JP2005328281A - Network system and communication method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a network system and a communication method that enable communication devices to communicate with each other always through a repeating device stored with network constitution information by virtually dividing one physical network and enable the communication between the communication devices without additionally installing software in the communication devices in advance nor making special settings. <P>SOLUTION: In the network system which is equipped with a plurality of communication devices capable of communicating with each other and the repeating device connecting with an external network and in which the respective communication devices and repeating device have unique addresses and pieces of address division information for dividing the addresses into network address parts and host address parts, the communication devices and repeating device have the pieces of address division information which are different and the communication devices communicate with each other via the repeating device. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a network system and a communication method that always communicate via a relay device when communication devices connected via a network communicate with each other.

  Recently, due to the rapid spread of the Internet, the spread of viruses, worms and other infections to personal computers (hereinafter referred to as PCs) used by general users has become a social problem. In other words, in an open communication environment, there are many PCs where security holes are left unattended, virus PCs that fail to update virus patterns, etc., and virus transmission via such mail transmission, file sharing, etc. Infections such as worms are spreading throughout the network.

  In order to prevent such infections such as viruses and worms, packet filtering by a firewall and a router is performed to prevent the entry of viruses and worms from the outside of the network.

  However, for example, when communicating between PCs connected to an Ethernet (registered trademark) LAN, communication is performed without going through a router. Therefore, even when using firewall, packet filtering by a router, etc. , Can not prevent the intrusion of worms. In other words, it is not possible to prevent invasion of viruses, worms, etc. by bringing in infected files on portable storage media, connecting to a LAN of portable PCs infected when connected to other networks, etc. It is difficult to detect and remove these, and there is a problem that they spread in the LAN over time.

  In order to deal with such problems, for example, in Patent Document 1, a switching hub connected in a LAN has a packet filtering function, so that even if communication between PCs in the same network is logically performed, A network system has been disclosed that can prevent the entry of viruses, worms, etc. via a switching hub.

One of the standard protocols is a method in which all communications are routed through a router by forming a virtual dedicated line between a router and a terminal, such as PPTP and PPPoE (Point to Point Protocol over Ethernet (registered trademark)). It is disclosed as.
JP 2003-348113 A

  However, in the network system as described above, if an attempt is made to function even when communication is performed between arbitrary PCs in the LAN, one switching hub port is physically required for one PC, and the hub As a result, it is necessary to dispose a large amount of expensive switching hubs having a packet filtering function, which is not a practical solution from an economical viewpoint.

  In addition, when using a virtual leased line, additional software must be installed in advance in each terminal, and it will be necessary to make appropriate settings according to the environment. From the time point of view that it takes a considerable amount of time for the initial setting time to become usable, there is a problem that it is not realistic.

  The present invention has been made in view of such circumstances. By virtually dividing one physical network, communication between communication devices is surely performed via a relay device that stores network configuration information. An object is to provide a network system and a communication method that can be performed. It is another object of the present invention to provide a network system and a communication method capable of performing communication between communication devices without additionally installing software in advance or performing special settings.

  In order to achieve the above object, a network system according to a first aspect of the present invention includes a plurality of communication devices capable of communicating with each other and a relay device connected to an external network, and each of the communication devices and the relay device is unique. In a network system having an address and address division information for dividing the address into a network address part and a host address part, the communication apparatus and the relay apparatus have the address division information different from each other and communicate between the communication apparatuses In this case, the relay apparatus is configured to pass through the relay device.

  In the network system according to the first invention, each communication device and relay device has a unique address and address division information for dividing the address into a network address portion and a host address portion. Have different address division information, and the value of the network address portion of each communication device is different from each other using the address division information unique to each communication device. As a result, when communicating between communication devices, one communication device recognizes that the other communication device is physically connected to a different network, and the transmission packet is always transmitted to the relay device. In addition, it is possible to perform audit processing such as packet filtering for all communications without changing the configuration of routers, intelligent hubs, etc., which are relay devices, so that safe and reliable communications can be performed.

  On the other hand, the relay device has address division information different from that of the communication device, and the network address portion of each communication device address divided by the address division information of the relay device is connected to the same network as the relay device. It is recognized that Therefore, the packet transmitted by the communication device is always sent to the relay device, and can be discarded or rewritten in the relay device. It is also possible for the relay device to directly transmit a packet to the communication device.

