JP2008166874A - Handoff method for terminal connected through napt router, transfer agent, terminal and program - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a handoff method for a terminal preventing, even when the terminal is connected to a network through a NAPT router by the movement of the terminal, the NAPT router from discarding a packet addressed to the terminal, and to provide a transfer agent, a terminal and a program. <P>SOLUTION: When the terminal is connected to a third network when moved and a new address after the movement is imparted to the terminal, the terminal transmits a TA_REG_PORT including a transmitter address and port number and a receiver's address and port number in a data section through a new third router to the transfer agent. Then, the transfer agent transmits L4_PEER_UPD including the new terminal address and the address and port number of the third router in the data section to a second terminal. Then, the terminal transmits the L4_PEER_UPD including the new terminal address and the address and port number of the third router in the data section to the second terminal. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a handoff method, a transfer agent, a terminal, and a program for a terminal connected via a NAPT router (Network Address Port Translation) (hereinafter also including a NAT (Network Address Translation) router).

  A home LAN (Local Area Network) and a corporate network are often connected to a global network such as the Internet via a NAPT router. The NAPT router mutually converts a private IP address used locally and a global IP address used on the Internet. As a result, a large number of private IP addresses can be assigned to a small number of global IP addresses. That is, more terminals than the number of global IP addresses can simultaneously access the Internet transparently.

  As a feature of the NAPT router, as long as there is no port forwarding setting, only connections in packets started to be transmitted from the network inside the NAPT router are allowed to pass.

Specifically, it is assumed that terminal A (IPa, port a) inside the NAPT router starts transmitting the following packet to terminal B (IPb, port B) outside the NAPT router.
Destination address: IPb, Port number: Port b
Source address: IPa, port number: port a
At this time, the following passable connections are set in the NAPT router.
[IPa: Port a] <-> [IPb: Port b]
When this passable connection is set, the packet transmitted from the terminal B to the terminal A is also allowed to pass.

RFC2663

  However, in many cases, a terminal moves from one network to the other as the wireless network is improved. Other newly connected networks may be inside the NAPT router. In this case, a new private IP address is assigned to the terminal. On the other hand, the counterpart terminal needs to know the global IP address of the new NAPT router after movement in order to transmit a packet to the terminal. Assume that the counterpart terminal can know the global IP address of the moved NAPT router. At this time, even if the counterpart terminal transmits a packet having the global IP address as the destination address, the NAPT router discards the packet as a connection not registered in the passable connection table.

  Therefore, the present invention provides a terminal handoff method and transfer in which the NAPT router does not discard packets to the terminal even if the terminal is connected to a network connected via the NAPT router by movement. An object is to provide an agent, a terminal, and a program.

According to the present invention, a plurality of local networks are connected to a backbone network via a router with a NAPT function, and the first terminal connected to the first local network is connected via the first router and the backbone network. A terminal handoff method executed when communicating with the second terminal,
A first transfer agent is connected to the first local network;
When a terminal connects to a third local network by movement and a new post-movement address is given to the terminal,
The terminal transmits a port registration message including the source address and port number and the address and port number of the second terminal in the data part to the first transfer agent via the third router. Steps,
A second step in which the first transfer agent transmits a movement update message including the post-movement address of the terminal and the address and port number of the third router in the data part to the second terminal;
The terminal includes a third step of transmitting a movement update message including a post-movement address of the terminal and an address and a port number of the third router in a data part to the second terminal.

  According to another embodiment of the handoff method of the present invention, the third step is also preferably performed simultaneously with the first step.

  According to another embodiment of the handoff method of the present invention, the second terminal that has received the movement update message transmits a movement update response message that uses the address of the third router after movement as the destination address. It is also preferable to further include a step.

According to the transfer agent of the present invention, a plurality of local networks are connected to a backbone network via a router with a NAPT function, and the first terminal connected to the first local network is connected to the first router and the backbone. A transfer agent connected to a first local network for a system communicating with a second terminal via a network;
When a terminal connects to a third local network by movement and a new post-movement address is given to the terminal,
Port registration message receiving means for receiving from the terminal a source address and port number, and a port registration message included in the address and port number of the second terminal and the data part;
It has a movement update message transmission means for transmitting a movement update message including the post-movement address of the terminal and the address and port number of the third router in the data part to the second terminal.

According to the present invention, a plurality of local networks are connected to a backbone network via a router with a NAPT function, and the first terminal connected to the first local network is connected via the first router and the backbone network. A system in communication with a second terminal in a system in which a transfer agent is connected to the first local network,
When a terminal connects to a third local network by movement and a new post-movement address is given to the terminal,
A port registration message transmitting means for transmitting a port registration message including a transmission source port number and the address and port number of the second terminal in the data part to the transfer agent;
It has a movement update message transmission means for transmitting a movement update message including the post-movement address of the terminal and the address and port number of the third router in the data part to the second terminal.

  According to another embodiment of the terminal of the present invention, when the mobile update message is received, the mobile update response message transmitting means for transmitting the mobile update response message having the destination address as the address of the third router after the movement is provided. It is also preferable to have it.

