JP2005229378A - Repeater and control method thereof - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To enable a repeater to surely relay at least audio packets to an external device whether or not a congestion occurs in a communication network on a sending side, by effectively utilizing the band of the communication network. <P>SOLUTION: In a repeater 1 for relaying audio packets and the other packets to the external device through a repeating line 50 (communication network) on the sending side, a control unit 12 transmits a header compressed packet by compressing header data out of header data and audio data constituting audio packets to be sent in future in the case that the occurrence of congestion in the communication network is predicted. When restoration from congestion of the communication network is determined during transmission of the header compressed packets, the control unit 12 switches audio packets to be sent from the header compressed packets to full header packets in which the headers are not compressed, by omitting compression of header data of audio packets to be sent thereafter. The occurrence of congestion is predicted on the basis of a usage rate of a transmission buffer in a transmission/reception buffer 11. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to the technical field of a relay device, and more particularly to the technical field of a relay device such as a gateway device that relays packetized voice data to an external device via a communication network.

  In recent years, there has been an increasing demand for communicating various data such as image data, character data, and voice data. In particular, since voice data is required to have real-time properties, a header compression function is known as a method for efficiently transmitting and receiving packetized voice data (voice packets) via the Internet.

  The header compression function performs processing conforming to IETF (Internet Engineering Task Force) and RFC 2508 (Compressing IP / UDP / RTP Headers for Low-Speed Serial Links), thereby enabling IP / UDR / RTP (Internet Protocol / This is a process for compressing a User Datagram Protocol / Real-Time Transport Protocol) header part from a data size of usually 40 bytes to 2 bytes to 4 bytes.

  However, when this header compression function is employed in data transmission in a relay line (communication network) in which a transmission-side device and a reception-side device that are relay devices (gateway devices) are connected, the following problem occurs.

  That is, due to the characteristics of data transmission in the header compression function, there is a problem in that the continuity of individual packets is lost due to loss of header-compressed voice packets (hereinafter referred to as “header compressed packets”) due to errors or the like. There is. When such a problem occurs, the header compressed packet received by the receiving side device is re-established by re-establishing the continuity of each packet by retransmitting the voice packet from the transmitting side device through some procedure. , It is discarded at the receiving side device.

  Here, FIG. 5 is a diagram showing the structure of the data fields of the header compressed packet format and the uncompressed packet format of the voice packet.

  The header compression function excludes a field that does not change during data transmission in the IP / UDR / RTP header field and a field that changes by a fixed amount in each successive packet, and only when there is a change. This is a technique for compressing the data size of the header by encoding the difference. As a result of this header compression, a 40-byte uncompressed header (hereinafter referred to as a “full header packet”) is transmitted in a compressed state from 2 bytes to 4 bytes when transmitting audio data to be transmitted. Can do.

  When header compression is performed in this way, as described in, for example, Patent Documents 1 and 2, the receiving side device that receives the header compressed packet receives the first uncompressed header (full header packet). ), And the header field of the received header compressed packet is decompressed based on the primary difference of the field that increases linearly. Therefore, the receiving-side apparatus can perform decompression even when the compression / non-compression of the header part is switched during voice communication. However, since this receiving side apparatus decompresses the compressed header by the method described above, if the voice packet header compressed on the trunk line is lost and the continuity of the received packet is lost, the compressed header is lost. Can not be thawed. Therefore, when a packet loss occurs, the receiving side device transmits a signal requesting a header uncompressed packet to the transmitting side device. On the other hand, the receiving side apparatus discards the header compressed packet received until the header uncompressed packet is received.

  In general, since voice data is required to have real-time characteristics, loss of a voice packet on the transmission path as described above is likely to cause a phenomenon such as sound interruption and has a high influence on voice quality. For this reason, data communication using the header compression function is not problematic in an environment where there is no transmission error at all, but is considered not suitable for an environment where transmission errors such as packet loss are likely to occur.

  Also, in communication networks that transmit voice packets and general data such as images and characters in a mixed manner, it is common to prioritize voice packets over general data in order to ensure voice quality. is there. For this reason, when the trunk line is congested, the receiving side apparatus often discards the general data before the voice packet.

