JP2007013511A - Packet communication system and packet relaying apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a packet communication system capable of executing a service with high quality even on the occurrence of a delay or missing in a communication packet. <P>SOLUTION: A packet switching apparatus 110 duplicates a communication packet transmitted to the packet switching apparatus 120 and transmits the duplicate packets to packet switching networks 130, 140 respectively. When the communication packet coming from a pre-stage of the same packet switching network is not received yet, packet relaying apparatuses 131-1 to 131-n, 141-1 to 141-n transfer the unreceived packet to a packet relaying apparatus corresponding to the post-stage and the other packet switching network, when the communication packet coming from the pre-stage is already received, the packet relaying apparatuses 131-1 to 131-n, 141-1 to 141-n abort the received packet. When the communication packet coming from a packet relaying apparatus corresponding to the other packet switching network is not received yet, the packet relaying apparatuses 131-1 to 131-n, 141-1 to 141-n transfer the unreceived packet to only the post-stage, and when the communication packet coming from the packet relaying apparatus corresponding to the other packet switching network, the packet relaying apparatuses 131-1 to 131-n, 141-1 to 141-n abort the received packet. Thus, even on the occurrence of a fault or the like on a communication path, the post-stage of the faulty path can execute normal communication. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a packet communication system that performs multiplex communication of identical communication packets and a packet relay device used therefor.

  Conventionally, a packet switching system is known as a kind of communication system. In a communication network that employs a packet switching method, an arbitrary line is used in units of communication packets, so that the line is not exclusively used by the transmission side and the reception side, and therefore the use efficiency of the communication line can be improved. .

  However, in a packet switching network, communication packets may be delayed or lost due to network congestion or the like, which may degrade service quality. For example, in an image communication service, a frame of a moving image (an image for one frame) may be lost due to packet loss, which may deteriorate image quality. In addition, in a communication service such as a transaction processing service that does not allow communication data to be lost, if a communication packet is lost, the communication packet must be retransmitted, resulting in a decrease in communication response.

  In addition, for example, when a communication line connecting the packet switching network and the communication device is disconnected, the communication packet may not reach the destination due to the occurrence of a communication failure. In such a case, the communication service itself cannot be provided. Conventionally, the communication line is made redundant and the path is automatically switched when a failure occurs, thereby speeding up the recovery from the communication failure. However, since such a method cannot prevent the occurrence of a communication failure itself, the communication service must be interrupted from the time of the occurrence of the failure until the failure recovery function is automatically activated. The

As a technique for preventing delay / loss of communication packets, for example, a technique described in Patent Document 1 below is known. In this technique, a copy of a communication packet is generated by an input packet switch of a packet switching network (see paragraph 0030 of the same patent document), and the original communication packet and the copy packet reach the destination via different communication paths. Header information (routing tag) is set in (see paragraphs 0034 to 0036 of the same document), thereby suppressing packet delay and loss. Further, the output packet switch of the packet switching network determines the identity of the copy packet based on the information content of the communication packet, and discards the copy packet having the same content (see paragraphs 0032 and 0036 of the patent document). .
Japanese Patent No. 3083133

  However, the technique of Patent Document 1 has a drawback that it cannot cope with a service interruption due to a communication failure such as disconnection in a communication line connecting a packet switching network and a communication device.

  In addition, since the routing tag must be individually set so that the original communication packet and the copy packet reach the destination via different paths, there is a disadvantage that the work load for route determination is large.

  Moreover, in the technique of Patent Document 1, since the identity of the copy packet is determined based on the information content of the communication packet, the processing load for such identity determination increases, and the output packet switch is expensive. There is also a drawback of becoming.

  An object of the present invention is to provide a packet communication system and a packet communication apparatus that can provide a high-quality service even when a communication packet is delayed or lost or a communication failure occurs at low cost.

  (1) The first invention relates to a packet communication system in which a transmission device and a reception device are connected via first and second communication networks.

  The first communication network includes a plurality of first relay devices, the second communication network includes a plurality of second relay devices connected to the corresponding first relay device, and the transmission device transmits two identical communication packets. A means for generating and outputting to the first and second relay devices in the first stage, and the first relay device receiving the communication packet received from the transmitting device or the preceding first relay device or the corresponding second relay device; If the received communication packet has not been received, the first network transfer means for transferring to the first relay device or receiving device in the subsequent stage and discarding if the communication packet has already been received, First inter-network transfer means for transferring to a second relay device corresponding to a case where a communication packet received from the first relay device has not been received, wherein the second relay device is a transmitting device or a second relay in the preceding stage. The communication received from the device A second network that forwards the packet or the communication packet received from the corresponding first relay device to the second relay device or receiving device in the subsequent stage and discards the communication packet if the communication packet has already been received An internal transfer means, and a second inter-network transfer means for transferring to the corresponding first relay apparatus when a communication packet received from the transmitting apparatus or the preceding second relay apparatus has not been received. If the communication packet received from the first and second relay devices at the final stage has already been received, the communication packet is discarded.

  (2) The second invention relates to a packet relay device for constructing a plurality of communication networks each for communication connection between a transmission device and a reception device.

  And when the communication packet received from the transmitting device or the preceding relay device or the communication packet received from the corresponding relay device of another communication network is not received, it is transferred to the succeeding relay device or receiving device, and If the communication packet has already been received, discard it in the network and forward it to the corresponding relay device in another communication network if the communication packet received from the transmitter or the preceding relay device has not been received. Network transfer means.

  According to the first and second inventions, the same communication packet transmitted from the transmission device to the first and second communication networks is sent to the transmission device while being exchanged between corresponding relay devices in these communication networks. Even if a failure occurs in the communication line, the service is not easily interrupted, and it is not necessary to make a routing setting so that the same communication packet reaches the destination via another route, so the processing is simple.

