JP4242752B2 - Address table management method and terminal - Google Patents

Description

  The present invention relates to an address table management method for managing an address table including IP addresses of terminals belonging to a multicast group, and a terminal.

  An identifier called URI (Uniform Resource Identifier) [IETF RFC2396 “Uniform Resource Identifiers”] is known as an identifier for uniquely specifying a user or a terminal device. The URI is a logical identifier and is used for identifying a transmission source and a transmission destination when performing communication. Also, since the URI is an identifier in the application layer, when the URI is used for communication, it is necessary to perform mapping between the URI and the IP address.

  Note that the most used URI is a URL (Uniform Resource Locator) used when a Resource is uniquely specified in a Web Browser or the like.

  As described above, when a URL is used for communication, it is necessary to map (name resolution) the URL and the IP address. As this mapping technique, a technique called DNS (Domain Name System) [IETF RFC1035 “Domain names-implementation and specification”] is known. In DNS, name resolution on the Internet is performed by a server (name server) that stores data necessary for name resolution.

  Another name resolution method that is effective in a network that is relatively smaller than the entire Internet is also known. For example, in Windows, which is a Microsoft OS, communication is possible by mapping host names and IP addresses using a method unique to Vender. At this time, as the communication protocol itself, a protocol uniquely defined by Vender (eg, Microsoft NetBIOS) is used. Also, a method is known in which a combination of a host name and an IP address is stored in advance in each terminal, like a hosts file in UNIX.

On the other hand, in the AdHoc network, each other knows the other party's IP address in advance, and communication is performed based on the IP address. Further, depending on the application and the OS, the host name and the IP address are mapped by a method unique to Vender, and communication is performed using the host name.
JP-A-11-55350

  However, since the communication protocol unique to Vender is different from the communication protocol in the public network, there is a problem that it is necessary to implement software that operates the communication protocol unique to Vender.

  Accordingly, the present invention has been made to solve the above-described problem, and the network address of each terminal is unified in a specific network (for example, AdHoc network) without using a communication protocol unique to Vender. It is an object of the present invention to provide an address table management method and a terminal capable of managing an address table.

  According to a first aspect of the present invention, there is provided an address table management method for managing an address table including IP addresses of terminals belonging to a multicast group, wherein an IP address of the first terminal and a network address of a network to which the first terminal belongs are obtained. Based on the step A in which the first terminal notifies the multicast group and the IP address and network address of the first terminal notified by the first terminal, the IP address of the second terminal is set to the second terminal. The process B set by the first terminal, the process C by which the second terminal updates the address table based on the IP address of the first terminal notified by the first terminal, and the second terminal set by the process B The second terminal notifies the IP address of the second terminal to the multicast group, and the IP address of the second terminal notified to the multicast group. Based on less, and summarized in that comprises a step E of the address table is the first terminal to update.

  The second feature of the present invention is that the terminal managing the address table including the IP addresses of the terminals belonging to the multicast group notifies the multicast group of the IP address of the own terminal and the network address of the network to which the own terminal belongs. And the IP address of the other terminal set in the other terminal based on the IP address and the network address notified by the notification unit, the address table based on the IP address of the other terminal The gist of the present invention is to include an updating unit for updating.

  According to such a feature, the terminal updates the address table based on the IP address of the other terminal set in the other terminal based on the IP address of the own terminal and the network address of the own terminal. Can manage an address table with matching network addresses.

  The third feature of the present invention is that the terminal managing the address table including the IP addresses of the terminals belonging to the multicast group receives the IP address of the other terminal notified to the multicast group and the network address of the network to which the other terminal belongs. An IP address setting unit for setting the IP address of the own terminal based on the above, a notification unit for notifying the IP address of the own terminal set by the IP address setting unit to the multicast group, and others notified to the multicast group And an update unit that updates the address table based on the IP address of the terminal.

  According to this feature, the terminal sets the IP address of its own terminal based on the IP address of the other terminal and the network address of the other terminal, so that the terminal has an address table in which the network address is consistent. Can be managed.

  In addition, the terminal notifies the multicast group of the IP address of the own terminal set based on the IP address of the other terminal and the network address of the other terminal, so that the network address can be matched in the other terminal. Manage the address table.

