JPWO2007023966A1 - Communication device, communication method and communication protocol processing method, communication terminal device and communication method thereof, and communication system and communication method thereof - Google Patents

Abstract

In a communication apparatus having a plurality of communication media, even when the available communication environment changes dynamically, disconnection of communication associated with switching of communication media is prevented. A communication media monitoring / diagnostic unit 11 that periodically monitors the status of communication media possessed by the terminal itself and notifies the monitoring destination of the monitored communication media to the destination terminal, an IP address used for communication, and the communication media An association database 14 holding association information including at least information associated with an identifier for identifying the association, an association transmitting unit 12 for generating a transmission packet with the association information added thereto, and extracting the association information from the received packet And an association receiving unit 13 for updating the stored information in the association database 14 based on the extracted association information.

Description

  The present invention is a communication that can use a plurality of communication media (communication interfaces) such as a portable card mounted on a mobile terminal such as Ethernet (registered trademark), wireless LAN (Local Area Network), or PHS (Personal Handyphone System). The present invention relates to a terminal device, a communication device applicable to the communication terminal device, a communication system having the communication device, and a communication method and a communication protocol processing method in the communication device and the communication system.

  Recently, various communication media such as Ethernet (registered trademark), wireless LAN, PHS and other portable cards can be used as means for accessing a communication network such as the Internet network. Communication devices such as devices and PDAs (Personal Digital Assistants) are equipped with communication media such as Ethernet (registered trademark) and wireless LAN as standard. As for the wireless LAN, a public wireless LAN service in which a wireless LAN access point is installed in a station or town is started.

  In these public wireless LAN services, the Internet connection in a specific area is possible. However, when the communication terminal itself moves and exceeds the radio wave reception area from the wireless LAN access point, the roaming function is used to move the terminal. Some communication service companies offer services that allow communication to continue. However, the public wireless LAN service is basically a service that allows you to connect to the Internet via a wireless LAN when you have moved, providing and guaranteeing seamless communication without interrupting communication even when the communication terminal itself is moving. It is not what you are doing.

  Therefore, when the communication terminal itself moves between public wireless LAN service areas provided by different communication service companies, or moves to a different network network such as a wireless LAN service and moves to an area where there is only an access means using a mobile card. In such a case, it has been necessary to temporarily disconnect the communication between the communication terminals to terminate the service, and to select a usable communication medium and network, and to reconnect and restart the service.

  In addition, for example, in a situation where a mobile card is used to access the Internet network, the mobile network moves to an area where a wireless LAN or Ethernet (registered trademark) faster than the mobile card is laid. Even if it is located in an environment where the communication media can be used immediately, after reconnecting to the wireless LAN and Ethernet (registered trademark) after completing access to the Internet network with the mobile card, High-speed communication media could not be used.

  Furthermore, in communication exceeding the network, that is, communication media to be used, and communication exceeding the domain in which the IP address changes, no means for switching between them has been established, and communication is temporarily disconnected by the communication medium to be used and the communication network that can be used. However, it is necessary for the user to specify the communication medium to be used and to reconnect to an available communication network.

  As a mechanism for performing handover, for example, HMIP (Hierarchical Mobile IP) as shown in FIG. 30 has been proposed, but HMIP is a communication within one network, that is, within a domain using the same IP address system. Provides a handover mechanism for communicating with which access point (AP), and communication beyond the domain has not been taken into consideration.

  In this HMIP, the MAP (Mobility Anchor Point) for switching the access point is located at the exit of the domain, that is, at the router or gateway that is a node interconnected with the external network, and all communication is performed. Since communication is performed via this MAP, when communicating with an external domain, the communication must always be performed via the MAP, which places a burden on the entire communication of the MAP and increases communication charges while reducing the overall communication performance. There was a problem.

  Here, as a conventional technique using a plurality of communication media, a method of switching a communication medium (for example, Patent Document 1) or using a router having a mobile function and causing the router to determine which communication medium to use is used. There has been proposed a method (for example, Patent Document 2) in which possible communication media are registered in advance in the terminal, and a user selects a communication media to be used at the start of communication.

  Further, in the following Patent Documents 3 and 4 and Non-Patent Documents 1 to 4, technologies for switching communication media and concealing IP addresses to be used in a multihome environment are proposed by a new function called an association layer. In particular, Non-Patent Document 1 proposes a network architecture in a multi-home environment as a means for implementing a plurality of communication media.

  Further, in each of the following documents, Patent Document 3, Patent Document 4, Non-Patent Document 2, Non-Patent Document 3, and Non-Patent Document 4, trial evaluation of a network architecture is reported.

JP 2005-12563 A JP 2004-70752 A Japanese Patent Application No. 2005-245037 Japanese Patent Application No. 2006-45758 “Design and Implementation of Association Layer for Realizing Mobility Transparency” Yasusuke Tsuji, IEICE, IEICE Technical Report, March 2004 IEICE “Proposal of Communication Media Optimization Mechanism Considering Communication Quality in Multi-home Environment” Hiroyuki Koga, Hiroro Haraguchi, Katsuyoshi Iida, Yuji Oie, September 2005 The Institute of Electronics, Information and Communication Engineers "Implementation and Evaluation of Communication Media Optimization Method in Multi-home Environment" Hiroaki Haraguchi, Hiroyuki Koga, Katsuyoshi Iida, Yuji Oie, September 2005 IEICE “Design and Implementation of Multihome Communication Media Optimization Function Considering Communication Quality” Hiroaki Haraguchi, Hiroyuki Koga, Katsuyoshi Iida, Yuji Oie, March 2006

  Conventionally, in communication terminals such as notebook PCs and PDAs that have a plurality of communication media and can access the Internet in a multi-home environment, the communication media used by the user must be changed according to the environment in which the communication terminal is used. In Non-Patent Documents 1 to 3, the communication medium is switched without making the user of the communication terminal aware of it, and the function of the association layer that hides the IP address added to the communication medium to be used. Even if the communication media to be used is switched, the user application can perform communication without interruption, and seamless communication has been realized.

  However, even in the association layer functions shown in Non-Patent Documents 1 to 3, there are environments in which the communication state is inferior, for example, two wireless LAN environments, and a communication terminal moves between them to move from one wireless LAN environment to the other wireless LAN environment. When switching to a LAN environment, there is a problem that communication is temporarily disabled during the time required for the switching, and communication packet loss or retransmission may occur.

  Further, for example, even if an environment capable of accessing the Internet network is prepared using a plurality of communication media provided in the communication terminal device, in the conventional technology described above, the user himself / herself sets the communication terminal. The communication media to be used must be selected according to the environment in use, and it is difficult for users who do not have sufficient knowledge about the communication environment or communication media to effectively use the communication media according to the communication environment. There was a problem that.

  In addition, when changing the available communication media with the physical movement of the communication terminal device, the user himself / herself temporarily terminates the current communication and then newly uses the communication media. There is a problem in that it is difficult to switch communication media having excellent mobility, because it has to be reconnected using the network.

  On the other hand, even in a communication method having an association layer function, a communication media switching function has been proposed as a function of both communication terminals that perform communication, and it takes time for signaling when switching communication media, that is, handover processing, There are problems such as temporary interruption of communication, loss of communication packets, and retransmission processing.

  Furthermore, in the past, in the communication beyond the domain where the network, that is, the IP address system is changed, the handover mechanism at the time of exceeding the domain has not been provided. A mechanism for providing communication was not established.

  Therefore, when communication is performed via the MAP that manages inter-domain communication, all communication packets pass through the MAP. Therefore, the communication efficiency depends on the communication packet processing capability of the MAP, and the communication packet There is a problem in that the communication efficiency of the entire network decreases as the amount increases.

  The present invention has been made in view of the above, and prevents disconnection of communication due to switching of communication media and is conscious of the user even when the available communication environment changes dynamically. It is an object of the present invention to provide a communication device and a communication method capable of realizing switching control of communication media without being performed, and a communication protocol processing method in the communication device.

  In addition, the present invention provides a communication terminal apparatus and communication having a multipath communication function with high reliability and mobility without causing deterioration in communication performance such as temporary packet loss and retransmission during a transition period when switching to a different network It aims to provide a method.

  In addition, the present invention provides a communication system and a communication method capable of reducing the processing time required for handover and enabling smooth handover processing and seamless communication even for handovers across domains. The purpose is to do.

  In addition, the present invention provides a communication system and a communication method in which a communication terminal itself enables active and autonomous communication path selection even in communication via MAP and suppresses a decrease in communication efficiency. For the purpose.

  In order to solve the above-described problems and achieve the object, a communication apparatus according to claim 1 is a communication apparatus applied to a communication terminal apparatus having a plurality of communication media as an access means to a predetermined network. Communication medium monitoring means for periodically monitoring the state of the communication medium possessed by the communication medium, communication medium diagnosis means for notifying the destination terminal of the monitoring result of the monitored communication medium, the IP address used for communication, and the communication medium An association database that holds association information that includes at least information associated with an identifier for identifying, association transmission means for generating a transmission packet to which the association information is added, and extracting the association information from the received packet; Extracted association information It is characterized in that and a association receiving means for updating the stored information of the association database based on.

  The communication apparatus according to claim 2 is the communication apparatus according to claim 1, wherein the association database stores information associating an IP address used by the communication medium with an identifier used by a predetermined application. It is characterized by being.

  According to a third aspect of the present invention, there is provided the communication device according to the first or second aspect, wherein the communication media monitoring means is provided on an association layer functioning between a network layer and a transport layer on a protocol stack. The functions of the communication media diagnosis unit, the association transmission unit, the association reception unit, and the association database are implemented.

  According to a fourth aspect of the present invention, there is provided the communication apparatus according to the first aspect, wherein the association database stores information indicating a priority order of the communication media.

  The communication device according to claim 5 is the communication device according to claim 1, wherein the communication media monitoring means constantly or periodically monitors communication traffic transmitted and received by the communication media of the terminal itself, The communication medium used by the terminal is switched based on the monitoring information.

  The communication apparatus according to claim 6 is the communication apparatus according to claim 1, wherein the association database stores grouping information in which communication media used for each communication flow and their priorities are grouped. It is characterized by being.

  A communication apparatus according to claim 7 is characterized in that, in the communication apparatus according to claim 1, usable communication media and a priority order regarding the communication media can be set by a user.

  The communication method according to claim 8 is a communication method applied between communication terminal devices having a plurality of communication media as means for accessing a predetermined network, and identifies an IP address used for communication and the communication media. An association database for holding association information including at least information associated with an identifier for performing communication, and a communication media monitoring step for periodically monitoring the state of communication media possessed by the terminal, and stored in the association database An association transmission step for generating and outputting a transmission packet to be transmitted to the destination terminal based on the association information being received, and an association for updating the stored information in the association database based on the association information extracted from the received packet And ® down receiving step and is characterized in that it comprises.

  The communication method according to claim 9 further includes a communication media diagnosis step of notifying a transmission destination terminal of a monitoring result obtained by monitoring a state of the communication media in the communication method of claim 8, wherein the association reception step includes: The storage information of the association database is updated based on the monitoring result of the communication media provided in the transmission source terminal notified in the communication media diagnosis step.

  A communication protocol processing method according to claim 10 is a communication protocol processing method applied to an association layer interposed between a network layer and a transport layer on a protocol stack, and is notified of a communication medium of a notified partner terminal Based on the status information of the terminal, the database provided in the own terminal is updated, and the status information concerning the communication medium of the own terminal, the priority information concerning the communication medium notified from the partner terminal, and the database in the own terminal are stored. The communication media of the local terminal and the partner terminal when transmitting the transmission packet are determined based on the status information of the communication medium related to the partner terminal.

  The communication protocol processing method according to claim 11 is the communication protocol processing method according to claim 10, wherein each communication medium and priority information that can be used between terminals are mutually notified and the response is confirmed. Thus, it is characterized in that the communicable state of the counterpart terminal is confirmed.

  A communication protocol processing method according to a twelfth aspect is the communication protocol processing method according to the tenth or eleventh aspect, wherein the communication medium information to be used and the priority order information are mutually communicated to the partner terminal. It is a feature.

  According to a thirteenth aspect of the present invention, there is provided a communication terminal apparatus having a plurality of communication media as means for accessing the Internet network, wherein a communication medium of the partner communication terminal is transferred from one communication medium of the own communication terminal. The multi-path communication for transmitting the same user data is executed, the same user data sent from the partner communication terminal is received by the communication medium of the own communication terminal, and the user data received earlier in time Multipath transmission / reception means for discarding user data that is passed to the application and received later in time is provided.

  A communication terminal apparatus according to claim 14 is the communication terminal apparatus according to claim 13, wherein the multipath transmission / reception means transmits and receives user data using a plurality of communication media. The means for exchanging the IP address information of the communication media possessed by each other and the association information for identifying the communication partner are created and the association information is added to the communication packet. Means for transmitting user data.