  Embodiments of the present invention will be described below with reference to the drawings. In the drawings, the size, shape, and arrangement relationship of each component are shown only schematically to the extent that the present invention can be understood, and the numerical conditions described below are merely examples. .

First Embodiment A first embodiment of the present invention will be described with reference to FIGS.

  FIG. 1 is a conceptual diagram schematically showing the overall configuration of a communication system according to this embodiment. As shown in FIG. 1, the communication system 100 of this embodiment includes two packet switching apparatuses 110 and 120 and two systems of packet switching networks 130 and 140.

  Each of the packet switching apparatuses 110 and 120 implements a unique function and service, and requests the other packet switching apparatus to provide the function and service. The internal structure of the packet switching devices 110 and 120 will be described later with reference to FIG.

  The packet switching network 130 is connected to the packet switching apparatus 110 via the interface IF11 and is connected to the packet switching apparatus 120 via the interface IF21. Similarly, the packet switching network 140 is connected to the packet switching apparatus 110 via the interface IF12 and is connected to the packet switching apparatus 120 via the interface IF22. The packet switching network 130 includes n packet relay apparatuses 131-1 to 131-n. Similarly, the packet switching network 140 includes n packet relay apparatuses 141-1 to 141-n.

  FIG. 2 is a block diagram schematically showing the internal configuration of the packet switching devices 110 and 120 according to this embodiment.

  As shown in FIG. 2, the packet switching apparatus 110 of this embodiment includes an application function unit 210, a packet transmission / reception function unit 220, and packet input / output units 230 and 240.

  The application function unit 210 implements functions and services unique to the packet switching apparatus 110. The application function unit 210 receives data received from other packet switching devices via the packet transmission / reception function unit 220. Further, the application function unit 210 passes data to be transmitted to other packet switching devices, a destination address, and the like to the packet transmission / reception function unit 220.

  The packet transmission / reception function unit 220 generates a communication packet using the data and the destination address received from the application function unit 210. The packet transmission / reception function unit 220 has a function of transmitting the same communication packet one by one (hereinafter referred to as “single transmission”) and a function of transmitting two each (hereinafter referred to as “double transmission”). As will be described later, when duplex transmission is performed, the packet transmission / reception function unit 220 stores identification information indicating a duplex communication and a sequence number in a communication packet, and packet input / output units 230 and 240. Pass to both. Further, the packet transmission / reception function unit 220 receives the packets received by the packet input / output units 230 and 240. As will be described later, when receiving two identical communication packets, the packet transmission / reception function unit 220 discards one of them. Further, the packet transmission / reception function unit 220 includes a hold buffer 221 and a hold timer 222. The hold buffer 221 can temporarily store one communication packet for each transmission source address of the received communication packet, and is used for rearrangement when the reception order of communication packets is reversed. The hold timer 222 is used for managing the hold time of the hold buffer 221.

  The packet input / output unit 230 transmits the communication packet received from the packet transmission / reception function unit 220 to one packet switching network 130, and passes the communication packet received from the packet switching network 130 to the packet transmission / reception function unit 220. Similarly, the packet input / output unit 240 transmits the communication packet received from the packet transmission / reception function unit 220 to the other packet switching network 140, and receives the communication packet received from the packet switching network 140 to the packet transmission / reception function unit 220. hand over.

  FIG. 3 is a block diagram schematically showing the internal configuration of the packet relay apparatuses 131-1 to 131-n and 141-1 to 141-n according to this embodiment. FIG. 3 shows only a configuration that contributes to packet transmission from the packet switching apparatus 110 to the packet switching apparatus 120 for simplification. However, FIG. 3 illustrates packet transmission from the packet switching apparatus 120 to the packet switching apparatus 110. The contributing configuration may be the same.

  As shown in FIG. 3, the packet switching apparatus of this embodiment includes an intra-network transfer function unit 310, an inter-network transfer function unit 320, packet input units 330 and 340, and packet output units 350 and 360. ing.

  The intra-network transfer function unit 310 is a communication transmitted by the upstream device (either the packet switching device 110 or the packet relay devices 131-1 to 131- (1-n), 141-1 to 141- (n-1)). A communication packet received from the packet input unit 330 and transmitted by a corresponding packet relay device (any one of the packet relay devices 131-1 to 131-n, 141-1 to 141-n) of the other packet switching network Is received from the packet input unit 340. When the intra-network transfer function unit 310 receives two identical communication packets, one of them is transferred from the packet output unit 350 to the next packet relay apparatus 131-2, and the other is discarded. Further, the intra-network transfer function unit 310 includes a hold buffer 311 and a hold timer 312. The hold buffer 311 can temporarily store one communication packet for each transmission source address of the received communication packet, and is used for rearrangement when the reception order of communication packets is reversed. The hold timer 312 is used to manage the hold time of the hold buffer 311.

  The inter-network transfer function unit 320 receives the communication packet transmitted by the packet switching device 110 from the packet input unit 330, evaluates whether the received communication packet is a double communication packet, and in the case of a double communication packet Is transferred to the packet repeater 141-1 via the packet output unit 360.

  FIG. 4 is a conceptual diagram showing a layer structure adopted in the packet communication system 100.

  As shown in FIG. 4, the layer structures of the packet switching apparatuses 110 and 120 are, from the lower layer side, Ethernet (registered trademark) layer Eth (primary Eth (P) and secondary Eth (S)), IP layer, two layers, respectively. It has a heavy communication control layer, a TCP / UDP layer, and an application layer.