JP 7-95235 A (paragraph number 35, FIG. 1) JP 2002-26963 A (paragraph numbers 20 to 22)

  In the conventional method described above, the header portion of the voice packet can be changed to a full header packet or a header compressed packet by the header compression function, but is fixed. For this reason, if the header compression function is always effective, the header compression is performed even when the line usage rate is low and the bandwidth is sufficient, so that the voice quality is greatly affected when a voice packet loss occurs. On the other hand, when the header compression function is always disabled and data transmission is performed by a full header packet, general data discarded at the receiving side device when congestion occurs cannot be relieved, and further, the congestion state After the problem is solved, there is a problem that it takes time to recover to normal data transmission.

  In addition to the header compression function described above, as a conventional technique for effectively using the bandwidth of the relay line, a technique for limiting the number of voice calls to be connected when congestion occurs is known. However, in such a conventional method, since the number of voice calls to be connected is limited when congestion occurs, if there is an extremely large amount of general data such as images and characters to be transmitted, the number of voice calls that can be connected is considerably small. There is a possibility.

  Further, as a conventional technique for effectively using the bandwidth of the trunk line, a technique is known such as changing the voice encoding method used in the voice call to one having a high compression rate. However, in such a conventional method, the bandwidth used by the voice call is reduced, but the voice quality is worse than that of the voice call in the low-compression encoding method. Furthermore, since the compression rate is determined at the time of call connection in such a voice coding method, the coding method cannot be changed in the middle of a voice call that is already in a call.

  Therefore, the present invention provides a relay device that reliably relays at least a voice packet to an external device by effectively using the bandwidth of the communication network regardless of the occurrence of congestion in the communication network on the transmission side. And providing a control method thereof.

  In order to achieve the above object, a relay apparatus according to the present invention has the following configuration.

That is, a relay device that relays at least a voice packet to an external device via a communication network on the transmission side,
Of the header data and voice data constituting the voice packet, header compression means for compressing header data;
Network state determination means for predicting the occurrence of congestion in the communication network and determining recovery from the congestion state;
While the occurrence of congestion in the communication network is predicted, the operation mode of the header compression means is switched to the header compression mode for performing header compression for the voice packet to be transmitted thereafter, while the header compression mode When the recovery from the congestion state of the communication network is determined during transmission, the operation mode of the header compression means is changed from the header compression mode to the header for a voice packet to be transmitted thereafter. Control means for switching to full header mode without compression;
It is characterized by providing.

In a preferred embodiment, the network state determination means includes
Based on the usage rate of the transmission buffer of the relay device, it is preferable to perform prediction of congestion occurrence and determination of recovery from the congestion state.

The control means includes
When the relay device is activated, the operation mode of the header compression means is set to the full header mode, and switching control between the full header mode and the header compression mode is performed during the relay operation by the relay device.

Furthermore, in any of the above device configurations, when the relay device can relay packets other than the voice packet to the transmission side communication network,
The header compression unit and the control unit may process only the voice packet among the voice packet and the other packets.

  In another preferred embodiment, a first predetermined value (critical point B) serving as a determination criterion for switching from the full header mode to the header compression mode, and switching from the header compression mode to the full header mode. It is preferable to further include setting means capable of setting a second predetermined value (recovery point A) as a determination criterion for each port of the communication network.

  Then, in the use of the setting means, among the plurality of ports of the communication network, the port having a large number of voice channels is compared to the other ports having a small number of voice channels. 2 By setting a low value for both predetermined values, the switching timing between the full header mode and the header compression mode may be set earlier than that for the other ports.

  This object can also be achieved by a control method corresponding to the relay device having the above-described configurations.

  In addition, the same purpose stores the program code that can be realized by mounting the relay device having each of the above-described configurations and the control method thereof on the control unit (CPU) of the relay device, and the program code. This is also achieved by a computer-readable storage medium.

  According to the present invention described above, at least voice packets are reliably relayed to an external device by effectively using the bandwidth of the communication network regardless of the occurrence of congestion in the communication network on the transmission side. Provision of the relay device and its control method is realized.

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

  FIG. 1 is a block diagram showing a configuration example of a gateway device as an embodiment of a relay device according to the present invention.

  In the present embodiment, the gateway device 1 is capable of voice communication based on so-called VoIP (Voice over Internet protocol) technology, and has a one-to-one connection using a frame relay (FR) or a point-to-point protocol (PPP). This is a gateway device that transmits and receives voice data and general data via a relay line.