  The communication terminal apparatus according to claim 15 is the communication terminal apparatus according to claim 14, wherein the multipath transmission / reception means identifies communication media possessed by the partner communication terminal based on the association information, and stores the same user data. At the same time, it transmits to a plurality of communication media possessed by the partner communication terminal.

  The communication terminal apparatus according to claim 16 is the communication terminal apparatus according to claim 14, wherein the multipath transmitting / receiving means receives user data received from a plurality of communication media by a user data identifier added to association information. It is characterized in that it is discriminated and it is determined whether the user data is passed to the upper application or discarded based on the identification result.

  A communication terminal apparatus according to claim 17 is the communication terminal apparatus according to claim 13, wherein the multipath transmission / reception means includes communication quality monitoring means for monitoring communication quality, and monitoring of the communication quality monitoring means. A multipath communication start request packet that requests to start the multipath communication is transmitted based on the result, and a multipath communication stop request packet that requests to stop the multipath communication is transmitted based on the monitoring result. It is characterized by doing.

  A communication terminal apparatus according to claim 18 is the communication terminal apparatus according to claim 17, further comprising transmission instruction means for instructing transmission of the multipath communication start request packet and the multipath communication stop request packet. It is what.

  The communication terminal device according to claim 19 is the communication terminal device according to claim 13, further comprising means for transmitting a command for starting and stopping multipath communication to a plurality of communication media possessed by the counterpart communication terminal. It is characterized by comprising.

  According to a twentieth aspect of the present invention, there is provided a communication method having a plurality of communication media as means for accessing the Internet network, and performing communication using the plurality of communication media. Performs multipath communication that transmits the same user data to multiple communication media held by the communication terminal, and receives the same user data sent from the partner communication terminal using the communication media held by the own communication terminal. The user data received earlier is handed over to the upper application, and the user data received later in time is discarded.

  The communication system according to claim 21 is a mobile terminal having a domain in which communication is possible using the same IP address system as a domain, moving between the plurality of domains, and having a plurality of usable communication media. (MH: Mobile Host) and a management server (MAP: Mobile Anchor Point) having a function of managing at least the communication media used by the mobile terminal and the IP address of the mobile terminal. The server is characterized in that it is installed outside the domain area.

  The communication system according to claim 22 is the communication system according to claim 21, wherein the mobile terminal detects a communication state of a communication medium used by itself and a deterioration in communication load, and a change in communication status. And switching means to switch communication media to be used, and when the mobile terminal detects a communication state or communication load deterioration of the communication media to be used, the mobile terminal notifies the management server of the detection status, and the management The server changes communication performed between the mobile terminal and the communication partner mobile terminal to the self management server for each of the mobile terminal and the communication partner mobile terminal with which the mobile terminal is communicating. It is characterized by notifying.

  The communication system according to claim 23 is the communication system according to claim 21 or 22, wherein the management server is communicating with means for detecting a communication load state of communication via the self-management server. Means for periodically notifying the mobile terminal of the detected communication load state, wherein the mobile terminal communicates via the management server (MAP) based on the communication load state notified from the management server. And a means for selecting whether to perform communication not via the management server (communication without MAP communication).

  A communication method according to claim 24 is a mobile terminal having a domain in which communication is possible using the same IP address system as a domain, moving between the plurality of domains, and having a plurality of usable communication media. (MH: Mobile Host) and at least a communication server used by the mobile terminal and a management server (MAP: Mobile Anchor Point) having a function of managing the IP address of the mobile terminal It is a communication method, characterized in that signaling control related to handover of switching of communication media used by the mobile terminal is mainly performed from the management server side installed outside that does not include each domain area. To do.

  The communication method according to claim 25 is the communication method according to claim 24, wherein when the mobile terminal detects a communication state of a communication medium to be used or a deterioration in communication load, the control indicates the detection status. The packet is transmitted to the management server, and the management server performs communication between the mobile terminal and the communication partner mobile terminal with respect to the communication partner mobile terminal with which the mobile terminal is communicating. A control packet for changing the communication packet addressed to the self-management server is transmitted.

  Further, the communication method according to claim 26 is the communication method according to claim 24 or 25, wherein the management server detects a communication load state of communication via the self-management server and performs communication while performing communication. Whether the mobile terminal periodically notifies the detected communication load state to the terminal, and the mobile terminal performs communication via the management server (communication via MAP) based on the communication load state notified from the management server , Whether to perform communication not via the management server (communication without MAP) is selected.

  According to the communication apparatus according to claim 1, an identifier for notifying the transmission destination terminal of a monitoring result obtained by periodically monitoring the state of the communication medium possessed by the terminal, and identifying the IP address used for communication and the communication medium Is stored in the association DB, and transmission packets to which the association information is added are transmitted and received, and the stored information in the association database is updated based on the association information extracted from the transmission and reception packets. As a result, the continuity of communication can be ensured without making the terminal user aware of switching of communication media.

  According to the communication method of the eighth aspect, the association information including at least information relating the IP address used for communication and the identifier for identifying the communication medium is held in the association database, and the communication possessed by the terminal itself Periodically monitors the media status, generates and outputs a transmission packet to be sent to the destination terminal based on the association information stored in the association database, and stores information in the association database based on the association information extracted from the received packet As a result, the continuity of communication can be ensured without making the terminal user aware of switching of communication media.

  Further, according to the communication protocol processing method according to claim 10, the database in the own terminal is updated based on the notified state information of the communication medium of the partner terminal, and the state information related to the communication medium of the terminal and the partner terminal Based on the priority information of the communication media notified from the communication media and the status information of the communication media related to the other terminal held in the database in the own terminal. Since the communication medium is determined, for example, when a communication abnormality occurs in the communication terminal, the communication medium switching is actively notified to the partner communication terminal, and the partner communication terminal receiving the notification actively Since the database is updated, it is possible to realize real-time switching of communication media.

  In addition, according to the communication terminal device of the thirteenth aspect, since the function of transmitting and receiving the same user data using a plurality of communication media is implemented, the communication terminal can be used by moving the place where the communication terminal is used. Even if the network changes dynamically, the communication quality of one communication medium deteriorates, and user data cannot be received, the user data can be received by the other communication medium, so communication is not interrupted. High communication quality can be provided. Moreover, high mobility can be provided without making the user aware of changes in the network state.

  According to the communication method of claim 20, since the function of transmitting and receiving the same user data using a plurality of communication media is implemented, a network that can be used by moving a place where the communication terminal uses it. Even when the network changes dynamically, the communication quality of one communication medium deteriorates and user data cannot be received, the user data can be received by the other communication medium, so communication is not interrupted, High communication quality can be provided. Moreover, high mobility can be provided without making the user aware of changes in the network state.

  Further, according to the communication system according to claim 21, the management server (MAP) is installed outside the domain to be moved, and the handover process for switching the communication media is performed, so that the HMIP proposed so far is performed. In addition to the communication media switching function in the domain, a handover function in communication beyond the domain is provided, and seamless communication can be provided in the inter-domain communication of the mobile terminal.

  Further, according to the communication system according to claim 22, the management server (MAP) performs the signaling process for switching the communication media of the mobile terminal to control the communication path, thereby performing the signaling process for both communications. This eliminates the need to perform it between terminals, reduces the overhead for the handover process, and improves the communication efficiency.

  According to the communication system of claim 23, the mobile terminal that has received the load information of the management server actively and autonomously communicates via the management server (MAP) by the load information notification function of the management server (MAP). It is possible to improve the communication efficiency by determining the communication efficiency of the communication (routed communication) and the communication not passing through the management server (non-MAP communication) and selecting the communication path to be used.

  Further, according to the communication method of claim 24, a management server (MAP) is installed outside the domain to be moved, and a handover process for switching communication media is performed, so that the HMIP proposed so far, etc. In addition to the communication media switching function in the domain, a handover function in communication beyond the domain is provided, and seamless communication can be provided in the inter-domain communication of the mobile terminal.

  According to the communication method of claim 25, the management server (MAP) performs the signaling processing for switching the communication media of the mobile terminal to control the communication path, whereby the signaling processing is performed for both communications. This eliminates the need to perform it between terminals, reduces the overhead for the handover process, and improves the communication efficiency.

  According to the communication method of claim 26, the load information notification function of the management server (MAP) enables the mobile terminal that has received the load information of the management server to actively and autonomously communicate via the management server (MAP). It is possible to improve the communication efficiency by determining the communication efficiency of the communication (routed communication) and the communication not passing through the management server (non-MAP communication) and selecting the communication path to be used.

FIG. 1 is a diagram showing a hierarchical structure (hereinafter simply referred to as “protocol stack”) of communication protocols common to the embodiments of the present invention. FIG. 2 is a block diagram showing a functional configuration of the association layer. FIG. 3 is a diagram illustrating an example of a storage state of data stored in the association DB. FIG. 4 is a diagram illustrating state transitions in the association layer. FIG. 5 is a diagram showing a packet structure of a control packet used in the communication protocol of the association layer (hereinafter referred to as “association protocol”). FIG. 6 is a diagram showing a format of the association header shown in FIG. FIG. 7 is a diagram showing a format of the “Flag” field shown in FIG. FIG. 8 is a diagram showing a format of the address list header shown in FIG. FIG. 9 is a diagram showing a format of the preference list header shown in FIG. FIG. 10 is a sequence diagram illustrating a communication procedure between terminals when an association is established. FIG. 11A is a flowchart illustrating a processing procedure in the transmission source terminal when the association is established. FIG. 11-2 is a flowchart illustrating a processing procedure in the transmission destination terminal when the association is established. FIG. 12 is a diagram illustrating a frame structure after the association is established. FIG. 13A is a flowchart of a processing procedure in the transmission source terminal after the association is established. FIG. 13-2 is a flowchart illustrating a processing procedure in the transmission destination terminal after establishment of the association. FIG. 14A is a sequence diagram illustrating an outline of a communication procedure (normal TCP / IP communication) between terminals after establishment of an association. FIG. 14-2 is a sequence diagram illustrating an overview of a communication procedure (association communication) between terminals after establishment of an association. FIG. 15A is a diagram (in a normal state) for explaining the communication media switching process by the communication media monitoring function. FIG. 15B is a diagram for explaining communication media switching processing by the communication media monitoring function (during malfunction). FIG. 16 is a flowchart showing a communication media switching process procedure by the communication media monitoring function. FIG. 17 is a sequence diagram illustrating a communication procedure for an address change notification between transmitting and receiving terminals. FIG. 18 is a sequence diagram illustrating a communication procedure for diagnosis notification between the transmitting and receiving terminals. FIG. 19 is a flowchart illustrating a processing procedure of a diagnosis process and a diagnosis result notification process by the communication media diagnosis function. FIG. 20 is a sequence diagram illustrating a communication procedure for association release processing. FIG. 21 is a flowchart illustrating a procedure of the association release process. FIG. 22 is a sequence diagram illustrating a communication procedure for communication flow control between the transmitting and receiving terminals using the preference list header. FIG. 23A is a diagram (before change control) for explaining change control of a communication medium in use. FIG. 23-2 is a diagram (after change control) for explaining change control of a communication medium in use. FIG. 24 is a functional block diagram of the association layer used in the present invention. FIG. 25 is a diagram showing a frame format for control flag bit assignment. FIG. 26 is a functional block diagram illustrating a data transmission operation from a terminal that has issued a multipath communication start request. FIG. 27 is a sequence diagram illustrating a data transmission operation from a terminal that has issued a multipath communication start request. FIG. 28 is a functional block diagram illustrating a data transmission operation from a terminal that has received a multipath communication start request. FIG. 29 is a sequence diagram illustrating a data transmission operation from a terminal that has received a multipath communication start request. FIG. 30 is a diagram illustrating the HMIP communication model according to the prior art and the flow of data and a handover signal in the communication model. FIG. 31A is a diagram illustrating an example of a communication model according to the fifth embodiment of the present invention and the flow of data and a handover signal in the communication model (when not passing through the MAP). FIG. 31-2 is a diagram illustrating a flow of data and a handover signal (in the case of passing through a MAP) in the communication model illustrated in FIG. 31-1. FIG. 32 is a diagram showing a handover sequence in the fifth embodiment of the present invention. FIG. 33 is a diagram illustrating an example of a simulation model according to the fifth embodiment. FIG. 34 is a diagram illustrating an example of a simulation model according to the sixth embodiment. FIG. 35 is a chart showing simulation results when handover is performed between MH and CH and when handover processing is reduced via MAP. FIG. 36 is a chart showing a simulation result performed under the same conditions as FIG. 35 except that communication traffic exists in the background.