  The Ethernet (registered trademark) layer corresponds to a physical layer and a data link layer of an OSI (Open Systems Interconnection) reference model, and is a layer for performing network connection between the packet switching apparatuses 110 and 120. Of the Ethernet (registered trademark) layer Eth of the packet switching apparatus 110, the primary Eth (P) corresponds to the interface IF11, and the secondary Eth (s) corresponds to the interface IF12 (see FIG. 1). Further, in the Ethernet (registered trademark) layer Eth of the packet switching device 120, the primary Eth (P) corresponds to the interface IF21, and the second (registered trademark) Re Eth (S) corresponds to the interface IF22.

  The IP layer corresponds to the lower layer of the network layer in the OSI reference model, and executes IP (Internet protocol) control.

  The dual communication control layer corresponds to the upper layer of the network layer in the OSI reference model, and is a layer responsible for controlling the dual communication according to this embodiment. That is, the duplex communication control layer adds identification information and a sequence number to a transmission packet, and performs double reception control by reading the identification information and sequence number from the received packet (described later).

  The TCP / UDP layer corresponds to the transport layer of the OSI reference model, and executes normal TCP (Transmission Control Protocol) and UDP (User Datagram Protocol).

  The application layer corresponds to the session layer, presentation layer, and application layer of the OSI reference model, and executes Telnet, DNS (Domain Name Service), HTTP (Hyper Text Transfer Protocol), FTP (File Transfer Protocol), and the like.

  The packet relay apparatuses 131-1 to 131-n and 141-1 to 141-n control corresponding to the Ethernet (registered trademark) layer Eth, the IP layer, and the duplex communication control layer in the layer structure of FIG. Only do.

  Thus, in this embodiment, since the dual communication control layer is provided between the TCP / UDP layer and the IP layer, the dual communication control can be performed without affecting the control of the TCP / UDP and the application layer. It can be carried out.

  Hereinafter, the operation of the packet communication system 100 according to this embodiment will be described by taking a case where a communication packet is transmitted from the packet switching apparatus 110 to the packet switching apparatus 120 as an example. The same applies to the case where a communication packet is transmitted from the packet switching apparatus 120 to the packet switching apparatus 110.

  FIG. 5 is a conceptual diagram for explaining the overall operation of the packet communication system 100 when duplex transmission is normally performed (when no communication packet loss or delay occurs). 6 and 7 are flowcharts for explaining the relay operation of the packet relay apparatus 131-1. 8 and 9 are flowcharts for explaining the reception operation of the packet switching apparatus 120.

  First, the operation in the case of single transmission will be described.

  When the packet switching apparatus 110 transmits a communication packet, first, a transmission request is sent from the application function unit 210 (see FIG. 2) to the packet transmission / reception function unit 220. This transmission request includes transmission data (user data) and a destination address. When receiving the transmission request, the packet transmission / reception function unit 220 determines whether the transmission is single transmission / duplex transmission. This determination can be made, for example, by registering in advance in the packet transmission / reception function unit 220 a destination address for performing double transmission.

  When performing single transmission, the packet transmission / reception function unit 220 uses the transmission data and the destination address received from the application function unit 210 to generate a communication packet in the same manner as in the past. In the case of single transmission, the above identification information and sequence number are not stored in the communication packet. The generated communication packet is sent to one of the packet input / output units 230 and 240. The packet input / output unit (230 or 240) that has received the communication packet transmits this communication packet to the corresponding packet relay device (130-1 or 140-1). Here, a case where a communication packet related to single transmission is sent from the packet input / output unit 230 to the packet relay apparatus 131-1 will be described as an example.

  The packet input unit 330 (see FIG. 3) in the packet relay apparatus 131-1 receives a communication packet from the packet switching apparatus 110. Then, the packet input unit 330 sends this communication packet to the intra-network transfer function unit 310 and the inter-network transfer function unit 320.

  When receiving the communication packet from the packet input unit 330, the intra-network transfer function unit 310 checks whether the identification information is stored in the communication packet (see step S601 in FIG. 6). Since the identification information is not stored here, the intra-network transfer function unit 310 determines that the communication packet is a communication packet related to single transmission, and instructs the packet output unit 350 to transmit the communication packet ( Step S602), and the process related to the communication packet is terminated.

  Each of the packet relay apparatuses 131-2 to 131-n transfers the communication packet received from the previous stage to the subsequent stage in the same manner as the packet relay apparatus 131-1.

  The packet input / output unit 230 (see FIG. 3) in the packet switching apparatus 120 receives a communication packet from the packet relay apparatus 131-n. Then, the packet input / output unit 230 sends the communication packet to the packet transmission / reception function unit 220.

  When receiving the communication packet, the packet transmission / reception function unit 220 checks whether the identification information is stored in the communication packet (see step S801 in FIG. 8). Here, since identification information is not stored, the packet transmission / reception function unit 220 determines that the communication packet is a communication packet related to single transmission, and notifies the application function unit 210 of reception of the communication packet ( In step S802), the processing related to the received packet is terminated.

  Next, the operation in the case of duplex transmission will be described.

  As described above, when the packet transmission / reception function unit 220 receives a transmission request from the application function unit 210 and the destination address included in the transmission request matches the address registered in the packet transmission / reception function unit 220 in advance, the packet transmission / reception function unit 220 The functional unit performs processing for double transmission.

  In this double transmission process, the packet transmission / reception function unit 220 generates a communication packet using identification information and a sequence number in addition to the transmission data and destination address received from the application function unit 210. The form of the identification information is arbitrary, and it is sufficient that the receiving side packet switching apparatus can recognize that it is duplex transmission. The sequence number is a number indicating the transmission order of communication packets transmitted to the same destination address. The initial value of the sequence number is arbitrary, but is incremented by “+1” each time a communication packet is generated. The packet transmission / reception function unit 220 temporarily stores a sequence number for each registered destination address (destination address for dual transmission). The storage location of the identification information and sequence number may be determined in correspondence with the layer structure shown in FIG. 4, for example. Further, as this sequence number, a sequence number used in TCP (Transmission Control Protocol) or RTP (Real-time Transport Protocol) may be used.