  Further, a part of the communication device may have the same address division information as the relay device. As a result, a communication device in which all communications pass through the relay device and a relay device that can directly transmit packets to other communication devices can be mixed.

  In the network system according to a second aspect of the present invention, in the first aspect, the address division information possessed by one communication apparatus is information having a unique address possessed by the one communication apparatus as one network address part. It is characterized by that.

  In the network system according to the second aspect of the invention, the unique address possessed by one communication device is recognized as one network address part as a whole by the address division information possessed by one communication device. Thereby, since one communication apparatus determines that the network is configured by only one communication apparatus and a relay apparatus, even if one communication apparatus communicates with another communication apparatus, Communication is always performed via the relay device, and audit processing such as packet filtering can be performed, so that safe and reliable communication can be performed.

  The network system according to a third aspect of the present invention is the network system according to the first aspect, wherein the address division information possessed by one communication device has a network address portion of a unique address possessed by the one communication device in a power of 2 An address is included.

  In the network system according to the third aspect of the invention, the address division information possessed by one communication apparatus is configured such that the network address portion of the unique address possessed by one communication apparatus includes a power of two host addresses. As a result, if there is no other communication device in the network address portion including the power-of-two host address, the one communication device determines that the network is composed of only one communication device and a relay device. Therefore, even when one communication device communicates with another communication device, it is always possible to communicate via a relay device and perform audit processing such as packet filtering, which is safe and reliable. Communication can be performed.

  According to a fourth aspect of the present invention, a communication method includes a plurality of communication devices that can communicate with each other and a relay device that is connected to an external network. Each of the communication devices and the relay device has a unique address and the address. In a communication method on a network having address division information for dividing a network address portion and a host address portion, the communication device and the relay device have different address division information and communicate between the communication devices. , Via the relay device.

  In the communication method according to the fourth aspect of the invention, each communication device and relay device has a unique address and address division information for dividing the address into a network address portion and a host address portion. Have different address division information, and the value of the network address portion of each communication device is different from each other using the address division information unique to each communication device. As a result, when communicating between communication devices, one communication device recognizes that the other communication device is physically connected to a different network, and the transmission packet is always transmitted to the relay device. In addition, it is possible to perform audit processing such as packet filtering for all communications without changing the configuration of routers, intelligent hubs, etc., which are relay devices, so that safe and reliable communications can be performed.

  On the other hand, the relay device has address division information different from that of the communication device, and the network address portion of the address of each communication device divided by the address division information of the relay device is the network portion of the address of the relay device. Since they are the same, it is recognized by the relay device that each communication device is connected to the same network. Therefore, the packet transmitted by the communication device is always sent to the relay device, and can be discarded or rewritten in the relay device. It is also possible for the relay device to directly transmit a packet to the communication device.

  Further, a part of the communication device may have the same address division information as the relay device. As a result, a communication device in which all communications pass through the relay device and a relay device that can directly transmit packets to other communication devices can be mixed.

  In the communication method according to a fifth aspect based on the fourth aspect, the address division information possessed by one communication apparatus is information having a unique address possessed by the one communication apparatus as one network address part. It is characterized by that.

  In the communication method according to the fifth aspect of the present invention, the unique address possessed by one communication device is recognized as one network address part as a whole by the address division information possessed by one communication device. Thereby, since one communication apparatus determines that the network is configured by only one communication apparatus and a relay apparatus, even if one communication apparatus communicates with another communication apparatus, Communication is always performed via the relay device, and audit processing such as packet filtering can be performed, so that safe and reliable communication can be performed.

  The communication method according to a sixth aspect of the present invention is the communication method according to the fourth aspect of the present invention, wherein the address division information possessed by one communication device has a network address portion of a unique address possessed by the one communication device and is a power of 2 hosts It includes an address.

  In the communication method according to the sixth aspect of the invention, the address division information possessed by one communication device is such that the network address portion of the unique address possessed by one communication device includes a power of 2 host addresses. As a result, if there is no other communication device in the network address portion including the power-of-two host address, the one communication device determines that the network is composed of only one communication device and a relay device. Therefore, even when one communication device communicates with another communication device, it is always possible to communicate via a relay device and perform audit processing such as packet filtering, which is safe and reliable. Communication can be performed.