Explanation of symbols

5 Network layer 6 Transport layer 10, 32, 42, 50 Association layer 11 Communication media monitoring / diagnostic unit 12 Association transmission unit 12a Association data creation unit 12b IP header conversion / transmission unit 13 Association reception unit 13a Packet reception unit 13b IP header Conversion unit 14, 54 Association database 20 Ethernet (registered trademark) header 21 IP header 22 Association control data 25 Association header 26 Address list header 27 Preference list header 28 Upper layer data 30 Source terminal 33, 34, 43, 44 Communication media 40 Destination terminal 51 Communication quality monitoring unit 52 Multipath communication transmission unit 53 Multipath communication reception unit A, B Communication terminal

  Hereinafter, embodiments of a communication device, a communication method and a communication protocol processing method, a communication terminal device and a communication method thereof, and a communication system and a communication method according to the present invention will be described in detail with reference to the drawings. Note that the present invention is not limited to these embodiments.

[Embodiment 1]
FIG. 1 is a diagram showing a hierarchical structure (hereinafter simply referred to as “protocol stack”) of communication protocols common to the embodiments of the present invention. As shown in the figure, in this protocol stack, a protocol called “association layer” is installed between a general “network layer” and “transport layer”. The reason for implementing such a layer is to add a function of continuing predetermined communication while automatically switching the optimum communication medium in real time according to the communication environment.

  In the following description, the “TCP / UDP protocol” is implemented in the transport layer, which is the upper layer of the association layer shown in FIG. 1, and the “IP protocol” is implemented in the network layer, which is the lower layer. The case will be described as an example. It should be noted that the function of the association layer according to the present invention is not limited to these protocols and can be applied widely to other protocols.

(Association layer functions-overall functions)
Next, a schematic function (overall function) of the association layer shown in FIG. 1 will be described. The association layer receives a packet transmission request from the transport layer (TCP / UDP layer) which is an upper layer, processes association information, and outputs a transmission request to the network layer (IP layer) which is a lower layer. On the other hand, when a received packet is transmitted from the lower IP layer, the transmitted association information is processed, and the packet is transferred to the upper TCP / UDP layer. Here, the “association information” is information that associates an IP address used for communication with a host identifier for identifying each host. In addition, “association” refers to a state in which mobility is secured between terminals (or between applications between each terminal) that may change the IP address based on this association information, or to ensure mobility This is the process to do. In this way, the concept of “association” is a concept that does not belong to either “flow control” mainly performed in the transport layer or “route control” mainly performed in the network layer. By newly defining the concept of association between the transport layer and the network layer, the influence on existing applications that are used on the assumption of the functions of the transport layer and the network layer may be localized. It becomes possible.

(Association layer functions-main components)
Next, the function of the association layer will be described. FIG. 2 is a block diagram showing a functional configuration of the association layer. As shown in the figure, the association layer 10 includes a communication media monitoring / diagnostic unit 11, an association transmission unit 12, an association reception unit 13, and an association DB 14, which operate between the network layer 5 and the transport layer 6. These four functional units are configured as main components.

(Association layer functions-main components-communication media monitoring / diagnostics)
The communication media monitoring / diagnosis unit 11 includes a communication media monitoring function and a communication media diagnosis function. The communication media monitoring function periodically determines the state of the communication media based on, for example, the output time of an internal timer provided in the association layer in order to determine, for example, the disconnection of the communication cable or the outside of the radio wave reception area in the wireless LAN. To monitor automatically. If an abnormal state of the communication media of the own terminal is detected, immediately switch the communication media used by the own terminal and send a communication media change notification to the partner terminal using the switched communication media. Do. The communication media diagnosis function is activated by, for example, an internal timer, and performs a process of periodically notifying the state of communication media possessed by the terminal itself.

(Association layer functions-main components-association transmitter)
The association transmission unit 12 includes an association information addition function for adding an association header 25 to the transmission packet and a communication media selection function for selecting a communication medium as a transmission means for transmission data.

  The association information addition function in the association transmission unit searches the association DB 14 based on the IP address of the own terminal and the IP address of the partner terminal set in the transmission data from the transport layer, which is an upper layer. When the relevant association information is retrieved, the association header 25 is added to the header portion of the transmission data from the upper layer, and the association protocol number is set in the upper protocol field of the IP header. If it is determined that the association DB 14 is not applicable, the association header 25 is not added, and the upper protocol field of the IP header is not set, and a normal TCP / IP frame is generated and the lower layer is used. It is transmitted to a certain network layer (IP layer).

  In addition, the communication media selection function in the association transmission unit is a process for determining the IP address of the communication media of the local terminal to be transmitted and the IP address of the communication media of the counterpart terminal to be transmitted based on the data corresponding to the search of the association DB 14. I do. When the transmission source IP address and the transmission destination IP address set in the transmission data from the upper layer are different from the IP address searched in the association DB 14, the transmission destination IP address in the transmission data, Then, the transmission source IP address is changed, and the transmission data generated at this time is transferred to the lower IP layer. Each of these functions is implemented by the association data creation unit 12a and the IP header conversion / transmission unit 12b provided in the association transmission unit 12.

(Association layer functions-main components-association receiver)
The association receiving unit 13 receives a packet reception notification from the lower IP layer, and performs an association header processing function for processing the association header 25 and a conversion process for the IP header set in the received data. An IP address conversion function is provided.

  The association header processing function in the association receiver checks the upper protocol field included in the IP header of the received packet sent from the IP layer, and if the association protocol number is included, the transmission included in the received packet The association DB 14 is searched based on the destination IP address and the source IP address. When the relevant association information is retrieved, the association header 25 is processed, deleted from the received packet, and processed into a normal TCP / IP packet format. If no association protocol is set in the upper protocol field of the IP header, association header processing is not performed.

  Further, the IP address conversion function in the association receiving unit determines a source IP address and a destination IP address to be passed to the upper layer based on the data hit in the search in the association DB 14. If the source IP address and destination IP address set in the received packet are different from the IP address searched in the association database, the destination IP address and source IP address in the received packet And the received packet is passed to the upper layer TCP / UDP layer. Each of these functions is implemented by the packet receiving unit 13a and the IP header converting unit 13b provided in the association receiving unit 13.

(Association layer function-main components-association DB)
FIG. 3 is a diagram illustrating an example of a storage state of data stored in the association DB 14. As shown in the figure, the association DB 14 has an association ID (“Source. Assoc. ID”, “Dest. Assoc. ID”) for managing the association, and an IP address list (“IP Address 1”, “ Information such as “IP Address 2”,... “IP Address N”) and priority (not shown) is stored in association with each other. Note that the data stored in the association DB 14 is related to the local terminal when the communication medium of the local terminal becomes unusable due to, for example, an Ethernet (registered trademark) cable disconnection or movement outside the radio wave reception area. The status and priority of the communication medium is updated. Further, when a communication media state change notification packet and a diagnostic packet are received from the partner terminal, the state and priority of the communication medium related to the partner terminal are updated.

(Association layer state transition)
FIG. 4 is a diagram illustrating state transitions in the association layer. The association layer establishes an association between both terminals by performing negotiation based on the association information when starting communication with the counterpart terminal. Hereinafter, states that the association layer can take and state transitions between these states will be described.

  The state “IDLE” is a state before starting communication with the partner terminal.

  Further, the state “Init Sent” is a transmission packet (“INIT” packet) in which the initialization bit is set to start communication with the partner terminal (Send “INIT”). State.

  On the other hand, the state “Init Receive” receives an initialization packet (“INIT” packet) from the partner terminal (Recv “INIT”), and sets a packet (“INIT + ACK”) with an initialization bit and an acknowledgment (acknowledge) bit. ”Packet) is transmitted (Sent“ INIT + ACK ”), and is a transition state on the receiving terminal side waiting for an acknowledgment packet from the partner terminal.

  Further, the state “Associated” is a state in which the negotiation between the two terminals is successful and the association can be established. Here, when the state before the transition is the state “Init Sent”, a packet (“INIT + ACK” packet) in which the initialization bit and the acknowledgment (acknowledge) bit are set is received from the partner terminal (Recv “INIT + ACK”). )), An acknowledgment packet (“ACK” packet) is transmitted to the partner terminal (Send “ACK”), and then the state transits to “Associated”. On the other hand, when the state before the transition is the state “Init Receive”, the state transitions to the state “Associated” when an acknowledgment packet (“ACK” packet) is received (Recv “ACK”) from the partner terminal. Note that during the state “Associated”, communication between both terminals performs transmission and reception of packets based on the association information exchanged when the association is established. Further, after the transition to the “Associated” state, both the communication media monitoring function and the diagnostic function described above become effective.

  In the state “No Associated”, an initialization packet (“INIT” packet) is transmitted to the partner terminal, but an acknowledgment packet (“ACK” packet) is not returned and time-out occurs, or a negative response packet (“NAK”). Packet (not shown) is returned and the negotiation has failed. In this “No Associated” state, the counterpart terminal may be handled as a device that does not support association, and subsequent communication may be performed using normal TCP / IP communication without using the association function.

  When the communication with the partner terminal is actively terminated, the state “Release” transmits a packet (“REL” packet) in which the association release bit is set (Send “REL”) to the partner terminal. Is waiting for reception of an acknowledgment packet from. After receiving an acknowledgment packet from the counterpart terminal (Recv “ACK”), the state transits to “IDLE”. On the other hand, when the association release packet (“REL” packet) is passively received (Recv “REL”) in the state “Associated”, an acknowledgment packet is transmitted (Send “ACK”) to the partner terminal, Transition to “IDLE”.

(Packet structure of control packet used in association protocol)
FIG. 5 is a diagram showing a packet structure of a control packet used in the communication protocol of the association layer (hereinafter referred to as “association protocol”). As shown in the figure, association control data 22 added at the time of processing in the association layer is inserted on the upper side of the IP header 21. The association control data 22 includes three header parts, an association header 25, an address list header 26, and a preference list header 27. The association header 25 is transmitted / received when communication using an association protocol is performed. Always inserted in every packet. On the other hand, the address list header 26 and the preference list header 27 are inserted into the upper layer side of the association header 25 (the side opposite to the side where the IP header 21 is inserted) as necessary.

(Control packet-association header format)
FIG. 6 is a diagram showing the format of the association header 25 shown in FIG. In the figure, the association header 25 has six fields of “Next Header” field, “Flag” field, “Flow-ID” field, “Sequence” field, “Source Host-ID” field, and “Destination Host-ID” field. Consists of fields.

(Control packet-Association header-"Next Header" field)
The “Next Header” field is composed of 8 bits, and the protocol number of the header to be inserted next to the association header 25 is set. When the address list header 26 or the preference list header 27 is inserted next to the association header 25, the association protocol number is set in the “Next Header” field. On the other hand, if there is no subsequent address list header 26 or preference list header 27, a protocol number such as a higher layer TCP / UDP is set.

(Control packet-Association header-"Flag" field)
FIG. 7 is a diagram showing a format of the “Flag” field shown in FIG. In the figure, the “Flag” field is composed of 8 bits, and bits for controlling the association protocol such as “INIT”, “ACK”, “REL”, “ADDR”, “DATA” are assigned.

(Control packet-Association header-"Flow-ID" field)
The “Flow-ID” field is composed of 4 bits and indicates the number of the flow list to be exchanged in the preference list header 27. If the reservation number “0” is designated in the “Flow-ID” field, the preference list means unused.

(Control packet-Association header-"Sequence" field)
The “Sequence” field is composed of 12 bits, and is incremented by one every time an association packet is transmitted as the sequence number of the association packet.

(Control packet-Association header-"Source Host-ID" field)
The “Source Host-ID” is composed of 128 bits of 16 bytes, and is determined based on a random number generated in the own terminal as an ID for identifying the own terminal, and is notified to the partner terminal when negotiating the establishment of the association. .

(Control packet-association header-"Destination Host-ID" field)
“Destination Host-ID” is composed of 128 bytes of 16 bytes, and is determined as an ID for identifying the partner terminal based on a random number generated by the partner terminal during negotiation for establishment of the partner terminal, and is notified to the terminal itself. .

(Control packet-address list header format)
FIG. 8 is a diagram showing the format of the address list header 26 shown in FIG. The address list header 26 includes a “Next Header” field, a “Type” field, a “Length” field, and a plurality of “IP Address” fields.

(Control packet-address list header-"Next Header" field)
The “Next Header” field is composed of 8 bits, and the protocol number of the header inserted after the address list header 26 is set. If a preference list header 27 is inserted after the address list header 26, an association protocol number is set in the “Next Header” field. On the other hand, if there is no subsequent preference list header 27, a protocol number such as TCP / UDP which is an upper layer is set.

(Control packet-Address list header-"Type" field)
The “Type” field is composed of 4 bits and is set with a number indicating that it is an address list.

(Control packet-Address list header-"Length" field)
The “Length” field is composed of 4 bits, and the number of IP addresses related to the communication media possessed by the own terminal set in the “IP Address” field is set.

