JP6261805B2 - Network system, center side router, base side router, NAPT table update method - Google Patents

Description

  The present invention relates to a network system in which a center side router and a base side router are connected to each other and communicate by NAPT, and a method of updating a NAPT table related to a NAPT table used for NAPT.

  First, as shown in FIG. 13, a network system is assumed in which a center and a plurality of bases are connected by a network. FIG. 13 shows a general network system in which a center 50 and three bases 60A to 60C are connected.

  In FIG. 13, a center communication device 51 is installed in the center 50, and base communication devices 61A to 61C are installed in the bases 60A to 60C, respectively. The center communication device 51 and the base communication devices 61A to 61C are connected to each other. Communicate between the two. There is no communication between the base communication devices 61A to 61C.

  Further, the center communication device 51 identifies the base communication devices 61A to 61C by IP addresses, and the correspondence between the bases 60A to 60C and the IP addresses is recorded in the IP address list 52 which is a database installed in the center 50. Has been.

  Here, in this network system, a case where a plurality of base communication devices are installed at one base is considered. Note that one global IP address is assigned to one site. At this time, since a plurality of base communication devices are provided for one global IP address, there is a problem that the base communication device cannot be simply identified by the IP address.

  Conventionally, NAPT (Network Address Port Translation) is known for this problem. NAPT is a technique for converting a communication IP address and port number, and allows one global IP address to correspond to a plurality of private IP addresses.

  Hereinafter, a network system that performs communication using NAPT will be described with reference to FIG. In FIG. 14, two base communication devices 1 and 2 are provided in the base 60A having the global IP address 203.0.113.10. Here, it is assumed that the base communication device 1 has a private IP address of 192.168.0.10 and the base communication device 2 has a private IP address of 192.168.0.20.

  The IP address / port list 53 installed in the center 50 records the correspondence between the base communication devices 1 and 2 and the base 60B of the base 60A, and the IP address and port number. Further, the router 62A of the base 60A has a NAPT function, and the settings shown in Table 1 are set in the NAPT table 63A.

  At this time, access to the port number 10000 of the global IP address 203.0.113.10 is made to the base communication device 1 having the private IP address 192.168.0.10, and access to the port number 10001 is made to the private IP address. It can be assigned to each base communication device 2 having the address 192.168.0.20. In this way, by performing communication using different port numbers, a plurality of base communication devices can be identified by one global IP address.

  However, when performing communication using NAPT, communication cannot be managed using only the IP address, and different port numbers will be used depending on the installation status even if the same base communication device is used. For this reason, it may be necessary to modify the center communication device 51 such as a communication protocol or an application.

  On the other hand, by installing routers having a NAPT function in both the center and the base, and performing two-step IP address / port number conversion processing, communication can be managed only by the IP address. Can communicate with the base communication device without using a different port number for each communication partner. This is called a two-stage NAPT system.

  Hereinafter, a network system that performs communication by the two-stage NAPT method will be described with reference to FIG. In FIG. 15, two base communication devices 1 and 2 are provided in the base 60A having the global IP address 203.0.113.123. Here, it is assumed that the base communication device 1 has a private IP address of 192.168.0.10 and the base communication device 2 has a private IP address of 192.168.0.20.

  Further, a center side router 54 and a site side router 64A having a NAPT function are installed in the center 50 and the site 60A, respectively. Note that the center communication device 51 and the base communication device 61A communicate with each other using the port number 10000. Further, the center side router 54 and the base side router 64A have a NAPT table 55 and a NAPT table 65A, respectively.

  Here, a case where the center communication device 51 communicates with the base communication device 2 will be described as an example of communication using the two-stage NAPT method. First, the center communication device 51 refers to the IP address list 56 installed in the center 50, and acquires the IP address of the base communication device desired to communicate. Table 2 shows the IP address list 56.

  In the two-stage NAPT method, a temporary IP address is assigned to the base communication device in the IP address list 56. Here, 10.0.0.10 is assigned to the base communication device 1 and 10.0.0.020 is assigned to the base communication device 2. These are irrelevant to the actual IP addresses of the bases and base communication devices, are unique addresses in the IP address list 56, and are routed to the center side router 54 when sent from the center communication device 51. Any address can be used.

