WO2022180665A1 - Communications system, communications method, connection destination management server, and program - Google Patents

Abstract

The present invention aims to achieve seamless connection destination switching between different types of networks, select a switching method that matches the desired quality, and reduce relay server and network loads.　A communications system pertaining to the present invention comprises: a switching quality estimation server that estimates the communications quality required when switching a user terminal connection; and a connection destination management server that is connected to a plurality of relay servers and the switching quality estimation server and manages a relay server that connects the user terminal to a service server. The connection destination management server is connected to the user terminal and the service server and, if the relay server that has established a main path needs to be switched, selects the method for switching to the destination relay server, on the basis of the estimation results, and notifies about the destination relay server and the switching method to the switching source relay server that established the main path.

Description

Communication system, communication method, connection destination management server and program

The present disclosure relates to a communication system, communication method, connection destination management server, and program for establishing multipaths.

When the user terminal continues the service across multiple networks (NW), Mobile IPv6 (Non-Patent Document 1), MPTCP (MultiPath Transmission Control Protocol) (Non-Patent Document 2), etc. are used between the service server and the terminal. With this technology, multiple paths are constructed with multiple interfaces (IF), and between NWs with different address types (heterogeneous NWs), terminals connected across the NWs appear to have the same IP address, so that between different types of NWs A method of continuing the same session and continuing the service is adopted.

Taking MPTCP as an example of conventional multipath establishment technology, after establishing a TCP (Transmission Control Protocol) connection, the transmitting side stores a sequence number in the TCP option area, separates, and transmits. The receiving side reads the sequence numbers and rearranges them to match the data.

However, when using the TCP option area to establish a connection and send and receive data, there is a problem with versatility because the service used is limited to the TCP protocol. Therefore, it is conceivable to eliminate protocol dependency by performing multipath establishment and sequence number arrangement/matching processing in Layer 3 such as the IP header instead of Layer 4 such as in the TCP protocol.

In addition, the conventional MPTCP is a technique that accompanies session establishment by TCP's 3-way handshake, so in order to use it, the service server must also support MPTCP. Therefore, a method is conceivable in which the relay server monitors packets between the user terminal and the service server, and terminates the multipath to the terminal instead of the service server.

MPTCP has a problem that as the number of user terminals to be switched increases and the number of path establishment destinations increases, the load on the relay server that terminates them increases.
In addition, if multipath communication is always performed at the time of switching, there is a problem that depending on the load state of the relay server and the packet communication method, the service may be greatly affected, such as an increase in processing delay.

JP 2005-328427 (Patent 4401864)

In order to solve the above problems, the present disclosure is capable of constructing a multipath environment even when there is no reachability from a network to a service server after connection destination switching, and seamless connection between heterogeneous networks. It is an object of the present invention to achieve early switching, select a switching method that matches the required quality, and reduce the load on a relay server and network.

This disclosure installs a connection destination management server that collects connection destination network information and connection destination switching instruction information declared by user terminals in networks that have reachability in all networks that user terminals can use. Then, the relay servers installed in each network that the user terminal can use secure mutual reachability via the connection destination management server based on the instruction from the connection destination management server. At this time, the connection destination management server reflects the requested quality at the time of switching estimated from the application information acquired from each user terminal in the switching instruction.

Specifically, the communication system according to the present disclosure includes:
A communication system comprising: a plurality of relay servers connectable to a user terminal; and a service server connected to the user terminal via the relay server and providing a service to the user terminal,
a switching quality estimation server for estimating a communication quality required at the time of connection switching of said user terminal; and a relay server connected to said plurality of relay servers and said switching quality estimation server and for connecting said user terminal to said service server. and a connection destination management server that manages
The connection destination management server is connected to the user terminal and the service server, and when switching of a relay server establishing a main path is necessary, a method of switching to a relay server of a switching destination based on an estimation result. and select
Notifying the switching destination relay server and the switching method to the switching source relay server that has established the main path,
Upon receipt of the notification, the switching source relay server transmits a path establishment request to the switching destination relay server with respect to its own device, and
if the switching method is multipath switching, causing the user terminal to transmit a subpath connection request to the switching destination relay server;
if the switching method is single path switching, causing the user terminal to transmit a main path connection request to the switching destination relay server, and disconnecting the main path between the device and the user terminal;
The switching destination relay server establishes a subpath or a main path with the relay server that has transmitted the path establishment request and with the user terminal that has transmitted the main path connection request or the subpath connection request, respectively.

Specifically, the connection destination management server according to the present disclosure
A connection destination management server that is connected to a plurality of relay servers connectable to a user terminal and manages the relay servers that connect the user terminal to a service server,
aggregating connection-related information including application information executed on each user terminal from the plurality of relay servers;
Acquiring the communication quality required at the time of connection switching of the user terminal estimated based on the aggregated connection-related information,
selecting a method of switching to a switching destination relay server based on the obtained communication quality when switching of a relay server that is connected to the user terminal and the service server and has established a main path is required;
The switching destination relay server and the switching method are notified to the switching source relay server that has established the main path.

Specifically, the communication method according to the present disclosure includes:
A communication method executed by a communication system comprising a plurality of relay servers connectable to a user terminal, and a service server connected to the user terminal via the relay server and providing a service to the user terminal There is
The communication system is connected to a switching quality estimation server for estimating communication quality required at the time of connection switching of the user terminal, the plurality of relay servers, and the switching quality estimation server, and connects the user terminal to the service server. a connection destination management server that manages the relay server connected to the
The connection destination management server is connected to the user terminal and the service server, and when switching of a relay server establishing a main path is necessary, a method of switching to a relay server of a switching destination based on an estimation result. and select
Notifying the switching destination relay server and the switching method to the switching source relay server that has established the main path,
Upon receipt of the notification, the switching source relay server transmits a path establishment request to the switching destination relay server with respect to its own device, and
if the switching method is multipath switching, causing the user terminal to transmit a subpath connection request to the switching destination relay server;
if the switching method is single path switching, causing the user terminal to transmit a main path connection request to the switching destination relay server, and disconnecting the main path between the device and the user terminal;
The switching destination relay server establishes a subpath or a main path with the relay server that has transmitted the path establishment request and with the user terminal that has transmitted the main path connection request or the subpath connection request, respectively.

A program according to the present disclosure implements a computer as each functional unit provided in the connection destination management server.

According to the present disclosure, even if there is no reachability from the network after connection destination switching to the service server, a multipath environment can be constructed, and seamless connection destination switching between heterogeneous networks can be realized. , the switching method can be selected according to the required quality, and the load on the relay server and network can be reduced.

