JP2014050090A - Packet repeater and method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a packet repeater and a control method therefor capable of dispersing server load by appropriately measuring a response to per-server application service.SOLUTION: The packet repeater comprises: transmission means for generating a session establishment packet for a plurality of servers and transmitting the generated packet via a network; and reception means for receiving a first confirmation response to the session establishment packet from a server and discarding the received response. The transmission means transmits a second confirmation response packet to the corresponding server upon the first confirmation response received, and calculates, as a delay time for each server, a difference between the time of day when the session establishment packet is transmitted and the time of day when the second confirmation response packet is transmitted, thereby creating a correspondence relation with the servers. The servers are assigned higher priority in order of increasing delay time in the correspondence relation, so that when a packet is received from a client, the received packet is transmitted via a network to the server corresponding to the priority indicated by the received packet.

Description

  The present invention relates to a packet relay apparatus and method for relaying packets between a client and a server existing in a network.

  In a network in which a plurality of clients and a plurality of servers exist, if service processing is concentrated on a specific server in a short time due to requests from a large number of clients, the load on the server increases, resulting in a decrease in response. Become. A load distribution technique for avoiding such load concentration on a specific server is already known.

  In a conventional IP packet relay device, a method of monitoring a server response using a Ping packet (ICMP echo request / reply packet) as a load balancing technique is used (see Patent Document 1).

  In the IP packet relay device disclosed in Patent Document 1, a Ping request packet is periodically created and transmitted to each server, the packet transmission time for each server is recorded, and the Ping request packet is transmitted from the server. Received Ping response packet, record the packet reception time for each server, calculate the delay time that is the difference between the transmission time and reception time for each server as a response, and prioritize the packets in order of the server with the smallest delay time Degrees are 1, 2, 3,. . . Setting is performed as follows. As a result, packets having higher priority among packets received in the packet relay operation are transmitted to a server having a smaller delay time.

JP 2012-15667 A

  In such a conventional IP packet relay apparatus, the response of the server including the load state of the IP network is measured using the Ping packet. It is only measured. On the other hand, since an application service that is actually used uses a higher layer of layer 4 or higher, there is a problem that a response measured using a Ping packet does not necessarily represent an appropriate response for each server.

  In addition, the priority of the Ping packet may be set high in the IP network and the server. In such a case, the Ping packet may be transferred with priority over other packets in the IP network and the server. Therefore, the response is far from the response to the packet carrying the application service, and the response is good. Therefore, there is a problem that even if the response of the server is measured using the Ping packet, the response in the actual application service cannot always be measured accurately.

  Accordingly, an object of the present invention is to provide a packet relay apparatus and method capable of appropriately measuring a response to an application service for each server and performing server load distribution.

  The packet relay device of the present invention is a packet relay device that relays packets between a plurality of servers and clients in a network, and generates a session establishment packet for each of the plurality of servers and corresponds to the server A transmission means for transmitting to the packet through the network, and receiving a first acknowledgment packet addressed to the packet relay apparatus from each of the plurality of servers for the session establishment packet via the network. Receiving means for discarding, wherein the transmitting means transmits the second acknowledgment packet to the corresponding server via the network in response to reception of the first acknowledgment packet, and the server Each time, the difference between the transmission time of the session establishment packet and the transmission time of the second acknowledgment packet is delayed. And calculating a relationship between the server and the delay time, and setting a higher priority to the plurality of servers in order of the server having the smallest delay time in the correspondence relationship, and the client via the network When a packet to be relayed is received, the received packet is transmitted to the server corresponding to the priority indicated by the received packet via the network.

  The packet relay method of the present invention is a relay method of a packet relay device that relays packets between a plurality of servers and clients in a network, and generates a session establishment packet for each of the plurality of servers. Transmitting to the corresponding server via the network; receiving a first acknowledgment packet from each of the plurality of servers for the session establishment packet via the network and discarding it; Transmitting the second acknowledgment packet to the corresponding server via the network in response to reception of the first acknowledgment packet, and the transmission time of the session establishment packet for each server; The difference between the transmission time of the second acknowledgment packet and the delay time is calculated as the delay time. Creating a correspondence relationship between the server and the delay time, setting a higher priority to the plurality of servers in order of the server having the smallest delay time in the correspondence relationship, and relaying from the client via the network And a step of transmitting the received packet via the network to a server corresponding to the priority indicated by the received packet when the packet to be received is received.

  In the packet relay apparatus and method of the present invention, only the low layer monitoring is performed like the Ping packet or the Ethernet OAM Loop back packet by measuring the time until the session is established with the server as the delay time of the server. Instead, it is possible to monitor the server response in the same layer as the application service that is actually used. Therefore, it is possible to appropriately measure the response to the application service for each server and perform server load distribution.

1 is a block diagram illustrating an IP network system including an IP packet relay device according to a first embodiment of the present invention. It is a figure which shows the priority table contained in the priority and destination determination part of the relay apparatus of FIG. It is a figure which shows the sequence at the time of the delay time measurement mode of the relay apparatus of FIG. It is a figure which shows the sequence at the time of the normal operation mode of the relay apparatus of FIG. It is a block diagram which shows the IP network system containing the IP packet relay apparatus of Example 2 of this invention. It is a figure which shows the sequence at the time of URI registration mode of the relay apparatus of FIG. It is a figure which shows the sequence at the time of the delay time measurement mode of the relay apparatus of FIG. It is a figure which shows the sequence at the time of the normal operation mode of the relay apparatus of FIG.

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

FIG. 1 shows an IP network system including an IP packet relay device 10 according to a first embodiment of the present invention. In addition to the IP packet relay apparatus 10, this IP network system includes a plurality of clients 21 _{1 to} 21 _M (M is an integer of 2 or more) and a plurality of servers 22 _{1 to} 22 _N (N is an integer of 2 or more). ing. The IP packet relay device 10, the clients 21 _{1 to} 21 _M and the servers 22 _{1 to} 22 _N are connected to the IP network 23, respectively. The connection with the network 23 may be either wired or wireless.

The clients 21 _{1 to} 21 _M are terminal devices such as personal computers, notebook computers, and smart phones.

The servers 22 _{1 to} 22 _N are server computers such as a web server, a mail server, and a SIP server that can provide services.

The IP packet relay device 10 includes a plurality of line processing units 11 _{1 to} 11 _S (S is an integer of 2 or more) and a switch unit 12. It shows only configuration of the line processing unit 11 ₁ in FIG. 1, the line processing unit ₁₁ 1 to 11 _S have the same configuration.

Line processing unit 11 _1, Layer 1 & 2 reception processing unit 31, TCP (Transmission Control Protocol) response extraction unit 32, the reception packet buffer 33, the priority and the destination determining unit 34, TCP sequence management unit 35, TCP request generator 36, a time management unit 37, a delay time determination unit 38, a transmission packet buffer 39, a TCP request transmission confirmation unit 40, and a layer 1-2 transmission processing unit 41.

