3 (segments) are logically integrated into one virtual VLAN by the VLAN switch 5. A plurality of remotely located LANs 3 are connected to each other via a WAN (Wide Area Network, such as the Internet) 4.
In the example shown in this figure, segment A and segment B are connected via a VLAN switch 5 for LAN connection. The segment A, the segment C, and the segment D are connected to each other via the WAN 4 by a WAN connection VLAN switch 5.

  One LAN 3 includes at least one DHCP server 2. The DHCP server 2 assigns an address to the client 6 connected to the network. Therefore, an allocation range is set for each DHCP server 2 so that different DHCP servers 2 do not allocate the same address to different clients 6. A plurality of clients 6 connected to the LAN 3 are assigned one IP address from the reachable DHCP server 2 by making an address assignment request in accordance with DHCP set at the time of activation.

  In addition, an address allocation capacity control device 1 is provided in the VLAN. The address allocation capacity control device 1 communicates with all DHCP servers 2 in the VLAN. The address allocation capacity control device 1 calculates the allocation capacity for each DHCP server 2 and determines the allocation range of each DHCP server 2. Further, the determined allocation range is notified to each DHCP server 2. The function of the address allocation capacity control device 1 may be installed in any one DHCP server 2.

In such a DHCP service system, there are three possible causes for the stop of the DHCP service in a certain LAN 3 as follows.
(Stop factor 1) When all the DHCP servers 2 in the LAN 3 have failed (Stop factor 2) When the remaining allocation amount of all the DHCP servers 2 in the LAN 3 becomes 0 (Stop factor 3) Adjacent to the LAN 3 When all links to WAN4 or LAN3 are broken

  Based on the stop factors 1 to 3, the requirements for the DHCP service system on the VLAN are summarized as follows. Hereinafter, the probability that the DHCP service in a certain LAN 3 cannot be used is referred to as a service outage risk SOR (Service Outage Risk).

(Requirement 1) The DHCP server 2 can be made redundant and distributed in the VLAN.
This is because as the number of DHCP servers 2 in the VLAN increases, the redundancy becomes higher and the SOR due to server failure becomes smaller. Also, the more DHCP servers 2 are in the same LAN 3, the smaller the SOR due to LAN isolation. Here, redundancy means that (1) IP addresses in the same subnet can be assigned without duplication from a plurality of DHCP servers 2 at the same time, and (2) duplication of address assignment occurs even when recovery from server failure or LAN isolation Each DHCP server 2 has a different allocation range at all times so as not to make it happen.

(Requirement 2) The allocated capacity of each DHCP server 2 can be readjusted.
This is because the DHCP server 2 group of the LAN 3 that is easily isolated can assign a lot of new addresses. When the number of DHCP servers 2 in the same LAN is constant, if the DHCP server 2 group in the LAN 3 can newly allocate as many addresses as possible when the LAN is isolated, it can withstand the isolated state for a long time. This is because the SOR due to becomes smaller.

(Requirement 3) SOR can be stably suppressed even for various conditions related to the temporal distribution of the number of activations of the client 6 and the spatial distribution on the VLAN.
This is because such conditions cannot always be specified before the operation starts.

[Function configuration]
FIG. 2 is a block diagram showing the configuration of the address allocation capacity control device 1 and the DHCP server 2 according to the present embodiment.
The address allocation capacity control device 1 includes a stop risk rate calculation unit 101, an allocation capacity calculation unit 102, an allocation range storage unit 103, an allocation range setting unit 104, an allocation remaining amount monitoring unit 105, and an allocation range determination unit 106. And comprising.
The allocated remaining amount monitoring unit 105 acquires the allocated remaining amount from each DHCP server 2. The stop risk rate calculation unit 101 calculates the service stop risk rate SOR of each LAN 3 according to the allocated remaining amount acquired by the allocated remaining amount monitoring unit 105. The allocated capacity calculation unit 102 calculates the allocated capacity to each LAN 3 based on the service stop risk rate SOR calculated by the stop risk rate calculation unit 101. The allocation range determination unit 106 determines the allocation range of each DHCP server 2 based on the allocation capacity calculated by the allocation capacity calculation unit 102 and stores the allocation range in the allocation range storage unit 103. The allocation range storage unit 103 stores the allocation range of each DHCP server 2. The allocation range setting unit 104 notifies each DHCP server 2 of the allocation range based on information in the allocation range storage unit 103.

