JP2005328354A - Ip telephone system and subscriber's router - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To surely prevent occurrence of third person's communication interruption through an IP telephone. <P>SOLUTION: In an IP telephone system provided with an IP network including a plurality of IP telephones to which IP addresses are respectively assigned to transmit/receive voices as IP packets and a plurality of subscriber's routers having a function for routing an IP packet and respectively connecting IP telephones to the IP network and one or more call control servers for controlling call connection, the call control server is provided with a means for informing a subscriber's router of the IP address of an IP telephone which becomes a communication party of IP telephone at the time of call connection and the subscriber's router is provided with a storage table for registering the informed IP address and a means for inspecting the IP address of the transmitting source of the IP packet received from the IP network side on the basis of the contents of the storage table and routing the IP packet to the IP telephone storing only the IP packet having the IP address registered in the storage table. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an IP telephone system and a subscriber router for transmitting voice information between IP units using IP packets.

  An IP telephone system includes an IP telephone terminal to which an IP address is assigned or an adapter for connecting the telephone terminal to an IP network (hereinafter, both are collectively referred to as an IP telephone terminal) and an IP packet routing function. It is composed of an IP network constituted by routers and a call control server that executes call connection control.

  Conventionally, the procedure for executing communication in the IP telephone system has been as follows (for example, Non-Patent Document 1, Non-Patent Document 2), where the source IP telephone terminal is the destination IP telephone terminal. When a call is made, the destination telephone number is transmitted to the call control server, and the call control server converts the destination telephone number to the destination IP address to make a call to the destination IP telephone terminal. Do. When the destination IP telephone terminal responds, the call control server performs call connection processing, and both IP telephone terminals acquire the IP address of the communication partner through these call connection procedures. A call after setting a call is made by designating the destination by the IP address of the communication partner directly acquired by the IP telephone terminals without using the call control server.

Nikkei Communication, August 11, 2003 issue, dissecting IP phones Nikkei Communication, December 8, 2003, Dissecting IP phones

  In the conventional IP telephone system, a direct communication is performed using the IP address of the communication partner during a call, and the IP router has an IP packet whose destination address is the IP address of the IP telephone terminal. Is sent to the IP telephone terminal. For this reason, when a malicious third party learns the user's IP address, the malicious third party can perform a denial-of-service attack such as a DOS attack, etc. There is sex. Note that it is possible to prevent an unauthorized packet from being sent to an IP telephone terminal by determining a code indicating a protocol higher than the IP layer in the IP packet, but the correct code is embedded in the IP packet. In such a case, it is not possible to prevent the user from interfering with communication by high-order protocol judgment.

  The present invention has been made in view of the above, and an object of the present invention is to obtain an IP telephone system and a subscriber router capable of preventing communication interference by a third party.

  In order to solve the above-described problems and achieve the object, the present invention has a function of routing a plurality of terminals to which IP addresses for transmitting and receiving voice as IP packets are assigned, and a function of routing the IP packets. An IP telephone system comprising an IP network including a plurality of subscriber routers connected to an IP network and one or more call control servers for controlling call connection, wherein the call control server communicates at the time of call connection Means for notifying a subscriber router that connects a terminal to be performed to an IP network of an IP address of a terminal that is a communication partner of the terminal accommodated by the subscriber router, wherein the subscriber router includes the call control server; A storage table for registering the IP address notified from the IP network, and an IP password received from the IP network side based on the registered contents of the storage table. It examines the source IP address of Tsu bets, characterized in that it comprises means for routing the terminals included only IP packets having a registered IP address to the IP storage table to the source address.

  According to the present invention, the subscriber router registers the IP address notified from the call control server at the time of call connection, and checks the transmission source IP address of the IP packet received from the IP network side based on the registered content, Routing to a terminal that accommodates only IP packets having the registered IP address as the source address.

