JP4375163B2 - Packet transfer method and transfer device - Google Patents

Description

  The present invention relates to a packet transfer method and a transfer apparatus when a mobile terminal is handed over in an IP (Internet Protocol) network.

  Some mobile terminals using the conventional Internet protocol use mobile IP. A mobile communication system using mobile IP includes a mobile terminal that communicates while moving through a sub-network, a home agent device that manages location of the mobile terminal, a communication partner terminal connected to the Internet that communicates with the mobile terminal, The access router device is connected to a terminal for communicating with a communication partner terminal connected to the Internet. When a mobile terminal moves to a different sub-network, it receives a router advertisement message from the access router device belonging to the destination sub-network, and uses the prefix information included in the message as a care-of address to be temporarily used in that sub-network. Generate. Thereafter, the mobile terminal transmits a binding update message including the home address and the newly generated care-of address to the home agent device. The home agent device receives the binding update message, and adds the combination of the home address and the care-of address included in the received binding update message to the binding cache storing the combination of the home address and the care-of address corresponding thereto. Thereafter, the packet transmitted to the home address of the mobile terminal is received by proxy by the home agent device and transferred to the current care-of address of the mobile terminal.

  In the mobile communication system using the mobile IP described above, the mobile terminal is addressed to the home address of the mobile terminal after the mobile terminal moves to a different subnetwork until the care-of address acquired at the destination is registered in the home agent device. The received packet is transferred from the home agent device to the care-of address before the mobile terminal moves. For this reason, since the mobile terminal does not exist at the destination care-of address, a loss of the transferred packet occurs.

  As a conventional method for solving this problem, there is a method described in Patent Document 1. In this Patent Document 1, a home agent device temporarily stores a packet addressed to a mobile terminal in response to a request from the mobile terminal, and stores the stored packet after the mobile terminal's binding update processing is completed. A packet transfer method for reducing packet loss by transferring to a packet is disclosed.

  FIG. 12 is a flowchart showing the operation of this home agent device. In FIG. 12, when the home agent device receives a packet addressed to the mobile terminal (mobile station) by proxy (step S131), the home agent device determines whether or not the mobile terminal is in a communication disabled period indicating a communication disabled state (step S132). If the communication is impossible, the proxy received packet is stored in the buffer (step S133). If it is outside the communication disabled period, the packet is transferred to the mobile terminal according to the normal mobile IP procedure (step S134).

  Further, when a packet is received from the mobile terminal (step S135) and the communication disabled period start message indicating that the communication disabled period is entered or the communication disabled period end message indicating that the communication disabled period is ended (step S136). ) Update the mobile terminal state on the binding cache (step S137).

Further, in the conventional IP network, when the packet cannot be delivered to the mobile terminal, an ICMP destination unreachable (Unreachable) message is returned to the packet transmission source. Further, as shown in FIG. 13, in the conventional mobile IP, the packet destined for the home address of the mobile terminal 20 received by the home agent device 10 from the communication terminal 30 is tunnel-transferred to the care-of address of the mobile terminal (step S200). When the ICMP destination unreachable message is received when the transfer packet is undeliverable (step S201) (step S202), the ICMP destination unreachable message is immediately issued to the packet source (step S203). . The protocol or application higher than the IP layer of the communication terminal 30 that has received the ICMP destination unreachable message may take measures such as stopping transmission of data in response to the failure to deliver the packet (step S204). .
JP 2003-209890 A (page 8, FIG. 7)

  However, in the packet transfer method of Patent Document 1, it is necessary for the mobile terminal to explicitly notify the home agent device that the communication incompletion period is entered, and the mobile terminal is unexpectedly disconnected from the link or from the link in the middle of notification. In such a case, the notification fails, and the home agent device cannot cope with it, resulting in a packet loss.

  The present invention has been made to solve the above problem, and even when the mobile terminal is disconnected from the link and cannot be notified to the home agent device, the mobile communication terminal can communicate again. It is an object of the present invention to provide a packet transfer method that can be received continuously.

  The packet transfer method according to the present invention includes a step in which a transfer device on an IP network receives and transfers a packet addressed to a mobile terminal by proxy, and the transfer device receives a packet transfer request from the mobile terminal within a predetermined time. The stored packet is transferred to the mobile terminal, and when it is not received, the stored packet is discarded.

  As a result, the transfer device temporarily stores the packet addressed to the mobile terminal disconnected from the link without explicitly notifying the mobile terminal of the disconnection to itself, and the packet stored when the mobile terminal connects to the link again. By transferring, packet transfer that can avoid session disconnection can be realized. Further, by discarding old packets according to the size of the storage area, the system operation rate can be increased.

  In the packet transfer method according to the present invention, the transfer device initially stores the packet in the high-speed access memory, and when receiving the non-delivery notice for the transferred packet, the stored packet addressed to the mobile terminal is accessed at high speed. The data is stored in a storage unit having a larger storage capacity than the memory.

  As a result, for example, temporarily stored packets that require a large amount of processing per unit time can be accessed at high speed, but there is little memory, and officially stored packets can be accessed at medium speed but memory can be stored in large areas. By changing the storage area according to the property, the processing efficiency can be improved.

