JP4231065B2 - Seamless access communication system - Google Patents

Description

  The present invention relates to a communication terminal apparatus including a plurality of interfaces individually connected to a plurality of networks, and particularly, seamless access communication capable of realizing seamless access between such communication terminal apparatus and a server apparatus on the network. About the system.

For example, as described in Patent Document 1, use of mobile IP is sought in a so-called seamless success communication system. If this mobile IP is used, for example, a portable personal computer can be switched between mobile phone communication and wireless LAN communication seamlessly while connected to the Internet. Within the communication range of the access point, data can be downloaded at high speed based on wireless LAN communication. On the other hand, even if the communication range of the access point is out of the range, the data download can be continued based on the mobile phone communication. Processing such as connection interruption and reconnection can be avoided.
JP 2006-121468 A JP 2005-267499 A Japanese Patent Laid-Open No. 2005-223811

  In the mobile IP, one IP address is assigned to one communication terminal. For example, when connected to the Internet, one IP address is maintained regardless of the switching of the communication method. Therefore, when communication is switched from any network to another, movement between such networks must be monitored. Moreover, in the mobile IP, the software program must be changed in a network layer lower than the transport layer such as TCP, that is, the IP layer. These changes are hard to handle for ordinary users. As a result, mobile IP is not as popular as expected.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a communication terminal device that can relatively easily and seamlessly switch a plurality of communications. An object of this invention is to provide the remote proxy server apparatus which can implement | achieve such a communication terminal device.

  In order to achieve the above object, according to the first invention, the first interface connected to the first network by the first IP address, and the second network connected by the second IP address, based on the first and second IP addresses. A second interface connecting the second network to the first network, a third interface connected to the third network by a third IP address, and connecting the third network to the first network based on the first and third IP addresses; There is provided a communication terminal device comprising: a control unit that switches communication between the first and second networks to communication between the first and third networks based on switching from the 2IP address to the third IP address. .

  In such a communication terminal device, a so-called local proxy is established. The local proxy is connected to application software such as a browser through a first interface. Therefore, even if the communication between the first and second networks is switched to the communication between the first and third networks, no change is made between the application software and the first interface. The application software does not need to recognize communication switching. In this way, communication is switched seamlessly. Moreover, an IP address may be allocated to the second interface and the third interface as usual based on so-called IP. Therefore, no changes are made to the IP layer. A user of a communication terminal device can incorporate a local proxy into the communication terminal device relatively easily.

  In such a communication terminal device, the control unit generates a packet requesting the issuance of an identification tag for specifying the connection in establishing the connection between the first and second networks, and the connection between the first and third networks. You may provide the packet generation part which produces | generates the packet containing the said identification tag in the case of establishment. With such an identification tag, the connection between the first and third networks can be easily associated with the connection between the first and second networks. As a result, communication between the first and second networks can be switched to communication between the first and third networks without error.

  A specific control method may be provided in realizing such a communication terminal device. This control method includes, for example, a procedure for establishing a connection with the first network based on a first interface connected to the first network with a first IP address, and a second connection with the second network using a second IP address. A procedure for connecting the second network to the first network based on the interface; a procedure for connecting the third network to the first network based on the third interface connected to the third network by a third IP address; And a procedure for switching communication established based on the second IP address to communication established based on the first and third IP addresses.

  In addition, a specific communication control software program may be provided for realizing such a control method. The communication control software program includes, for example, a procedure for connecting the second network to the first network based on the first IP address unique to the first network and the second IP address unique to the second network, and the first and first A procedure for transmitting a packet requesting issuance of an identification tag for specifying a connection between two networks to the second network, a procedure for receiving a packet including the identification tag from the second network, a first IP address, and a first A procedure for connecting the third network to the first network based on a third IP address unique to the three networks and a packet specifying the connection between the first and third networks while being associated with the received identification tag is directed to the second network Then, the processor may execute the transmission procedure.

  According to the second invention, a first communication unit that establishes a connection based on a first IP address assigned to a predetermined communication terminal device, and a second communication unit that establishes a connection based on a second IP address assigned to the communication terminal device. And a control unit that switches communication based on the first IP address to communication based on the second IP address when a packet notifying the request for switching the communication is received from the second IP address, a remote proxy server device is provided. The

  Such a remote proxy server device is used in combination with the communication terminal device described above. That is, the remote proxy server device is connected to a specific interface (first interface) on the communication terminal device side with the first IP address. At the same time, the remote proxy server device is connected to a specific interface (second interface) on the communication terminal device side with the second IP address. If the first IP address is described in the packet for the communication terminal device, the packet is delivered to the communication terminal via the first interface. Similarly, if the second IP address is described in the packet for the communication terminal device, the packet is delivered to the communication terminal via the second interface. The interface may be assigned an IP address as usual based on the IP. Therefore, no changes are made to the IP layer. A user of a communication terminal device can incorporate a local proxy into the communication terminal device relatively easily.

  Such a remote proxy server device may further include a storage unit that stores an identification tag for specifying the connection in establishing the connection. With such an identification tag, a connection based on the first IP address can be easily associated with a connection based on the second IP address. As a result, communication based on the first IP address can be switched to communication based on the second IP address without error.

  A specific control method may be provided in realizing such a remote proxy server device. This control method notifies a procedure for establishing a connection based on a first IP address assigned to a predetermined communication terminal device, a procedure for establishing a connection based on a second IP address assigned to the communication terminal device, and a request for switching communication. And a procedure for switching communication based on the first IP address to communication based on the second IP address when a packet to be received is received from the second IP address. In the control method, a procedure for receiving an identification tag request signal transmitted from a communication device having a first IP address, and an identification tag for identifying a connection with the communication device having a first IP address in association with the first IP address are registered in the storage unit. And a procedure for extracting an identification tag from a packet transmitted from the communication device having the second IP address, and a procedure for registering the second IP address in the storage unit in association with the extracted identification tag.