  According to the present invention, the subscriber router registers the IP address notified from the call control server at the time of call connection, and checks the transmission source IP address of the IP packet received from the IP network side based on the registered content, Routing is performed to a terminal that accommodates only an IP packet having a registered IP address as a source address, and an IP packet having an unregistered source IP address is discarded without being transferred. Therefore, even if a third party tries to interfere with the communication performed by the terminal due to a denial of service attack such as a DOS attack, the IP packet from the third party is discarded by the subscriber router. Therefore, communication interference by a third party can be reliably prevented.

  Embodiments of an IP telephone system and a subscriber router according to the present invention will be described below in detail with reference to the drawings. Note that the present invention is not limited to the embodiments.

Embodiment 1 FIG.
A first embodiment of the present invention will be described with reference to FIGS. FIG. 1 shows the configuration of an IP telephone system according to Embodiment 1 of the present invention. This IP telephone system is an IP including a plurality of routers including a plurality of subscriber IP telephones (hereinafter abbreviated as IP telephones) 11 and 12 as terminals and subscriber routers (VoIP routers) 41 and 42 as edge routers. A network 31 and a call control server 21 are provided.

  The IP phones 11 and 12 have a function of transmitting and receiving voice as IP packets. The IP phones 11 and 12 are assigned IP addresses. The subscriber router 41 has a function of routing IP packets, and connects the accommodated IP telephone 11 to the IP network 31. The edge router 42 has a function of routing an IP packet, and connects the accommodated IP telephone 12 to the IP network 31. The call control server 21 performs call connection control. Note that a plurality of call control servers 21 may exist in the IP network 31 for purposes such as load balancing or when a plurality of communication providers provide services. The number of servers 21 is one. Reference numeral 51 denotes a third party IP terminal.

  FIG. 2 shows the stored contents of the IP storage tables 41a and 42a provided in the routers 41 and 42. FIG. The IP storage tables 41a and 42a are used by the routers 41 and 42 to determine whether or not to transfer IP packets from the IP network 31 side to the terminal side (user side) such as the IP telephones 11 and 12 accommodated in the routers 41 and 42. In the IP storage tables 41a and 42a, source IP addresses that permit the transfer of IP packets to the user side are registered. The registered transmission source IP address is transmitted from the call control server 21 as described later. Note that the IP address of the call control server 21 is registered in advance as a source IP address that permits transfer.

  Here, the routers 41 and 42 unconditionally transfer the IP packet from the user side to the IP network 31 side, but the IP packet from the IP network 31 side to the user side is received from the IP network 31. Even if the destination IP address of the IP packet is an IP phone accommodated by itself, if the source IP address of the IP packet is not registered in the IP storage tables 41a and 42a, the IP packet is transferred to the user side. Works to discard without.

  FIG. 3 shows a communication operation procedure according to the first embodiment when a connection request is made from IP phone 12 to IP phone 11. First, the IP phone 12 transmits a connection request IP packet (hereinafter simply referred to as a connection request) to the IP phone 11 to the call control server 21 in order to set a call to the IP phone 11. This connection request is, for example, one in which the IP address of the call control server 21 is set as the transmission destination address, and the IP address A2 of the IP phone 12 is set as the transmission source address. Identification information for identifying the destination (IP phone 11 in this case).

  The identification information includes a telephone number and an IP address. When the identification information is a telephone number, an IP address corresponding to the telephone number is registered in the call control server 21, and the call control server 21 converts the telephone number into an IP address using this registration data. . When the identification information is an IP address, the call control server 21 does not convert the telephone number into the IP address, and uses the identification information (IP address) indicating the connection request destination included in the connection request IP packet. The connection request is transmitted to the IP phone 11. In the above description, the IP address A2 of the IP telephone 12 is set as the transmission source address in the connection request IP packet. However, the telephone number of the IP telephone 12 that is the transmission source of the connection request in the connection request IP packet. Can be entered as transmission source information, and the call control server 21 can recognize the IP address of the transmission source IP telephone 12 of the connection request by converting the telephone number into an IP address.