The packet transfer method according to the present invention also includes a step of storing a non-delivery notice when receiving a non-delivery notice for a packet transferred by the transfer apparatus, and a packet transfer from a mobile terminal within a predetermined time after the transfer apparatus starts saving. When the request is not received, the method further includes a step of transmitting a non-delivery notice to the transmission source of the packet destined for the mobile terminal based on the non-delivery notice and discarding the stored packet destined for the mobile terminal.

  As a result, at the time of a handover that is completed in a short period, the timing for transmitting the undeliverable communication to the packet transmission source is delayed to conceal the handover period, thereby improving the efficiency of communication and session.

  The packet transfer method according to the present invention also includes a step of storing a non-delivery notice when receiving a non-delivery notice for a packet transferred by the transfer device, and a movement before the amount of packets saved by the transfer device exceeds a predetermined amount. And a step of sending a non-delivery notice to the source of the packet destined for the mobile terminal based on the non-delivery notice when the packet transfer request from the terminal is not received and discarding the stored mobile terminal-destined packet It is.

  As a result, the end-to-end communication bandwidth is maintained by delaying the timing of sending the non-delivery notice to the packet transmission source to the upper limit value assigned according to the packet storage area, and in particular, a bandwidth management type protocol such as TCP , The session can be resumed at a high transmission rate when the handover is completed.

  The packet transfer method according to the present invention includes a step of adding an identifier to a packet transferred by the transfer device to the mobile terminal, and a delivery failure notification for the packet transferred by the transfer device. And a step of discarding a packet stored before the same packet as the identifier of the packet addressed to the mobile terminal included in the disabled notification.

  As a result, it is possible to accurately identify the packet for starting formal storage, and avoid receiving duplicate packets by the mobile terminal after the handover is completed.

  Further, the identifier in the packet transfer method according to the present invention is a sequence number for each packet, and the processing efficiency of the transfer apparatus can be improved by giving a simple identifier.

  Further, the identifier in the packet transfer method according to the present invention is a value calculated from a portion excluding the IP header of the packet, and since the assigned identifier can be calculated from the packet header, There is no need to store it in the transfer device, and the use efficiency of the storage area can be improved.

  A transfer device according to the present invention includes a packet transfer unit that transfers a packet addressed to a mobile terminal, a packet storage unit that stores the packet, and receives a packet transfer request from the mobile terminal by proxy reception of a packet addressed to the mobile terminal. When receiving the proxy reception notification from the receiving unit, the received packet is stored in the packet storage unit, and the packet storage request is received from the reception unit to store the packet. A transfer control unit for instructing the packet transfer unit to transfer the packet stored in the unit to the mobile terminal.

  As a result, the mobile terminal temporarily saves the packet addressed to the mobile terminal disconnected from the link without explicitly notifying the mobile terminal, and transfers the saved packet when the mobile terminal connects to the link again. Packet transfer capable of avoiding disconnection is realized.

The transfer device according to the present invention further includes a timer that counts the time until the packet stored in the packet storage unit is discarded, and before the transfer control unit receives a notification of the elapsed time from the timer to the discard, When the packet transfer request is not received, the stored packet is discarded.

  Thereby, since the old packet is discarded, the system operation rate can be increased.

  The transfer apparatus according to the present invention stores the transfer control unit in the high-speed access memory at the initial stage of proxy reception, and receives the notification of delivery failure notification for the transferred packet from the reception unit when the transfer control unit receives from the high-speed access memory. The data is stored in a storage unit having a large storage capacity.

  As a result, for example, temporarily stored packets that require a large amount of processing per unit time can be accessed at high speed, but there is little memory, and officially stored packets can be accessed at medium speed but memory can be stored in large areas. By changing the storage area according to the property, the processing efficiency can be improved.

Furthermore, in the transfer device according to the present invention, the transfer control unit discards the stored packet if the packet transfer request cannot be received from the mobile terminal even after a predetermined time has elapsed after temporarily storing or officially storing the packet. It is characterized by
Furthermore, the transfer device according to the present invention further includes a message storage unit that stores the received non-delivery notification, and the transfer control unit receives the non-delivery notification when the transferred packet is received. When the packet transfer request is not received before receiving the notification of the elapse of time from the timer to the discard, the non-delivery notification is transmitted to the transmission source of the packet addressed to the mobile terminal based on the non-delivery notification and the packet is stored. The packet destined for the mobile terminal saved from the unit is discarded.

  As a result, at the time of a handover that is completed in a short period, it is possible to conceal the handover period by delaying the timing for transmitting the undeliverable communication to the packet transmission source, thereby improving the efficiency of communication and session.

  The transfer device according to the present invention further includes a message storage unit that stores the received non-delivery notice, and when the transfer control unit receives the non-delivery notice for the transferred packet, the non-delivery notice is sent to the message storage unit. When the packet transfer request from the mobile terminal is not received before the packet amount stored in the packet storage unit exceeds the predetermined amount, the packet cannot be delivered to the source of the packet addressed to the mobile terminal based on the non-delivery notification The notification is transmitted, and the mobile terminal-addressed packet stored from the packet storage unit is discarded.