The DHCP server 2 includes an allocation range request unit 201, an allocation range reception unit 202, an address allocation storage unit 203, an address allocation unit 204, and an allocation remaining amount notification unit 205.
The allocation range request unit 201 inquires the address allocation capacity control device 1 about the allocation range in the DHCP server 2. The allocation range receiving unit 202 receives the allocation range in the DHCP server 2 from the address allocation capacity control device 1 and stores the received allocation range in the address allocation storage unit 203. The address allocation storage unit 203 stores the allocation range of the DHCP server 2, addresses already allocated to each client 6, and addresses that can be allocated to each client 6. When the address assignment unit 204 receives an address assignment request from the client 6, the address assignment unit 204 notifies the client 6 of an assignable address. At this time, the address assignment unit 204 refers to the address assignment storage unit 203 and acquires an assignable address. The allocated remaining amount notification unit 205 transmits the allocated remaining amount to the address allocated capacity control device 1 when an address is allocated to each client 6 of the DHCP server 2 or when the address of each client 6 is released. In this embodiment, the allocated remaining amount is transmitted when an address is allocated to each client 6 and when the address of each client 6 is released. However, the allocated remaining amount may be transmitted every predetermined time. .
Note that the address allocation capacity control apparatus 1 may include processing functions of the respective units of the DHCP server 2 shown in FIG.

[Method for calculating the risk of service outage]
Hereinafter, the process of the stop danger rate calculation unit 101 of the address allocation capacity control apparatus 1 will be described in detail.
Here, in the address allocation capacity control apparatus 1, the connection topology between the LANs 3, the probability of each link disconnection, the number of DHCP servers 2 in each LAN 3, and the initial value of the allocated capacity are set.

The outage risk factor calculation unit 101 calculates the service outage risk factor SOR (k) of the kth LAN (k) in the VLAN using the following parameters.
(1) DHCP server 2 failure rate f _server
(2) Depletion probability f _pool that the remaining allocation amount of DHCP server 2 of LAN (k) is all 0
(3) Failure probability f _link (k, j) of link (j) in LAN (k)

  Thereby, the service stoppage risk rate SOR (k) of the DHCP service in the LAN (k) is defined by the following formula (1). Equation (1) takes into account stop factors 1 to 3.

s (k): Number of DHCP servers in LAN (k) f _server : DHCP server failure rate (constant for all DHCP servers)
f _pool (k): Depletion probability that the remaining allocation of DHCP server of LAN (k) is all 0 f _link (k, j): Failure probability of link (j) of LAN (k) (time invariant)
l (k): number of links of LAN (k) (number of adjacent LANs)

The depletion probability f _pool (k) is defined by the following equation (2). According to equation (2), the depletion probability under the assumption that the number of allocations increases from the allocation remaining amount (c (k) -a (k)) thereafter at a constant allocation rate (g (k)). f _pool (k) means being inversely proportional to time.

c (k): Total allocated capacity of all DHCP servers in LAN (k) a (k): Total allocated number of all DHCP servers in LAN (k) g (k): All DHCP servers in LAN (k) Allocation ratio b: coefficient uptime (k): average operating time of all DHCP servers of LAN (k)

[Allocation capacity calculation method]
Next, the processing of the allocated capacity calculation unit 102 of the address allocated capacity control apparatus 1 will be described in detail.
The allocated capacity calculation unit 102 calculates an address allocated capacity c (k) in each LAN according to the SOR (k) calculated by the stop risk rate calculation unit 101. Specifically, when the average value of the entire SOR (k) VLAN deviates from a predetermined range, the allocated capacity calculation unit 102 calculates the average of the SOR (k) over the entire VLAN by linear programming (LP). The allocated capacity c (k) that minimizes the value is calculated. Further, when the variance value over the entire VLAN of SOR (k) deviates from a predetermined range, the allocated capacity calculation unit 102 calculates the variance value of SOR (k) over the entire VLAN by quadratic programming (QP). The allocated capacity c (k) is recalculated so as to minimize it.
However, if there is no restriction on the one-time adjustment range of the allocated capacity, there may be a case where address exhaustion is caused under the condition that the service stop danger rate SOR (k) increases locally and temporarily in some LANs 3. Specifically, the allocated capacity is biased toward the LAN 3 with the increased service outage risk rate SOR (k), and the allocated capacity of the other LAN 3 is excessively reduced (this phenomenon is hereinafter referred to as over-optimization). As a result, in the LAN 3 in which the allocated capacity is reduced, address exhaustion is likely to occur when a subsequent link disconnection occurs. Therefore, the above (Requirement 3) cannot be satisfied.
Therefore, in the present invention, the maximum increase / decrease rate MaxDeltaC of the allocated capacity is added as a constraint condition. The following formulas (3), (4), and (5) are the constraints on the allocated capacity. Expression (3) represents that the total allocated capacity in the VLAN becomes the total number of available IP addresses N in the VLAN. Formula (4) represents that the allocated capacity of each LAN 3 is equal to or greater than the allocated number. Formula (5) represents that the adjustment range of the allocated capacity once does not exceed the maximum increase / decrease rate.