4 illustrates an example use of the system of the present disclosure; 1 shows an example of a system configuration of the present disclosure; An example of the configuration of each element of the communication system of the present disclosure is shown. 3 shows an example of a flowchart showing the flow of connection destination switching determination. 4 shows an example of a flowchart showing the flow of multipath establishment. 4 shows an example of a flowchart showing the flow of packet transmission/reception. An example of a sequence for establishing a multipath via a relay server different from the main path is shown. An example of a sequence when no multipath is established is shown. An example of connection related information is shown. 4 shows an example of scheduler operation. 1 shows an example of an option field in an IP packet; An example of an IPv6 option storage area is shown. An example of an IPv4 option storage area is shown. An example of switching quality is shown. An example of a packet transmission method is shown.

Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings. Note that the present disclosure is not limited to the embodiments shown below. These implementation examples are merely illustrative, and the present disclosure can be implemented in various modified and improved forms based on the knowledge of those skilled in the art. In addition, in this specification and the drawings, constituent elements having the same reference numerals are the same as each other.

(Points of this disclosure)
FIG. 1 shows an example of the system configuration of the present disclosure. In the communication system of the present disclosure, network A (NW-A86) and network N (NW-N86n) to network M (NW-N86m) are connected to each other, and network A and network N to network M are all It is connected to network C. Networks A and N to M are networks provided by MNOs (Mobile Network Operators), for example. Network C is a network provided by (Virtual Mobile Network Operator). User terminals 93 (user terminal x 93x . . . user terminal y 93y) are connected to each network (from network A and network N to network M) via a relay server on each network. For example, the user terminal 93 is connected to network A using relay server A20, and connected to network M using relay server m20m. The present disclosure includes a connection destination management server 40 connected to all of the relay server A20 and the relay server n20n to the relay server m20m, and the switching quality estimation server 50 connected to the connection destination management server 40 is used by each user. It determines whether or not it is necessary to establish a multipath between the terminal and the relay server. Then, based on this determination result, the connection destination management server 40 and each relay server work together to establish a connection between the user terminal 93 and any relay server among the relay servers A20 and n20n to m20m. to establish a single path or multiple paths. Hereinafter, switching quality refers to communication quality required at the time of switching.

User terminal 93 (user terminal x93x ... user A connection destination management server 40 is installed to collect/manage connection destination NW information and connection destination switching instruction information reported by the terminal y93y) as connection related information, and indicate a relay server of a connection destination with the user terminal 93. Understand connection destination switching information in advance.
Based on the instruction from the connection destination management server 40, the relay server A20 installed in each NW (NW-A86, NW-N86n to NW-M86m) and the relay server n20n to relay server m20m confirm each other's address. Reachability between heterogeneous NWs is ensured.
To ensure reachability, based on the multipath option information written in the multipath option, each relay server rewrites the destination/source information and transfers it, and the user terminal 93 and the service edge server 85 are transferred via the connection switching destination NW. By enabling communication between them, a multipath environment is formed and seamless switching is possible.
At this time, the switching quality estimation server 50 estimates the quality necessary for switching from the terminal information (application information) from each user terminal 93 collected by the connection destination management server 40 . The connection destination management server 40 determines whether or not seamless switching is necessary based on the estimation result, and reflects it in the switching instruction.
Also, the connection destination management server 40 determines whether or not seamless switching is necessary based on the estimation result, and reflects it in the switching instruction.

(Effects of this disclosure)
In the switching instruction to the user terminal 93, the quality level required for switching is estimated from the application and service used for each user terminal 93, and the switching method is selected according to the required quality. Unnecessary resource load on the server can be reduced, and the load on the NW side can also be reduced. Method selection points are whether or not the multipath switching method is necessary and the packet transmission method for multipath.

(embodiment)
FIG. 2 shows an example of the configuration of a communication system according to this embodiment. FIG. 3 shows an example of the configuration of each element of the communication system according to this embodiment. The communication network system according to the present embodiment includes NW-A 86, NW-B 87 and NW-C 88, which are heterogeneous NWs having different address bands, user terminal 93 connectable to each NW, NW-A 86 and NW -Relay server A20 and relay server B30 that relay packets on B87, service edge server 85 that provides service to user terminal 93, and service master that provides service-related information to service edge server 85 A server 84, a connection destination management server 40 that manages information on a NW to which a user terminal 93 can be connected as connection-related information, and a request for switching the user terminal 93 based on the information managed by the connection destination management server 40 and a switching quality estimation server 50 for estimating quality.

The service master server 84 is located on the Internet, communicates and connects with the service edge server 85 on the edge cloud, and provides service-available user information and service information.

The service edge server 85 is arranged on an edge cloud having reachability with the NW-A 86, communicates with the service master server 84 and the user terminal 93, receives service-related information on service provision from the service master server 84, A service is provided in response to a request from the user terminal 93 .

NW-A86 has edge cloud and reachability with NW-C88.
NW-B87 has reachability with NW-C88.
NW-C88 has reachability with NW-A86 and NW-B87.
The switching quality estimation server 50 is located on the NW-C 88 and is connected to the connection destination management server 40 for communication.
The connection destination management server 40 is located on NW-C88, which has reachability with NW-A86 and NW-B87, and is connected for communication with relay servers (A, B) of each NW (NW-A86, NW-B87). .
The relay server A20 is arranged on the NW-A86, the user terminal 93, and
It is connected for communication with the connection destination management server 40 and the service edge server 85 .
The relay server B30 is arranged on the NW-B87, the user terminal 93, and
It is connected for communication with the connection destination management server 40 .
The user terminal 93 is communicatively connected to the relay server of each NW (NW-A86, NW-B87).
It should be noted that all communication connections may be through either wired or wireless media.
Also, the user terminal 93 may be connected to the service master server 84 instead of the service edge server 85 .

A case of switching the connection of the user terminal 93 connected to the relay server A20 to the relay server B30 will be described below, but the present invention is not limited to this. A plurality of user terminals 93 may be provided.

The user terminal 93 includes a control communication interface (hereinafter "interface" is abbreviated as "IF") section 11-1, a control communication IF section 11-2, an IP communication IF section 12-1, an IP communication IF A connection information management unit 13, a switching control unit 14, an IP header area setting unit 15, a scheduler unit 16, a virtual IF unit 17, and an application control unit 18 are provided. The user terminal 93 can also be realized by a computer and a program, and the program can be recorded on a recording medium or provided through a network.

The relay server A20 includes a control communication IF unit 21-1, a control communication IF unit 21-2, an IP communication IF unit 22-1, an IP communication IF unit 22-2, an IP communication IF unit 22-3, A connection information management unit 23 , a switching control unit 24 , an IP header area setting unit 25 and a scheduler unit 26 are provided. The relay server A20 can also be realized by a computer and a program, and the program can be recorded on a recording medium or provided through a network.

Relay server B30 includes control communication IF section 31-1, control communication IF section 31-2, IP communication IF section 32-1, IP communication IF section 32-2, connection information management section 33, switching control A transfer processing unit 35 is provided. The relay server B30 can also be realized by a computer and a program, and the program can be recorded on a recording medium or provided through a network.