According to the present invention, a plurality of local networks are connected to a backbone network via a router with a NAPT function, and the first terminal connected to the first local network is connected via the first router and the backbone network. A program for causing a computer mounted on a transfer agent connected to the first local network to function for a system communicating with the second terminal,
When a terminal connects to a third local network by movement and a new post-movement address is given to the terminal,
Port registration message receiving means for receiving from the terminal a source address and port number, and a port registration message included in the address and port number of the second terminal and the data part;
The computer is caused to function as a movement update message transmitting means for transmitting a movement update message including the post-movement address of the terminal and the address and port number of the third router in the data portion to the second terminal.

According to the present invention, a plurality of local networks are connected to a backbone network via a router with a NAPT function, and the first terminal connected to the first local network is connected via the first router and the backbone network. A program for causing a computer mounted on a terminal in a system in which a transfer agent is connected to the first local network to function for a system communicating with the second terminal,
When a terminal connects to a third local network by movement and a new post-movement address is given to the terminal,
A port registration message transmitting means for transmitting a port registration message including a transmission source port number and the address and port number of the second terminal in the data part to the transfer agent;
The computer is caused to function as a movement update message transmitting means for transmitting a movement update message including the post-movement address of the terminal and the address and port number of the third router in the data portion to the second terminal.

  According to another embodiment of the terminal program of the present invention, when a move update message is received, a move update response message transmission for sending a move update response message with the address of the third router after the move as the destination address It is also preferable to further have means.

  According to the terminal handoff method, transfer agent, terminal, and program of the present invention, even when the terminal is connected to a network connected via the NAPT router by movement, the NAPT router is connected to the terminal. Packets can be prevented from being discarded. Further, according to the present invention, even when two terminals communicating with each other move at the same time, communication can be recovered even if the network after the movement is inside the NAPT router.

  Hereinafter, the best mode for carrying out the present invention will be described in detail with reference to the drawings.

  FIG. 1 is a sequence diagram of communication established before the terminal moves.

  According to FIG. 1, a plurality of local networks A to C are connected to a backbone (core) network via routers A to C with a NAPT function. Further, the terminal is movable and can be connected from one network to the other network. The terminal is automatically given a new address that can be used within the newly connected network. The port number is arbitrarily determined by the terminal on the own side or the other side, and is not assigned from the network.

Terminal A is connected to network A, and terminal B is connected to network B. Terminal A and terminal B have the following addresses and port numbers.
Terminal A: Address: Port number [1.1.1.1:1000]
Terminal B: Address: Port number [2.2.2.2:2000]

Network A is connected to the backbone network via router A, and network B is connected to the backbone network via router B. Router A and router B have the following addresses and port numbers for the backbone network.
Router A: Address: Port number [10.0.0.1:1111]
Router B: Address: Port number [10.0.0.2:2222]

(S101) Terminal A transmits an IP packet to terminal B. This IP packet has the following address and port number and is received by router A.
Destination address: Port number [10.0.0.2:2222] (Router B)
Source address: port number [1.1.1.1:1000] (terminal A)

(S102) Router A converts the source address of the IP packet received from terminal A into the address of router A.
Destination address: Port number [10.0.0.2:2222] (Router B)
Source address: Port number [10.0.0.1:1111] (Router A)
At this time, the router A has the following passable connection in order to allow the IP packet transmitted from the inside to the outside of the NAPT to pass the IP packet transferred in the reverse direction.
Passable connection of router A [1.1.1.1:1000<->10.0.0.2:2222]
(Terminal A) <-> (Router B)
Router A transmits the IP packet to router B via the backbone network.

(S103) Router B converts the destination address of the IP packet received from router A into the address of terminal B.
Destination address: Port number [2.2.2.2:2000]
Source address: port number [10.0.0.1:1111]
Then, the router B transmits the IP packet to the terminal B via the network B.

(S104) Terminal B transmits an IP packet to terminal A. This IP packet has the following address and port number and is received by router B.
Destination address: Port number [10.0.0.1:1111] (Router A)
Source address: port number [1.1.1.1:1000] (terminal B)

(S105) Router B converts the source address of the IP packet received from terminal B into the address of router A.
Destination address: Port number [10.0.0.1:1111] (Router A)
Source address: Port number [10.0.0.2:2222] (Router B)
At this time, the router B has the following passable connection in order to allow the IP packet transmitted from the inside to the outside of the NAPT to pass the IP packet transferred in the reverse direction.
Router B passable connection [10.0.0.1:1111<->2.2.2.2:2000]
(Router A) <-> (Terminal B)
Router B transmits the IP packet to router A via the backbone network.

(S106) The router A converts the destination address of the IP packet received from the router B into the address of the terminal A.
Destination address: port number [1.1.1.1:1000] (terminal A)
Source address: Port number [10.0.0.2:2222] (Router B)
Router A transmits the IP packet to terminal A via network A.

  FIG. 2 is a message format used by the present invention.

  According to FIG. 2, TA_REG_PORT (Transfer Agent_REGistration_PORT, port registration message) and L4_PEER_UPD (Layer 4 PEER UPDate, move update message) are represented.

  TA_REG_PORT is a message for the terminal after movement to register a port to the transfer agent connected to the network before movement. The role of TA_REG_PORT is to notify the transfer agent connected to the network before movement of the address and port number conversion state in the NAPT router connected to the terminal after movement.