(Control packet-address list header-"IP Address" field)
The “IP Address” field is composed of 16 bytes of 128 bits, and an IP address added to the communication medium of the terminal itself is set.

(Control packet-preference list header format)
FIG. 9 is a diagram showing a format of the preference list header 27 shown in FIG. The preference list header 27 includes a “Next Header” field, a “Type” field, a “Length” field, and a plurality of “flow information” fields.

(Control packet-Preference list header-"Next Header" field)
The “Next Header” field is composed of 8 bits, and the protocol number of the header inserted after the preference list header 27 is set. If the address list header 26 is inserted after the preference list header 27, an association protocol number is set in the “Next Header” field. On the other hand, when there is no subsequent address list header 26, a protocol number such as TCP / UDP which is an upper layer is set.

(Control packet-Preference list header-"Type" field)
The “Type” field is composed of 4 bits and is set with a number indicating a preference list.

(Control packet-Preferences list header-"Length" field)
The “Length” field is composed of 4 bits, and the number of flow information is set.

(Control packet-Preference list header-"Flow information" field)
Each of the “flow information” fields is composed of 16 bits, the first 4 bits form a “Flow-ID” field, and the remaining 12 bits form a “NIC-No” field for each 4 bits. Here, the flow ID number set in the “Flow-ID” field in the association header 25 is set in the “Flow-ID” field, and the address list header 26 described above is set in the “NIC-No” field. Information indicating the order of IP addresses related to the communication media set in the “IP Address” field is set.

(Communication device operation)
Next, with respect to the operation of the communication apparatus according to the first embodiment, the functions of the association layer characterizing this embodiment are shown in FIGS. 2, 5 to 9, FIG. 10, FIG. 11-1 and FIG. This will be described with reference to each figure. FIG. 10 is a sequence diagram showing a communication procedure between terminals at the time of association establishment, FIG. 11-1 is a flowchart showing a processing procedure at the transmission source terminal at the time of association establishment, and FIG. It is a flowchart which shows the process sequence in the transmission destination terminal at the time of association establishment.

(Communication device operation-Association establishment operation)
Prior to starting communication, the transmission source terminal searches the association DB 14 using the IP address of the transmission destination terminal to determine whether or not there is an association with the transmission destination terminal (step S101 in FIG. 11-1). If the association ID of the transmission destination terminal is not found, it is determined that the association with the transmission destination terminal has not been established (No in step S101). In this case, the transmission source terminal determines a transmission source association ID (Source Host-ID) using its own random number generation function.

  When the transmission source association ID is determined, the following values are set in the fields of the association header 25. That is, in the “Next Header” field, a value “0” indicating that a subsequent header is not added to the rear part of the association header 25 is set. The INIT bit is set in the “Flag” bit. “0” is set in the “Sequence” field. In the “Source Host-ID” field, the association ID of the transmission source is set. “0” is set in the “Destination Host-ID” field. Further, after the association protocol number is set in the protocol portion (not shown) of the IP header 21, the association establishment request packet is transmitted to the destination terminal (the sequence SQ21-23, SQ31 in FIG. 10, FIG. 11- 1 step S102 (the first way).

  The destination terminal that has received the association establishment request packet retrieves the “Source Host-ID” set in the association header 25 of the received packet and searches the association DB 14 in its own terminal to associate with the source terminal. Is determined (step S201 in FIG. 11-2). If the corresponding transmission source association ID is not found, it is determined that the association with the transmission destination terminal has not been established (No in step S201 in FIG. 11-2). In this case, the transmission destination terminal determines its own association ID using its own random number generation function. If the association with the destination terminal is established (step S201 in FIG. 11-2, Yes), the received packet is discarded (step S260 in FIG. 11-2), and the process in step S205 described later is performed. Migrate to

  When the association ID of the own terminal is determined on the transmission destination terminal side, the transmission destination terminal generates an acknowledgment packet including the association header 25 and the address list header 26 as shown below.

  First, the following values are set in each field of the association header 25 of the packet generated at the destination terminal. That is, an association protocol number is set in the “Next Header” field. In the “Flag” field, an “INIT” bit and an “ACK” bit are set. In “Source Host-ID”, an association ID generated in the own terminal is set. In “Destination Host-ID”, the value of “Source Host-ID” in the association establishment request packet transmitted from the transmission source terminal is set.

  In addition, the following values are set in each field of the address list of the acknowledgment packet. That is, a value “0” indicating that there is no subsequent header is set in the “Next Header” field. A value indicating an address list is set in the “Type” field. In the “Length” field, the number of IP addresses included in the address list is set. Further, the IP address added to the communication medium of the destination terminal is set in the “IP address” field.

  The transmission destination terminal sets the association protocol number to the protocol number of the IP header and transmits an acknowledgment packet to the transmission source terminal (the steps S202 to S26, SQ32 in FIG. 10 and steps S202 in FIG. 11-2). processing). In addition, the transmission destination terminal registers information such as its own association ID, partner association ID, and IP address list in the association DB 14 in the transmission destination terminal (step S203 in FIG. 11-2).

  The source terminal that has received the acknowledgment packet extracts the protocol number in the IP header and the “Destination Host-ID” in the association header 25, and checks whether or not it matches the ID set at the time of transmitting the association establishment request packet. .

  When the association IDs of the acknowledgment packet and the association establishment request packet match, the number of IP addresses specified in the “Length” field is extracted from the address list header 26 included in the acknowledgment packet. Then, information such as a self-association ID, a partner association ID, and an IP address list is registered in the association DB 14 in the transmission source terminal (step S103 in FIG. 11-1 (second way processing)).

  After various pieces of predetermined information are registered in the association DB 14, the transmission source terminal generates an acknowledgment packet shown below that includes an association header 25 and an address list header 26.

  First, the following values are set in the fields of the association header 25 of the packet generated at the transmission source terminal. That is, an association protocol number is set in the “Next Header” field. In the “Flag” field, the “ACK” bit is set. In each field of “Source Host-ID” and “Destination Host-ID”, the association ID of the transmission source terminal and the association ID of the transmission destination terminal registered in the association DB 14 are set.

  The following values are set in the fields of the address list header 26 of the acknowledgment packet. That is, a value “0” indicating that there is no subsequent header is set in the “Next Header” field. A value indicating an address list is set in the “Type” field. In the “Length” field, the number of communication media attached to the transmission source terminal is set. Further, in each “IP Address” field, an IP address added to each communication medium of the transmission source terminal is set.

  The transmission source terminal sets the association protocol number to the protocol number of the IP header, and transmits an acknowledgment packet to the transmission destination terminal. (Sequence SQ33 in FIG. 10 and step S104 in FIG. 11-1 (third way processing)). The transmission source terminal registers information such as its own association ID, partner association ID, and IP address list in the association DB 14 in the transmission source terminal (step S105 in FIG. 11-1).

  The destination terminal that has received the acknowledgment packet from the source terminal extracts “Destination Host-ID” in the association header 25 and responds at the time of processing of the sequence SQ32 in FIG. 10 (the same applies to step S203 in FIG. 11-2) It is checked whether or not it matches the association ID set in the acknowledge packet.

  When the ID matches the association ID, the transmission destination terminal extracts the number of IP addresses specified by the “Length” field from the address list header 26 of the received acknowledgment packet. Then, information such as a self association ID, a peer association ID, and an IP address list is registered in the association DB 14 in the self terminal (step S205 in FIG. 11-2).

  Through the above processing, the negotiation for establishing the association is completed between the transmission source terminal and the transmission destination terminal. The subsequent communication is performed using the association ID registered in the association DB 14.

  In addition, in each of the second and third ways, if the association ID is inconsistent, or if a timeout is detected without an acknowledgment being returned, both communication terminals are not associated with an association protocol non-compliant device. Judgment and registration as an unsupported terminal in the association DB 14, and thereafter, communication using a normal TCP / IP protocol is performed.

(Communication device operation-Operation after association is established)
Next, the operation after the association is established will be described with reference to FIGS. 2, 12, 13-1 and 13-2, focusing on the function of the association layer. FIG. 12 is a diagram illustrating an example of a frame structure after the association is established. FIG. 13A is a flowchart illustrating a processing procedure in the transmission source terminal after the association is established, and FIG. 13B is a flowchart illustrating a processing procedure in the transmission destination terminal after the association is established.

  The communication frame shown in FIG. 12 shows an Ethernet (registered trademark) frame transmitted after establishment of an association, and includes an Ethernet (registered trademark) header 20, an IP header 21, an association header 25, and upper layer (TCP / UDP) data. 28. An association protocol number is specified as the protocol number in the IP header 21. In the “Next Header” field in the association header 25, a higher layer protocol number (for example, “8” in the case of TCP) is designated. The association header 25 is created based on information such as a self association ID, a partner association ID, and an IP address list held in the association DB 14 of the transmission source terminal.

  When the transmission destination terminal supports the association function, the initialization of the association is completed in the sequence process described above (Yes in step S301 in FIG. 13-1). In this case, the transmission source terminal The transmission data passed from the upper layer is searched in the association DB 14 (step S302 in FIG. 13-1), and the association header 25 is inserted into the transmission packet and transmitted to the partner terminal (steps S303 to S303 in FIG. 13-1). S305).

  If the destination terminal is a device that does not support association (step S306 in FIG. 13-1), the TCP / UDP data passed from the upper layer is transmitted as it is (step S305 in FIG. 13-1). . If the destination terminal is not an association non-compliant device, that is, if it is an association-compatible device (No in step S306 in FIG. 13-1), after performing the association initialization process (step S307 in FIG. 13-1). TCP / UDP data passed from the upper layer is transmitted.

  On the other hand, the transmission destination terminal that has received the packet transmitted from the transmission source terminal first extracts the upper protocol number in the IP header 21, and when the association protocol number is designated (step S401 in FIG. 13-2). Yes), the association header 25 is taken out and the association DB 14 is searched (step S402 in FIG. 13-2). When the relevant association information is found (step S402 in FIG. 13-2, Yes), association protocol processing such as deleting the association header 25 is performed (step S404 in FIG. 13-2), and the processed packet Is transferred to the upper layer (step S405 in FIG. 13-2). If the corresponding association information is not found (step S403 in FIG. 13-2, No), the received packet is discarded as an invalid packet (step S406 in FIG. 13-2). On the other hand, when the association protocol number is not specified in the upper protocol number of the IP header (No in step S401 in FIG. 13-2), the received packet is transferred to the upper layer as it is.

  FIG. 14-1 is a sequence diagram illustrating an outline of a communication procedure (normal TCP / IP communication) between terminals after the establishment of an association, and FIG. 14-2 illustrates a communication procedure (association communication) between the terminals after the establishment of an association. FIG. When the destination terminal is a device that does not support association, as indicated by the solid line arrow in FIG. 14A, the processing in the association layer is bypassed and normal TCP / IP communication is performed. On the other hand, when the destination terminal is an association-compatible device, TCP / IP communication as indicated by the solid line arrow is performed after the processing in the association layer as indicated by the broken line arrow in FIG. 14-2. Is called.

(Communication Device Operation-Communication Media Switching Operation-Switching Process Procedure)
Next, the communication media switching operation by the communication media monitoring function will be described with reference to FIGS. 15-1, 15-2, and 16. FIG. 15A and 15B are diagrams for explaining communication media switching processing by the communication media monitoring function, and FIG. 16 is a flowchart showing a communication media switching processing procedure by the communication media monitoring function. It is.

  First, the communication media monitoring function of the transmission source terminal 30 shown in FIG. 15A is the communication media that are the first and second communication media periodically provided to the terminal by the timer (not shown) of the association layer 32. The statuses 33 and 34 are monitored. Similarly, the communication media monitoring function of the destination terminal 40 is the state of the communication media 43 and 44 that are the third and fourth communication media that are periodically provided in the own terminal by a timer (not shown) of the association layer 42. Are monitored (steps S501 and S502 in FIG. 16).

  Now, it is assumed that the transmission source terminal 30 uses the communication medium 33 and the transmission destination terminal 40 communicates using the communication medium 43. At this time, as shown in FIG. 15B, a case is considered where the cable of the communication medium 33 of the transmission source terminal 30 is disconnected and the carrier is in an OFF state. Under such circumstances, a communication abnormality of the communication medium 33 is detected by the communication medium monitoring function (step S503, Yes in FIG. 16).

  When an abnormality of the communication medium 33 is detected by the communication medium monitoring function of the own terminal, the transmission source terminal 30 sets an unusable flag for the communication medium in which the abnormality is detected, and performs communication using the communication medium 34. The association DB of the own terminal is updated so as to change to (step S504 in FIG. 16). Further, the transmission source terminal 30 transmits an address change notification to the transmission destination terminal 40 using the communication medium 34 (step S505 in FIG. 16).