  The layer 1 and 2 reception processing unit 31, the TCP response extraction unit 32, and the reception packet buffer 33 constitute reception means. The TCP sequence management unit 35, TCP request generation unit 36, delay time determination unit 38, transmission packet buffer 39, TCP request transmission confirmation unit 40, and layer 1 and 2 transmission processing unit 41 constitute a transmission means.

  The layer 1 and 2 reception processing unit 31 receives a packet input from the IP network 23 and performs physical layer and data link layer termination processing on the packet. A TCP response extraction unit 32 is connected to the output of the layer 1 and 2 reception processing unit 31, and the packet subjected to termination processing in the layer 1 and 2 reception processing unit 31 is supplied to the TCP response extraction unit 32.

The TCP response extraction unit 32 extracts a SYN ACK packet from the received packet to confirm the server response during the TCP session establishment operation, and extracts an ACK packet and a FIN packet during the session disconnection operation. Each of these packets is a packet whose destination is the IP address assigned to its own IP packet relay device 10 and whose source is any of the IP addresses of the servers 22 _{1 to} 22 _N. A reception packet buffer 33 is connected to the output of the TCP response extraction unit 32, and TCP packets other than the packet extracted by the TCP response extraction unit 32 and other packets are transferred from the TCP response extraction unit 32 to the reception packet buffer 33. Is done.

  The reception packet buffer 33 stores the packet transferred from the TCP response extraction unit 32. The reception packet buffer 33 is connected to the priority and destination determination unit 34.

The priority and destination determination unit 34 extracts a packet from the received packet buffer 33, and a device header indicating the IP address and line number of the server n (one of the servers 22 _{1 to} 22 _N ) determined by the priority of the packet Is added to the packet, and then the packet is transferred to the switch unit 12.

As shown in FIG. 2, the priority and destination determination unit 34 stores a priority table indicating the correspondence relationship between the priority, the server number, the delay time, the line number, and the destination IP address in the internal memory. Using this priority table, the destination IP address of the packet is rewritten and the above-described device header is created and attached to the packet. The line number is determined for each server, and corresponds to any _{one of} the line processing units 11 _{1 to} 11 _S.

The switch unit 12 is connected to the priority and destination determination unit 34 and the transmission packet buffer 39 of each of the line processing units 11 _{1 to} 11 _S. The switch unit 12 connects the packet transferred from the priority and destination determination unit 34 to the line processing unit (one of the line processing units 11 _{1 to} 11 _S ) corresponding to the line number indicated in the device header of the packet. To the transmission packet buffer 39.

  The transmission packet buffer 39 is connected to each of the switch unit 12, the TCP request generation unit 36, and the TCP request transmission confirmation unit 40. When a packet is transferred from the switch unit 12, the transmission packet buffer 39 stores the packet.

TCP request generation unit 36, to confirm the load state of the server ₂₂ 1 through 22 _N, respectively, present IP packet relay apparatus 10 to the assigned IP address to the sender, the IP address of the server ₂₂ 1 through 22 _N, respectively destination As described above, a SYN packet and an ACK packet are generated periodically during the TCP session establishment operation, and similarly, a FIN packet and an ACK packet are generated during the session disconnection operation. These packets are delay time measurement packets. When they are generated, they are supplied to the transmission packet buffer 39 and stored therein.

  The TCP request transmission confirmation unit 40 is disposed between the transmission packet buffer 39 and the layer 1 and 2 transmission processing unit 41, and the layer 1 and 2 transmission processing is performed in the order in which the packets stored in the transmission packet buffer 39 are stored. Supplied to the unit 41. Further, when the TCP request transmission confirmation unit 40 supplies each of the SYN packet and the ACK packet to the layer 1 and 2 transmission processing unit 41 during the session establishment operation generated by the TCP request generation unit 36, these packets are transmitted. Notifies the delay time determination unit 38 of the time when it passes through the TCP request transmission confirmation unit 40.

  The layer 1 and 2 transmission processing unit 41 performs physical layer and data link layer termination processing on the packet supplied from the TCP request transmission confirmation unit 40, and sends the packet to the IP network 23.

  The TCP sequence management unit 35 is connected to the TCP response extraction unit 32 and the TCP request generation unit 36. The TCP request generation unit 36 uses the packet for delay time measurement (the SYN ACK packet during the session establishment operation, and the session). The generation of the FIN packet and the ACK packet during the cutting operation is managed. Specifically, in the session establishment operation, when it is time to generate a SYN packet for delay time measurement, a command for generating a session establishment SYN packet is sent to the TCP request generation unit 36. In response to this, the TCP request generation unit 36 receives a notification of the completion of SYN packet generation, and then receives a SYN ACK packet reception notification from the TCP response extraction unit 32. The TCP request generation unit 36 generates an ACK packet. Command. Further, the TCP request generator 36 receives a notification of completion of ACK packet generation. In session disconnection, a command for generating a session disconnection FIN packet is sent to the TCP request generation unit 36. In response to this, the TCP request generator 36 receives a notification of completion of the FIN packet generation. Thereafter, upon receiving notification of ACK packet reception from the TCP response extraction unit 32 and further notification of FIN packet reception, the TCP request generation unit 36 is instructed to generate an ACK packet. Further, the TCP request generator 36 receives a notification of completion of ACK packet generation.

  The time management unit 37 includes a counter that counts the time, and supplies the current time information to the TCP response extraction unit 32, the TCP request generation unit 36, and the TCP request transmission confirmation unit 40. The TCP request transmission confirmation unit 40 refers to this time information and provides the packet transit time to the delay time determination unit 38.

The delay time determination unit 38 selects _{one of} the servers n (22 _{1 to} 22 _N) according to the time when the SYN packet passes and the time when the ACK packet passes during the session establishment operation supplied from the TCP request transmission confirmation unit 40. 1), and notifies the priority and destination determination unit 34 of the delay time. The delay time is calculated for all of the servers 22 _{1 to} 22 _N and notified to the priority and destination determination unit 34.

  The priority and destination determination unit 34 stores a priority table in a memory (not shown), and associates the server with the minimum delay time of each of these servers with the priority 1 of the priority table described above. The server number, delay time, line number, and destination IP address for priority 1 in the priority table are rewritten from the previous contents. Further, the server with the next smallest delay time is made to correspond to priority 2 in the priority table, and the server number, delay time, line number, and destination IP address for priority 2 in the priority table are the contents up to that point. Rewrite from In this way, priorities are determined as 1, 2, 3,... In order of increasing delay time, and each item in the priority table is updated. The server corresponding to the priority is determined by using the delay time calculated this time as it is as the delay time, but the average value, minimum value, or maximum value of the delay time measured within the past T (min). The server corresponding to the priority may be determined using or taking into account.

Next, transmission / reception of packets between the IP packet relay device 10 and the server n when the operation mode of the IP packet relay device 10 becomes the delay time measurement mode will be described with reference to the TCP sequence diagram of FIG. This sequence of the delay time measurement mode is repeated at intervals of time Ti for all the servers 22 _{1 to} 22 _N.