  Since the IP address of the base communication device 2 is 10.0.0.20 from the IP address list 56, the center communication device 51 transmits a communication packet addressed to the IP address 10.0.0.20. Table 3 shows communication packets transmitted by the center communication device 51.

  In Table 3, since the center communication device 51 and the base communication device 61A communicate using the port number 10,000, the destination port number is 10,000. The transmission source IP address is the global IP address 203.00.113.1 of the center 50, and the transmission source port number is 10000 here.

  The communication packet sent from the center communication device 51 reaches the center side router 54, and the destination IP address and port number are converted by the NAPT table 55. Table 4 shows the NAPT table 55 of the center side router 54.

  The NAPT table 55 of the center side router 54 is set to convert the temporary IP address assigned to the base communication devices 1 and 2 into the global IP address of the original base 60A. In addition, the destination IP address before conversion needs to correspond to the temporary IP address assigned to the base communication devices 1 and 2 of the base 60A. At this time, a different port number is set for each base communication device as the converted port number.

  Table 5 shows a communication packet after passing through the center side router 54. Comparing Table 5 with Table 3, the destination IP address and the destination port number are converted by the NAPT table 55 of the center side router 54.

  Next, the communication packet that has passed through the center side router 54 reaches the base side router 64A of the base 60A. In the base side router 64A, a NAPT table 65A shown in Table 6 is set so that communication packets are distributed to each base communication device by a port number.

  Since the destination port number of the communication packet that has reached the base side router 64A is 10001, the NAPT table 65A converts it into the port number 10000 of the IP address 192.168.0.20 and sends it to the base communication device 2. Table 7 shows a communication packet after passing through the base side router 64A.

  As a result, communication can be managed using only the IP address, and the center communication device does not use a different port number for each communication partner, that is, without changing the port number for each base communication device. Can communicate with the device.

  As a related technique, when a tunnel generation request message for another private network connected to the public network is received from a host connected to the private network, it communicates with the gateway of the other private network to communicate with the VPN (Virtual Private Network). ) When a private network and another private network have the same network address, or when one private network contains the network address of another private network, the two private networks A network connection that creates a new network address table to use a different network address, translates and forwards data packets forwarded from a host connected to the private network or other private networks based on the new network address table Device knows (For example, refer to Patent Document 1).

JP 2004-229299 A

  However, in the two-stage NAPT method, it is necessary to manage the NAPT tables of both the center side router and the base side router, and there is a problem that the management load increases. That is, since the port number converted by the center side router is restored to the original by the base side router, the port number cannot be accurately converted unless the port numbers to be converted are matched in both NAPT tables. The communication device and the base communication device cannot communicate.

  In addition, it is necessary to update the NAPT table each time a base is added or deleted, or a base communication device is added or deleted. When the NAPT table is manually updated each time, there is a high risk of error. There is also a problem that the workload becomes large.

  In Patent Document 1, a new network address table is generated so that two private networks use different network addresses in the VPN tunnel, and addresses are converted based on this table. Converting port numbers, such as schemes, is not shown.

  The present invention has been made to solve the above-described problems, and reduces the management load of the NAPT table by setting and updating the NAPT table of the center side router and the base side router in synchronization. An object of the present invention is to obtain a network system capable of preventing errors and reducing the work load.

The network system according to the present invention is a network system in which a center-side router and a base-side router are connected to each other and perform communication by NAPT, and the center-side router includes device information of communication equipment connected to the base-side router. Based on this, the temporary port number used in the communication between the center side router and the base side router is set, the NAPT table is updated using the temporary port number, and the temporary port number is transmitted to the base side router. The base-side router updates its NAPT table using the received temporary port number, and updates the NAPT table of the center-side router and the NAPT table of the base-side router in synchronization .

