JP2006180274A - GATEWAY APPARATUS AND VoIP NETWORK SYSTEM - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a gateway apparatus and a VoIP network system for setting an optimum retransmission timing to overflowed packets so as to distribute transmitted packets thereby relieving a network load even when registered packets and other messages are concentrated on for a period of time. <P>SOLUTION: A protocol conversion gateway apparatus 108 manages packets whose number exceeds a threshold value among packets received within a prescribed time as transmission reservation packets, and a timer value calculation section 115 calculates a timer value in a way that the number of packets retransmitted within a predetermined time for every transmission reservation packet does not exceed the threshold value, and sets the timer value to a re-registration timer 116. When the re-registration timer 116 expires, the gateway apparatus 108 retransmits the packets to a server 201 compliant with protocol B. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a gateway device arranged at a connection point between a certain network and an external network, and in particular, a terminal device connected to a VoIP network having a certain protocol and connected to the VoIP network having a different protocol via the network. And a VoIP network system.

  By establishing a VoIP network (A) of a certain protocol A on a LAN and connecting a terminal device (protocol A compliant terminal) operating in accordance with the protocol A to the LAN, it is possible to make a call between the protocol A compliant terminals. For example, H.M. When H.323 is adopted as protocol A, a gatekeeper is installed on the LAN, each protocol A compliant terminal transmits a registration request (registration packet) to the gatekeeper to perform registration, and the registered protocol A compliant terminal Call connection is made through a gatekeeper.

  On the other hand, recently, an IP telephone service has been provided on the Internet. A VoIP network (B) of a certain protocol B is constructed on the Internet so that a telephone call can be made between terminal devices (protocol B compliant terminals) such as an IP telephone device operating according to the protocol B. For example, when SIP (Session Initiation Protocol) is adopted as protocol B, a SIP server is installed on the Internet, and each protocol B-compliant terminal transmits a registration packet to the SIP server to perform registration. A protocol B compliant terminal is call-connected through a SIP server.

  If a protocol A compliant terminal can be operated as a protocol B compliant terminal of a VoIP network (B) of another protocol B, a call can be made between the protocol A compliant terminal and the protocol B compliant terminal via the VoIP network (B). become. It is conceivable to arrange a protocol conversion gateway device for converting the protocol A and the protocol B on the LAN in which the VoIP network (A) of the protocol A is constructed. In this case, the protocol A compliant terminal transmits a registration packet to the gatekeeper on the LAN. The gatekeeper registers a protocol A-compliant terminal so that a call can be made on the VoIP network (A), and transmits a registration packet to the SIP server of the VoIP network (B) via the protocol conversion gateway device. The SIP server receives the registration packet and registers the protocol A compliant terminal as a protocol B compliant terminal. As a result, in the VoIP network (B), the protocol A compliant terminal is managed by an identification number (for example, 050) that can be recognized by the VoIP network (B).

  By the way, in the case of a large-scale VoIP network operated by a telecommunications carrier, there is not only one LAN provided with the above-described protocol conversion gateway device. It is expected that a large number of Protocol A compliant terminals will transmit registration packets via a protocol conversion gateway device of each LAN from a large number of LANs (VoIP network (A)). Since a valid period is set for registration in a VoIP network server such as a gatekeeper and a SIP server, in order to maintain a state in which each protocol A-compliant terminal can always make a call, a periodical or It is necessary to irregularly send a registration packet to a VoIP network server (a gatekeeper for H.323, a SIP server for SIP).

In order to avoid a congestion state when a failure occurs in the network or when a significant configuration change occurs in the network, measures for preventing a large amount of data from flowing in temporarily have been proposed. For example, when the number of packets exceeds a threshold value within a predetermined time, a command for suppressing the report is transmitted to a communication apparatus that reports state information periodically (see, for example, Patent Document 1).
JP 2001-111550 A

  However, protocol A-compliant terminals under the individual LANs send registration packets completely asynchronously at least between LANs, so that the load concentration of registration packets can occur in the SIP server and the network of the route to the SIP server. There is. Since it is expected that a large number of protocol A compliant terminals simultaneously transmit registration packets to the SIP server at the time of failure recovery, it is difficult to respond to all registration packets.

  The above is a phenomenon that appears prominently in the registration packet, but there is always a risk of load concentration similar to the above due to the system configuration described above even for messages (packets) other than the registration packet. To do.