  The gateway apparatus 1 shown in FIG. 1 accommodates a data terminal 2 such as a personal computer (information processing apparatus), and a voice terminal 3 such as a PBX (Private Branch exchange) or a general telephone, and these accommodated terminals. The data output from the device is sent to the trunk line 50 so as to be transmitted to a device (not shown) (hereinafter also referred to as “reception side device”).

  In the present embodiment, the transmission data handled by the gateway device 1 to be relayed to the receiving side device is voice data (voice packets) and other general data (packets such as images and characters). That is, the gateway apparatus 1 is an example of ITU-T H.264. In accordance with the H.323 recommendation, voice communication and general data communication are performed by making a call connection with the receiving side apparatus via the relay line 50.

  As shown in FIG. 1, the gateway device 1 roughly includes an input / output device 10, a transmission / reception buffer 11, a control unit 12, a DSP (Digital Signal Processor) unit 13, a data interface 14, and a voice interface 15.

  The control unit 12 includes a buffer monitoring unit 121, a setting information management unit 122, a header compression / decompression processing unit 123, a voice call control unit 124 that performs call control such as call connection processing, and a data processing unit 125. Each unit (module) represents a processing unit including hardware including a CPU (Central Processing Unit), a memory, and the like (all not shown) and a software program executed by the CPU.

  More specifically, the buffer monitoring unit 121 monitors the state of the transmission / reception buffer 11 (details will be described later). The setting information management unit 122 is notified of information indicating the congestion status of the trunk line bandwidth (details will be described later). The header compression / decompression processing unit 123 compresses and decompresses the header given to each data packet. The voice call control unit 124 performs call control such as call connection processing. The data processing unit 125 performs protocol processing such as TCP (Transmission Control Protocol) and IP (Internet Protocol).

  The DSP unit 13 also includes an audio compression unit 131 that performs compression encoding and decoding of audio data, and an audio signal processing unit 132 that performs audio data processing such as RTP (Real-time Transport Protocol) protocol processing. .

  The transmission / reception buffer 11 has a transmission buffer (output buffer) and a reception buffer (input buffer) (not shown), and temporarily stores data packets to be transmitted / received. The input / output device 10 outputs the data packet received via the relay line 50 to the transmission / reception buffer 11 and sends the data packet output from the buffer to the relay line 50.

  Here, the operation when a voice call is performed in the gateway device 1 having the above-described device configuration will be outlined.

  The audio signal input via the audio interface 15 is subjected to encoding and protocol processing in the DSP unit 13. Thereafter, the control unit 12 performs IP (Internet Protocol) packetization, and each audio packet is subjected to header compression processing (when header compression is performed) and predetermined application processing, and then is sent via the transmission / reception buffer 11. Then, the data is transmitted from the input / output device 10 to the receiving side device (not shown) via the relay line 50. In addition, the voice packet received from the trunk line 50 side is decoded by a substantially reverse procedure in the above-described apparatus configuration, so that a voice signal is output to the voice terminal 3 via the voice interface 15.

  Further, general data (data such as images and characters) input from the data interface 14 is converted into IP packets by the control unit 12, and then passes from the input / output device 10 to the relay line 50 via the transmission / reception buffer 11. Is transmitted.

  In addition, in the process in which various processes are performed on the audio data and the general data in such a procedure, the buffer monitoring unit 121 transmits a transmission buffer (not specified) included in the transmission / reception buffer 11 by a timer interrupt counted by a CPU (not illustrated). The usage rate of the relay line 50 is predicted (determined) based on the usage rate, and information indicating the prediction result (hereinafter, information C) is sent to the setting information management unit 122. Notice.

  The setting information management unit 122 sets setting information about the header compression function (that is, information indicating whether or not to perform header compression) S to the header compression / decompression processing unit 123 when the gateway device 1 is activated.

  Also, when the setting information management unit 122 receives the information C from the buffer monitoring unit 121 during the data packet transmission operation by the gateway device 1, the setting information management unit 122 instructs the header compression / decompression processing unit 123 to execute the header compression function. The setting information S is changed according to the information C.

  Thus, the header compression / decompression processing unit 123 compresses or decompresses the header part of the voice packet to be transmitted / received according to the content of the setting information S of the header compression function acquired from the setting information management unit 122.