As a result, the end-to-end communication bandwidth is maintained by delaying the timing of sending the non-delivery notice to the packet transmission source to the upper limit value assigned according to the packet storage area, and in particular, a bandwidth management type protocol such as TCP , The session can be resumed at a high transmission rate when the handover is completed.
In addition, the packet transfer unit of the transfer device according to the present invention adds an identifier to the packet addressed to the mobile terminal received by the reception unit and transmits the packet. In the packet stored in the packet storage unit, the packet transfer unit notifies the delivery failure notification. A packet determination unit that discards a packet stored before the same packet as the identifier of the included packet addressed to the mobile terminal, and a packet when the transfer control unit receives a notification of non-delivery from the receiving unit; It instructs the discrimination unit to determine whether to discard the packet stored in the packet storage unit.

  As a result, it is possible to accurately identify the packet for starting formal storage, and avoid receiving duplicate packets by the mobile terminal after the handover is completed.

Furthermore, the transfer device according to the present invention is characterized in that the identifier is a sequence number for each packet, and the processing efficiency of the transfer device can be improved by giving a simple identifier.

  Furthermore, the transfer device according to the present invention is characterized in that the identifier is a value calculated from a portion excluding the IP header of the packet, and the assigned identifier can be calculated from the header of the packet. It is not necessary to store the data in the storage area, and the use efficiency of the storage area can be improved.

  As described above, according to the present invention, it is possible to reduce the packet loss when the mobile terminal is unexpectedly disconnected from the link or handed over. In addition, an application of a communication terminal that is a transmission source at the time of handover that is completed in a short period can continue communication.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

(Embodiment 1)
The connection management system in Embodiment 1 of this invention is demonstrated using FIGS. 1-5.

FIG. 2 is a diagram showing an IP network configuration for carrying out the packet transfer method according to the present invention, and access formed by the network 100, the home agent device 10, the access router devices 101 and 102, and the access router devices 101 and 102. The network 110 and 120, the mobile terminal 20, and the communication terminal 30 which communicates with this mobile terminal 20 are comprised. The home agent device 10 corresponds to the transfer device according to the present invention.
Next, the operation of the home agent device 10 according to the present embodiment will be described with reference to the drawings.

  FIG. 1 is a configuration diagram of a home agent device 10, and a lower layer processing unit 11 that performs physical layer processing and data link layer processing, an IP processing unit 12 that performs network layer processing, and a packet that performs transfer processing including mobile IP processing Transfer unit 19, transfer control unit 13 for controlling packet transfer unit 19, transfer packet buffer 14 for temporarily storing transfer packets, transfer packet storage unit 18 for formal storage, and ICMP for storing received ICMP destination unreachable messages The buffer 15 includes a binding cache 17 in which the correspondence between the home address and care-of address of the mobile terminal whose location is managed, a timer 21 that counts various times, and a packet determination unit 16 that specifies a packet to be stored. The lower layer processing unit 11 and the IP processing unit 12 correspond to the receiving unit according to the present invention, the transfer packet buffer 14 and the transfer packet storage unit 18 correspond to the packet storage unit according to the present invention, and the ICMP. Buffer 15 corresponds to a message storage unit according to the present invention. In particular, the transfer packet buffer 14 corresponds to a high-speed access memory according to the present invention, and the transfer packet storage unit 18 corresponds to a storage unit having a larger storage capacity than the high-speed access memory according to the present invention.

  The basic operation of the home agent device 10 configured as described above will be described below with reference to the flowcharts shown in FIGS.

FIG. 5A shows processing when a packet to the mobile terminal is received. In FIG. 5A, when the packet transfer unit 19 receives a packet addressed to the mobile terminal 20 via the lower layer processing unit 11 and the IP processing unit 12 by proxy (Step S10), the binding cache managed by the mobile IP protocol is used. The care-of address is searched with reference to FIG. The packet transfer unit 19 adds a tunnel header having the destination IP address as the care-of address and the source IP address as its own address to the packet, and transmits the packet via the IP processing unit 12 and the lower layer processing unit 11 (step S11). ). At this time, the transfer control unit 13 temporarily stores the transferred packet in the transfer packet buffer 14 (step S12).

  The packet to be stored may be a transfer packet to the mobile terminal 20 (with a tunnel header added) or a proxy received packet (with no tunnel header added). In the former case, the packet buffer transferred and transmitted can be stored as it is, which is efficient. In the latter case, the storage area for 40 octets of the tunnel header can be saved, and more packets can be stored.

  Next, FIG. 5B shows processing when an ICMP destination unreachable message is received. In FIG. 5B, when the packet transfer unit 19 receives the ICMP destination unreachable message (step S20), it determines whether the packet is for the packet transferred to the mobile terminal 20 (step S21). Performs normal ICMP message processing (step S22). If applicable, the transfer control unit 13 stores the received ICMP destination unreachable message in the ICMP buffer 15 (step S23).

  Next, the packet discriminating unit 16 discriminates whether or not the packet temporarily stored from the packet temporarily stored in the transfer packet buffer 14 (step S24), and receives the packet to be officially stored and the proxy reception thereafter. Formal storage is started in the transfer packet storage unit 18 including the packet (step S25).

  Here, the packets to be officially stored may be all temporarily stored packets or packets that have been scrutinized by the packet discrimination unit 16. The scrutiny by the packet discrimination unit 16 can be performed by adding an identifier to the transfer packet. That is, by comparing and discriminating the identifier assigned to the transfer packet and the identifier of the transfer message included in the received ICMP destination unreachable message, it is possible to correctly identify the packet for starting formal storage. For example, when the temporary storage packet after the identifier matches is officially stored, the mobile terminal 20 does not receive duplicate packets after the handover.