  The present invention has been made in view of the above circumstances, and even when registration packets and other messages (packets) are concentrated at one time, by setting an optimum retransmission timing for overflow packets. An object of the present invention is to provide a gateway device and a VoIP network system that reduce packet load by distributing packet transmission.

  The present invention manages packets that exceed a threshold among packets received within a predetermined time as transmission reservation packets, and sets a timer value for each transmission reservation packet so that the number of packets retransmitted within a predetermined time does not exceed the threshold. When the calculated timer value expires, the corresponding packet is retransmitted.

  According to the present invention, even when registration packets and other messages (packets) are concentrated at one time, the packet transmission is distributed and the network load is reduced by setting the optimum retransmission timing for the overflow packets. Gateway device and VoIP network system can be provided.

  According to a first aspect of the present invention, when the number of packets received within a predetermined time exceeds a threshold, a packet that exceeds the threshold is managed as a transmission reservation packet and retransmitted when the timer value expires, and the retransmission control means And a timer value calculation unit that calculates the timer value for each transmission reservation packet so that the number of packets retransmitted within a predetermined time by the control unit does not exceed the threshold value.

  According to the gateway device configured as described above, the timer value is calculated so that the number of retransmitted packets does not exceed the threshold as the retransmission timing of the packets that exceed the threshold among the packets received within a predetermined time. Since it is set, the retransmission timing of the transmission reservation packet is also distributed.

  According to a second aspect of the present invention, in the gateway device according to the first aspect, the timer value calculation means calculates a timer value for each transmission reservation packet based on timer value = fixed value + number of transmission reservations / threshold value. It was decided to.

  As a result, when retransmission timings of transmission reservation packets are concentrated, there is an effect of being distributed according to the value of (number of transmission reservations / threshold).

  According to a third aspect of the present invention, in the gateway device according to the first or second aspect, a protocol A- is used for operating a terminal device connected to a VoIP network of protocol A as a terminal device of a VoIP network of another protocol B. Protocol conversion means for performing protocol conversion between protocols B was provided.

  As a result, the packet retransmission control can be performed in the gateway device that performs the protocol conversion between the protocol A and the protocol B on the protocol A VoIP network, and the packets transmitted toward the protocol B VoIP network are concentrated. In such a case, it is possible to suppress this.

  According to a fourth aspect of the present invention, in the gateway device according to the third aspect, the call control server conforming to the protocol A installed on the protocol A VoIP network conforms to the protocol B installed on the protocol VoIP network. When a registration packet requesting registration of a protocol A terminal with respect to the call control server is received, a protocol-converted registration packet is transmitted to the call control server compliant with protocol B, and a response from the call control server compliant with protocol B The response is returned to the call control server conforming to the protocol A without waiting.

  As a result, the registration request source terminal can continue or newly make a call on the protocol A VoIP network without waiting for registration to the protocol B VoIP network.

  According to a fifth aspect of the present invention, a call control server compliant with protocol A installed on a VoIP network of protocol A, a plurality of terminal devices compliant with protocol A, and a protocol B installed on a VoIP network of protocol B A call control server compliant with protocol B, a plurality of terminal devices compliant with protocol B, the VoIP network of protocol A and the VoIP network of protocol B, and protocol conversion between protocol A and protocol B is performed. In a VoIP network system including a gateway device that performs transmission and reception, when the number of packets received by the gateway device within a predetermined time exceeds a threshold value, the packet exceeding the threshold value is managed as a transmission reservation packet and the timer value expires A retransmission control means for retransmitting, The retransmission control unit is VoIP network system comprising a, a timer value calculating means for calculating for each transmission reservation packet the timer value as the number of packets to be retransmitted does not exceed the threshold within a predetermined time.

  With this configuration, even when registration packets and other messages are concentrated at one time, the packet transmission is distributed and the network load is reduced by setting the optimal retransmission timing for the overflowed packets. be able to.

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

  FIG. 1 is a diagram showing a network configuration of the present embodiment. A VoIP network constructed according to protocol A (H.323 in this example) is a protocol AVoIP network 100, and a VoIP network constructed according to protocol B (SIP in this example) is protocol BVoIP. A network 200 is assumed.