  TA_REG_PORT in FIG. 2 includes an IP header, an L4 header, and an extension header. The IP header includes a destination address and a source address. The destination address is the address of the transfer agent before moving. The source address is the address of the terminal after movement. The L4 header includes a destination port number and a transmission source port number. The destination port number is the “standby port number” of the transfer agent before movement. The source port number is the “port number used as the source port” by the terminal before movement. Here, the port number of the terminal before movement and the port number of the terminal after movement are the same.

  The extension header is included in the data part, and includes the transmission source port number, the address and port number of the counterpart terminal. The source port number is the same as the source port number included in the L4 header. This is because the source port number in the L4 header is rewritten by the NAPT router. The address and port number of the counterpart terminal are the address and port number of the counterpart terminal with which the terminal communicated before moving.

  L4_PEER_UPD is a packet that explicitly notifies the counterpart terminal of the change of the IP address. The L4_PEER_UPD may be (1) the transfer agent that has received the TA_REG_PORT transmits to the counterpart terminal, or (2) the terminal itself after movement to the counterpart terminal.

  The L4_PEER_UPD in FIG. 2 includes an IP header, an L4 header, and an extension header. The IP header and the L4 header are the same as the TA_REG_PORT described above. The extension header includes a terminal address, a router address, and a port number. The terminal address is the same as the source address included in the L4 header. This is because the source address of the IP header is rewritten by the NAPT router. The address and port number of the counterpart terminal are the address and port number of the counterpart terminal with which the terminal communicated before moving.

  L4_PEER_UPD must be sent for all socket information. For example, if the mobile terminal holds 10 sockets (maintains 10 connections), 10 L4_PEER_UPDs must be transmitted. The socket information is information for identifying a connection in the terminal, and is a “source IP address, destination IP address, source port number, destination port number, protocol type (UDP / TCP)” pair. Of course, the L4_PEER_UPD and TA_REG_PORT messages in the present invention also depend on the protocol type (UDP / TCP) defined by the socket information.

  Note that L4_PEER_UPD has the configuration shown in FIG. 2, but it may be an IP packet that does not include data or may include data. The counterpart terminal that has received the L4_PEER_UPD that does not include data simply updates the socket information and does not pass it to the application as a data packet.

  Based on the basic sequence of FIG. 1, FIGS. 3 to 6 show a case where only one terminal moves to another network, and FIGS. 7 to 11 show a case where both terminals move to another network at the same time. Represents.

  FIG. 3 is a first sequence diagram when the terminal A moves to the network C.

  According to FIG. 3, a transfer agent A (Transfer Agent) A characteristic of the present invention is connected to a network A. The transfer agent functions as a temporary home agent for the counterpart terminal using the connection to the terminal before movement instead of the terminal after movement. As a result, direct communication recovery is realized between the terminal after movement and the counterpart terminal.

Transfer agent A has the following address and port number, and waits at port number 500.
Transfer Agent A: Address: Port number [1.1.1.9:500]

(S301) The terminal A finds the transfer agent A connected to the network A and acquires its IP address. The terminal A registers the pre-movement information with the transfer agent A. Thereby, the transfer agent A functions as a temporary home agent in the terminal A. That is, the transfer of the packet addressed to the terminal A is started when the terminal A registered before the movement receives a TA_REQ_PORT described later.

The transfer agent A periodically broadcasts an advertisement message informing the presence of the transfer agent A in the network. The advertisement message is realized by ICMP (Internet Control and Management Protocol). The advertisement message includes the following information, for example.
(1) Transfer agent address and port number (2) Network domain name (to distinguish the transfer agent after moving)
(3) A flag indicating that the network is inside / outside the NAPT router

  The terminal that receives the advertisement message knows the presence of the forwarding agent and can know whether the network is inside or outside the NAPT router.

(S302) It is assumed that the terminal A has moved from the network A to the network C. When the terminal A is connected to the network C, an IP address that can be used in the network C is automatically assigned. At this time, the port number is not changed. According to the present invention, the port number is unique among a plurality of communications.
Terminal A: Address: Port number [3.3.3.3:1000]

  Although not shown in FIG. 3, the terminal A connected to the new network C sends a transfer registration message such as TA_REG (Transfer Agent-REGistration) to the transfer agent A connected to the network A before moving through the router A. ) Send a message. TA_REG includes, for example, an IP address before movement, an IP address after movement, and socket information (port number pair, various flags, session key). If there are multiple connections, all socket information is included. By TA_REG (movement registration message), the transfer agent A knows that the previously connected terminal A is connected to the new network C.

  When the moved terminal A moves to the network inside the NAPT router, the terminal further transmits TA_REG_PORT. Whether or not it has moved to the inside of the NAPT router can be determined by an advertisement message received from the transfer agent connected to the network C after the movement. TA_REG_PORT is transmitted to all sockets.

(S303) Next, the terminal A transmits TA_REG_PORT to the transfer agent A. TA_REG_PORT containing the following information is received by router C:
IP / L4 header>
Destination address: Port number [10.0.0.1:500] (Router A)
Source address: port number [3.3.3.3:1000] (terminal A)
Extension header>
Source address: port number [3.3.3.3:1000] (terminal A)
Counterparty address: port number [10.0.0.2.2222] (terminal B)
The source address is an IP address newly assigned by connecting to the network C. On the other hand, the source port number is the same before and after the movement of the terminal A.