First, the TCP request generation unit 36 of the line processing unit S (one of the line processing units 11 _{1 to} 11 _S ) corresponding to the server n of the IP packet relay device 10 is assigned to the IP packet relay device 10. A SYN packet (session establishment packet) is generated during the TCP session establishment operation using the address as the source IP address and the IP address of the server n as the destination IP address (step S1). The SYN packet generated by the TCP request generation unit 36 is stored in the transmission packet buffer 39, and then extracted from the SYN packet, passes through the TCP request transmission confirmation unit 40, and is transmitted from the layer 1-2 transmission processing unit 41 to the IP network 23. To the server n (step S2). The time ta when the SYN packet passes through the TCP request transmission confirmation unit 40 is notified to the delay time determination unit 38 for measuring the delay time.

  When the server n receives the SYN packet, the server n generates a SYN ACK packet (first acknowledgment packet) as a response thereto (step S3), and sends the SYN ACK packet to the IP packet relay apparatus 10 via the IP network 23. (Step S4). The source IP address of the SYN ACK packet is the IP address assigned to the server n, and the destination IP address is the IP address assigned to the IP packet relay device 10.

  The SYN ACK packet is received by the line processing unit S corresponding to the server n of the IP packet relay apparatus 10. The TCP response extraction unit 32 of the line processing unit S determines that the SYN ACK packet is a SYN ACK packet transmitted to the IP packet relay device 10, and does not transfer it to the reception packet buffer 33, but again Then, it is discarded so as not to be sent to the IP network 23 (step S5). The extraction of the SYN ACK packet by the TCP response extraction unit 32 is notified to the TCP sequence management unit 35.

  Thereafter, the TCP request generation unit 36 of the line processing unit S uses the IP address assigned to the IP packet relay device 10 as the transmission source IP address and the IP address of the server n as the destination according to the instruction of the TCP sequence management unit 35 As the IP address, an ACK packet (second acknowledgment packet) is generated during the TCP session establishment operation (step S6). The ACK packet generated by the TCP request generation unit 36 is stored in the transmission packet buffer 39, and is then extracted from the ACK packet, passes through the TCP request transmission confirmation unit 40, and is transmitted from the layer 1-2 transmission processing unit 41 to the IP network 23. To the server n (step S7). The time tb when the ACK packet passes through the TCP request transmission confirmation unit 40 is notified to the delay time determination unit 38 for measuring the delay time.

  When this ACK packet is received by the server n, a TCP session between the IP packet relay apparatus 10 and the server n is established.

The delay time determination unit 38 calculates a delay time tb-ta for the server n according to the time ta when the SYN packet passes and the time tb when the ACK packet passes, and the delay time is sent to the priority and destination determination unit 34. Be notified. In the priority and destination determination unit 34, priorities are determined as 1, 2, 3,... In order of increasing delay time as described above according to the delay time of each of the servers 22 _{1 to} 22 _N. Each item is updated.

  Then, in order to avoid wasteful consumption of the bandwidth of the IP network 23 due to the establishment of the TCP session, the TCP request generation unit 36 is immediately assigned to the IP packet relay device 10 according to the instruction of the TCP sequence management unit 35. A TCP session disconnection FIN packet (first session disconnection packet) is generated using the IP address as the source IP address and the server n as the destination IP address (step S8). The FIN packet generated by the TCP request generation unit 36 is stored in the transmission packet buffer 39 and is then extracted from the FIN packet and passed through the TCP request transmission confirmation unit 40 from the layer 1 and 2 transmission processing unit 41 to the IP network 23. To the server n (step S9).

  When the server n receives the FIN packet, it generates an ACK packet as a response thereto (step S10), and transmits the ACK packet (third acknowledgment packet) to the IP packet relay apparatus 10 via the IP network 23. (Step S11). The source IP address of this ACK packet is the IP address assigned to the server n, and the destination IP address is the IP address assigned to the IP packet relay device 10.

  The ACK packet is received by the line processing unit S corresponding to the server n of the IP packet relay device 10. The TCP response extraction unit 32 of the line processing unit S determines that the ACK packet is an ACK packet transmitted to the IP packet relay device 10, does not transfer it to the reception packet buffer 33, and again transmits the IP packet It discards so that it may not be sent to the network 23 (step S12).

  Also, after transmitting the ACK packet in step S11, the server n generates a FIN packet (second session disconnection packet) (step S13), and sends the FIN packet to the IP packet relay apparatus 10 via the IP network 23. (Step S14). The source IP address of the FIN packet is an IP address assigned to the server n, and the destination IP address is an IP address assigned to the IP packet relay device 10.

  The FIN packet transmitted in step S14 is received by the line processing unit S corresponding to the server n of the IP packet relay apparatus 10. The TCP response extraction unit 32 of the line processing unit S determines that the FIN packet is a FIN packet transmitted to the IP packet relay device 10, does not transfer it to the reception packet buffer 33, and again transmits the IP packet It discards so that it may not be sent to the network 23 (step S15).

  In addition, the TCP request generation unit 36 of the line processing unit S uses the IP address assigned to the IP packet relay apparatus 10 to respond to the FIN packet in response to a command from the TCP sequence management unit 35 as a transmission source IP address, An ACK packet (fourth acknowledgment packet) is generated with the IP address of server n as the destination IP address (step S16). The ACK packet generated by the TCP request generation unit 36 is stored in the transmission packet buffer 39, and is then extracted from the ACK packet, passes through the TCP request transmission confirmation unit 40, and is transmitted from the layer 1-2 transmission processing unit 41 to the IP network 23. To the server n (step S17).

  When this ACK packet is received by the server n, the TCP session between the IP packet relay device 10 and the server n is disconnected, and the IP packet relay device 10 ends the delay time measurement mode and the normal operation mode. Become.

Next, when the operation mode of the IP packet relay device 10 becomes the normal operation mode, the IP packet relay device 10, the client m (one of the clients 21 _{1 to} 21 _M ), and the server n (the servers 22 _{1 to} 22). Packet transmission / reception with one of _N ) will be described with reference to the TCP sequence diagram of FIG.

When there is a request for establishing a TCP session from the client m to the server n, the SYN packet in the client m is an IP network with the IP address of the client m as the source IP address and the IP address of the server n as the destination IP address. 23 (step S21). In the IP packet relay device 10, when the SYN packet is received by the layer 1 or 2 reception processing unit 31, the received packet is not discarded by the TCP response extraction unit 32 because it is not a packet addressed to the IP packet relay device 10. The data is transferred to the buffer 33 and temporarily stored therein. The SYN packet is extracted from the reception packet buffer 33 by the priority and destination determination unit 34, and a device header indicating the IP address of the server n determined by the priority of the SYN packet is added to the packet using the priority table, and then , The SYN packet is transferred to the switch unit 12. The SYN packet transferred from the priority / destination determination unit 34 to the switch unit 12 is transmitted by the switch unit 12 to the line processing unit (of the line processing units 11 _{1 to} 11 _S corresponding to the line number indicated in the device header of the packet). Is transmitted to the transmission packet buffer 39 and temporarily stored therein. The SYN packets stored in the transmission packet buffer 39 are taken out by the TCP request transmission confirmation unit 40 in the order in which they are stored, supplied to the layer 1/2 transmission processing unit 41, and directed to the server n by the layer 1/2 transmission processing unit 41. Is sent to the IP network 23 (step S22).