  As described above, according to the present invention, it is possible to provide a communication terminal device capable of switching a plurality of communications with each other relatively easily and seamlessly. At the same time, a remote proxy server device capable of realizing such a communication terminal device is provided.

  Hereinafter, an embodiment of the present invention will be described with reference to the accompanying drawings.

  As shown in FIG. 1, the seamless access communication system 11 includes a communication terminal device 12. A mobile phone interface 13, a wireless LAN interface 14, and a wired LAN interface 15 are mounted on the communication terminal device 12. The cellular phone interface 13, the wireless LAN interface 14, and the wired LAN interface 15 are connected to a CPU (Central Processing Unit) 16. The CPU 16 can be connected to the mobile phone communication network 17 through the mobile phone interface 13. In such connection, the mobile phone interface 13 establishes wireless communication with the base station 18. For establishing wireless communication, for example, a communication method such as WCDMA or CDMA2000 is used. Similarly, the CPU 16 can be connected to the wireless LAN network 19 and the wired LAN network 21 through the wireless LAN interface 14 and the wired LAN interface 15. Wireless communication is established between the wireless LAN interface 14 and the access point 22 of the wireless LAN network 19. Wireless communication may be established in accordance with, for example, IEEE 802.11 system standards. Here, a router function is incorporated in the access point 22. The wired LAN interface 15 is connected to a router 24 by a cable 23, for example. For example, Ethernet (registered trademark) may be used for the wired LAN network 21.

  A memory 25 and a storage 26 are connected to the CPU 16. The storage 26 stores so-called application software programs and data. The CPU 16 executes arithmetic processing based on programs and data temporarily stored in the memory 25. Here, Internet-related application software such as a browser and e-mail is cited as application software. In addition, the storage 26 stores a local proxy program for realizing a local proxy described later. For example, a RAM may be used as the memory 25. For example, a hard disk drive (HDD) may be used for the storage 26.

  A gateway 27 is connected to the cellular phone communication network 17. The gateway 27 connects the cellular phone communication network 17 to the Internet 28. Communication is established between the Internet 28 and the communication terminal device 12 by the action of the gateway 27. In establishing such communication, the gateway 27 assigns an IP address to the communication terminal device 12 based on a so-called DHCP function. However, a DHCP server connected to the cellular phone communication network 17 may be used for IP address assignment.

  Similarly, the access point 22 is connected to the Internet 28. The access point 22 connects the wireless LAN network 19 to the Internet 28. Communication is established between the Internet 28 and the communication terminal device 12 by the action of the access point 22. For example, a so-called DHCP server (not shown) is connected to the wireless LAN network 19. In establishing communication, the DHCP server assigns an IP address to the communication terminal device 12.

  The router 24 is similarly connected to the Internet 28. The router 24 connects the wired LAN network 21 to the Internet 28. Communication between the Internet 28 and the communication terminal device 12 is established by the action of the router 24. For example, a DHCP server (not shown) is connected to the wired LAN network 21. In establishing communication, the DHCP server assigns an IP address to the communication terminal device 12.

  A remote proxy server device 29 is connected to the Internet 28. The remote proxy server device 29 includes a plurality of interfaces, for example, first and second interfaces 31 and 32. The first and second interfaces 31 and 32 are individually connected to the router 33. The router 33 connects the first and second interfaces 31 and 32 to the Internet 28. The router 33 sets an IP address for each interface 31 and 32 individually.

  The remote proxy server device 29 includes a CPU 34. The CPU 34 is connected to the first and second interfaces 31 and 32. The CPU 34 is connected to the Internet 28 through the first and second interfaces 31 and 32.

  A memory 35 and a storage 36 are connected to the CPU 34. The storage 36 stores so-called application software programs and data. The CPU 34 executes arithmetic processing based on programs and data temporarily stored in the memory 35. Here, the storage 36 stores a remote proxy program for realizing a remote proxy described later. For example, a RAM may be used as the memory 35. For example, a hard disk drive (HDD) may be used for the storage 36.

  A so-called content server 37 is connected to the Internet 28. An interface 38 is mounted on the content server 37. The interface 38 connects the content server 37 to the Internet 28. In such connection, the interface 38 may function as a so-called router. The content server 37 is uniquely set with an IP address.

  The content server 37 includes a CPU 39. A memory 41 and a storage 42 are connected to the CPU 39. The storage 42 stores so-called application software programs and data. The CPU 39 executes arithmetic processing based on programs and data temporarily stored in the memory 41. Here, for example, content is stored in the storage 42. Such content may be described in HTTP, for example. For example, a RAM may be used as the memory 41. For example, a hard disk drive (HDD) may be used as the storage 42.

  The communication terminal device 12 is equipped with a local proxy. In realizing the local proxy, the CPU 16 executes a local proxy program. In execution, the local proxy program is temporarily stored in the memory 25. The local proxy operates at the TCP layer. Details of the local proxy processing will be described later. The local proxy functions as a control unit according to the present invention.

  Similarly, the remote proxy server device 29 is equipped with a remote proxy. In realizing this remote proxy, the CPU 34 executes a remote proxy program. In execution, the remote proxy program is temporarily stored in the memory 35. The remote proxy 44 operates at the TCP layer. Details of the remote proxy processing will be described later. The remote proxy functions as a control unit according to the present invention.

  Next, the processing of the local proxy will be described in detail. As shown in FIG. 2, when the local proxy process is started, a new connection is first established between the local proxy and the remote proxy in step S1. As a result, any one of the mobile phone interface 13, the wireless LAN interface 14, and the wired LAN interface 15 is connected to the first interface 31. A link is established. Packets travel back and forth on the link. Details will be described later.