The connection destination management server 40 includes a control communication IF unit 41 , a connection information management unit 43 and a connection destination control unit 45 . The control communication IF section 41, the connection information management section 43, and the connection destination control section 45 are connected to each other. The connection destination management server 40 can also be realized by a computer and a program, and the program can be recorded on a recording medium or provided through a network.
Another relay server connected to both the relay server A20 and the relay server B30 may also serve as the connection destination management server 40 .

The switching quality estimation server 50 includes a control communication IF section 51 and a switching quality estimation section 52, which are connected to each other. The switching quality estimation server 50 can also be implemented by a computer and a program, and the program can be recorded on a recording medium or provided through a network.

The relay servers A20 and B30 collect/manage connection-related information from connected user terminals and notify the connection destination management server 40 of the information.
The connection destination management server 40 aggregates/manages the connection-related information of the user terminal group connected to each NW via the relay servers A20 and B30.

IP communication IF units 12-1, 12-2, 22-1, 22-2, 22-3, 32-1 and 32-2 are IP communication IF units. IP communication IF units 12-1 and 22-1, 12-2 and 32-1, and 22-2 and 32-2 are connected, respectively, and IP communication IF unit 22-3 is a service edge. It is connected to server 85 .

The control communication IF units 11-1, 11-2, 21-1, 21-2, 31-1, 31-2, 41 and 51 are control communication IF units and may be common to the IP communication IF units. The control communication IF units 11-1 and 21-1 are connected to 11-2 and 31-1, respectively, and the control communication IF units 21-2 and 31-2 are connected to the control communication IF unit 41. is doing. Further, the control communication IF section 51 is connected to the control communication IF section 47 .

The connection information management units 13, 23, 33, and 43 notify/manage connection-related information between each device through the control communication IF unit. For example, the connection information management unit 13 of the user terminal 93 manages connection-related information such as connectable NW information and communication quality information for each IF in addition to the MAC address and IP address of each communication IF. Notify the destination relay server. Also, the connection information management unit 23 of the relay server A 20 and the connection information management unit 33 of the relay server B 30 hold and manage all or part of the connection related information related to the user terminals accommodated in their own devices. The relay server A20 and the relay server B30 utilize the connection-related information managed by the connection information management section of their own devices for their operations.

The connection destination control unit 45 determines the connection destination of each user terminal according to the quality policy of the NW based on the connection related information of the user terminal group, and the switching control unit of each relay server performs switching for each user terminal. Notify the destination NW. Connection destination determination such as connection destination optimization based on the quality policy may be performed by another server (external server).

The switching quality estimating unit 52 estimates the switching quality required by each terminal from various information of each user terminal 93 collected by the connection destination management server 40 and notifies the connection destination management server 40 of it.

The switching control units 14, 24 and 34 manage the main path and sub-paths and perform switching control. Each of the switching control units 14, 24, and 34 establishes a subpath/main path based on control information such as a "switching destination instruction" and a "switching completion notification" received by the control communication IF unit or IP communication IF unit connected to itself. Controls such as path disconnection. An ON/OFF instruction may be given to the IP communication IF unit.
The forwarding processing unit 35 creates a forwarding table and forwards the packet based on the instruction from the switching control unit 34 .

The scheduler units 16 and 26 separate and reintegrate data.
On the transmission side, the schedulers 16 and 26 determine the priority of each IP communication IF and the transmission IF of each packet. In accordance with this, the sequence number of the packet is determined and instructed to the IP header area setting unit. It should be noted that the transmission packet may be copied and transmitted to a plurality of IP communication interfaces. On the receiving side, the scheduler units 16 and 26 reintegrate based on the sequence number read by the IP header area setting unit. If duplicate packets are received, they may be discarded here.

On the transmitting side, the IP header area setting units 15 and 25 store each piece of information in the IP header based on instructions from the scheduler unit and switching control unit. The IP header area setting units 15 and 25 on the receiving side read the path information from the IP header, and if there is multipath option information, notify the switching control unit connected thereto. Along with this, the IP header area setting unit 25 rewrites the source of the IP header to the virtual IF unit, rewrites the destination of the IP header to the service edge server, and transfers it to the scheduler unit connected to itself. Also, the IP header area setting unit 15 rewrites the source of the IP header to the service edge server, rewrites the destination of the IP header to the virtual IF unit, and transfers it to the scheduler unit connected to itself. Those without multipath option information are transferred to the scheduler as they are. Here, the multipath option information is information written in the multipath option, and includes information described in the IP header for matching multipath packets, such as the sequence number of the packet and the transmission/reception destination IF.

The virtual IF unit 17 is a virtual IP communication IF for showing the same terminal across different NWs. For example, the virtual IF unit 17 may have a common IP address common to the main path and subpath.
The application control unit 18 controls applications that operate on the user terminal 93 , including applications that receive service from the service edge server 85 .

FIG. 4 shows how connection-related information is transmitted and received between the user terminal and the connection destination management server 40, determination of whether or not connection destination switching is necessary for each user terminal, and notification of the result to the relevant relay server. It is an example of a flowchart showing the flow of.

The user terminal 93 operates as follows.
The connection information management unit 13 collects and manages its own connection-related information, and notifies the relay server 20A of the latest connection-related information at regular intervals (or requests from the relay server) (S101, S102). The connection-related information includes connectable NW information (wired, Wi-Fi, mobile, etc.), detailed information of each NW (service ID, SSID, SIM information, etc.), IF information (MAC address, IP addresses, radio wave intensity, etc.) and user terminal information (applications in use, resources, etc.). In addition, information such as that shown in FIG. 9, which will be described later, is included.

The relay servers A20 and B30 operate as follows.
The connection-related information from each user terminal is collected, managed, and notified to the connection destination management server 40 (S103 to S105). The notification trigger may be a spontaneous trigger (fixed period, operator's operation, etc.) or an external trigger (request from the connection destination management server 40, request from the NW, when a user terminal is newly connected, etc.). Note that information from sources other than the user terminal (for example, within the NW where the relay server is installed) may also be aggregated and notified.

The connection destination management server 40 operates as follows.
Collect and manage connection-related information from each relay server (S107), determine whether or not to switch the connection destination of each user terminal (S108, S109), and based on the estimation result of the switching quality estimation server, the corresponding relay server is notified of connection destination switching information (switching destination NW, switching method) for each user terminal (S172, S111, S112). The decision trigger may be a spontaneous trigger (fixed period, operation by an operator, etc.) or an external trigger (instruction from another server, request from each NW, information update from a relay server, etc.). Here, the connection destination switching information includes the identification information of the user terminal to be switched, the identification information of the switching source relay server connected to the user terminal, and the relay destination to be connected to the user terminal from now on. Contains server identification information. Also, the connection destination switching information may include arbitrary information used for connecting the switching destination relay server to the switching user terminal.