(Communication Device Operation-Communication Media Switching Operation-Communication Media Switching Sequence)
Next, a communication media switching process sequence will be described with reference to FIG. FIG. 17 is a sequence diagram showing a communication procedure for address change notification between the transmitting and receiving terminals. The address change notification packet is composed of an association header 25 and an address list header 26 in the association control data 22 shown in FIG. In the “Flag” field of the association header 25, an “ADDR” bit indicating an address change is set (see FIGS. 6 and 7). Further, in the address list header 26, the “IP Address” field corresponding to the communication medium 33 in which an abnormality has been detected has a value indicating unusable (for example, a bit in which all bytes are padded with hexadecimal FFs, hereinafter “all FF bit) is set (see FIG. 8). The packet in which these bits are set is transmitted from the transmission source terminal 30 to the transmission destination terminal 40 (sequence SQ51 in FIG. 17).

  On the other hand, the transmission destination terminal 40 that has received the address change notification extracts the number of IP addresses included in the address list header 26 as specified in the “Length” field, and transmits the transmission source terminal in the association DB 14 in the transmission destination terminal 40. 30 communication media information is updated. In the example of FIG. 3, the IP address field related to the communication medium 33 stored in the association DB of the transmission destination terminal 40 is set to be unusable, for example, with all FF bits embedded therein.

  By notifying this address change, the association DB of the communication media that can be used in the transmission source terminal 30 in which an abnormality has occurred is updated, and the transmission destination partner in the association DB held in the transmission destination terminal 40 is also updated. The IP address can be updated, and there is no inconsistency in address information of communication media used between both terminals.

(Communication device operation-normal data transmission after association is established)
Next, transmission / reception of normal data after establishment of an association between both terminals will be described. First, in the source terminal, the association layer that has received the data transmission request from the upper layer TCP / UDP layer detects the IP address included in the transmission data, and also detects the detected source IP address and destination IP address. The association information held in the association DB 14 is searched based on the above. When association information is detected, a memory having an association header size is secured, and an association header 25 is created from the association information. In the “Next Header” field of the association header 25, the protocol number included in the IP header passed from the upper layer is copied, and the association protocol number is set as the protocol number of the IP header. Hereinafter, the “DATA” bit is set in the “Flag” field of the association header 25, and a value incremented by 1 is set in the “Sequence” field, and the “Source Host-ID” and “Destination Host” are set. In “-ID”, the association ID retrieved from the association DB is set. The association header 25 in which a predetermined value is set is inserted between the IP header of the data requested to be transmitted from the upper layer and the TCP or UDP header.

  Next, the source IP address of the association information is compared with the source IP address in the IP header included in the transmission data passed from the upper layer. If the source IP addresses do not match, it is determined that the source communication media set in the transmission data from the upper layer is unusable, and the IP addresses of the source communication media registered in the association DB 14 are prioritized. Search in order. When a usable communication medium is detected, the IP address of the communication medium using the transmission source IP address in the transmission data is rewritten.

  Similarly, the destination IP address of the association information is compared with the destination IP address in the IP header included in the transmission data passed from the upper layer. If the destination IP addresses do not match, it is determined that the destination communication media set in the transmission data from the upper layer is unusable, and the destination IP address in the transmission data is obtained from the association information. Rewrite to Thereafter, a data transmission request is made to the lower IP layer.

  On the other hand, the destination terminal that has received the packet including the association basic header from the lower IP layer extracts the necessary data from the association header 25 and extracts the extracted “Source Host-ID” and “Destination Host-ID”. Is used to search the association DB 14.

  When association information that matches each of “Source Host-ID” and “Destination Host-ID” is searched, these IP addresses are compared with each other.

  If the source IP address included in the received packet does not match the source IP address obtained from the association information, the source IP address in the IP header included in the received packet is rewritten. That is, the IP address is rewritten to the IP address added to the communication medium that has performed association establishment communication.

  Similarly, if the destination IP address included in the received packet does not match the destination IP address obtained from the association information, the destination IP address in the IP header included in the received packet is rewritten. That is, the IP address is rewritten to the IP address added to the communication medium that has performed association establishment communication.

  After processing the source IP address and the destination IP address, the “Next Header” field included in the association header 25 is copied to the protocol number in the IP header of the received packet. Thereafter, the association header 25 is deleted from the received packet, and the IP header and the header attached after the association header 25 are concatenated to generate a normal TCP / IP packet format.

  In this way, after the IP address conversion processing by the association DB, the association header 25 is deleted, so that a normal TCP / IP packet is generated and delivered to the upper TCP / UDP layer. With these processes, the TCP / UDP layer can perform predetermined communication without being aware of the use of any lower layer and communication media.

(Communication Device Operation-Communication Media Diagnosis Processing and Diagnosis Result Notification Processing)
Next, the communication media diagnosis function of the communication apparatus according to the present embodiment will be described with reference to FIGS. FIG. 18 is a sequence diagram showing a communication procedure for diagnosis notification between the transmitting and receiving terminals, and FIG. 19 is a flowchart showing a processing procedure for diagnosis processing and diagnosis result notification processing by the communication media diagnosis function.

  When the communication media diagnosis function operates, the association layer timer is periodically (periodically) started (step S601 in FIG. 19), and the state of the communication media is checked (step S602 in FIG. 19). The diagnosis result at this time is reflected in the association header 25 and the address list header 26 as in the case of the address change notification accompanying the change of the communication medium. First, an “ADDR” bit indicating an address change is set in the “Flag” field of the association header 25 (see FIGS. 6 and 7). In the “IP Address” field of the address list header 26, an IP address of a communication medium that can be used by the terminal itself is set (see FIG. 8). The transmission source terminal updates the association DB of its own terminal (step S603 in FIG. 19) and notifies the transmission destination terminal of a diagnostic packet including association diagnostic data (SQ61 in FIG. 18, step S604 in FIG. 19).

  The destination terminal that has received such association diagnosis data extracts each information of “Source Host-ID” and “Destination Host-ID” from the association header 25 of the received packet, and extracts the extracted “Source Host-ID” and The association information held in the association DB 14 is searched based on “Destination Host-ID”.

  When the association information matches, the transmission destination terminal transmits an acknowledgment to the transmission source terminal (sequence SQ62 in FIG. 18). In the acknowledgment packet transmitted at this time, “ACK” is set in the “Flag” field of the association header 25, and the value of the association information is set in “Source Host-ID” and “Destination Host-ID”. The When the IP address list included in the address list header 26 of the received packet does not match the IP address list stored in the association DB, the association DB is updated.

  If the association information does not match, it is determined that the association has not been established, the received packet is discarded, and the subsequent diagnosis processing is not performed.

  When the transmission source terminal receives an affirmative response to the diagnosis notification from the transmission destination terminal, the transmission source terminal determines that the association between both terminals is valid, and continues communication.

  On the other hand, when the transmission source terminal detects a timeout without a response to the diagnosis notification from the transmission destination terminal, the transmission source terminal determines that the association between the two terminals is invalid, and performs association release processing.

(Communication device operation-Association release processing)
Next, association release processing performed when it is determined that the association between both terminals is invalid will be described with reference to FIGS. 20 and 21. FIG. FIG. 20 is a sequence diagram showing the communication procedure of the association release process, and FIG. 21 is a flowchart showing the procedure of the association release process.

  The association release process is executed by using these events as a trigger when communication between both terminals is completed and the association becomes unnecessary or when a timeout is detected by the association diagnosis function (sequence in FIG. 20). SQ71).

  The association release packet generated during the association release processing is configured using the association header 25. In the “Flag” field in the association header 25, a “REL” bit indicating association release is set. An association ID to be released is set in “Source Host-ID” and “Destination Host-ID”. After these pieces of information are set, the generated association release packet is transmitted to the destination terminal (sequence SQ72 in FIG. 20, step S701 in FIG. 21).

  The destination terminal that has received the association release packet retrieves the “Source Host-ID” and “Destination Host-ID” set in the association header 25 of the received packet, and searches the association DB in its own terminal. The presence / absence of association release processing is determined.

  When the association information matches, the transmission destination terminal transmits an acknowledgment to the transmission source terminal (sequence SQ73 in FIG. 20). The acknowledgment packet is composed of an association header, the “FLAG” field is set with the “REL” bit and the “ACK” bit, and the “Source Host-ID” and the “Destination Host-ID” have association information. The value of is set. Further, the transmission destination terminal deletes the corresponding association information from the association DB.

  The source terminal that has received the response packet responding to the association release processing from the destination terminal extracts each information of the “Flag” field, “Source Host-ID”, and “Destination Host-ID” from the association header 25 of the received packet. If the extracted information matches (step S702 in FIG. 21), the corresponding information is deleted from the association DB in the own terminal (step S703 in FIG. 21).

  On the other hand, if the association information in the acknowledgment packet does not match, the transmission source terminal discards the packet. When an acknowledgment packet from the transmission destination terminal cannot be received, the corresponding association information is deleted from the association DB in the own terminal with a timeout as a trigger.

  As described above, according to this embodiment, the monitoring result of periodically monitoring the state of the communication medium of the terminal itself is notified to the destination terminal, and the IP address and communication medium used for communication are identified. Association information including at least information associated with an identifier for the association is held in the association DB, a transmission packet to which the association information is added is transmitted / received, and storage information in the association database is updated based on the association information extracted from the transmission / reception packet Thus, the continuity of communication can be ensured without making the terminal user aware of switching of communication media.

  Further, according to this embodiment, when the IP address which is the network layer is changed by using the association layer implemented between the TCP / UDP transport layer and the IP network layer, However, it is possible to maintain the consistency of control parameters such as sequence number, ACK number and window size control function used in communication flow control, which is a transport layer function, and to continue communication of higher-level applications by implementing the function. it can.

  In addition, according to this embodiment, at the start of communication, communication packets that can be used and packets of information indicating their priorities are negotiated between the communication terminals, and communication states between the terminals are mutually established. Since it is stored in a built-in database and communication media is dynamically selected based on the database, there is an effect that a server or agent node for managing the communication state is not required on the network. .

[Embodiment 2]
In this embodiment, referring to FIG. 2, FIG. 5 to FIG. 9 and FIG. 22 for communication flow control between both a transmission source terminal and a transmission destination terminal for communication by preference communication using a preference list header. To explain. FIG. 22 is a sequence diagram showing a communication procedure for communication flow control between the transmitting and receiving terminals using the preference list header.

  First, in order to establish an association between both terminals of a transmission source terminal and a transmission destination terminal that perform communication, a 3-way handshake negotiation is performed as in the first embodiment. After the association is established, the preference list header shown in FIG. 9 is exchanged from the source terminal to the destination terminal (sequences SQ81 and SQ82 in FIG. 22). At this time, the association protocol is set in the “Next Header” field of the association header 25. For “Source Host-ID” and “Destination Host-ID”, values registered in the association DB 14 when the association is established are used.

  Note that the exchange of the preference list header as described above can be performed even after the association is not established. For example, it can be added to the association address option when the association is established. In this case, the preference list header 27 may be added to the rear part of the association header 25 and the address list header 26 in the second-way or third-way negotiation packet at the time of the 3-way handshake for establishing the association.

  As shown in FIG. 9, one flow ID list in the preference list header 27 is composed of a 4-bit flow ID number and an IP address number in 4-bit units. It is possible to specify a maximum of three IP address numbers.

  The IP address number specified in the flow ID list indicates the number of the IP address list that is exchanged in the address list header 26 and registered in the association DB 14 in the negotiation at the time of association. It should be noted that the IP address numbers shown in each address list header 26 can be handled as having a priority order in ascending order of bits.

  The flow ID number of the preference list is set in the “Flow-ID” field (see FIG. 6) of the association header 25. Note that the default value of the “Flow-ID” field is “0”, which means that the preference list header is not used. On the other hand, when the value of the “Flow-ID” field is other than “0”, first, the communication medium specified in the preference list header is preferentially used. By this processing procedure, the user can arbitrarily control the communication path by setting the “Flow-ID” field in the association header 25.

  If “0” is set in the “Flow-ID” field in the association header 25, or if the preference list is not exchanged, that is, if there is no preference list, the destination terminal Searches the address list in the association DB 14, selects a communication medium with a high priority, and transmits the packet to the transmission source terminal using the selected communication medium.

  On the other hand, when a value other than “0” is set in the “Flow-ID” field (see FIG. 6) in the association header 25, the destination terminal sets the value of the “Flow-ID” field from the received packet. Is extracted and stored in its own terminal, and an association process similar to that in the first embodiment is performed, and the received packet is delivered to the upper layer TCP / UDP layer.

  In addition, when receiving a data transmission request from the upper layer TCP / UDP layer, the destination terminal is registered in the preference list based on the “Flow-ID” stored in the terminal itself. A communication media number having a high priority is extracted, and a packet related to the IP address of the communication media corresponding to the extracted communication media number is generated.