(S304) The router C converts the transmission source address into the address of the router C with respect to the TA_REG_PORT received from the terminal A.
IP / L4 header>
Destination address: Port number [10.0.0.1:500] (Router A)
Source address: Port number [10.0.0.3:1111] (Router C)
Extension header>
Source address: port number [3.3.3.3:1000] (terminal A)
Counterparty address: port number [10.0.0.2.2222] (terminal B)

At this time, for the TA_REG_PORT transmitted from the inside to the outside of the NAPT, the router C sets the following passable connection in order to allow the IP packet transferred in the reverse direction to pass.
Passable connection of router C [3.3.3.3:1000<->10.0.0.1:1111]
(Terminal A) <-> (Router A)
Then, the router C transmits the TA_REG_PORT to the router A via the backbone network.

(S305) Router A receives TA_REG_PORT from Router C. The port number of TA_REG_PORT represents [500]. The router A is set to wait for an IP packet at the port number [500] and forcibly forward it to the transfer agent A (static address-port conversion, port forwarding function). Therefore, the router A forcibly transmits all of the IP packets of destination address: port number [10.0.0.1:500] received from the backbone network to the transfer agent A.

The router A converts the destination address of the TA_REG_PORT received from the router C into the address of the transfer agent A.
IP / L4 header>
Destination address: Port number [1.1.1.9:500] (Agent A)
Source address: Port number [10.0.0.3:1111] (Router C)
Extension header>
Source address: port number [3.3.3.3:1000] (terminal A)
Counterparty address: port number [10.0.0.2.2222] (terminal B)
Then, the router A transmits the TA_REG_PORT to the transfer agent A via the network A.

  The transfer agent A before moving can know the address-port conversion performed by the NAPT router by looking at the header (IP, L4, extension) of the received TA_REG_PORT. The transfer agent A can record the NAPT conversion rule (that is, the pair of the outside IP address of the NAPT router and the outside source port number).

  FIG. 4 is a second sequence diagram when the terminal A moves to the network C.

  As shown in FIGS. 1, 3, and 4, when the counterpart terminal is also connected to the network inside the NAPT router, the terminal A after the movement includes an IP packet including the destination address and port number of the terminal B The IP packet is discarded by the router B. This is because the source address of the IP packet transmitted from the terminal A to the terminal B is different, so that the source address after the movement is not set in the passable connection of the router B.

  Here, according to the present invention, the movement of the terminal A is notified to the terminal B using the passable connection already set in the router B. For this purpose, transfer agent A transmits L4_PEER_UPD to terminal B via router A and router B.

(S401) Upon receiving TA_REG_PORT, transfer agent A immediately transmits L4_PEER_UPD to router A. The L4_PEER_UPD has the following information and is received by the router A.
IP / L4 header>
Destination address: Port number [10.0.0.2:2222] (Router B)
Source address: port number [1.1.1.1:1000] (terminal A)
Extension header>
Terminal address after movement: port number [3.3.3.3:1000] (terminal A)
Router address after movement: port number [10.0.0.3:1111] (Router C)

(S402) The router A converts the transmission source address into the address of the router A for L4_PEER_UPD received from the transfer agent A.
IP / L4 header>
Destination address: Port number [10.0.0.2:2222] (Router B)
Source address: Port number [10.0.0.1:1111] (Router A)
Extension header>
Terminal address after movement: port number [3.3.3.3:1000] (terminal A)
Router address after movement: port number [10.0.0.3:1111] (Router C)
Then, router A transmits the L4_PEER_UPD to router B via the backbone network.

(S403) Router B receives L4_PEER_UPD from Router A. Router B has already set the following passable connections.
Router B passable connection [10.0.0.1:1111<->2.2.2.2:2000]
(Router A) <-> (Terminal B)
Therefore, the router B converts the destination address of the L4_PEER_UPD received from the router A into the address of the terminal B.
IP / L4 header>
Destination address: port number [2.2.2.2:2000] (terminal B)
Source address: port number [10.0.0.1:1111] (Router A)
Extension header>
Terminal address after movement [3.3.3.3] (Terminal A)
Router address after movement: port number [10.0.0.3:1111] (Router C)
Then, the router B transmits the L4_PEER_UPD to the terminal B via the network B.

The terminal B updates the socket information as follows by the sequence of S301 to S403.
Terminal A: Destination address: Port number [1.1.1.1:1000]
↓
Terminal A: Destination address: Port number [3.3.3.3:1000]
Move destination router: Destination address: Port number [10.0.0.3:1111]

  FIG. 5 is a third sequence diagram when the terminal A moves to the network C.

(S501) Terminal B attempts to transmit L4_PEER_ACK (movement update response message) to terminal A. This is necessary when the terminal B is connected to the network inside the NAPT router. As a result, the permission of the connection with the router C can be set for the passable connection of the router B.

Terminal B transmits L4_PEER_ACK to router B. Terminal B knows that terminal A has moved to the network inside router C. The L4_PEER_ACK has the following information and is received by the router B.
Destination address: Port number [10.0.0.3:1111] (Router C)
Source address: port number [2.2.2.2:2000] (terminal B)

(S502) The router B converts the transmission source address into the address of the router B for L4_PEER_ACK received from the terminal B.
Destination address: Port number [10.0.0.3:1111] (Router C)
Source address: Port number [10.0.0.2:2222] (Router B)
At this time, for the L4_PEER_ACK transmitted from the inside to the outside of the NAPT, the router B further sets the following passable connection in order to allow the IP packet transferred in the reverse direction to pass.
Router B passable connection [10.0.0.1:1111<->2.2.2.2:2000]
(Router A) <-> (Terminal B)
[10.0.0.3:1111<->2.2.2.2:2000]
(Router C) <-> (Terminal B)
Then, the router B transmits the L4_PEER_ACK to the router C through the backbone network.