  The connection request transmitted from the IP phone 12 is transferred to the call control server 21 by the router 42. The call control server 21 that has received the connection request from the IP phone 12 sends a connection request to the IP phone 11 using itself, that is, the IP address of the call control server 21 as the source address and the IP address of the IP phone 11 as the destination address. Forward. At this time, the call control server 21 may change the format of the connection request to be transferred to an optimum form in the system. The connection request transmitted by the call control server 21 is received by the router 41. The router 41 checks whether or not the source IP address of this connection request is registered in the IP storage table 41a. As described above, since the IP address of the call control server 21 is registered in advance in the IP storage table 41 a of the router 41, the connection request is transferred to the IP phone 11.

  The IP telephone 11 transmits a response to the connection request to the call control server 21 via the router 41. This response uses the IP address of the call control server 21 as the transmission destination address and the IP address of the IP telephone 11 as the transmission source address. Upon receiving this connection request response, the call control server 21 notifies the IP address A2 of the IP telephone 12 of the connection request transmission source to the router 41, which is a subscriber router on the connection request transmission side, and The IP address A1 of the destination IP telephone 11 of the connection request is notified to the router 42 which is a subscriber router on the transmission side. By receiving these IP address notifications, the IP address A2 of the IP phone 12 is registered in the IP storage table 41a of the router 41, and the IP address A1 of the IP phone 11 is registered in the IP storage table 42a of the router 42. FIG. 4 shows the registration contents of the IP storage table 41 a of the router 41.

  The call control server 21 notifies the routers 41 and 42 of these IP addresses, and then uses the IP address of the IP phone 12 as the source address, the IP address of the IP phone 12 as the destination address, and A response to the connection request including the IP address of IP phone 11 is transferred to IP phone 11. The response to the connection request is transmitted to the IP telephone 12 via the router 42, whereby the call connection is completed. After the call connection is completed, IP phone 11 and IP phone 12 make a direct call using each other's IP address. The address A2 of the IP phone 12 is registered in the IP storage table 41a of the router 41, and the address A1 of the IP phone 11 is registered in the IP storage table 42a of the router 42. The IP packet transmitted by is transferred to the communication partner via the router.

  After the call is completed, the IP telephones 11 and 12 transmit a call disconnection notification to the call control server 21. Upon receiving the call disconnection notification, the call control server 21 detects the completion of the call and sends the IP addresses A2 and A1 of the IP phone 12 and the IP phone 11 to the router 41 and the router 42 from the IP storage tables 41a and 42a, respectively. Perform call disconnect processing to be deleted.

  As described above, in the first embodiment, each of the subscriber routers 41 and 42 stores the source IP address that permits the transfer of the IP packet to the user side transmitted from the call control server 21 and receives it from the IP network 31. If the source IP address of the IP packet is not registered in the IP storage tables 41a and 42a, the IP packet is discarded without being transferred. Even if the third party who acquired the address uses the IP terminal 51 and tries to interfere with the communication performed by the IP telephones 11 and 12 due to a service denial attack such as a DOS attack, the IP transmitted by the third party IP terminal 51 Since the source IP address of the packet is not registered in the IP storage table of the routers 41 and 42 as shown in FIG. 42, as shown in FIG. 5, not transferred to the IP telephone 11, 12 the IP packet IP terminal 51 of the third party sends its own accommodated. For this reason, communication interference by a third party can be reliably prevented.

Embodiment 2. FIG.
Next, a second embodiment of the present invention will be described with reference to FIGS. FIG. 6 shows the configuration of the IP telephone system according to the second embodiment. 6, the same components as those in FIG. 1 are denoted by the same reference numerals as those in FIG. In the IP telephone system shown in FIG. 5, a personal computer 71 for performing user IP communication and a WEB server 81 connected to the IP network 31 are added.