The switching quality estimating server 50 estimates the communication quality required at the time of switching (session disconnection possibility, allowable delay, etc.) based on the connection-related information for each user terminal 93 received from the connection destination management server 40 (S170). ), and notifies the connection destination management server 40 (S171). If the switching destination determination time is shorter than the estimated time, the switching quality of the target terminal may be estimated after specifying the switching target terminal. If the estimation of switching quality and the determination of the switching destination are processed independently, and the relationship between the estimation of the switching quality and the processing time of the switching destination determination is such that the estimation of the switching quality < the determination of the switching destination, waiting for the result of the switching destination determination. , the overall processing will be slow, and the switching quality estimation can be processed in a sufficiently short time. be done. However, if the processing time relationship is switching quality estimation>switching destination determination, the overall processing time can be shortened by limiting the processing target of switching quality estimation based on the result of switching destination determination.
With this, the processing of the flowchart shown in the drawing ends.

Each step of the flowchart shown in FIG. 4 will be described below.
The connection information management section 13 of the user terminal 93 transmits its own connection-related information to the control communication IF section 11-1 (S101).
The control communication IF unit 11-1 of the user terminal 93 transmits the connection-related information to the control communication IF unit 21-1 of the relay server A20 (S102).

The control communication IF section 21-1 of the relay server A20 receives connection-related information from the user terminal 93 (S103).
The connection information management unit 23 of the relay server A20 collects and updates the connection related information from each user terminal 93 connected to the relay server A20, and transmits it to the control communication IF unit 21-2 (S104).
The control communication IF section 21-2 of the relay server A20 transmits the collected connection-related information to the control communication IF section 41 of the connection destination management server 40 (S105).

The control communication IF section 41 of the connection destination management server 40 receives the connection-related information and transmits it to the connection information management section 43 (S106).
The connection information management unit 43 of the connection destination management server 40 aggregates and updates the connection related information from the relay server A20, and notifies the connection related information of each user terminal 93 to the connection destination control unit 45 (S107).
The connection destination control unit 45 of the connection destination management server 40 determines whether switching of the connection destination of the user terminal 93 is necessary based on the aggregated connection related information, periodically or by some trigger (S108).
When the connection destination control unit 45 of the connection destination management server 40 determines that the connection destination switching of the user terminal 93 is unnecessary, S108 is performed again (S109).
The connection destination control unit 45 of the connection destination management server 40 notifies the switching quality estimation server 50 of the received connection related information such as the application information of each user terminal 93, and requests the estimation of required quality at the time of switching (S170). ).
The switching quality estimating unit 52 of the switching quality estimating server 50 estimates the required quality at the time of switching based on the received terminal information such as the application information of each user terminal 93, and replies to the connection destination management server 40 (S171 ).
The connection destination control unit 45 of the connection destination management server 40 notifies the connection destination switching destination/switching method to the connection information management unit 43 based on the connection destination switching information of each user terminal 93 and the switching quality estimation result ( S172).
The connection information management unit 43 of the connection destination management server 40 transmits the connection destination switching information of the user terminal 93 accommodated in each relay server to the control communication IF unit 41 (S111).
The control communication IF section 41 of the connection destination management server 40 transmits the connection destination switching information of the user terminal accommodated in each relay server to the control communication IF sections 21-2 and 31-2 (S112).
The connection destination management server notifies the relay server A20 and the relay server B30 from the viewpoint of security, and spoofing can be prevented by knowing in advance that the path request will come from another relay server. This is because

The control communication IF section 21-2 of the relay server A20 acquires the connection destination switching information of the user terminal 93 accommodated from the connection destination management server 40, and transfers it to the connection information management section 23 (S113).
The connection information management unit 23 of the relay server A 20 identifies the target user terminal 93 from the connection destination switching information of the user terminal 93 stored therein, and confirms the latest connection status (S114). If the target user terminal 93 is still not connected (S115), the connection information management unit 23 of the relay server A20 updates the connection related information of the target user terminal 93 (S116).

FIG. 5 is an example of a flow chart showing the flow of exchange of control communication between the relay server A 20 and the user terminal 93 and between the relay servers after the determination of connection destination switching and establishment of multipaths.

The relay server A20 operates as follows as a multipath establishment instruction.
The connection information management unit 23 confirms the content of the connection destination switching information for each user terminal 93 received from the connection destination management server 40, and connects the relevant user terminal 93 and another relay server (relay server B30). path establishment is determined (S121).
If it is necessary to establish a path with another relay server (relay server B30) (S122), it notifies the relay server B30 of a path establishment request (S123, S124) and establishes the path. After that, connection destination switching information (connection destination NW, necessity of multipath) is transmitted to the corresponding user terminal 93 (S128, S129). In establishing a path with another relay server, if packet transfer alone cannot pass FW or the like, reachability may be ensured by linking with VPN construction or a filter function. When a subpath establishment request comes from the user terminal (S133, S134), the subpath setting is reflected in the IP header area setting section, and a subpath establishment notification is transmitted to the user terminal (S135 to S137).
When the multipath setting completion notification is received from the user terminal 93, multipath communication is started (S145).

The relay server B30 performs subpath transfer as follows.
When a path establishment request notification is received from relay server A20 (S125), a transfer table is created in transfer processing unit 35 (S126), and a path establishment completion notification is transmitted to relay server A20 (S127).
When a subpath connection request is received from the user terminal 93 (S138, S139), the subpath setting is reflected in the transfer processing unit 35, and a subpath establishment completion notice is transmitted to the user terminal (S140 to S142). If relay server A20 and relay server B30 do not have direct reachability, another relay server may be placed in NW-C88 to establish reachability.

The user terminal 93 operates as a multipath termination as follows.
When the connection destination switching information is received from the relay server A20 (S130), the switching control unit 14 confirms the switching destination NW, relay server information, and switching method (S131).
If multipath establishment is required (S173), a subpath connection request is transmitted to relay server A20 or relay server B30 (S133, S134, S138, S139).
When a subpath establishment completion notification is received from relay server A20 or B30, the multipath setting is reflected in the IP header area setting section, and multipath setting completion is notified to relay server A20 (S143, S144).
After that, multipath communication is started.
If multipath establishment is unnecessary (S173), a main path connection request is transmitted to relay server A20 or relay server B30 (S174).
With this, the processing of the flowchart shown in the drawing ends.

Each step of the flowchart shown in FIG. 5 will be described below.
If the target user terminal 93 is still connected (S115), the connection information management unit 23 of the relay server A 20 performs connection switching information for each user terminal 93 from the connection destination management server 40. Then, the corresponding user terminal 93 and the presence or absence of a relay server requiring path establishment are confirmed, and the result is notified to the switching control unit 24 (S121).
When it is necessary to establish a path between relay servers (S122), the switching control unit 24 performs S128 after performing the following S123 to S127. On the other hand, if the path establishment between relay servers is unnecessary (S122), the switching control unit 24 directly performs S128.