  When a new connection is established, a link other than the existing link is newly established in the subsequent step S2. In other words, one interface is newly connected to the first interface 31 from the interfaces 13, 14, 15 that are not involved in the existing link. As a result, the first interface 31 establishes a link with two of the interfaces 13, 14, and 15. Details will be described later.

  In the subsequent step S3, the local proxy considers the priority of the two links. If the priority of the new link is higher than that of the existing link, the local proxy processing operation proceeds to step S4. In step S4, the link is switched. New links replace existing links. That is, the packet goes back and forth on the new link. Packet traffic is canceled on existing links. Details will be described later.

  Thereafter, in step S5, the local proxy monitors existing links that are not involved in packet traffic. In this way, the local proxy continues to secure a backup link. When the disconnection of the backup link is confirmed in step S5, the local proxy processing operation returns to step S2. The local proxy tries again to establish a new link. Thus, the local proxy keeps at least two links as much as possible.

  If the priority of the new link is lower than that of the existing link in step S3, the local proxy processing operation proceeds to step S6. Packet traffic on existing links is maintained. On the other hand, in step S6, the local proxy monitors a new link that is not involved in packet traffic. The local proxy keeps a backup link. When the disconnection of the backup link is confirmed in step S6, the local proxy processing operation returns to step S2. The local proxy tries again to establish a new link. Thus, the local proxy keeps at least two links as much as possible.

  Here, the disconnection of the link may be monitored based on an arbitrary “health check” packet, for example. If the link is maintained, an “ACK” packet is returned in response to the transmission of the “health check” packet. On the other hand, if the link is disconnected, the reply of the “ACK” packet is inhibited. The local proxy cannot receive the “ACK” packet in response to the transmission of the “health check” packet. Therefore, the disconnection of the link can be determined based on whether or not the “ACK” packet is received. Transmission of such “health check” packets may be repeated at regular time intervals. In addition, for example, in the case of a link based on the mobile phone interface 13 or the wireless LAN interface 14, the reception intensity of radio waves may be monitored.

  Next, “new connection” in FIG. 2 will be described in detail. As shown in FIG. 3, at step T1, the local proxy selects an interface. The local proxy considers the priority when selecting an interface. Such priorities may be set in advance in the local proxy program, for example. Here, for example, the priority order may be set in the order of the wired LAN interface 15, the wireless LAN interface 14, and the mobile phone interface 13 based on the packet transfer rate. In addition, priorities may be set based on communication charges. Such priorities may be set based on an input operation of the user of the communication terminal device 12. The priorities may be stored in a nonvolatile storage medium such as the storage 26, for example.

  Subsequently, the local proxy performs a three-way handshake process with the remote proxy based on the selected interface. That is, the local proxy transmits a “SYN” packet toward the first interface 31 of the remote proxy server device 29 in step T2. Prior to transmission, the local proxy generates a “SYN” packet. For example, when the cellular phone interface 13 is selected, the IP address of the cellular phone interface 13 is described in the transmission source in the “SYN” packet. Similarly, when the wireless LAN interface 14 is selected, the IP address of the wireless LAN interface 14 is described in the transmission source. When the wired LAN interface 15 is selected, the IP address of the wired LAN interface 15 is described in the transmission source.

  In subsequent step T3, the local proxy waits for a reply of the “SYN + ACK” packet in accordance with the TCP procedure. When receiving the “SYN + ACK” packet from the selected interface, the local proxy returns an “ACK” packet to the IP address of the first interface 31 in accordance with the TCP procedure in step T4. Thus, the 3-way handshake process is completed according to the TCP procedure. A link is established between the local proxy and the remote proxy.

  In the subsequent step T5, the local proxy transmits an “IP address + identification tag request” packet to the first interface 31 via the selected interface. In this packet, the IP address of the selected interface and an intention indication requesting the issuance of an identification tag are described. The identification tag specifies a link between the selected interface and the first interface 31. This identification tag is issued by a remote proxy, as will be described later.

  In subsequent step T6, the local proxy waits for a reply of the “ACK + identification tag” packet in accordance with the TCP procedure. When the local proxy receives the “ACK + identification tag” packet via the selected interface, the received identification tag is registered in step T7. For example, the identification tag may be temporarily stored in the memory 25. When the processing of “new connection” is completed in this way, downloading of content data is started between the selected interface and the first interface 31. The local proxy starts relaying the content data at step T8. The local proxy stores the content data in the memory 25 in accordance with the TCP procedure, and transfers the content data to the running application software such as a browser.

  If the local proxy cannot receive the “SYN + ACK” packet in step T3, the local proxy confirms that the link is not established. The processing operation of the local proxy proceeds to step T9. In step T9, the local proxy determines whether there is an interface. When the presence of an interface other than the first selected interface is confirmed, the processing operation of the local proxy returns to step T1. The local proxy selects a new interface while giving up on the first selected interface. Thereafter, the local proxy performs the aforementioned processing operation.

  If the local proxy cannot receive the “ACK + identification tag” packet in step T6, the local proxy similarly confirms that the link is not established. The processing operation of the local proxy proceeds to step T9. Thus, the local proxy repeats interface selection until any one of the interfaces 13, 14, 15 is established. When the link failure is completely confirmed in step T9, the local proxy gives up the link establishment. The process ends. The local proxy notifies the application software of the link disconnection.

  Next, “establishing a new link” in FIG. 2 will be described in detail. As shown in FIG. 4, in step V1, the local proxy selects an interface in the same manner as described above. Here, an interface other than the interface involved in the link is selected. For example, if a link is established via the mobile phone interface 13 in “new connection”, either the wireless LAN interface 14 or the wired LAN interface 15 is selected.