  When the server n receives the SYN packet, the server n sends a SYN ACK packet to the IP network 23 with the IP address of the server n as the source IP address and the IP address of the client m as the destination IP address in order to respond to the SYN packet (step S23). ). In the IP packet relay device 10, when the SYN ACK packet is received by the layer 1 and 2 reception processing unit 31, it is not a packet addressed to the IP packet relay device 10, so the SYN ACK packet is discarded as in the case of the SYN packet. The layer 1 and 2 transmission processing unit 41 transmits the data to the IP network 23 toward the client m (step S24).

  Upon receiving the SYN ACK packet, the client m sends an ACK packet to the IP network 23 with the IP address of the client m as the source IP address and the IP address of the server n as the destination IP address in order to respond to it (step S25). ). In the IP packet relay device 10, when the ACK packet is received by the layer 1 and 2 reception processing unit 31, the packet is not addressed to the IP packet relay device 10, so the ACK packet is the same as in the case of a SYN packet or a SYN ACK packet. And is sent to the IP network 23 toward the server n by the layer 1 and 2 transmission processing unit 41 (step S26).

  When this ACK packet is received by the server n, a TCP session between the client m and the server n via the IP packet relay apparatus 10 is established. Therefore, data transfer such as image data and audio data by the packet is executed (step S27).

  When the data transfer is completed, a FIN packet is sent from the client m to the server n via the IP packet relay device 10 (steps S28 and S29), and in response thereto, an ACK packet is sent from the server n to the IP packet relay device 10. To the client m (steps S30 and S31). Further, the FIN packet is sent from the server n to the client m through the IP packet relay device 10 (steps S32 and S33). In response, an ACK packet is sent from the client m to the server n via the IP packet relay device 10 (steps S34 and S35). When this ACK packet is received by the server n, the TCP session between the client m and the server n via the IP packet relay apparatus 10 is disconnected. Since these FIN packets and ACK packets are not packets addressed to the IP packet relay device 10, the packets between the client m and the server n are not discarded by the IP packet relay device 10 in the same manner as packets for establishing a TCP session. Forwarded.

  As described above, in the first embodiment, the time until the TCP session is established is measured as the delay time of the server, so that a low layer such as a Ping (ICMP echo request / reply) packet or an Ethernet OAM Loop back packet is used. Instead of only monitoring, it is possible to monitor the server response in the same layer as the application service actually used.

  In addition, since the established TCP session is immediately disconnected after the delay time measurement, useless bandwidth consumption of the IP network due to the establishment of the TCP session can be prevented.

FIG. 5 shows an IP network system including the IP packet relay devices 10A and 10B according to the second embodiment of the present invention. This IP network system uses SIP (Session Initiation Protocol) which is one of call control protocols, clients 21 _{1 to} 21 _M are SIP clients, and servers 22 _{1 to} 22 _N are SIP servers.

UDP (User Datagram Protocol) is used as a default protocol for transmission / reception of packets by SIP, and control packets including UDP packets and TCP packets are used in the IP packet relay device 10, the clients 21 _{1 to} 21 _M, and the servers 22 _{1 to} 22 _N. Can be sent and received.

The IP packet relay apparatuses 10A and 10B have the same configuration, and include a plurality of line processing units 11 _{1 to} 11 _S (S is an integer of 2 or more) and a switch unit 12. FIG. 5 shows only the configuration of the line processing unit 11 ₁ of the IP packet relay apparatus 10A, but the line processing units 11 _{1 to} 11 _S have the same configuration. In Example 1, the same parts of FIG. 1 in the line processing unit 11 ₁ of FIG. 5 are denoted by the same reference numerals.

Line processing unit 11 _1, Layer 1 & 2 reception processing unit 31, SIP response extraction unit 51, the reception packet buffer 33, the priority and the destination determining unit 34, SIP sequence management unit 52, SIP request generator 53, the time management unit 37, a delay time determination unit 38, a transmission packet buffer 39, a SIP request transmission confirmation unit 54, and a layer 1 and 2 transmission processing unit 41.

The SIP request generation unit 53 uses the SIP URI (Uniform Resource Identifier) assigned to its own IP packet relay device 10A (10B) as the transmission source address and the IP address assigned to the IP packet relay device 10A (10B) as a server address. A REGISTER packet at the time of SIP URI registration is generated with the IP address of n (one of the servers 22 _{1 to} 22 _N ) as the destination.

  In the delay time measurement mode in which the SIP request generator 53 measures the delay time as the load state of the server, the IP address / SIP URI assigned to its own IP packet relay device 10A (10B) is used as the source IP address / A SIP URI, an IP address of the server n is a destination IP address, a SIP URI of the opposite IP packet relay device 10B is a destination SIP URI, and an INVITE packet and an ACK packet are generated during the SIP session establishment operation, A BYE packet is generated during the session disconnection operation. The delay time measurement mode is periodically executed according to a command from the SIP sequence management unit 52. In the delay time measurement mode, the INVITE packet and the ACK packet are generated for delay time measurement, and the BYE packet is generated to disconnect the SIP session for delay time measurement.

  The SIP request transmission confirmation unit 54 notifies the delay time determination unit 38 of the time when each of the delay time measurement INVITE packet and the ACK packet generated by the SIP request generation unit 53 passes through the SIP request transmission confirmation unit 54.

  The delay time determination unit 38 calculates the delay time according to the time when the INVITE packet supplied from the SIP request transmission confirmation unit 54 passes and the time when the ACK packet passes in the delay time measurement mode.

  The SIP response extraction unit 51 extracts the 200 OK packet at the time of SIP URI registration, and the 100 Trying packet, 180 Ringing packet, and 200 OK packet in the delay time measurement mode in order to confirm the server response. Also, the client side error 300-series packet and the server-side error 400-series packet are extracted. Except at the time of URI registration, any extracted packet has the IP address / SIP URI assigned to its own IP packet relay apparatus 10A as the destination IP address / SIP URI, the IP address of server n as the source IP address, The packet having the SIP URI of the IP packet relay apparatus 10B as the source SIP URI is transferred to the reception packet buffer 33 for other SIP packets and other packets. The packet extracted at the time of URI registration is a packet in which the IP address assigned to the IP packet relay apparatus 10A is the destination IP address and the IP address of the server n is the source IP address. Other REGISTER packets and other packets Is transferred to the reception packet buffer 33.