N: Total number of IP addresses available in the VLAN c _prev (k): Current total allocated capacity of all DHCP servers in LAN (k) MaxDeltaC: Maximum increase / decrease rate of allocated capacity

[Allocated capacity calculation method by linear programming]
Next, a method of calculating the allocated capacity c (k) that minimizes the average value of SOR (k) under the constraint conditions (3) to (5) will be described.
First, the mean value minimization of SOR (k) by LP will be described. A method for obtaining c (k) that minimizes the average value Avg (SOR (k)) of SOR (k) when a constraint condition is involved will be described below. Avg (SOR (k)) is defined as the following equation (6). The allocated capacity calculation unit 102 calculates c (k) that minimizes Equation (6) using LP under the constraint equations (3), (4), and (5).

  In the following, a method is described in which the simplex method, which is a typical high-speed LP method, can be applied so as not to hinder the processing of the address allocation capacity control apparatus 1 as the DHCP server 2. The simplex method is a well-known technique. In order to make the simplex method applicable, first, equation (1) is rewritten as the following equation (7).

  The definition of d (k) is the following equation (8). The definition of e (k) is the following formula (9). d (k) and e (k) are constants determined by each LAN 3.

  Substituting equation (7) into equation (6) yields equation (10) below.

  Next, in order to make the simplex method applicable, the equation (2) is rewritten into the following equation (11).

Since Expression (11) is not a linear expression of c (k), Expression (10) is not a linear expression of c (k), and the minimization problem using Expression (10) as an objective function is solved by the simplex method. I can't. Therefore, by linearly approximating f _pool (k) within the range of equation (5), it can be expressed as a linear equation of c (k), and the simplex method can be applied.

FIG. 3 is a schematic diagram showing an outline of linear approximation of the depletion probability f _pool (k) in the present embodiment. The vertical axis of the graph shown in this figure is the depletion probability f _pool (k), and the horizontal axis is the allocated capacity c (k).
First, c (k) is within the range of equation (5), and in the vicinity of a point where c (k) = c _prev (k) on the hyperbola shown in the graph of FIG. Is linearly approximated.

  Next, the following equation (13) is calculated by substituting equation (12) into equation (10).

  Solving the minimization problem using this equation (13) as an objective function is equivalent to solving the minimization problem using the objective function of the following equation (14) excluding the constant term. Therefore, the objective function is defined as the following formula (14).

FIG. 4 is a schematic diagram showing an overview of the linear interpolation method of A (k) in the present embodiment.
Equation (12), (14) A (k) at the two points _c in FIG. (K) = c prev (k ) (1-CalcDeltaC) and _{c (k) = c prev (} k) (1 + CalcDeltaC) Is obtained by linear interpolation. That is, A (k) is defined by the following formula (15). Here, CalcDeltaC is a calculation parameter and is an arbitrary positive real number that is less than MaxDeltaC. For example, MaxDeltaC can be set to 0.1, CalcDeltaC can be set to 0.05, and the like.

  As described above, in the optimization problem after rewriting, the objective functions are the expressions (14) and (15), and the determination conditions are the expressions (3), (4), and (5). Accordingly, the allocated capacity calculation unit 102 uses the simplex method to minimize the allocated capacity c under the condition formulas (3), (4), and (5) for the purpose of minimizing the expression (14) and thereafter. (K) is calculated.

[Allocated capacity calculation method by quadratic programming]
Next, the dispersion value minimization of SOR (k) by QP will be described.
Here, a method of obtaining c (k) that minimizes the variance value Var (SOR (k)) of SOR (k) under the constraint equations (3), (4), and (5) is shown. Var (SOR (k)) is defined as the following equation (16).

  The allocated capacity calculation unit 102 calculates c (k) that minimizes Expression (16) using QP under the constraint condition expressions (3), (4), and (5). For the same reason as in the case of the average minimization, here, one of the representative fast solutions of QP, the sequential quadratic optimization (SQP) method is applied. Since the SQP method is a quadratic optimization, it is not necessary to modify the expression (16) and the constraint expressions (3), (4), and (5), and can be directly applied.

