JP2005229559A - Ip network communication method and device thereof - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To enable a communication quality between communication devices to be enhanced by enhancing a communication quality of path switchboards located on a communication path, concerning the communication devices for which the enhancement of the communication quality is difficult when only an existing technology is used. <P>SOLUTION: A path switchboard is used having conversion functions of a source and a destination of a packet in an IP network, and a function of controlling a packet conversion rule of the path switchboard. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a communication method between communication devices via a network.

  The main technologies for enhancing the quality of communication in an IP (Internet Protocol) network based on best effort are RSVP (Resource Reservation Protocol), Diffserv (Differential Services), and MPLS (Multiprotocol Label Switch).

  RSVP is used for a purpose in which a router existing between communication devices secures resources for each communication unit. This is a technique for improving communication quality by causing each router to execute communication processing according to the rules determined by RSVP. The communication unit can be specified by, for example, a set of network address and port number of the communication device. However, in this method, each router needs to maintain the communication state for each communication unit and execute communication processing, and it is difficult to execute many communications simultaneously.

  Diffserv is a technology developed to address this problem. In the network of the Diffserv configuration, a certain priority is given to each packet based on the type of the packet, and packet transfer processing is executed based on the priority. Examples of the packet type include a packet including voice data of an IP phone and a packet based on HTTP. A type of communication given a high priority is expected to obtain a higher communication quality than that of a low priority. However, the types of priority given are limited, and resources are not allocated for each communication unit.

MPLS is a technique for adding a label to a packet and transferring the packet along a set route based on the label. By using a label for determining the type of packet, high-speed processing is possible. In addition, it is possible to guarantee communication quality by reserving resources on the route for communication. Effective for building virtual private networks, etc., but requires network administrator work to set up communication paths and reserve resources, making it difficult to guarantee the quality of individual communications in applications where the communication partner changes frequently. . Further, since the entire network existing between communication devices is compatible with MPLS and needs to be operated under a unified management policy, it is difficult to construct a network via different organizations such as the Internet.
“Resource ReServation Protocol (RSVP)”, IETF, 1997, RFC 2205 “An Architecture for Differentiated Services”, IETF, 1998, RFC 2475. "Multiprotocol Label Switching Architecture", IETF, 2001, RFC3031

Problems to be solved by the invention

  In recent years, as represented by remote lectures via IP telephones and the Internet, applications that require service reliability and stable high-quality communication while using IP networks have appeared. However, it is difficult to increase the communication quality between arbitrary communication devices flexibly and reliably in a large-scale network such as the Internet only with the above-described conventional technology. In general, in order to perform communication correctly in an IP network, it is necessary that a communication partner and an intervening network can use the same communication protocol (for example, IPv4 or IPv6). However, the technology related to the Internet is steadily changing, and the network technology to be used and the configuration are often changed. At this time, there may occur a situation in which a device used by the service user needs to be changed, or a change in the service content itself cannot be avoided. In particular, this can be an obstacle to providing a communication device having a limited function such as an IP telephone or providing the same service stably over a long period of time.

Means for solving the problem

  The present invention retains information about a set of path switches that can communicate with a device (hereinafter referred to as a path switch) that has a function of converting a packet source and destination in an IP-based network. Based on the above, the above problem is solved by using an apparatus (hereinafter referred to as a controller) comprising a computer having a function of controlling packet conversion rules of one or more route exchanges. Note that the entire network does not have to be based on the same IP technology, and other types and versions of technologies may be used for communication between devices to be used and communication devices. The function of the controller that controls the packet conversion rule of each route switch may be provided in the route switch without being provided outside the route switch.

  The present invention does not require control of a communication device using a communication method according to the present invention when a failure such as a link disconnection occurs in a communication path or a part of a route switch, and communication performed by the communication device is not necessary. A function for changing the communication path to be used and preventing the communication from being stopped is provided. Further, except when the failure occurs, it is not necessary to control the communication device using the communication method according to the present invention, and further, the communication can be performed without impairing information exchanged by the communication performed by the communication device. A function for changing the communication path to be used is provided. These enhance the reliability of communications using the present invention.