  According to the first and fourth inventions, when communicating between communication devices, one communication device recognizes that another communication device is connected to a physically different network, and the transmission packet is always Since it is transmitted to the relay device, it is possible to perform audit processing such as packet filtering for all communications without changing the configuration of routers, intelligent hubs, etc. that are relay devices, ensuring safe and reliable communication. Can be done.

  According to the second and fifth inventions, since one communication apparatus determines that the network is composed of only one communication apparatus and a relay apparatus, one communication apparatus is another communication apparatus. Even if the communication is performed, it is always possible to communicate via the relay device and to perform an audit process such as packet filtering, and it is possible to perform a safe and reliable communication.

  According to the third and sixth inventions, when there is no other communication device in the network address part including the power-of-two host addresses, one communication device is a communication device and a relay device with one network. Therefore, even if one communication device communicates with another communication device, it always communicates via the relay device and performs audit processing such as packet filtering. It is possible to perform secure and reliable communication.

  Hereinafter, the present invention will be specifically described with reference to the drawings showing embodiments thereof.

(Embodiment 1)
FIG. 1 is a block diagram illustrating the overall configuration of a network system according to Embodiment 1 of the present invention. In the first embodiment, a LAN environment connected using Ethernet (registered trademark) is assumed, and a router 1 as a relay device and a plurality of communication devices 2 to be managed by the router 1 are used. Are connected via the LAN 3. The router 1 is connected to the Internet 5 via a communication line 4 and can be connected to an external network. As an operating system, Windows (registered trademark) (R) is introduced into the communication devices 2, 2,.

  FIG. 2 is a block diagram showing the configuration of the router 1. The router 1 includes at least a CPU 11, a RAM 12, and communication interfaces 13a and 13b. The RAM 12 includes a routing table 121 that stores address division information for controlling information for controlling communication addresses, computer viruses, worms, and the like. A filtering table 122 used for detection and removal is provided.

  The CPU 11 is connected to the above-described hardware units of the router 1 via the internal bus 14, and controls the above-described hardware units and transmits a communication packet destination according to the routing table 121 stored in the RAM 12. And the presence / absence of an abnormal packet is detected and removed according to the filtering table 122.

  The RAM 12 also stores temporary data generated when the software is executed. The communication interface 13 a is connected to the internal bus 14 and transmits / receives communication packet information to / from different network environments via the communication line 4. The communication interface 13b is connected to the internal bus 14, and transmits / receives communication packet information in the same network via the LAN 3.

  FIG. 3 is a block diagram illustrating a configuration of the communication device 2. The communication device 2 includes at least a CPU 21, a storage device 22, a RAM 23, a display unit 24, an input unit 25, an auxiliary storage device 26, and a communication interface 27. The storage device 22 controls an operating system, a control program, and a communication address. Address division information for controlling information is stored. The address division information stored in the communication device 2 is specifically netmask information, and divides an IP address, which is a unique address, into a network address portion and a host address portion. The content of the address division information is different for each communication device 2.

  The CPU 21 is connected to the above-described hardware units of the communication device 2 via the internal bus 28, and controls the above-described hardware units and controls programs or auxiliary programs stored in the storage device 22 such as a hard disk. Various software functions are executed in accordance with a control program introduced into the storage device 22 using a (portable) recording medium such as a CD-ROM or DVD via the storage device 26. Further, the network address portion is calculated using the address division information stored in the storage device 22, and data is transmitted and received between devices recognized as the same network.

  The RAM 23 is composed of a DRAM or the like, and stores temporary data generated when the software is executed.

  The display unit 24 is a display device such as a liquid crystal display device or a CRT display, and displays a communication state, a screen that prompts the user to input an operation, and displays image data. The input unit 25 is an input medium such as a keyboard and a mouse having character keys, numeric keys, various function keys, and the like necessary for operating the communication device 2.

  The communication interface 27 is connected to the internal bus 28 and transmits / receives communication packet information from the outside via the LAN 3.

  The operation of communication processing between the communication devices 2 and 2 in the network system having the above-described configuration will be described below. FIG. 4 is a diagram showing a relationship of IP addresses with the communication devices 2, 2,... And the router 1 in the network system according to the first embodiment of the present invention.

  In FIG. 4, the network configuration information applied to the communication interfaces 13a and 13b of the router 1 is not different from the conventional setting. That is, the IP address of LAN3 to be connected is 256 from 192.168.1.0 to 192.168.1.255, and the devices to be connected to LAN3 are 192.168.1.1 to 192.168 .. Have any IP address in the range of 1.254. Note that 192.168.1.1 is assigned as the IP address indicating the router 1.