  According to a fourth aspect of the present invention, when a terminal that manages an address table including IP addresses of terminals belonging to a multicast group joins the multicast group from the middle, notification of the address table is made to the terminals belonging to the multicast group. A request unit for requesting, an IP address setting unit for setting an IP address not included in the notified address table as an IP address of the own terminal based on the network address specified by the notified address table, and a notification The gist of the present invention is to include a management unit that manages the address table that has been set, and a notification unit that notifies the IP address of the own terminal set by the IP address setting unit to the multicast group.

  According to such a feature, the terminal sets the IP address of its own terminal based on the network address related to the address table in which the network address is already matched, so that the terminal can obtain the address table in which the network address is matched. Can be managed.

  In addition, when the terminal notifies the multicast group of the IP address of its own terminal set based on the network address in the address table in which the network address is already matched, the network address can be matched in other terminals as well. The address table taken can be managed.

  In the second feature to the fourth feature of the present invention, when the IP address included in the address table and the IP address set in the terminal overlap, based on the network address notified to the multicast group Preferably, the terminal includes an IP address resetting unit that resets the IP address of the terminal itself, and the notification unit notifies the multicast group of the IP address of the terminal set by the IP address resetting unit.

  In the second to fourth features of the present invention, the IP address resetting unit is configured so that the number of terminals in which an IP address belonging to another network address is set in the address table belongs to the network address of the own terminal. When the number of addresses is larger than the number of terminals set, it is preferable to reset the IP address of the own terminal based on another network address.

  In the second to fourth features of the present invention, when the IP address resetting unit has an address table in which the address space included in the other network address is larger than the address space included in the network address of the own terminal. It is preferable to reset the IP address of the own terminal based on another network address.

  In the second to fourth features of the present invention, when the notifying unit communicates with another terminal whose IP address is not included in the address table, the information requesting the IP address of the other terminal is multicast. It is preferable to notify the group.

  In the second to fourth aspects of the present invention, it is preferable that the notification unit notifies the multicast group of the user identifier of the own terminal together with the IP address of the own terminal.

  In the second to fourth aspects of the present invention, it is preferable that the notifying unit notifies the multicast group of the terminal identifier of the own terminal together with the IP address of the own terminal.

  According to the present invention, an address table management method for managing an address table in which network addresses of terminals are unified in a specific network (for example, AdHoc network) without using a communication protocol unique to Vender, and a terminal Can be provided.

(Configuration of terminal according to one embodiment of the present invention)
Hereinafter, the configuration of a terminal according to an embodiment of the present invention and a network to which the terminal is connected will be described with reference to FIGS. FIG. 1 is an overall configuration diagram of a network to which terminals according to the present embodiment are connected.

  As shown in FIG. 1, the terminals 10a to 10d according to the present embodiment form a specific network (hereinafter referred to as AdHoc network). Further, the terminals 10a to 10d are assumed to form an AdHoc mode communication network in a physical layer (Layer 1) and a MAC sub-layer (Layer 2) by a wireless network (for example, a wireless LAN compliant with IEEE 802.11). Further, it is assumed that the terminals 10a to 10d belong to a predetermined multicast group.

  The terminals 10a to 10d are assumed to have the same configuration. Hereinafter, the terminal 10a will be described as an example. FIG. 2 is a block diagram showing a configuration of the terminal 10a according to the present embodiment.

  As illustrated in FIG. 2, the terminal 10 a includes a transmission / reception unit 11, a control unit 12, an IP address setting unit 13, and a storage unit 14.

  The transmission / reception unit 11 transmits / receives information to / from each terminal belonging to the multicast group. For example, the transmission / reception unit 11 includes the IP address (192.168.0.11) of the own terminal, a user identifier (hereinafter, URI (alice@company.co.jp)), a terminal identifier (hereinafter, MAC address), and a subnet mask. Name resolution information including (255.255.255.0), the AdHoc network name, and the effective duration of the AdHoc network is transmitted to the multicast group. That is, the transmission / reception unit 11 transmits the IP address (192.168.0.11) of the terminal 10a and the subnet mask (255.255.255.0) to the multicast group, whereby the IP address of the terminal 10a ( 192.168.0.11) and the network address (192.168.0.0) of the network to which the terminal 10a belongs are notified to the multicast group. Further, the transmission / reception unit 11 receives the name resolution information transmitted to the multicast group by other terminals (terminals 10b to 10d).

