JP2012065011A - Name resolution apparatus and name resolution method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a name resolution apparatus that can automatically connect terminals such as SIP terminals to main apparatuses selected according to a predetermined policy.SOLUTION: The name resolution apparatus includes: reception means for receiving from a terminal a request for name resolution which includes a URL corresponding to a system including a master main apparatus and one or more slave main apparatuses; name resolution means for selecting one main apparatus from the master main apparatus and one or more slave main apparatuses according to a predetermined policy and acquiring an IP address of the selected main apparatus; and transmission means for replying to the terminal with the IP address.

Description

  The present invention relates to a name resolution apparatus and a name resolution method for obtaining an IP (Internet Protocol) address corresponding to a URL (Uniform Resource Locator) when a terminal such as a SIP (Session Initiation Protocol) terminal is connected to a main apparatus. .

  In the invention described in Patent Document 1, a physical package included in a slave main device is used as a package for controlling a digital terminal, a line, and the like. The physical package included in the slave main unit is associated with the virtual slot included in the master main unit using the correspondence table, and the master main unit uses the association to determine the physical package of the slave main unit. It was possible to control the digital terminals and lines under it. Since the physical package included in each slave controls a digital terminal or the like using the CPU of the slave main device, it is possible to avoid the processing for such control from being concentrated on the CPU of the master main device. .

JP 2009-003923 A

  Here, the SIP terminal is also connected to a system including the master main unit and one or more slave main units. As a result, the versatility and usefulness of this system could be greatly improved.

  However, the SIP terminal is not accommodated in the physical package of the slave main device. Since the master main apparatus directly controls the SIP terminal, processing for controlling the SIP terminal is concentrated on the CPU of the master main apparatus. In particular, heavy processing such as message processing is required to control each SIP terminal. Therefore, the number of SIP terminals that can be connected to a system including a master main unit and one or more slave main units has been considerably limited.

  Further, even if each SIP terminal is connected to any main device of a system including a master main device and one or more slave main devices, it is reasonably determined to which main device each SIP terminal is connected. The device has not existed before. For this reason, it became necessary for a person to make a decision as an alternative to that decision, and the decision was not always reasonable.

  Accordingly, an object of the present invention is to provide a name resolution device, a name resolution method, and a program that allow a terminal such as a SIP terminal to be automatically connected to a main device selected according to a predetermined policy. .

  According to the first aspect of the present invention, a receiving unit that receives a request for name resolution from a terminal, a URL included in the request, and a master main unit and one or more slave main units A match confirmation means for confirming whether or not a match with a system corresponding to the system included, and when the confirmation result by the match confirmation means is affirmative, the master main apparatus and the one or more slave mains according to a predetermined policy There is provided a name resolution device comprising: main device selection means for selecting one main device from the devices; and transmission means for returning an IP address of the selected main device to the terminal.

  According to the second aspect of the present invention, a reception step of receiving a request for name resolution from a terminal, a URL included in the request, and a master main device and one or more slave main devices are checked. A match confirmation step for confirming whether or not it corresponds to a system corresponding to the system including the same, and when the confirmation result by the match confirmation step is affirmative, the master main device and the one or more slave mains according to a predetermined policy There is provided a name resolution method comprising: a main device selection step of selecting one main device from the devices; and a transmission step of returning an IP address of the selected main device to the terminal.

  According to a third aspect of the present invention, a receiving means for receiving a request for name resolution from a terminal, a URL included in the request, and a master main device and one or more slave main devices are detected. A match confirmation means for confirming whether or not a match with a system corresponding to the system included, and when the confirmation result by the match confirmation means is affirmative, the master main apparatus and the one or more slave mains according to a predetermined policy A program for causing a computer to function as a name resolution device, comprising: main device selection means for selecting one main device from the devices; and transmission means for returning an IP address of the selected main device to the terminal. Is provided.

  According to the present invention, since the name resolution device selects the main device to which the terminal is connected according to a predetermined policy, it is possible to automatically connect the terminal to the main device selected according to the predetermined policy It becomes.

It is a block diagram which shows the structure of each main apparatus contained in the system by Embodiment 1 of this invention, and the SIP terminal connected to a system. It is a block diagram which shows the structure of the name resolution apparatus by Embodiment 2 of this invention. It is a conceptual diagram which shows the structure of the information regarding the position of each main apparatus shown in FIG. It is a conceptual diagram which shows the structural example of the system corresponding to the structure of the information regarding the position of each main apparatus shown in FIG. It is a flowchart which shows the whole name resolution method by Embodiment 2 of this invention. It is a flowchart which shows the method of selecting the main apparatus shown in FIG. It is a block diagram which shows the structure of the main apparatus by Embodiment 3 of this invention.

  DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments for carrying out the present invention will be described in detail with reference to the drawings.

[Embodiment 1]
In the first embodiment, a configuration in which a plurality of SIP terminals are distributed and connected to a plurality of main devices will be described.

  Referring to FIG. 1, the entire system according to the embodiment of the present invention includes a master main device 101, a first slave main device 102-1, a second slave main device 102-2, and SIP terminals 104-1 to 104-. 9 is included.

  The number of master main devices 101 is one. The number of second slave main devices is 2 in the example of FIG. 1, but may be other numbers.

  The master main apparatus 101, the first slave main apparatus 102-1 and the second slave main apparatus 102-2 are connected by the SIP link 103. The SIP link 103 transmits and receives communication messages between main devices.

  In the example of FIG. 1, two SIP terminals 104-4 and 104-5 are connected to the master main apparatus 101 via TCP / IP, and three SIP terminals 104 are connected to the first slave main apparatus 102-1. -1 to 104-3 are connected over TCP / IP, and four SIP terminals 104-6 to 104-9 are connected to the second slave main apparatus 102-2. The number of SIP terminals to be performed is arbitrary.

  The master main apparatus 101 includes a CAPS / OPMS 201, an IOCS 203, multilink units 205-1 to 205-3, and a SIP terminal accommodating unit 207. The number 3 of multilink units 205 corresponds to 3 which is the number of main devices. Therefore, if the slave main device is added, the multilink unit 2-5 is also added accordingly.

  The CAPS of the CAPS / OPMS 201 is a call control module, and the OPMS is a package and terminal management module. Here, the package is, for example, the SIP terminal accommodating unit 207. IOCS is an input / output control module.

  As described above, the multilink unit 205 is provided in the same number as the number of main devices included in the system, and links the IOCS 203 and one SIP terminal accommodating unit 207 via the SIP link 103.

  The SIP terminal accommodating unit 207 includes a transmission side processing unit 209, a reception side processing unit 211, and a TCP / IP unit 213.

  The transmission side processing unit 209 generates a transmission SIP message composed of text based on the transmission binary data transmitted from the multilink unit 205 and passes the transmission message to the TCP / IP unit 213.

  The reception side processing unit 211J analyzes the received SIP message passed from the TCP / IP unit 213 and transmits the analysis result to the multilink unit 205 as a text message.

  The TCP / IP unit 213 handles transmission / reception of SIP messages among the transmission processing unit 209, the reception processing unit 211, and the SIP terminal 104.

  The CAPS / OPMS 201, the IOCS 203, and the multilink units 205-1 to 205-3 are realized by the CPU of the master main apparatus 101 executing a program for causing the CPU of the master main apparatus 101 to function as each of these parts. The This program is stored in a memory (not shown) of the master main unit 101.

  The SIP terminal accommodation unit 207 of the master main apparatus 101 is realized by the CPU of the master main apparatus 101 executing a program for causing the CPU of the master main apparatus 101 to function as the SIP terminal accommodation unit 207. This program is also stored in the memory (not shown) of the master main unit 101.

  The SIP terminal accommodation unit 207 of the first slave main device 102-1 stores a program for causing the CPU of the first slave main device 102-1 to function as the SIP terminal accommodation unit 207. This is realized by executing the CPU. This program is stored in a memory (not shown) of the first slave main device 102-1.

  The SIP terminal accommodation unit 207 of the second slave main device 102-2 stores a program for causing the CPU of the second slave main device 102-2 to function as the SIP terminal accommodation unit 207. This is realized by executing the CPU. This program is stored in a memory (not shown) of the second slave main device 102-2.

  Each of the above parts is obtained by instantiating a class in a program in a memory.

  The CAPS / OPMS 201 and the IOCS 203 are also generated in the first slave main device 102-1. When the master main unit 101 is operating normally, the CAPS / OPMS 201 and the IOCS 203 of the first slave main unit 102-1 are in a standby state, but when the master main unit 101 is down, the first slave main unit 101 The CAPS / OPMS 201 and the IOCS 203 of the device 102-1 are in operation. At this time, the multilink unit 205 is also generated in the first slave main device 102-1.