  For example, a packet ID destination option header 50 using a destination option header supported by the standard IPv6 protocol shown in FIG. 6 is newly added at the time of tunnel transfer, and a counter value obtained by counting the number of temporarily stored packets or a transfer packet A hash value calculated from a part of the packet ID field 51 is described and transferred. Since the ICMP destination unreachable message includes the contents of the original packet until the entire message reaches 576 octets, the ICMP destination unreachable message for the transfer packet at this time includes the ID destination option header 50 added earlier. Is included. Therefore, the packet determination unit 16 can identify a packet to be officially stored by comparing it with the value of the packet ID field 51 of the temporarily stored transfer packet. The identifier may be described by newly providing an extension header as described above, or may be described by extending a part of an existing header.

  Here, when calculating the hash value from a part of the transfer packet, it is possible to specify the packet by using data of 528 octets from the head of the header (or all headers and payload when 528 octets are not reached). Possible identifiers can be generated. The calculation basis of 528 octets is obtained by subtracting the header (IPv6 header and ICMPv6 header) size 48 octets of the ICMP destination unreachable message from the maximum size 576 octets of the ICMP destination unreachable message.

Furthermore, by including at least the TCP or UDP header in the calculation target, an identifier that can accurately identify the packet can be obtained by a parameter such as a checksum included in the header.

  Here, when a packet without a tunnel header is temporarily stored, an extension header or an extension field in which an identifier is described is not stored together with the stored packet. Therefore, it is necessary to perform buffer management so that the identifier is stored together with the temporarily stored packet.

  Furthermore, when a hash value is calculated from a part of the transfer packet, it is not necessary to provide a new header or extension field such as the packet ID destination option 50 in the transfer packet. That is, the hash value is not calculated at the time of packet transfer, but only when an ICMP destination unreachable message is received and compared with a temporarily stored packet, a new header or extension field becomes unnecessary.

  Note that the storage unit for storing packets is not limited to this embodiment, and temporary storage and formal storage can be stored in the same storage device. In the case of the present embodiment, temporarily stored packets that require a processing amount per unit time are stored in a memory that has a small area but can be accessed at high speed, and officially stored packets that can be accessed at a medium speed but stored in a memory having a large area is doing. By changing the storage area according to the nature of the packet to be stored in this way, it is possible to improve the efficiency of transfer processing of the home agent device.

  Next, FIG. 5C shows processing when a binding update message is received from the mobile terminal. In FIG. 5C, when the packet transfer unit 19 receives the binding update message from the mobile terminal (step S30), the binding process is performed according to the mobile IP protocol to update the binding cache 17, and the binding ACK message is transmitted to the mobile terminal 20. (Step S31). Then, the transfer control unit 13 checks whether or not the packet addressed to the mobile terminal 20 is stored in the transfer packet storage unit 18. If the packet is stored, the transfer control unit 13 instructs the packet transfer unit 19 to instruct the mobile terminal 20. Is started (step S32). If the transfer control unit 13 receives a binding update message from the mobile terminal 20 before receiving the ICMP destination unreachable message, that is, confirms the handover of the mobile terminal 20 before performing formal storage, The packet addressed to the mobile terminal 20 stored in the packet buffer 14 is transferred.

  Next, FIG.5 (d) has shown the process after transferring the packet to a mobile terminal. In FIG. 5D, the transfer control unit 13 cannot receive the binding update message from the mobile terminal 20, and a predetermined time (usually 15 seconds) after starting formal storage in step S25 of FIG. 5B. ) Elapses, that is, when the timer 21 times out (step S40), an ICMP destination unreachable message for the proxy received packet is generated based on the ICMP destination unreachable message stored in the ICMP buffer 15. At this time, the packet addressed to the mobile terminal 30 that has been officially stored in the transfer packet storage unit 18 is discarded (step S42). The predetermined time of 15 seconds at this time also takes into account that the mobile terminal 20 is handed over to a different network system, and means a general time required for the authentication process in that case. The predetermined time may be calculated based on the TCP retransmission timer value. It is also possible to set the time when 39 seconds have passed with reference to the start time of temporary storage of the packet. The breakdown of 39 seconds will be described with reference to FIG.

FIG. 8 shows an operation of setting the state of the neighbor cache entry managed by the access router apparatus 101 based on the IETF RFC 2461 standard. The access router apparatus 101 manages the correspondence between the IP address of the mobile terminal 20 and the link layer address using the neighbor cache, and can confirm the existence of the mobile terminal 20 by the presence of the neighbor cache entry. Each neighbor cache entry is periodically checked for existence. At this time, the state transition diagram shown in FIG. 8 is applied as a standard specification. Hereinafter, the contents of the state transition will be described.

  In FIG. 8, when a packet transmission request to a destination having no entry in the neighbor cache is generated, the access router apparatus 101 generates a neighbor cache entry for the destination IP address (step S220) and an indeterminate state (INCOMPLETE) (step S221).

  Next, the access router apparatus 101 transmits a neighbor search message (step S222).

  Next, if the access router apparatus 101 cannot receive the corresponding neighbor advertisement message within one second after transmission, the access router apparatus 101 retransmits the neighbor search message and transmits the message up to a total of three times. As a result, it is checked whether or not the corresponding neighborhood advertisement message has been received (step S223), and if it can be received, the entry state is set to the receivable state (REACHABLE) (step S224), and the neighborhood advertisement message is received. If the transmission packet is a relay packet, the ICMP destination unreachable message is transmitted to the packet transmission source. At this time, the relay packet is discarded (step S229).