  The SIP sequence management unit 52 is connected to the SIP response extraction unit 51 and the SIP request generation unit 53. The SIP sequence management unit 52 includes a packet (an INVITE packet and an ACK packet during the session establishment operation, and a session) in the delay time measurement mode. The generation of BYE packets during the cutting operation is managed. Specifically, in the session establishment operation, when it is time to generate an INVITE packet for delay time measurement, an instruction to generate an INVITE packet for session establishment is sent to the SIP request generation unit 53. On the other hand, when the notification of the completion of the INVITE packet generation is received from the SIP request generation unit 53 and then the notification of the 100 Trying packet, the 180 Ringing packet, and the 200 OK packet reception is sequentially received from the SIP response extraction unit 51, the SIP request generation The unit 53 is instructed to generate an ACK packet. Further, the SIP request generator 53 receives a notification of completion of ACK packet generation. In session disconnection, an instruction for generating a BYE packet for session disconnection is sent to the SIP request generation unit 53. In response to this, the SIP request generator 36 receives a notification of the completion of BYE packet generation. Thereafter, when a notification of 200 OK packet reception is received from the SIP response extraction unit 51, the delay time measurement mode is terminated.

  In addition, the SIP response management unit 52 is notified from the SIP response extraction unit 51 that the client side error 300 series packet or the server side error 400 series packet addressed to the IP packet relay apparatus 10A itself is received in the delay time measurement mode. If packet retransmission is set, the SIP request generation unit 53 is instructed to retransmit the immediately preceding INVITE packet or BYE packet. If packet retransmission is not set, wait for the interval Ti and issue an instruction to start again from transmission of the INVITE packet in the next cycle, or if the session is being established, instruct the SIP request generator 53 to generate a BYE packet. To disconnect the session.

  Other configurations of the second embodiment are the same as those of the first embodiment, and thus further description thereof is omitted here.

Next, between the IP packet relay devices 10A and 10B and the server n (any one of the servers 22 _{1 to} 22 _N ) when the operation mode of the IP packet relay devices 10A and 10B is the URI registration mode. Packet transmission / reception will be described with reference to the sequence diagram of FIG. In this URI registration mode, the SIP URIs of the IP packet relay apparatuses 10A and 10B are registered in all the servers 22 _{1 to} 22 _N.

  In the IP packet relay device 10A, when the operation mode is the URI registration mode, the SIP sequence management unit 52 notifies the SIP request generation unit 53 of a URI registration command. In response to this command, the SIP request generation unit 53 uses the IP address assigned to the IP packet relay device 10A as the source IP address, the IP address of the server n as the destination IP address, and further assigned to the IP packet relay device 10A. A REGISTER packet using the SIP URI as registration information is generated (step S51). The REGISTER packet generated by the SIP request generation unit 53 is stored in the transmission packet buffer 39, and then extracted from the REGISTER packet, passes through the SIP request transmission confirmation unit 54, and is transmitted from the layer 1-2 transmission processing unit 41 to the IP network 23. To the server n (step S52).

  Upon receiving the REGISTER packet, the server n registers a SIP URI according to the REGISTER packet (step S53), generates a 200 OK packet as a response (step S54), and sends the 200 OK packet to the IP packet relay device 10A. To the IP network 23 (step S55).

  The 200 OK packet is received by the line processing unit S corresponding to the server n of the IP packet relay apparatus 10A. The SIP response extraction unit 51 of the line processing unit S determines that the 200 OK packet is a packet transmitted to the IP packet relay apparatus 10A, does not transfer it to the reception packet buffer 33, and again transmits the IP packet. It discards so that it may not be sent to the network 23 (step S56).

  As shown in steps S61 to S66, the REGISTER packet and the 200 OK packet are similarly transmitted and received between the IP packet relay apparatus 10B and the server n, and the SIP URI assigned to the IP packet relay apparatus 10B is transmitted to the server n. be registered.

Next, packet transmission / reception between each of the IP packet relay devices 10A and 10B and the server n when the operation mode of the IP packet relay device 10A becomes the delay time measurement mode will be described with reference to the sequence diagram of FIG. This sequence of the delay time measurement mode is repeated at intervals of time Ti for all the servers 22 _{1 to} 22 _N.

  First, the SIP request generation unit 53 of the line processing unit S (one of the line processing units 111 to 11S) corresponding to the server n of the IP packet relay device 10A receives the IP address assigned to the IP packet relay device 10A and The SIP URI is the source IP address and the source SIP URI, the IP address of the server n is the destination IP address, and the SIP URI of the IP packet relay device 10B is the destination SIP URI. (Establishment packet) is generated (step S71). The INVITE packet generated by the SIP request generation unit 53 is stored in the transmission packet buffer 39, and is then extracted from the packet and passed through the SIP request transmission confirmation unit 54 from the layer 1-2 transmission processing unit 41 to the IP network 23. To the server n (step S72). The time ta when the INVITE packet passes through the SIP request transmission confirmation unit 54 is notified to the delay time determination unit 38 for the delay time measurement.

  Upon receiving the INVITE packet, the server n sends it to the IP network 23 in order to transfer the INVITE packet to the IP packet relay device 10B that is the destination SIP URI of the INVITE packet (step S73). The source IP address of the INVITE packet in step S73 is the IP address of the server n, the destination IP address is the IP address of the IP packet relay device 10B, and the source SIP URI is the SIP URI of the IP packet relay device 10A. The destination SIP URI is the SIP URI of the IP packet relay device 10B. The server n receives the INVITE packet from the IP packet relay device 10A and generates a 100 Trying packet to notify the IP packet relay device 10A that it is processing it (step S74). (Step S75). The source IP address of the 100 Trying packet is the IP address of the server n, the destination IP address is the IP address of the IP packet relay device 10A, the source SIP URI is the SIP URI of the IP packet relay device 10B, and the destination SIP The URI is the SIP URI of the IP packet relay device 10A.

  The 100 Trying packet is received by the line processing unit S corresponding to the server n of the IP packet relay apparatus 10A. The SIP response extraction unit 51 of the line processing unit S determines that the 100 Trying packet is a packet transmitted to the IP packet relay apparatus 10A, does not transfer it to the reception packet buffer 33, It discards so that it may not be sent to the network 23 (step S76). The extraction of 100 Trying packets by the SIP response extraction unit 51 is notified to the SIP sequence management unit 52.

  In the IP packet relay device 10B, the INVITE packet is received by the line processing unit S corresponding to the server n of the IP packet relay device 10B. The SIP response extraction unit 51 of the line processing unit S determines that the INVITE packet is an INVITE packet transmitted to the IP packet relay apparatus 10B, does not transfer it to the reception packet buffer 33, and again transmits the IP packet It discards so that it may not be sent to the network 23 (step S77). Since the reception of the INVITE packet is notified to the SIP sequence management unit 52 of the line processing unit S, the SIP request generation unit 53 generates a 180 Ringing packet in response to a command from the SIP sequence management unit 52 (step S78). Further, a 200 OK packet is generated (step S82). Each of the 180 Ringing packet and the 200 OK packet generated by the SIP request generation unit 53 is stored in the transmission packet buffer 39, and is then extracted from the packet and passed through the SIP request transmission confirmation unit 54. The data is transmitted from the unit 41 to the server n via the IP network 23 (steps S79 and S83). Each of the 180 Ringing packet and the 200 OK packet is transmitted by the SIP request generation unit 53 using the IP address assigned to the IP packet relay device 10B as the source IP address and the IP address of the server n as the destination IP address. The SIP URI of the device 10B is generated as the source SIP URI, and the SIP URI of the IP packet relay device 10A is generated as the destination SIP URI.

