Gateway system, gateway, telephone terminal, program, and method for building a telephone system

Abstract

Even without redundancy for the call control server, telephone services will be provided to telephones registered with the call control server even in the event of a failure in the call control server or the lines it serves. [Solution] A master gateway installed at a main base acquires address information of call control servers installed at sub-bases from slave gateways installed at the sub-bases and manages them. The master gateway also monitors the call control server installed at the main base, and if it detects an abnormality in the call control server or the line accommodated by the call control server, it sends a server registration request specifying the address information of the call control server installed at the sub-base to a telephone terminal installed at the main base, causing the telephone terminal to register with the call control server installed at the sub-base, and forwarding calls addressed to the telephone terminal to the call control server installed at the sub-base.

Description

[Technical Field]

[0001] The present invention relates to a technique for dealing with abnormalities in a call control server. [Background technology]

[0002] Call control server redundancy is known as a countermeasure technology for dealing with abnormalities in call control servers. In call control server redundancy, a standby call control server is prepared in addition to an active call control server, and is synchronized with the active call control server. In the event of an abnormality in the active call control server, the active call control server is switched to the standby call control server, and the call control that had been performed by the active call control server is taken over by the standby call control server (for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2013-110668 Summary of the Invention [Problem to be solved by the invention]

[0004] However, in order to implement call control server redundancy, it is necessary to prepare a backup call control server in addition to the active call control server and synchronize it with the active call control server. This increases the implementation and operation costs. Furthermore, if there is no problem with the call control server itself but an abnormality occurs in the line that this call control server accommodates, the call control server redundancy cannot be used to address the problem.

[0005] The present invention has been made in consideration of the above circumstances, and its purpose is to provide a technology that can provide telephone services to telephones registered with a call control server even when an abnormality occurs in the call control server or the line that the call control server accommodates, without making the call control server redundant. [Means for solving the problem]

[0006] In order to solve the above problems, the present invention relates to a gateway system that connects bases where a call control server that performs call control in cooperation with telephone terminals and telephone terminals registered therein is installed, and is configured with a master gateway installed at a main base, which is a specified base, and a slave gateway installed at a sub-base, which is a base other than the main base.

[0007] The master gateway manages the address information of the telephone terminals and call control servers installed at the main base, and also acquires and manages address information of the call control servers installed at the sub-bases from the slave gateway. Furthermore, the master gateway monitors the call control server installed at the main base, and if it detects an abnormality in this call control server or the line accommodated by this call control server, it sends a server registration request specifying the address information of the call control server installed at the sub-base to the telephone terminal installed at the main base, causing this telephone terminal to be registered with the call control server installed at the sub-base, and forwarding calls addressed to this telephone terminal to the call control server installed at the sub-base.

[0008] Alternatively, the master gateway manages the address information of the call control server installed at the main base, and acquires and manages address information of the telephone terminals and call control servers installed at the sub-bases from the slave gateway. Furthermore, by monitoring the call control server installed at the sub-base, if an abnormality is detected in the call control server or the line accommodated by the call control server, the master gateway sends a server registration request specifying the address information of the call control server installed at the main base to the telephone terminal installed at the sub-base, causing the telephone terminal to register with the call control server installed at the main base, and sends an incoming call forwarding request specifying the address information of the call control server installed at the main base to the slave gateway, causing calls addressed to the telephone terminal to be forwarded to the call control server installed at the main base.

[0009] For example, one aspect of the present invention is: A gateway system that connects between bases where a call control server that performs call control in cooperation with a telephone terminal and the telephone terminal registered in the gateway system is installed, a master gateway installed at a main base which is a predetermined base among the bases, and a slave gateway installed at a sub-base which is a base other than the main base among the bases, The master gateway an address information management means for managing address information of the telephone terminals and the call control server installed at the main base, and for acquiring address information of the call control server installed at the sub-base from the slave gateway and managing the address information; a monitoring means for monitoring the call control server installed at the main base; a server registration request means for transmitting a server registration request specifying address information of the call control server installed at the sub-base as a registration destination to the telephone terminal installed at the main base when the monitoring means detects an abnormality in the call control server installed at the main base or in a line accommodated by the call control server; and call transfer means for transferring, when the monitoring means detects an abnormality in the call control server installed at the main base or in the line accommodated by the call control server, a call that is destined for the telephone terminal to which the server registration request is sent by the server registration request means, to the call control server installed at the sub-base, The slave gateway The sub-base includes an address information notification unit that notifies the master gateway of address information of the call control server installed at the sub-base.

[0010] Another aspect of the present invention is A gateway system that connects between bases where a call control server that performs call control in cooperation with a telephone terminal and the telephone terminal registered in the gateway system is installed, a master gateway installed at a main base which is a predetermined base among the bases, and a slave gateway installed at a sub-base which is a base other than the main base among the bases, The master gateway an address information management means for managing address information of the call control server installed at the main base, and for acquiring address information of the telephone terminals and the call control server installed at the sub-bases from the slave gateway and managing the address information; Monitoring means for monitoring the call control server installed at the sub-site, a server registration request means for transmitting a server registration request specifying address information of the call control server installed at the main base as a registration destination to the telephone terminal installed at the sub-base when the monitoring means detects an abnormality in the call control server installed at the sub-base or in a line accommodated by the call control server; and an incoming call transfer request means for transmitting an incoming call transfer request accompanied by designation of address information of the call control server installed at the main base to the slave gateway when the monitoring means detects an abnormality in the call control server installed at the sub-base or in a line accommodated by the call control server, The slave gateway an address information notifying means for notifying the master gateway of address information of the telephone terminal and the call control server installed at the sub-base; and an incoming call forwarding means, which is installed at the sub-base and forwards calls addressed to the telephone terminal to which the server registration request was sent, to a call control server installed at the main base in accordance with the incoming call forwarding request received from the master gateway. [Effects of the Invention]

[0011] In the present invention, the master gateway monitors the call control server installed at the main base, and if it detects an abnormality in this call control server or in the lines accommodated by this call control server, it registers the telephone terminal installed at the main base with the call control server installed at the sub-base and transfers calls addressed to this telephone terminal to the call control server installed at the sub-base. Alternatively, if it monitors the call control server installed at the sub-base and detects an abnormality in this call control server or in the lines accommodated by this call control server, it registers the telephone terminal installed at the sub-base with the call control server installed at the main base and causes the slave gateway to transfer calls addressed to this telephone terminal to the call control server installed at the main base.