  Subsequently, the local proxy performs a 3-way handshake process with the remote proxy 43 based on the selected interface. That is, the local proxy transmits a “SYN” packet toward the first interface 31 of the remote proxy server device 29 via the selected interface in step V2. Prior to transmission, the local proxy generates a “SYN” packet addressed to the IP address of the first interface 31. In subsequent step V3, the local proxy waits for a reply of the “SYN + ACK” packet in accordance with the TCP procedure. When receiving the “SYN + ACK” packet from the selected interface, the local proxy returns an “ACK” packet to the IP address of the first interface 31 in accordance with the TCP procedure in step V4. Thus, the 3-way handshake process is completed according to the TCP procedure. A link is established between the local proxy and the remote proxy.

  In the subsequent step V5, the local proxy transmits an “IP address + identification tag” packet to the first interface 31 via the selected interface. In this packet, the IP address of the selected interface and the aforementioned identification tag are described. The identification tag may be read from the memory 25. The interface thus selected is associated with the existing link described above.

  In subsequent step V6, the local proxy waits for a reply of the “ACK + identification tag” packet in accordance with the TCP procedure. When the local proxy receives the “ACK + identification tag” packet, the “new link establishment” process is completed. At this time, the relay of the content data is maintained with the existing link. Downloading content data is uninterrupted.

  If the local proxy cannot receive the “SYN + ACK” packet in step V3, the local proxy confirms that the link is not established. The processing operation of the local proxy returns to step V1. The local proxy selects a new interface while giving up on the first selected interface. Thereafter, the local proxy performs the above-described processing. Similarly, if the local proxy cannot receive the “ACK + identification tag” packet in step V6, the local proxy confirms that the link is not established. The processing operation of the local proxy returns to step V1. In this way, the local proxy repeats interface selection until any one of the interfaces 13, 14, 15 is newly established.

  Next, “link switching” in FIG. 2 will be described in detail. As shown in FIG. 5, in step W <b> 1, the local proxy transmits a “switch trigger” packet to the first interface 31 of the remote proxy server device 29 via the interface of the new link. Prior to transmission, the local proxy generates a “switch trigger” packet addressed to the IP address of the first interface. In the “switch trigger” packet, an intention to switch the link is described. The IP address of the interface of the new link is described in the transmission source.

  In subsequent step W2, the local proxy confirms the return of the “ACK” packet in accordance with the TCP procedure. At this time, as will be described later, link switching is started in the remote proxy. In the subsequent step W3, the local proxy receives a “switching complete message” packet via the selected interface. The completion of link switching is notified by this “switching completion message” packet. The IP address of the first interface 31 of the remote proxy server device 29 is described in the transmission source of the “switching completion message” packet. The IP address of the selected interface is described in the packet transmission destination.

  In step W4, the local proxy returns an “ACK” packet in accordance with the TCP procedure. When the link switching is completed in this way, downloading of content data is started between the selected interface and the first interface 31. The local proxy resumes the relay of the content data at step W5. The local proxy transfers the content data to the application software while temporarily storing the content data in the memory 25 according to the TCP procedure. Thereafter, the processing operation of the local proxy shifts to step S5 in FIG.

  If the local proxy cannot receive the “ACK” packet in step W2, the local proxy determines a request timeout in subsequent step W6. That is, if reception of the “ACK” packet is not confirmed for a predetermined time, the local proxy stops link switching in step W7. Thereafter, the processing operation of the local proxy shifts to step S5 in FIG. If the request timeout is not confirmed in step W6, the processing operation of the local proxy returns to step W1. The local proxy again sends a “switch trigger” packet.

  In parallel with the processing operation as described above, the occurrence of a failure is monitored in the local proxy. That is, for example, as shown in FIG. 6, the local proxy monitors reception of a “DUP ACK” packet. When a failure occurs in downloading content data, the application software cannot acquire the content data. At this time, the application software transmits a “DUP ACK” packet to the local proxy. In this way, the local proxy is notified of the non-arrival of the content data.

  When the local proxy receives the “DUP ACK” packet in step X1, the local proxy returns an “ACK” packet to the application software. The “ACK” packet only needs to be transmitted at regular intervals. As a result, the occurrence of timeout is avoided in the application software. The application software continues to receive “ACK” packets. However, so-called data is not incorporated in such an “ACK” packet.

  In the following step X3, the local proxy selects a new link. In this case, an arbitrary link other than the failed link is selected. For example, if a failure is confirmed in the link via the wired LAN interface 15, one of the links via the mobile phone interface 13 and the wireless LAN interface 14 is selected. The priorities described above may be taken into account when selecting a link.

  Subsequently, the local proxy transmits a “switch trigger” packet toward the first interface 31 of the remote proxy server device 29 in step X4. Upon transmission, the local proxy generates a “switch trigger” packet. The IP address of the interface related to the selected link is described in the transmission source of the “switch trigger” packet. In subsequent step X5, the local proxy confirms the reply of the “ACK” packet in accordance with the TCP procedure. At this time, link switching is started in the remote proxy.

  In subsequent step X6, the local proxy receives a “switching complete message” packet via the selected interface. In step X7, the local proxy returns an “ACK” packet in accordance with the TCP procedure. In subsequent step X8, the local proxy ends transmission of the “ACK” packet to the application software. As a result, download of content data is started. The local proxy resumes the relay of the content data at step X9. The local proxy transfers the content data to the application software while temporarily storing the content data in the memory 25 according to the TCP procedure. Thereafter, the processing operation of the local proxy returns to step X1. The local proxy continues to monitor for “failure occurrence” again.

  If the local proxy cannot receive the “ACK” packet in step X5, the local proxy determines a request timeout in subsequent step X10. That is, if reception of an “ACK” packet is not confirmed for a predetermined time, the local proxy confirms disconnection of all links. The local proxy stops link switching in step X11. In subsequent step X12, the local proxy ends transmission of the “ACK” packet toward the application software. As a result, downloading of content data is interrupted. If the request timeout is not confirmed in step X10, the local proxy processing operation returns to step X4. The local proxy again sends a “switch trigger” packet.