The switching control unit 24 of the relay server A20 transmits a path establishment request to the relay server B30 to the IP communication IF unit 22-2 (S123).
IP communication IF section 22-2 of relay server A20 transmits a path establishment request to relay server B30 (S124).
The IP communication IF section 32-2 of the relay server B30 receives the path establishment request from the relay server A20 and transmits it to the switching control section 34 (S125).
The switching control unit 34 of the relay server B30 responds to the request from the relay server A20,
While creating a transfer table in the transfer processing unit 35,
A path establishment completion notification to the relay server A20 is sent to the IP communication IF section 32-2 (S126).
IP communication IF section 32-2 of relay server B30 transmits a path establishment completion notification to relay server A20 (S127).

The switching control unit 24 of the relay server A20 transmits the connection destination switching information for the user terminal 93 to be switched to the connection destination to the IP communication IF unit 22-1 (S128).
The IP communication IF unit 22-1 of the relay server A20 transmits connection destination switching information to each user terminal 93 (S129).

The IP communication IF unit 12-1 of the user terminal 93 receives the connection destination switching information from the relay server A20 and notifies the switching control unit 14 (S130).
The switching control unit 14 of the user terminal 93 confirms the content of the connection destination switching information from the relay server A20 (S131), and confirms whether multipath establishment is required (S173).
If multipath establishment is required and subpath establishment with a relay server different from the main path is not performed, S133 to S137 are performed. When establishing a subpath with another relay server, S138 to S142 are performed (S132). If multipath establishment is unnecessary, a main path connection request is transmitted to relay server A20 or relay server B30 as described above (S174).

First, a case (S133 to S137) will be described where multipath establishment is necessary and subpath establishment with a relay server other than the main path is not performed.
The switching control unit 14 notifies the IP communication IF unit 12-1 of the subpath connection request for the relay server A20 (S133).
The IP communication IF section 12-1 of the user terminal 93 transmits a subpath connection request to the relay server A20 (S134).
The IP communication IF section 22-1 of the relay server A20 receives the subpath connection request from the user terminal 93 and notifies the switching connection section 24 of it. (S135)
The switching connection unit 24 of the relay server A20 receives the subpath connection request from the user terminal 93, reflects the subpath setting to the IP header area setting unit, and transmits the subpath to the user terminal 93 to the IP communication IF unit 22-1. Send an establishment complete notification. (S136)
The IP communication IF section 22-1 of the relay server A20 transmits a subpath establishment completion notification to the user terminal 93. FIG. (S137)

Next, a case where multipath establishment is required and a subpath is established with a relay server different from the main path (S138 to S142) will be described.
The switching control unit 14 of the user terminal 93 notifies the IP communication IF unit 12-2 of the subpath connection request to the relay server B30. (S138).
The IP communication IF unit 12-2 of the user terminal 93 transmits a subpath connection request to the relay server B30 (S139).
The IP communication IF section 32-1 of the relay server B30 receives the subpath connection request from the user terminal 93 and notifies the switching control section 34 of it. (S140)
The switching control unit 34 of the relay server B30 receives the sub-path connection request from the user terminal 93, reflects the sub-path setting and the transfer setting to the transfer processing unit 35, and sends the IP communication IF unit 32-1 to the user terminal 93. send a subpath establishment completion notification for (S141)
The IP communication IF section 32-1 of the relay server B30 transmits a subpath establishment completion notification to the user terminal 93. FIG. (S142)

The IP communication IF unit 12-1 or 12-2 of the user terminal 93 transmits the subpath establishment completion notification received from the relay server A20 or the relay server B30 to the switching control unit 14 (S143).
The switching control unit 14 of the user terminal 93 receives the subpath establishment completion notification from the relay server A20 or the relay server B30, reflects the multipath setting to the IP header area setting unit 15, and notifies the relay server A20 of the multipath setting completion. Notice. After that, multipath communication is started (S144).
The switching control unit 24 of the relay server A20 receives the multipath setting completion notification from the user terminal 93 and starts multipath communication. (S145)
In this embodiment, the control communication IF unit and the connection information management unit are connected, and the IF for transmitting/receiving signals handled by the connection information management unit, such as connection-related information and connection destination switching information, between devices is used for control communication. The IF section connects the IP communication IF section and the switching connection section, and transmits signals handled by the switching connection section such as path establishment request, path establishment completion notification, connection destination switching information, sub-path connection request and sub-path establishment completion notification between devices. Although the IF for transmission and reception is the IP communication IF, it is not limited to this. For example, the switching connection unit and the control communication IF unit may be connected, and the control communication IF unit may be used as an IF for transmitting and receiving signals handled by the switching connection unit between devices.

FIG. 6 shows the flow of data transmission/reception between the user terminal 93 and the relay server A20, between the user terminal 93 and the relay server B30, and between the relay server A20 and the relay server B30, until the data is transmitted to the service edge server 85. It is an example of a flow chart.

The user terminal 93 operates as a sender as follows.
When the virtual IF unit 17 acquires transmission data information from the application control unit 18 (S151) and detects use of multiple IFs, multipath transfer is started. For a multipath transfer packet, the scheduler unit 16 determines the priority of the destination IP communication interface, divides the packet according to this priority, and determines to which IP communication interface each packet is to be sent. (S154). At this time, instead of dividing the packet, it may be decided to copy the same packet and transmit it to the multiple IP communication IF units. Also, the switching control unit 14 determines multipath option information to be stored in the IP header.
Upon receiving instructions from the scheduler 16 and switching control unit 14, the IP header area setting unit 15 stores the schedule number and multipath option information in the IP header (S155).
Thereafter, each IP communication IF unit transmits the packet to the destination relay server (S156, S162).

The relay server B30 operates as a forwarder as follows.
After the IP communication IF section 32-1 receives the packet (S163), it transfers the packet to the transfer processing section 35 and reads the IP header (S164).
After confirming that the multipath option information can be read and that the packet is the target of multipath and that the packet is to be relayed to another relay server, the options described in the multipath option information are notified to the switching control unit. (S165, S166).
After that, the transfer processing unit 35 rewrites the IP header of the packet based on the transfer table, creates a packet to be transmitted to the relay server A20, and transfers it to the IP communication IF unit 32-2 (S167).
The IP communication IF section 32-2 transmits the received packet to the relay server A20 (S168).

The relay server A20 operates as a recipient as follows.
After each IP communication IF unit receives the packet, it transfers the packet to the IP header area setting unit and reads the IP header (S157, S158, S169).
The schedule number and multipath option information can be read, and when it is confirmed that the packet is a multipath target packet, the option contents are notified to the switching control unit 24 (S158, S159).
After that, the scheduler unit 26 reintegrates the divided packets based on the schedule number, and the IP header area setting unit 25 rewrites the IP header to the user terminal transmission packet based on the multipath option information. It is transferred to the section 22-3 (S160). At this time, copy packets may be detected and duplicate packets may be discarded. Further, the IP header area setting unit 25 may refer to the connection related information managed by the connection information management unit 23 when rewriting the IP header of the packet.
IP communication IF section 22 - 3 transmits the received packet to service edge server 85 .
With this, the processing of the flowchart shown in the drawing ends.