  Next, the setting value management table that the setting information management unit 122 has to perform the setting operation described above will be described.

  FIG. 2 is a diagram conceptually showing the data structure of the setting value management table included in setting information management unit 122 shown in FIG.

In this embodiment, the initial setting value of the setting information S of the header compression function is
Mode 1: always compresses the header of the voice packet to be transmitted (that is, always enabled during data transmission)
Mode 2: header compression of voice packets to be transmitted is not always performed (that is, always disabled during data transmission),
Mode 3: normally invalid but valid only during congestion (ie when congestion is expected),
Any one of the three modes can be selected, and each voice packet is “header compressed packet” when header compression is performed, and “full header packet” when header compression is not performed. Be treated.

  In the setting value management table of the setting information management unit 122, as shown in FIG. 2, setting information S indicating any one of the operation modes is stored in advance for each port (not shown) of the trunk line 50. Are stored as initial setting values. The setting information S is reflected from the setting information management unit 122 to the header compression / decompression processing unit 123 when the gateway device 1 is activated.

  In the set value management table, as shown in FIG. 2, for each port of the trunk line 50, a header compression function status indicating the current header compression function status and a Congestion_check indicating whether or not the trunk line is congested. A value (0 is a non-congested state, 1 is a congested state) is set. That is, during the operation of the gateway device 1, the buffer monitoring unit 121 performs the relay line port set to the above-described “mode 3” among the relay line ports in the setting value management table of the setting information management unit 122. As the information C, the header compression function status and the Congestion_check value are set. The set state is reflected on the header compression / decompression processing unit 123 by the setting information management unit 122.

  FIG. 3 is a flowchart of header compression control processing in the relay apparatus according to the present embodiment. Processing of a software program executed by a CPU (not shown) as a function of the buffer monitoring unit 121 in the control unit 12 shown in FIG. Represents a procedure.

  That is, the header compression control process shown in FIG. 3 detects the usage rate of the transmission buffer in the transmission / reception buffer 11 corresponding to the trunk line port set to the “mode 3” when the gateway device 1 is activated. This is a process of predicting and determining the congestion state of the bandwidth of the trunk line 50 based on the detected usage rate, and switching the necessity of header compression according to the prediction determination result.

  The header compression control process is started when the buffer monitoring unit 121 makes a timer interrupt during the operation of the apparatus. Then, the setting information management unit 122 controls the operation of the header compression / decompression processing unit 123 according to the state of the setting value management table (FIG. 2) updated by the buffer monitoring unit 121.

  That is, in FIG. 3, at A1, the usage rate of the transmission buffer is detected, and the process proceeds to A2.

  In A2, it is determined whether the usage rate detected in A1 exceeds a predetermined recovery point A (details will be described later with reference to FIG. 4) (A2-1). In this determination, a YES determination (usage rate ≧ In the case of the recovery point A), the Congestion_check value is determined (A2-2).

  In the determination of A2-2, when the Congestion_check value is 0, that is, when it is not in a congestion state (YES determination), the usage rate of the transmission buffer detected in A1 is a predetermined critical point B (> recovery point A : It is determined whether or not it exceeds the details (to be described later with reference to FIG. 4) (A2-3).

  In the determination of A2-3, when the usage rate detected in A1 exceeds the critical point B, it is predicted that a congestion state has occurred in the trunk line 50. Accordingly, in A2-4 to 6, header compression is performed for the port set to “mode 3” by referring to the initial setting value of the header compression function of each port in the setting value management table (FIG. 2). The function status is changed from the “invalid” state to the “valid” state, and the Congestion_check value is changed to 1. As a result, the set value management table (FIG. 2) is updated to a state representing the latest state of the trunk line 50 by the buffer monitoring unit 121. Then, the setting information management unit 122 instructs switching of the operation of the header compression / decompression processing unit 123 according to the setting value management table updated by the buffer monitoring unit 121.

  That is, the header compression / decompression processing unit 123 stops organizing the “full header packet” while organizing the individual audio packets to be transmitted in response to the change in the Congestion_check value as described above, A “header compressed packet” is organized by starting compression of the header portion from the control cycle.

  In the case of NO determination (Congestion_check value = 1) in the determination of A2-2, since it can be predicted that the congestion state is still occurring, the process returns. If the determination in A2-3 is NO (transmission buffer usage rate <critical point B), the process returns because it cannot be determined that congestion has occurred.