[0012] Therefore, according to the present invention, even if the call control server is not made redundant, telephone services can be continuously provided to telephones registered with this call control server in the event of an abnormality in the call control server or the line accommodated by the call control server. [Brief explanation of the drawings]

[0013] [Figure 1] Figure 1 is a schematic diagram of a communication system according to one embodiment of the present invention. [Figure 2] Figure 2 is a sequence diagram illustrating a first example of operation of a communication system according to one embodiment of the present invention. [Figure 3] Figure 3 is a sequence diagram illustrating a first example of operation of a communication system according to one embodiment of the present invention, and is a continuation of Figure 2. [Figure 4] Figure 4 is a sequence diagram illustrating a first example of operation of a communication system according to one embodiment of the present invention, and is a continuation of Figure 3. [Figure 5] Figure 5 is a sequence diagram illustrating a second example of operation of a communication system according to one embodiment of the present invention. [Figure 6] Figure 6 is a sequence diagram illustrating a second example of operation of a communication system according to one embodiment of the present invention, and is a continuation of Figure 5. [Figure 7] FIG. 7 is a sequence diagram illustrating a second operation example of the communication system according to an embodiment of the present invention, which is a continuation of FIG. [Figure 8] FIG. 8 is a schematic functional configuration diagram of the master gateway 2a. [Figure 9] FIG. 9 is a flow diagram for explaining the server information management process of the master gateway 2a. [Figure 10] FIG. 10 is a flow diagram for explaining the server status monitoring process of the master gateway 2a. [Figure 11] Figure 11(A) is a flowchart illustrating the main base server change process S213 shown in Figure 10, and Figure 11(B) is a flowchart illustrating the main base server recovery process S215 shown in Figure 10. [Figure 12] Figure 12(A) is a flowchart illustrating the sub-site server change process S218 shown in Figure 10, and Figure 12(B) is a flowchart illustrating the sub-site server recovery process S220 shown in Figure 10. [Figure 13] FIG. 13 is a schematic functional configuration diagram of the slave gateway 2b. [Figure 14] FIG. 14 is a flow diagram for explaining the operation of the slave gateway 2b. [Figure 15] FIG. 15 is a diagram showing a schematic functional configuration of the SIP phone 4. As shown in FIG. [Figure 16] FIG. 16 is a flow diagram for explaining the operation of the SIP phone 4. DETAILED DESCRIPTION OF THE INVENTION

[0014] An embodiment of the present invention will now be described.

[0015] FIG. 1 is a schematic diagram of a communication system according to this embodiment.

[0016] As shown in the figure, the communication system of this embodiment is configured to include a gateway system 1 that connects a main base and a sub-base via an IP network 6, and telephone systems 3a and 3b that are constructed at the main base and the sub-base, respectively.

[0017] The gateway system 1 has a master gateway (GW) 2a that connects to a telephone system 3a established at a main base via a LAN (Local Area Network) 8a, and a slave gateway (GW) 2b that connects to a telephone system 3b established at a sub-base via the LAN 8b (hereinafter, the master gateway 2a and slave gateway 2b are also simply referred to as gateways 2). The master gateway 2a and slave gateway 2b are connected via an IP network 6 via a VPN (Virtual Private Network), thereby interconnecting the telephone system 3a established at the main base and the telephone system 3b established at the sub-base.

[0018] The telephone systems 3a and 3b each have Session Initiation Protocol (SIP) phones 4a and 4b (hereinafter simply referred to as SIP phones 4) and SIP servers 5a and 5b (hereinafter simply referred to as SIP servers 5) that perform call control in cooperation with one or more SIP phones 4 registered in the systems. Here, the SIP phone 4a is registered in the SIP server 5a, and the SIP phone 4b is registered in the SIP server 5b. As a result, the SIP phone 4a receives telephone services via the SIP server 5a, and the SIP phone 4b receives telephone services via the SIP server 5b.

[0019] 2 to 4 are sequence diagrams for explaining a first operation example of the communication system according to the present embodiment.

[0020] When a predetermined event occurs, such as the arrival of a periodic notification timing or the registration of a new SIP phone 4, the SIP server 5 notifies the gateway 2 at the same location as itself of server information including its own address information and the address information of the SIP phones 4 registered with it, and its own line allocation information (information indicating the line allocation to line buttons such as function keys of the SIP phones 4 registered with it) (S100, S101). The gateway 2 registers the received server information as the server information of the location to which it belongs (S102, S103).

[0021] Furthermore, when a predetermined event occurs, such as the arrival of a periodic request timing, the master gateway 2a transmits a server information request to the slave gateway 2b (S104). In response to this, the slave gateway 2b transmits its own registered server information (address information of the SIP server 5b and SIP phone 4b, and line allocation information of the SIP server 5b) to the master gateway 2a (S105), and the master gateway 2a registers this server information as server information of the sub-site (S106).

[0022] The master gateway 2a also periodically sends a status request to the SIP server 5a based on the server information of the main base registered in itself (S107), and receives a status response in return from the SIP server 5a (S108), thereby monitoring the status of the SIP server 5a. Similarly, the master gateway 2a periodically sends a status request to the SIP server 5b based on the server information of the sub-base registered in itself (S109), and receives a status response in return from the SIP server 5b (S110), thereby monitoring the status of the SIP server 5b.

[0023] Now, let's assume that a failure has occurred in the SIP server 5a or the line to which the SIP server 5a is connected (S111). As described above, the master gateway 2a sends a status request to the SIP server 5a when the periodic request timing arrives (S112). In response, the SIP server 5a either does not send a status response or sends a status response indicating a failure. As a result, the master gateway 2a can detect the failure of the SIP server 5a at the main site.

[0024] When the master gateway 2a detects a failure in the SIP server 5a at the main site (S113), it confirms that the SIP server 5b at the sub-site is operating normally and sends a server registration request to the SIP phone 4a at the main site, which is registered in the server information of the main site, specifying the SIP server 5b at the sub-site (S114). In response, the SIP phone 4a sends a registration request to the SIP server 5b at the sub-site (S115). Then, the SIP server 5b registers the SIP phone 4a as a call control target (S116).

[0025] Furthermore, the master gateway 2a configures incoming call forwarding of calls originating from the SIP phone 4a at the main site to the SIP server 5b at the sub-site (S117). In addition, the master gateway 2a transmits the line assignment information of the SIP server 5b, which is included in the server information of the sub-site registered with it, to the SIP phone 4a at the main site (S118). In response, the SIP phone 4a configures the line assignment to its own line button according to the line assignment information of the SIP server 5b (S119).

[0026] Here, assume that telephone 7 on IP network 6 makes a call destined for SIP phone 4a (S120). When this call arrives at master gateway 2a via IP network 6, master gateway 2a confirms that this call is destined for SIP phone 4a and forwards the call to SIP server 5b at the sub-site (S121). When SIP server 5b receives a call from master gateway 2a (S122), it confirms that the destination of this call is SIP phone 4a, which is registered with it as a call control target, and sends the call to SIP phone 4a (S123).

[0027] Next, SIP phone 4a rings to notify the user of an incoming call from SIP server 5b (S124), and upon receiving an answer from the user (S125), sends a connection response to SIP server 5b (S126). SIP server 5b receives this connection response and sends it to telephone 7, the originator of the call (S127). This establishes a communication path between SIP phone 4a and telephone 7, enabling communication between the two (S128).

[0028] Next, assume that the SIP server 5a has recovered from its failure after the call between SIP phone 4a and telephone 7 has ended and the call path between them has been released (S129). As described above, the master gateway 2a sends a status request to SIP server 5a when the periodic request timing arrives (S130). In response, SIP server 5a, which has recovered from its failure, replies with a status response (S131). This allows the master gateway 2a to detect that the SIP server 5a at the main site has recovered from its failure.

[0029] When the master gateway 2a detects that the SIP server 5a at the main base has recovered from a failure (S132), it sends a server release request specifying the SIP server 5b specified in the server registration request to the SIP phone 4a that was the destination of the server registration request sent when the failure was detected (S133). In response to this, the SIP phone 4a sends a release request to the SIP server 5b at the sub-base (S134). The SIP server 5b then releases the SIP phone 4a from its call control targets (S135).