  However, the router C does not set the address [10.0.0.2:2222] of the router B in the passable connection. Therefore, the router C discards the L4_PEER_ACK received from the router B. Here, the L4_PEER_ACK transmitted from the terminal B to the terminal A serves only to set a passable connection in the router B.

  FIG. 6 is a fourth sequence diagram when the terminal A moves to the network C.

  The sequence shown in FIG. 6 may be executed in conjunction with FIG. That is, the terminal A transmits TA_REG_PORT to the transfer agent A and transmits L4_PEER_UPD to the terminal B. At this time, although the state as shown in FIG. 5 does not occur, conversely, the router B may discard the L4_PEER_UPD.

(S601) The terminal A connected to the network C transmits L4_PEER_UPD to the terminal B. The L4_PEER_UPD has the following information and is received by the router A.
IP / L4 header>
Destination address: Port number [10.0.0.2:2222] (Router B)
Source address: port number [3.3.3.3:1000] (terminal A)
Extension header>
Terminal address after movement: port number [3.3.3.3:1000] (terminal A)
Moved router address: port number [0]

  The post-movement terminal address included in the extension header is the same as the source address included in the IP header. Since this IP packet passes through the NAPT router and the source address is rewritten, it also serves to notify the counterpart terminal by including the source address in the extension header.

  Note that the post-movement router address: port number is unknown to the terminal A, and [0] is set. The terminal B can know the address: port number of the router after movement through S403 in FIG.

(S602) For the L4_PEER_UPD received from the terminal A, the router C converts the source address to the address of the router C.
IP / L4 header>
Destination address: Port number [10.0.0.2:2222] (Router B)
Source address: Port number [10.0.0.3:1111] (Router C)
Extension header>
Terminal address after movement: port number [3.3.3.3:1000] (terminal A)
Moved router address: port number [0]
At this time, for the L4_PEER_UPD transmitted from the inside to the outside of the NAPT, the router A further sets the following passable connection in order to allow the IP packet transferred in the reverse direction to pass.
Passable connection of router C [3.3.3.3:1000<->10.0.0.1:1111]
(Terminal A) <-> (Router A)
[3.3.3.3:1000<->10.0.0.2:2222]
(Terminal A) <-> (Router B)
Then, the router C transmits the L4_PEER_UPD to the router B via the backbone network.

(S603) Router B receives L4_PEER_UPD from Router A. Router B has already set the following passable connections.
Router B passable connection [10.0.0.1:1111<->2.2.2.2:2000]
(Router A) <-> (Terminal B)
[10.0.0.3:1111<->2.2.2.2:2000]
(Router C) <-> (Terminal B)
Therefore, the router B converts the destination address of the L4_PEER_UPD received from the router A into the address of the terminal B.
IP / L4 header>
Destination address: port number [2.2.2.2:2000] (terminal B)
Source address: Port number [10.0.0.3:1111] (Router C)
Extension header>
Terminal address after movement: port number [3.3.3.3:1000] (terminal A)
Router address after movement: port number [10.0.0.3:1111] (Router C)
Then, the router B transmits the L4_PEER_UPD to the terminal B via the network B.

  FIG. 7 is a first sequence diagram when the terminal A and the terminal B move on the network at the same time.

(S701 to S705) The movement of the terminal A is exactly the same as S301 to S305 in FIG.
(S711 to S715) The movement of the terminal B is exactly the same as S301 to S305 in FIG.

  FIG. 8 is a second sequence diagram when the terminal A and the terminal B move on the network at the same time.

(S801 to S802) The movement of the terminal A is exactly the same as S401 to S402 in FIG. Although not shown, the terminal B transmits L4_PEER_UPD to the transfer agent A via the router B and the router A even when the terminal B moves.

(S803) Router B receives L4_PEER_UPD from router A. Router B has already set the following passable connections.
Router B passable connection [10.0.0.1:1111<->2.2.2.2:2000]
(Router A) <-> (Transfer Agent B)
Therefore, the router B converts the destination address of the L4_PEER_UPD received from the router A into the address of the terminal B.
IP / L4 header>
Destination address: Port number [2.2.2.2:2000] (Agent B)
Source address: Port number [10.0.0.1:1111] (Router A)
Extension header>
Terminal address after movement: port number [3.3.3.3:1000] (terminal A)
Router address after movement: port number [10.0.0.3:1111] (Router C)
Here, an IP packet whose destination address is the address of terminal B after movement is transmitted to transfer agent B. At this time, the transfer agent B immediately operates in the next sequence S901.

  FIG. 9 is a third sequence diagram when the terminal A and the terminal B move on the network at the same time.