  The generated communication packet is sent to both the packet input / output units 230 and 240. Receiving the communication packet, the packet input / output units 230 and 240 respectively transmit the communication packet to the corresponding packet relay apparatuses 130-1 and 140-1 (see P1 and P2 in FIG. 5). Therefore, the same sequence number is stored in the pair of communication packets P1, P2 related to one double transmission.

  The packet input unit 330 (see FIG. 3) in the packet relay device 131-1 receives the communication packet P1 from the packet switching device 110. Then, the packet input unit 330 sends the communication packet P1 to the intra-network transfer function unit 310 and the inter-network transfer function unit 320.

  As will be described later, the intra-network transfer function unit 310 transfers the communication packet P1 to the packet relay device 141-1 in a predetermined case. Similarly, the intra-network transfer function unit 310 in the packet relay device 141-1 also transfers the communication packet P2 to the packet relay device 131-1 in a predetermined case. When the packet input unit 340 in the packet relay device 131-1 receives the communication packet P2 from the packet relay device 141-1, the packet input unit 340 sends the communication packet P2 to the intra-network transfer function unit 310.

  When receiving the communication packet P1 or P2 from the packet input unit 330 or 340, the intra-network transfer function unit 310 checks whether or not identification information is stored in the communication packet (see step S601 in FIG. 6). Since the identification information is stored here, the intra-network transfer function unit 310 determines that the received packet is a communication packet related to duplex transmission, and compares the sequence number of the received packet with an expected value. (Refer to step S603). The intra-network transfer function unit 310 stores the addresses of the packet switching apparatuses 110 and 120 that can perform double transmission, and for each address, the sequence number (expectation) of the communication packet to be received next. Value) is temporarily saved. When the packet switching apparatus 110 is powered on, the expected value corresponding to each address is set to an initial value. When the sequence number of the received packet matches the expected value, the intra-network transfer function unit 310 increments the expected value by “+1” (see step S604) and instructs the packet output unit 350 to transmit the communication packet. (Refer to step S605).

  Subsequently, the intra-network transfer function unit 310 checks the reservation buffer 311 (see step S606). If no communication packet is stored in the hold buffer 311, the intra-network transfer function unit 310 ends the process related to the received packet. On the other hand, when it is determined in step S606 that the communication packet is stored in the hold buffer 311, the intra-network transfer function unit 310 compares the sequence number of the hold packet with the sequence number of the received packet (P1 or P2). (Refer to step S607).

  When these sequence numbers are consecutive, the intra-network transfer function unit 310 instructs the packet output unit 350 to transfer the communication packet (hold packet) stored in the hold buffer 311 (see step S608).

  Further, the intra-network transfer function unit 310 increments the expected value of the sequence number by “+1” (see step S609), stops the hold timer 312 and releases the hold buffer 311 (see steps S610 and S611). Then, the process related to the received packet is terminated. By such processing, when two consecutive packets are received in the reverse order, the order can be corrected and transferred to the next stage device (here, the packet relay device 311-2).

  On the other hand, if the sequence numbers are not consecutive in step S607, the hold timer 312 is restarted, and the process related to the received packet is terminated. By this process, the holding time of the holding buffer 311 is extended.

  When the sequence number does not match the expected value in step S603, the intra-network transfer function unit 310 checks whether or not the received communication packet is the same as the already received communication packet (see step S701 in FIG. 7). ). For example, when the sequence number is greater than or equal to the initial value and smaller than the expected value stored therein, the communication packet is the same as the communication packet already received (that is, both communication packets P1 and P2 are It is possible to determine that the data has been received normally. When it is determined that they are the same, the intra-network transfer function unit 310 discards the communication packet (see step S702), and ends the process related to the received packet.

  If it is determined in step S701 that the communication packet is not the same as the communication packet already received, the intra-network transfer function unit 310 determines whether or not the communication packet is stored in the hold buffer 311 (see step S703). If the hold buffer 311 is empty, the received packet is stored (see step S704), the hold timer 312 is started (see step S705), and the process related to the received packet is ended. When the time measured by the hold timer 312 reaches a predetermined hold time, the communication packet in the hold buffer 311 is discarded. Normally, the time measured by the hold timer 312 reaches a predetermined hold time when one or more communication packets are lost in both the packet switching networks 130 and 140. In such a case, the hold buffer 311 is used. This is because it is considered that it is not useful to deliver only one of the communication packets to the application function unit 210. When a communication packet is lost, for example, in TCP or the like, communication is made to the transmission side packet switching device (here, the packet switching device 110) by an instruction of the application function unit 210 of the reception side packet switching device (here, the packet switching device 120). A packet resend request is sent. The holding time is arbitrary, but is set to, for example, several milliseconds to several tens of milliseconds.

  If it is determined in step S703 that the communication packet is stored in the hold buffer 311, the intra-network transfer function unit 310 compares the sequence number of the stored packet with the sequence number of the received packet (P1 or P2) ( (See step S706).

  If these sequence numbers are consecutive, the intra-network transfer function unit 310 determines that these communication packets have been received in reverse order, and instructs the packet output unit 350 to transmit the received packet and the hold packet ( (See step S707). At this time, transfer of the communication packet received from the preceding apparatus is also instructed to the inter-network transfer function unit 320. Further, the intra-network transfer function unit 310 stops the hold timer 312 (see step S708), discards the stored packet by releasing the hold buffer (see step S709), and sets the expected value of the sequence number to “+1”. Increment (see step S710), and the process related to the received packet ends.

