JP2023130884A - Transfer device and program - Google Patents

Abstract

To enable continued service provision even when a wireless device moves to an area associated with a different MEC (Multi-Access Edge Computing) site.SOLUTION: A transfer device is used in a network where a first packet, which is sent by a wireless device depending on the position of the wireless device and destined for a common address, is transferred to one transfer device of a plurality of transfer devices. The transfer device includes: means for holding a first identifier; and means which, when the first packet is received, determines whether or not a second identifier included in the first packet matches the first identifier, and if the second identifier matches the first identifier, transfers the first packet to one server device of one or more server devices associated with the transfer device, while if the second identifier does not match the first identifier, transfers a first capsulated packet storing the first packet in a pay load to another transfer device to which the second identifier is assigned.SELECTED DRAWING: Figure 6

Description

The present disclosure relates to techniques for continuing communications in an edge computing environment.

In the current cloud computing environment using large, centralized data centers, it is difficult to provide low-latency services. For this reason, Non-Patent Document 1 discloses MEC (Multi-Access Edge Computing) in which many small-scale data centers are geographically distributed to provide services. In the following, the MEC data center will be referred to as the MEC site. Each MEC site is associated with a geographic area. For example, an area associated with one MEC site may be an area served by one or more base stations. A wireless device (WD) of a mobile communication network is served by equipment at a MEC site associated with the area in which the WD is currently located.

In networks using current IP protocols, a communication device obtains the IP address of a communication partner from DNS when starting communication. Therefore, when a WD connects to a MEC site, the DNS must inform the WD of the IP address of the device in the MEC site that is associated with the area in which the WD is currently located. To achieve this, the IP address acquisition process must be changed so that the WD notifies the DNS of location information indicating its location, and the DNS determines the IP address to be notified to the WD based on the location information. .

Non-Patent Document 2 discloses a technology called IP Anycast (hereinafter referred to as Anycast method) as a method that does not require changes in IP address acquisition processing. In the Anycast method, the same IP address (hereinafter referred to as a common address) is assigned to devices at all MEC sites that provide the same service. Therefore, when receiving services provided by devices at the MEC site, the WD will obtain a common address from the DNS regardless of its location. When the WD obtains the common address from the DNS, it transmits an IP packet with the common address set as the destination address. When the mobile communication network receives an IP packet with the common address set as the destination address, it forwards the IP packet to the MEC site associated with the area where the WD is currently located. For example, if the MEC site is associated with one or more base stations, the mobile communication network forwards the IP packet to the MEC site associated with the base station to which the WD is currently connected. When a connection such as a TCP connection is established between the WD and a device within the MEC site, the WD and the device within the MEC site thereafter communicate using the established connection.

S. Kekki, et al. , "MEC in 5G networks", ETSI white paper, vol. 28, pp. 1-28, June 2018 M. Suzuki, et al. , "Enhanced DNS Support towards Distributed MEC Environment", ETSI White Paper No. 39, September 2020

For example, suppose that while a WD in a first area is receiving service from a device in a first MEC site, the WD moves to a second area associated with a second MEC site. In this case, the IP packet sent by the WD is sent to the device within the second MEC site. Since the device within the second MEC site does not have a connection with the WD, it discards the IP packet received from the WD. Therefore, service provision to the WD is stopped.

The present invention provides a technique that allows a wireless device to continue providing service even when it moves to an area associated with a different MEC site.

According to one aspect of the present invention, the method is used in a network that forwards a first packet destined for a common address transmitted by the wireless device to one of a plurality of forwarding devices according to the location of the wireless device. The transfer device includes a holding unit that holds a first identifier, and upon receiving the first packet from the network, determines whether a second identifier included in the first packet matches the first identifier, and If the second identifier matches the first identifier, the first packet is transferred to one of the one or more server devices associated with the transfer device, and the second identifier is and a transfer means for transferring a first encapsulated packet in which the first packet is stored in a payload to another transfer device to which the second identifier is assigned, if the first identifier does not match the first identifier. .

According to the present invention, service provision can be continued even when a wireless device moves to an area associated with a different MEC site.

FIG. 1 is a system configuration diagram according to an embodiment. FIG. 2 is a sequence diagram according to one embodiment. FIG. 2 is a sequence diagram according to one embodiment. FIG. 3 is a diagram illustrating transfer information according to one embodiment. FIG. 1 is a configuration diagram of a transfer device according to an embodiment. FIG. 3 is a diagram showing determination information according to an embodiment. FIG. 2 is a sequence diagram according to one embodiment.