  Although the protocol AVoIP network 100 is constructed on a single LAN 101, it may be constructed on a plurality of interconnected LANs. A plurality of protocol A-compliant terminals are connected to the LAN 101. For example, the protocol A compliant terminal 102 can be configured by an IP telephone apparatus that supports protocol A. Further, the protocol A compliant terminal 103 can be configured by a protocol A compatible mobile phone device. The mobile phone device 103 connects to the LAN 101 by wireless communication with the wireless mobile base station 104 connected to the LAN 101. Further, the protocol A compliant terminal 105 can be configured by a PHS telephone apparatus that supports protocol A. The PHS telephone device 105 connects to the LAN 101 by wireless communication with a wireless PHS base station 106 connected to the LAN 101.

  Each of the protocol A compliant terminals 102, 103, and 105 is connected via a protocol A compliant server (in this example, a gatekeeper compatible with H.323). The protocol A compliant server receives and registers a registration request (registration packet) from each protocol A compliant terminal 102, 103, 105 on the LAN 101, and if there is a call connection request, it acts as an intermediary for a call between the protocol A compliant terminals do.

  The protocol AVoIP network 100 includes a protocol conversion gateway device 108 for connecting the subordinate protocol A compliant terminals 102, 103, and 105 to the protocol BVoIP network 200.

  The protocol conversion gateway device 108 has a function of performing protocol conversion between the protocol A and the protocol B in order to absorb the difference in protocol between the protocol AVoIP network 100 and the protocol B VoIP network 200. For example, each protocol A-compliant terminal 102, 103, 105 has a different identification number (E.164 system) used in the protocol AVoIP network 100 and an identification number (050 system) used in the protocol BVoIP network 200. For this reason, a process of changing the identification number according to the VoIP network of the connection destination at the time of protocol conversion is performed. FIG. 2 is an example of a number conversion table provided in the protocol conversion gateway device 108. Further, the protocol conversion gateway device 108 is implemented with protocols A and B in order to communicate with both the protocol AVoIP network 100 and the protocol BVoIP network 200.

  The protocol BVoIP network 200 is connected to the protocol AVoIP network 100 via a network 109. In this example, the protocol BVoIP network 200 is assumed to be a large-scale VoIP network managed by a communication carrier, but is not limited to such a large-scale network. A protocol B compliant server 201 is installed in the protocol BVoIP network 200.

  The protocol B compliant server 201 registers a protocol B compliant terminal under the protocol B VoIP network 200 as a subscriber terminal, receives a registration request from each protocol B compliant terminal, sets an expiration date, and registers as a call terminal. I do. In response to a call connection request from a registered protocol B compliant terminal, a command is transmitted to the called terminal, and the call connection between the calling terminal and the called terminal is mediated. In the case of an SIP server, after a call connection is established and a session between terminals is established, the terminals communicate directly with each other. Even a protocol A compliant terminal under the protocol AVoIP network 100 is treated as a protocol B compliant terminal if a contract is made in advance and registered as a subscriber terminal in the protocol B compliant server 201, and registration as a call terminal is performed. If you do, you will be able to talk.

  It should be noted that the above protocol conversion gateway is used for each network that connects to the protocol BVoIP network 200 from the outside, such as another protocol AVoIP network, protocol CVoIP network, etc., and operates the subordinate terminals as terminals under the protocol BVoIP network 200. Assume that apparatus 108 is provided.

  In the present embodiment, in order to prevent a large number of packets from being transmitted to the protocol B compliant server 201 at a time, individual networks in each VoIP network (including the VoIP network 100) other than the protocol B VoIP network 200. Assume that the protocol conversion gateway device 108 installed in the server executes packet retransmission control described later.

  Next, the operation of the embodiment configured as described above will be described in detail.

  FIG. 3 shows a sequence when a protocol A compliant terminal under the protocol AVoIP network 100 issues a registration request to the protocol B compliant server 201. The registration request is sent periodically for the purpose of maintaining the registration of the terminal as a call terminal.

  3 transmits a packet (registration packet) including a command (RRQ) indicating a registration request to the protocol A compliant server 107 at an arbitrary timing.

  Upon receiving the registration request command (RRQ), the protocol A compliant server 107 sets an expiration date and registers the terminal as a call terminal in the internal management table. The protocol A compliant server 107 further converts the registration request command (RRQ) received from the terminal into a REGISTER transmission request and transmits the REGISTER transmission request to the protocol B compliant server 201 of the protocol BVoIP network 200.