  FIG. 7 shows the stored contents of the IP storage table 41 b built in the router 41. The IP storage table 42b built in the router 42 also has the same stored contents. In the first embodiment, only the transmission source address is registered in the IP storage table. However, in the second embodiment, the combination of the destination (transmission destination) IP address and the transmission source IP address is changed to the IP storage table 41b, Among IP packets from the IP network 31 to the user side, IP packets whose destination addresses match the destination IP addresses registered in the IP storage tables 41b and 42b are transmitted from the source IP. Only when the address is registered at the same time, the IP packet is routed to the user side. That is, in the rulers 41 and 42, among the IP packets from the IP network 31 to the user side, the IP packets whose destination addresses match the destination IP addresses registered in the IP storage tables 41b and 42b, and the IP packets An IP packet whose source address is not registered as a source IP address of a pair of destination IP addresses registered in the IP storage tables 41b and 42b is discarded.

  In the IP storage table 41 b of the router 41, the IP address of the call control server 21 is registered in advance in combination with an IP address such as the IP telephone 11 accommodated in the router 41. The IP address A1 of the IP phone 11 is registered as the destination IP address, and the IP address of the call control server 21 is registered as the transmission source IP address. In the IP storage table 42b of the router 42, a combination of these IP addresses is registered with the IP address of the call control server 21 as the source IP address and the IP address A2 of the IP telephone 12 as the destination IP address.

  FIG. 8 shows the operation procedure of communication in the second embodiment when a connection request is made from IP phone 12 to IP phone 11. The difference from the first embodiment is that the IP address notification from the call control server 21 to the router 41 and the router 42, the notification to the router 41 is the IP address of the IP telephone 11 and the source IP address is IP address. Similarly, the notification to the router 42 is that the destination IP address is the IP phone 12 and the transmission source IP address is the IP address 11 combination.

  First, as in the first embodiment, since the IP phone 12 sets a call to the IP phone 11, the IP address of the call control server 21 is set as the transmission destination address, and the IP address A2 of the IP phone 12 is set as the transmission source address. And a connection request including identification information such as the telephone number of the IP phone 11 for identifying the partner IP phone 11 of the connection request is transmitted to the call control server 21. The connection request transmitted from the IP phone 12 is transferred to the call control server 21 by the router 42. The call control server 21 that has received the connection request from the IP telephone 12 has an IP address corresponding to the telephone number registered in the call control server 21, and the call control server 21 uses the registration data for the IP telephone 11. The telephone number is converted into the IP address of the IP telephone 11.

  Then, the call control server 21 forwards a connection request with the IP address of the call control server 21 as the transmission source address and the IP address of the IP phone 11 as the transmission destination address to the IP phone 11. The connection request transmitted by the call control server 21 is received by the router 41. The router 41 checks whether or not the pair of the transmission source IP address and the transmission destination address included in the connection request is registered in the IP storage table 41a. As shown in FIG. 7, since the combination in which the IP address of the call control server 21 is the source address and the IP address of the IP telephone 11 is the destination address is registered in advance in the IP storage table 41a of the router 41, The connection request is transferred to the IP phone 11.

  The IP telephone 11 transmits a response to the connection request to the call control server 21 via the router 41. This response uses the IP address of the call control server 21 as the transmission destination address and the IP address of the IP telephone 11 as the transmission source address. Upon receiving this connection request response, the call control server 21 uses the IP address A1 of the IP telephone 11 accommodated by the router 41 as the destination IP address for the router 41, which is the subscriber router on the connection request transmission destination side, and receives the connection request. An IP address notification is executed with the IP address A2 of the original IP phone 12 as the source IP address. Also, the call control server 21 uses the IP address A2 of the IP telephone 12 accommodated in the router 42 as the destination IP address for the router 42 which is the subscriber router on the connection request transmission side, and is the other party of the connection request. An IP address notification is executed with the IP address A1 of the IP phone 11 as the source IP address.