  The network system according to the present invention is a network system in which a center side router and a base side router are connected to each other and communicate by NAPT. The center side router and the base side router are connected to the base side router, respectively. There is a common table for the device type and the maximum number of installed communication devices, and the base side router uses its table based on the device type and the number of communication devices actually connected to the base side router. The NAPT table is updated, and the device type and number of communication devices actually connected to the base router are transmitted to the center router. The center router receives the communication devices actually connected to the received base router. Updates its own NAPT table using a table based on device type and number

According to the network system of the present invention, the center router sets a temporary port number used for communication between the center router and the base router based on the device information of the communication device connected to the base router. Then, the temporary port number is used to update its own NAPT table, and the temporary port number is transmitted to the base router. The base router updates the own NAPT table using the received temporary port number.
Also, the center side router and the base side router have a common table for the device type and the maximum number of installed communication devices connected to the base side router, respectively, and the base side router is actually connected to the base side router. Based on the device type and the number of communication devices, the table is used to update its own NAPT table, and the device type and the number of communication devices actually connected to the base router are transmitted to the center router. The side router updates its NAPT table using the table based on the device type and number of communication devices actually connected to the received base side router.
Therefore, by updating the NAPT table of the center side router and the base side router in synchronization, it is possible to reduce the management load of the NAPT table and prevent a setting error and reduce the work load.

1 is a block configuration diagram showing a network system according to Embodiment 1 of the present invention. In the network system concerning Embodiment 1 of this invention, it is explanatory drawing which shows the input data which a system administrator inputs. It is a flowchart which shows the registration process of the data in the network system which concerns on Embodiment 1 of this invention. It is explanatory drawing which shows the input data in the case of deleting data in the network system which concerns on Embodiment 1 of this invention. It is explanatory drawing which shows the input data in the case of deleting data in the network system which concerns on Embodiment 1 of this invention. It is explanatory drawing which shows the input data in the case of deleting data in the network system which concerns on Embodiment 1 of this invention. It is explanatory drawing which shows the input data in the case of dynamically registering a port number in the network system concerning Embodiment 1 of this invention. It is explanatory drawing which shows the communication sequence in the case of registering a port number dynamically in the network system which concerns on Embodiment 1 of this invention. It is a block block diagram which shows the network system which concerns on Embodiment 2 of this invention. In the network system concerning Embodiment 2 of this invention, it is explanatory drawing which shows the input data which an equipment installation worker inputs. It is a block block diagram which shows the network system which concerns on Embodiment 3 of this invention. It is a flowchart which shows the process at the time of detecting a global IP address change in the network system which concerns on Embodiment 3 of this invention. 1 is a block configuration diagram showing a general network system that connects a center and a plurality of bases via a network. FIG. 1 is a block configuration diagram illustrating a network system in which a center and a plurality of bases are connected by a network and communication is performed by NAPT. 1 is a block configuration diagram illustrating a network system in which a center and a plurality of bases are connected by a network and communication is performed by a two-stage NAPT method.

  Hereinafter, preferred embodiments of a network system and a NAPT table update method according to the present invention will be described with reference to the drawings. In the drawings, the same or corresponding parts will be described with the same reference numerals.

Embodiment 1 FIG.
1 is a block diagram showing a network system according to Embodiment 1 of the present invention. In FIG. 1, a center side router 10 and a base side router 20 communicate with each other by a network I / F (interface) 11 and a network I / F 21 provided in each.

  In addition to the NAPT function 12 and the NAPT table 13, the center side router 10 includes a data input unit 14 that receives input of an IP address / port number, an IP / port correspondence table 15 that stores input data, and a base side router 20. A data transmission unit 16 that transmits data is included.

  In addition to the NAPT function 22 and the NAPT table 23, the base side router 20 has a data receiving unit 24 that receives data from the center side router 10.

  Here, consider a case where a base A (not shown) having a global IP address 203.0.113.123 is newly added to the base-side router 20. Note that the base A is provided with two base communication devices 1 and 2 as shown in FIG.

  Further, it is assumed that the base communication device 1 has a private IP address of 192.168.0.10 and the base communication device 2 has a private IP address of 192.168.0.20. In communication between the center communication device and the base communication device, two port numbers 12300 and 23400 are used, and the base communication device waits for a connection.

  In the network system configured as described above, first, the system administrator inputs necessary data to the center side router 10. The input method does not matter. Specific input data input by the system administrator is shown in FIG.

  In FIG. 2, there are two processing contents, “input” and “deletion”. The “deletion” will be described later. The temporary IP address input by the system administrator may be anything as long as it is not registered in the NAPT table 13 of the center side router 10.