  If the sequence numbers match in step S706, the intra-network transfer function unit 310 determines that these communication packets are the same packet and instructs the packet output unit 350 to transmit the received packet (step S706). S711). At this time, transfer of the communication packet received from the preceding apparatus is also instructed to the inter-network transfer function unit 320. When a reception packet having a sequence number larger than the expected value is stored in the hold buffer 311 due to the reverse of the reception order or the loss of the previous communication packet, and when the same communication packet as the storage packet is received, in step S706 A determination is made that the packets are the same. The intra-network transfer function unit 310 stops the hold timer 312, releases the hold buffer, and increments the expected value (see Steps S <b> 708 to S <b> 710), and ends the processing related to the received packet.

  On the other hand, if the sequence numbers do not match and are not consecutive in step S706, the intra-network transfer function unit 310 overwrites the received packet in the hold buffer 311 (see step S712) and restarts the hold timer 312. (Refer to step S713), the process regarding the received packet is terminated. The sequence numbers become discontinuous in step S706 in many cases when communication packets are lost both between the packet switching device 110 and the packet relay device 131-1 and between the packet switching device 110 and the packet relay device 141-1. In such a case, it is considered that it is not useful to transfer only one communication packet in the hold buffer 311 to the next-stage device.

  Other packet relay apparatuses 131-2 to 131-n and 141-1 to 141-n are also similar to the packet relay apparatus 131-1, and receive communication packets received from the preceding apparatus and other packet switching networks. The packet is transferred to the subsequent device. As a result, the communication packet double-transmitted by the packet switching device 110 reaches the packet switching device 120 except when a communication failure or the like occurs.

  Packet input / output units 230 and 240 (see FIG. 2) in the packet switching apparatus 120 receive the communication packets P1 and P2 from the packet relay apparatuses 131-n and 141-n. Then, the packet input / output units 230 and 240 send the communication packets P1 and P2 to the packet transmission / reception function unit 220.

  When the packet transmission / reception function unit 220 in the packet switching device 120 receives the communication packet P1 or P2 from the packet input / output unit 230 or 240, it checks whether or not identification information is stored in the communication packet (FIG. 8). (See step S801). Since the identification information is stored here, the packet transmission / reception function unit 220 determines that the communication packet is a communication packet related to double transmission, and compares the sequence number of the received packet with an expected value ( (See step S803). The packet transmission / reception function unit 220 stores the addresses of other packet switching devices capable of performing dual transmission, as in the above-described intra-network transfer function unit 310, and is further received next for each address. The sequence number (expected value) of the communication packet to be stored is temporarily stored. When the sequence number of the received packet matches the expected value, the packet transmission / reception function unit 220 increments the expected value by “+1” (see step S804) and notifies the application function unit 210 of reception of the communication packet. (See step S805).

  Subsequently, the packet transmission / reception function unit 220 checks the hold buffer 221 (see step S806). When the communication packet is not stored in the hold buffer 221, the packet transmission / reception function unit 220 ends the process related to the received packet. On the other hand, when it is determined in step S806 that the communication packet is stored in the hold buffer 221, the packet transmission / reception function unit 220 compares the sequence number of the hold packet with the sequence number of the received packet (see step S807). .

  When these sequence numbers are consecutive, the packet transmission / reception function unit 220 notifies the application function unit 210 of the communication packet (hold packet) stored in the hold buffer 221 (see step S808), and the expected value of the sequence number. Is further incremented by “+1” (see step S809), the hold timer 222 is stopped and the hold buffer 221 is released (see steps S810 and S811), and the process for the received packet is completed. By such processing, when two consecutive packets are received in the reverse order, the order can be corrected and transferred to the application function unit 210.

  On the other hand, if the sequence numbers are not consecutive in step S807, the hold timer 222 is restarted, and the process related to the received packet ends. By this process, the holding time of the holding buffer 221 is extended.

  If the sequence number does not match the expected value in step S803, the packet transmission / reception function unit 220 checks whether the received communication packet is the same as the already received communication packet (see step S901 in FIG. 9). . For example, when the sequence number is greater than or equal to the initial value and smaller than the expected value stored therein, the communication packet is the same as the already received communication packet (ie, each packet switched network 130, 140 is It is possible to determine that both of the same communication packets P1 and P2 transmitted through the network have been normally received. If it is determined that they are the same, the packet transmission / reception function unit 220 discards the communication packet (see step S902), and ends the process related to the received packet.

  If it is determined in step S901 that the communication packet is not the same as the communication packet already received, the packet transmission / reception function unit 220 determines whether the communication packet is stored in the hold buffer 221 (see step S903). If the hold buffer 221 is empty, the received packet is stored (see step S904), the hold timer 222 is started (see step S905), and the process related to the received packet is ended. Note that, for the same reason as the intra-network transfer function unit 310 described above, when the time measured by the hold timer 222 reaches a predetermined hold time, the communication packet in the hold buffer 221 is discarded.

  If it is determined in step S903 that the communication packet is stored in the hold buffer 221, the packet transmission / reception function unit 220 compares the sequence number of the stored packet with the sequence number of the received packet (see step S906).

  If these sequence numbers are consecutive, the packet transmission / reception function unit 220 determines that these communication packets have been received in reverse order, and notifies the application function unit 210 of the received packet and the hold packet (step S907). (See step S908), the hold buffer is released, the stored packet is discarded (see step S909), and the expected value of the sequence number is incremented by “+1” (see step S910). ), The processing related to the received packet is terminated.