[0030] The master gateway 2a also cancels the call forwarding to the SIP server 5b of the sub-site for calls addressed to the SIP phone 4a of the main site (S136). Furthermore, the master gateway 2a transmits the line allocation information of the SIP server 5a contained in the server information of the main site registered with the master gateway 2a to the SIP phone 4a of the main site (S137). In response to this, the SIP phone 4a sets line allocation to its own line button in accordance with the line allocation information of the SIP server 5a (S138).

[0031] Let us now assume that one of the telephones 7 on the IP network 6 has made a call addressed to the SIP phone 4a (S139). When this call arrives at the master gateway 2a via the IP network 6, the master gateway 2a sends the received call to the SIP server 5a at the main base. The SIP server 5a confirms that the destination of this call is the SIP phone 4a registered in itself as a call control target, and sends the call to the SIP phone 4a (S140).

[0032] Next, the SIP phone 4a rings to notify the user of the incoming call from the SIP server 5a (S141), and upon receiving a response from the user (S142), sends a connection response to the SIP server 5a (S143). The SIP server 5a receives this connection response and sends it to the telephone 7, the originator of the call (S144). This establishes a communication path between the SIP phone 4a and the telephone 7, enabling communication between them (S145).

[0033] 5 to 7 are sequence diagrams for explaining a second operation example of the communication system according to the present embodiment.

[0034] When a predetermined event occurs, such as the arrival of a periodic notification timing or the registration of a new SIP phone 4, SIP server 5 notifies gateway 2 at the same location as itself of server information, including its own address information, the address information of SIP phones 4 registered with it, and its own line assignment information (S150, S151). Gateway 2 registers the received server information as the server information of the location to which it belongs (S152, S153).

[0035] Furthermore, when a predetermined event occurs, such as the arrival of a periodic request timing, the master gateway 2a sends a server information request to the slave gateway 2b (S154). In response, the slave gateway 2b sends the server information registered to it (address information of SIP server 5b and SIP phone 4b, and line assignment information of SIP server 5b) to the master gateway 2a (S155), and the master gateway 2a registers this server information as the server information of the sub-site (S156).

[0036] Furthermore, the master gateway 2a monitors the status of SIP server 5a by periodically sending status requests to SIP server 5a based on the server information of the main site registered with it (S157) and receiving status responses from SIP server 5a in return (S158). Similarly, the master gateway 2a monitors the status of SIP server 5b by periodically sending status requests to SIP server 5b based on the server information of the sub-site registered with it (S159) and receiving status responses from SIP server 5b in return (S160).

[0037] Now, let us assume that a failure has occurred in the SIP server 5b or in the line accommodated by the SIP server 5b (S161). As described above, the master gateway 2a transmits a status request to the SIP server 5b at the arrival of a periodic request timing (S162). In response, the SIP server 5b either does not return a status response or returns a status response indicating a failure. This allows the master gateway 2a to detect the failure of the SIP server 5b at the sub-site.

[0038] When the master gateway 2a detects a failure in the SIP server 5b of the sub-site (S163), it confirms that the SIP server 5a of the main-site is operating normally and transmits a server registration request specifying the SIP server 5a of the main-site to the SIP phone 4b of the sub-site, which is registered in the server information of the sub-site (S164). In response to this, the SIP phone 4b transmits a registration request to the SIP server 5a of the main-site (S165). The SIP server 5a then registers the SIP phone 4b as a call control target (S166).

[0039] The master gateway 2a also sends an incoming call forwarding request to the slave gateway 2b to forward calls addressed to the SIP phone 4b at the sub-site to the SIP server 5a at the main site (S167). In response to this, the slave gateway 2b sets up incoming call forwarding to the SIP server 5a at the main site for calls addressed to the SIP phone 4b at the sub-site (S168). Furthermore, the master gateway 2a sends the line allocation information of the SIP server 5a included in the server information of the main site registered with the master gateway 2a to the SIP phone 4b at the sub-site (S169). In response to this, the SIP phone 4b sets up line allocation for its own line button in accordance with the line allocation information of the SIP server 5a (S170).

[0040] Here, it is assumed that one of the telephones 7 on the IP network 6 originates a call addressed to the SIP phone 4b (S171). When this call arrives at the slave gateway 2b via the IP network 6, the slave gateway 2b confirms that the call is addressed to the SIP phone 4b and transfers the call to the SIP server 5a at the main base (S172). When the SIP server 5a receives a call from the slave gateway 2b (S173), it confirms that the call is addressed to the SIP phone 4b, which is registered in the SIP server 5a as a call control target, and sends the call to the SIP phone 4b (S174).

[0041] Next, the SIP phone 4b rings to notify the user of the incoming call from the SIP server 5a (S175), and upon receiving a response from the user (S176), sends a connection response to the SIP server 5a (S177). The SIP server 5a receives this connection response and sends it to the telephone set 7 that originated the call (S178). This establishes a communication path between the SIP phone 4b and the telephone set 7, enabling communication between them (S179).

[0042] Next, it is assumed that the SIP server 5b has recovered from the failure after the call between the SIP phone 4b and the telephone set 7 has ended and the call path between them has been released (S180). As described above, the master gateway 2a sends a status request to the SIP server 5b at the arrival of a periodic request timing (S181). In response, the SIP server 5b, which has recovered from the failure, replies with a status response (S182). This allows the master gateway 2a to detect that the SIP server 5b at the sub-site has recovered from the failure.

[0043] Next, when the master gateway 2a detects that the SIP server 5b at the sub-site has recovered from the failure (S183), it sends a server release request to the SIP phone 4b, which was the destination of the server registration request sent when the failure was detected, specifying the SIP server 5a that was specified in the server registration request (S184). In response, the SIP phone 4b sends a release request to the SIP server 5a at the main site (S185). Then, the SIP server 5a releases the SIP phone 4b from its call control target (S186).

[0044] Furthermore, the master gateway 2a sends a call forwarding cancellation request to the slave gateway 2b to cancel the call forwarding of calls originating from the SIP phone 4b at the sub-site to the SIP server 5a at the main site (S187). In response, the slave gateway 2b cancels the call forwarding of calls originating from the SIP phone 4a at the sub-site to the SIP server 5a at the main site (S188). In addition, the master gateway 2a sends the line assignment information of the SIP server 5b, which is included in the server information of the sub-site registered with it, to the SIP phone 4b at the sub-site (S189). In response, the SIP phone 4b sets the line assignment to its line button according to the line assignment information of the SIP server 5b (S190).

[0045] Here, assume that one of the telephones 7 on the IP network 6 makes a call destined for SIP phone 4b (S191). When this call arrives at the slave gateway 2b via the IP network 6, the slave gateway 2b sends the incoming call to the SIP server 5b at the sub-site. The SIP server 5b confirms that the destination of this call is SIP phone 4b, which is registered with it as a call control target, and sends the call to SIP phone 4b (S192).

[0046] Next, the SIP phone 4b rings to notify the user of the incoming call from the SIP server 5b (S193), and upon receiving a response from the user (S194), sends a connection response to the SIP server 5b (S195). The SIP server 5b receives this connection response and sends it to the telephone 7, the originator of the call (S196). This establishes a communication path between the SIP phone 4b and the telephone 7, enabling communication between them (S197).