The invention's effect

  In the present invention, by improving the communication quality between the path exchanges located on the communication path, even when communication devices that are difficult to improve the communication quality when using only the existing technology are communicated between them. It is possible to increase. The communication between route exchanges has a clear feature, that is, a set of route exchanges that execute communication, and does not require frequent changes of communication targets compared to general communication. And RSVP can be used to improve quality. A bandwidth can be reserved in the network for the communication according to the present invention, and by changing the bandwidth according to the use state of the communication, the network can be effectively used for both the communication according to the present invention and the general communication. it can. In addition, the technology for improving the communication quality does not need to be the same for the entire network interposed between communication devices, but is used only for a part of the route exchanges, or different for each. Can be. Thereby, the reliability of the entire communication can be increased step by step.

  In the present invention, the route switch controls the communication quality including the bandwidth of each communication passing through the route switch, so that all the routers existing in the network interposed between the communication devices communicate many communication situations. Quality can be controlled on a per-communication basis without having to process every unit.

  In the present invention, for communication devices that exist in networks using different communication protocols such as IPv4 and IPv6, as long as the communication devices can each communicate with at least one route switch, similar communication is provided. Is possible.

  In the present invention, it is possible to use a dedicated communication path for communication between the controller and each path switch. Each route switch retains an identifier for another route switch, and uses the identifier when the controller controls the route switch, thereby saving the bandwidth required for a dedicated communication path. In addition, including a case where a failure occurs in the communication path of the communication device, the communication method according to the present invention is changed to use another communication path with little or no effect on the communication in use. It is possible. Thereby, it becomes possible to improve the reliability of communication.

  In the present invention, it is possible to perform network address resolution by a method different from that of the domain name system (DNS) during communication. Thereby, security can be improved.

  In the present invention, it is not necessary for communication partners to know the position (for example, IP address) on each other's network at the time of communication, making it difficult for a network attack that requires position information on the network of the communication partner to increase security. Is possible.

  In the present invention, a person who provides a service using the present invention enhances security by specifying a person who intends to execute communication every time communication is performed, and for example, it is used for communication for emergency calls. It is possible to give priority to the communication, or the communication partner can resume the communication after the communication is completed.

  In the present invention, at the time of communication, a fee for executing communication can be calculated according to the content of the communication. Therefore, it becomes easy to charge the user for the cost necessary for realizing highly reliable communication according to the usage situation.

BEST MODE FOR CARRYING OUT THE INVENTION

  A communication method according to the first embodiment of the present invention will be described below. First, the outline of the communication system used here will be described based on the example of FIG. This system includes a path switch (A, B, C) and a controller, and there are communication devices (C1, C2) that perform communication using this system.

  Each path switch is connected to a network, and is an apparatus comprising a computer having a function of converting a transmission source and a destination of a packet received from a communication apparatus or another path switch and transmitting it to the communication apparatus or another path switch. It is. The source and destination of the packet are not limited to the network address. For example, when using UDP (User Datagram Protocol), the UDP port number is also included. In other words, each route switch is a device having a function known as NAT (Network Address Translator) or NAPT (Network Address and Port Translator) that can convert both the source and the destination. Moreover, you may have the function to change the value of TTL (Time To Live) contained in a packet in the case of conversion. Each route switch may have connection points or network addresses with a plurality of networks, and the converted packet may be transmitted using the network that received it, or other networks may be used. May be transmitted.

  In the example of FIG. 1, the route switch A and the route switch B, the route switch B and the route switch C, and the route switch C and the route switch A can communicate with each other. Each route switch holds information (for example, information including a network address) of communicable route switches (hereinafter referred to as adjacent route switches). Further, an identifier (hereinafter referred to as “adjacent path switch ID”), such as a numerical value or a character string, may be uniquely held for each adjacent path switch. Of course, four or more route exchanges may exist. Each route switch need not be able to communicate directly with all other route switches, and there may be a set of route switches that cannot communicate directly with each other. The adjacent route switch can be added and changed, and the controller may hold information related to the adjacent route switch through communication between the route switch and the controller.

  An IP network can be used for communication between route exchanges, but another network may be used for a part thereof. For example, for the communication between the route exchange A and the route exchange B and between the route exchange B and the route exchange C, an IP network composed of devices such as a router and a switch is used. The communication may use a network of a protocol other than IP.