Hereinafter, embodiments will be described in detail with reference to the accompanying drawings. Note that the following embodiments do not limit the claimed invention, and not all combinations of features described in the embodiments are essential to the invention. Two or more features among the plurality of features described in the embodiments may be arbitrarily combined. In addition, the same or similar configurations are given the same reference numerals, and duplicate explanations will be omitted.

<First embodiment>
FIG. 1 shows the system configuration according to this embodiment. The MEC site 1 includes a transfer device 2 and a plurality of server devices 3. Although two MEC sites 1 are shown in FIG. 1, the number of MEC sites 1 is any number greater than or equal to 2, and they are located at various geographical locations. In the following description, when two MEC sites 1 are to be distinguished, they will be referred to as MEC site #1 and MEC site #2. Further, in FIG. 1, the number of server devices 3 located at each MEC site 1 is two, but the number of server devices 3 located at each MEC site 1 may be any number greater than or equal to one. Furthermore, it is not necessary to make the number of server devices 3 arranged at each MEC site 1 the same. In the following description, when distinguishing between the server devices 3, they are expressed as server devices #1-1, #1-2, #2-1, and #2-2, as shown in FIG. Similarly, when distinguishing two transfer devices 2, they are expressed as transfer devices #1 and #2, as shown in FIG.

In this embodiment, a site identifier is assigned to each MEC site 1. According to FIG. 1, the site identifier of MEC site #1 is ID#1, and the site identifier of MEC site #2 is ID#2. Note that the site identifier is also the device identifier of the transfer device 2 at the same MEC site. The site identifier is set for all devices (transfer device 2 and server device 3) in the same MEC site 1. The server device 3 to which the same site identifier as the site identifier set to the transfer device 2 is set is the server device 3 associated with the transfer device 2.

Further, a server identifier is assigned to each server device 3. According to FIG. 1, the server identifiers of server devices #1-1, #1-2, #2-1 and #2-2 are SID #1-1, #1-2, #2-1 and #2, respectively. It is 2-2. Note that the server identifier of the associated server device 3 is set in the transfer device 2. Furthermore, similarly to the Anycast method, in this embodiment, a common address AD#C is assigned to the transfer device 2 of each MEC site 1.

Further, each transfer device 2 is assigned a unique address, which is a unique address. According to FIG. 1, the unique address of transfer device #1 is AD#1, and the unique address of transfer device #2 is AD#2. Transfer device 2 is connected to network 4 . Further, the transfer device 2 is connected to the server device 3 within the same MEC site 1. Note that each server device 3 is also assigned a unique address. The unique address assigned to each server device 3 may be a private address.

The WD 5 accesses the MEC site 1 via a base station (not shown) of the mobile communication network and the network 4, and receives service from the server device 3 within the MEC site 1. Note that, similarly to the Anycast method, when the WD 5 accesses the MEC site 1, the DNS (not shown) is configured to notify the common address AD#C to the WD 5 regardless of the location of the WD 5. In the following description, a packet transmitted by the WD 5 toward the MEC site 1, that is, a packet in which the common address AD#C is set as the destination address, will be referred to as an "MEC packet." The network 4 changes the destination of the MEC packet depending on the location of the WD 5. In this embodiment, if WD5 is in area #1, the MEC packet is transferred to MEC site #1, and if WD5 is in area #2, the MEC packet is transferred to MEC site #2. .

FIG. 2 is a sequence diagram when the WD 5 starts accessing the MEC site 1. Note that it is assumed that WD5 is in area #1. Upon acquiring the common address AD#C from the DNS, the WD 5 transmits an MEC packet (request MEC packet) for requesting a connection in S10. The request MEC packet is transferred to transfer device #1 of MEC site #1. Upon receiving the request MEC packet, transfer device #1 selects one of server devices #1-1 and #1-2 and transfers the request MEC packet to the selected server device 3. Note that the transfer device 2 has a normal NAT function, and converts the common address AD#C set as the destination address of the request MEC packet to the unique address of the selected server device 3. Note that in the following description, an MEC packet whose destination address has been changed by the transfer device 2 will also be referred to as an MEC packet. According to FIG. 2, transfer device #1 has selected server device #1-1. Therefore, transfer device #1 transmits a request MEC packet to server device #1-1 in S11.