  By receiving these IP address notifications, the IP storage table 41b of the router 41 transmits the IP address A1 of the IP phone 11 as the destination IP address and the IP address A2 of the IP phone 12 as shown in FIG. A combination of IP addresses as original IP addresses is registered. Similarly, the IP storage table 42b of the router 42 registers a combination of IP addresses in which the IP address A2 of the IP phone 12 is the destination IP address and the IP address A1 of the IP phone 11 is the source IP address.

  After making these IP address notifications, the call control server 21 sets its own IP address as the source address, the IP address of the IP phone 12 as the destination address, and the IP phone 11 A response to the connection request including the IP address is transferred to the IP phone 11. This connection request response is transmitted to the IP telephone 12 via the router 42, whereby the call connection is completed. After the call connection is completed, IP phone 11 and IP phone 12 make a direct call using each other's IP address. In the IP storage table 41b of the router 41, a combination of IP addresses whose destination is the IP address of the IP telephone 11 and whose source is the IP address of the IP telephone 12 is registered. Similarly, the IP storage table 42b of the router 42 is registered. Since the combination of the IP addresses with the IP address of the IP phone 12 as the destination and the IP address of the IP phone 11 as the transmission source is registered, the IP phone 11 and the IP phone 12 directly set the IP address of the communication partner. Can be used for communication. After the call is completed, the IP telephones 11 and 12 transmit a call disconnection notification to the call control server 21 as in the first embodiment. The call control server 21 that has received the call disconnection notification detects the completion of the call and performs call disconnection processing for causing the router 41 and the router 42 to delete the registered content of the IP address notification from the IP storage tables 41a and 42a.

  In the routers 41 and 42, among IP packets from the IP network 31 to the user side, IP addresses that are not registered as destination IP addresses in the IP storage tables 41b and 42b, that is, IP telephones accommodated by each router. As for IP packets destined for terminals other than the above, normal transfer is executed. Therefore, the IP packet from the WEB server 81 to the personal computer 71 is not discarded by the router 41.

  As described above, in the second embodiment, each of the subscriber routers 41 and 42 stores the combination of the transmission destination and the transmission source IP address transmitted from the call control server 21, and among the IP packets received from the IP network 31. For an IP packet whose destination address matches the destination IP address registered in the IP storage tables 41b and 42b, the IP packet is routed to the user side only when the source IP address is registered at the same time, and the source IP address Since IP packets that are not registered as addresses are discarded, a third party who acquires the IP addresses of the IP telephones 11 and 12 by some means uses the IP terminal 51 to reject a service such as a DOS attack. Even if an attempt is made to obstruct communications performed by the IP telephones 11 and 12 due to an attack or the like, Since the source IP address of the IP packet transmitted by the IP terminal 51 is not registered in the IP storage table of the routers 41 and 42, as shown in FIG. 9, the routers 41 and 42 are as shown in FIG. The IP packet transmitted by the third party's IP terminal 51 is not transferred to the IP telephones 11 and 12 accommodated therein. For this reason, communication interference by a third party can be reliably prevented. Furthermore, in the second embodiment, in the routers 41 and 42, among IP packets from the IP network 31 to the user side, IP addresses that are not registered as destination IP addresses in the IP storage tables 41b and 42b, Since IP packets destined for terminals other than IP telephones accommodated in the router are transferred as usual, communications such as WEB access performed by a personal computer can be performed simultaneously.

Embodiment 3 FIG.
Next, Embodiment 3 of the present invention will be described with reference to FIG. In the IP telephone system of the first embodiment, in the call disconnection process after the call ends, the call control server 21 notifies the router 41 and the router 42 to delete the IP address from the IP storage tables 41a and 42a. In this embodiment, the process of deleting the registration of the IP address from the IP storage tables 41a and 42a is performed. However, in the third embodiment, this process is simplified, and the IP telephones 11 and 12 do not issue a call disconnection notification. The call control server 21 does not issue a notification for deleting the IP address.