  Each time the server n individually receives the 180 Ringing packet and the 200 OK packet, the server n transfers the 180 Ringing packet and the 200 OK packet (first acknowledgment packet) to the IP packet relay device 10A that is the destination SIP URI of the packet. It is sent to the IP network 23 (steps S80 and S84). The source IP address of each of the 180 Ringing packet and the 200 OK packet is the IP address of the server n, the destination IP address is the IP address of the IP packet relay device 10A, and the source SIP URI is the SIP address of the IP packet relay device 10B. It is a URI, and the destination SIP URI is the SIP URI of the IP packet relay apparatus 10A.

  The 180 Ringing packet and the 200 OK packet from the server n are received by the line processing unit S corresponding to the server n of the IP packet relay apparatus 10A. The SIP response extraction unit 51 of the line processing unit S determines that the 180 Ringing packet and the 200 OK packet are packets transmitted to the IP packet relay device 10A, and does not transfer them to the reception packet buffer 33. Then, it is discarded again so as not to be sent to the IP network 23 (steps S81 and S85). The SIP sequence management unit 52 is notified of the extraction of the 180 Ringing packet and the 200 OK packet by the SIP response extraction unit 51.

  Thereafter, the SIP request generation unit 53 of the line processing unit S sets the IP address and SIP URI assigned to the IP packet relay device 10A as the transmission source IP address and transmission source SIP URI in accordance with the instruction of the SIP sequence management unit 52. An ACK packet (second acknowledgment packet) is generated with the IP address of the server n as the destination IP address and the SIP URI assigned to the IP packet relay device 10B as the destination SIP URI (step S86). The ACK packet generated by the SIP request generation unit 53 is stored in the transmission packet buffer 39, and then extracted from the ACK packet, passes through the SIP request transmission confirmation unit 54, and is transmitted from the layer 1-2 transmission processing unit 41 to the IP network 23. To the server n (step S87). The time tb when the ACK packet passes through the SIP request transmission confirmation unit 54 is notified to the delay time determination unit 38 for delay time measurement.

  When the server n receives the ACK packet, it sends it to the IP network 23 in order to transfer the ACK packet to the IP packet relay device 10B which is the destination SIP URI of the ACK packet (step S88). The source IP address of the ACK packet in step S88 is the IP address of server n, the destination IP address is the IP address of IP packet relay device 10B, and the source SIP URI is the SIP URI of IP packet relay device 10A. The destination SIP URI is the SIP URI of the IP packet relay device 10B.

  In the IP packet relay device 10B, the ACK packet is received by the line processing unit S corresponding to the server n of the IP packet relay device 10B. The SIP response extraction unit 51 of the line processing unit S determines that the ACK packet is an ACK packet transmitted to the IP packet relay device 10B, and does not transfer it to the reception packet buffer 33. It discards so that it may not be sent to the IP network 23 (step S89). When the ACK packet is received by the IP packet relay device 10B, a SIP session is established between the IP packet relay devices 10A and 10B.

The delay time determination unit 38 calculates a delay time tb-ta for the server n according to the time ta when the INVITE packet passes and the time tb when the ACK packet passes, and the delay time is sent to the priority and destination determination unit 34. Be notified. In the priority and destination determination unit 34, priorities are determined as 1, 2, 3,... In order of increasing delay time as described above according to the delay time of each of the servers 22 _{1 to} 22 _N. Each item is updated.

  Then, in order to avoid wasteful consumption of the bandwidth of the IP network 23 due to the establishment of the SIP session, the SIP request generation unit 53 immediately responds to the command of the SIP sequence management unit 52 of the SIP packet relay device 10A. The IP address and SIP URI assigned to the packet relay device 10A are set as the source IP address and SIP URI, the IP address of the server n is set as the destination IP address, and the SIP URI assigned to the IP packet relay device 10B is set as the destination SIP URI. Then, a BYE packet (first session disconnection packet) for SIP session disconnection is generated (step S90). The BYE packet generated by the SIP request generation unit 53 is stored in the transmission packet buffer 39, and then extracted from the BYE packet, passes through the SIP request transmission confirmation unit 54, and is transmitted from the layer 1-2 transmission processing unit 41 to the IP network 23. To the server n (step S91).

  Upon receiving the BYE packet, the server n sends it to the IP network 23 in order to transfer the BYE packet to the IP packet relay device 10B that is the destination SIP URI of the BYE packet (step S92). The source IP address of the BYE packet in step S92 is the IP address of the server n, the destination IP address is the IP address of the IP packet relay device 10B, and the source SIP URI is the SIP URI of the IP packet relay device 10A. The destination SIP URI is the SIP URI of the IP packet relay device 10B.

  When the IP packet relay device 10B receives the BYE packet, the BYE packet is received by the line processing unit S corresponding to the server n of the IP packet relay device 10B. The SIP response extraction unit 51 of the line processing unit S determines that the BYE packet is a BYE packet transmitted to the IP packet relay apparatus 10B, does not transfer it to the reception packet buffer 33, It discards so that it may not be sent to the network 23 (step S93). Since the reception of the BYE packet is notified to the SIP sequence management unit 52 of the line processing unit S, the SIP request generation unit 53 generates a 200 OK packet in accordance with a command from the SIP sequence management unit 52 (step S94). The 200 OK packet generated by the SIP request generation unit 53 is stored in the transmission packet buffer 39, and is then taken out from the packet and passed through the SIP request transmission confirmation unit 54 to the IP network from the layer 1-2 transmission processing unit 41. 23 is transmitted to the server n via step 23 (step S95). In the 200 OK packet, the SIP request generation unit 53 uses the IP address assigned to the IP packet relay device 10B as the source IP address, the IP address of the server n as the destination IP address, and the SIP URI of the IP packet relay device 10B. Is generated as the source SIP URI, and the SIP URI of the IP packet relay apparatus 10A is generated as the destination SIP URI.

  When the server n receives the 200 OK packet, the server n sends it to the IP network 23 in order to transfer the 200 OK packet (third acknowledgment packet) to the IP packet relay device 10A which is the destination SIP URI of the packet (step). S96). The source IP address of the 200 OK packet is the IP address of the server n, the destination IP address is the IP address of the IP packet relay device 10A, the source SIP URI is the SIP URI of the IP packet relay device 10B, and the destination The SIP URI is the SIP URI of the IP packet relay device 10A.