[0047] Next, we will explain in detail the master gateway 2a, the slave gateway 2b, and the SIP phone 4 that make up the communication system according to this embodiment. Note that the SIP server 5 can be an existing SIP server that has a function of notifying the gateway 2 of server information, so detailed explanations thereof will be omitted.

[0048] First, the master gateway 2a will be described in detail.

[0049] FIG. 8 is a schematic functional configuration diagram of the master gateway 2a.

[0050] As shown in the figure, the master gateway 2a is configured to include a LAN interface unit 200, an IP network interface unit 201, a VPN connection unit 202, a relay unit 203, a server information storage unit 204, a server information request unit 205, a server monitoring unit 206, a server registration request unit 207, an incoming call forwarding unit 208, an incoming call forwarding request unit 209, and a line allocation information notification unit 210.

[0051] The LAN interface unit 200 is an interface for connecting to LAN8a, and the IP network interface unit 201 is an interface for connecting to IP network 6.

[0052] The VPN connection unit 202 establishes a VPN connection with the slave gateway 2 b via the IP network interface unit 201 .

[0053] The relay unit 203 relays between the LAN 8 a and the IP network 6 via the LAN interface unit 200 and the IP network interface unit 201 .

[0054] The server information storage unit 204 stores server information of the main base (address information of the SIP server 5a, SIP phone 4a, line allocation information of the SIP server 5a) and server information of the sub-base (address information of the SIP server 5b, SIP phone 4b, line allocation information of the SIP server 5b).

[0055] When a predetermined server information request timing comes, such as a regular timing, the server information request unit 205 transmits a server information request to the slave gateway 2b and acquires the server information of the sub-base from the slave gateway 2b.

[0056] The server monitoring unit 206 periodically sends a status request to the SIP server 5a based on the server information of the main base stored in the server information storage unit 204, and receives a status response in return from the SIP server 5a, thereby monitoring the status of the SIP server 5a. Similarly, the server monitoring unit 206 periodically sends a status request to the SIP server 5b based on the server information of the sub-base stored in the server information storage unit 204, and receives a status response in return from the SIP server 5b, thereby monitoring the status of the SIP server 5b.

[0057] When the server monitoring unit 206 detects a failure of the SIP server 5, the server registration request unit 207 transmits a server registration request specifying another SIP server 5 to the SIP phone 4 at the same base as this SIP server 5. Also, when the server monitoring unit 206 detects recovery from the failure of the SIP server 5, the server registration request unit 207 transmits a server cancellation request to the SIP phone 4 at the same base as this SIP server 5, specifying another SIP server 5 specified in the server registration request transmitted to this SIP phone 4.

[0058] The call forwarding unit 208 sets up call forwarding to the SIP server 5b of the sub-base for calls addressed to the SIP phone 4a of the main base when the server monitoring unit 206 detects a failure in the SIP server 5a of the main base. Also, when the server monitoring unit 206 detects recovery from the failure in the SIP server 5a of the main base, the call forwarding unit 208 cancels call forwarding to the SIP server 5b of the sub-base for calls addressed to the SIP phone 4a of the main base.

[0059] When the server monitoring unit 206 detects a failure in the SIP server 5b of the sub-base, the call transfer request unit 209 sends to the slave gateway 2b a call transfer request to transfer calls addressed to the SIP phone 4b of the sub-base to the SIP server 5a of the main base. Also, when the server monitoring unit 206 detects recovery from the failure in the SIP server 5b of the sub-base, the call transfer request unit 209 sends to the slave gateway 2b a call transfer cancellation request to cancel the call transfer of calls addressed to the SIP phone 4b of the sub-base to the SIP server 5a of the main base.

[0060] When the server monitoring unit 206 detects a failure of a SIP server 5, the line allocation information notification unit 210 transmits the line allocation information of other SIP servers 5 stored in the server information storage unit 204 to the SIP phone 4 at the same location as this SIP server 5. Also, when the server monitoring unit 206 detects recovery from the failure of the SIP server 5, the line allocation information of this SIP server 5 stored in the server information storage unit 204 is transmitted to the SIP phone 4 at the same location as this SIP server 5.

[0061] The functional configuration of the master gateway 2a shown in Fig. 8 is realized in hardware using an integrated logic IC such as an ASIC (Application Specific Integrated Circuit) or FPGA (Field Programmable Gate Array), or in software using a computer such as a DSP (Digital Signal Processor). Alternatively, it is realized as a process in a general-purpose computer such as a PC (Personal Computer) equipped with a CPU (Central Processing Unit), memory, an auxiliary storage device such as an SSD (Solid State Drive) or HDD (Hard Disk Drive), and a communication device such as a NIC (Network Interface Card), by the CPU loading a predetermined program from the auxiliary storage device into the memory and executing it.

[0062] FIG. 9 is a flow diagram for explaining the server information management process of the master gateway 2a.

[0063] When the server information storage unit 204 receives server information from the SIP server 5a of the main base via the LAN interface unit 200 (YES in S200), it stores and updates this server information as server information of the main base (S201).

[0064] Furthermore, when a predetermined server information request timing arrives (YES in S202), the server information request unit 205 transmits a server information request to the slave gateway 2b via the IP network interface unit 201 and acquires server information from the slave gateway 2b (S203). The acquired server information is then passed to the server information storage unit 204. In response to this, the server information storage unit 204 stores and updates the server information received from the server information request unit 205 as server information of the sub-base (S204).

[0065] FIG. 10 is a flow diagram for explaining the server status monitoring process of the master gateway 2a.

[0066] First, the server monitoring unit 206 starts monitoring the status of SIP servers 5a and 5b based on the server information for the main site and sub-sites stored in the server information storage unit 204 (S210). Specifically, the server monitoring unit 206 periodically sends a status request to SIP server 5a at the main site and monitors the status of SIP server 5a based on whether or not a status response is received or the content of the received status response. Similarly, the server monitoring unit 206 periodically sends a status request to SIP server 5b at the sub-site and monitors the status of SIP server 5b based on whether or not a status response is received or the content of the received status response.

[0067] Next, the server monitoring unit 206 determines that a failure has occurred in SIP server 5a if it has not received a status response from SIP server 5a as a reply to a status request sent to SIP server 5a at the main site after a predetermined time has elapsed, or if the received status response indicates a line abnormality (YES in S211). If SIP server 5b at the sub-site is operating normally (the status response received as a reply to the latest status request sent to SIP server 5b indicates that it is operating normally) (YES in S212), it performs the main site server change process described later (S213).

[0068] Subsequently, if the latest status response received as a reply to the status request sent to the SIP server 5a at the main site indicates that it is operating normally, the server monitoring unit 206 determines that the SIP server 5a has recovered from the failure (YES in S214) and performs the main site server recovery process described below (S215).

[0069] Furthermore, if a timeout occurs after a predetermined time has elapsed without receiving a status response from the SIP server 5a in response to the status request sent to the SIP server 5b at the sub-base, or if the received status response indicates a line abnormality, the server monitoring unit 206 determines that a failure has occurred in the SIP server 5b (YES in S216), and if the SIP server 5a at the main base is operating normally (the status response received in response to the latest status request sent to the SIP server 5a indicates that it is operating normally) (YES in S217), the server monitoring unit 206 performs the sub-base server change process described below (S218).