  When the routers 41 and 42 detect that the IP packet having the IP address registered in the IP storage table 41a or 42a as the transmission source IP address has not been received for a predetermined time or longer, the routers 41 and 42 set the IP address to the IP address itself. It operates to delete from the storage tables 41a and 42a. That is, when the router 41 detects that an IP packet having the IP address of the IP phone 12 as the source IP address has not been received for a predetermined time or longer, the router 41 deletes the IP address of the IP phone 12 from the IP storage table 41a. . When the router 42 detects that an IP packet having the IP address of the IP phone 11 as the transmission source IP address has not been received for a predetermined time or longer, the router 42 deletes the IP address of the IP phone 11 from the IP storage table 42a. . Thus, in the IP telephone system according to the third embodiment, the load on the call control server 21 can be reduced.

  The third embodiment may be applied to the IP telephone system of the second embodiment. In this case, when the routers 41 and 42 do not receive an IP packet whose transmission source IP address and destination IP address match the registered content of the storage table for a predetermined time or longer, the registered data is deleted. .

Embodiment 4 FIG.
Next, Embodiment 4 will be described with reference to FIGS. The fourth embodiment is a modification of the first embodiment. In the routers 41 and 42 of the fourth embodiment shown in FIG. 12, the IP addresses registered in the IP storage tables 41c and 42c are as shown in FIG. The source IP address is not permitted to be transferred from the IP network 31 to the user side. In FIG. 13, the IP address of the third party IP terminal 51 is registered as the source IP address that does not permit transfer.

  When the third party IP terminal 51 interferes with communication due to a denial of service attack or the like, the IP packet transmitted by the third party is received by the IP telephones 11 and 12 via the routers 41 and 42 which are subscriber routers. Therefore, the routers 41 and 42 as subscriber routers can acquire the transmission source IP address of the IP packet transmitted for the purpose of interference. Accordingly, the routers 41 and 42 register the source IP address acquired from the IP packet transmitted by the disturber in the IP storage tables 41c and 42c.

  Then, the routers 41 and 42 inspect the IP packets transferred from the IP network 31 to the user side using the registration data of the IP storage tables 41c and 42c. That is, when the source address of the IP packet transferred from the IP network 31 to the user side matches the source IP address registered in the IP storage tables 41c and 42c, the IP packet is discarded without being transferred to the user side. To do.

  Therefore, in the fourth embodiment, the IP packet transmitted by the communication disturber is not transmitted to the IP phone, and it is possible to prevent communication interference and mischief calls.

  As described above, the present invention is useful for an IP telephone system that transmits voice information between IP telephones using IP packets.

1 is a diagram showing a configuration of an IP telephone system according to a first embodiment. In Embodiment 1, it is a figure which shows the memory content of the IP storage table built in a subscriber router. 6 is a diagram illustrating a communication procedure according to the first embodiment. FIG. In Embodiment 1, it is a figure which shows the memory content of the IP storage table built in a subscriber router. 3 is a diagram showing blocking of IP packets from a third party in the IP telephone system according to Embodiment 1. FIG. It is a figure which shows the structure of the IP telephone system of Embodiment 2. FIG. In Embodiment 2, it is a figure which shows the memory content of the IP storage table built in a subscriber router. FIG. 10 is a diagram illustrating a communication procedure according to the second embodiment. In Embodiment 2, it is a figure which shows the memory content of the IP storage table built in a subscriber router. 6 is a diagram showing blocking of an IP packet from a third party in the IP telephone system of Embodiment 2. FIG. FIG. 10 is a diagram illustrating a communication procedure according to the third embodiment. FIG. 10 is a diagram illustrating blocking of an IP packet from a third party in the IP telephone system according to the fourth embodiment. In Embodiment 4, it is a figure which shows the memory content of the IP storage table built in a subscriber router.