  When the router 1 has a DHCP server function and automatically assigns an IP address to the communication device 2a on which Windows (registered trademark) (R) operates as an operating system, 192.168.1.2 to 192.168. 1. Select one unused IP address from 1.254, for example, 192.168.1.50. The IP address of the communication device 2a is designated as 192.168.1.50, the netmask is set to 255.255.255.255, and the default gateway address 192.168.1.1 is transmitted to the communication device 2a.

  In this way, for example, when the communication device 2a attempts to transmit an IP packet, it is determined that the communication device 2a is connected to a different physical network except when the transmission destination is the communication device 2a. For example, when the communication device 2b is the transmission destination, the network to which the communication device 2a is connected is the netmask 255.255.255.255, so the size of 192.168.1.50 to 192.168.1.50 is set. Is recognized as a network having Therefore, since it is determined that the network address is different from the IP address 192.168.1.51 of the communication device 2b, direct communication cannot be performed. Therefore, the IP packet is transferred to the default gateway 192.168.1.1 and arrives at the router 1.

  Therefore, even when transmission is performed from the communication device 2 a to the other communication devices 2, 2,..., Communication is always performed via the router 1. After auditing according to the settings and confirming that the data is normal, the communication packet can be routed to the original destination IP address.

  For the communication apparatus 2a, the default gateway 192.168.1.1 does not exist within the range of the directly connected network 192.168.1.50 to 192.168.1.50. However, in an operating system that does not validate network configuration information, such as Windows (registered trademark) (R), it is transmitted unconditionally to the IP address set as the default gateway. Therefore, even when the transmission source communication device 2 a transmits a packet to another communication device 2 b directly connected via the LAN 3, the communication device 2 a can always communicate via the router 1. It is possible to perform processing such as packet filtering.

  Therefore, even when the communication device 2a infected with a virus, a worm, etc. brought into the LAN from the outside communicates with another communication device 2b connected on the LAN having the same physical network. It will always go through the audit process in the router 1, and when the communication packet arrives at the router 1, it can execute appropriate processes such as removing viruses, worms, etc., and it is safer and more reliable. Communication can be performed.

(Embodiment 2)
In the second embodiment, as in the first embodiment, a LAN environment connected using Ethernet (registered trademark) is assumed, and the router 1 that is one relay device and the management target of the router 1 are used. A plurality of communication devices 2, 2,... Are connected via a LAN 3. The router 1 is connected to the Internet 5 via the communication line 4 and can be connected to an external network. As an operating system, Linux is introduced into the communication devices 2, 2,. Note that the operating system is not limited to Linux, and may be an operating system for confirming network configuration information, for example, MacOSX®.

  The operation of communication processing between the communication devices 2, 2,... In the network system having the above-described configuration will be described below. FIG. 5 is a diagram showing a relationship of IP addresses with the communication devices 2, 2,... And the router 1 in the network system according to the second embodiment of the present invention.

  As shown in FIG. 5, the network configuration information applied to the communication interface 13 of the router 1 is not different from the conventional setting. That is, the IP address of the LAN 3 to be connected is 256 from 192.168.1.0 to 192.168.1.255, and the devices connected to the LAN 3 are 192.168.1.1 to 192.168.1. Have any IP address in the range of .254. 192.168.1.1 is assigned as an IP address indicating the router 1.

  When the router 1 has a DHCP server function and automatically assigns an IP address to the communication device 2a, one unused IP address is assigned from 192.168.1.5 to 192.168.1.253, 192.168.1. n (n = 4m + 1, where m and n are natural numbers) is assigned. For example, the IP address of the communication device 2a that selects 192.168.1.5 is specified as 192.168.1.5, the netmask is set to 255.255.255.252, and the IP address is set as the default gateway address. 192.168.1.6 with 1 added to the end is transmitted to the communication device 2a. In addition, the IP address 192.168.1. k (k = 4m, 4m + 1, 4m + 2, 4m + 3, where k and m are natural numbers) is not assigned to the other communication devices 2, 2,.