  Next, the access router apparatus 101 transitions the entry in the receivable state in which the reachable time (REACHABLE_TIME) (normally 30 seconds) has passed to the expired state (STALE) (step S225).

  Thereafter, when a packet transmission request to the corresponding communication terminal is generated, the access router apparatus 101 transmits a packet to change the entry to a delay state (DELAY) (step S226), and a delay time (DELAY_FIRST_PROBE_TIME) (normally 5 seconds) Start the timer.

  Next, after the delay time (DELAY_FIRST_PROBE_TIME) has elapsed, the access router apparatus 101 transitions the entry to the search state (PROBE) (step S227), and sends a neighbor search message to the IP address of the entry as a retransmission time (RETRANS_TIME) ( The maximum number of searches (MAX_UNICAST_SOLICIT) (usually 3 times) is transmitted at intervals of (usually 1 second) (step S228). Then, the access router apparatus 101 transitions to a receivable state (REACHABLE) when it can receive a neighbor advertisement message as a response from the mobile terminal (step S224). The access router apparatus 101 deletes the entry when the neighbor advertisement message cannot be received even after the retransmission time (RETRANS_TIME) has elapsed with respect to transmission of the maximum number of searches (MAX_UNICAST_SOLICIT). If the transmission packet is a relay packet, an ICMP destination unreachable message is transmitted to the packet transmission source, and the transmission packet is discarded (step S229).

Here, in the access router apparatus 101, the mobile terminal 20 leaves the link at the same time as the neighbor cache entry of the mobile terminal 20 is changed to the receivable state (REACHABLE) (step S224). Further, the transfer packet addressed to the mobile terminal 20 is further transferred. May need to be transferred. This is the time when the access router apparatus 101 detects the absence of the mobile terminal 20 and maximizes the time required for transmitting the ICMP destination unreachable message to the packet transmission source. Incidentally, the shortest case is when the mobile terminal 20 does not exist on the link when the packet addressed to the mobile terminal 20 is transferred, and there is no neighboring cache entry of the mobile terminal 20.
In this case, it takes 3 seconds.

  As described above, the maximum time required for the access router apparatus 101 to detect the absence of the mobile terminal 20 and transmit the ICMP destination unreachable message is 38 seconds, and packet transmission between the transfer apparatus 10 and the access router apparatus 101 is performed. Estimating the delay as 1 second at most would be 39 seconds. Note that the packet transmission delay between the transfer device 10 and the access router device 101 is not limited to 1 second, but is determined as appropriate according to the status of the communication system. It may be determined automatically. Further, the time required to detect the absence of the mobile terminal 20 is not limited to 38 seconds, and depends on parameter values (DELAY_FIRST_PROBE_TIME, RETRANS_TIME, MAX_UNICAST_SOLICIT, etc.) related to the state transition of the neighbor cache entry taken by the access router apparatus 101. It may take a value other than 38 seconds. In general, by setting the parameter value small, measures are often taken to shorten the absence detection time of the mobile terminal 20 and improve the processing efficiency.

  Further, by giving a time stamp to a packet to be temporarily stored, it is possible to quickly and accurately detect a packet that has passed 39 seconds from the temporary storage and delete it from the buffer, thereby increasing the buffer utilization efficiency.

  In the above description, when a predetermined time has elapsed since the home agent device started formal saving, an ICMP destination unreachable message is transmitted to the communication terminal 30 and a packet addressed to the mobile terminal 20 is discarded. However, the same processing may be started when the number of stored packets or the total packet size after starting formal storage (step S25) reaches a predetermined value. This predetermined value is determined from the correlation between the number of terminals 20 accommodated by the home agent device 10 and the allocated storage area.

  Further, the ICMP unreachable message transmitted to the packet transmission source may be for the packet stored in the transfer packet buffer earliest, or the only ICMP unreachable message received from the access router apparatus 101 indicates It may be for a packet of. In the former case, since the leading position of a packet that has not been received can be obtained, it is possible to designate the next transmission start packet position. Then, it is possible to start playback of the storage-related video / music stream application from the point where the mobile terminal 20 was previously stopped when the mobile terminal 20 was reconnected. In the latter case, it is based on a conventional standard method, and guarantees compatibility with an application that assumes operation by the conventional method.

  As described above, the home agent device 10 uses the ICMP destination unreachable message returned by the access router device 101 when the mobile terminal is disconnected from the link and packet delivery is impossible. It is possible to start buffering of a packet addressed to a mobile terminal without explicitly performing notification. Furthermore, it conceals that the mobile terminal is disconnected from the link and becomes unreachable from the communication terminal that is communicating with the mobile terminal, and improves communication efficiency at the time of handover that is completed in a short period of time. is there.

  Next, the operation of the access router apparatus 101 of this embodiment will be described using the drawings.

FIG. 9 is a diagram showing the configuration of the access router apparatus 101. In FIG. 9, the lower layer processing unit 103 performs physical layer processing and data link layer processing, the IP processing unit 104 performs network layer processing, and the connection management unit 105 displays the connection state of the mobile terminal as a lower level. Management is based on information from the layer processing unit 103, the ICMP transmission processing unit 106 generates an ICMP message, and the neighbor cache 107 stores address information such as connected mobile terminals and other routers. It is to hold.