Explanation of symbols

11, 12 IP phone (terminal)
21 Call control server 31 IP network 41, 42 Router (subscriber router)
41a, 42a, 41b, 42b, 41c, 42c IP storage table 51 IP terminal 71 PC 81 Web server

Claims (8)

A plurality of terminals to which IP addresses for transmitting and receiving voice as IP packets are assigned;
An IP network having a function of routing an IP packet and including a plurality of subscriber routers connecting the terminal to the IP network;
One or more call control servers that perform call connection control;
An IP phone system comprising:
The call control server
A means for notifying a subscriber router that connects a terminal that communicates at the time of call connection to an IP network with an IP address of a terminal that is a communication partner of the terminal accommodated by the subscriber router;
The subscriber router is:
A storage table for registering the IP address notified from the call control server;
A terminal that checks only the source IP address of the IP packet received from the IP network side based on the registered contents of the storage table and accommodates only IP packets having the IP address registered in the IP storage table as the source address A means of routing;
An IP telephone system comprising:   2. The call control server according to claim 1, wherein the call control server executes a call disconnection process for deleting the IP address of the notified terminal from the storage table of the subscriber router in response to a call disconnection notification from the terminal. IP phone system.   2. The subscriber router according to claim 1, wherein when the IP packet whose transmission source IP address matches the registered content of the storage table is not received for a predetermined time or more, the subscriber router deletes the registered data. IP phone system. A plurality of terminals to which IP addresses for transmitting and receiving voice as IP packets are assigned;
An IP network having a function of routing an IP packet and including a plurality of subscriber routers connecting the terminal to the IP network;
One or more call control servers that perform call connection control;
An IP phone system comprising:
The call control server
For a subscriber router that connects a terminal that communicates during call connection to an IP network, the IP address of the terminal accommodated by the subscriber router is set as the destination IP address, and the IP of the terminal that is the communication partner of the accommodated terminal Means for notifying the address as a source IP address;
The subscriber router is:
A storage table for registering a combination of a destination IP address and a source IP address notified from the call control server;
The transmission source IP address of the IP packet received from the IP network side is inspected based on the registered contents of the storage table, and for the IP packet that matches the destination IP address registered in the storage table, the transmission source IP address is also simultaneously Means for routing to terminals containing only conforming IP packets;
An IP telephone system comprising:   5. The call control server, in response to a call disconnection notification from a terminal, executes a call disconnection process for deleting the notified IP address of the terminal from the storage table of the subscriber router. IP phone system.   The subscriber router deletes the registered data when it does not receive an IP packet whose source IP address and destination IP address match the registered contents of the storage table for a predetermined time or more. 4. The IP telephone system according to 4. A plurality of terminals to which IP addresses for transmitting and receiving voice as IP packets are assigned;
An IP network having a function of routing an IP packet and including a plurality of subscriber routers connecting the terminal to the IP network;
One or more call control servers that perform call connection control;
An IP phone system comprising:
The subscriber router is:
A storage table for registering a source IP address that does not permit routing to a terminal accommodated from the IP network side;
Means for discarding the IP packet when receiving an IP packet having a source address of the IP address registered in the storage table;
An IP telephone system comprising: A plurality of terminals provided with IP addresses for transmitting and receiving voice as IP packets, an IP network having a function of routing IP packets and including a plurality of subscriber routers connecting the terminals to the IP network; A subscriber router in an IP telephone system comprising one or more call control servers for connection control,
A storage table for registering the IP address of the terminal that is the communication partner of the terminal connected to the IP network by the subscriber router, notified by the call control server when the call is connected.
Inspects the source IP address of the IP packet received from the IP network side based on the registration contents of the storage table, and routes to a terminal that accommodates only IP packets having the IP address registered in the storage table as the source address Means to
A subscriber router characterized by comprising:

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