  The same applies to the second slave device.

[Embodiment 2]
In the second embodiment, a configuration will be described in which a main device that is a connection destination of a SIP terminal is selected and the SIP terminal is connected to the main device.

  Referring to FIG. 2, the name resolution device 300 according to the second embodiment includes a TCP / IP unit 301, a name resolution unit 302, and a storage unit 303.

  The TCP / IP unit 301 connects the name resolution unit 302 to the IP network. In particular, the name resolution request sent from the IP terminal is sent to the name resolution unit 302, and the IP address returned from the name resolution unit 302 is sent to the IP terminal that sent the name resolution request accordingly.

  When the name resolution unit 302 receives a name resolution request from the IP terminal via the TCP / IP unit 301, the name resolution unit 302 selects one master unit from the master main unit and one or more slave main units according to a predetermined policy. Then, the IP address of the selected main device is obtained.

  The storage unit 303 includes information 303-1 regarding the activation status of each main device, information 303-2 regarding the position of each main device, information 303-3 regarding the function of each main device, and each terminal (IP terminal for each main device). Information 303-4 concerning the registration status, IP address 303-5 of each main apparatus, information 303-7 concerning the position of each terminal, and information 303-9 concerning the function of each terminal.

  Returning to the description of the name resolution unit 302, this is because each main device stored in the storage unit 303 is selected when one main device is selected from the master main device and one or more slave main devices according to a predetermined policy. Information 303-1 related to the activation status of each device, information 303-2 related to the position of each main device, information 303-3 related to the function of each main device, information related to the registration status of each terminal (including an IP terminal) to each main device. 303-4, and further referring to information 303-7 regarding the position of the terminal stored in the storage unit 303 and information 303-9 regarding the function of the terminal, if one main device is selected, the storage unit The IP address of the selected main device is read out from the IP addresses 303-5 of each main device stored in 303, and is transferred to the TCP / IP unit 301.

  Referring to FIG. 3, the information 303-2 regarding the position of each main device has items of main device identification information, main device type and position identification information, and includes the values of these items for each main device. . The example shown in FIG. 3 corresponds to the connection configuration as shown in FIG.

  Next, the operation of the name resolution apparatus will be described with reference to FIGS.

  First, the SIP terminal 104 attempting to connect to any main device included in the system including the master main device and one or more slave main devices transmits a name resolution request to the name resolution device (step S401). This request includes the URL of the system. The TCP / IP unit 301 of the name resolution device 300 receives this request (step S403).

  Next, the name resolution unit 302 of the name resolution device 300 determines whether or not the URL included in the request corresponds to the system (step S405). If so, it is included in the system. Is selected with reference to the information stored in the storage unit 303 according to a predetermined policy (step S409), and the IP address of the selected main device is acquired from the storage unit 303 ( Step S411).

  The TCP / IP unit 301 of the name resolution device 300 transmits the IP address acquired by the name resolution unit 302 to the requesting SIP terminal 104 (step S413). The SIP terminal 104 receives the IP address (step S415), and then transmits a connection request (REGISTER message) to the main apparatus having the IP address.

  Referring to FIG. 6, in selecting a main device, the name resolution unit 302 first reads information 303-1 related to the activation status of each main device from the storage unit 303 (step S409-1).

  Next, the name resolution unit 302 removes the main device that has not been activated from the selection targets based on the information 303-1 regarding the activation status of each main device (step S409-3).

  Next, the name resolution part 302 reads the information 303-2 regarding the position of each main apparatus from the memory | storage part 303 (step S409-5).

  Next, the name resolution unit 302 reads information 303-7 related to the location where the SIP terminal exists from the storage unit 303 (step S409-7).

  Next, the name resolution unit 302 compares the information related to the position of each main apparatus read out in step S409-5 with the information related to the position where the SIP terminal read out in step S409-7, and the information related to the position is determined as SIP. The main device that does not match the terminal is excluded from the selection targets (step S409-9). Here, the information regarding the position matches that, for example, “Tokyo”, which is information regarding the position of the SIP terminal, and “Tokyo”, which is information regarding the position of a certain main device, match. “Does not match” means, for example, that “Tokyo”, which is information related to the position of the SIP terminal, does not match “Osaka”, which is information related to the position of another main device. As the position information, other character strings may be used instead of place names, symbols, numbers, or the like may be used.

  Next, the name resolution part 302 reads the information 303-3 regarding the function of each main apparatus from the memory | storage part 303 (step S409-11).