  Next, the operation of the access router apparatus 101 configured as described above will be described below with reference to FIG.

  FIG. 10 is a flowchart for explaining the operation when the mobile terminal moves during packet transfer to the mobile terminal.

  First, when the connection management unit 105 detects that the mobile terminal 20 is absent from the frame information from the lower layer processing unit 103 (step S61), the current time is recorded in the neighborhood cache 107 (step S62).

  Next, as a result of the processing shown in FIG. 8, the IP processing unit 104 instructs the ICMP transmission processing unit 106 to transmit an ICMP destination unreachable message in step S228. In response, the ICMP transmission processing unit 106 requests the connection management unit 105 for a detection time at which the absence of the mobile terminal 20 is detected (step S63).

  Next, the connection management unit 105 notifies the ICMP transmission processing unit 106 of this detection time (step S64). In response to this, the ICMP transmission processing unit 106 generates an ICMP destination unreachable message (step S65), calculates an elapsed time from the current time and the detection time (step S66), and uses the time as the ICMP destination shown in FIG. It is described in the unreachable message elapsed time field 71 and transmitted to the transmission source of the packet (step S67), and the process is terminated.

  Thereby, when the transmission packet from the communication terminal 30 is transmitted via the home agent device 10, the access router device 101 can notify the home agent device 10 of the period during which the access router device 101 could not relay to the mobile terminal.

  When the home agent device 10 assigns an identifier such as a sequence number to the transfer packet, the packet identifier when the connection management unit 105 detects the absence of the mobile terminal 20 (step S61) is stored in the neighbor cache 107. The identifier may be recorded and the identifier may be described in the elapsed time field 71 of the ICMP destination unreachable message.

  A method in which a packet transmitted from the communication terminal 30 to the mobile terminal 20 via the home agent apparatus 10 and the access router apparatuses 101 and 102 described above is transferred with a small loss at the time of handover of the mobile terminal 20 will be described below. To do.

  In the present embodiment, the case where the mobile terminal 20 moves from the state connected to the access network 110 accommodated in the access router apparatus 101 and connects to the access network 120 accommodated in the access router apparatus 102 will be described. To do. At this time, since the mobile terminal 20 is accommodated in the home agent device 10 using the mobile IP protocol, the change of the IP address accompanying the movement can be concealed from the communication terminal 30 which is the communication partner.

  FIG. 3 is a sequence diagram showing a transfer method according to the embodiment of the present invention.

  In FIG. 3, the communication terminal 30 transmits a packet to the home address of the mobile terminal 20 (steps S100 and S102), and the home agent device 10 receives the proxy.

  Next, the home agent device 10 tunnels this packet to the care-of address of the mobile terminal 20 and temporarily stores it at the same time (steps S101 and S103).

  Next, if the mobile terminal 20 is disconnected from the link and the tunneled packet cannot be reached (step S102), the access router apparatus 101 transmits an ICMP destination unreachable message to the home agent apparatus 10 that is the transmission source (step S102). Step S104).

  Next, when receiving the ICMP destination unreachable message, the home agent device 10 officially saves the temporarily stored packet and saves the received ICMP destination unreachable message (step S105). The home agent device 10 then officially stores the packets received by proxy from the communication terminal 30 thereafter (step S106). When the home agent device 10 adds the above-described identifier to the transferred packet, the packet up to where is transferred from the identifier of the packet that has not been transferred included in the ICMP destination unreachable message, and the packet from where Since the packet is not transferred, only the packets after the packet that has not been transferred among the temporarily stored packets can be officially stored. Alternatively, when the home agent apparatus 10 includes the above-described elapsed time information in the ICMP destination unreachable message, the home agent apparatus 10 only officially saves the packet that has been passed by the elapsed time notified from the time when the ICMP destination unreachable message was received. You can also go to save.

  Next, when the mobile terminal 20 completes the handover and becomes able to transmit and receive IP packets, it transmits a binding update (Binding / Update) message to the home agent device 10 according to the mobile IP protocol (step S107). In response to this, the home agent device 10 performs a binding process according to the mobile IP protocol, and transmits a binding acknowledge (Binding Ack) message to the mobile terminal 20 (step S108). In addition, transfer of the packet addressed to the mobile terminal 20 officially stored at this time is started to the mobile terminal 20 (steps S109 and S110).

  After the transfer of the stored packet is completed, the packet transmitted from the communication terminal is transferred to the mobile terminal 20 via the access router device 2 (step S111).

  FIG. 7 is a diagram illustrating a transfer method when a binding update message is received from the mobile terminal 20 before receiving an ICMP destination unreachable message from the access router apparatus 101.

  In FIG. 7, steps S100 to S103 are the same as the operations described in FIG. At this time, when the home agent device 10 receives the binding update message from the mobile terminal 20 (step S107), the home agent device 10 receives the binding update message, performs a binding process according to the mobile IP protocol, and performs a binding acknowledge message. Is transmitted to the mobile terminal 20 (step S108). At this time, the temporarily stored packet addressed to the mobile terminal 20 is started to be transferred to the mobile terminal 20 (steps S109 and S110).