  A protocol conversion gateway device 108 is installed at a location where the LAN 101 is connected to an external network. When the protocol conversion gateway device 108 receives the REGISTER transmission request from the protocol A compliant server 107, the protocol conversion gateway device 108 changes the transmission source address, which is the identification number in the protocol AVoIP network 100, to the identification number in the protocol BVoIP network 200. Specifically, as shown in FIG. 2, if the identification number in the protocol AVoIP network 100 is “1000”, a process of changing to “05011111000” as the identification number in the protocol BVoIP network 200 is performed. As shown in FIG. 3, <SIP: 05011110000@voip.ne.jp> is set as the source address in the REGISTER packet header. Then, according to protocol B, “REGISTER” which is a registration request command in the protocol BVoIP network 200 is transmitted to the protocol B compliant server 201.

  In this embodiment, when the protocol conversion gateway device 108 transmits “REGISTER” to the protocol B compliant server 201, it immediately returns a REGISTER transmission request response to the protocol A compliant server 107 without waiting for the response. is doing. If the protocol conversion gateway device 108 holds the response to the protocol A compliant server 107 until the response from the protocol B compliant server 201 is received, the registration in the protocol A compliant server 107 is delayed when the response from the protocol B compliant server 201 is delayed. Even if the process ends normally, there will be a situation in which no response (RCF) is returned to the terminal. This is not preferable because there is a possibility that it is impossible to make a call on the protocol AVoIP network 100 for which registration is normally completed. Therefore, a REGISTER transmission request response is immediately returned to the protocol A compliant server 107, and a call on the protocol AVoIP network 100 is made possible regardless of whether the registration to the protocol B compliant server 201 is correct or not.

  If the protocol B compliant server 201 is operating normally without a congestion state, when receiving the REGISTER, the protocol B compliant server 201 sets an expiration date and registers the terminal as a call terminal in the internal management table. As shown in FIG. 3, when the network 109 is not congested, the protocol B compliant server 201 smoothly completes the registration process and returns 200 OK to the protocol conversion gateway device 108.

  Since the protocol conversion gateway device 108 has already returned the REGISTER transmission request response to the protocol A compliant server 107, the protocol conversion gateway device 108 does not return the same REGISTER transmission request response again.

  On the other hand, when packets are concentrated from each VoIP network to the protocol B compliant server 201 as in the case of failure recovery, a large number of packets waiting for retransmission are generated in the protocol conversion gateway device 108 of each VoIP network. .

  The protocol conversion gateway device 108 determines the maximum number of packets (for example, 2 packets) transmitted in a predetermined time (for example, 1 second) as a threshold value in advance. Therefore, when a packet transmission request exceeding the threshold is generated within a predetermined time, each packet exceeding the threshold is managed as a transmission reservation packet.

  In FIG. 3, packet retransmission control is performed in the protocol conversion gateway device 108 for each registered packet transmitted by the third terminal (identification number: 1002) and the fourth terminal (identification number: 1003) from the left. . Basically, a re-registration timer is set and retransmitted after the timer expires.

  As described above, when a packet transmission request exceeding the threshold value is generated within the predetermined time in the protocol conversion gateway device 108, the re-registration timer is set for each packet exceeding the threshold value, and the packet is retransmitted after the predetermined time elapses. By doing so, even if packets are concentrated at one time, they can be distributed. By executing such retransmission control in the protocol conversion gateway devices 108 of other VoIP networks, the effect of suppressing the concentration of packets to the protocol B compliant server 201 as a whole can be expected.

  By the way, if the same waiting time is uniformly set for all packets exceeding the threshold, the following problem may occur. If a large number of packets exceeding the threshold value are generated at a certain time, and if the same waiting time is set for all packets exceeding the threshold value at that time, a large number of packets are transmitted at the same time when the waiting time has elapsed. It becomes.

  In this embodiment, when a packet that has entered retransmission wait is expected to exceed the threshold again after the waiting time has elapsed, it is calculated in advance during the first retransmission control so that the transmission time is further distributed. The optimal re-registration timer for the packet is calculated separately.