  Next, the name resolution unit 302 reads information 303-9 related to the function of the SIP terminal from the storage unit (step S409-13).

  Next, the name resolution unit 302 compares the information on the function of each main device read in step S409-11 with the information on the function of the SIP terminal read out in step S409-13, and supports the function of the SIP terminal. The main device having no function is removed from the selection target (step S409-15). For example, if the SIP terminal has a call function, the main device that does not have the call function is excluded from selection. If the SIP terminal has a videophone function, the main device having no videophone function is excluded from selection.

  Next, the name resolution unit 302 checks the number of main devices that have not been excluded from the selection target (step S409-17).

  If the number is 1, the name resolution unit 302 selects the one main device that has not been excluded from the selection (step S409-19).

  If there are a plurality of numbers checked in step S409-17, the name resolution unit 302 reads out information 303-4 on the registration status of each terminal in each main device from the storage unit 303 (step S409-21), and selects it. Among the main devices that are not excluded, the main device with the fewest registered SIP terminals is selected (step S409-23).

  If the number checked in step S409-17 is zero, the name resolution unit 302 determines that the number of main devices to be selected among the main devices excluded from the selection targets is one or more. Conditions regarding the position of the apparatus are relaxed (step S409-25). Here, loosening the conditions means expanding the position where the main device that is not excluded from the selection target exists in the order from the position where the SIP terminal exists. Further, “near” means “near” in the geographical area or on the network.

  Next, the main device with the smallest number of registered terminals is selected from the main devices newly selected in step S409-27 (step S409-27).

[Embodiment 3]
In the second embodiment, the name resolution device 300 is provided separately from the main device. However, in the third embodiment, the name resolution device is included in the main device. FIG. 7 shows a main apparatus having such a configuration. Among the components shown in FIG. 7, the components shown in FIGS. 1 and 2 are denoted by the same reference numerals and description thereof is omitted. The TCP / IP unit 304 is a combination of the TCP / IP unit 213 shown in FIG. 1 and the TCP / IP unit 301 shown in FIG. 2, and in accordance with the port number, the connection destination is set to the SIP terminal accommodating unit 207 (transmission side processing). Switching to the name resolution unit 302.

  In the above embodiment, the example in which the device connected to the main device is a SIP terminal has been described. However, other terminals (for example, personal computers, mobile phones, etc.) that can connect the SIP terminal to the main device by IP. , PDA (Personal Digital Assistant), game machine).

  According to the present embodiment, it is possible to avoid concentration of IP terminals connected to a specific main apparatus. In addition, it is possible to avoid connecting an IP terminal to a main apparatus in which a failure has occurred. Furthermore, since it is possible to avoid connecting the IP terminal and the main apparatus that are located at a distance from each other, it is possible to reduce the amount of communication in the network. Furthermore, it is possible to avoid erroneously connecting the IP terminal to a main apparatus that does not have a function corresponding to the function of the IP terminal.

  A part or all of the above-described embodiment can be described as in the following supplementary notes, but is not limited thereto.

(Appendix 1)
Receiving means for receiving a request for name resolution from a terminal including a URL corresponding to a system including a master main device and one or more slave main devices;
Name resolution means for selecting one master device from the master master device and one or more slave master devices according to a predetermined policy, and obtaining an IP address of the selected master device;
Transmitting means for returning the IP address to the terminal;
A name resolution device comprising:

(Appendix 2)
The name resolution device according to attachment 1, wherein
The main device selection means, when making the selection, information related to the activation status of each main device, information related to the position of each main device, information related to the registration status of each terminal to each main device, and the function of each main device A name resolution apparatus characterized by referring to at least one type of information and information of a terminal corresponding to the at least one type of information.

(Appendix 3)
The name resolution device according to appendix 2,
A name resolution apparatus further comprising storage means for storing the various information.

(Appendix 4)
The name resolution device according to appendix 2 or 3,
The name resolution device, wherein the main device selection means refers to information related to the activation status of each main device when performing the selection, and excludes a main device that has not been activated from a selection target.

(Appendix 5)
The name resolution device according to any one of appendices 2 to 4,
The main device selection means, when making the selection, refers to information on the position of each main device and information on the position of the terminal, and gives priority to a main device closer to the terminal than other main devices. A name resolution device characterized by selecting.

(Appendix 6)
The name resolution device according to any one of appendices 2 to 5,
The main device selection means prioritizes a main device having a smaller number of registered terminals than other main devices by referring to information regarding the registration status of each terminal to each main device when performing the selection. A name resolution device characterized by being selected.