Upon receiving the request MEC packet, server device #1-1 sets a connection identifier for a connection to be established. In this embodiment, the connection identifier is the site identifier ID#1 of the MEC site #1 where the server device #1-1 to set up the connection is installed, and the server identifier SID #1-1 of the server device #1-1. Contains the concatenated value. For example, the connection identifier can be a value obtained by concatenating the site identifier ID#1 of the MEC site #1, the server identifier SID#1-1 of the server device #1-1, and a random number in a predetermined order. As a response to the request MEC packet, server device #1-1 transmits a response packet, which includes a connection identifier and is a packet indicating a response to the request MEC packet, to transfer device #1 in S12. The address of the WD5, which is the source address of the request MEC packet, is set as the destination address of the response packet.

When the transfer device #1 receives the response packet from the server device #1-1, the transfer device #1 transmits the received response packet to the WD 5 via the network 4 in S13. After the connection between the WD 5 and the server device #1-1 is established, a connection identifier is set in all packets sent and received between the WD 5 and the server device #1-1. The WD 5 transmits an MEC packet including data (data MEC packet) in S14. Transfer device #1, which has received the data MEC packet, determines that the transfer destination server device 3 is server device #1-1 based on the connection identifier (including the server identifier) included in the data MEC packet. Therefore, transfer device #1 transmits the data MEC packet to server device #1-1 in S15. In S16, server device #1-1 transmits a data packet, which is a packet containing data, to WD5. When the transfer device #1 receives the data packet from the server device #1-1, it transfers it to the WD 5 (S17).

Thereafter, as long as the WD 5 is within the area #1, communication is performed between the WD 5 and the server device #1-1 as shown in S14 to S17 in FIG.

FIG. 3 is a sequence diagram when the WD 5 moves to area #2 while continuing communication with server device #1-1. Since WD5 has entered area #2, the data MEC packet transmitted in S20 is transferred to transfer device #2 of MEC site #2. Based on the connection identifier included in the received data MEC packet, the transfer device #2 determines in S21 whether the data MEC packet is destined for its own site. In this example, the site identifier included in the connection identifier is ID#1, which does not match the site identifier ID#2 of MEC site #2 where transfer device #2 is installed, so transfer device #2 receives the It is determined that the data MEC packet is not destined for the own site.

In this case, transfer device #2 transfers the received data MEC packet to transfer device 2 (transfer device #1 in this example) of MEC site 1 (in this example, MEC site #1) which is the original destination. . Note that encapsulation is used for transfer. That is, transfer device #2 generates a new packet, stores the received data MEC packet in the payload of the generated packet, and transmits it to transfer destination transfer device 2 in S22. Hereinafter, a packet that encapsulates another packet will be referred to as an encapsulated packet. In order to determine the value to be set as the destination address of the encapsulated packet, each transfer device 2 uses the site identifier of the other MEC site 1 and the transfer device 2 installed at the MEC site 1 to which the site identifier is assigned. It holds forwarding information indicating the relationship with the unique address. FIG. 4 shows an example of transfer information held by transfer device #2. Based on the transfer information and the site identifier ID#1 included in the received data MEC packet, the transfer device #2 sets the unique address AD#1 of the transfer device #1 as the destination address of the encapsulated packet and transfers it to the network. Send to 4.

Upon receiving the encapsulated packet containing the data MEC packet in the payload, the transfer device #1 extracts the data MEC packet stored in the payload. Then, in S23, transfer device #1 converts the source address of the data MEC packet, that is, the address of WD5, to the source address of the encapsulated packet, that is, the unique address of transfer device #2 in this example. Register it in the return information in association with #2. Furthermore, based on the server identifier SID#1-1 included in the retrieved data MEC packet, the transfer device #1 transmits the data MEC packet to the server device #1-1 in S24.

In S25, server device #1-1 transmits a data packet destined for WD5 to transfer device #1. Upon receiving the data packet, transfer device #1 determines in S26 whether the destination address of the data packet is registered in the return information. If not registered, transfer device #1 transmits the received data packet to network 4. On the other hand, if registered, the transfer device #1 encapsulates the received data packet and transmits it to the transfer device 2 associated with the destination address of the data packet in the return information. In this example, since the IP address of the WD5 is registered in the return information and associated with the unique address AD#2 of the transfer device #2, the transfer device #1 encapsulates the data packet in S27 and transfers the data packet to the transfer device #2. Send to 2. Upon receiving the encapsulated packet containing the data packet, the transfer device #2 extracts the data packet and transmits the data packet to the WD 5 in S28 based on the destination address of the data packet.