  Subsequently, the center side router 10 receiving the data registers the data in the IP / port correspondence table 15. Table 8 shows the IP / port correspondence table 15.

  In the IP / port correspondence table 15 shown in Table 8, the global IP address of the base is the main entry, and the actual IP address and temporary IP address of the base communication device installed in the base are recorded below it. Yes. Further, an actual port number and a temporary port number used for communication are recorded for each base communication device.

Next, the procedure of data registration processing will be described with reference to the flowchart shown in FIG.
First, it is determined whether or not the global IP address of the base is already registered in the IP / port correspondence table 15.

Here, if the global IP address of the site has already been registered, the entry is set as a target entry, and data is added by the following procedure.
On the other hand, if the global IP address of the site is not registered, a new target entry is created and data is registered according to the following procedure.

  Subsequently, one piece of unprocessed base communication device information is extracted from the input data, and it is determined whether or not the same pair as the pair of the real IP address and the temporary IP address of the base communication device is already registered in the target entry. .

Here, if the same pair as the pair of the real IP address and the temporary IP address of the base communication device is already registered, the process proceeds to the next procedure without doing anything.
On the other hand, when the same pair as the pair of the real IP address and the temporary IP address of the base communication device is not registered, the pair of the real IP address and the temporary IP address is registered.

  Next, an unregistered one in the port number list is added as a real port number to the pair of the real IP address and the temporary IP address found or registered in the above procedure. At this time, one temporary port number is assigned to each real port number. Here, the temporary port number may be anything as long as it is unique within the entry of the global IP address of the base. In Table 8, for example, assignment is performed by incrementing one by one from 10,000.

  Table 8 shows the IP / port correspondence table 15 when the data shown in FIG. In Table 8, it is assumed that the entry of the global IP address 203.0.113.123 of the base was not originally present.

  Subsequently, when the IP / port correspondence table 15 is changed, the center side router 10 updates its NAPT table 13 and transmits the IP / port correspondence table 15 to the base side router 20.

  At this time, the center side router 10 sets the temporary IP address and the real port number as the values before conversion for each entry registered in the IP / port correspondence table 15, and the global IP address and temporary port of the base. Set the number as the converted value. Table 9 shows the NAPT table 13 of the center side router 10 created from the IP / port correspondence table 15 of Table 8.

  The base-side router 20 that has received the IP / port correspondence table 15 sets the global IP address of the base in the table as the destination IP address before conversion, sets the temporary port number as the port number before conversion, The NAPT table 23 is constructed by setting the IP address as the converted destination IP address and setting the actual port number as the converted port number. Table 10 shows the NAPT table 23 of the base router 20.

  Thereby, the center side router 10 and the base side router 20 can update the NAPT table in synchronization.

  If there is no base or the base communication device is removed, the entry is deleted when it is desired to delete the corresponding entry from the IP / port correspondence table 15. For example, when it is desired to delete the port number 23400 of the base communication device 192.168.0.10/10.0.0.1 from the IP / port correspondence table 15 of Table 8, the system administrator must Enter the input data shown. Table 11 shows the IP / port correspondence table 15 after the port number is deleted.

  Further, when it is desired to delete the base communication device 192.168.0.10/10.0.0.1 itself from the IP / port correspondence table 15 in Table 8, the system administrator inputs the input shown in FIG. Enter the data. Table 12 shows the IP / port correspondence table 15 after the base communication device is deleted.

  Further, when it is desired to delete the site 203.0.113.123 from the IP / port correspondence table 15 in Table 8, the system administrator inputs the input data shown in FIG. In this case, the base communication device is also deleted.

  In this way, the NAPT table 13 of the center side router 10 and the NAPT table 23 of the site side router 20 can be synchronized and updated simply by inputting input data to the center side router 10, so that the management of the NAPT table is possible. In addition to reducing the load, setting errors can be prevented and the work load can be reduced.

  In the above-described method, the NAPT table needs to be updated every time a port number used in the base communication device is added or changed. In addition, it is necessary to know all the port numbers to be used for each type of base communication device.

  Therefore, as a modification of the first embodiment, a method for eliminating the need to specify a port number by dynamically generating an entry in the NAPT table will be described below. Specifically, in this modification, the system administrator inputs the input data shown in FIG.