  Next, remote proxy processing will be described in detail. As shown in FIG. 7, when the remote proxy receives the packet at step Y1, the remote proxy decrypts the packet. That is, when the remote proxy confirms the reception of the “SYN” packet in step Y2, the remote proxy returns a “SYN + ACK” packet to the transmission source of the “SYN” packet in accordance with the TCP procedure in the following step Y3. In replying, the remote proxy generates a “SYN + ACK” packet. The IP address of the transmission source of the “SYN” packet is described in the destination. Thereafter, when the remote proxy receives an “ACK” packet for the “SYN + ACK” packet, the three-way handshake process with the transmission source of the “SYN” packet is completed. A link is established.

  When the remote proxy confirms the reception of the “IP address + identification tag request” packet in step Y5, the remote proxy registers the “IP address” and “identification tag” in the memory 35 or the storage 36 in step Y6. The “IP address” identifies the local proxy interfaces 13, 14, 15. The “identification tag” specifies a link established between the one interface and the first interface 31. Thus, for each link, an “IP address”, ie, one interface 13, 14, 15 is associated. The remote proxy generates an “identification tag” unique to the interface in response to the “identification tag request”. In subsequent step Y7, the remote proxy transmits an “identification tag” together with “ACK” in a packet toward “IP address”.

  When the remote proxy confirms reception of the “IP address + identification tag” packet in step Y8, the remote proxy searches for the registered “identification tag” in step Y9. As a result, the “IP address” of the existing link is extracted. The sent IP address is associated with the “IP address” of the existing link. In subsequent step Y10, the remote proxy registers the sent IP address. At this time, the remote proxy newly assigns an “identification tag” to the IP address to be registered. Here, two “identification tags” are associated with each other during registration. In subsequent step Y11, the remote proxy transmits an “identification tag” to be registered together with “ACK” in a packet toward the IP address to be registered.

  When the remote proxy confirms reception of the “switch trigger” packet in step Y12, the remote proxy returns an “ACK” packet to the transmission source of the “switch trigger” packet in step Y13. The remote proxy extracts the “identification tag” from the “switch trigger” packet. This “identification tag” identifies the link before switching, that is, the existing link. Simultaneously with the transmission of the “ACK” packet, the remote proxy transmits a “zero window” packet to the content server 37 via the second interface 32. The content server 37 interrupts the transmission of the content data in response to the reception of the “zero window” packet. As is well known, the content server 37 stops transmitting content data until it starts to receive the “ACK” packet again.

  In subsequent step Y15, the remote proxy performs link switching. The remote proxy changes the “IP address” of the transfer destination. The IP address of the existing link is changed to the IP address of the transmission source of the “switch trigger” packet. For example, when content data is stored in the buffer, that is, the memory 36, the content data in the buffer is transmitted to the changed transfer destination. When the link switching is completed in this way, the remote proxy transmits a “switching completion message” packet to the transmission source of the “switching trigger” packet.

  When the remote proxy confirms the reception of the “ACK” packet in step Y 17, the remote proxy erases the content data corresponding to the “ACK” packet from the buffer, ie, the memory 35. As a result, the relay of content data is completed. In relaying, the content data is transferred from the second interface 32 to the remote proxy. In the content data, the destination “IP address” is confirmed for each individual packet.

  If the remote proxy cannot confirm receipt of the “ACK” packet in step Y17, the remote proxy holds the content data in the buffer. Thereafter, when the timeout is confirmed in the subsequent step Y19, the processing operation of the remote proxy proceeds to step Y20. The remote proxy sends a “zero window” packet to the content server 37. The content server 37 interrupts the transmission of the content data in response to the reception of the “zero window” packet. Even if the time-out is not confirmed in step Y 19, if the buffer space disappears in step Y 21, the remote proxy transmits a “zero window” packet to the content server 37.

  Now, assume that content data is downloaded from the content server 37 in the seamless access communication system 11. As shown in FIG. 8, “aa” is set as the IP address of the content server 37. Therefore, when an IP address “aa” is set in a packet in the Internet 28, the packet reaches the content server 37.

The local proxy 43 constructs a network with application software such as the Internet browser 45 and the e-mail 46, for example. This network functions as the first network of the present invention. In this network, the interface of the local proxy 43 is specified by, for example, the IP address “127.0.0.1”. That is, the IP address “127.0.0.1” is set in the proxy server of the application software. In the packet generated by the application software, the IP address “127.0.0.1” is designated as the transmission destination. The interface of the local proxy 43 functions as the first interface of the present invention.

  The local proxy 43 is connected to the Internet 28 for each interface 13, 14, 15. In the Internet 28, an IP address “dddd” is assigned to the mobile phone interface 13. Similarly, IP addresses “eef” and “ffff” are allocated to the wireless LAN interface 14 and the wired LAN interface 15, respectively. When an IP address “dddd” is specified in a packet in the Internet 28, the packet reaches the local proxy 43 via the mobile phone interface 13. Similarly, when the IP address “eeee” is designated by a packet in the Internet 28, the packet reaches the local proxy 43 via the wireless LAN interface 14. When an IP address “ffff” is designated by a packet in the Internet 28, the packet reaches the local proxy 43 via the wired LAN interface 15.

  Similarly, the remote proxy 44 is connected to the Internet 28 for each of the interfaces 31 and 32. In the Internet 28, an IP address “c.c.c.c” is assigned to the first interface 31. Similarly, the second interface 32 is assigned an IP address “bbbb”. When an IP address “c.c.c.c” is set in a packet in the Internet 28, the packet reaches the remote proxy 44 via the first interface 31. When an IP address “bbbb” is set in a packet in the Internet 28, the packet reaches the remote proxy 44 via the second interface 32. The IP addresses “c.c.c.c” and “b.bb.b” may be assigned to the first and second interfaces 31 and 32 as fixed values. Any IP address may be arbitrarily set within the range of “0.0.0.0” to “255.255.255.255”.