  The controller is a device having a function of controlling the path switch. The controller and each path switch can communicate directly or indirectly. For communication, a network different from the network connecting the path switches or between the path switch and the communication device may be used, and it is desirable to use a dedicated communication path for communication with each path switch. There is no restriction on the communication method, and for example, IP or other protocols may be used. Further, there may be a case where communication is relayed by another device (for example, another route switch) on the way. There may be a plurality of controllers. For example, there may be two controllers having equivalent functions and the processing may be distributed. Alternatively, one controller may control some route exchanges, and the other route exchanges may perform functions by communicating with other controllers.

  One controller or one route switch may be composed of one computer or a plurality of computers. Moreover, the computer which comprises it may exist in the place distant geographically.

  A communication device is a device having a function of using a network. For example, a computer that executes Windows or UNIX, or a telephone-only machine. It may be a router or a device having a multicast function. Each communication device only needs to be able to communicate with at least one of the path switches. In the example of FIG. 1, the communication device C1 can communicate with the route switch B, and the communication device C2 can communicate with the route switch C. For example, UDP or TCP (Transmission Control Protocol) can be used for communication between a communication device, a route switch, and communication devices via the route switch. You may have the function to adjust the size of the packet sent to a route switch based on the state of a network.

  There is no restriction on the configuration of the physical layer for communication between computers used in the present invention.

  FIG. 2 is a simplified flowchart showing a procedure for starting communication. Here, the communication destination is another communication device that is a communication partner of the communication device.

  In the example of FIG. 1, the communication device C1 transmits a communication start request to the route switch B. The request may be transmitted in a plurality of packets. The request includes a resource (for example, a UDP port number) to be allocated to the communication device C1, and an identifier (C2 here) of the communication partner. The request may include other information, for example, information on a band to be used and communication quality. The route exchange B forwards this request to the controller, and the controller searches for the location (for example, IP address) of the communication partner. However, the communication device C1 may directly send a request to the controller. For the search, for example, a database in which the correspondence between the identifier and the position on the network is recorded can be used. There are no restrictions on the number of databases and the data structure used at that time, and the search may be executed only by the controller, or may be executed by communicating with one or more route switches. Further, the position on the network may be used as an identifier as it is.

  When a communication partner (here, the communication device C2) exists and permits the start of communication, the controller determines a communication path for the communication. The communication path can be determined based on, for example, a rule that minimizes the number of route exchanges that pass through. Others, for example, the type and priority of communication to be performed, the bandwidth available between the route exchanges that are routed, the reliability of communication between the route switches that are routed, and the use of communication channels for other communications that are simultaneously performed The determination may be made in consideration of the situation and the time required to transfer information between the communication device and the communication destination via the communication path. The type and priority of communication to be executed may include, for example, information on the type and priority in the request for starting communication, or may be specified by the network address of each communication device. Further, it may be determined according to the band to be used. The time required to transfer the information can be obtained, for example, by summing up RTT (Round-Trip Time) between route exchanges serving as communication routes. For this purpose, the route switch or the controller may have a function of monitoring and holding the RTT between adjacent route switches. Information for determining a communication path may be collected each time communication is started, or may be created in advance and held as a database.

  When the communication path is determined, the controller controls the path switch C, and the path switch C requests the communication device C2 whether to accept the communication and the resource to be allocated to the communication device C2 when the communication is received. Send. Specifically, for example, an IP packet including the identifier of the communication device (here, C1) that requested the start of the communication is transmitted. The request may include other information, for example, information on a band to be used and communication quality. When the communication device C2 accepts the communication requested by the communication device C1, it transmits a response including resources to be assigned to the path switch C. Specifically, for example, an IP packet including the UDP port number to be allocated is transmitted. The response may include other information, for example, information on the bandwidth to be used and communication quality. The route exchange C transfers the response received from the communication device C2 to the controller. However, the controller may directly execute the inquiry to the communication device C2. The inquiry may not be made to the communication device C2, and in this case, the destination of the packet transmitted from the communication device C1 after the start of communication, which is a resource allocated to the communication device C2, is determined as the communication device C1. Any one of the controller and the path switch may be determined.

  Note that the resources allocated to each communication device can be used regardless of the communication instead of specifying each communication device for each communication in order to limit the functions of the communication device or reduce the amount of information required to start communication. It may be fixed or determined by a controller or a route switch. In that case, the request from the communication device C1 and the response from the communication device C2 do not have to include information on the resource to be allocated.