  FIG. 4 is a functional block of the protocol conversion gateway device 108. The network control unit 111 performs network control between the LAN 101 side and the network 109 side. The call control / protocol conversion unit 112 is a part that performs call control based on the protocol A and the protocol B. The memory 113 stores the number conversion table shown in FIG. 2 and other various data (including parameters such as threshold values and fixed values). When a packet transmission request exceeding a threshold occurs within a predetermined time, the retransmission control unit 114 manages each packet exceeding the threshold as a transmission reservation packet, sets a re-registration timer for each transmission reservation packet, Control to retransmit after time elapses. The timer value calculation unit 115 is a part that calculates a timer value based on a calculation formula described later for each transmission reservation packet. The re-registration timer 116 is a timer in which the timer value calculated by the timer value calculation unit 115 is set. When the timer expires, a retransmission trigger is given to the retransmission control unit 114. Note that each functional block shown in FIG. 4 is a function realized by the CPU reading software from the ROM and executing instructions, but all or part of the functions may be constructed by hardware. .

  5 and 6 are flowcharts of retransmission control for calculating an optimum re-registration timer setting time. When the call control / protocol conversion unit 112 detects reception of the REGISTER transmission request (S101), the protocol conversion gateway device 108 compares the current “number of transmissions” with a predetermined “threshold value” (S101). S102). Here, the “number of transmissions” is the total number of registered packets transmitted within a predetermined time, and is a value that is reset to 0 when the predetermined time elapses as shown in FIG. The “threshold value” is the maximum value of registration packets to be transmitted within the predetermined time, and is set to 2 in this example. If the “number of transmissions” does not exceed “threshold” = 2 at the present time, it can be determined that the registration requests are not concentrated. Therefore, without setting the re-registration timer 116, the REGISTER ( Registration packet) is transmitted (S103). Then, the value of “number of transmissions” is incremented by one (S104).

On the other hand, if it is determined in step S102 that the “number of transmissions” currently exceeds “threshold” = 2 in step S102, the retransmission control unit 114 executes processing for setting the re-registration timer 116 (S105). That is, the timer value calculation unit 115 is instructed to calculate a timer value to be set in the re-registration timer 116 in order to control retransmission of the registration packet. The timer value is calculated according to the following formula.
Timer value = fixed value + α
Here, the fixed value is 60 seconds, but can be set according to the number of terminals accommodated. α is the number of transmission reservations / threshold (natural number less than 1 is 0).

  If the retransmission control is performed after a fixed value (60 seconds) has elapsed for a registration packet that exceeds the threshold value, the above-described inconvenience occurs. Therefore, in order to further distribute the transmission timing, the time added with α (= number of transmission reservations / threshold value) is a timer. I decided to use it as a value.

  The timer value calculated in this way is set in the re-registration timer 116 as the timer value of the registration packet. When the re-registration timer 116 is set without transmitting a registration packet, it is managed as a transmission reservation packet, and the “transmission reservation number” is incremented by one (S106).

  FIG. 6 shows an algorithm for determining the number of transmission reservations used for calculating the reset timing of the “transmission number” and the timer value. In the flowchart shown in FIG. 5, it is determined whether or not the number of transmission packets exceeds a threshold value within a predetermined time, but the predetermined time is set as a timer value for a predetermined time. Here, it is assumed that 1 second is set as the predetermined time timer value. That is, a restriction is imposed so that two or more packets are not transmitted per second. When this timer expires (S201), the "transmission number" is reset to 0, and the transmission reservation number is recalculated (S202). Specifically, the value obtained by subtracting the threshold from the current number of transmission reservations incremented in step S106 in FIG. 5 is set as the initial value of the “number of transmission reservations” used in step S105 in FIG. The “reserved number of transmissions” is incremented each time the initial value is passed through step S106, but after 1 second, a timer is set (S203), and the initial value of the “reserved number of transmissions” is set again in step S202 of FIG. It will be recalculated.

  If the current number of transmission reservations is not 2 or more in the calculation in step S202, the calculation result becomes negative. In such a case, the calculation result is set to 0.

  The relationship between the number of transmission reservations and the set value of the re-registration timer will be described with reference to FIG. In FIG. 7, 3 packets are input at time t1 (including transmission reservation). Since up to two packets are within the threshold, the packet is transmitted as it is, but the remaining one packet is subjected to retransmission control. At this time, at the present time, when a fixed value (60 seconds) has elapsed, it is only necessary to transmit the one packet. Since the number of transmission reservations is 1 and the threshold is 2, α = ½. Since α is a natural number and less than 1 is 0, finally α = 0, and timer value = fixed value (60 seconds) + α (0 seconds). Therefore, it is retransmitted after (t1 + 60 seconds).