  Subsequently, the center side router 10 receiving the data registers the data in the IP / port correspondence table 15. Table 13 shows an IP / port correspondence table 15 in this modification. In Table 13, the actual port number and the temporary port number are blank.

  Next, when the IP / port correspondence table 15 is registered, the center side router 10 generates a NAPT table 13 based on the IP / port correspondence table 15. Table 14 shows the NAPT table 13 in this modification. In Table 14, the port numbers before and after conversion remain blank.

  In this modification, the NAPT table 23 of the base router 20 is not constructed at this stage.

  Subsequently, in this state, it is assumed that communication has occurred from the center communication device to the port number 12300 of the base communication device 192.168.0.10/10.0.0.1. Hereinafter, the communication sequence in this case will be described with reference to FIG.

  At this time, the center side router 10 that has received the communication packet dynamically registers the port number in the entry of the destination IP address 10.0.0.1 of the NAPT table 13. Table 15 shows the NAPT table 13 after dynamically adding the port numbers in this modification.

  In Table 15, the destination port number of the communication packet is set to the port number before conversion, and a port number that is not duplicated in the NAPT table 13 is appropriately assigned to the port number after conversion. In Table 15, 10000 is assigned as the port number after conversion.

  Next, the center side router 10 transmits an entry registration request to the base side router 20 before transferring the communication packet. The entry registration request includes the global IP address 203.0.113.123 of the base, the pre-conversion port number 10000, the real IP address 192.168.0.10, and the real port number 12300.

  Further, when receiving the entry registration request, the base side router 20 dynamically registers an entry in the NAPT table 23 and transmits an entry registration notification to the center side router 10. Table 16 shows the NAPT table 23 of the base router 20 after receiving the entry registration request in this modification.

  Subsequently, the center-side router 10 that has received the entry registration notification executes a NAPT process on the communication packet from the center-side communication device, and then forwards the packet to the base-side router 20. At this time, the entries dynamically added by the center side router 10 and the base side router 20 may be deleted after a certain timeout period after they are no longer used for communication.

  This modification eliminates the need for the port number list to be specified in advance when the system administrator inputs data, reducing the management load on the NAPT table and reducing the work load by preventing setting errors. can do.

As described above, according to the first embodiment, the center side router is a temporary port used for communication between the center side router and the site side router based on the device information of the communication device connected to the site side router. Set the number, update its own NAPT table using the temporary port number, send the temporary port number to the base router, and the base router updates its own NAPT table using the received temporary port number To do.
Therefore, by updating the NAPT table of the center side router and the base side router in synchronization, it is possible to reduce the management load of the NAPT table and prevent a setting error and reduce the work load.

Embodiment 2. FIG.
In the first embodiment, the system administrator inputs necessary data to the center side router. On the other hand, if the type, maximum installation number, and private IP address of each base communication device installed at the base are determined in advance, the temporary port number correspondence table can be shared between the center side router and the base side router. For example, only the type and the number of base communication devices to be installed are notified from the base side router to the center side router, whereby both NAPT tables can be synchronized and updated.

  Here, for example, it is assumed that there are three types of devices, device A, device B, and device C, and that device A is installed at a maximum of 4 devices, and device B and device C are installed at a maximum of 2 devices each. Also, assume that device A uses two types of port numbers, 12300 and 23400, device B uses 5678, and device C uses 9012.

  The first device A is assigned a private IP address 192.168.0.10, the second device is assigned 192.168.0.11 and the third device is 192.168.8.0. 12 is assigned, and 192.168.0.13 is assigned to the fourth unit. The private IP addresses to be assigned are similarly determined for the devices B and C. Table 17 shows a temporary port number correspondence table in which a temporary port number is uniquely assigned to each entry obtained in this way.

  FIG. 9 is a block diagram showing a network system according to Embodiment 2 of the present invention. In FIG. 9, the center side router 10 has a data receiving unit 16 that receives data from the base side router 20 and a temporary port number correspondence table 17 in addition to the NAPT function 12 and the NAPT table 13.