  If the sequence numbers match in step S906, the packet transmission / reception function unit 220 determines that these communication packets are the same packet, and notifies the application function unit 210 of the received packet (see step S911). . Further, the packet transmission / reception function unit 220 stops the hold timer 222, releases the hold buffer, and increments the expected value (see steps S908 to S910), and ends the process related to the received packet.

  On the other hand, if the sequence numbers do not match and are not consecutive in step S906, the packet transmission / reception function unit 220 overwrites the received packet in the hold buffer 221 for the same reason as the above-described intra-network transfer function unit 310 (step S906). In step S912, the hold timer 222 is restarted (see step S913), and the process related to the received packet ends.

  In the packet communication system 100 according to this embodiment, unless a communication failure or a large-scale delay occurs, the communication packet double-transmitted by the packet switching device 110 is transmitted via the interface IFs 11 and 12 to the packet relay device 131-1. 141-1, all communication paths A1 to An-1, B1 to Bn-1 in the packet switching networks 130 and 140 and all communication paths C1 to Cn and D1 to Dn between the packet switching networks 130 and 140 are connected. It passes through and is received by the packet relay devices 131-n and 141-n. Therefore, when a communication failure or the like occurs in a part of these communication paths A1 to An-1, B1 to Bn-1, C1 to Cn, and D1 to Dn, the possibility that the service is stopped is extremely reduced. be able to.

  FIG. 10 is a conceptual diagram illustrating an operation example of the packet communication system 100 when an abnormality occurs. As shown in FIG. 10, in the packet communication system 100 according to this embodiment, a communication failure or the like occurs in a part of the communication paths A1 to An-1, B1 to Bn-1, C1 to Cn, and D1 to Dn. However, normal duplex communication can be performed after the failure point.

  Further, according to this embodiment, even when a failure or the like occurs in one of the interface IFs 11 and 12 or one of the interface IFs 21 and 22, it is possible to continue providing services.

  Furthermore, according to this embodiment, since whether or not to perform duplex communication can be determined by the transmission side packet switching devices 110 and 120, only the services for which the delay / loss of communication packets is a serious problem are multiplexed. And congestion of the packet switching networks 130 and 140 is not increased unnecessarily.

  In addition, in the packet switching devices 110 and 120 of this embodiment, the identity of the communication packet is determined using the source address and the sequence number, and this determination process is performed between the TCP / UDP layer and the IP layer. Therefore, the identity determination process is simple and does not affect the control of the upper layer (TCP / UDP or application layer).

  In addition, in the packet communication system 100 according to this embodiment, it is not necessary to individually set a communication path for each communication packet, so the processing is simple.

  In this embodiment, the sequence number of the communication packet is assigned to each destination address in the transmission side packet switching apparatus and is checked for each transmission source address in the reception side packet switching apparatus. (That is, a series of sequence numbers are assigned to a plurality of communication packets having the same address and the same application session). This makes it possible to manage double transmission for each application session.

Second Embodiment Next, a second embodiment of the present invention will be described with reference to FIGS.

  The configurations of the packet communication system, the packet switching device, and the packet relay device according to this embodiment are substantially the same as those in the case of the first embodiment (see FIGS. 1 to 3). However, the hold buffer 221 provided in the packet transmission / reception function unit 220 in the packet switching devices 120 and 130 and the intra-network transfer function unit 310 in the packet relay devices 131-1 to 131-n and 141-1 to 141-n. 311 is different from the first embodiment in that a plurality of communication packets can be temporarily stored for each source address, and hold timers 222 and 312 are provided for each of the plurality of hold packets.

  Further, the transmission operation of the packet switching apparatus is the same as that of the first embodiment.

  11 and 12 are flowcharts for explaining the reception operation of the intra-network transfer function unit 310 provided in the packet relay devices 131-1 to 131-n and 141-1 to 141-n according to this embodiment. is there.

  When the intra-network transfer function unit 310 receives a communication packet from each packet input / output unit (see FIG. 3), it first checks whether identification information is stored in the communication packet (see step S1101 in FIG. 11). ). If the identification information is not stored, the intra-network transfer function unit 310 determines that the communication packet is a communication packet related to single transmission, and instructs the packet output unit 350 to transmit the communication packet (step S31). (See S1102). After that, the intra-network transfer function unit 310 ends the process related to the received packet.

  On the other hand, if the identification information is stored in step S1101, the intra-network transfer function unit 310 determines that the communication packet is a communication packet related to double transmission, and compares the sequence number with the expected value ( (See step S1103). When the sequence number of the received packet matches the expected value, the intra-network transfer function unit 310 increments the expected value by “+1” (see step S1104) and instructs the packet output unit 350 to transmit the communication packet. (See step S1105). At this time, transfer of the communication packet received from the preceding apparatus is also instructed to the inter-network transfer function unit 320.

  Subsequently, the intra-network transfer function unit 310 checks the reservation buffer 311 (see step S1106). If no communication packet is stored in the hold buffer 311, the intra-network transfer function unit 310 ends the process related to the received packet. On the other hand, if it is determined in step S1106 that one or more communication packets are stored in the hold buffer 311, the intra-network transfer function unit 310 compares the sequence numbers of each hold packet and received packet with each other (step S1106). S1107). Then, a transmission instruction to the packet output unit is given to the communication packets having the consecutive sequence numbers (see step S1108). At this time, transfer of the communication packet received from the preceding apparatus is also instructed to the inter-network transfer function unit 320. Further, the intra-network transfer function unit 310 increments the expected value of the sequence number by the number of communication packets instructed to transfer (see step S1109). For example, if the sequence numbers of two pending packets are “n + 2” and “n” and the sequence number of the received packet is “n + 1”, the sequence numbers of these three communication packets are consecutive. The transmission of the communication packet is instructed. On the other hand, when the sequence numbers of the two pending packets are “n + 2” and “n” and the sequence number of the received packet is “n−1”, the pending packet and the received packet with the sequence number “n” are transmitted. Instructed.