(Appendix 7)
The name resolution device according to any one of appendices 2 to 6,
The main device selection means refers to information on the function of each main device and information on the function of the terminal when performing the selection, and selects a main device that does not have a function corresponding to the function of the terminal. Name resolution device characterized by being excluded from the target.

(Appendix 8)
A system including a master main unit and one or more slave main units connected to the master main unit, further including the name resolution device according to any one of appendices 1 to 7, or the master main unit or The slave main device is a SIP terminal control system in a system having the function of the name resolution device according to any one of appendices 1 to 7,
The master main unit includes a plurality of multilink units each corresponding to each of the master main unit or the slave main unit,
The master main unit and each slave main unit include a SIP terminal accommodating unit for accommodating one or more SIP terminals,
Each of the multilink unit and each of the SIP terminal accommodating units are connected by a SIP link,
Each of the multilink units operates using the CPU of the master main unit,
Each SIP accommodating unit operates using a CPU of the slave main device or the master main device in which each SIP accommodating unit is included.

(Appendix 9)
Receiving a name resolution request from a terminal that includes a URL corresponding to a system including a master main unit and one or more slave main units;
A name resolution step of selecting one master device from the master master device and one or more slave master devices according to a predetermined policy, and obtaining an IP address of the selected master device;
A transmission step of returning the IP address to the terminal;
A name resolution method characterized by comprising:

(Appendix 10)
The name resolution method according to attachment 9, wherein
In the main device selection step, when performing the selection, information on the activation status of each main device, information on the position of each main device, information on the registration status of each terminal in each main device, and functions of each main device A name resolution method characterized by referring to at least one type of information and information of a terminal corresponding to the at least one type of information.

(Appendix 11)
The name resolution method according to attachment 10, wherein
The name resolution method further comprising the step of storing the various information in a storage means.

(Appendix 12)
The name resolution method according to appendix 10 or 11,
In the main device selection step, when performing the selection, the name resolution method is characterized by referring to information related to the activation status of each main device and excluding the main device that has not been activated from the selection target.

(Appendix 13)
The name resolution method according to any one of appendices 10 to 12,
In the main device selection step, when the selection is performed, the information on the position of each main device and the information on the position of the terminal are referred to, and the main device closer to the terminal is prioritized than the other main devices. Name resolution method characterized by selecting.

(Appendix 14)
The name resolution method according to any one of appendices 10 to 13,
In the main device selection step, when performing the selection, the information on the registration status of each terminal to each main device is referred to, and the main device having a smaller number of registered terminals than other main devices is prioritized. Name resolution method characterized by selecting to.

(Appendix 15)
The name resolution method according to any one of appendices 10 to 14,
In the main device selection step, when performing the selection, the information on the function of each main device and the information on the function of the terminal are referred to, and a main device having no function corresponding to the function of the terminal is selected. Name resolution method characterized by excluding from the target.

(Appendix 16)
A system including a master main device and one or more slave main devices connected to the master main device, further including the name resolution device according to any one of appendices 9 to 15, or the master main device or In the SIP terminal control method in a system in which the slave main device has the function of the name resolution device according to any one of appendices 9 to 15,
A plurality of multilink units each corresponding to each of the master main device or the slave main device are generated in the master main device,
Generate a SIP terminal accommodating unit for accommodating one or more SIP terminals in the master main apparatus and each slave main apparatus,
Connecting each of the multi-link units and each of the SIP terminal accommodating units by a SIP link;
Each multi-link unit is operated using the CPU of the master main unit,
A SIP terminal control method, wherein each SIP accommodating unit is operated using a CPU of the slave main device or the master main device in which each SIP accommodating unit is included.

(Appendix 17)
Receiving means for receiving a request for name resolution from a terminal including a URL corresponding to a system including a master main device and one or more slave main devices;
Name resolution means for selecting one master device from the master master device and one or more slave master devices according to a predetermined policy, and obtaining an IP address of the selected master device;
Transmitting means for returning the IP address to the terminal;
A program for causing a computer to function as a name resolution device.

(Appendix 18)
The program according to appendix 17, wherein
The main device selection means, when making the selection, information related to the activation status of each main device, information related to the position of each main device, information related to the registration status of each terminal to each main device, and the function of each main device A program that refers to at least one type of information and information of a terminal corresponding to the at least one type of information.