  The control unit 12 determines reference name resolution information (hereinafter referred to as reference name resolution information) from the name resolution information transmitted to the multicast group. Here, the control unit 12 of the terminal 10a determines that the name resolution information first transmitted to the multicast group in terms of time is the reference name resolution information. Note that the control unit 12 of the terminal 10a uses the name resolution information transmitted from the terminal as a reference when the name resolution information transmitted from the terminal to the multicast group is the name resolution information transmitted first in time. Judged as name resolution information.

  The control unit 12 updates the name resolution table (address table) including the IP addresses of the terminals participating in the AdHoc network based on the name resolution information transmitted to the multicast group by other terminals.

  When the effective duration of the AdHoc network associated with the IP address included in the name resolution table is exhausted, the control unit 12 deletes information associated with the IP address. Moreover, the control part 12 may be comprised so that the effective continuation time may be extended according to predetermined conditions, when the effective continuation time of an AdHoc network runs out.

  When receiving the reference name resolution information from another terminal, the IP address setting unit 13 sets (or re-sets) the IP address of the own terminal based on the IP address and the subnet mask included in the reference name resolution information. Set). That is, the IP address setting unit 13 sets the IP address of the own terminal based on the IP address notified by the other terminal and the network address of the network to which the other terminal belongs.

  Note that the IP address setting unit 13 does not set the network address, the broadcast address, and the IP address of another terminal as the IP address of the own terminal.

  Further, the IP address setting unit 13 uses the reference name resolution information transmitted by the own terminal (or received from another terminal) when the IP address included in the name resolution table overlaps with the IP address of the own terminal. Based on the included IP address and subnet mask, the IP address of the own terminal is reset.

  Further, the IP address setting unit 13 is configured so that the number of terminals set with IP addresses belonging to network addresses other than the own terminal in the name resolution table is the number of terminals set with IP addresses belonging to the network address of the own terminal. When the number is larger than the number, the IP address of the own terminal is reset based on the network address other than the own terminal (the network address having the largest number of terminals set with the IP address belonging to the network address). The reason why the network addresses are not unified in the name resolution table is that, for example, when different name resolution information is transmitted almost simultaneously, each terminal may recognize different name resolution information as reference name resolution information. .

  In addition, the IP address setting unit 13 includes, in the name resolution table, the number of terminals set with IP addresses belonging to network addresses other than the own terminal and the number of terminals set with IP addresses belonging to the network address of the own terminal. Are the same, and the IP address space included in the network address other than the own terminal is larger than the IP address space included in the network address of the own terminal, the network address other than the own terminal (including the largest IP address space) Based on the network address, the IP address of the own terminal is reset.

  In this embodiment, the IP address setting unit 13 determines the own terminal based on the IP address of the other terminal notified to the multicast group, the network address of the network to which the other terminal belongs, and (reference name resolution information). The IP address setting unit for setting the IP address, and the IP address of the other terminal notified to the multicast group and the other terminal when the IP address included in the name resolution table and the IP address of the own terminal overlap. An IP address resetting unit configured to reset the IP address of the own terminal based on the network address of the network to which the terminal belongs and (reference name resolution information).

  The storage unit 14 stores a name resolution table (address table) including IP addresses of terminals participating in the AdHoc network. Specifically, this will be described with reference to FIG.

  As shown in the figure, the storage unit 14 stores the URIs of terminals participating in the AdHoc network (for example, IP address, MAC address, and Status (whether the terminal is participating in the AdHoc network (“Active” or In addition to the above-mentioned information, the name resolution table is associated with the AdHoc network name, the AdHoc network effective duration, and the like. Yes.

(Operation of terminal according to one embodiment of the present invention)
Hereinafter, the operation of the terminal according to the embodiment of the present invention will be described with reference to FIGS. FIG. 4 is a flowchart showing name resolution table sharing processing (formation) according to the present embodiment.