  By doing so, for example, when the communication device 2a attempts to transmit an IP packet, it is determined that the transmission destination is connected to a different physical network, except when the transmission destination is the communication device 2a. . For example, when the communication device 2b is the transmission destination, the network to which the communication device 2a is connected is the netmask 255.255.255.252, so the size is between 192.168.1.4 and 192.168.1.7. 4 network. The addresses of the other communication devices 2, 2,... Are assigned addresses outside this range. Therefore, it is determined that the IP address 192.168.1.9 of the communication device 2b is a network that cannot communicate directly, and the communication device 2a transfers the IP packet to the default gateway 192.168.1.6.

  A device having the address 192.168.1.6 does not exist on the LAN 3, but when the communication device 2a makes an ARP request on the LAN 3 to search for 192.168.1.6, the relay device 1 Respond with the MAC address MR. Therefore, the communication device 2a assumes that MR is the MAC address of the default router, and transmits a packet to the MR.

  Therefore, even when transmission is performed from the communication device 2 a to the other communication devices 2, 2,..., Communication is always performed via the router 1. After auditing according to the settings and confirming that the data is normal, the communication packet can be routed to the original destination IP address.

  As a result, even in the case of an operating system that validates network configuration information like Linux, the transmission source communication device 2a has only itself, a default router, and two unused addresses in the connected physical network. Since it is erroneously recognized as being present, the transmission source communication device 2a always communicates via the router 1 even when transmitting a packet to the communication device 2b directly connected via the LAN 3. Processing such as packet filtering can be performed on the communication packet.

  Therefore, even when a communication device 2a infected with a virus, a worm or the like brought into the LAN 3 from the outside communicates with another communication device 2b connected to the LAN 3 as a transmission source, It will go through the audit process in the router 1, and when the communication packet arrives at the router 1, it can execute appropriate processes such as removing viruses, worms, etc. Can be done.

  In the second embodiment, a case where one communication apparatus is recognized in the network configuration information on the communication apparatus side so as to be included in a network having four IP addresses has been described. The number of addresses included in is not limited to four, but may be any number that can be network masked by two or more, that is, a power of two. However, among the addresses included in one logical network, only one address can be assigned to the communication device, and the others need not be used.

  In the first and second embodiments, the case where the router 1 has a communication packet audit function has been described. However, the audit process is not limited to the router 1, and a dedicated monitoring device is used. It may be provided separately on the LAN 3. In this case, the communication apparatus that is the transmission source sets the network configuration information so as to recognize that the transmission is made to the IP address of the monitoring apparatus.

(Embodiment 3)
As in the second embodiment, the third embodiment assumes a LAN environment that is connected using Ethernet (registered trademark), and is a router 1 that is one relay device and a management target of the router 1. Communication devices 2, 2,... Are connected via a LAN 3. The router 1 is connected to the Internet 5 via a communication line 4 and can be connected to an external network. As an operating system, Linux is introduced into the communication device 2a, and Windows (registered trademark) is introduced into the communication device 2b. The communication device 2c is a scanner device.

  The operation of communication processing between the communication devices 2, 2,... In the network system having the above-described configuration will be described below. FIG. 6 is a diagram showing the IP address relationship with the communication devices 2, 2,... And the router 1 in the network system according to the third embodiment of the present invention.

  In FIG. 6, the network configuration information applied to the communication interface 13 of the router 1 is not different from the conventional setting. That is, the IP address of LAN3 to be connected is 256 from 192.168.1.0 to 192.168.1.255, and the devices to be connected to LAN3 are 192.168.1.1 to 192.168 .. Have any IP address in the range of 1.254. 192.168.1.1 is assigned as the IP address indicating the router 1.

  The address assignment table in the router 1 is an area for Windows (registered trademark) (R) 192.168.1.50 to 192.168.1.127 (netmask 255.255.255.255), other OS 192.168.1.128 to 192.168.1.251 (net mask 255.255.255.252) as the application area, and 192.168.1.2 to 192.168.8.1. 49, Mc is registered as a non-applicable device MAC address.

  When the router 1 has a DHCP server function and automatically assigns an IP address to the communication device 2a, it knows that it is Windows (registered trademark) from the operating system information included in the DHCP request from the communication device 2. Can do. Therefore, the router 1 selects one unused IP address from 192.168.1.50 to 192.168.1.127, for example, 192.168.1.50. The router 1 designates the IP address of the communication device 2a as 192.168.1.50, sets the netmask to 255.255.255.255, and sets 192.168.1.1 as the default gateway address to the communication device 2a. Send.