  Subsequently, the intra-network transfer function unit 310 checks whether or not a hold packet remains in the hold buffer 311 (step S1110). If no pending packet remains, the suspension timer 312 is stopped (see step S1111) and the suspension buffer 311 is released (see step S1112), and the processing related to the received packet is terminated.

  On the other hand, if there are no pending / received packets with consecutive sequence numbers in step S1107, or if there are any pending packets remaining in the pending buffer 311 in step S1110, the pending timer 312 is restarted and the received packet The process related to is terminated.

  If the sequence number does not match the expected value in step S1103, the intra-network transfer function unit 310 checks whether the received communication packet is the same as the already received communication packet, as in the first embodiment. (See step S1201 in FIG. 12). If it is determined that they are the same, the intra-network transfer function unit 310 discards the communication packet (see step S1202), and ends the process related to the received packet.

  On the other hand, if it is determined in step S1201 that it is not the same as the communication packet that has already been received, the intra-network transfer function unit 310 determines whether or not the reservation buffer 311 has a free space (see step S1203). If there is an empty space in the hold buffer 311, the received packet is stored in one of the empty portions (see step S 1204), the hold timer 312 is activated (see step S 1205), and processing related to the received packet is performed. finish.

  When it is determined in step S1203 that there is no space in the hold buffer 311, the packet transmission / reception function unit notifies the reception of the one with the largest sequence number in the stored packet (see step S 1206), and sets the expected value of the sequence number. A value that is larger by “+1” than the sequence number is set (see step S1207), all the hold buffers 311 are released (see step S1208), the hold timer is stopped (see step S1209), and the received packet is related. End the process. Communication packets are temporarily stored in all the hold buffers 311 in many cases when communication packets are lost in both packet switching networks 130 and 140. In such a case, several packets in the hold buffer 311 are stored. This is because it is considered that it is not useful to deliver only the communication packet to the application function unit 210.

  FIGS. 13 and 14 are flowcharts for explaining the reception operation of the packet transmission / reception function unit 220 provided in the packet switching apparatuses 110 and 120 according to this embodiment.

  When receiving a communication packet from each packet input / output unit (see FIG. 2), the packet transmission / reception function unit 220 first checks whether or not identification information is stored in the communication packet (see step S1301 in FIG. 13). . If the identification information is not stored, the packet transmission / reception function unit 220 determines that the communication packet is a communication packet for single transmission, and notifies the application function unit 210 of reception of the communication packet (step S1302). And the processing related to the received packet is terminated.

  On the other hand, when the identification information is stored in step S1301, the packet transmission / reception function unit 220 determines that the communication packet is a communication packet related to double transmission, and compares the sequence number with the expected value (step S1301). (See S1303). When the sequence number of the received packet matches the expected value, the packet transmission / reception function unit 220 increments the expected value by “+1” (see step S1304) and notifies the application function unit 210 of reception of the communication packet. (See step S1305).

  Subsequently, the packet transmission / reception function unit 220 checks the hold buffer 221 (see step S1306). When the communication packet is not stored in the hold buffer 221, the packet transmission / reception function unit 220 ends the process related to the received packet. On the other hand, when it is determined in step S1306 that one or more communication packets are stored in the hold buffer 221, the packet transmission / reception function unit 220 compares the sequence numbers of each hold packet and the received packet with each other (step S1307). reference). Then, with respect to communication packets having consecutive sequence numbers, reception notification to the application function unit 210 is performed (see step S1308), and the expected value of the sequence number is incremented by the number of notified communication packets (see step S1309). .

  Next, the packet transmission / reception function unit 220 checks whether or not a pending packet remains in the pending buffer 221 (step S1310). If no pending packet remains, the suspension timer 222 is stopped (see step S1311) and the suspension buffer 221 is released (see step S1312), and the processing related to the received packet is terminated.

  On the other hand, if there are no hold / reception packets with consecutive sequence numbers in step S1307, or if there are any hold packets remaining in the hold buffer 221 in step S1310, the hold timer 222 is restarted, and the received packet The process related to is terminated.

  If the sequence number does not match the expected value in step S1303, the packet transmission / reception function unit 220 checks whether the received communication packet is the same as the already received communication packet, as in the first embodiment. (See step S1401 in FIG. 14). If it is determined that they are the same, the packet transmission / reception function unit 220 discards the communication packet (see step S1402), and ends the process related to the received packet.

  On the other hand, when it is determined in step S1401 that it is not the same as the communication packet that has already been received, the packet transmission / reception function unit 220 determines whether or not there is an empty space in the hold buffer 221 (see step S1403). If there is a vacancy in the hold buffer 221, the received packet is stored in one of the vacant portions (see step S1404), the hold timer 222 is started (see step S1405), and the process related to the received packet is performed. finish.

  If it is determined in step S1403 that the hold buffer 221 is not empty, the packet transmission / reception function unit 220 receives the one with the largest sequence number in the stored packet for the same reason as the case of the intra-network transfer function unit 310 described above. In addition to the notification (see step S1406), the expected value of the sequence number is set to a value “+1” larger than the sequence number (see step S1407), and all the pending buffers are released (see step S1408). The timer is stopped (see step S1409), and the process related to the received packet is terminated.