  The 200 OK packet from the server n is received by the line processing unit S corresponding to the server n of the IP packet relay apparatus 10A. The SIP response extraction unit 51 of the line processing unit S determines that the 200 OK packet is a packet transmitted to the IP packet relay device 10A, and does not transfer it to the reception packet buffer 33. It discards so that it may not be sent to the IP network 23 (step S97). The extraction of the 200 OK packet by the SIP response extraction unit 51 is notified to the SIP sequence management unit 52.

  When the 200 OK packet is received by the IP packet relay device 10A, the session via the server n between the IP packet relay devices 10A and 10B is disconnected, and the delay time measurement mode ends in the IP packet relay device 10A. It becomes the normal operation mode.

Next, when the operation mode of the IP packet relay apparatus 10A becomes the normal operation mode, the client m1 makes a call to the client m1 (one of the clients 21 _{1 to} 21 _M ), and the client m1 then receives the IP packet relay apparatus 10A, the server n, Packet communication with the client m2 (another one of the clients 21 _{1 to} 21 _M ) via the IP packet relay device 10B will be described with reference to the SIP sequence diagram of FIG.

When there is a SIP session establishment request from the client m1 to the server n, in the client m1, the INVITE packet uses the IP address of the client m1 as the source IP address, the IP address of the server n as the destination IP address, and the client The SIP URI of m1 is set as the source SIP URI and the SIP URI of the client m2 is set as the destination SIP URI, and is sent to the IP network 23 (step S101). In the IP packet relay device 10A, when the INVITE packet is received by the layer 1 and 2 reception processing unit 31, the received packet is not discarded by the SIP response extraction unit 51 because it is not a packet addressed to the IP packet relay device 10A. The data is transferred to the buffer 33 and temporarily stored therein. The priority and destination determination unit 34 extracts the INVITE packet from the reception packet buffer 33, and uses the priority table to determine the server n (one of the servers 22 _{1 to} 22 _N ) determined by the priority of the INVITE packet. A device header indicating the IP address is added to the packet, and then the INVITE packet is transferred to the switch unit 12. The INVITE packet transferred from the priority / destination determination unit 34 to the switch unit 12 is transmitted to the line processing unit (of the line processing units 11 _{1 to} 11 _S) corresponding to the line number indicated in the device header of the packet by the switch unit 12. Is transmitted to the transmission packet buffer 39 and temporarily stored therein. The INVITE packets stored in the transmission packet buffer 39 are taken out by the SIP request transmission confirmation unit 54 in the order in which they are stored and supplied to the layer 1 and 2 transmission processing unit 41, and are sent to the server n by the layer 1 and 2 transmission processing unit 41. Is sent to the IP network 23 (step S102).

  When the server n receives the INVITE packet, the server n uses the IP address of the server n as the source IP address, the IP address of the client m2 as the destination IP address, the SIP URI of the client m1 as the source SIP URI, and the client The INVITE packet is sent to the IP network 23 with the SIP URI of m2 as the destination SIP URI (step S103).

In the IP packet relay device 10B, when the INVITE packet from the server n is received by the layer 1 and 2 reception processing unit 31, the SIP response extraction unit 51 does not discard the INVITE packet because it is not a packet addressed to the IP packet relay device 10B. The packet is transferred to the reception packet buffer 33 and temporarily stored therein. The priority and destination determination unit 34 extracts the INVITE packet from the reception packet buffer 33, and uses the priority table to determine the server n (one of the servers 22 _{1 to} 22 _N ) determined by the priority of the INVITE packet. A device header indicating the IP address is added to the packet, and then the INVITE packet is transferred to the switch unit 12. The INVITE packet transferred from the priority / destination determination unit 34 to the switch unit 12 is transmitted to the line processing unit (of the line processing units 11 _{1 to} 11 _S) corresponding to the line number indicated in the device header of the packet by the switch unit 12. Is transmitted to the transmission packet buffer 39 and temporarily stored therein. The INVITE packets stored in the transmission packet buffer 39 are extracted by the SIP request transmission confirmation unit 54 in the order in which they are stored, and are supplied to the layer 1 and 2 transmission processing unit 41. Is sent to the IP network 23 (step S104).

  The server n receives the INVITE packet from the client m1 and sends a 100 Trying packet to the IP network 23 to inform the client m1 that it is processing it (step S105). The source IP address of the 100 Trying packet is the IP address of server n, the destination IP address is the IP address of client m1, the source SIP URI is the SIP URI of client m2, and the destination SIP URI is the SIP address of client m1. URI.

The 100 Trying packet is received by the line processing unit S corresponding to the server n of the IP packet relay device 10A, and is not a packet addressed to the IP packet relay device 10A. Transferred to and temporarily stored there. The priority and destination determination unit 34 extracts the 100 Trying packet from the reception packet buffer 33 and uses the priority table to determine the server n (one of the servers 22 _{1 to} 22 _N determined by the priority of the 100 Trying packet. ) Is added to the packet, and then the 100 Trying packet is transferred to the switch unit 12. The 100 Trying packet transferred from the priority and destination determination unit 34 to the switch unit 12 is transmitted to the line processing unit (line processing units 11 _{1 to} 11 _S corresponding to the line number indicated in the device header of the packet by the switch unit 12. One of them) is supplied to the transmission packet buffer 39 and temporarily stored therein. The 100 Trying packets stored in the transmission packet buffer 39 are extracted by the SIP request transmission confirmation unit 54 in the order in which they are stored and supplied to the layer 1 and 2 transmission processing unit 41. To the IP network 23 (step S104).

  In response to the reception of the INVITE packet, the client m2 transmits a 180 Ringing packet (step S107), and further transmits a 200 OK packet (step S111). Each of these 180 Ringing packet and 200 OK packet has the IP address of the client m2 as the source IP address, the IP address of the server n as the destination IP address, the SIP URI of the client m2 as the source SIP URI, and the client m1's IP address. A SIP URI is generated as a destination SIP URI. Each of the 180 Ringing packet and the 200 OK packet is relayed by the IP packet relay device 10B and sent to the IP network 23 toward the server n (steps S108 and S112).

  Each time the server n receives the 180 Ringing packet and the 200 OK packet individually, the server n sends the 180 Ringing packet and the 200 OK packet to the IP network 23 in order to transfer them (Steps S109 and S113). The source IP address of each of the 180 Ringing packet and the 200 OK packet is the IP address of the server n, the destination IP address is the IP address of the client m1, the source SIP URI is the SIP URI of the client m2, and the destination SIP The URI is the SIP URI of the client m1. Each of the 180 Ringing packet and the 200 OK packet from the server n is relayed by the IP packet relay device 10A and sent to the IP network 23 toward the client m1 (steps S110 and S114).

  When the client m1 receives each of the 180 Ringing packet and the 200 OK packet, it sends an ACK packet to the IP network 23 in response to it (step S115). The source IP address of this ACK packet is the IP address of the client m1, the destination IP address is the IP address of the server n, the source SIP URI is the SIP URI of the client m1, and the destination SIP URI is the SIP address of the client m2. URI.