(S901) Upon receiving L4_PEER_UPD, transfer agent B immediately transmits L4_PEER_UPD to router D. The L4_PEER_UPD has the following information and is received by the router B.
IP / L4 header>
Destination address: Port number [10.0.0.4:4444] (Router D)
Source address: port number [2.2.2.2:2000] (terminal B)
Extension header>
Terminal address after movement: port number [3.3.3.3:1000] (terminal A)
Router address after movement: port number [10.0.0.3:1111] (Router C)

(S902) The router B converts the source address to the address of the router A for L4_PEER_UPD received from the transfer agent B.
IP / L4 header>
Destination address: Port number [10.0.0.4:4444] (Router D)
Source address: Port number [10.0.0.2:2222] (Router B)
Extension header>
Terminal address after movement: port number [3.3.3.3:1000] (terminal A)
Router address after movement: port number [10.0.0.3:1111] (Router C)
Then, the router B transmits the L4_PEER_UPD to the router D through the backbone network.

(S903) Router D receives L4_PEER_UPD from Router B. Router D has already set the following passable connections.
Allowable connection of Router B [10.0.0.2:2222<->4.4.4.4:2000]
(Router B) <-> (Terminal B)
Therefore, the router D converts the destination address of the L4_PEER_UPD received from the router B into the address of the terminal B.
IP / L4 header>
Destination address: port number [4.4.4.4:2000] (terminal B)
Source address: Port number [10.0.0.2:2222] (Router B)
Extension header>
Terminal address after movement: port number [3.3.3.3:1000] (terminal A)
Router address after movement: port number [10.0.0.3:1111] (Router C)
Then, the router D transmits the L4_PEER_UPD to the terminal B via the network B.

  FIG. 10 is a fourth sequence diagram when terminal A and terminal B move through the network at the same time.

(S1001) Terminal B attempts to transmit L4_PEER_ACK to terminal A. This is necessary when the terminal B is connected to the network inside the NAPT router. As a result, the permission of the connection with the router C can be set in the passable connection of the router D.

Terminal B transmits L4_PEER_ACK to router D. Terminal B knows that terminal A has moved to the network inside router C. This L4_PEER_ACK has the following information and is received by the router D.
Destination address: Port number [10.0.0.3:1111] (Router C)
Source address: port number [4.4.4.4:2000] (terminal B)

(S1002) The router D converts the transmission source address into the address of the router D for L4_PEER_ACK received from the terminal B.
Destination address: Port number [10.0.0.3:1111] (Router C)
Source address: Port number [10.0.0.4:2000] (Router D)
At this time, for the L4_PEER_ACK transmitted from the inside to the outside of the NAPT, the router D further sets the following passable connection in order to allow the IP packet transferred in the reverse direction to pass.
Passable connection of router D [10.0.0.2:2222<->4.4.4.4:2000]
(Router B) <-> (Terminal B)
[10.0.0.3:1111<->4.44.4:2000]
(Router C) <-> (Terminal B)
Then, the router D transmits the L4_PEER_ACK to the router C via the backbone network.

  However, the router C does not set the address [10.0.0.4:4444] of the router D in the passable connection. Therefore, the router C discards the L4_PEER_ACK received from the router D. Here, the L4_PEER_ACK transmitted from the terminal B to the terminal A serves only to set a passable connection in the router D.

  FIG. 11 is a fifth sequence diagram when terminal A and terminal B move through the network at the same time.

  The sequence from S801 to S903 in FIG. 8 and FIG. Accordingly, terminal S transmits L4_PEER_ACK to terminal B in the same manner as terminal B transmits L4_PEER_ACK to terminal A in S1001 of FIG. In the following, it is assumed that L4_PEER_ACK is transmitted from terminal B first, and then L4_PEER_ACK is transmitted from terminal A.

(S1101) Terminal A connected to network C transmits L4_PEER_ACK to terminal B. This L4_PEER_ACK has the following information and is received by the router A.
Destination address: Port number [10.0.0.4:4444] (Router D)
Source address: port number [3.3.3.3:1000] (terminal A)

(S1102) The router C converts the source address to the address of the router C for L4_PEER_ACK received from the terminal A.
Destination address: Port number [10.0.0.4:4444] (Router D)
Source address: Port number [10.0.0.3:1111] (Router C)
At this time, for the L4_PEER_UPD transmitted from the inside to the outside of the NAPT, the router A further sets the following passable connection in order to allow the IP packet transferred in the reverse direction to pass.
Passable connection of router C [3.3.3.3:1000<->10.0.0.1:1111]
(Terminal A) <-> (Router A)
[3.3.3.3:1000<->10.0.0.4:4444]
(Terminal A) <-> (Router D)
Then, the router C transmits the L4_PEER_UPD to the router D through the backbone network.

(S1103) The router D receives L4_PEER_ACK from the router A. Router D has already set the following passable connections.
Passable connection of router D [10.0.0.2:2222<->4.4.4.4:2000]
(Router B) <-> (Terminal B)
[10.0.0.3:1111<->4.44.4:2000]
(Router C) <-> (Terminal B)
Therefore, the router D converts the destination address into the address of the terminal B for L4_PEER_ACK received from the router C.
Destination address: port number [4.4.4.4:2000] (terminal B)
Source address: Port number [10.0.0.3:1111] (Router C)
Then, the router D transmits the L4_PEER_ACK to the terminal B via the network D.

  As described above, FIGS. 1 and 3 to 11 have been described on the assumption that the terminal after movement is connected to the network inside the NAPT router. Here, even if the terminal after movement is directly connected to a network without a NAPT router, for example, a backbone network, the sequence operation described above is exactly the same.