Each step of the flowchart shown in FIG. 6 will be described below.
The virtual IF unit 17 of the user terminal 93 acquires transmission data information from the application control unit 18 and transmits IP packets (S151).
The scheduler unit 16 of the user terminal 93 acquires IP packets from the virtual IF unit 17 (S152).
The scheduler unit 16 of the user terminal 93 confirms whether or not multiple interfaces are enabled (S153). If multiple interfaces are enabled, the scheduler unit 16 determines the IF priority and divides or copies the packet (S154).
The IP header area setting unit 15 of the user terminal 93 stores the schedule number and multipath option information in the IP header and transfers it to the IP communication IF units 12-1 and 12-2 (S155).
The IP communication IF section 12-1 of the user terminal 93 transmits the packet to the relay server A20 (S156).
The IP communication IF section 22-1 of the user terminal 93 receives the packet (S157).
The IP communication IF section 12-2 of the user terminal 93 transmits the packet to the relay server B30 (S162).

The IP communication IF section 32-1 of the relay server B30 receives the packet (S163).
The transfer processing unit 35 of the relay server B30 reads the schedule number and multipath option information,
It is checked whether the packet is subject to multipath and is subject to transfer to another relay server (S164).
If there is multipath option information described in the IP header (S165) and there is a relay packet to another relay server (S166), the transfer processing unit 35 of the relay server B30 refers to the transfer table and The destination of the header is rewritten to relay server A20, and transferred to IP communication IF section 32-2 of relay server B30 (S167).
IP communication IF section 32-2 of relay server B30 receives the packet and transfers it to relay server A20 (S168).

The relay server B30 may have another IP communication IF section 32-3 (not shown) and be connected to the service edge server via the IP communication IF section 32-3. In this case, when relay server B30 confirms that the IP header of the received packet does not include multipath option information (S165), relay server B30 sends the received packet to the service edge server connected to itself by the IP communication interface. It may be directly transmitted via the section 32-3 (S180).
Further, the relay server B30 may have an IP header area setting section (not shown) and a scheduler section (not shown). If the IP header contains multipath option information (S165) and the received packet is not a relay packet to another relay server (S166), the transfer processing unit 35 of the relay server B30 forwards the received packet to its own device. may be transferred to the IP header area setting unit (S181). After that, after performing S158 and S160 by the IP header area setting unit and the scheduler unit of the relay server B30, the relay server B30 transmits the packet to the service edge server connected to itself via the IP communication IF unit 32-3. may be sent.

IP communication IF unit 22-2 of relay server A20 receives the packet (S169).
The IP header area setting unit 25 of the relay server A20 reads the schedule number and multipath option information from the packet received by the IP communication IF unit 22-1 or IP communication IF unit 22-2, and confirms whether the packet is subject to multipath. (S158).
If multipath information is described in the IP header (S159), the scheduler unit 26 of the relay server A20 separates and integrates the data based on the multipath option information, rewrites the IP header, and rewrites the IP header. The packet is transferred to the IP communication IF unit 22-3, or the duplicate packet is discarded (S160).
The IP communication IF section 22-3 of the relay server A20 receives the packet and transfers it to the service edge server 85 (S161).

FIG. 7 shows an operation example of establishing a multipath via a relay server B30 different from the main path (between the user terminal 93 and the relay server A20).
The user terminal 93 uses the multipath option to transmit a connection request (information up to path connection) to the relay server A20 in order to establish a main path connection (S201) (S202).
The relay server A20 establishes a main path connection with the user terminal 93 (S203).
The user terminal 93 manages connection-related information such as connectable NW information and each IF information (MAC address, IP address, etc.) (S204), and notifies the connection-related information to the relay server A20 (S205).

The relay server A20 manages the connection-related information of the user terminals connected to the relay server A20 (S206), and notifies the connection-related information to the connection destination management server 40 (S207).
The relay server B30 manages the connection-related information of the user terminals connected to the relay server B30 (S208), and notifies the connection-related information to the connection destination management server 40 (S209).
The connection destination management server 40 manages connection-related information (S210).
The connection destination management server 40 makes an estimation request to the switching quality estimation server 50 (S250).
The switching quality estimation server 50 estimates the switching-time required quality of each user terminal 93 (S251), and notifies the connection destination management server 40 of the estimation result (S252).
The connection destination management server 40 determines the connection destination change (S211), and if the change is necessary, notifies the connection destination switching information (user terminal, relay server information) to the relay server A20 and the relay server B30 (S212). , S213).

The relay server A20 and the relay server B30 receive (start switching) the connection destination switching information (S214, S215), refer to the received connection destination switching information and the managed connection related information, and select the target user. Identify the terminal and check the latest connection status (S216, S217).
Relay server A20 establishes a path with relay server B30, which is the switching destination relay server (S218), and relay server B30 establishes a path with relay server A20, which is the switching source relay server (S219). A path is established between the relay server A20 and the relay server B30 (S220).
The relay server A20 and the relay server B30 notify the corresponding terminal group of the switching instruction (S221, S222). In this embodiment, the relay server A20 instructs the user terminal 93 to switch (S223).
The user terminal 93 receives the switching instruction (S224), and transmits a connection request to the relay server B30 (S226) in order to establish a subpath connection (S225).
The relay server B30 establishes a subpath connection with the user terminal 93 (S227).
Thus, relay server B30 completes relay path establishment (S228), and user terminal 93 and relay server A20 complete multipath establishment (S229, S230).

The user terminal 93 and the relay server A20 start multipath transfer (S231, S232), and perform main path transfer between the user terminal 93 and the relay server A20 (S233). The relay server B30 starts transfer relay (S234), and performs subpath transfer (S235, S236) with each of the user terminal 93 and the relay server A20.
When the reception IF switching is completed (S232, S233), the user terminal 93 and the relay server A20 notify each other of the switching completion (S234). The user terminal 93 and the relay server A20 disconnect the main path (S235, S236), and the switching is completed (S237, S238, S239).

Relay server A20 updates and manages the connection-related information (S240). The user terminal 93 manages connectable NW information and each IF information (MAC address, IP address, etc.) (S241), and notifies the relay server B30 of the connection-related information of its own device (S242).
The relay server B30 updates and manages the connection-related information (S243). The relay server B30 notifies the connection-related information to the connection destination management server 40 (S244).
The connection destination management server 40 updates and manages the connection-related information (S245).

FIG. 8 shows an operation example when the main path (between the user terminal 93 and the relay server A20) passes through a relay server B30 different from the relay server B30 and no multipath is established.
The user terminal 93 uses the multipath option to transmit a connection request (information up to path connection) to the relay server A20 in order to establish a main path connection (S301) (S302).
The relay server A20 establishes a main path connection with the user terminal 93 (S303).
The user terminal 93 manages connection-related information such as connectable NW information and each IF information (MAC address, IP address, etc.) (S304), and notifies the connection-related information to the relay server A20 (S305).