[Process flow]
FIG. 5 is a flowchart showing an example of the flow of the allocated capacity calculation process in the present embodiment. For example, the address allocation capacity control device 1 starts the allocation capacity calculation process at the following timing.
(1) Every elapse of a predetermined time (2) When the allocation remaining amount is notified from the DHCP server 2

When the process starts, first, the outage risk factor calculation unit 101 calculates the service outage risk factor SOR (k) of each DHCP server 2 (step S1). Next, the allocated capacity calculation unit 102 calculates an average value Avg (SOR (k)) of the calculated service outage risk rate SOR (k) (step S2). Next, the allocated capacity calculation unit 102 determines whether or not the calculated average value Avg (SOR (k)) is within a predetermined range (step S3). If it is not within the predetermined range, the process proceeds to the next step S4. If it is within the predetermined range, the process is terminated. Next, the allocated capacity calculation unit 102 calculates the allocated capacity c (k) of each DHCP server 2 so as to minimize Avg (SOR (k)) using linear programming (step S4). Next, the allocation range determination unit 106 determines the allocation range of each DHCP server 2 based on the calculated allocation capacity (step S5). Finally, the allocation range setting unit 104 notifies the determined allocation range to each DHCP server 2 and ends the process (step S6).
In this example, the allocated capacity c (k) is calculated based on the average value Avg (SOR (k)) of the service outage risk rate SOR (k), but the variance value Var of the service outage risk rate SOR (k). When (SOR (k)) is outside the predetermined range, the allocated capacity c (k) of each DHCP server 2 is calculated using quadratic programming so as to minimize Var (SOR (k)). May be.

  FIG. 6 is a sequence diagram showing an example of processing in the DHCP service system in the present embodiment. In this figure, there are two DHCP servers 2, but the sequence is similar when there are three or more. That is, the third and subsequent DHCP servers 2 also communicate with the address allocation capacity control device 1 and the client 6 in the sequence shown in this figure.

  When activated, the DHCP server 2 transmits an allocation range request to the address allocation capacity control device 1 in order to acquire its allocation range (step S101). In response to this, the address allocation capacity control device 1 transmits an allocation range response including the corresponding allocation range to the DHCP server 2 (step S102). When receiving the allocation range, the DHCP server 2 starts an address allocation service for the client 6 (step S103).

  On the other hand, when activated, the client 6 transmits an address assignment request to the DHCP server 2 in order to connect to the network (step S104). In response to this, the DHCP server 2 transmits an address assignment response including an assignable address to the client 6 (step S105). The client 6 can connect to the network using the received address. At this time, the DHCP server 2 notifies the address allocation capacity control device 1 of the allocated remaining amount (step S106). Thereby, the address allocation capacity control device 1 can grasp the allocation remaining amount of each DHCP server 2. Further, the client 6 transmits an address release request to the DHCP server 2 when terminating the connection to the network (step S107). In response to this, the DHCP server 2 updates the received address to an assignable address, and transmits an address release response to the client 6 (step S108). At this time, the DHCP server 2 notifies the allocated address remaining capacity to the address allocation capacity control device 1 (step S109).

  When the address allocation capacity control apparatus 1 is notified of the allocated remaining capacity, it starts the allocated capacity calculation process shown in FIG. 5 (step S110). Then, the address allocation capacity control device 1 notifies the determined allocation range to each DHCP server 2 (step S111). Each DHCP server 2 replaces the allocation range in the address allocation storage unit 203 with the notified allocation range (step S112). In this way, the address allocation capacity control device 1 readjusts the allocation range of each DHCP server 2.

  As described above, according to the present embodiment, the address allocation capacity control device 1 calculates the service outage risk rate SOR for a VLAN including a plurality of LANs 3, and each DHCP server 2 according to the calculated service outage risk rate SOR. Determine the allocated capacity. At this time, the address allocation capacity control device 1 limits the adjustment range of the allocation capacity. For this reason, it is possible to dynamically readjust the allocated capacity of the DHCP server 2 during operation while suppressing excessive optimization. As a result, excessive increase / reduction of the allocated capacity with respect to local and temporary increases in address requests can be suppressed, and high reliability of the DHCP service can be achieved under various conditions.