  As shown in the figure, in step 11, an arbitrary terminal (for example, terminal 10a) transmits name resolution information to the multicast group.

  In step 12, the terminal (for example, the terminal 10b to the terminal 10d) that has received the name resolution information creates a name resolution table based on the name resolution information.

  In step 13, each terminal (terminal 10a to terminal 10d) checks whether or not there is only one name resolution information received by the terminal itself (including the name resolution information if the terminal transmits it). . Each terminal proceeds to the process of step 15 when there is only one name resolution information, and proceeds to the process of step 14 when there are a plurality of name resolution information.

  In step 14, each terminal (terminal 10a to terminal 10d) recognizes the name resolution information transmitted first in terms of time as reference name resolution information.

  In step 15, each terminal (for example, terminal 10b to terminal 10d) recognizes the received name resolution information as reference name resolution information.

  Hereinafter, it is assumed that each terminal (terminal 10b to terminal 10d) recognizes the name resolution information transmitted by the terminal 10a as the reference name resolution information in step 14 or step 15.

  In step 16, each terminal (terminal 10b to terminal 10d) that has received the reference name resolution information receives the IP address (192.168.0.11) and subnet mask (255.255) of the terminal 10a included in the reference name resolution information. 255.0), the IP address of the own terminal is set.

  Each terminal (terminal 10b to terminal 10d) has a network address (192.168.0.0), a broadcast address (192.168.0.255), and an IP address (192.168.0.11) of the terminal 10a. Suppose that it is not set as the IP address of its own terminal.

  In step 17, each terminal (terminal 10b to terminal 10d) transmits name resolution information to the multicast group.

  In step 18, each terminal (terminal 10a to terminal 10d) updates the name resolution table based on the received name resolution information.

  In step 19, each terminal (terminal 10a to terminal 10d) checks whether the IP address of the other terminal included in the name resolution table overlaps with the IP address of its own terminal. Each terminal ends the name resolution table sharing process (formation) when the IP address is not duplicated, and proceeds to the process of step 20 when the IP address is duplicated.

  In step 20, each terminal (terminal 10a to terminal 10d) has its own terminal IP address and another terminal's IP address overlapping in the name resolution table. Reset the IP address.

  Hereinafter, a description will be given of processing for correcting a case where the network address of each terminal is not unified in the name resolution table managed by each terminal. FIG. 5 is a flowchart showing name resolution table sharing processing (mismatch correction) according to the present embodiment. Hereinafter, the operation of the terminal 10a will be described as an example.

  As shown in the figure, in step 31, the terminal 10a checks whether or not the network address of each terminal is unified in its own name resolution table. If the network address of each terminal is not unified, the terminal 10a proceeds to the process of step 32. If the network address of each terminal is unified, the name resolution table sharing process (mismatch correction). Exit.

  In step 32, the terminal 10a checks whether or not there is a difference in the number of terminals set with IP addresses belonging to the respective network addresses in the name resolution table of the terminal itself. Further, when the number of terminals set with IP addresses belonging to each network address is the same, the terminal 10a proceeds to the process of step 34, and the terminal 10a is set to the terminal set with the IP address belonging to each network address. If there is a difference between the numbers, the process proceeds to step 33.

  In step 33, the terminal 10a re-recognizes the reference name resolution information related to the network address having the largest number of terminals to which the IP address belonging to the network address is set as the reference name resolution information in its own terminal.

  In step 34, the terminal 10a checks whether or not there is a difference in the size of the IP address space included in each network address in the name resolution table of its own terminal. If there is a difference in the size of the IP address space, the terminal 10a proceeds to the process of step 35. If there is no difference in the size of the IP address space, the terminal 10a proceeds to the process of step 36.

  In step 35, the terminal 10a re-recognizes the reference name resolution information related to the network address having the largest IP address space as the reference name resolution information in its own terminal.

  In step 36, the terminal 10a recognizes the reference name resolution information having the smallest IP address as the reference name resolution information of the terminal itself.

  In step 37, if the network address specified by the reference name resolution information and the network address of the own terminal are not matched, the terminal 10a determines the IP address of the own terminal based on the reference name resolution information. Reset it.