[0070] Subsequently, if the status response received as a reply to the latest status request sent to the SIP server 5b at the sub-site indicates that it is operating normally, the server monitoring unit 206 determines that the SIP server 5b has recovered from the failure (YES in S219) and performs the sub-site server recovery process described later (S220).

[0071] Figure 11(A) is a flowchart illustrating the main base server change process S213 shown in Figure 10.

[0072] The server monitoring unit 206 reads address information for the SIP phone 4a at the main base from the server information for the main base stored in the server information storage unit 204, and also reads address information for the SIP server 5b at the sub-base from the server information for the sub-base stored in the server information storage unit 204. Then, the server monitoring unit 206 passes this information to the server registration request unit 207 to instruct server registration. In response to this, the server registration request unit 207 transmits a server registration request including the address information for the SIP server 5b at the sub-base as the registration destination to the SIP phone 4a at the main base via the LAN interface unit 200 (S2130).

[0073] The server monitor unit 206 also instructs the call forwarding unit 208 to set up call forwarding by passing the address information of the SIP phone 4a at the main base and the address information of the SIP server 5b at the sub-base read in S2130. In response to this, the call forwarding unit 208 sets up call forwarding to the SIP server 5b at the sub-base for calls addressed to the SIP phone 4a at the main base (S2131).

[0074] The server monitor 206 also reads out the line allocation information of the SIP server 5b at the sub-base from the server information of the sub-base stored in the server information storage unit 204, and passes the line allocation information of the SIP server 5b together with the address information of the SIP phone 4a at the main base read out in S2130 to the line allocation information notification unit 210. In response to this, the line allocation information notification unit 210 transmits the line allocation information of the SIP server 5b to the SIP phone 4a at the main base via the LAN interface unit 200 (S2132).

[0075] Figure 11(B) is a flowchart illustrating the main base server recovery process S215 shown in Figure 10.

[0076] The server monitoring unit 206 reads address information for the SIP phone 4a at the main base from the server information for the main base stored in the server information storage unit 204, and also reads address information for the SIP server 5b at the sub-base from the server information for the sub-base stored in the server information storage unit 204. Then, the server monitoring unit 206 passes this information to the server registration request unit 207 to instruct server cancellation. In response to this, the server registration request unit 207 transmits a server cancellation request, including address information for the SIP server 5b at the sub-base as the cancellation destination, to the SIP phone 4a at the main base via the LAN interface unit 200 (S2150).

[0077] The server monitor 206 also passes the address information of the SIP phone 4a at the main base and the address information of the SIP server 5b at the sub-base read in S2150 to the call forwarding unit 208, instructing it to cancel the call forwarding setting. In response to this, the call forwarding unit 208 cancels the call forwarding setting to the SIP server 5b at the sub-base for calls addressed to the SIP phone 4a at the main base (S2151).

[0078] The server monitor 206 also reads out line allocation information for the SIP server 5a at the main base from the server information for the main base stored in the server information storage unit 204, and passes the line allocation information for the SIP server 5a together with the address information for the SIP phone 4a at the main base read out in S2150 to the line allocation information notification unit 210. In response to this, the line allocation information notification unit 210 transmits the line allocation information for the SIP server 5a to the SIP phone 4a at the main base via the LAN interface unit 200 (S2152).

[0079] FIG. 12A is a flow diagram for explaining the sub-base server change processing S218 shown in FIG.

[0080] The server monitoring unit 206 reads address information of the SIP server 5a at the main base from the server information of the main base stored in the server information storage unit 204, and also reads address information of the SIP phone 4b at the sub-base from the server information of the sub-base stored in the server information storage unit 204. Then, the server monitoring unit 206 passes this information to the server registration request unit 207 to instruct server registration. In response to this, the server registration request unit 207 transmits a server registration request including the address information of the SIP server 5a at the main base as the registration destination to the SIP phone 4b at the sub-base via the IP network interface unit 201 (S2180).

[0081] Furthermore, the server monitoring unit 206 passes the address information of the SIP server 5a at the main site and the address information of the SIP phone 4b at the sub-site, which were read in S2180, to the call forwarding request unit 209 and instructs it to send a call forwarding request. In response, the call forwarding request unit 209 sends a call forwarding request to the slave gateway 2b via the IP network interface unit 201 to forward a call destined for the SIP phone 4b at the sub-site to the SIP server 5a at the main site (S2181).

[0082] Furthermore, the server monitoring unit 206 reads the line allocation information of the SIP server 5a at the main site from the server information of the main site stored in the server information storage unit 204, and passes the line allocation information of SIP server 5a, along with the address information of SIP phone 4b at the sub-site read in S2180, to the line allocation information notification unit 210. In response, the line allocation information notification unit 210 transmits the line allocation information of SIP server 5a to SIP phone 4b at the sub-site via the IP network interface unit 201 (S2182).

[0083] Figure 12(B) is a flowchart illustrating the sub-site server recovery process S220 shown in Figure 10.

[0084] The server monitoring unit 206 reads the address information of the main site's SIP server 5a from the server information of the main site stored in the server information storage unit 204, and also reads the address information of the sub-site's SIP phone 4b from the server information of the sub-site stored in the server information storage unit 204. Then, it passes this information to the server registration request unit 207 and instructs it to deregister the server. In response, the server registration request unit 207 sends a server deregistration request to the sub-site's SIP phone 4b via the IP network interface unit 201, including the address information of the main site's SIP server 5a as the deregistration destination (S2200).

[0085] Furthermore, the server monitoring unit 206 passes the address information of the SIP server 5a at the main site and the address information of the SIP phone 4b at the sub-site, which were read in S2200, to the call forwarding request unit 209 and instructs it to cancel the call forwarding setting. In response, the call forwarding request unit 209 sends a call forwarding cancellation request to the slave gateway 2b via the IP network interface unit 201 to cancel the call forwarding of calls destined for the SIP phone 4b at the sub-site to the SIP server 5a at the main site (S2201).

[0086] Furthermore, the server monitoring unit 206 reads the line allocation information of the SIP server 5b of the sub-site from the server information of the sub-site stored in the server information storage unit 204, and passes the line allocation information of SIP server 5b, along with the address information of SIP phone 4b of the sub-site read in S2200, to the line allocation information notification unit 210. In response, the line allocation information notification unit 210 transmits the line allocation information of SIP server 5b to SIP phone 4b of the sub-site via the IP network interface unit 201 (S2202).

[0087] Next, we will explain the details of slave gateway 2b.

[0088] FIG. 13 is a schematic functional configuration diagram of the slave gateway 2b.

[0089] As shown in the figure, the slave gateway 2b is configured to include a LAN interface unit 220, an IP network interface unit 221, a VPN connection unit 222, a relay unit 223, a server information storage unit 224, a server information transmission unit 225, and an incoming call forwarding unit 226.

[0090] The LAN interface unit 220 is an interface for connecting to the LAN 8b, and the IP network interface unit 221 is an interface for connecting to the IP network 6.

[0091] The VPN connection unit 222 establishes a VPN connection with the master gateway 2a via the IP network interface unit 221.

[0092] The relay unit 223 relays between the LAN 8 b and the IP network 6 via the LAN interface unit 220 and the IP network interface unit 221 .

[0093] The server information storage unit 224 stores the server information of the sub-base (address information of the SIP server 5b and the SIP phone 4b, and line allocation information of the SIP server 5b).