  As described above, according to this embodiment, for the same reason as in the first embodiment described above, service interruption due to disconnection of a communication line or the like is unlikely to occur, and congestion of the packet switching network is unnecessarily increased. In addition, the identity determination process is simple and does not affect the control of other layers, and it is not necessary to individually set communication paths.

  In addition, according to this embodiment, since a plurality of communication packets can be temporarily stored in the hold buffer at the same time, the number of communication packets to be relieved can be increased.

  The point that communication packets may be managed for each application session is the same as in the first embodiment.

1 is a conceptual diagram schematically showing an overall configuration of a communication system according to a first embodiment. It is a block diagram which shows roughly the internal structure of the packet switching apparatus which concerns on 1st Embodiment. It is a block diagram which shows roughly the internal structure of the packet relay apparatus which concerns on 1st Embodiment. It is a conceptual diagram which shows the layer structure employ | adopted with the packet communication system which concerns on 1st Embodiment. It is a conceptual diagram for demonstrating the whole operation | movement of the packet communication system which concerns on 1st Embodiment. It is a flowchart for demonstrating the relay operation | movement of the packet relay apparatus which concerns on 1st Embodiment. It is a flowchart for demonstrating the relay operation | movement of the packet relay apparatus which concerns on 1st Embodiment. It is a flowchart for demonstrating the reception operation | movement of the packet switching apparatus which concerns on 1st Embodiment. It is a flowchart for demonstrating the reception operation | movement of the packet switching apparatus which concerns on 1st Embodiment. It is a conceptual diagram for demonstrating the whole operation | movement at the time of abnormality occurrence of the packet communication system which concerns on 1st Embodiment. It is a flowchart for demonstrating the relay operation | movement of the packet relay apparatus which concerns on 2nd Embodiment. It is a flowchart for demonstrating the relay operation | movement of the packet relay apparatus which concerns on 2nd Embodiment. It is a flowchart for demonstrating the reception operation | movement of the packet switching apparatus which concerns on 2nd Embodiment. It is a flowchart for demonstrating the reception operation | movement of the packet switching apparatus which concerns on 2nd Embodiment.

Explanation of symbols

100 packet communication system 110, 120 packet switching device 130, 140 packet switching network 210 application function unit 220 packet transmission / reception function unit 230, 240 packet input / output unit 310 intra-network transfer function unit 320 inter-network transfer function unit 330, 340 packet input unit 350, 360 packet output section

Claims (10)

A packet communication system in which a transmission device and a reception device are connected via first and second communication networks,
The first communication network includes a plurality of first relay devices,
The second communication network includes a plurality of second relay devices that are communicatively connected to corresponding first relay devices;
The transmission device includes means for generating two identical communication packets and outputting them to the first and second relay devices in the first stage,
When the first relay device has not received the communication packet received from the transmitting device or the first relay device in the preceding stage or the communication packet received from the corresponding second relay device, the first relay device in the latter stage A first in-network transfer means that transfers to one relay device or the receiving device and discards the communication packet if it has been received; and the communication packet received from the transmitting device or the first relay device in the previous stage First inter-network transfer means for transferring to the second relay device corresponding to a case where it has not been received,
When the second relay device has not received the communication packet received from the transmitter or the second relay device in the previous stage or the communication packet received from the corresponding first relay device, the second relay device The second in-network transfer means for transferring to the 2 relay device or the receiving device and discarding the communication packet if it has already been received, and the communication packet received from the transmitting device or the second relay device in the previous stage A second inter-network transfer means for transferring to the first relay device corresponding to a case where it has not been received,
The receiving device discards the communication packet received from the first and second relay devices at the final stage if it has already been received;
A packet communication system. The transmitter transmits communication packets storing the same user data, the same sequence number, and identification information indicating multiplex communication to the first and second communication networks, and
Means for the first and second relay devices and the receiving device to determine whether the identification information is stored in the received communication packet; a source address if the identification information is stored; Means for determining the identity of the communication packet using the sequence number,
The packet communication system according to claim 1. The transmitting device issues the sequence number for each session of an application corresponding to the communication packet; and
The communication packet and the communication packet that has already been received only when the transmission source address, the sequence number, and the session of the application all match in the first and second relay devices and the reception device. Judging that they are the same,
The packet communication system according to claim 2.   3. The packet communication system according to claim 1, wherein the determination of the identity of the communication packet is executed as a process related to a layer between an original network layer and a transport layer.   The packet communication system according to claim 1 or 2, wherein a sequence number defined by a transmission control protocol or a real-time transport protocol is used as the sequence number. A packet relay device for constructing each of a plurality of communication networks for communication connection between a transmission device and a reception device,
If the communication packet received from the transmission device or the relay device in the previous stage or the communication packet received from the corresponding relay device in another communication network is not received, the relay device or the reception device in the subsequent stage And in-network transfer means for discarding the communication packet if it has already been received,
An inter-network transfer means for transferring to the corresponding relay device of the other communication network when the communication packet received from the transmitting device or the preceding relay device is not received;
A packet relay device comprising: Receiving the communication packet in which the same user data, the same sequence number, and identification information indicating multiplex communication are stored;
Determining whether the identification information is stored in the communication packet;
Determining the identity of the communication packet using a source address and the sequence number when the identification information is stored;
The packet relay apparatus according to claim 6. The sequence number is issued for each session of the application corresponding to the communication packet, and
Only when the source address, the sequence number, and the session of the application all match, the communication packet and the already received communication packet are determined to be the same.
The packet relay apparatus according to claim 7.   8. The packet relay apparatus according to claim 6, wherein the determination of the identity of the communication packet is executed as a process related to a layer between an original network layer and a transport layer.   The packet relay apparatus according to claim 6 or 7, wherein a sequence number defined by a transmission control protocol or a real-time transport protocol is used as the sequence number.