  The ACK packet sent from the client m1 is further relayed by the IP packet relay device 10A and sent to the IP network 23 toward the server n (step S116). When the server n receives the ACK packet, it sends it to the IP network 23 in order to transfer the ACK packet to the client m2 (step S117). The source IP address of the ACK packet sent from the server n is the IP address of the server n, the destination IP address is the IP address of the client m2, the source SIP URI is the SIP URI of the client m1, and the destination SIP URI Is the SIP URI of client m2. The ACK packet is further relayed by the IP packet relay device 10B and sent to the IP network 23 toward the client m2 (step S118).

  When the ACK packet is received by the client m2, a SIP session between the clients m1 and m2 is established. Therefore, transmission / reception of media data such as audio data and video data is performed between the clients m1 and m2 (step S119).

  When the transmission / reception of the media data is completed, the client m1 sends a BYE packet to the IP network 23 to disconnect the SIP session (step S120). The source IP address of this BYE packet is the IP address of the client m1, the destination IP address is the IP address of the server n, the source SIP URI is the SIP URI of the client m1, and the destination SIP URI is the SIP address of the client m2. URI.

  The BYE packet is transferred to the client m2 via the IP packet relay device 10A, the server n, and the IP packet relay device 10B as in steps S121 to S123, similarly to the transfer of the ACK packet. In response to this, the client m2 sends a 200 OK packet to the IP network 23 (step S124). The source IP address of the 200 OK packet is the IP address of the client m2, the destination IP address is the IP address of the server n, the source SIP URI is the SIP URI of the client m2, and the destination SIP URI is the client SIP address. It is a SIP URI.

  The 200 OK packet is transferred to the client m1 via the IP packet relay device 10B, the server n, and the IP packet relay device 10A as in steps S124 to S127. This is the same as the 200 OK packet in steps S111 to S114 described above.

  When the client m1 receives the 200 OK packet, the session between the clients m1 and m2 via the IP packet relay device 10A, the server n, and the IP packet relay device 10B is disconnected.

  As described above, in the second embodiment, by measuring the time until the SIP session is established as the delay time of the server, a low layer such as a Ping (ICMP echo request / reply) packet or an Ethernet OAM loop back packet is used. Instead of only monitoring, it is possible to monitor the server response in the same layer as the application service actually used.

  Further, since the established SIP session is immediately disconnected after the delay time is measured, useless bandwidth consumption of the IP network due to the establishment of the SIP session can be prevented.

  Furthermore, since the URI of the IP packet relay device is registered in advance in the server, it is possible to avoid the occurrence of erroneous ringing (ringing tone) in the accommodated client.

  In the above-described embodiment, the example in which the TCP packet and the SIP packet are used as the server delay time measurement has been described. However, the server delay time may be measured using a higher layer protocol that provides an application service. good.

  In addition, each server, each client, and the IP packet relay device may be connected to the network by wire or wireless.

10, 10A, 10B IP packet relay apparatus 11 _{1 to} 11 _S line processing unit 12 switch unit 21 _{1 to} 21 _M , m, m1, m2 client
22 _{1 to} 22 _N , n server 23 IP network 32 TCP response extraction unit 35 TCP sequence management unit 36 TCP request generation unit 38 delay time determination unit 40 TCP request transmission confirmation unit 51 SIP response extraction unit 52 SIP sequence management unit 53 SIP request Generation unit 54 SIP request transmission confirmation unit

Claims (10)

A packet relay device that relays packets between a plurality of servers and clients in a network,
Transmitting means for generating a session establishment packet for each of the plurality of servers and transmitting the packet to the corresponding server via the network;
Receiving means for receiving a first acknowledgment packet addressed to the packet relay apparatus from each of the plurality of servers for the session establishment packet via the network and discarding the packet;
The transmission means includes
In response to receiving the first acknowledgment packet, sending a second acknowledgment packet to the corresponding server via the network;
For each server, calculate the difference between the transmission time of the session establishment packet and the transmission time of the second acknowledgment packet as a delay time to create a correspondence between the server and the delay time,
In the correspondence, the priority is set high for the plurality of servers in the order of the servers with the shortest delay time,
When receiving a packet to be relayed from the client via the network, the packet relay apparatus transmits the received packet to the server corresponding to the priority indicated by the received packet via the network. The transmission means, after measuring the delay time of each of the plurality of servers, generates a first session disconnection packet for each server and transmits it to the corresponding server via the network,
The receiving means receives the third acknowledgment packet from each of the plurality of servers in response to the first session disconnection packet via the network and discards it. The packet relay apparatus described. The receiving means receives a second session disconnection packet addressed to the packet relay apparatus from each of the plurality of servers for the first session disconnection packet via the network, and discards it;
3. The packet relay according to claim 2, wherein the transmission unit transmits a fourth acknowledgment packet to the corresponding server via the network in response to reception of the second session disconnection packet. apparatus.   3. The packet relay apparatus according to claim 2, wherein the reception unit includes a response extraction unit that extracts and discards a packet addressed to the packet relay apparatus from received packets. The transmission means includes a request transmission confirmation unit that detects a transmission time of the session establishment packet and a transmission time of the second confirmation response packet;
4. A delay time determination unit that calculates the delay time according to a transmission time of the session establishment packet and a transmission time of the second confirmation response packet. 5. 1. The packet relay device according to 1. The transmission means includes a request generator for generating the session establishment packet, the second confirmation response packet, the first session disconnection packet, and the fourth confirmation response packet, respectively.
When the delay time measurement mode is started, the request generation unit is instructed to generate the session establishment packet, and when the response extraction unit extracts the first confirmation response packet, the second confirmation response packet is generated. To the request generation unit, and then instructs the request generation unit to generate the first session disconnection packet, and the response extraction unit extracts the second session disconnection packet when the fourth session disconnection packet is extracted. The packet relay apparatus according to claim 3, further comprising: a sequence management unit that instructs the request generation unit to generate an acknowledgment packet.   The packet relay apparatus according to claim 1, wherein the packet is a TCP packet.   7. The packet relay device according to claim 1, wherein the packet is a SIP packet.   9. The packet relay apparatus according to claim 8, wherein the transmission means includes means for registering a SIP URI for each of the plurality of servers before measuring the delay time. A relay method of a packet relay device that relays packets between a plurality of servers and clients in a network,
Generating a session establishment packet for each of the plurality of servers and transmitting it to the corresponding server over the network;
Receiving a first acknowledgment packet from each of the plurality of servers for the session establishment packet via the network and discarding it;
Transmitting a second acknowledgment packet to the corresponding server via the network in response to receiving the first acknowledgment packet;
Calculating a difference between the transmission time of the session establishment packet and the transmission time of the second acknowledgment packet for each server as a delay time and creating a correspondence between the server and the delay time;
Setting higher priority to the plurality of servers in the order of the servers with the smallest delay time in the correspondence relationship;
And when the packet to be relayed from the client via the network is transmitted to the server corresponding to the priority indicated by the received packet via the network. Relay method.

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