  The cellular phone interface 13, the wireless LAN interface 14, and the wired LAN interface 15 each establish a connection with the first interface 31. That is, “cc” is described in the destination IP address in the packets sent from the individual interfaces 13, 14, and 15. At this time, in the local proxy 43, the IP address “c.c.c.c” may be set as a unique proxy server. Such proxy server settings may be stored in a non-volatile storage medium such as the storage 26, for example. On the other hand, in the packet sent out from the first interface 31, any one of “dddd”, “eeee”, and “ffff” is set as the destination IP address. Is described. The second interface 32 establishes a connection with the content server 37. That is, in the packet sent out from the second interface 32, “aa” is described in the destination IP address.

  Assume that the mobile phone interface 13 of the communication terminal device 12 is used for downloading content data. First, the local proxy 43 of the communication terminal device 12 performs the above-described “new connection”. As shown in FIG. 9, the local proxy 43 performs a three-way handshake process with the first interface 31 of the remote proxy 44 via the mobile phone interface 13. A link is established. Thus, the cellular phone interface 13 is connected to the Internet 28 by the IP address “dddd”. The browser 45 is connected to the Internet 28 via the mobile phone interface 13 based on the IP addresses “127.0.0.1” and “dddd”.

  Subsequently, the local proxy 43 generates an “IP address + identification tag RQT” packet. An IP address “dddd” is described in the transmission source of this packet. An IP address “c.c.c.c” is described in the packet transmission destination. The packet is transmitted from the mobile phone interface 13.

  The remote proxy 44 receives the “IP address + identification tag RQT” packet via the first interface 31. For example, the remote proxy 44 registers the IP address “dddd” and the identification tag in the storage 36. At the same time, the remote proxy 44 generates an “ACK + identification tag” packet. An IP address “c.c.c.c” is described in the transmission source of this packet. An IP address “dddd” is described in the packet transmission destination. The packet is transmitted from the first interface 31. The local proxy 43 receives the “ACK + identification tag” packet via the mobile phone interface 13. For example, the local proxy 43 registers an “identification tag” in the storage 26.

  Thereafter, the browser 45 accesses the content server 37. For example, packets are exchanged between the browser 45 and the content server 37. Prior to packet exchange, a 3-way handshake process may be performed. Browser 45 generates a “GET” packet. In the “GET” packet, an intention to acquire content data, that is, HTTP data is described. In the transmission destination of this packet, the IP address “127.0.0.1” of the local interface 47 is described. The local proxy 43 forwards the “GET” packet to the remote proxy 44. The IP address “c.c.c.c” is described in the transmission destination of the packet for the transfer. An IP address “dddd” is described in the packet transmission source. The “GET” packet is received by the remote proxy 44 at the first interface 31. The remote proxy 44 transfers the “GET” packet to the content server 37. In this transfer, the IP address “aaaaa” is described in the packet transmission destination. The IP address “bbbb” is described in the packet transmission source. This packet is transmitted from the second interface 32. In this way, the content server 37 receives the “GET” packet.

  The content server 37 generates a “GET reply” packet in response to the reception of the “GET” packet. The “GET reply” packet is sent back to the browser 45. In replying, the IP address “bbbb” is described in the packet transmission destination. An IP address “aaaa” is described in the packet source. The remote proxy 44 receives the “GET reply” packet via the second interface 32. At the same time, the remote proxy 44 forwards a “GET reply” packet to the local proxy 43. An IP address “dddd” is described in the transmission destination of the packet for the transfer. The IP address “c.c.c.c” is described in the packet source. The “GET reply” packet is received by the local proxy 43 at the mobile phone interface 13. The local proxy 43 delivers a “GET reply” packet to the browser 45 via the local interface 47.

  Thereafter, the content server 37 sequentially transmits “HTTP data” packets. In transmission, the IP address “bbbb” is described in the packet transmission destination. An IP address “aaaa” is described in the packet source. The remote proxy 44 receives the “HTTP data” packet via the second interface 32. At the same time, the remote proxy 44 forwards the “HTTP data” packet to the local proxy 43. An IP address “dddd” is described in the transmission destination of the packet for the transfer. The IP address “c.c.c.c” is described in the packet source. On the other hand, the remote proxy 44 temporarily holds the “HTTP data” packet until reception of the “ACK” packet. The “HTTP data” packet is received by the local proxy 43 at the mobile phone interface 13. The local proxy 43 passes the “HTTP data” packet to the browser 45 via the local interface 47. Thus, the browser 45 displays the HTTP data on the screen of a display device (not shown) based on the “HTTP data” packet.

  When the “HTTP data” packet arrives at the browser 45 in this way, the browser 45 generates an “ACK” packet (not shown). The “ACK” packet is delivered to the local proxy 43 via the local interface 47. The local proxy 43 forwards the “ACK” packet to the remote proxy 44. At this time, the IP address “ffff” is described in the packet transmission source. An IP address “c.c.c.c” is described in the packet transmission destination. The packet is sent out from the mobile phone interface 13. The remote proxy 44 receives the “ACK” packet via the first interface 31. Upon receipt, the remote proxy 44 deletes the corresponding “HTTP data” packet from the buffer. At the same time, the “ACK” packet is transferred to the content server 37. The content server 37 confirms the arrival of the “HTTP data” packet in response to the reception of the “ACK” packet.

  For example, assume that the cable 23 is connected to the wired LAN interface 15 during the download of the above-described HTTP data. As shown in FIG. 10, the local proxy 43 of the communication terminal device 12 performs the above-described “establishment of a new link”. The local proxy 43 performs a three-way handshake process with the first interface 31 of the remote proxy 44 via the wired LAN interface 15. A link is established. Thus, the wired LAN interface 15 is connected to the Internet 28 with the IP address “ffff”. The browser 45 is connected to the Internet 28 via the wired LAN interface 15 based on the IP addresses “127.0.0.1” and “f.f.f.f”.