The relay server A20 manages the connection-related information of the user terminals connected to the relay server A20 (S306), and notifies the connection-related information to the connection destination management server 40 (S307).
The relay server B30 manages the connection-related information of the user terminals connected to the relay server B30 (S308), and notifies the connection-related information to the connection destination management server 40 (S309).
The connection destination management server 40 manages connection-related information (S310).
The connection destination management server 40 makes an estimation request to the switching quality estimation server 50 (S350).
The switching quality estimation server 50 estimates the switching-time required quality of each user terminal 93 (S351), and notifies the connection destination management server 40 of the estimation result (S352).
The connection destination management server 40 determines the connection destination change (S311), and if the change is necessary, notifies the connection destination switching information (user terminal, relay server information) to the relay server A20 and the relay server B30 (S312). , S313).

The relay server A20 and the relay server B30 receive (start switching) the connection destination switching information (S314, S315), inquire the received connection destination switching information and the managed connection related information, and select the target user. Identify the terminal and check the latest connection status (S316, S317).
Relay server A20 establishes a path with relay server B30, which is the switching destination relay server (S318), and relay server B30 establishes a path with relay server A20, which is the switching source relay server (S319). A path is established between the relay server A20 and the relay server B30 (S320).
The relay server A20 and the relay server B30 notify the corresponding terminal group of the switching instruction (S321, S322). In this embodiment, the relay server A20 instructs the user terminal 93 to switch (S323).
The user terminal 93 receives the switching instruction (S324).
The user terminal 93 and relay server A20 disconnect the main path (S335, 336).

The user terminal 93 transmits a connection request to the relay server B30 (S361) in order to establish a main path connection with the relay server B30 (S360).
The relay server B30 establishes a main path connection with the user terminal 93 (S362).
After that, the user terminal 93, relay server A20, and relay server B30 determine that switching is complete (S337, S338, S339).

The relay server A20 updates and manages the connection-related information (S340). The user terminal 93 manages connectable NW information and each IF information (MAC address, IP address, etc.) (S341), and notifies the relay server B30 of its own information (S342).
The relay server B30 updates and manages the connection-related information (S343). The relay server B30 notifies the connection-related information to the connection destination management server 40 (S344).
The connection destination management server 40 updates and manages the connection-related information (S345).

　An example of information indicating the user's situation, information indicating the situation of the user terminal, and information about the NW is shown in FIG. These may be included in the connection related information. The user terminal 93, the relay server, and the connection destination management server 40 collect and aggregate information indicating the user status, information indicating the status of the user terminal, and information about the NW within their respective jurisdictions, and manage the connection destination. It is conceivable that it is used to determine connection destination switching of the server 40 .

Information for understanding access medium information includes the following information regarding user status, terminal status, and NW status. Information about user status can be illustrative of static information such as user preferences, priorities, profile history, and the like. The information about the terminal status can be exemplified by static information such as H/W information such as available IF and S/W information such as memory resources, and dynamic information such as power status, physical movement parameters (distance, location), Examples include received signal strength (RSS) and signal-to-noise and interference ratio (SINR). The information on the NW situation includes provider status such as charge and security management as static information, and NW resource quality or adjacent NW resources such as base station location information, bandwidth, delay, throughput and device failure status as dynamic information. Examples can be given of the effects associated with NW switching, such as quality, delays associated with disconnection/decision/execution, quality degradation rate, quality improvement rate, and the like.

In addition, as information for grasping APL (Application) information, static information such as APL usage settings for user status, and dynamic information such as APL information being executed and memory resources in use for terminal status are provided. Information can be exemplified.

An operation example of the scheduler will be described with reference to FIG. The schedulers 16 and 26 manage sequence numbers and option storage areas.
Sequence Management: Schedulers 16 and 26 store a sequence number for each packet sent using multipath. Before data transmission of each packet from each IF, the IP header area setting units 15 and 25 store the sequence number in the IP header. This is a sequence number that is unified among multipaths, and the receiving side can integrate packets among multipaths by checking this.

FIG. 11 shows an example of the option storage area. The IP header contains an option storage area. For example, an IP header of 12 to 60 bytes includes an option number storage area (1 byte), a length N storage area (1 byte), and an option value storage area (1 byte). The IP header area setting units 15 and 25 store the flow option and sequence number in the option storage area of the IP header.

(IPv6 extension header)
FIG. 12 shows an example of the IPv6 option storage area (see Non-Patent Document 3, for example). An IPv6 packet has an area called an IPv6 extension header, which is read only for a specified destination. In this area, only the specified destination is read, so even if arbitrary data is stored, the relay node will not malfunction. Therefore, it can be freely replaced. Therefore, by inserting arbitrary multipath option information in this area, multipath establishment (first technique) and sequence number storage (second technique) are established between the user terminal 93 and the service edge server 85. ) may be performed.

(IPv4 option storage area)
FIG. 13 shows an example of the IPv4 option storage area. An IPv4 packet has an IPv4 header option (see, for example, Patent Document 1). The value to be inserted in this area is defined as an option value, and storing an arbitrary value may cause the relay node to malfunction. Therefore, the IP header area setting units 15 and 25 have an optional final position designation display function. The display function specifying the position at the end of an option designates an area for inputting a specified option value, and inserts an arbitrary value after it. Multipath option information is stored in this area. As a result, the IP header area setting units 15 and 25 of the destination device, which is the receiving side, can read the input value of the option final position specification display function without causing the relay node to malfunction.

FIG. 14 shows an example of switching quality. The connection destination control unit 45 of the connection destination management server 40 may determine the necessity of multipath establishment and the packet transmission method based on the quality policy shown in FIG. Specifically, the switching quality is divided into four levels, and the packet transmission method and whether to use single-path or multi-path may be determined for each level.

　Since the service itself expires in a short time, it may be set to level 1 if the session does not need to be continued. At level 1, an IP address change, NW temporary disconnection/reconnection, and an increase in delay on the order of ms due to buffering, etc. are allowed, and an example of such a service is web browsing. In this case, single path switching may be performed.

Level 2 may be used when session continuation is required, but a certain amount of delay is acceptable and temporary NW disconnection is acceptable. At level 2, IP address changes are not allowed, NW temporary disconnection/reconnection, delay increases on the order of ms due to buffering, etc. are allowed, and an example of such a service is telephone. In this case, single path switching may be performed using a common IP address by the virtual IF.

Level 3 may be used when session continuation is required and a certain amount of delay is acceptable, but temporary network disconnection is not acceptable. Level 3 does not allow IP address changes and NW temporary disconnection/reconnection, but allows delay increases on the order of ms due to buffering or the like, and an example of such a service is video streaming. In this case, a common IP address by the virtual IF may be used, multipath switching may be performed, and (1) packet buffering during switching or (2) transmission path change, which will be described later, may be used as the packet transmission method.