With the above configuration, when the WD 5 moves, communication can be continued even if the MEC packet is transferred to a different MEC site 1 from before. Although some parts are omitted in FIGS. 2 and 3 to simplify the explanation, each time the transfer device 2 receives a packet, it determines how to transfer the packet. This determination method will be described later.

FIG. 5 is a configuration diagram of the transfer device 2. As shown in FIG. Communication interface 20 is connected to network 4 . The connection interface 21 is connected to the server device 3. When the communication interface 20 and the connection interface 21 receive a packet, they output the received packet to the transfer unit 22 . The transfer unit 22 has determination information and determines processing for the received packet based on the determination information. FIG. 6 shows determination information held by transfer device #k installed at MEC site #k. Note that the site identifier of MEC site #k is ID#k, and the unique address of transfer device #k is AD#k. Note that, as described above, the site identifier ID#k can also be regarded as the device identifier of the transfer device #k.

First, when the transfer unit 22 receives a packet whose destination address is the common address AD#C and has no connection identifier (no site identifier), it determines to transmit the packet to the server device 3 in the MEC site #k. do. Note that when a plurality of server devices 3 are installed at the MEC site #k, the transfer device #k selects which server device 3 to send to by an arbitrary method. In this case, the transfer unit 22 outputs the packet to the connection interface 21 together with information indicating the destination server device 3 . Note that this process corresponds to S10 and S11 in FIG.

When the transfer unit 22 receives a packet in which the destination address is the common address AD#C and the site identifier in the connection identifier is ID#k, the transfer unit 22 transfers the packet to the MEC site #k indicated by the server identifier in the connection identifier. It is determined that the data is to be transmitted to the server device 3 of. In this case, the transfer unit 22 outputs the packet to the connection interface 21 along with information indicating the destination server device 3 . Note that this process corresponds to S14 and S15 in FIG.

When the transfer unit 22 receives a packet in which the destination address is the common address AD#C and the site identifier in the connection identifier is different from ID#k, the transfer unit 22 determines to encapsulate the packet and transmit it to the network 4. In this case, the transfer unit 22 causes the encapsulation processing unit 23 to encapsulate the received packet. That is, the encapsulation processing unit 23 is caused to generate an encapsulated packet. In the following description, a packet stored in the payload of an encapsulated packet will be referred to as an encapsulated packet. The transfer unit 22 determines the value to be set as the destination address of the encapsulated packet by referring to the transfer information using the site identifier. The transfer unit 22 transmits the encapsulated packet to the communication interface 20. Note that this process corresponds to S20 to S22 in FIG.

When the transfer unit 22 receives an encapsulated packet whose destination address is the unique address AD#k, the transfer unit 22 determines to decapsulate the encapsulated packet. In this case, the transfer unit 22 causes the encapsulation processing unit 23 to decapsulate the received encapsulated packet. That is, the encapsulation processing unit 23 is caused to take out the encapsulated packet stored in the payload of the encapsulated packet. Subsequently, processing for the encapsulated packet is determined again based on the determination information. This process corresponds to the processes of S22 to S24 and S27 and S28 in FIG. Note that, as shown in S23 in FIG. 3, when transmitting the encapsulated packet to the server device 3, the transfer unit 22 determines the correspondence between the source address of the encapsulated packet and the source address of the encapsulated packet. to be registered in the return information. Note that when receiving a packet whose destination address is the unique address AD#k but which is not an encapsulated packet, the transfer unit 22 performs normal packet processing.

When the transfer unit 22 receives a packet whose destination address is different from the common address AD#C and the unique address AD#k and which is not registered in the return information, the transfer unit 22 transmits the destination address of the packet to the packet. Perform normal transfer processing according to . In this case, the transfer unit 22 transmits the received packet to the interface corresponding to the destination address. Note that this process corresponds to S16 and S17 in FIG.