  Subsequently, the local proxy 43 generates an “IP address + identification tag” packet. An IP address “ffff” is described in the transmission source of this packet. An IP address “c.c.c.c” is described in the packet transmission destination. The packet is transmitted from the wired LAN interface 15.

  The remote proxy 44 receives the “IP address + identification tag” packet via the first interface 31. For example, the storage 36 searches for “identification tag” in the packet. Thus, the two IP addresses “dddd” and “ffff” are associated with each other. At the same time, the remote proxy 44 registers the IP address “ffff” and a new identification tag in the storage 36, for example. On the other hand, the remote proxy 44 generates an “ACK + identification tag” packet based on the new identification tag. An IP address “c.c.c.c” is described in the transmission source of this packet. An IP address “ffff” is described in the packet transmission destination. The packet is transmitted from the first interface 31. The local proxy 43 receives the “ACK + identification tag” packet via the wired LAN interface 15. For example, the local proxy 43 registers a new “identification tag” in the storage 26.

  The local proxy 43 confirms the priority order of the wired LAN interface 15. Here, it is assumed that the priority order of the wired LAN interface 15 is higher than that of the cellular phone interface 13. Therefore, the local proxy 43 performs the “link switching” described above. The local proxy 43 generates a “switch trigger” packet. The “switch trigger” packet describes the intention of switching the link, that is, switching the interface. At the same time, an “identification tag” assigned to the link based on the mobile phone interface 13 is described in this packet. An IP address “ffff” is described in the transmission source of this packet. An IP address “c.c.c.c” is described in the packet transmission destination. The packet is transmitted from the wired LAN interface 15.

  The remote proxy 44 receives the “switch trigger” packet via the first interface 31. The remote proxy 44 performs link switching in response to reception of the “switch trigger” packet. At the same time, the remote proxy 44 generates an “ACK” packet. An IP address “c.c.c.c” is described in the transmission source of this packet. An IP address “ffff” is described in the packet transmission destination. The packet is transmitted from the first interface 31. The local proxy 43 receives the “ACK” packet via the wired LAN interface 15. Meanwhile, the remote proxy 44 generates a “zero window” packet. An IP address “bbbb” is described in the transmission source of this packet. An IP address “aa” is described as the packet destination. The packet is transmitted from the second interface 32. The content server 37 receives the “zero window” packet via the Internet 28. In response to the reception of the “zero window” packet, the content server 37 interrupts the transmission of the “HTTP data” packet.

  The remote proxy 44 realizes link switching based on IP address switching. The remote proxy 44 changes the IP address when transferring the “HTTP data” packet. That is, the IP address “ffff” is described in place of the IP address “dddd” so far in the transmission destination of the “HTTP data” packet. Therefore, when the “HTTP data” packet is transmitted from the first interface 31, the “HTTP data” packet is received by the local proxy 43 via the wired LAN interface 15. In such a change, the IP address “dddd” of the mobile phone interface 13 is specified based on the “identification tag”.

  Subsequently, the remote proxy 44 generates a “switching completion message” packet. Completion of link switching is notified. An IP address “c.c.c.c” is described in the transmission source of this packet. An IP address “ffff” is described in the packet transmission destination. The packet is transmitted from the first interface 31. The local proxy 43 receives the “switching completion message” packet via the wired LAN interface 15.

  The local proxy 43 generates an “ACK” packet in response to reception of the “switching completion message” packet. An IP address “c.c.c.c” is described in the transmission source of this packet. An IP address “ffff” is described in the packet transmission destination. The packet is transmitted from the wired LAN interface 15. The remote proxy 44 receives the “ACK” packet via the first interface 31.

  Subsequently, the remote proxy 44 transfers an “ACK” packet to the content server 37. In this transfer, the IP address “aaaaa” is described in the packet transmission destination. The IP address “bbbb” is described in the packet transmission source. This packet is transmitted from the second interface 32. In this way, the content server 37 receives the “ACK” packet. In response to the reception of the “ACK” packet, the content server 37 resumes transmission of the “HTTP data” packet.

  For example, assume that the cable 23 is disconnected from the wired LAN interface 15 during downloading of HTTP data. As shown in FIG. 11, the browser 45 transmits a “DUP ACK” packet to the local proxy 43. Thereafter, the local proxy 43 performs the above-mentioned “occurrence of failure”. That is, the local proxy 43 returns an “ACK” packet to the browser 45 in response to the reception of the “DUP ACK” packet. At this time, data is not incorporated into the “ACK” packet. In response to the reception of such an “ACK” packet, the browser 45 avoids the occurrence of a request timeout. The processing operation of the browser 45 is maintained.

  At the same time, the remote proxy 44 inhibits the reception of the “ACK” packet for the already transmitted “HTTP data” packet. The “HTTP data” packet is accumulated in the buffer. When the buffer overflows, the remote proxy 44 generates a “zero window” packet. An IP address “bbbb” is described in the transmission source of this packet. An IP address “aa” is described as the packet destination. The packet is transmitted from the second interface 32. The content server 37 receives the “zero window” packet via the Internet 28. In response to the reception of the “zero window” packet, the content server 37 interrupts the transmission of the “HTTP data” packet.

  When the “ACK” packet is transmitted, the local proxy 43 generates a “switch trigger” packet. In this packet, an “identification tag” assigned to a link based on the wired LAN interface 15 is described. An IP address “dddd” is described in the transmission source of this packet. An IP address “c.c.c.c” is described in the packet transmission destination. The packet is transmitted from the mobile phone interface 13.