Level 4 may be used when session continuation is required and services are affected by temporary network disconnection or increased delay. At level 4, IP address changes, NW temporary disconnection/reconnection, delay increases on the order of ms due to buffering, etc. are not allowed, and examples of applicable services include remote monitoring of autonomous driving. In this case, a common IP address by the virtual IF may be used, multipath switching may be performed, and packet copy, which will be described later, may be used as the packet transmission method.

FIG. 15 shows an example of a packet transmission method. Three patterns are exemplified as the packet transmission method, but the present invention is not limited to these. Here, a case where the option area setting unit transmits a packet to IF1 or IF2 will be described, but the present invention is not limited to this.

In the packet copy of the first pattern, packet copy is performed and the same packet is transmitted from both IFs. Advantages of packet copying include low risk of packet loss because processing can be performed independently of switching processing, light processing on the transmitting side, and little effect of delay. On the other hand, the disadvantage of packet copying is that if nothing is done, duplicate packets will be sent to the NW. As a countermeasure against duplicate packets, it is possible to discard duplicate packets at the multipath termination point, but this increases the processing load.

In the second pattern of packet buffering, sequence number 1 is transmitted from IF1, and after confirming arrival at the receiving side, sequence number 2 is transmitted from IF2. Wait packets are buffered until confirmation of arrival at the receiving side after transmission. Advantages of packet buffering include a low risk of packet loss because packets can be buffered until the switching process is completed. On the other hand, the disadvantages of packet buffering include an increase in delay due to waiting time for confirmation of arrival, and the need for memory for buffering on the transmitting side (and limited capacity).

In the third pattern of packet destination distribution, after sending sequence number 1 from IF1, sequence number 2 is sent from IF2 without waiting for arrival at the receiving side. Advantages of assigning packet transmission destinations include that processing can be performed at the transmission side's discretion and that there is little delay effect. On the other hand, the disadvantages of packet buffering are that it must be linked with the switching process (if it is not linked, the risk of packet loss is high), and the need for reordering processing on the receiving side increases the load on the receiving side. mentioned.

The communication system, communication method, connection destination management server, and program according to the present disclosure can be applied to the information and communication industry.

11-1: Control communication IF section 11-2: Control communication IF section 12-1: IP communication IF section 12-2: IP communication IF section 13: Connection information management section 14: Switching control section 15: IP header area setting section 16: scheduler unit 17: virtual IF unit 18: application control unit 20: relay server A
21-1: Control communication IF section 21-2: Control communication IF section 22-1: IP communication IF section 22-2: IP communication IF section 22-3: IP communication IF section 23: Connection information management section 24: Switching control Unit 25: IP header area setting unit 26: Scheduler unit 30: Relay server B
31-1: Control communication IF section 31-2: Control communication IF section 32-1: IP communication IF section 32-2: IP communication IF section 33: Connection information management section 34: Switching control section 35: Transfer processing section 40: Connection destination management server 41: Control communication IF unit 43: Connection information management unit 45: Connection destination control unit 50: Switching quality estimation server 51: Control communication IF unit 52: Switching quality estimation unit 84: Service master server 85: Service edge server 86: NW-A
87: NW-B
88: NW-C
91: relay server 92: service server 93: user terminal

Claims (7)

1. A communication system comprising: a plurality of relay servers connectable to a user terminal; and a service server connected to the user terminal via the relay server and providing a service to the user terminal,
   a switching quality estimation server for estimating a communication quality required at the time of connection switching of the user terminal; and a relay server connected to the plurality of relay servers and the switching quality estimation server for connecting the user terminal to the service server. and a connection destination management server that manages
   The connection destination management server is connected to the user terminal and the service server, and when switching of a relay server establishing a main path is necessary, a method of switching to a relay server of a switching destination based on an estimation result. and select
   Notifying the switching destination relay server and the switching method to the switching source relay server that has established the main path,
   Upon receipt of the notification, the switching source relay server transmits a path establishment request to the switching destination relay server with respect to its own device, and
   if the switching method is multipath switching, causing the user terminal to transmit a subpath connection request to the switching destination relay server;
   if the switching method is single path switching, causing the user terminal to transmit a main path connection request to the switching destination relay server, and disconnecting the main path between the device and the user terminal;
   The switching destination relay server establishes a subpath or a main path with the relay server that has transmitted the path establishment request and with the user terminal that has transmitted the main path connection request or the subpath connection request, respectively.
   Communications system.
2. When the service server is not connected to the switching destination relay server, the switching source relay server transmits a request to establish a path with its own device to the switching destination relay server. causing the terminal to transmit a subpath connection request to the switching destination relay server;
   The switching destination relay server establishes a sub-path with each of the relay server that has transmitted the path establishment request and the user terminal that has transmitted the sub-path connection request,
   A communication system according to claim 1.
3. A connection destination management server that is connected to a plurality of relay servers connectable to a user terminal and manages the relay servers that connect the user terminal to a service server,
   aggregating connection-related information including application information executed on each user terminal from the plurality of relay servers;
   Acquiring the communication quality required at the time of connection switching of the user terminal estimated based on the aggregated connection-related information,
   selecting a method of switching to a switching destination relay server based on the obtained communication quality when switching of a relay server that is connected to the user terminal and the service server and has established a main path is required;
   notifying the switching source relay server that has established the main path of the switching destination relay server and the switching method;
   Connection destination management server.
4. 4. The connection destination management server according to claim 3, wherein the switching method is multipath switching or single path switching.
5. 5. The connection destination management server according to claim 4, wherein when said switching method is said multipath switching, a packet transmission method for multipaths is also notified as said switching method.
6. A communication method executed by a communication system comprising a plurality of relay servers connectable to a user terminal, and a service server connected to the user terminal via the relay server and providing a service to the user terminal There is
   The communication system is connected to a switching quality estimation server for estimating communication quality required at the time of connection switching of the user terminal, the plurality of relay servers, and the switching quality estimation server, and connects the user terminal to the service server. a connection destination management server that manages the relay server connected to the
   The connection destination management server is connected to the user terminal and the service server, and when switching of a relay server establishing a main path is necessary, a method of switching to a relay server of a switching destination based on an estimation result. and select
   Notifying the switching destination relay server and the switching method to the switching source relay server that has established the main path,
   Upon receipt of the notification, the switching source relay server transmits a path establishment request to the switching destination relay server with respect to its own device, and
   if the switching method is multipath switching, causing the user terminal to transmit a subpath connection request to the switching destination relay server;
   if the switching method is single path switching, causing the user terminal to transmit a main path connection request to the switching destination relay server, and disconnecting the main path between the device and the user terminal;
   The switching destination relay server establishes a subpath or a main path with the relay server that has transmitted the path establishment request and with the user terminal that has transmitted the main path connection request or the subpath connection request, respectively.
   Communication method.
7. A program for realizing a computer as each functional unit provided in the connection destination management server according to any one of claims 3 to 5.

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