When the transfer unit 22 receives a packet whose destination address is different from the common address AD#C and the unique address AD#k and whose destination address is registered in the return information from the server device 3 of the MEC site #k, , it is determined that the packet is to be encapsulated and transmitted to the network 4. In this case, the transfer unit 22 causes the encapsulation processing unit 23 to encapsulate the received packet. The transfer unit 22 determines the value to be set as the destination address of the encapsulated packet by referring to the return information using the destination address of the encapsulated packet. The transfer unit 22 transmits the encapsulated packet to the communication interface 20. Note that this process corresponds to S25 to S27 in FIG.

In the embodiment described above, the common address AD#C and the unique address are assigned to the transfer device 2, and only the unique address is assigned to each server device 3. However, it is also possible to have a configuration in which the common address AD#C and a unique address are assigned to each server device 3, and only the unique address is assigned to each transfer device 2. Even in this case, each MEC site 1 is configured so that packets are transmitted and received between the network 4 and each server device 3 via the transfer device 2 of the same MEC site 1. Note that in this case, the transfer device 2 does not perform NAT. By doing so, communication can be performed as explained in FIGS. 1 to 6.

<Second embodiment>
Next, the second embodiment will be described focusing on the differences from the first embodiment. In the sequence of FIG. 3, unless the WD 5 returns to area #1, communication between the WD 5 and the server device #1-1 will go through another MEC site 1, resulting in increased delay. Therefore, in this embodiment, when transfer device #1 receives the encapsulated data MEC packet from MEC site #2 in S22, communication is performed via transfer device #2 of MEC site #2. This is notified to server device #1-1. This notification includes, for example, the unique address of transfer device #2. For example, the transfer device #1 can make the notification using the header area of the data MEC packet in S24. Further, transfer device #1 can individually notify server device #1-1 that communication with WD5 is being performed via transfer device #2 of MEC site #2.

In response to the notification, server device #1-1 can transmit a request to shift the service provision to WD5 to MEC site #2. FIG. 7 is a sequence diagram of a process in which server device #1-1 transfers service provision to WD5 to MEC site #2. In addition, in FIG. 7, the dotted line arrow indicates the process by which server device #1-1 takes over the role of providing services to MEC site #2, and the solid line arrow indicates the process by which server device #1-1 transfers the connection identifier to WD5. This shows the process for notifying changes.

In S30, server device #1-1 transmits a takeover request packet, which is a packet requesting takeover to MEC site #2. The destination of the takeover request packet is, for example, the unique address of the transfer device #2 notified from the transfer device #1 in the notification. Note that the takeover request packet includes the unique address of server device #1-1. Transfer device #1 transfers a takeover request packet to transfer device #2 in S31. Upon receiving the takeover request packet, transfer device #2 selects server device 3 from server devices #2-1 and #2-2 to take over service provision. In FIG. 7, transfer device #2 selects server device #2-2. Therefore, transfer device #2 transmits a newly generated takeover request packet to server device #2-2 in S32. This newly generated takeover request packet includes the unique address of server device #1-1. Server device #2-2 sends a response packet to server device #1-1 based on the unique address of server device #1-1 included in the takeover request packet, and sends a response packet to server device #1-1 that is necessary for providing the service. Obtain relevant information. For example, when the WD 5 receives distribution of video data, it acquires information for identifying undelivered data. Additionally, the server device #2-2 generates a connection identifier, that is, a value that combines the site identifier ID #2 of the MEC site #2, the server identifier #2-2 of the server device #2-2, and a random number. Then, the server device #1-1 is notified in the process of S33.

When the handover is completed, server device #1-1 generates an identifier switching notification packet that notifies that the connection identifier will be changed. The identifier switching notification packet contains, in addition to the previous connection identifier, the connection identifier to be used in future communication with WD5, that is, the connection generated by server device #2-2 and notified to server device #1-1. Contains an identifier. In S34, server device #1-1 transmits an identifier switching notification packet with the destination set to WD5 to transfer device #1. Transfer device #1 encapsulates the identifier switching notification packet and sends it to transfer device #2 (S35), and transfer device #2 sends the identifier switching notification packet included in the encapsulated packet to WD 5 (S36). As a result, the WD 5 includes a connection identifier including the site identifier ID#2 of the MEC site #2 and the server identifier SID#2-2 of the server device #2-2 in subsequent MEC packets. As a result, the MEC packet is transmitted from transfer device #2 to server device #2-2. Furthermore, upon transmitting the identifier switching notification packet to the WD5, the transfer device #1 deletes the entry of return information regarding the WD5.