  In step 38, the terminal 10a transmits the name resolution information to the multicast group.

  In step 39, the terminal 10a updates the name resolution table based on the name resolution information received from the other terminals.

  In step 40, the terminal 10a checks whether or not the IP address of its own terminal and the IP address of another terminal overlap in the name resolution table. If the IP address is duplicated, the terminal 10a proceeds to the process of step 41. If the IP address is not duplicated, the terminal 10a ends the name resolution table sharing process (mismatch correction).

  In step 41, when the IP address of the terminal 10a and the IP address of another terminal overlap, the terminal 10a resets the IP address of the terminal 10a.

  A case will be described below where communication is performed with another terminal (transmission destination) related to an IP address that does not exist in the name resolution table of the terminal (transmission source). The factors that cause the IP address of the other terminal not to exist in the name resolution table of the own terminal are (1) the other terminal is not connected to the network, and (2) the other terminal is transmitting name resolution information. There may be factors such as no (3) the terminal itself cannot receive the name resolution information transmitted by another terminal.

  Hereinafter, the case where the own terminal (transmission source) is the terminal 10a and the other terminal (transmission destination) is the terminal 10b will be described as an example.

  FIG. 6 is a flowchart showing name resolution table sharing processing (communication with a terminal not in the name resolution table) according to the present embodiment. As shown in the figure, in step 51, the terminal 10a starts communication with the terminal 10b.

  In step 52, the terminal 10a checks whether or not the URI (IP address) of the terminal 10b is included in the name resolution table of the terminal 10a. If the URI of the terminal 10b is included, the terminal 10a ends the name resolution table sharing process. If the URI of the terminal 10b is not included, the terminal 10a proceeds to the process of step 53.

  In step 53, the terminal 10a transmits a terminal search request to the multicast group.

  In step 54, the terminal 10a confirms whether or not a response to the terminal search request is within a predetermined time. If the response to the terminal search request is not within the predetermined time, the terminal 10a proceeds to the process of step 55. If the response to the terminal search request is within the predetermined time, the process of step 56 is performed. Move on.

  At this time, when the terminal 10b receives the terminal search request, the terminal 10b transmits a terminal search response to the multicast group when the name resolution information of the terminal 10b has not yet been transmitted to the multicast group. In addition, when the terminal 10b has already transmitted the name resolution information of the terminal itself to the multicast group, the terminal 10b transmits the name resolution information of the terminal itself to the multicast group again.

  In step 55, the terminal 10a stops communication with the terminal 10b.

  In step 56, the terminal 10a confirms whether or not the response to the terminal search request is name resolution information. If the response to the terminal search request is name resolution information, the terminal 10a proceeds to step 61. If the response to the terminal search request is not name resolution information, the terminal 10a proceeds to step 57.

  In step 57, the terminal 10a confirms whether the response to the terminal search request is a terminal search response. If the response to the terminal search request is a terminal search response, the terminal 10a proceeds to step 58. If the response to the terminal search request is not a terminal search response, the terminal 10a proceeds to step 55.

  In step 58, the terminal 10a transmits a name resolution table managed by the terminal 10a to the terminal 10b.

  In step 59, the terminal 10b sets the IP address of its own terminal based on the network address specified by the received name resolution table.

  In step 60, the terminal 10b transmits the name resolution information of its own terminal to the multicast group.

  In step 61, the terminal 10a updates the name resolution table based on the name resolution information received from the terminal 10b.

  In this embodiment, only one AdHoc network is formed. However, a plurality of AdHoc networks are formed in the same LAN segment (in the case of a wired network) or the same wireless channel (in the case of a wireless network). May be.

  At this time, each terminal participating in a plurality of AdHoc networks shall manage a name resolution table unified with different network addresses. Also, it is assumed that terminals participating in a plurality of AdHoc networks can set different IP addresses for each AdHoc network.

  Also, a terminal that joins an already formed AdHoc network from the middle sends a name resolution table request to a multicast group in order to request a terminal that participates in the AdHoc network for a name resolution table managed by the terminal. Send to. At this time, a terminal already participating in the AdHoc network transmits a name resolution table managed by the own terminal to the multicast group. However, a terminal already participating in the AdHoc network does not transmit a name resolution table in order to avoid duplicate transmission when any terminal has already transmitted the name resolution table.