  The remote proxy 44 receives the “switch trigger” packet via the first interface 31. In response to the reception of the “switch trigger” packet, the remote proxy 44 performs link switching as described above. At the same time, the remote proxy 44 generates an “ACK” packet. An IP address “c.c.c.c” is described in the transmission source of this packet. An IP address “dddd” is described in the packet transmission destination. The packet is transmitted from the first interface 31. The local proxy 43 receives the “ACK” packet via the mobile phone interface 13. Simultaneously with the transmission of the “ACK” packet, the remote proxy 44 implements link switching as described above.

  Subsequently, the remote proxy 44 generates a “switching completion message” packet. Completion of link switching is notified. The packet is transmitted from the first interface 31. The local proxy 43 receives the “switching completion message” packet via the mobile phone interface 13. The local proxy 43 generates an “ACK” packet in response to reception of the “switching completion message” packet. The packet is transmitted from the mobile phone interface 13. The remote proxy 44 receives the “ACK” packet via the first interface 31.

  When the link is switched, the remote proxy 44 changes the IP address of the transmission destination with the “HTTP data” packet in the buffer. Thus, the “HTTP data” packet in the buffer is sent out from the remote proxy 44. The IP address “c.c.c.c” is described in the packet source. An IP address “ffff” is described in the packet transmission destination. The local proxy 43 receives the “HTTP data” packet via the mobile phone interface 13. Subsequently, the local proxy 43 delivers the “HTTP data” packet to the browser 45 via the local interface 47. Thus, the browser 45 displays the HTTP data on the screen of a display device (not shown) based on the “HTTP data” packet.

  When the “HTTP data” packet arrives at the browser 45 in this way, the browser 45 generates an “ACK” packet (not shown). The “ACK” packet is delivered to the local proxy 43 via the local interface 47. The local proxy 43 forwards the “ACK” packet to the remote proxy 44. At this time, the IP address “ffff” is described in the packet transmission source. An IP address “c.c.c.c” is described in the packet transmission destination. The packet is sent out from the mobile phone interface 13. The remote proxy 44 receives the “ACK” packet via the first interface 31. Upon receipt, the remote proxy 44 deletes the corresponding “HTTP data” packet from the buffer. At the same time, the “ACK” packet is transferred to the content server 37. In response to the reception of the “ACK” packet, the content server 37 resumes transmission of the “HTTP data” packet.

  Thus, when the link via the cellular phone interface 13 is switched to the link via the wired LAN interface 15, or conversely, when the link via the wired LAN interface 15 is switched to a link via the cellular phone interface 13, the local proxy 43 and the remote Processing is completed between the proxies 44. No changes are made to the connection between the browser 45 and the local interface 47. Similarly, no changes are made to the connection between the remote proxy 44 and the content server 37. The browser 45 and the content server 37 do not recognize link switching. That is, it is not necessary to change the software program in the browser 45 or the content server 37. Links can be switched seamlessly. In addition, in realizing the local proxy 43, software may be installed in the communication terminal apparatus 12 in a layer higher than the TPC layer. No changes are made to the IP layer. The user of the communication terminal device 12 can incorporate the local proxy 43 into the communication terminal device 12 relatively easily.

  The communication terminal device 12 may include a so-called notebook personal computer, a PDA (personal digital assistant), a mobile phone terminal, a wireless LAN terminal, and other electronic devices.

1 is a block diagram schematically showing a hardware configuration of a seamless access communication system according to an embodiment of the present invention. It is a block diagram which shows schematically the software structure of a seamless access communication system. It is a flowchart which shows the process sequence of a local proxy roughly. It is a flowchart which shows the process sequence of "new connection" roughly. It is a flowchart which shows roughly the process sequence of "establishment of a new link." 10 is a flowchart schematically showing a processing procedure of “link switching”. 10 is a flowchart schematically showing a processing procedure of “occurrence of failure”. It is a flowchart which shows the process sequence of a remote proxy roughly. FIG. 10 is a sequence diagram showing packet exchange in a seamless access communication system when a link is established between a communication terminal and a content server via a mobile phone network. FIG. 11 is a sequence diagram illustrating packet exchange in the seamless access communication system when a link is newly established between a communication terminal and a content server via a wired LAN network. FIG. 10 is a sequence diagram illustrating packet exchange in the seamless access communication system when a link is switched from a wired LAN network to a mobile phone network based on a failure of the link via the wired LAN network.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 12 Communication terminal device, 13 Mobile phone interface which functions as 2nd and 3rd network, 14 Wireless LAN interface which functions as 2nd and 3rd network, 15 Wired LAN interface which functions as 2nd and 3rd network, 16 Control part And CPU (central processing unit) that functions as a packet generation unit, 28 second network and third network (Internet), 29 remote proxy server device, 34 CPU that functions as first communication unit and second communication unit, and control unit 36, storage functioning as a storage unit, 43 local proxy functioning as a control unit, 44 remote proxy functioning as a control unit, 47 local interface functioning as a first interface.

Claims (1)

A communication terminal device, and a remote proxy server device connected to the communication terminal device via an IP network, the communication terminal device having a first interface connected to the first network with a first IP address and a second IP address A second interface connected to the second network and connected to the first network based on the first and second IP addresses; a third interface connected to the third network based on the first IP address; and a second interface connected to the third network based on the first and third IP addresses. A first interface that connects the third network to the first network, and a first packet that requests the issuance of an identification tag that identifies the connection in establishing the connection between the first and second networks; Identification in connection with connection between 3 networks A packet generation unit that generates a second packet including a first communication unit, wherein the remote proxy server device is connected to the second interface via the second network based on the second IP address; A second communication unit connected to the third interface via the third network based on a third IP address; an interface connected to the IP network and establishing a connection based on a fourth IP address assigned to the content server; A controller that issues the identification tag in response to reception of the first packet and associates a connection between the first and third networks to a connection between the first and second networks in response to reception of the second packet ; A seamless access communication system comprising:

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