[0094] The server information transmitting unit 225 transmits the server information of the sub-base stored in the server information storage unit 224 to the master gateway 2a in response to a server information request received from the master gateway 2a.

[0095] The call forwarding unit 226 sets and cancels call forwarding in accordance with the call forwarding request and call forwarding cancellation request received from the master gateway 2a.

[0096] The functional configuration of the slave gateway 2b shown in Figure 13 is similar to that of the master gateway 2a shown in Figure 8, and can be implemented in hardware using integrated logic ICs such as ASICs and FPGAs, or in software using a computer such as a DSP. Alternatively, it can be implemented as a process in a general-purpose computer such as a PC, which is equipped with a CPU, memory, auxiliary storage devices such as SSDs and HDDs, and communication devices such as NICs, by having the CPU load a predetermined program from the auxiliary storage device into memory and execute it.

[0097] FIG. 14 is a flow diagram for explaining the operation of the slave gateway 2b.

[0098] When the server information storage unit 224 receives the server information from the SIP server 5b via the LAN interface unit 220 (YES in S300), it stores this server information as the server information of the SIP server 5b (S301).

[0099] Furthermore, when the server information transmission unit 225 receives a server information request from the master gateway 2a via the IP network interface unit 221 (YES in S302), it reads the server information of the SIP server 5b from the server information storage unit 224 and transmits it to the master gateway 2a (S303).

[0100] Furthermore, when the call forwarding unit 226 receives a call forwarding request from the master gateway 2a via the IP network interface unit 221 (YES in S304), it sets up call forwarding to the master gateway 2a for calls that arrive at the IP network interface unit 221 and are destined for the SIP phone 4b at the sub-site (S305) in accordance with this call forwarding request.

[0101] Furthermore, when the call forwarding unit 226 receives a call forwarding cancellation request from the master gateway 2a via the IP network interface unit 221 (YES in S306), it cancels the call forwarding setting to the master gateway 2a for calls that arrive at the IP network interface unit 221 and are destined for the SIP phone 4b at the sub-site in accordance with this call forwarding cancellation request (S307).

[0102] Next, we will explain the details of SIP Phone 4.

[0103] FIG. 15 is a diagram showing a schematic functional configuration of the SIP phone 4. As shown in FIG.

[0104] As shown in the figure, the SIP phone 4 comprises a LAN interface unit 400 , a man-machine interface unit 401 , a telephone function unit 402 , a registration request processing unit 403 , and a line allocation unit 404 .

[0105] The LAN interface unit 400 is an interface for connecting to LANs 8a and 8b.

[0106] The man-machine interface unit 401 is an interface for the user to use the telephone, and although not shown in the diagram, it includes a microphone and speaker for voice calls, a display panel for displaying various information to the user, and a group of operation buttons for receiving various operations from the user. Here, the group of operation buttons includes a group of line buttons 405 used for line acquisition.

[0107] The telephone function unit 402 is a processing unit that realizes the functions of a SIP phone 4. Although not shown in the diagram, it performs call control in accordance with SIP and in cooperation with the registered SIP server 5 to establish and release the call path with the other party. It also sends and receives call data with the other party via the established call path in accordance with RTP (Realtime Transport Protocol).

[0108] In response to the server registration request received from the gateway 2 , the registration request processor 403 sends a registration request to the SIP server 5 to register its own SIP phone 4 with the SIP server 5 .

[0109] The line allocation unit 404 assigns the lines of the SIP server 5 to be registered to the line button group 405 according to the line allocation information received from the gateway 2.

[0110] The functional configuration of SIP phone 4 shown in Figure 15, like the functional configuration of gateway 2 shown in Figures 8 and 13, can be implemented in hardware using integrated logic ICs such as ASICs and FPGAs, or in software using a computer such as a DSP. Alternatively, it can be implemented as a process in a general-purpose computer such as a PC or smartphone, which is equipped with a CPU, memory, auxiliary storage devices such as an SSD, and communication devices such as a NIC, by having the CPU load a predetermined program from the auxiliary storage device into memory and execute it.

[0111] FIG. 16 is a flow diagram for explaining the operation of the SIP phone 4.

[0112] When the registration request processing unit 403 receives a server registration request from the gateway 2 via the LAN interface unit 400 (YES in S400), it sends the registration request to the SIP server 5 specified as the registration destination in this server registration request via the LAN interface unit 400 (S401).

[0113] Furthermore, when the registration request processing unit 403 receives a server deregistration request from the gateway 2 via the LAN interface unit 400 (YES in S402), it sends the deregistration request via the LAN interface unit 400 to the SIP server 5 specified as the deregistration destination in the server deregistration request (S403).

[0114] Furthermore, when the line allocation unit 404 receives line allocation information from the gateway 2 via the LAN interface unit 400 (YES in S404), it allocates the accommodated lines of the SIP server 5 of the registration destination to the line button group 405 in accordance with this line allocation information (S405).

[0115] One embodiment of the present invention has been described above.

[0116] In this embodiment, the master gateway 2a monitors the SIP server 5a installed at the main base, and if it detects an abnormality in the SIP server 5a or the line accommodated by the SIP server 5a, it registers the SIP phone 4a installed at the main base with the SIP server 5b installed at the sub-base, and forwards calls addressed to this SIP phone 4a to the SIP server 5b installed at the sub-base.

[0117] In addition, the master gateway 2a monitors the SIP server 5b installed at the sub-site, and if it detects an abnormality in the SIP server 5b or the line accommodated by the SIP server 5b, it registers the SIP phone 4b installed at the sub-site with the SIP server 5a installed at the main site, and causes the slave gateway 2b to forward calls addressed to this SIP phone 4b to the SIP server 5a installed at the main site.

[0118] Therefore, according to this embodiment, even if the SIP server 5 is not made redundant, telephone services can be provided to the SIP phones 4 registered in this SIP server 5 even when an abnormality occurs in the SIP server 5 or the line that this SIP server 5 accommodates.

[0119] Furthermore, in this embodiment, if the master gateway 2a detects that the SIP server 5a installed at the main site or the line connected to the SIP server 5a has been resolved, it sends a server release request to the SIP phone 4a installed at the main site, specifying the address information of the SIP server 5b installed at the sub-site, and also cancels the forwarding of calls originating from the SIP phone 4a at the main site to the SIP server 5b installed at the sub-site.

[0120] Furthermore, if the master gateway 2a detects that the SIP server 5b installed at the sub-site or the line connected to the SIP server 5b has been resolved, it sends a server release request to the SIP phone 4b installed at the sub-site, specifying the address information of the SIP server 5a installed at the main site, and also sends a call forwarding release request to the slave gateway 2b, specifying the address information of the SIP server 5a installed at the main site. The slave gateway 2b then releases the call forwarding of calls originating from the SIP phone 4b installed at the sub-site to the SIP server 5a installed at the main site, in accordance with the call forwarding release request received from the master gateway 2a.

[0121] Therefore, according to this embodiment, if the SIP phone 4 resolves an issue with the SIP server 5 at the same location as itself or the line connected to this SIP server 5, it can switch the SIP server 5 it uses back from the SIP server 5 at another location to the SIP server 5 at the same location, thereby reducing unnecessary communication traffic between the main location and sub-locations.