  In addition to the NAPT function 22 and the NAPT table 23, the site-side router 20 transmits data to the data input unit 25, the temporary port number correspondence table 26, and the center-side router 10 that receive input of the type and number of site communication devices. The data transmission unit 27 is provided. Here, the temporary port number correspondence table 17 and the temporary port number correspondence table 26 are shared in advance.

  Consider a case where two devices A and one device B are added to a base having a global IP address 203.0.113.123 in the network system having the above configuration. First, the equipment installation worker inputs the type and number of base communication equipment to the base-side router 20. The input method does not matter. Specific input data input by the equipment installation worker is shown in FIG.

  The base side router 20 updates the NAPT table 23 based on the input data and the temporary port number correspondence table 26. Specifically, since there are two devices A and one device B, refer to the entry of # 1 and # 2 of device A and the entry of # 1 of device B from the temporary port number correspondence table 26. The private IP address is set as the destination IP address after conversion, the port number is set as the port number after conversion, and the temporary port number is set as the port number before conversion.

  Further, the base router 20 sets the global IP address of the base as the destination IP address before conversion of each entry. Thereby, the NAPT table 23 of the base side router 20 can be updated. Table 18 shows the NAPT table 23 of the base router 20.

  Next, the base side router 20 transmits the input data of the type and number of base communication devices input by the equipment installation worker to the center side router 10. The center side router 10 updates the NAPT table 13 based on the received input data and the temporary port number correspondence table 17.

  Specifically, since there are two devices A and one device B, refer to the entries of # 1 and # 2 of device A and the entries of # 1 of device B from the temporary port number correspondence table 17, The port number is set to the port number before conversion, and the temporary port number is set to the port number after conversion.

  Further, the center side router 10 sets the global IP address of the base as the destination IP address after conversion. This is because the data receiving unit 16 of the center side router 10 can know the global IP address of the base when receiving the input data from the base side router 20 and uses this.

  Further, the center side router 10 assigns a temporary IP address to each device. This temporary IP address may be anything as long as it is unique in the NAPT table 13 of the center side router 10. Here, it is assumed that 10.0.0.1 is assigned to the device A # 1, 10.0.0.2 is assigned to the device A # 2, and 10.0.0.3 is assigned to the device B. Thereby, the NAPT table 13 of the center side router 10 can be updated. Table 19 shows the NAPT table 13 of the center side router 10.

  In this way, the NAPT table 13 of the center side router 10 and the NAPT table 23 of the site side router 20 are synchronized and updated only by inputting the type and number of base communication devices to the base side router 20 as input data. Therefore, it is possible to reduce the management load of the NAPT table and to prevent setting errors and reduce the work load.

As described above, according to the second embodiment, the center side router and the base side router have a common table for the device type and the maximum number of installed communication devices connected to the base side router, respectively. Uses the table to update its NAPT table based on the device type and number of communication devices actually connected to the base side router, and also sets the device type of the communication device actually connected to the base side router. The center side router updates its NAPT table using the table based on the device type and number of communication devices actually connected to the received base side router.
Therefore, by updating the NAPT table of the center side router and the base side router in synchronization, it is possible to reduce the management load of the NAPT table and prevent a setting error and reduce the work load.

Embodiment 3 FIG.
In the first and second embodiments, the case where the global IP address of the base is fixed has been described as an example. However, if the global IP address of the site is not a fixed IP address, the global IP address of the site may be changed during operation of the network system.

  In the third embodiment of the present invention, a method for updating the global IP address of the base after the NAPT table is constructed will be described. This method can be applied to any of the first and second embodiments.

  FIG. 11 is a block diagram showing a network system according to Embodiment 3 of the present invention. 11, this network system basically has the same configuration as that shown in FIG. 15 except that an IP address notification unit 27 is provided in the base router 20.

  In FIG. 11, it is assumed that the NAPT table 13 of the center side router 10 is set as shown in Table 20.

  In Table 20, an item “base ID” is newly added to the NAPT table 13 of the center side router 10. Here, the base ID is an ID for identifying the base, and is a unique value for each base. Further, it is assumed that the NAPT table 23 of the site side router 20 of the site A is set as shown in Table 21.

  Subsequently, in this state, it is assumed that the global IP address of the site A is changed to 203.0.113.124. Hereinafter, a process when a change in the global IP address is detected will be described with reference to FIG.