  Through the above processing, for example, the communication flow A (arrow indicated by the solid line) that has been communicated between the default communication media as shown in FIG. It can switch to the flow B (arrow of a wavy line part). With this flow control, it is possible to change communication between communication media 33 and communication media 43 for upstream communication and communication between communication media 34 and communication media 43 for downstream communication. Can be dispersed and reduced.

  In addition, if the above-described processing using different “Flow-ID” fields is performed for each application, an application requiring real-time performance, for example, VoIP (Voice over IP) that requires voice data distribution every 20 ms is required. For example, a high-quality communication medium can be assigned to the application, and, for example, an application that does not require real-time performance, such as mail, can be assigned to a low-speed communication medium.

  In order to perform such processing, for example, information relating the flow ID number stored in the “Flow-ID” field and a predetermined application may be held in the association DB.

  As described above, according to this embodiment, communication media to be used for each communication flow and priorities are grouped, the grouping information is exchanged between both communication terminals, and communication based on the grouping database is performed. Therefore, the communication media suitable for the communication characteristics of the communication flow is selected, and communication traffic can be distributed.

[Embodiment 3]
In this embodiment, the communication media change control in use will be described with reference to FIGS. 2 and 5 to 9.

  After the association is established between the communication terminals, the state of the communication media attached to the own terminal is monitored by the above-described communication media monitoring function. If an abnormality is detected in the communication media attached to the terminal itself, an address list is transmitted to the communication destination terminal by the communication media diagnosis function described above.

  In this case, first, the destination terminal notified of the changed address list updates the address list stored in the association DB 14 in its own terminal, and the partner terminal (source terminal) that has become unusable. Disable communication media information.

  When a packet in which a value other than “0” is set in the “Flow-ID” field of the association header 25 during a predetermined association communication between both terminals, the “Flow-ID” ”Field value is stored in the own terminal.

  Thereafter, when communication from the transmission destination terminal to the transmission source terminal is performed, the preference list is searched based on the stored “Flow-ID”, and the state of the communication media of the transmission source terminal is checked. At this time, the communication media registered in the preference list are checked in the order of NIC-No, a response packet is generated in response to the first usable communication media found, and the generated packet is transmitted.

  As a result of the above processing, a communication medium having a high priority registered in the preference list is not usable due to disconnection of the communication cable or movement of the terminal device outside the wireless LAN coverage area. Even in such a case, it becomes possible to continue communication by switching the communication medium to be used, and high reliability of communication can be realized.

  In addition, it is possible to detect a network failure by monitoring the carrier status of the communication media of the terminal itself and the frequency of occurrence of temporary or continuous packet loss caused by a sudden load increase. Then, the communication media that can be used and the priority order thereof can be notified to the other terminal, and processing that avoids using the communication media in which a failure has occurred can be performed.

[Embodiment 4]
Next, a communication terminal device and a communication method according to Embodiment 4 of the present invention will be described. The communication terminal apparatus according to the present embodiment has a plurality of communication media as means for accessing the Internet network, and the communication terminal apparatus according to the present embodiment has a protocol stack as shown in FIG. Yes. In the communication terminal device of the present invention, as in the above embodiment, an association layer having a function for controlling the start and stop of multipath communication is added to the protocol stack in the TCP / IP protocol stack.

  FIG. 24 is a functional block diagram of the multipath communication function added to the association layer 50. The multipath communication function includes a multipath communication transmitter (hereinafter referred to as a multipath transmitter) 52, a multipath communication receiver (hereinafter referred to as a multipath receiver) 53, an association database (association DB) 54, a communication The quality monitoring unit 51 is composed of four parts.

  The multipath transmission unit 52 refers to the association DB 54 held in the association layer of the own information communication terminal device, and transmits the same user data to a plurality of communication media possessed by the information communication terminal device of the transmission destination have. In addition to this multipath communication function, the multipath transmission unit 52 has an association information addition function for adding an association header to a transmission packet and a communication media selection function for selecting a communication medium for transmitting transmission data. The

  The association information adding function in the multipath transmission unit 52 searches the association DB 54 based on the IP address of the own terminal and the IP address of the partner terminal set in the transmission data from the transport layer, which is an upper layer. When the relevant association information is retrieved, the association header is added to the header portion of the transmission data from the upper layer, and the association protocol number is set in the upper protocol field of the IP header.

  Further, the communication media selection function in the multipath transmission unit 52 determines the IP address of the communication media of the local terminal to be transmitted and the IP address of the communication media of the counterpart terminal to be transmitted based on the data corresponding to the search of the association DB 54. Perform the process. When the transmission source IP address and the transmission destination IP address set in the transmission data from the upper layer are different from the IP address searched in the association DB 54, the transmission destination IP address in the transmission data, Then, the transmission source IP address is changed, and the transmission data generated at this time is transferred to the lower IP layer.

  The multipath receiving unit 53 receives user data received from the communication medium of the own information communication terminal, extracts a sequence number as a communication data identifier included in the received communication data, and holds it in the association layer The association DB 54 is referred to and compared, and if user data having the sequence number is not received, the association DB 54 is passed to the upper protocol. In addition, if the sequence number of the received user data has already been received, the multipath receiving unit 53 has a function of discarding the user data in the association layer. In addition to this multipath reception function, the multipath reception unit 53 receives an association header processing function for receiving a packet reception notification from the lower IP layer and processes the association header, and is set in the received data. An IP address conversion function for performing conversion processing of the existing IP header part is provided.

  The association header processing function in the multipath receiving unit 53 checks the upper protocol field included in the IP header portion of the received packet sent from the IP layer. If the association protocol number is included, it is included in the received packet. The association DB 54 is searched based on the transmission destination IP address and the transmission source IP address. When the relevant association information is retrieved, the association header is processed, deleted from the received packet, and processed into a normal TCP / IP packet format.

  In addition, the IP address conversion function in the multipath receiving unit 53 determines a source IP address and a destination IP address to be passed to the upper layer based on the data hit in the search in the association DB 54. If the source IP address and destination IP address set in the received packet are different from the IP address searched in the association database, the destination IP address and source IP address in the received packet And the received packet is passed to the upper layer TCP / UDP layer.

  The association DB 54 is a database that manages sequence numbers set in the association header of received packets received by the multipath receiving unit 53. The association DB 54 stores information such as association IDs for managing associations, IP address lists related to communication media, and priorities, in association with each other.

  The communication quality monitoring unit 51 monitors the received sequence number holding area stored in the association database 54, detects the occurrence of missing sequence numbers, and detects the difference in arrival times of received packets having the same sequence number (that is, plural (Reception time difference between communication media).

  In the communication terminal device according to the present embodiment, the frame format of the control packet communicated by the association protocol is as shown in FIG. 5, the format of the association header is as shown in FIG. 6, and the address list The format of the header is as shown in FIG. 8, and the format of the preference list header is as shown in FIG.

  First, as shown in FIG. 5, in a control packet communicated by the association protocol, association control data 22 added at the time of processing of the association layer is inserted on the upper side of the IP header 21. The association control data 22 includes three header parts, an association header 25, an address list header 26, and a preference list header 27. The association header 25 is transmitted / received when communication using an association protocol is performed. Always inserted in every packet. On the other hand, the address list header 26 and the preference list header 27 are inserted into the upper layer side of the association header 25 as necessary.

  Also, as shown in FIG. 6, in the association header, the “Next Header” field is composed of 8 bits, and the protocol number of the header to be inserted next to the association header is set. The “Flag” field is composed of 8 bits, and “INIT”, “ACK”, “REL”, “ADDR”, “DATA”, “MP-S”, “MP-E” as shown in FIG. Bits for controlling the association protocol such as are assigned. The “Flow-ID” field is composed of 4 bits, and indicates the number of the flow list to be exchanged in the preference list header. The “Sequence” field is composed of 12 bits, and is incremented by one every time an association packet is transmitted as the sequence number of the association packet. The “Source Host-ID” is composed of 128 bits of 16 bytes, and is determined based on a random number generated in the own terminal as an ID for identifying the own terminal, and is notified to the partner terminal when negotiating the establishment of the association. . The “Destination Host-ID” is composed of 16 bytes of 128 bits, and is determined based on a random number generated by the partner terminal as an ID for identifying the partner terminal upon negotiation of establishment of the partner terminal, and is notified to the terminal itself. .

  FIG. 25 shows the “Flag” field in the association header, and the control of the start and stop of multipath communication is “MP-S” and “MP-E” in the “Flag” field shown in FIG. Control using bits. A communication terminal requesting the start of multipath communication sets the “MP-S” bit to 1, and transmits a control packet for the start request to the partner communication terminal. The communication terminal requesting the stop of multipath communication sets “MP-E” bit to 1 and transmits a stop request control packet to the partner communication terminal.

  As shown in FIG. 8, in the address list header, the “Next Header” field is composed of 8 bits, and the protocol number of the header inserted after the address list header is set. The “Type” field is composed of 4 bits and is set with a number indicating that it is an address list. The “Length” field is composed of 4 bits, and the number of IP addresses related to the communication media possessed by the own terminal set in the “IP Address” field is set. The “IP Address” field is composed of 16 bytes of 128 bits, and an IP address added to the communication medium of the terminal itself is set.

  Also, as shown in FIG. 9, in the preference list header, the “Next Header” field is composed of 8 bits, and the protocol number of the header inserted after the preference list header is set. The “Type” field is composed of 4 bits and is set with a number indicating a preference list. The “Length” field is composed of 4 bits, and the number of flow information is set. Each of the “flow information” fields is composed of 16 bits, the first 4 bits form a “Flow-ID” field, and the remaining 12 bits form an “NIC-NO” field for each 4 bits. In the “Flow-ID” field, the flow ID number set in the “Flow-ID” field in the association header described above is set, and in the “NIC-NO” field, “IP Address” in the above-described address list header is set. The information indicating the order of the IP addresses related to the communication media set in the "" field is set.

  The communication quality monitoring unit 51 establishes an association between both terminals by performing a negotiation based on the association information between the communication terminals, and starts monitoring after the association is established. First, the communication quality monitoring unit 51 searches for a received sequence number stored in the association database 54 by using data reception at the multipath receiving unit 53 as a trigger, and there is no missing sequence number, that is, packet loss occurs. Check if it is not. When the occurrence of packet loss exceeds a threshold that can be arbitrarily set by the terminal user, a multipath communication start request packet is transmitted to the counterpart communication terminal. Alternatively, when the user requests the communication quality management unit to start multipath communication using the input / output device of the own communication terminal, a multipath communication start request packet is transmitted to the counterpart communication terminal.

  Also, when the association is established between both terminals, key information is exchanged between both terminals in order to generate a shared secret key for packet encryption. The public key information uses a Diffie-Hellman algorithm also used in IPSec or the like, generates a random number and a public value to be transmitted to the partner terminal, and adds it to the negotiation packet at the time of association establishment. Both terminals generate a shared secret key from the exchanged key information and use the key to AES-encrypt the “IP Address” field in the address list header shown in FIG. Hide IP address information.

  First, a case where user data is transmitted from the communication terminal A that has transmitted the multipath communication request packet and received by the communication terminal B will be described with reference to FIGS. 26 and 27. FIG.

  First, the multipath transmission unit 12 of the communication terminal A that performs transmission checks whether the multipath communication function is started. When the multipath communication function has been started, the communication terminal A transmits user data from all the communication media A-1 and A-2 of the communication terminal A to the partner communication terminal B.

  To which communication medium of the destination terminal is transmitted, user data is transmitted to the communication medium having the highest priority in the IP address list exchanged in the association address header when the association is established (in this case, B-1). . First, it instructs the communication media A-1 of the communication terminal A that is its own terminal to transmit user data to the communication media B-1 of the communication terminal B that is the counterpart terminal. At this time, the multipath transmission unit 52 sets the sequence number in the sequence number field in the association header, stores the sequence number in the association DB 54, and creates a copy of the user data.

  Next, the multipath transmission unit 52 directs the copied user data to the communication medium A-2 of the own communication terminal A and the user data to the communication medium B-1 of the communication terminal B which is the counterpart terminal. Instructs to send user data. At this time, the sequence number stored at the time of transmission from the communication medium A-1 is set in the sequence number field of the association header.

  When the transmission from the communication media A-1 and A-2 is completed, the multipath transmission unit 12 increments the sequence number by 1 as a sequence number to be added next when user data is transmitted.

  The communication terminal B receives the user data sent from the partner communication media A-1 and A-2 by the communication media B-1 that the communication terminal B has. The receiving communication terminal B extracts the sequence number in the association header of the received user data packet and searches the received sequence number holding area stored in the association database 54.

  If the received sequence number is not found, the received user data is passed to the upper transport layer. When the user data is transferred to the upper transport layer, the received sequence number is stored in the received sequence number holding area stored in the association database 54.