  When the router 1 has a DHCP server function and automatically assigns an IP address to the communication device 2b, it can be recognized that the router 1 is Linux by operating system information included in the DHCP request from the communication device 2. Therefore, one unused IP address from 192.168.1.128 to 192.168.1.251, 192.168.1. n (n = 4m + 1, where m and n are natural numbers) is assigned. For example, the router 1 that selects 192.168.1.129 specifies the IP address of the communication device 2b as 192.168.1.129, sets the netmask to 255.255.255.252, and sets the IP address as the default gateway address. 192.168.1.130 with 1 added to the end of the address is transmitted to the communication device 2b. Also, the IP addresses 192.168.1.128 to 192.168.1.131 are not assigned to the other communication devices 2, 2,.

  When the router 1 has a DHCP server function and automatically assigns an IP address to the communication device 2c, the source MAC address information included in the DHCP request from the communication device 2 is Mc. I can know. Accordingly, one unused IP address, for example, 192.168.1.2 is selected from 192.168.1.2 to 192.168.1.49. The router 1 specifies the IP address of the communication device 2b as 192.168.1.2, sets the netmask to 255.255.255.0, and transmits the default gateway address 192.168.1.1 to the communication device 2c. To do. This network configuration information is not different from conventional settings.

  In this way, when the communication devices 2a and 2b try to transmit an IP packet, it is determined that the transmission destination is connected to a different physical network, except when the transmission destination is itself. 1 is transmitted. When the communication device 2c tries to send an IP packet, it is sent directly if the destination is connected to the LAN 3, and sent to the router 1 otherwise.

  Therefore, even in a network system in which communication devices 2, 2,... In which a plurality of operating systems are installed are mixed, all packets are transmitted via the router 1 only to devices that require packet inspection at the router 1. It becomes possible.

  Therefore, even when a communication device 2a infected with a virus, a worm or the like brought into the LAN 3 from the outside communicates with another communication device 2b connected to the LAN 3, When the communication packet arrives at the router 1 through the audit process in the router 1, it is possible to execute an appropriate process such as identifying and discarding the packet transmitted by a virus, worm or the like. Therefore, safer and more reliable communication can be performed. Further, the communication device 2c, which is not related to viruses, worms, etc., can directly send packets to other communication devices, thereby reducing the load on the router 1.

It is a block diagram explaining the whole structure of the network system which concerns on Embodiment 1 of this invention. It is a block diagram which shows the structure of a router. It is a block diagram which shows the structure of a communication apparatus. It is a figure which shows the relationship of the IP address with the communication apparatus and router in the network system which concerns on Embodiment 1 of this invention. It is a figure which shows the relationship of the IP address with the communication apparatus and router in the network system which concerns on Embodiment 2 of this invention. It is a figure which shows the relationship of the IP address with the communication apparatus and router in the network system which concerns on Embodiment 3 of this invention.

Explanation of symbols

1 router 2, 2a, 2b, 2c communication device 3 LAN
11, 21 CPU
12, 23 RAM
13a, 13b, 27 Communication interface 14, 28 Internal bus 22 Storage device 24 Display unit 25 Input unit 26 Auxiliary storage device

Claims (6)

A plurality of communication devices capable of communicating with each other and a relay device connected to an external network,
In each of the communication devices and the relay device, a network system having a unique address and address division information for dividing the address into a network address portion and a host address portion.
The network system, wherein the communication device and the relay device have different address division information, and are communicated between the communication devices via the relay device.   2. The network system according to claim 1, wherein the address division information possessed by one communication apparatus is information having a unique address possessed by the one communication apparatus as one network address part.   2. The network according to claim 1, wherein said address division information possessed by one communication device is such that a network address portion of a unique address possessed by said one communication device includes a power-of-two host address. system. A plurality of communication devices capable of communicating with each other and a relay device connected to an external network,
In the communication method on the network, each communication device and the relay device each have a unique address and address division information for dividing the address into a network address portion and a host address portion.
A communication method characterized in that the communication device and the relay device have different address division information, and when communication is performed between the communication devices, the communication device passes through the relay device.   5. The communication method according to claim 4, wherein the address division information possessed by one communication apparatus is information having a unique address possessed by the one communication apparatus as one network address part.   5. The communication method according to claim 4, wherein in the address division information possessed by one communication device, the network address portion of the unique address possessed by the one communication device includes a power of two host addresses.

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