With the above configuration, by moving the WD 5, communication can be continued even if the MEC packet is transferred to a different MEC site 1 from before, and an increase in communication delay can be suppressed.

In each of the embodiments described above, it is assumed that the transfer device 2 is connected to one or more associated server devices 3. However, it is only necessary that packets can be sent and received between the transfer device 2 and the associated one or more server devices 3, and the transfer device 2 can directly communicate with the associated one or more server devices 3. does not need to be connected to.

Note that the transfer device 2 according to the present disclosure can be realized by a program that causes a computer to operate as the transfer device 2. The program is configured to cause the device to function as the transfer device 2 when executed on one or more processors of a device having one or more processors. The program can be stored on a computer readable storage medium or distributed via a network.

The invention is not limited to the above-described embodiments, and various modifications and changes can be made within the scope of the invention.

With the above configuration, service provision can be continued even if the wireless device moves to an area associated with a different MEC site. Therefore, it will be possible to contribute to Goal 9 of the Sustainable Development Goals (SDGs) led by the United Nations: ``Build resilient infrastructure, promote sustainable industrialization, and expand innovation.''

22: Transfer section

Claims (11)

A transfer device used in a network that transfers a first packet destined for a common address transmitted by the wireless device to one transfer device among a plurality of transfer devices according to the location of the wireless device,
holding means for holding the first identifier;
Upon receiving the first packet from the network, it is determined whether a second identifier included in the first packet matches the first identifier, and if the second identifier matches the first identifier, , forwards the first packet to one of the one or more server devices associated with the transfer device, and if the second identifier does not match the first identifier, the first Transfer means for transferring a first encapsulated packet containing the packet in a payload to another transfer device to which the second identifier is assigned;
A transfer device equipped with If the second identifier matches the first identifier, the transfer means transfers the server device to which the server identifier included in the first packet is assigned, among the one or more server devices. The transfer device according to claim 1, which transfers the first packet. According to claim 1 or 2, when the first packet does not include the second identifier, the transfer means transfers the first packet to one server device selected from the one or more server devices. Transfer device as described. The transfer means holds transfer information indicating a correspondence relationship between a unique address assigned to each of the plurality of transfer devices and the second identifier,
If the second identifier does not match the first identifier, the transfer means sets a unique address corresponding to the second identifier as a destination address of the first encapsulated packet and transmits it to the network. The transfer device according to any one of claims 1 to 3, wherein the first encapsulated packet is transferred to the another transfer device. When receiving a second encapsulated packet in which a unique address assigned to the transfer device is set as the destination from the network and a second packet is stored in the payload, the transfer means sends a message to the destination of the second packet. If the common address is set and the second identifier included in the second packet matches the first identifier, the second packet is sent to one of the one or more server devices. The transfer device according to claim 4, wherein the transfer device transfers the second packet to a server device to which the server identifier included in the second packet is assigned. 6. The transfer device according to claim 5, wherein the transfer means notifies a server device to which a server identifier included in the second packet is assigned that the second packet has been received from another transfer device. 2. The transfer means, when the common address is not set as the destination of the second packet, transfers the second packet to a device to which the address set as the destination of the second packet is assigned. 6. The transfer device according to 5 or 6. When the transfer means transfers the second packet to a server device to which a server identifier included in the second packet is assigned, the transfer means includes a first source address of the second encapsulated packet and a first source address of the second packet. The transfer device according to any one of claims 5 to 7, wherein the transfer device retains a correspondence relationship between the second source address and the second source address as return information. Upon receiving the third packet from one of the one or more server devices, the transfer means transfers the address set as the destination of the third packet to the second source address of the return information. It is determined whether or not they match, and if the address set as the destination of the third packet does not match the second source address of the return information, the third packet is set as the destination of the third packet. 9. The transfer device according to claim 8, wherein the transfer device transfers the transferred address to the device to which the address is assigned. If the address set as the destination of the third packet matches the second source address of the return information, the transfer means stores the third packet in a payload and includes the third packet in the return information. 10. The transfer device according to claim 9, wherein the third encapsulated packet having the first source address indicated as corresponding to the second source address as the destination is transmitted to the network. A program characterized in that when executed by the one or more processors of a device having one or more processors, the program causes the device to function as the transfer device according to any one of claims 1 to 10.

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