  The communication terminal B extracts the sequence number in the association header from the user data received from the other communication medium, that is, the user data received later in time. The received sequence number holding area in the association database 54 is searched for a received sequence number.

  In the case of user data received second, since the same sequence number is found in the received sequence number holding area, the user data is discarded in the association layer and is not passed to the upper transport layer.

  Since the user data sent from the communication media A-1 and A-2 on the transmission side are the same, the user data that has arrived first regardless of whether the user data is sent from A-1 or A-2. Can be passed to the upper transport layer. As a result, it is possible to receive data from a plurality of network networks, so even if data cannot be received from one network due to movement of the communication terminal itself or a network network problem, data can be received. Realize high-quality communication.

  Next, a case where user data is transmitted to the communication terminal A from the communication terminal B that has received the multipath communication monitoring request will be described with reference to FIGS.

  The communication terminal B that transmits the user data checks whether the multipath communication start request packet has been received. When the multipath communication start request packet has been received, the communication terminal B transmits user data to the communication media registered in the address list stored in the association database 54.

  First, the communication terminal B transmits user data to a communication medium having a higher priority of the partner communication terminal registered in the address list. In the case of FIG. 28, it is assumed that the communication terminal B transmits user data from the communication medium B-1 to the communication medium A-1 of the partner communication terminal A.

  At this time, the communication terminal B sets the sequence number in the sequence number field in the association header, stores the sequence number in the association database 54, and creates a copy of the user data.

  Next, the communication terminal B transmits the user data, which has been copied, to the communication medium A-2 of the partner communication terminal A using the communication medium B-1 of the own communication terminal. At this time, the sequence number stored at the time of transmission to the communication medium A-1 is set in the sequence number field of the association header.

  When the transmission to the communication media A-1 and A-2 is completed, the communication terminal B increments the sequence number by 1 and stores it in the association database 54 as a sequence number to be added the next time user data is transmitted. .

  The receiving communication terminal A extracts the sequence number in the association header of the received user data packet, and searches the received sequence number holding area stored in the association database 54. If the received sequence number is not found, the received user data is passed to the upper transport layer. Further, when the user data is passed to the upper transport layer, the received sequence number is stored in the received sequence number holding area stored in the association database.

  The sequence number in the association header is extracted also from the user data received from the other communication medium, that is, received later in time. Then, the received sequence number holding area in the association database 54 is searched to search for the received sequence number. In the case of user data received second, since the same sequence number is found in the received sequence number holding area, the user data is discarded in the association layer and is not passed to the upper transport layer.

  Since the user data received by the communication media A-1 and A-2 of the own communication terminal is the same, the user who has arrived first is independent of whether the communication media A-1 or A-2 is received. Data can be passed to the upper transport layer.

  As a result, it is possible to receive data from a plurality of network networks, so even if data cannot be received from one network due to movement of the communication terminal itself or a network network problem, data can be received. Realize high-quality communication.

  Next, a case where the multipath communication function is stopped will be described. The communication quality monitoring unit of the communication terminal on the side that has transmitted the start request for the multipath communication function receives user data from different communication media.

  At this time, using the packet reception as a trigger, the received sequence number holding area in the association database is searched. There is no omission of the sequence number stored in the received sequence number holding area, and it is below the allowable range (threshold value) of packet loss set by the communication terminal user, or the communication terminal user is an input / output device of the communication terminal When the multipath communication stop request is explicitly issued from the terminal, a multipath communication stop request control packet is transmitted to the partner communication terminal to stop the multipath communication function. At this time, the communication quality monitoring means of each communication medium is used to detect the difference in communication quality of each communication medium, and the communication quality of one communication medium is stable. When it is detected that there is no loss, the communication information used on the receiving side is notified to the sender's information communication terminal device. You may make it restrain the communication data amount exchanged between each communication terminal by stopping the transmission to a medium.

  In addition, the communication quality monitoring unit 51 detects a packet reception time difference between a plurality of media, but there is a large difference in reception time depending on the communication media received using this reception time difference. When there is a difference in quality, a multipath communication stop request control packet may be transmitted to the partner communication terminal to stop the multipath communication function. At this time, the communication media used on the receiving side is notified to the other communication terminal, so that only the communication media with a stable communication state is used, and transmission to other communication media is stopped. The amount of communication data exchanged between terminals may be suppressed.

  In the case of FIGS. 26 and 27, if the occurrence of packet loss exceeds a threshold that can be arbitrarily set by the terminal user, the same user data is transmitted to a plurality of communication media attached to the own communication terminal. The multipath communication function is activated and a multipath communication start request packet is transmitted to the partner communication terminal. The communication quality monitoring unit 51 constantly monitors the communication state between the own communication terminal and the partner communication terminal. When the communication state becomes unstable due to the movement of the communication terminal, for example, the radio wave intensity of the wireless LAN has decreased, packet loss has occurred frequently and retransmission of user data has become noticeable, response data for transmission data is slow, etc. If the communication status becomes unstable or the communication quality deteriorates more than a certain level, With starting the multi-path communication function of transmitting the same user data, it may be transmitted multipath communication start request packet to the partner communication terminal.

  In addition, by enabling the transmission and reception of multipath communication function start / stop commands to multiple communication media of the partner communication terminal, the partner communication terminal can arbitrarily start and stop the multipath communication function. It is possible to control the communication media and arbitrarily switch the communication media of the partner communication terminal as the transmission source when the communication state deteriorates due to movement or failure of the partner information terminal.

  As described above, according to the present embodiment, since a function for transmitting and receiving the same user data using a plurality of communication media is implemented, a network that can be used by moving a place where the communication terminal uses is provided. Even if the communication quality of one communication medium deteriorates and the user data cannot be received even when the user data cannot be received, the user data can be received by the other communication medium, so the communication is interrupted for the user application. No seamless communication, can provide high communication quality. In addition, it is possible to provide high mobility without making the user aware of changes in the network state, switching of network access means, termination of applications, and restarting due to communication switching.

  In addition, it manages the sequence number of user data received from multiple communication media, discards already received user data inside the association layer, and does not pass it to the higher-level application. Can be used as they are. In addition, unnecessary user data that has already been received is discarded in the association layer, so there is no need to perform extra processing, and the load on resources such as CPU and memory can be reduced.

  In addition, a function that continuously monitors the communication quality status, automatically determines deterioration and recovery of the communication status, and automatically starts and stops multipath communication is implemented. High mobility can be provided without being aware of state changes.

  In addition, the user can arbitrarily control the start and stop of multipath communication via the input / output device of the communication terminal, move to a place where the probability of occurrence of packet loss of user data is high, or no packet loss is recognized. It is possible to provide high communication quality when using a user application.

  In addition, by implementing a function that automatically and manually controls the start and stop of multipath communication, multipath communication is started in places where communication quality is poor, and user data is transmitted using multiple communication media. By increasing the communication rate, if the communication quality is secured and the communication state is moved to a place with a good communication state, the multipath communication is stopped and the communication flow, that is, the amount of data to be transmitted is reduced, thereby reducing the communication load on the network Is possible.

  In addition, by controlling the start and stop of multipath communication for multiple communication media of the communication terminal of the transmission source, communication is performed with the communication flow of the number of combinations of communication media of the transmission source and the transmission destination. Network access means using various communication media.

  Next, the communication system and the communication method according to the fifth to seventh embodiments of the present invention will be described. Before detailed description, some features of the communication system according to the fifth to seventh embodiments will be described. To do.

  A communication system and a communication method according to the present embodiment are used in a multi-home communication terminal having a plurality of communication media such as Ethernet (registered trademark), wireless LAN, and PHS in an Internet network including a plurality of networks. A means for switching communication media to be used in accordance with a change in the situation is provided, and a handover processing load due to switching of the communication media is reduced.

  In addition, the communication system and communication method according to the present embodiment can be used in a communication environment (for example, mobile communication) in which the IP address system to be used changes across networks, that is, between domains, due to movement or the like. By installing the MAP for managing the mobile terminal outside the domain, the mobile terminal can manage the address of the mobile terminal and relay the communication even when the MAP moves between domains. And providing continuous seamless communication with the partner communication terminal.

  Further, in the communication system and the communication method according to the present embodiment, the MAP manages the communication media used by the mobile terminal, the communication media switching of the mobile terminal, that is, the signaling operation at the time of handover is performed by the MAP, By eliminating the signaling with the partner communication terminal, the handover processing time is reduced and the communication efficiency is improved.

  In addition, the communication system and the communication method according to the present embodiment include means for periodically notifying the communication terminal that the MAP is communicating with the communication load state via the MAP, and the communication load state of the MAP. The communication terminal that received the notification of MAP determines the communication load state of the MAP, and when the set threshold is exceeded, there is provided means for switching between using communication via the MAP or directly communicating between the communication terminals It is characterized by.

[Embodiment 5]
FIG. 31A is an example of a communication model according to the fifth embodiment of the present invention, and a flow of data (hereinafter referred to as “handover signal”) necessary for handover processing and data in the communication model (when not passing through MAP) 31-2 is a diagram illustrating a flow of data and a handover signal (in the case of passing through the MAP) in the communication model illustrated in FIG. 31-1. The communication model shown in FIGS. 31-1 and 31-2 includes a mobile terminal MH (Mobile Host) that moves between domains, a GW (Gate Way) that relays inter-domain communication, and an IX (Internet) that controls Internet communication. Exchange), CH (Corresponding Host) which is a communication terminal of a communication partner, and a MAP having management functions such as management of communication media and handover control between communication terminals.

  Normally, when the mobile communication node MH does not move between domains, as shown in FIG. 31-1, the MH and CH directly perform data communication between both terminals, and the GW to be used does not change. Communication is performed at.

  On the other hand, the mobile communication node MH moves out of the radio wave reception area of the wireless LAN system being used, for example, and then enters the radio wave area of the movable wireless LAN or has a low-speed but wide communication area. Consider the situation of moving to an established cellular network area.

  At this time, in each of the above-mentioned Patent Documents 1 and 2 and Non-Patent Documents 2 to 4, a communication media switching function by the association layer is provided, and a continuous communication between MH and CH is achieved by a technique for concealing the communication media to be used. And seamless communication is realized.

  However, depending on factors such as the physical distance between communication terminals and communication load, it depends on the communication delay between the MH and the CH, and the handover processing time due to the movement of the MH between domains varies, resulting in packet loss and packet retransmission. The communication efficiency is reduced due to the occurrence of.

  For this reason, in the present invention, a MAP that manages communication media used by the MH is installed outside the domain to be used, and handover of communication beyond the domain accompanying movement is controlled.

  FIG. 32 is a diagram showing a handover sequence in the fifth embodiment of the present invention, and shows each sequence between MH, MAP and CH when handover is performed.

  Usually, between MH and CH, the IP address of the communication media used by each other is designated, and “Data Packet” communication is performed directly.

  When the MH, which is a mobile terminal, detects a deterioration in the communication state and communication load of the communication medium to be used, the MH transmits a “Registration Request” packet to the MAP that manages the communication medium of the MH, and transmits to the MAP. Notify that the communication media will be changed.

  The MAP that has received the “Registration Request” packet uses the reception of the “Start Request” packet from the MH as a trigger, and the communication packet transmission destination that has been in direct communication with the MH and the CH from the partner communication terminal MH to the own MAP. A control packet for notifying transmission is transmitted to the CH. The MAP that has received the “Start Request” packet from the MH that is the mobile terminal transmits an “Start Request” packet to the CH, and instructs the MAP to transmit “Data Packet”.

  The MAP that has transmitted the “Registration Request” packet to the CH changes the transmission of user data directly to the MH to the CH, triggered by the “Start Request” from the MH, and a control packet that instructs the MAP to send the data. Send. The CH that has received the “Start Request” packet changes the packet that has been directly transmitted to the MH to the IP address of the MAP and transmits it.

  The CH that has received the “Start Request” control packet changes the packet directly transmitted to the MH to the MAP supported by the “Request Registration” control packet, and transmits the MAP IP address. When switching the communication media used by the mobile terminal MH, the MAP transmits “Update Request” to the MAP, and the MAP that has received this “Update Request” changes the IP address of the MH and then transmits to the new IP address. .

  The control packet from the MAP becomes valid in the CH, and the MAP that receives the user data from the CH to the MH is the user sent from the CH based on the management information of the MH communication media updated in the above processing. It is determined to which communication media (media A and B (see FIG. 32)) the MH should transmit data, and user data is transmitted to the MH.

  The MH that receives the user data normally receives and sorts the received user data by using the communication media switching function, the multipath communication function, and the like described in Patent Documents 2 to 4, and is normal between the applications in the own MH. Exchange data.