  When starting the requested communication after the procedure, the controller creates a communication path for the communication. In the example of FIG. 1, in order to create a packet conversion rule for communication of these communication devices in the path switch B and the path switch C, communication is performed with each path switch. At that time, if necessary (for example, when a communication to be newly started is prioritized), the communication path of another communication being executed may be changed or stopped.

  The controller transmits (1) the resource C1a to the resource Bb of the communication device C1 to the route switch B by transmitting the position of the adjacent route switch or the communication device, the resource allocated to each, and the resource allocated to the route switch. For the packet received in the above, the source is the resource Bc, the destination is the resource Cd of the path switch C, and (2) the packet received from the resource Cd of the path switch C to the resource Bc is the source of the resource Bb and the destination is the communication device C1. A conversion rule for transmission as a resource C1a of the communication device C1 is created. For the packet received from the resource C2f from the resource C2f of the communication device C2 to the resource Ce, the transmission source is the resource Cd and the destination is the route switch B. (2) For a packet received from the resource Bc of the path switch B to the resource Cd, the source is the resource Ce and the destination Resources C2f communication device C2, creates a transformation rule to send as. However, the resources Bb and Bc and the resources Cd and Ce may be the same. Different communication paths or resources may be used in both directions of communication. Furthermore, when the controller transmits information for route creation to each route switch, information other than the above may be included, for example, information regarding the allocated bandwidth and communication quality. You may use the adjacent path switch ID currently hold | maintained in the switch.

  Thereafter, the information transmitted from the resource C1a of the communication device C1 to the resource Bb of the route switch B reaches the resource C2f of the communication device C2 from the resource Ce of the route switch C via the route switches B and C. The information transmitted from the resource C2f of the C2 to the resource Ce of the route exchange C passes through the route exchanges C and B, and reaches the resource C1a of the communication device C1 from the resource Bb of the route exchange B. Communication of the communication device C2 becomes possible.

  In communication according to the present invention, a controller, a path switch, or other computer capable of communicating with either or both of them, for example, in order to charge a person using the communication according to the present invention Usage charges can be calculated based on type, content, communication partner, assigned communication quality, and communication time.

  A communication method according to the second embodiment of the present invention will be described below. First, the outline of the communication system used here will be described based on the example of FIG. This system includes route exchanges (A, B, C, D), and there are communication devices (C1, C2) that execute communication using this system.

  The difference from the first embodiment is that no controller is provided outside. The functions of the controller, such as searching for communication partners of communication devices, determining communication paths, and determining packet conversion rules, are provided inside one or more path switches. In order to create a communication route, the route exchanges communicate with each other and exchange information for realizing the above functions. For example, a controller provided in one of the route switches may control the packet conversion rules of all the route switches, or may share the route switches controlled by the controllers of a plurality of route switches. Of course, an external controller may be used to control some route switches. It is desirable to reserve a band or to use a dedicated communication path for communication for control that occurs between path switches having a controller function and between other path switches. Other features are the same as those in the first embodiment.

  The present invention does not require control of a communication device using the communication method according to the present invention when a failure such as link disconnection or a decrease in communication quality occurs in a part of a communication path or a route switch, and the communication device Has a function of changing the communication path used by the communication being executed and preventing the influence on the communication. A method used for realizing this function will be described based on the example of FIG. FIG. 4 shows a part of a communication path in communication executed in any of the above embodiments, for example, and includes path exchanges (A, B1, B2, C, D). For the sake of simplicity, other path switches, communication devices, and controllers are not drawn.

  FIG. 4 shows an example in which a certain communication is executed via the route exchange A, the route exchange C, and the route exchange D, and a failure occurs in the network between the route exchange A and the route exchange C that are communication routes. It is. There are no restrictions on how to detect faults. For example, when a packet is transmitted to an adjacent route switch at regular intervals and does not reach a certain level, it may be regarded as a failure. Alternatively, the RTT up to the adjacent route switch may be measured at regular intervals, and a decrease in communication quality may be detected from the change. The communication is changed so that the route switch A, the route switch B1, the route switch B2, and the route switch D are used as communication paths. The change is realized by the communication between the controller and the route switch and by changing, adding, or deleting the packet conversion rule of each related route switch. The same applies when a failure occurs in the path switch (here, path switch C).