  As described above, since the home agent device 10 stores packets that are not transferred at the time of handover without a request from the mobile terminal, when the mobile terminal 20 is suddenly disconnected from the network and then reconnected. In addition, it is possible to continue reception without packet loss. Further, since the communication terminal 30 does not receive the ICMP destination unreachable message immediately after the mobile terminal is handed over, the opportunity to continue the session with the mobile terminal increases.

  FIG. 4 is a diagram illustrating a transfer method when the binding update message from the mobile terminal 20 cannot be received.

  In FIG. 4, steps S100 to S106 are the same as the operations described in FIG. At this time, if the home agent device 10 cannot receive the binding update message from the mobile terminal 20 even after waiting for a predetermined time, the ICMP destination cannot be reached for the proxy received packet based on the saved ICMP destination unreachable message. A message is generated and transmitted to the communication terminal 30 (step S120). At the same time, the packet addressed to the mobile terminal 30 that has been officially saved is discarded (step S121).

  As a result, when the mobile terminal 20 moves out of the communication range, the home agent device 10 can delete the stored packet, so that it is possible to respond to a new packet accumulation request.

  As described above, even when the mobile terminal is unexpectedly disconnected from the link or when it is handed over, the home agent device always saves the packet addressed to the mobile terminal for a necessary period, and the mobile terminal can communicate again. Since the packet is transferred from time to time, packet loss addressed to the mobile terminal can be reduced. Also, at the time of handover that is completed in a short period, the ICMP destination unreachable message is not transmitted to the communication terminal that is the transmission source, so the application of the communication terminal assumes that the mobile terminal is continuously connected, and thus continues communication. Can do.

  The present invention is useful for packet transfer in a mobile IP network, and is suitable for a mobile terminal to perform handover while implementing the mobile IP protocol.

The figure which shows the structure of the home agent apparatus in Embodiment 1 of this invention. The figure which shows the structure of the system which concerns on Embodiment 1 of this invention. The figure which shows the 1st sequence of the packet transfer in Embodiment 1 of this invention The figure which shows the 2nd sequence of the packet transfer in Embodiment 1 of this invention. The flowchart which shows operation | movement of the home agent apparatus in Embodiment 1 of this invention. The figure which shows the format of the packet ID destination option header in Embodiment 1 of this invention The figure which shows the 3rd sequence of the packet transfer in Embodiment 1 of this invention. The flowchart which shows operation | movement of the access router apparatus in Embodiment 1 of this invention. The figure which shows the structure of the access router apparatus in Embodiment 1 of this invention. The flowchart which shows operation | movement of the access router apparatus in Embodiment 1 of this invention. The figure which shows the format of the ICMP destination unreachable message in Embodiment 1 of this invention Flow chart showing operation of conventional home agent device A diagram showing a conventional packet transfer sequence

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Home agent apparatus 20 Communication terminal 30 Communication apparatus 101,102 Access router apparatus 100 Network 110,120 Access network 11 Lower layer processing part 12 IP processing part 13 Transfer control part 14 Transfer packet buffer 15 ICMP buffer 20 Packet discrimination part

Claims (14)