(Operation and effect of terminal according to one embodiment of the present invention)
According to the terminal according to the present embodiment, the terminal 10a transmits the IP address and subnet mask of the terminal 10a to the multicast group, thereby changing the IP address of the terminal 10a and the network address of the network to which the terminal 10a belongs. Terminal (terminal 10b to terminal 10d) and received the IP address set in the other terminal (terminal 10b to terminal 10d) based on the notified IP address and network address of terminal 10a. By updating the name resolution table (address table) based on the IP address, the terminal 10a can manage the name resolution table with a unified network address.

  Further, the terminals 10b to 10d set their own IP addresses based on the IP addresses and network addresses of other terminals (terminals 10a), and create a name resolution table, so that the terminals 10b to 10d 10d can manage a name resolution table with a unified network address.

  Further, the terminal 10b to the terminal 10d set the IP address of the own terminal based on the IP address and network address of the other terminal (terminal 10a), and transmit the IP address of the own terminal to the multicast group. Thus, each terminal (terminal 10a to terminal 10d) can share a name resolution table with a unified network address.

  Further, when each terminal (terminal 10a to terminal 10d) includes IP addresses included in a plurality of network addresses in its own name resolution table, an IP address belonging to the network address is set. Based on the reference name resolution information related to the network address having the largest number of terminals, the IP address of the own terminal is reset, and the reset IP address is transmitted to the multicast group. 10d) can unify network addresses in the name resolution table managed by its own terminal, and can share the name resolution table with the unified network address.

  Furthermore, when each terminal (terminal 10a to terminal 10d) includes IP addresses included in a plurality of network addresses in its own name resolution table, the reference name relating to the network address having the largest IP address space Based on the resolution information, by resetting the IP address of the own terminal and transmitting the reset IP address to the multicast group, each terminal (terminal 10a to terminal 10d) can manage the name resolution table managed by the own terminal. Network addresses can be unified, and a name resolution table with unified network addresses can be shared.

1 is an overall configuration diagram of a network to which a terminal according to the present embodiment is connected. It is a figure which shows the structure of the terminal which concerns on this embodiment. It is a figure which shows an example of the name resolution table which concerns on this embodiment. It is a flowchart which shows the name resolution table sharing process (formation) concerning this embodiment. It is a flowchart which shows the name resolution table sharing process (mismatch correction) which concerns on this embodiment. It is a flowchart which shows the name resolution table sharing process (communication with the terminal which is not in a name resolution table) concerning this embodiment.

Explanation of symbols

  10a to 10d ... terminal, 11 ... transmission / reception unit, 12 ... control unit, 13 ... IP address setting unit, 14 ... 13 storage unit

Claims (10)