(Appendix 19)
The program according to appendix 18, wherein
The name resolution device further comprises storage means for storing the various information.

(Appendix 20)
The program according to appendix 18 or 19,
The main device selecting means refers to information relating to the activation status of each main device when performing the selection, and excludes a main device that has not been activated from a selection target.

(Appendix 21)
The program according to any one of appendices 18 to 20,
The main device selection means, when making the selection, refers to information on the position of each main device and information on the position of the terminal, and gives priority to a main device closer to the terminal than other main devices. A program characterized by selection.

(Appendix 22)
The program according to any one of appendices 18 to 21,
The main device selection means prioritizes a main device having a smaller number of registered terminals than other main devices by referring to information regarding the registration status of each terminal to each main device when performing the selection. A program characterized by being selected.

(Appendix 23)
The program according to any one of appendices 18 to 22,
The main device selection means refers to information on the function of each main device and information on the function of the terminal when performing the selection, and selects a main device that does not have a function corresponding to the function of the terminal. A program characterized by being excluded from the target.

101 Master Main Device 102-1 First Slave Device 102-2 Second Slave Device 103 SIP Link 104-1 to 104-9 SIP Terminal 201 CAPS / OPMS
203 IOCS
205-1, 205-2, 205-3 Multilink unit 207 SIP terminal accommodating unit 209 Transmission side processing unit 211 Reception side processing unit 213 TCP / IP unit

Claims (10)

Receiving means for receiving a request for name resolution from a terminal including a URL corresponding to a system including a master main device and one or more slave main devices;
Name resolution means for selecting one master device from the master master device and one or more slave master devices according to a predetermined policy, and obtaining an IP address of the selected master device;
Transmitting means for returning the IP address to the terminal;
A name resolution device comprising: The name resolution device according to claim 1,
The main device selection means, when making the selection, information about the activation status of each main device, information about the position status of each main device, information about the registration status of each terminal to each main device, and the function of each main device A name resolution device that refers to at least one type of information and information of a terminal corresponding to the at least one type of information. The name resolution device according to claim 2,
A name resolution apparatus further comprising storage means for storing the various information. The name resolution device according to claim 2 or 3,
The name resolution device, wherein the main device selection means refers to information related to the activation status of each main device when performing the selection, and excludes a main device that has not been activated from a selection target. The name resolution device according to any one of claims 2 to 4,
The main device selection means, when making the selection, refers to information on the position of each main device and information on the position of the terminal, and gives priority to a main device closer to the terminal than other main devices. A name resolution device characterized by selecting. The name resolution device according to any one of claims 2 to 5,
The main device selection means prioritizes a main device having a smaller number of registered terminals than other main devices by referring to information regarding the registration status of each terminal to each main device when performing the selection. A name resolution device characterized by being selected. The name resolution device according to any one of claims 2 to 6,
The main device selection means refers to information on the function of each main device and information on the function of the terminal when performing the selection, and selects a main device that does not have a function corresponding to the function of the terminal. Name resolution device characterized by being excluded from the target. A system comprising a master main unit and one or more slave main units connected to the master main unit, further comprising the name resolution device according to any one of claims 1 to 7, or the master main unit Or any one of the slave main devices is a SIP terminal control system in a system having the function of the name resolution device according to any one of claims 1 to 7,
The master main unit includes a plurality of multilink units each corresponding to each of the master main unit or the slave main unit,
The master main unit and each slave main unit include a SIP terminal accommodating unit for accommodating one or more SIP terminals,
Each of the multilink unit and each of the SIP terminal accommodating units are connected by a SIP link,
Each of the multilink units operates using the CPU of the master main unit,
Each SIP accommodating unit operates using a CPU of the slave main device or the master main device in which each SIP accommodating unit is included. Receiving a name resolution request from a terminal that includes a URL corresponding to a system including a master main unit and one or more slave main units;
A name resolution step of selecting one master device from the master master device and one or more slave master devices according to a predetermined policy, and obtaining an IP address of the selected master device;
A transmission step of returning the IP address to the terminal;
A name resolution method characterized by comprising: Receiving means for receiving a request for name resolution from a terminal including a URL corresponding to a system including a master main device and one or more slave main devices;
Name resolution means for selecting one master device from the master master device and one or more slave master devices according to a predetermined policy, and obtaining an IP address of the selected master device;
Transmitting means for returning the IP address to the terminal;
A program for causing a computer to function as a name resolution device.

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