[0122] Furthermore, in this embodiment, the master gateway 2a stores the line allocation information of the SIP server 5a installed at the main site, and also acquires and stores the line allocation information of the SIP server 5b installed at the sub-site from the slave gateway 2b. If an abnormality occurs in the SIP server 5a installed at the main site or in the lines connected to SIP server 5a, the master gateway 2a transmits the line allocation information of SIP server 5b installed at the sub-site to the SIP phone 4a installed at the main site. If an abnormality occurs in the SIP server 5b installed at the sub-site or in the lines connected to SIP server 5b, the master gateway 2a transmits the line allocation information of SIP server 5a installed at the main site to the SIP phone 4b installed at the sub-site. As a result, if a SIP phone 4 needs to receive telephone service using a SIP server 5 at another site due to an abnormality in the SIP server 5 at the same site as itself, it can accept line operations using the line allocation information of the SIP server 5 at the other site, thereby improving user convenience.

[0123] It should be noted that the present invention is not limited to the embodiments described above, and numerous modifications are possible within the scope of its essence.

[0124] For example, in the above embodiment, there may be multiple sub-sites. In this case, when the master gateway 2a detects an abnormality in the SIP server 5a of the main site or in the line accommodated by the SIP server 5a, it selects one of the SIP servers 5b of the sub-sites that is operating normally, registers the SIP phone 4a of the main site with the SIP server 5b of the selected sub-site, and forwards calls addressed to the SIP phone 4a to the SIP server 5b of the selected sub-site. Furthermore, when the master gateway 2a detects an abnormality in the SIP server 5b of one of the sub-sites or the line accommodated by this SIP server 5b, it selects a normally operating SIP server 5 of one of the sites from among the SIP servers 5b of the sub-sites other than the sub-site where the abnormality in the SIP server 5b etc. was detected and the SIP server 5a of the main site, and registers the SIP phone 4b of the sub-site where the abnormality in the SIP server 5b etc. was detected to this selected SIP server 5, and also causes the slave gateway 2b of the sub-site where the abnormality in the SIP server 5b etc. was detected to forward calls addressed to the SIP phone 4b of the same sub-site to this selected SIP server 5.

[0125] In the above embodiment, the telephone system 3 established at each base is configured to include a SIP phone 4 and a SIP server 5. However, the present invention is not limited to this. The present invention can be widely applied to cases where a telephone system is established at each base, including a call control server that executes call control in cooperation with registered telephone terminals, and telephone terminals that send registration requests to the call control server to register themselves with the call control server.

[0126] Furthermore, the above embodiment was described using the example of a case where the main site and sub-sites are connected by VPN via the gateway system 1. However, the present invention is not limited to this. The present invention only requires that the sites are connected via IP network 6 via the gateway system 1. [Explanation of symbols]

[0127] 1: Gateway system 2a: Master gateway 2b: Slave Gateway 3a, 3b: Telephone System 4, 4a, 4b: SIP phone 5, 5a, 5b: SIP server 6:IP network 7:Telephone 200, 220, 400: LAN interface section 201, 221: IP network interface section 202, 222: VPN connection section 203, 223: Relay section 204, 224: Server information storage unit 205: Server information request unit 206: Server monitoring unit 207: Server registration request unit 208, 226: Call forwarding unit 209: Call forwarding request unit 210: Line allocation information notification unit 225: Server information transmission unit 401: Man-machine interface unit 402: Telephone function unit 403: Registration request processing unit 404: Line allocation section 405: Line button group

Claims

1. A gateway system that connects between bases where a call control server that performs call control in cooperation with a telephone terminal and the telephone terminal registered in the gateway system is installed, a master gateway installed at a main base which is a predetermined base among the bases, and a slave gateway installed at a sub-base which is a base other than the main base among the bases, The master gateway an address information management means for managing address information of the telephone terminals and the call control server installed at the main base, and for acquiring address information of the call control server installed at the sub-base from the slave gateway and managing the address information; a monitoring means for monitoring the call control server installed at the main base; a server registration request means for transmitting a server registration request specifying address information of the call control server installed at the sub-base as a registration destination to the telephone terminal installed at the main base when the monitoring means detects an abnormality in the call control server installed at the main base or in a line accommodated by the call control server; and an incoming call forwarding means for forwarding, when the monitoring means detects an abnormality in the call control server installed at the main base or in the line accommodated by the call control server, an incoming call forwarding means for forwarding, to the call control server installed at the sub-base, a call addressed to the telephone terminal to which the server registration request has been sent by the server registration requesting means, the call control server installed at the sub-base, The slave gateway an address information notifying means for notifying the master gateway of address information of the call control server installed at the sub-base; A gateway system comprising:

2. 2. The gateway system of claim 1, The server registration request means When the monitoring means detects that the abnormality in the call control server installed at the main base or the line accommodated by the call control server has been resolved, a server deregistration request is sent to the telephone terminal installed at the main base, the server deregistration request specifying the address information of the call control server installed at the sub-base as the deregistration destination, The call forwarding means When the monitoring means detects that the abnormality in the call control server installed at the main base or the line accommodated by the call control server has been resolved, the call forwarding to the call control server installed at the sub-base of a call addressed to the telephone terminal installed at the main base and to which the server registration request means has sent the server cancellation request is cancelled. A gateway system comprising:

3. 3. The gateway system according to claim 1, The master gateway a line assignment information acquisition means for acquiring line assignment information indicating line assignments to line buttons of the telephone terminals by the call control server installed at the sub-base from the slave gateway; and a line assignment information notification means for notifying the telephone terminal installed at the main base of the line assignment information acquired by the line assignment information acquisition means when the monitoring means detects an abnormality in the call control server installed at the main base or in a line accommodated by the call control server, The slave gateway The system further includes a line assignment information transmitting means for transmitting the line assignment information of the call control server installed at the sub-base to the master gateway. A gateway system comprising:

4. A gateway system that connects between bases where a call control server that performs call control in cooperation with a telephone terminal and the telephone terminal registered in the gateway system is installed, a master gateway installed at a main base which is a predetermined base among the bases, and a slave gateway installed at a sub-base which is a base other than the main base among the bases, The master gateway an address information management means for managing address information of the call control server installed at the main base, and for acquiring address information of the telephone terminals and the call control server installed at the sub-bases from the slave gateway and managing the address information; a monitoring means for monitoring the call control server installed at the sub-base; a server registration request means for transmitting a server registration request specifying address information of the call control server installed at the main base as a registration destination to the telephone terminal installed at the sub-base when the monitoring means detects an abnormality in the call control server installed at the sub-base or in a line accommodated by the call control server; and an incoming call transfer request means for transmitting an incoming call transfer request accompanied by designation of address information of the call control server installed at the main base to the slave gateway when the monitoring means detects an abnormality in the call control server installed at the sub-base or in a line accommodated by the call control server, The slave gateway an address information notifying means for notifying the master gateway of address information of the telephone terminal and the call control server installed at the sub-base; and an incoming call forwarding means, which is installed at the sub-base and forwards a call addressed to the telephone terminal to which the server registration request has been sent, to a call control server installed at the main base in accordance with the incoming call forwarding request received from the master gateway. A gateway system comprising:

5. 5. The gateway system according to claim 4, The server registration request means When the monitoring means detects that the abnormality in the call control server installed at the sub-base or the line accommodated by the call control server has been resolved, a server deregistration request is sent to the telephone terminal installed at the sub-base, the server deregistration request specifying the address information of the call control server installed at the main base as the deregistration destination, The call transfer request means when the monitoring means detects that the abnormality in the call control server installed at the sub-base or the line accommodated by the call control server has been resolved, it transmits to the slave gateway a call forwarding cancellation request accompanied by designation of address information of the call control server installed at the main base, The call forwarding means Canceling the call forwarding to the call control server installed at the main base for calls addressed to the telephone terminal installed at the sub-base and to which the server cancellation request was sent, in accordance with the call forwarding cancellation request received from the master gateway. A gateway system comprising:

6. 6. The gateway system according to claim 4 or 5, The master gateway The system further comprises a line allocation information notification means for notifying the telephone terminal installed at the sub-base of line allocation information indicating line allocation to the line buttons of the telephone terminal by the call control server installed at the main base when the monitoring means detects an abnormality in the call control server installed at the sub-base or in the line accommodated by the call control server. A gateway system comprising:

7. A gateway is installed at a base where a call control server that performs call control in cooperation with a telephone terminal and the telephone terminal registered in the gateway is installed, and connects the base to another base where the telephone terminal and the call control server are installed, an address information management means for managing address information of the telephone terminals and the call control server installed at the base and for managing address information of the call control server installed at the other base; a monitoring means for monitoring the call control server installed at the base; a server registration request means for transmitting a server registration request to the telephone terminal installed at the base, when the monitoring means detects an abnormality in the call control server installed at the base or in a line accommodated by the call control server, the server registration request specifying address information of the call control server installed at the other base as a registration destination; and an incoming call forwarding means for forwarding, when the monitoring means detects an abnormality in the call control server installed at the base or in a line accommodated by the call control server, an incoming call forwarding means for forwarding, to the call control server installed at the other base, a call addressed to the telephone terminal to which the server registration request has been sent by the server registration requesting means. A gateway characterized by:

8. A gateway is installed at a base where a call control server that performs call control in cooperation with a telephone terminal and the telephone terminal registered in the gateway is installed, and connects the base to another base where the telephone terminal and the call control server are installed, an address information management means for managing address information of the call control server installed at the base and for managing address information of the telephone terminals and the call control servers installed at the other bases; a monitoring means for monitoring the call control server installed at the other site; a server registration request means for transmitting a server registration request specifying address information of the call control server installed at the other base as a registration destination to the telephone terminal installed at the other base when the monitoring means detects an abnormality in the call control server installed at the other base or in a line accommodated by the call control server; and an incoming call transfer request means for transmitting an incoming call transfer request accompanied by designation of address information of the call control server installed at the other base to another gateway installed at the other base when the monitoring means detects an abnormality in the call control server installed at the other base or in a line accommodated by the call control server. A gateway characterized by:

9. A telephone terminal that performs call control in cooperation with a call control server in which the telephone terminal is registered, a server registration request receiving means for receiving the server registration request from the gateway according to claim 7 or 8; a registration means for transmitting a registration request along with its own address information to the call control server designated in the server registration request received by the server registration request receiving means, and registering itself with the call control server. A telephone terminal characterized by:

10. A program that is installed at a base where a call control server that performs call control in cooperation with telephone terminals and the telephone terminals registered in the base is installed, and that causes a computer to function as a gateway that connects the base to other bases where the telephone terminals and the call control server are installed, an address information management means for managing address information of the telephone terminals and the call control server installed at the base and for managing address information of the call control server installed at the other base; a monitoring means for monitoring the call control server installed at the base; a server registration request means for transmitting, to the telephone terminal installed at the base, a server registration request specifying address information of the call control server installed at the other base as a registration destination when the monitoring means detects an abnormality in the call control server installed at the base or in a line accommodated by the call control server; When the monitoring means detects an abnormality in the call control server installed at the base or in the line accommodated by the call control server, the computer is made to function as an incoming call forwarding means for forwarding a call addressed to the telephone terminal installed at the base and which has transmitted the server registration request, to the call control server installed at the other base. A program characterized by:

11. A program that is installed at a base where a call control server that performs call control in cooperation with telephone terminals and the telephone terminals registered in the base is installed, and that causes a computer to function as a gateway that connects the base to other bases where the telephone terminals and the call control server are installed, an address information management means for managing address information of the call control server installed at the base and for managing address information of the telephone terminals and the call control servers installed at the other bases; a monitoring means for monitoring the call control server installed at the other site; a server registration request means for transmitting, to the telephone terminal installed at the other site, a server registration request specifying address information of the call control server installed at the site as a registration destination when the monitoring means detects an abnormality in the call control server installed at the other site or in a line accommodated by the call control server; When the monitoring means detects an abnormality in the call control server installed at the other base or in the line accommodated by the call control server, the computer is made to function as an incoming call transfer request means for transmitting an incoming call transfer request accompanied by designation of address information of the call control server installed at the other base to another gateway installed at the other base and to which the server registration request was transmitted. A program characterized by:

12. A program that causes a computer to function as a telephone terminal that performs call control in cooperation with a call control server in which the computer is registered, a server registration request receiving means for receiving the server registration request from the gateway according to claim 7 or 8; causing the computer to function as registration means for transmitting a registration request along with its own address information to the call control server designated in the server registration request received by the server registration request receiving means, and registering itself with the call control server; A program characterized by:

13. A method for constructing a telephone system using a gateway system that connects between bases where telephone terminals and call control servers that perform call control in cooperation with the telephone terminals registered in the gateway system are installed, comprising: The gateway system includes: a master gateway installed at a main base which is a predetermined base among the bases, and a slave gateway installed at a sub-base which is a base other than the main base among the bases, The master gateway managing address information of the telephone terminals and the call control server installed at the main base, acquiring address information of the call control server installed at the sub-base from the slave gateway and managing it, and monitoring the call control server installed at the main base; when an abnormality is detected in the call control server installed at the main base or in the line accommodated by the call control server, a server registration request accompanied by designation of address information of the call control server installed at the sub-base is transmitted to the telephone terminal installed at the main base, and call forwarding is set to the call control server installed at the sub-base for calls addressed to the telephone terminal to which the server registration request was transmitted; The slave gateway The master gateway is notified of address information of the call control server installed at the sub-site. A method for constructing a telephone system.

14. A method for constructing a telephone system using a gateway system that connects between bases where telephone terminals and call control servers that perform call control in cooperation with the telephone terminals registered in the gateway system are installed, comprising: The gateway system includes: a master gateway installed at a main base which is a predetermined base among the bases, and a slave gateway installed at a sub-base which is a base other than the main base among the bases, The master gateway managing address information of the call control server installed at the main base, acquiring address information of the telephone terminals and the call control server installed at the sub-bases from the slave gateway and managing the address information, and monitoring the call control server installed at the sub-bases; when an abnormality is detected in the call control server installed at the sub-base or in the line accommodated by the call control server, transmits a server registration request to the telephone terminal installed at the sub-base, which request specifies address information of the call control server installed at the main base, and transmits an incoming call transfer request to the slave gateway, which request specifies address information of the call control server installed at the main base; The slave gateway notifying the master gateway of address information of the telephone terminal and the call control server installed at the sub-base; When the call forwarding request is received from the master gateway, the call forwarding server sets up a call forwarding to the call control server installed at the main base for calls addressed to the telephone terminal installed at the sub-base and to which the server registration request was sent. A method for constructing a telephone system.

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