  In this case, the IP header of the L4_PEER_UPD transmitted from the terminal after movement and the source address and port number of the L4 header reach the counterpart NAPT router (or counterpart terminal) without being rewritten. The port number of the terminal after moving remains 0. Similarly, the IP header and L4 header of TA_REG_PORT are not rewritten. After all, there is no difference between the contents of the IP header and the L4 header and the contents of the extension header. For example, in FIG. 10, if the router C is not a NAPT router, the L4_PEER_ACK simply passes through the router C and reaches the terminal A.

  FIG. 12 is a functional configuration diagram of the terminal and the transfer agent in the present invention.

  The transfer agent 1 includes a port registration message reception unit 11, a movement update message transmission unit 12, a movement registration message reception unit 13, a packet transfer unit 14, and an advertisement message transmission unit 15. These functional units can also be realized by executing a program that causes a computer installed in the transfer agent to function.

  The port registration message receiving unit 11 receives TA_REG_PORT including the transmission source address and port number and the address and port number of the counterpart terminal in the data part from the terminal. The terminal A is specified by the source address and the port number. Also, it recognizes that the terminal A wants to update the connection with the terminal B by the address and port number of the counterpart terminal.

  The movement update message transmission unit 12 transmits L4_PEER_UPD including the post-movement address of the terminal and the address and port number of the moved router in the data part to the counterpart terminal. L4_PEER_UPD can pass through the partner router through the connection of the terminal before movement. Thereby, the counterpart terminal recognizes the address of the terminal after movement, and recognizes that the packet to be transmitted to the terminal should be transmitted to the address and port number of the router after the movement.

  The movement registration message receiving unit 13 receives a movement registration message (TA_REG) including an address after movement from the terminal. The updated moved address is registered in the transfer table of the packet transfer unit 14.

  The packet transfer unit 14 uses the transfer table to transfer a packet to be transmitted to the terminal before movement to the terminal after movement. The forwarding table corresponds to the movement registration message.

  The advertisement message transmission unit 15 periodically transmits an advertisement message informing the presence of the advertisement message in the network.

  The terminal 2 includes a port registration message transmission unit 21, a movement update message transmission unit 22, a movement update message reception unit 23, a movement update response message transmission unit 24, a movement registration message transmission unit 25, and a packet transmission / reception unit 26. And an advertisement message receiving unit 27. These functional units can also be realized by executing a program that causes a computer installed in the terminal to function.

  The port registration message transmission unit 21 transmits TA_REG_PORT including the transmission source address and port number and the address and port number of the counterpart terminal in the data part to the transfer agent 1. Thereby, the transfer agent identifies the terminal after movement by the source address and the port number, and recognizes that the terminal A wants to update the connection with the terminal B by the address and port number of the counterpart terminal.

  The movement update message transmission unit 22 transmits L4_PEER_UPD including the post-movement address of the terminal and the address and port number of the moved router in the data part to the counterpart terminal. As a result, a passable connection with the counterpart terminal can be set in the moved router.

  The movement update message receiving unit 23 receives L4_PEER_UPD from the transfer agent 1 or the counterpart terminal. In addition, the movement update message reception unit 23 notifies the movement update response message transmission unit 24 that L4_PEER_UPD has been received.

  The movement update response message transmission unit 24 transmits L4_PEER_ACK to the counterpart terminal when the movement update message reception unit 23 receives L4_PEER_UPD. As a result, a passable connection with the counterpart terminal can be set in the router.

  The movement registration message transmission unit 25 transmits TA_REG including one or more pieces of socket information to the transfer agent 1.

  The packet transmitting / receiving unit 26 transmits / receives a packet to / from a counterpart terminal, a counterpart router, or a transfer agent.

  The advertisement message receiving unit 27 receives the advertisement message and knows the presence of the transfer agent 1.

  Finally, the application state of the present invention will be described.

  According to the earlier application invention by the same applicant (Japanese Patent Application No. 2005-358837), even if the address of the terminal after movement is changed by assigning a unique port number, the correspondence of the port number , Update the address automatically. Thereby, even if a terminal moves, a socket can be validated and a connection is not cut | disconnected.

  However, when a terminal or an agent device is connected to a network inside the NAPT router, all signaling and data packets with the terminal after movement cannot pass through the NAPT router. Therefore, according to the present invention, even if the terminal moves to the network inside the NAPT router, communication can be recovered without disconnecting the connection by the opposing terminal.

  The previous invention will be specifically described. It is assumed that when the terminal A (IPa, port a) and the terminal B (IPa, port a) are communicating, the terminal A moves and newly acquires IPna. In addition, a unique number is assigned to the port number, and the uniqueness of the source port number-destination port number pair is guaranteed. For this reason, when a packet of destination address: port number [IPna: port a] is received, it can be recognized that the destination address of port a has been changed from IPa to IPna. Based on this, the address of terminal A in the socket information is changed to IPna.

  As described above in detail, according to the terminal handoff method, transfer agent, terminal, and program of the present invention, when the terminal is connected to the network connected via the NAPT router by movement. In addition, it is possible to prevent the NAPT router from discarding the packet to the terminal. Further, according to the present invention, even if two terminals communicating with each other move at the same time, the network after the movement can be used only on the inside / outside of the NAPT router by using a transfer agent temporarily. Regardless of the communication, communication can be recovered.