  On the other hand, if the determination in A2-1 is NO (usage rate <recovery point A), the congestion state that occurred before that is resolved, and the normal network state (a state in which sufficient bandwidth can be secured) is restored. It can be judged that Therefore, the following process A3 is performed.

  That is, in A3-1, it is determined whether the Congestion_check value is 1, that is, indicates a congestion state. If YES in this determination, each port of the set value management table (FIG. 2) is determined in A3-2-4. By referring to the initial setting value of the header compression function, the header compression function status is changed from the “valid” state to the “invalid” state for the port set to “mode 3”. Change the Congestion_check value to 0.

  In response to the change in the Congestion_check value, the header compression / decompression processing unit 123 stops organizing the “header compressed packet” while organizing the individual audio packets to be transmitted, and starts “full” from the control cycle thereafter. Organize “header packets”.

  If the determination in A3-1 is NO (Congestion_check value = 0), the network is determined to be in a normal state with no congestion, and the process returns.

  Next, the recovery point A and the critical point B referred to as the determination criteria in the header compression control process (FIG. 3) described above will be described with reference to FIG.

  FIG. 4 is a diagram showing the relationship between the usage rate of the transmission buffer in the transmission / reception buffer 11 shown in FIG.

  As can be seen from the description of the header compression control process described above, in this embodiment, the critical point B is a transmission buffer usage rate (b%) that serves as a reference for determining that a congestion state has occurred in the trunk line 50. It is.

  On the other hand, the recovery point A is a use rate (a%) of a transmission buffer serving as a reference for determining that a congestion state does not occur in the trunk line 50 and a normal network state (a state where a sufficient bandwidth can be secured). ). Therefore, in the header compression control process described above, if the buffer usage rate drops to a% in response to the congestion state that has occurred during the operation of the gateway device 1 being congested, congestion occurs at that time. It is determined that the condition has been resolved. As an example, the buffer usage rate is monitored by the buffer monitoring unit 121 performing a timer interrupt.

  The gateway device 1 according to the present embodiment described above detects the usage rate of the transmission buffer in the transmission / reception buffer 11, and performs prediction determination of the congestion state of the bandwidth of the relay line 50 based on the detected usage rate. Further, when it is predicted that a congestion state will occur as a result of the prediction determination, the gateway device 1 transmits a voice packet to be transmitted in relation to a voice call already in progress at that time and a voice call connected thereafter. Is a “header compressed packet”, on the other hand, if it can be determined that the congestion state has not occurred or has recovered from the congestion state that has occurred, the voice packet to be transmitted is determined as a “full header packet”.

  As described above, according to this embodiment in which the necessity of header compression of the voice packet is switched according to the bandwidth state of the trunk line 50, the header compressed packet can be organized before the congestion state occurs. The voice data included in each voice packet is not affected at all by the necessity switching of the header compression function. Therefore, even when a congestion state occurs, the deterioration of sound quality is kept to a minimum, and general data is discarded at the reception side device by sending a full header packet from the transmission side device even when congestion occurs, As a result, the conventional problem that data transmission is delayed can be solved.

  In particular, in the present embodiment, the above-described header compression control process (FIG. 3) is performed in the transmission side apparatus (gateway apparatus 1) connected to the upstream side of the trunk line 50, and this processing is performed in the transmission side apparatus. This is a closed configuration. For this reason, a conventional system configuration in which a data packet is discarded due to the occurrence of congestion is fed back from the reception side device to the transmission side device, and recovery processing is started as a trigger (for example, Patent Document 1 described above) Compared with 2 and the like, the unique effect that the bandwidth of the relay line can be used efficiently and the general data packet to be discarded can be minimized to ensure optimum and quick data transmission. obtain.

  In this embodiment, the usage rate of the transmission buffer of the transmission side device is adopted as one method for predicting the bandwidth state of the trunk line 50. However, the transmission side device may be able to predict the state of the data transmission target network. Any method can be employed.

  In the above-described embodiment, the case has been described in which the gateway device 1 handles voice data (voice packets) and other general data (general data packets) such as images and characters. It is not limited. For example, when only voice data (voice packets) is handled, in this case as well, if congestion is predicted, header transmission is performed to secure the bandwidth to ensure reliable transmission of voice calls. In addition, it is possible to minimize the deterioration of the voice quality. That is, at least a voice packet can be reliably relayed to an external device by effectively using the bandwidth of the communication network regardless of the occurrence of congestion in the communication network on the transmission side.