  At time t2, 4 packets are input (including transmission reservation). Two packets are transmitted without being reserved for transmission (retransmission control), but the two packets become transmission reserved packets. If the number of reserved transmissions is up to 2, α = 0 in the same manner as described above, and is retransmitted after a fixed value (60 seconds).

  However, when the number of transmission reservations exceeds 3 packets as at time t3, α = 0 until the first and second 2 packets of the transmission reservations, and retransmission after a fixed value (60 seconds) elapses. However, for the third packet, α = 1 and is retransmitted after (60 seconds + 1 second). As a result, when three transmission reservations are made at time t3, the first two packets reserved for transmission are retransmitted 60 seconds later, and the remaining one packet is transmitted 61 seconds later. Will be suppressed.

  The packet retransmission control as described above is executed in the protocol conversion gateway device 108 of each VoIP network. As a result, even if a network failure that affects all VoIP networks occurs and registration requests are intensively generated from all terminals at the time of recovery, packets are transmitted so as to suppress the concentration of registration requests in each protocol conversion gateway device 108. Since retransmission control is performed, the overall network load can be reduced.

  In the above description, the concentration of registration packets has been mainly described. However, other messages can be similarly applied.

  In the present invention, even when registration packets and other messages (packets) are concentrated at one time, it is possible to set an optimal retransmission timing for load distribution for retransmission reservation packets, and packet transmission to other VoIP networks. It can be applied to a gateway device and a VoIP network system.

Network configuration diagram according to one embodiment Configuration diagram of table provided in protocol conversion gateway device Sequence diagram when multiple protocol A compliant terminals issue registration requests Functional block diagram of protocol conversion gateway device Flow chart of registration transmission processing by protocol conversion gateway device Flow chart of retransmission control to calculate the optimal re-registration timer setting time Diagram showing the relationship between the number of reserved transmissions and retransmission timing

Explanation of symbols

100 protocol AVoIP network 101 LAN
102, 103, 105 Protocol A compliant terminal 107 Protocol A compliant server 108 Protocol conversion gateway device 109 Network 111 Network control unit 112 Call control / protocol conversion unit 113 Memory 114 Retransmission control unit 115 Timer value calculation unit 116 Re-registration timer 200 Protocol BVoIP Network 201 Protocol B compliant server

Claims (5)

  When the number of packets received within a predetermined time exceeds the threshold, packets exceeding the threshold are managed as transmission reservation packets, and are retransmitted within a predetermined time by the retransmission control means for retransmitting when the timer value expires. Timer value calculation means for calculating the timer value for each transmission reservation packet so that the number of packets to be transmitted does not exceed the threshold value. 2. The gateway apparatus according to claim 1, wherein the timer value calculation means calculates a timer value for each transmission reservation packet based on timer value = fixed value + transmission reservation number / threshold.   3. A protocol conversion means for performing protocol conversion between protocol A and protocol B in order to operate a terminal device connected to a VoIP network of protocol A as a terminal device of a VoIP network of another protocol B. The gateway device described.   When a registration packet for requesting registration of a protocol A terminal to a call control server compliant with protocol B installed on the VoIP network of protocol B is received from a call control server compliant with protocol A installed on the VoIP network of protocol A, Sending a protocol-converted registration packet to a call control server compliant with protocol B and returning a response to the call control server compliant with protocol A without waiting for a response from the call control server compliant with protocol B The gateway device according to claim 3.   A call control server compliant with protocol A installed on a VoIP network of protocol A, a plurality of terminal devices compliant with protocol A, a call control server compliant with protocol B installed on a VoIP network of protocol B, and a protocol A plurality of terminal devices compliant with B, and a gateway device that connects the VoIP network of protocol A and the VoIP network of protocol B, performs protocol conversion between protocol A and protocol B, and transmits and receives packets. In the VoIP network system, when the number of packets received by the gateway device within a predetermined time exceeds a threshold, a packet exceeding the threshold is managed as a transmission reservation packet, and retransmission control means for retransmitting when the timer value expires, By retransmission control means VoIP network system comprising a timer value calculating unit number of packets to be retransmitted within a constant time to calculate the timer value for each transmission reservation packet so as not to exceed the threshold, the.

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