A step in which a transfer device on the IP network receives a packet addressed to a mobile terminal, transfers the packet, and stores the packet;
Transferring the stored packet to the mobile terminal when the transfer device receives a packet transfer request from the mobile terminal within a predetermined time, and discarding the stored packet when the packet is not received. And
The transfer device initially stores the packet in the high-speed access memory, and stores the packet addressed to the mobile terminal having a larger storage capacity than the high-speed access memory when receiving a non-delivery notification for the transferred packet. packet transfer method to save the part. A step in which a transfer device on the IP network receives a packet addressed to a mobile terminal, transfers the packet, and stores the packet;
The transfer device storing the non-delivery notice when receiving the non-delivery notice for the transferred packet;
When the transfer device receives a packet transfer request from the mobile terminal within a predetermined time from the start of storage, the transfer device transfers the stored packet addressed to the mobile terminal to the mobile terminal and fails to deliver the packet. sends said non-delivery notification to the transmission source mobile terminal addressed packets, a step discards the mobile terminal addressed packet stored based on the notification,
A packet transfer method comprising: A step in which a transfer device on the IP network receives a packet addressed to a mobile terminal, transfers the packet, and stores the packet;
The transfer device storing the non-delivery notice when receiving the non-delivery notice for the transferred packet;
If the quantity of packets the transfer device is saved when receiving a packet transfer request from the mobile terminal before a predetermined amount or more, which forwards the mobile terminal addressed packets stored in the mobile terminal did not receive to transmit a non-delivery notification to the transmission source of the mobile terminal addressed packet based on the non-delivery notification, and step discards the mobile terminal addressed packets stored,
A packet transfer method comprising: A step in which a transfer device on the IP network receives a packet addressed to a mobile terminal, transfers the packet, and stores the packet;
Transferring the stored packet to the mobile terminal when the transfer device receives a packet transfer request from the mobile terminal within a predetermined time, and discarding the stored packet when not received;
Adding an identifier to a packet transferred by the transfer device to the mobile terminal;
Discarded if it receives a non-delivery notification, among the saved packets, the packets stored prior identifier and the same packets of the mobile terminal addressed packet included in the non-delivery notification for packet said transfer device has transferred Steps ,
A packet transfer method comprising: A step in which the transfer device on the IP network receives the packet addressed to the mobile terminal, transfers the packet, and temporarily stores the packet;
A formal storage of the temporarily stored packet and a packet received by proxy after receiving the non-delivery notification when receiving the non-delivery notification for the packet transferred by the transfer device from the access router device;
When the transfer device receives a packet transfer request from the mobile terminal, transferring the officially stored packet to the mobile terminal;
A packet transfer method comprising: The packet transfer method according to claim 4 , wherein the identifier is a sequence number for each packet. The packet transfer method according to claim 4 , wherein the identifier is a value calculated from a portion excluding the IP header of the packet. A packet forwarding unit for forwarding packets addressed to the mobile terminal;
A packet storage unit for storing the packet;
Receiving a packet addressed to the mobile terminal by proxy and receiving a packet transfer request from the mobile terminal;
When a proxy reception notification is received from the reception unit, the received packets are stored in a packet storage unit, and a packet transfer request reception notification from the reception unit is received, and the packet storage unit receives A transfer control unit for instructing the packet transfer unit to transfer the stored packet to the mobile terminal;
A timer that counts the time until the packet stored in the packet storage unit is discarded;
Comprising
If the transfer control unit does not receive a packet transfer request before receiving notification of the elapse of time from the timer to the discard, the stored packet is discarded,
The transfer control unit accumulates in the high-speed access memory at the initial stage of proxy reception, and stores a larger storage capacity than the high-speed access memory when receiving from the reception unit a reception notification of non-delivery notification for the transferred packet. transfer device for storing the parts. A packet forwarding unit for forwarding packets addressed to the mobile terminal;
A packet storage unit for storing the packet;
Receiving a packet addressed to the mobile terminal by proxy and receiving a packet transfer request from the mobile terminal;
When a proxy reception notification is received from the reception unit, the received packets are stored in a packet storage unit, and a packet transfer request reception notification from the reception unit is received, and the packet storage unit receives A transfer control unit for instructing the packet transfer unit to transfer the stored packet to the mobile terminal;
A timer that counts the time until the packet stored in the packet storage unit is discarded;
A message storage unit for storing the received delivery failure notification ;
Comprising
The transfer control unit, when receiving the non-delivery notice to the transferred packet, before saving the delivery failure notice to the message memory, receiving notification of lapse of time from the timer to the disposal, packet transfer If not receiving the request, on the basis of the non-delivery notification sends a non-delivery notification to the transmission source of the mobile terminal addressed packets, forwards discards mobile terminal addressed packets saved from the packet storage unit device. A packet forwarding unit for forwarding packets addressed to the mobile terminal;
A packet storage unit for storing the packet;
Receiving a packet addressed to the mobile terminal by proxy and receiving a packet transfer request from the mobile terminal;
When a proxy reception notification is received from the reception unit, the received packets are stored in a packet storage unit, and a packet transfer request reception notification from the reception unit is received, and the packet storage unit receives A transfer control unit for instructing the packet transfer unit to transfer the stored packet to the mobile terminal;
A message storage unit for storing the received delivery failure notification ;
Comprising
The transfer control unit, when receiving the non-delivery notice to the transferred packet, the the non-delivery notification is stored in the message memory, before the amount of packets stored in the packet storage unit becomes a predetermined amount or more if it does not receive a packet transfer request from the mobile terminal, the based on the non-delivery notification sends a non-delivery notification to the transmission source of the mobile terminal addressed packet, the mobile terminal addressed packets saved from the packet storage unit discard transfer apparatus. A packet forwarding unit for forwarding packets addressed to the mobile terminal;
A packet storage unit for storing the packet;
Receiving a packet addressed to the mobile terminal by proxy and receiving a packet transfer request from the mobile terminal;
When a proxy reception notification is received from the reception unit, the received packets are stored in a packet storage unit, and a packet transfer request reception notification from the reception unit is received, and the packet storage unit receives A transfer control unit for instructing the packet transfer unit to transfer the stored packet to the mobile terminal;
Comprising
The packet transfer unit adds an identifier to the packet addressed to the mobile terminal received by the reception unit and transmits the packet,
A packet discriminating unit for discarding a packet stored before the same packet as the identifier of the packet addressed to the mobile terminal included in the non-delivery notice among the packets stored in the packet storage unit;
When said transfer control unit has received a notification of receiving the non-delivery notification from the receiving unit, forwards that instructs the determination process of discarding packets stored in the packet storage unit to the packet determining section apparatus . A packet forwarding unit for forwarding packets addressed to the mobile terminal;
A packet storage unit for storing packets addressed to the mobile terminal;
A receiving unit for proxy reception of a packet addressed to the mobile terminal;
A transfer control unit;
Comprising
The transfer control unit
When the reception unit receives a packet addressed to a mobile terminal by proxy, the received packet is transferred by the packet transfer unit, and the received packet is temporarily stored in the packet storage unit,
When a delivery failure notification for the transferred packet is received from the access router device, the temporarily stored packet and a packet received by the reception unit after receiving the delivery failure notification are officially stored in the packet storage unit. Save and
A transfer apparatus for transferring the officially stored packet to the mobile terminal by the packet transfer unit when receiving a packet transfer request from the mobile terminal . The transfer apparatus according to claim 11 , wherein the identifier is a sequence number for each packet. The transfer apparatus according to claim 11 , wherein the identifier is a value calculated from a portion excluding an IP header of a packet.

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