  According to the various embodiments of the present invention described above, those skilled in the art can easily make various changes, modifications and omissions within the scope of the technical idea and the viewpoint of the present invention. The above description is merely an example, and is not intended to be restrictive. The invention is limited only as defined in the following claims and the equivalents thereto.

It is a sequence diagram of communication established before the terminal moves. It is a message format used by the present invention. FIG. 6 is a first sequence diagram when terminal A moves to network C. FIG. 10 is a second sequence diagram when terminal A moves to network C. FIG. 10 is a third sequence diagram when terminal A moves to network C. FIG. 10 is a fourth sequence diagram when terminal A moves to network C. It is a 1st sequence diagram when the terminal A and the terminal B move the network simultaneously. It is a 2nd sequence diagram when the terminal A and the terminal B move the network simultaneously. It is a 3rd sequence diagram when the terminal A and the terminal B move the network simultaneously. It is a 4th sequence diagram when the terminal A and the terminal B move the network simultaneously. It is a 5th sequence diagram when the terminal A and the terminal B move the network simultaneously. It is a function block diagram of the terminal and transfer agent in this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Transfer agent 11 Port registration message receiving part 12 Movement update message transmission part 13 Movement registration message reception part 14 Packet transfer part 15 Advertisement message transmission part 2 Terminal 21 Port registration message transmission part 22 Movement update message transmission part 23 Movement update message reception part 24 movement update response message transmission unit 25 movement registration message transmission unit 26 packet transmission / reception unit 27 advertisement message reception unit

Claims (9)

A plurality of local networks are connected to the backbone network via a router with a network address port translation (NAPT) function, and the first terminal connected to the first local network connects the first router and the backbone network. A terminal handoff method performed when communicating with the second terminal via:
A first transfer agent is connected to the first local network;
When the terminal connects to a third local network by movement and a new post-movement address is given to the terminal,
The terminal transmits a port registration message including the source address and port number and the address and port number of the second terminal in the data part to the first transfer agent via the third router. And the steps
A second step in which a first transfer agent transmits a movement update message including the post-movement address of the terminal and the address and port number of a third router in a data part to a second terminal;
The terminal includes a third step of transmitting a movement update message including the post-movement address of the terminal and the address and port number of a third router in a data part to the second terminal. The terminal handoff method.   The terminal handoff method according to claim 1, wherein the third step is executed simultaneously with the first step.   The second step of receiving the movement update message further comprises a fourth step of transmitting a movement update response message having the destination address as the address of the third router after movement. The terminal handoff method according to 2. A plurality of local networks are connected to the backbone network via a router with a NAPT function, and the first terminal connected to the first local network is connected to the second network via the first router and the backbone network. A transfer agent connected to a first local network for a system communicating with a terminal,
When the terminal connects to a third local network by movement and a new post-movement address is given to the terminal,
Port registration message receiving means for receiving a source address and port number from the terminal, and a port registration message included in the address and port number of the second terminal and the data part;
A transfer update message sending means for sending a move update message including the post-movement address of the terminal and the address and port number of a third router in a data part to a second terminal; Agent. A plurality of local networks are connected to the backbone network via a router with a NAPT function, and the first terminal connected to the first local network is connected to the second network via the first router and the backbone network. For a system communicating with a terminal, the terminal in a system in which a transfer agent is connected to a first local network,
When the terminal connects to a third local network by movement and a new post-movement address is given to the terminal,
A port registration message transmitting means for transmitting a port registration message including a transmission source port number and the address and port number of the second terminal in the data part to the transfer agent;
A terminal comprising: a movement update message transmission means for transmitting a movement update message including the post-movement address of the terminal and the address and port number of a third router in a data part to the second terminal. .   6. The mobile update response message transmitting means for transmitting a mobile update response message having a destination address of the address of the third router after the movement when the mobile update message is received. Terminal. A plurality of local networks are connected to the backbone network via a router with a NAPT function, and the first terminal connected to the first local network is connected to the second network via the first router and the backbone network. A program for operating a computer mounted on a transfer agent connected to a first local network for a system communicating with a terminal,
When the terminal connects to a third local network by movement and a new post-movement address is given to the terminal,
Port registration message receiving means for receiving a source address and port number from the terminal, and a port registration message included in the address and port number of the second terminal and the data part;
A computer is caused to function as a movement update message transmitting means for transmitting a movement update message including the post-movement address of the terminal and the address and port number of a third router in a data part to a second terminal. Transfer agent program to be executed. A plurality of local networks are connected to the backbone network via a router with a NAPT function, and the first terminal connected to the first local network is connected to the second network via the first router and the backbone network. For a system that communicates with a terminal, a program that causes a computer installed in the terminal in a system in which a transfer agent is connected to a first local network to function,
When the terminal connects to a third local network by movement and a new post-movement address is given to the terminal,
A port registration message transmitting means for transmitting a port registration message including a transmission source port number and the address and port number of the second terminal in the data part to the transfer agent;
A computer is caused to function as a movement update message transmitting means for transmitting a movement update message including the post-movement address of the terminal and the address and port number of a third router in a data part to a second terminal. Terminal program to be used.   9. The mobile update response message transmitting unit according to claim 8, further comprising: a mobile update response message transmitting unit configured to transmit an update response message having a destination address of the address of the third router after the movement when the mobile update message is received. Terminal program.

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