  The present invention does not require control of a communication device using the communication method according to the present invention, and further, does not impair information exchanged in communication performed by the communication device, and does not impair the communication path used by the communication. It has a function to change. A method used for realizing this function will be described based on the example of FIG. FIG. 5 shows a part of a communication path in communication executed in any of the above embodiments, for example, and includes path exchanges (A, B1, B2, C, D). For the sake of simplicity, other path switches, communication devices, and controllers are not drawn.

  FIG. 5 shows an example in which a certain communication is executed via the route exchange A, the route exchange C, and the route exchange D, and the route exchange C existing on the communication route is disconnected from the network. The communication is changed so that the route switch A, the route switch B1, the route switch B2, and the route switch D are used as communication paths.

The change is realized by the controller and the route switch performing communication and changing, adding, or deleting the packet conversion rule of each related route switch. In that case, for example, the communication path is changed by the following procedure:
(1) Create a packet conversion rule for the route switch B1 and the route switch B2. ;
(2) The route switch A receives from the route switch B1 so that the destination of the packet received from the route switch B2 is converted to the same destination as the converted destination of the packet received from the route switch C. The conversion rule is changed so that the destination of the packet is converted to the same destination as the converted destination of the packet received from the route switch C. ;
(3) The conversion rule is changed from the route switch C to the route switch B1 as the destination of the packet transmitted by the route switch A, and from the route switch C to the route switch B2 as the destination of the packet transmitted from the route switch D. ;
(4) Disconnect the path switch C from the network. ;
For simplification, only one direction of communication is shown in the figure.
The same applies to the case where only a part of the connection between the route exchanges is disconnected or only the change of the communication route is executed. In this case, the procedure (4) is different or omitted.

  The present invention can also be used through networks of different types and versions. In the example of FIG. 6, the route switch is connected to IP networks having different versions or address spaces. In the embodiment shown in this example, communication between the communication device C1 and the communication device C2 is possible as in the other embodiments.

  In the present invention, one or more path switches and controllers may have a function of controlling communication conditions of communication executed using the present invention. For example, the maximum bandwidth that a certain communication can use may be limited. Since the bandwidth limiting method is well known, it will be omitted. Furthermore, communication quality may be controlled between the path switch and the communication device by using, for example, RSVP. In addition, as shown in the example of FIG. 7, using a technique for guaranteeing or improving communication quality when a packet transmitted by a route switch is transferred to an adjacent route switch in part or all of a network between route switches. Also good. It may have a function of reserving a band for use in communication according to the present invention between a path switch and an adjacent path switch for a part or all of the network between the path switches. There are no restrictions on the technology for reserving bandwidth and guaranteeing or enhancing communication quality. For example, MPLS or RSVP may be used. The path switch or the controller may have a function of controlling the setting of these technologies such as a reserved bandwidth, or requesting control from another device or network, depending on the use state of communication. The path switch and the controller may have the function of holding information about the bandwidth available for the present invention between the path switches.

  In the present invention, general NAT or NAPT may exist in part or all of communication paths between path switches using the IP network or between the path switch and the communication device. It is only necessary that packets can be transmitted and received in the same manner as in the communication method when a general NAT or NAPT exists in a general IP network. Since the communication method in that case is well known, it is omitted. However, when the destination necessary for transmitting the packet to the communication partner is unknown at the time of creating the communication path, one or more packets are transmitted from the communication partner, and the destination is determined after receiving the packet.

  A path switch or a communication device may transmit or receive a packet for avoiding communication disconnection due to the NAT or NAPT session timeout (hereinafter referred to as keep-alive packet). The received keep-alive packet does not have to be transferred to another route switch or communication device. In order to distinguish between communication packets and keep-alive packets between communication devices having the same contents as the keep-alive packet, for example, the route switch may change some or all of the packets. In addition, a session may be used to transmit or receive a packet for distinguishing and communicating with the packet.

  It is a schematic block diagram of the system used for the communication method concerning 1st Embodiment of this invention.   It is a flowchart which shows the procedure at the time of starting communication in the system used for the communication method concerning 1st Embodiment of this invention.   It is a schematic block diagram of the system used for the communication method concerning 2nd Embodiment of this invention.   In this invention, it is a figure for demonstrating the method of changing a communication path | route, without requiring the stop of the communication currently performed.   In this invention, it is a figure for demonstrating the method to change a communication path, without losing the information of the communication currently performed.   It is a figure for demonstrating the example in case many types of networks are used in this invention.   It is a figure for demonstrating the example in case this invention is used with the technique for improving communication quality.