Further, the program for realizing each step shown in FIG. 5 is recorded on a computer-readable recording medium, and the program recorded on the recording medium is read into the computer system and executed, thereby executing the allocated capacity calculation process. May be performed. Here, the “computer system” may include an OS and hardware such as peripheral devices.
Further, the “computer system” includes a homepage providing environment (or display environment) if a WWW system is used.
The “computer-readable recording medium” means a flexible disk, a magneto-optical disk, a ROM, a writable nonvolatile memory such as a flash memory, a portable medium such as a CD-ROM, a hard disk built in a computer system, etc. This is a storage device.

Further, the “computer-readable recording medium” means a volatile memory (for example, DRAM (Dynamic DRAM) in a computer system that becomes a server or a client when a program is transmitted through a network such as the Internet or a communication line such as a telephone line. Random Access Memory)), etc., which hold programs for a certain period of time.
The program may be transmitted from a computer system storing the program in a storage device or the like to another computer system via a transmission medium or by a transmission wave in the transmission medium. Here, the “transmission medium” for transmitting the program refers to a medium having a function of transmitting information, such as a network (communication network) such as the Internet or a communication line (communication line) such as a telephone line.
The program may be for realizing a part of the functions described above. Furthermore, what can implement | achieve the function mentioned above in combination with the program already recorded on the computer system, and what is called a difference file (difference program) may be sufficient.

  As described above, the embodiment of the present invention has been described in detail with reference to the drawings. However, the specific configuration is not limited to the above, and various design changes and the like can be made without departing from the scope of the present invention. It is possible to

It is the schematic which shows the network structure of the DHCP service system by one Embodiment of this invention. It is the block diagram which showed the structure of the address allocation capacity control apparatus by this embodiment, and a DHCP server. It is the schematic which showed the outline | summary of the linear approximation of the depletion probability _fpool (k) in this embodiment. It is the schematic shown about the outline | summary of the linear interpolation method of A (k) in this embodiment. It is a flowchart showing an example of the flow of the allocation capacity calculation process in this embodiment. It is a sequence diagram showing an example of the process in the DHCP service system in this embodiment.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Address allocation capacity control apparatus 2 ... DHCP server 3 ... LAN 4 ... WAN 5 ... VLAN switch 6 ... Client 101 ... Stop risk rate calculation part 102 ... Allocation capacity calculation part 103 ... Allocation range determination part 104 ... Allocation range setting part 105 ... Allocation remaining amount monitoring unit 106 ... Allocation range determination unit 201 ... Allocation range request unit 202 ... Allocation range reception unit 203 ... Address storage unit 204 ... Address allocation unit 205 ... Allocation remaining amount notification unit

Claims (6)

An address allocation capacity control apparatus for controlling an address allocation capacity of the segment in a network in which a plurality of segments including at least one DHCP server are configured in one address space,
An allocation remaining amount monitoring unit for acquiring an address allocation remaining amount of the DHCP server;
A stop risk rate calculating unit that calculates a service stop risk rate for address allocation by the DHCP server for each segment based on the address allocation remaining amount of the DHCP server;
An allocated capacity calculation unit that calculates an address allocated capacity of each segment by setting a limit on the increase / decrease amount according to the service outage risk rate;
An address allocation capacity control apparatus comprising: The allocated capacity calculation unit and constraints that place limits on the amount of change in address allocated capacity, the address assignment capacity of each segment by using the linear programming method to minimize the average value of the outage risk rate The address allocation capacity control apparatus according to claim 1, wherein the address allocation capacity control apparatus calculates. The allocated capacity calculation unit, the providing a limit to increase or decrease the amount of address allocated capacity and constraints, address assignment capacity of each segment using quadratic programming to minimize the variance of the outage risk rate The address allocation capacity control apparatus according to claim 1, wherein: In a network in which a plurality of segments including at least one DHCP server are configured in one address space, a computer for controlling the address allocation capacity of the segments,
Obtaining an address allocation remaining amount of the DHCP server;
Calculating a service outage risk rate of address allocation in the DHCP server for each segment based on the remaining address allocation of the DHCP server;
Depending on the service stop hazard ratio, and assigned capacity calculating step of calculating the address assignment capacity of each segment restrictions on the decrease amount,
A program for running The allocated capacity calculation step, a constraint condition that limits on increase or decrease the amount of address allocated capacity, the address assignment capacity of each segment by using the linear programming method to minimize the average value of the outage risk rate The program according to claim 4, wherein the program is calculated. The allocated capacity calculation step, and that the limits on increase or decrease the amount of address allocated capacity and constraints, address assignment capacity of each segment using quadratic programming to minimize the variance of the outage risk rate The program according to claim 4, wherein the program is calculated.

Images