  When the communication state of the communication media to be used and the communication load are detected to be restored, the MH that is a mobile terminal stops communication between the MH and the CH via the MAP and directly between the MH and the CH. A communication request “Stop Request” for starting a simple communication is requested to the MAP.

  The MAP that has received “Stop Request” notifies the CH of the request and notifies the MH of the change of the destination IP address.

  The MH of the transmission source validates the “Stop Request” packet according to the set condition, and transmits an “Unregistration Request” packet for starting direct communication between the MH and the CH to the MAP.

  The CH that has received the “Unregistration Request” changes the destination of user data from the IP address of the MAP node to the IP address of the MH according to the MH information included in the “Stop Request”, and directly transmits from the CH to the MH.

(simulation result)
Next, simulation results performed based on the above functions will be described.

  FIG. 33 is a diagram illustrating an example of a simulation model according to the fifth embodiment. FIG. 33 shows the arrangement of nodes configured as a simulation model, communication media used for communication, and set values of communication bandwidths that can be communicated.

  Next, specific setting values in the simulation model will be described.

  The MH is equipped with two communication media, for example, a cellular network and a wireless LAN. The former has a communication speed of 384 kbps and a delay of 10 ms for packet transmission, and the latter has a communication speed of 11 Mbps and a delay of 1 ms for packet transmission. Set as stuff. When the MH moves between domains, it communicates with the CH via a GW (Gate Way) installed in each domain.

  Between each GW and IX via Internet communication, a communication speed of 10 Mbps and a communication packet delay of 5 ms are set on both the cellular network side and the wireless LAN side.

  The communication speed and delay time are set to 10 Mbps and 5 ms, respectively, between MAP and IX that control communication between MH and CH domains.

  The communication speed and delay time between IX and the communication partner CH are 10 Ms and 50 ms, respectively.

  FIG. 35 shows a case where the communication beyond the domain is directly performed between the MH and the CH, and when the handover is performed, that is, when the handover is performed between the MH and the CH and the handover process is performed via the MAP. It is a graph which shows each simulation result at the time of performing.

  In the case where the direct handover process is performed between the MH and the CH, the throughput is 1.81 Mbps (see the column “Original” in FIG. 35), whereas in the communication method of the present invention via the MAP, 4.97 Mbps (see “Through MAP” column in FIG. 35) and 2.5 times or more communication performance were obtained.

  This simulation result shows that the control packet is directly transmitted and received between the MH and the CH by taking the “Start Registration” sequence and the “Update Request” sequence for the counterpart communication terminal in the handover process. This indicates that packet loss that occurs during the handover process is reduced, and as a result, communication efficiency can be improved.

[Embodiment 6]
In the sixth embodiment, in communication in each communication section with MH and MAP that are mobile terminals and CH that is a communication terminal, communication between MH and CH via MAP when a communication load is generated in the MAP node. The MH-CH communication (direct communication) without passing through the MAP will be described.

  FIG. 34 is a diagram illustrating an example of a simulation model according to the sixth embodiment. In the same figure, each node of SRC and DST generates “Background Flow” in this simulation system and gives a communication load to the MAP node.

  Each node of SRC and DST is configured to perform one-to-one communication between SRC and DST via the MAP node and does not affect other nodes in the system.

  The communication speed and packet delay between SRC and IX are set to 100 Mbps and 10 ms, respectively, and the communication speed and packet delay between DST and IX are set to 100 Mbps and 50 ms, respectively.

  FIG. 36 is a chart showing a simulation result performed under the same conditions as FIG. 35 except that communication traffic exists in the background.

  Even when communication traffic is generated in the background and communication load is given to MAP, IX, etc., by performing handover processing by MH-CH communication via MAP, communication between MH-CH without MAP is performed. Compared with the conventional system to perform, the packet loss generated at the time of the handover process is reduced, and as a result, the communication efficiency can be improved.

[Embodiment 7]
In the seventh embodiment, in addition to the configuration and functions of the sixth embodiment, the MAP node has means for periodically notifying the MH and CH of the communication load state of the own MAP node. Is.

  The MH and CH that have received the communication load state from the MAP node determine whether to select MH-CH communication via MAP or MH-CH communication not via MAP depending on the communication load state of the MAP. To do.

  By adding this function, the communication path used by the MH or CH is autonomously switched according to the communication load state of the MAP, and an efficient communication path can be selected.

  The lowermost term (Adaptive handover) in FIG. 36 periodically (periodically) transmits the communication load state of its own MAP to MH and CH under the same system configuration and communication conditions as in the sixth embodiment. In this case, the MH-CH communication via the MAP and the MH-CH communication not via the MAP are generated. More specifically, the communication via the MAP and the communication not via the MAP are set to 10 The simulation result when performing alternately every second is shown.

  In the simulation result shown in FIG. 36, the throughput when only communication via MAP is performed is 2.43 Mbps (refer to the “Through MAP” column in FIG. 36), whereas communication via MAP and non-MAP are not transmitted. The throughput (see the column “Adaptive handover” in FIG. 36) in the case of alternately performing communication in the above was 3.63 Mbps. Thus, by periodically (periodically) transmitting the communication load state of the MAP to the terminals that are performing communication, it is possible to improve the throughput between the terminals that are performing communication.

  As described above, the present invention is useful for communication between terminal apparatuses having a plurality of communication media, and is particularly suitable for mobile communication in which the network environment changes dynamically.

Claims (26)

In a communication device applied to a communication terminal device having a plurality of communication media as access means to a predetermined network,
Communication media monitoring means for periodically monitoring the status of communication media possessed by the terminal;
A communication media diagnosis means for notifying the transmission destination terminal of a monitoring result of the monitored communication media;
An association database holding association information including at least information associating an IP address used for communication with an identifier for identifying the communication medium;
Association transmission means for generating a transmission packet with the association information added thereto;
An association receiving means for extracting the association information from the received packet and updating the stored information in the association database based on the extracted association information;
A communication apparatus comprising:   2. The communication apparatus according to claim 1, wherein the association database stores information in which an IP address used by the communication medium is associated with an identifier used by a predetermined application.   Each of the communication media monitoring means, the communication media diagnostic means, the association transmission means, the association reception means, and the association database on an association layer that functions between a network layer and a transport layer on the protocol stack. The communication apparatus according to claim 1, wherein the function is embodied.   The communication apparatus according to claim 1, wherein the association database stores information indicating a priority order of the communication media.   The communication media monitoring means constantly or periodically monitors communication traffic transmitted and received by the communication media of the own terminal, and switches and controls the communication media used by the own terminal based on the monitoring information. The communication apparatus according to claim 1.   The communication apparatus according to claim 1, wherein the association database stores grouping information obtained by grouping communication media used for each communication flow and their priorities.   The communication apparatus according to claim 1, wherein a usable communication medium and a priority order regarding the communication medium can be set by a user. In a communication method applied between communication terminal devices having a plurality of communication media as means for accessing a predetermined network,
An association database holding association information including at least information relating an IP address used for communication and an identifier for identifying the communication medium;
A communication media monitoring step for periodically monitoring the status of the communication media possessed by the terminal;
An association transmission step for generating and outputting a transmission packet to be transmitted to the destination terminal based on the association information stored in the association database;
An association receiving step for updating the stored information in the association database based on the association information extracted from the received packet;
A communication method comprising: A communication medium diagnosis step of notifying a transmission destination terminal of a monitoring result obtained by monitoring the state of the communication medium;
9. The association reception step updates storage information in the association database based on a monitoring result of communication media provided in a transmission source terminal notified in the communication media diagnosis step. Communication method. A communication protocol processing method applied to an association layer interposed between a network layer and a transport layer on a protocol stack,
Update the database provided in the own terminal based on the notified communication terminal status information of the partner terminal, status information concerning the communication media of the own terminal and priority information concerning the communication media notified from the partner terminal A communication protocol for determining a communication medium of the terminal and the partner terminal when transmitting a transmission packet based on the communication medium status information of the partner terminal held in a database in the terminal Processing method.   11. The communication protocol processing according to claim 10, wherein the communication status of the counterpart terminal is confirmed by mutually reporting and confirming the response of communication media and priority information that can be used between the terminals. Method.   12. The communication protocol processing method according to claim 10 or 11, wherein information on communication media to be used and information on the priority order thereof are communicated to a partner terminal. In a communication terminal device having a plurality of communication media as access means to the Internet network,
Multipath communication is performed to transmit the same user data to a plurality of communication media possessed by the other communication terminal from one communication medium of the own communication terminal, and the same user data sent from the other communication terminal is transmitted to the own communication terminal. Multipath transmission / reception means for receiving user data received in communication media of the terminal, passing the user data received earlier in time to the upper application, and discarding user data received later in time,
A communication terminal device comprising: The multipath transmission / reception means includes:
Means for exchanging IP address information of communication media held by each other in order to transmit / receive user data using a plurality of communication media;
Means for transmitting user data to communication media possessed by the partner communication terminal by creating association information for identifying the communication partner and adding the association information to the communication packet;
The communication terminal device according to claim 13, comprising:   15. The multipath transmitting / receiving means identifies communication media possessed by a counterpart communication terminal based on the association information, and transmits the same user data to a plurality of communication media possessed by the counterpart communication terminal simultaneously. The communication terminal device according to 1.   The multipath transmission / reception means identifies user data received from a plurality of communication media by a user data identifier added to association information, and determines whether to pass or discard the user data to a higher-level application based on the identification result. The communication terminal device according to claim 14.   The multipath transmission / reception means has communication quality monitoring means for monitoring communication quality, and transmits a multipath communication start request packet for requesting to start the multipath communication based on a monitoring result of the communication quality monitoring means. The communication terminal apparatus according to claim 13, wherein the communication terminal apparatus transmits a multipath communication stop request packet requesting to stop the multipath communication based on the monitoring result.   18. The communication terminal apparatus according to claim 17, further comprising transmission instruction means for instructing transmission of the multipath communication start request packet and the multipath communication stop request packet.   14. The communication terminal apparatus according to claim 13, further comprising means for transmitting a multipath communication start / stop command to a plurality of communication media possessed by the partner communication terminal. In a communication method having a plurality of communication media as means for accessing the Internet network and performing communication using these plurality of communication media,
Multipath communication is performed to transmit the same user data to a plurality of communication media possessed by the other communication terminal from one communication medium of the own communication terminal, and the same user data sent from the other communication terminal is transmitted to the own communication terminal. A communication method characterized by receiving user data received in a communication medium possessed by a terminal and transferring the user data received earlier in time to an upper application and discarding the user data received later in time. A mobile terminal (MH: Mobile Host) having a communication area using the same IP address system as a domain, moving between the plurality of domains and having a plurality of usable communication media, and at least the movement In a communication system comprising a communication server used by a terminal and a management server (MAP: Mobile Anchor Point) having a function of managing the IP address of the mobile terminal,
The communication system according to claim 1, wherein the management server is installed outside the domain area. The mobile terminal
A means for detecting the deterioration of the communication status and communication load of the communication media used by itself;
Means for switching communication media to be used in accordance with changes in communication status;
With
When the mobile terminal detects a deterioration in the communication state or communication load of the communication medium to be used, the mobile terminal notifies the management server of the detection status,
The management server directs the communication performed between the mobile terminal and the communication partner mobile terminal to the self management server for each of the mobile terminal and the communication partner mobile terminal with which the mobile terminal is communicating. The communication system according to claim 21, wherein notification is made to change. The management server
Means for detecting a communication load state of communication via the self-management server;
Means for periodically notifying the detected communication load state to the mobile terminal performing communication;
With
The mobile terminal performs communication via the management server (communication via MAP) or communication not via the management server (communication without MAP) based on the communication load state notified from the management server. 23. The communication system according to claim 21 or 22, further comprising means for selecting the above. A mobile terminal (MH: Mobile Host) having a communication area using the same IP address system as a domain, moving between the plurality of domains and having a plurality of usable communication media, and at least the movement A communication method applied to a communication system including a communication medium used by a terminal and a management server (MAP: Mobile Anchor Point) having a function of managing an IP address of the mobile terminal,
A communication method characterized in that signaling control related to handover of switching of communication media used by the mobile terminal is led from the management server side installed outside that does not include each domain area. When the mobile terminal detects a deterioration in communication state or communication load of a communication medium to be used, the mobile terminal transmits a control packet indicating the detection state to the management server,
The management server sends a communication packet sent between the mobile terminal and the communication partner mobile terminal to the self-management server for the communication partner mobile terminal with which the mobile terminal and the mobile terminal are communicating. The communication method according to claim 24, wherein a control packet to be changed is transmitted. The management server detects a communication load state of communication via the self-management server, and periodically notifies the detected communication load state to a mobile terminal performing communication,
The mobile terminal performs communication via the management server (communication via MAP) or communication not via the management server (communication without MAP) based on the communication load state notified from the management server. 26. The communication method according to claim 24 or 25, wherein the method is selected.

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