Explanation of symbols

C1 communication equipment C1
C2 communication equipment C2
A Route switch A
B Route switch B
C Route switch C
D Route switch D
B1 Route switch B1
B2 Route switch B2

Claims (17)

  In an IP network, a path switch composed of a computer having a network address conversion function, and a controller that exists inside or outside the path switch and can communicate using the same or different communication path as the path switch and the IP network And holding information on the set of route exchanges that can communicate with each other, determining a communication destination for the communication device based on a request of the communication device and the information, and from the communication device, the same as the communication device or A packet conversion rule of one or a plurality of the route exchanges to the communication destination that exists in a different network and can or cannot communicate with the communication device without requiring conversion of a packet source or destination. The packets transmitted to each of these route switches are In the exchange, control is performed so that the route exchange is used as a transmission source and the next route exchange, the communication device, or the communication destination is used as a destination, and communication is sequentially performed via the controlled route exchange. A communication method comprising a function of creating a route and realizing communication using the route. The communication method according to claim 1, comprising the following steps when the communication device starts communication:
(1) The communication device transmits a communication start request to the route switch or the controller;
(2) a step in which one or both of the controller and the path switch searches for a position in the network of the communication destination;
(3) a step in which the route switch or the controller inquires of the communication destination whether the communication request can be accepted and a resource to be allocated to the communication destination for the communication;
(4) Either one or both of the controller and the path switch determines a communication path to be created through the path switch from the communication device to the communication destination, and a network address is assigned to each path switch existing in the path. Creating a transformation rule;
(5) a step in which the route switch or the controller notifies the communication device and the communication destination of resource information created in the route switch for the purpose of communication with the communication destination;   3. Either or both of the resources allocated to the communication device and the communication destination are fixed, or a part or all of the communication device, the communication destination, the path switch, and the controller are determined. Communication method.   When creating the communication route, information on the number of the route exchanges through which the communication route passes, information on the type of communication to be executed, information on the priority of communication to be executed, and available between the route exchanges through Bandwidth information, information on the reliability of communication between the route exchanges that pass through, information on the status of other communications that are executed simultaneously, information between the communication device and the communication destination via the communication route 4. The communication method according to claim 1, wherein the communication path is determined based on a part or all of the information of the time required to transfer the information.   5. The communication method according to claim 1, wherein a failure or a deterioration in communication quality is detected in the path switch or a network between the path switches.   The communication path is changed without necessitating the stop of the communication by changing a packet conversion rule of the path switch for the communication executed using the created communication path. Item 5. The communication method according to items 1-4.   For communication executed using the created communication path, the communication information is not lost by changing the packet conversion rule of the path switch existing in the communication path after creating an alternative path. The communication method according to any one of claims 1 to 4, wherein the communication path is changed.   7. The route switch holds an independent identifier corresponding to another route switch that can communicate with each other, and uses the identifier when creating and changing a communication route. 8. The communication method according to 7.   The communication method according to claim 1, wherein the path switch and the controller control a bandwidth that can be used for each communication via the path switch and a quality of each communication.   The communication quality when a packet transmitted by a certain route switch is transferred to another route switch in a part or all of a network interposed between the route switches is guaranteed or controlled. The communication method according to 1-4.   Reserving a band to be used for communication according to the present invention between the path switch and another path switch for a part or all of the network interposed between the path switches, and the reserved band The communication method according to claim 1, wherein the path switch and the controller change according to the communication status.   When there is a general device having a network address translation function between two route exchanges, by transmitting and receiving packets between the route exchanges, without requiring control by the communication device and the communication destination, The communication method according to claim 1, wherein communication is maintained in a possible state.   The communication device and the communication destination, when performing communication, the controller, the path switch, or another computer calculates a fee for executing the communication. The communication method described.   The communication method according to claim 1, wherein a packet is transferred to a part of a communication path between the communication device and the communication destination using a network having a protocol different from IP.   An apparatus comprising: a function of holding information on a set of network addresses capable of transmitting packets to each other, and searching for a route from a network address to another network address based on the information.   An apparatus comprising a function of determining packet conversion rules of a plurality of path switches composed of computers having a network address conversion function based on a request from a communication device.   A network address conversion function; a function of holding information of a device having another network address conversion function capable of communicating with each other; and a function of changing a network address conversion rule based on control of an external controller. Equipment.

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