  At this time, when the base-side router 20 of the base A detects a change in the global IP address, first, the base-side destination IP address in its NAPT table 23 is updated to a new global IP address. Table 22 shows the NAPT table 23 after the change of the base side router 20 of the base A.

  In addition, the IP address notifying unit 27 of the base side router 20 transmits a communication packet including the base ID of the local base to the center side router 10 as an IP address update packet. Note that the IP address notifying unit 27 is not limited to detecting a change in the global IP address, and may acquire an IP address update packet after acquiring the global IP address.

  Next, the center-side router 10 that has received the IP address update packet uses the converted destination IP address of the entry of the designated site ID in the NAPT table 13 as the source address of the received IP address update packet. To the global IP address. Table 23 shows the NAPT table 13 after the change of the center side router 10.

  As described above, when the change of the global IP address is detected, the IP address notification unit 27 transmits the communication packet including the base ID of the local base to the center side router 10 as the IP address update packet. Even if the global IP address is changed, communication can be continued. At this time, since the temporary IP address is not changed, the IP address list 32 of the center side router 10 does not need to be changed.

  The third embodiment can also be used to construct a new NAPT table when a new base is added in the first embodiment. That is, when the NAPT table 13 is constructed by the center side router 10, the destination IP address after conversion is left blank, and the IP address is updated from the site side. It is not necessary for the center router 10 to know the IP address.

Claims (8)

A network system in which a center side router and a base side router are connected to each other, and perform communication by NAPT (Network Address Port Translation),
The center side router sets a temporary port number used for communication between the center side router and the base side router based on device information of a communication device connected to the base side router, and the temporary port number To update its own NAPT table using, and send the temporary port number to the base router,
The base router updates its NAPT table with the received temporary port number ,
A network system for updating the NAPT table of the center side router and the NAPT table of the base side router in synchronization . A center side router applied to the network system according to claim 1,
Based on the device information of the communication device connected to the base side router, a temporary port number used for communication between the center side router and the base side router is set, and the NAPT using the temporary port number is set. A center side router that updates the table and transmits the temporary port number to the base side router. A base router applied to the network system according to claim 1,
When receiving the temporary port number from the center side router, the base side router updates its own NAPT table using the temporary port number. A network system in which a center side router and a base side router are connected to each other and communicate by NAPT,
The center side router and the base side router each have a common table for the device type and the maximum number of installed communication devices connected to the base side router,
The base-side router updates its NAPT table using the table based on the device type and number of communication devices actually connected to the base-side router, and actually connects to the base-side router. The device type and the number of the communication devices that have been sent to the center side router,
The network system in which the center side router updates its NAPT table using the table based on the received device type and number of communication devices actually connected to the base side router. A center side router applied to the network system according to claim 4,
When receiving the device type and number of communication devices actually connected to the base side router from the base side router, based on the device type and number of communication devices actually connected to the base side router, Center side router that updates its own NAPT table. A base router applied to the network system according to claim 4,
Based on the device type and number of communication devices actually connected to the base side router, the NAPT table is updated using the table, and the communication device device actually connected to the base side router is used. A base router that transmits the type and number to the center router. A NAPT table update method executed in a network system in which a center side router and a base side router are connected to each other and communicate by NAPT,
Setting a temporary port number used for communication between the center side router and the base side router based on device information of communication equipment connected to the base side router by the center side router;
The center side router updates its NAPT table with the temporary port number, and transmits the temporary port number to the base side router;
Updating the NAPT table of itself with the temporary port number received by the base side router;
Unrealized, the the center side router NAPT table to synchronize NAPT table of the base side router updates, update method NAPT table. A NAPT table update method executed in a network system in which a center side router and a base side router are connected to each other and communicate by NAPT,
The center side router and the base side router each have a common table for the device type and the maximum number of installed communication devices connected to the base side router,
Updating the NAPT table by using the table based on the device type and the number of communication devices actually connected to the site-side router by the site-side router;
Transmitting the device type and the number of communication devices actually connected to the base side router to the center side router by the base side router;
Updating the NAPT table of itself using the table based on the device type and the number of communication devices actually connected to the base side router received by the center side router;
Of updating NAPT table including

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