An address table management method for managing an address table including IP addresses of terminals belonging to a multicast group,
A step in which the first terminal notifies the multicast group of the IP address of the first terminal and the network address of the network to which the first terminal belongs;
The second terminal has the same network address as the network address of the first terminal based on the IP address and network address of the first terminal notified by the first terminal; and Setting an IP address that does not overlap with the IP address of the first terminal as the IP address of the second terminal;
A step C in which the second terminal updates the address table based on the IP address of the first terminal notified by the first terminal;
A step D in which the second terminal notifies the multicast group of the IP address of the second terminal set in the step B;
A step E in which the first terminal updates the address table based on the IP address of the second terminal notified to the multicast group ;
In the address table, the number of terminals for which the first terminal or the second terminal is set with an IP address belonging to another network address is set to an IP address belonging to the network address of the own terminal. And a step F of resetting the IP address of the own terminal based on the other network address when the number is larger than the number of terminals .   An address table management method for managing an address table including IP addresses of terminals belonging to a multicast group,
  A step in which the first terminal notifies the multicast group of the IP address of the first terminal and the network address of the network to which the first terminal belongs;
  The second terminal has the same network address as the network address of the first terminal based on the IP address and network address of the first terminal notified by the first terminal; and Setting an IP address that does not overlap with the IP address of the first terminal as the IP address of the second terminal;
  A step C in which the second terminal updates the address table based on the IP address of the first terminal notified by the first terminal;
  A step D in which the second terminal notifies the multicast group of the IP address of the second terminal set in the step B;
  A step E in which the first terminal updates the address table based on the IP address of the second terminal notified to the multicast group;
  When the first terminal or the second terminal has an address space included in another network address in the address table larger than an address space included in the network address of its own terminal, the other network address And a step F of resetting the IP address of the own terminal on the basis of the address table management method. A terminal that manages an address table including IP addresses of terminals belonging to a multicast group,
Based on the IP address of the other terminal notified to the multicast group and the network address of the network to which the other terminal belongs, and has the same network address as the network address of the other terminal, and An IP address setting unit for setting an IP address not overlapping with the IP address of another terminal as the IP address of the own terminal;
A notifying unit for notifying the IP address of the terminal set by the IP address setting unit to the multicast group;
An updating unit for updating the address table based on the IP address of the other terminal notified to the multicast group ;
In the address table, when the number of terminals set with IP addresses belonging to other network addresses is larger than the number of terminals set with IP addresses belonging to the network address of the own terminal, the other networks A terminal comprising: an IP address resetting unit that resets the IP address of the terminal based on the address .   A terminal that manages an address table including IP addresses of terminals belonging to a multicast group,
  Based on the IP address of the other terminal notified to the multicast group and the network address of the network to which the other terminal belongs, and has the same network address as the network address of the other terminal, and An IP address setting unit for setting an IP address not overlapping with the IP address of another terminal as the IP address of the own terminal;
  A notifying unit for notifying the IP address of the terminal set by the IP address setting unit to the multicast group;
  An updating unit for updating the address table based on the IP address of the other terminal notified to the multicast group;
  In the address table, when the address space included in the other network address is larger than the address space included in the network address of the own terminal, the IP address of the own terminal is reset based on the other network address. A terminal comprising: an IP address resetting unit. A terminal that manages an address table including IP addresses of terminals belonging to a multicast group,
A request unit for requesting notification of the address table to terminals belonging to the multicast group when joining the multicast group from the middle;
An IP address setting unit that sets an IP address that has the same network address as the network address specified by the notified address table and is not included in the notified address table as the IP address of its own terminal When,
A management unit for managing the notified address table;
A notifying unit for notifying the IP address of the terminal set by the IP address setting unit to the multicast group ;
In the address table, when the number of terminals set with IP addresses belonging to other network addresses is larger than the number of terminals set with IP addresses belonging to the network address of the own terminal, the other networks A terminal comprising: an IP address resetting unit that resets the IP address of the terminal based on the address .   A terminal that manages an address table including IP addresses of terminals belonging to a multicast group,
  A request unit for requesting notification of the address table to terminals belonging to the multicast group when joining the multicast group from the middle;
  An IP address setting unit that sets an IP address that has the same network address as the network address specified by the notified address table and is not included in the notified address table as the IP address of its own terminal When,
  A management unit for managing the notified address table;
  A notifying unit for notifying the IP address of the terminal set by the IP address setting unit to the multicast group;
  In the address table, when the address space included in the other network address is larger than the address space included in the network address of the own terminal, the IP address of the own terminal is reset based on the other network address. A terminal comprising: an IP address resetting unit. IP for resetting the IP address of the own terminal based on the network address notified to the multicast group when the IP address included in the address table overlaps with the IP address set for the own terminal An address resetting unit,
The notification unit terminal according to claims 3 to 6 and notifies the IP address of the terminal that is set by the IP address resetting unit addressed the multicast group. The notification unit, when communicating with another terminal whose IP address is not included in the address table, notifies the multicast group of information requesting the IP address of the other terminal. The terminal of Claim 3 thru | or 7 . The notification unit, together with the IP address of the terminal, the terminal according to claims 3 to 8 and notifies the user identifier of the own terminal addressed to the multicast group. The notification unit, together with the IP address of the terminal, the terminal according to claims 3 to 9 and notifies the terminal identifier of the own terminal addressed to the multicast group.

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