<Modification of Embodiment>
In the preferred modification of the present embodiment described above, the recovery point A and the critical point B can be set for each port. By adopting such a configuration, it is possible to more appropriately cope with the environment of each network to which the gateway device 1 is connected.

  That is, the bandwidth used per channel for voice calls is generally fixed. Further, the bandwidth of general data such as images and characters fluctuates including burst increases. Therefore, in this modification, by paying attention to the difference in the line speed of each port, the port having a relatively large number of accommodated voice channels (in other words, the number of accommodated voice channels is larger than the line speed, In the case of a port having a large proportion of voice data in the transmission data), both the recovery point A (second predetermined value) and the critical point B (first predetermined value) are compared with a port having a small number of voice channels. Set lower.

  More specifically, when the number of voice channels accommodated is relatively large, the effect of performing header compression on the voice packet to be transmitted is great. For this reason, if such a setting is adopted, in addition to the effect of the above-described embodiment, the “full header mode” can be switched to the “header compression mode” when the transmission buffer usage rate is relatively low. It is possible to transmit more and more reliably.

  On the other hand, when the number of voice channels accommodated is relatively small, the effect of header compression into voice packets to be transmitted is small. For this reason, if such a setting is adopted, in addition to the effect of the above-described embodiment, since the transmission buffer usage rate becomes relatively high, the “full header mode” is switched to the “header compression mode”. The effect that the deterioration of the voice quality during the execution of the “compression mode” can be minimized.

  Note that the present invention described by taking the above-described embodiment as an example supplies the above-described gateway apparatus 1 with a computer program capable of realizing the functions of the flowchart referred to in the description, and then reads it out to the CPU of the apparatus. To achieve. Further, the computer program supplied in the apparatus may be stored in a storage device such as a readable / writable memory.

  In the above-described case, the computer program can be supplied to each apparatus by a method of installing the apparatus via various recording media such as a floppy disk or a communication line such as the Internet. Currently, a general procedure can be adopted, such as a method of downloading from the outside via the external method. In such a case, the present invention is constituted by the code of the computer program or a storage medium.

It is a block diagram which shows the structural example of the gateway apparatus as embodiment of the relay apparatus which concerns on this invention. It is a figure which shows notionally the data structure of the setting value management table which the setting information management part 122 shown in FIG. 1 has. It is a flowchart of a header compression control process in the relay device according to the present embodiment. It is a figure which shows the usage rate of the transmission buffer in the transmission / reception buffer 11 shown in FIG. It is a figure which shows the structure of the data field of the header compression packet format of an audio | voice packet, and an uncompressed packet format.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Gateway apparatus 2 Data terminal 3 Voice terminal 10 Input / output device 11 Transmission / reception buffer 12 Control unit 13 DSP (Digital Signal Processor) unit 14 Data interface 15 Voice interface 50 Relay line 121 Buffer monitoring part 122 Setting information management part 123 Header compression / decompression Processing unit 124 Voice call control unit 125 Data processing unit 131 Voice compression unit 132 Voice signal processing unit

Claims (10)

A relay device that relays at least a voice packet to an external device via a communication network on the transmission side;
Of the header data and voice data constituting the voice packet, header compression means for compressing header data;
Network state determination means for predicting the occurrence of congestion in the communication network and determining recovery from the congestion state;
While the occurrence of congestion in the communication network is predicted, the operation mode of the header compression means is switched to the header compression mode for performing header compression for the voice packet to be transmitted thereafter, while the header compression mode When the recovery from the congestion state of the communication network is determined during transmission, the operation mode of the header compression means is changed from the header compression mode to the header for a voice packet to be transmitted thereafter. Control means for switching to full header mode without compression;
A relay device comprising: The network state determining means includes
The relay apparatus according to claim 1, wherein prediction of congestion occurrence and determination of recovery from a congestion state are performed based on a usage rate of a transmission buffer included in the relay apparatus. The control means includes
When the relay device is activated, the operation mode of the header compression unit is set to the full header mode, and switching control between the full header mode and the header compression mode is performed during the relay operation by the relay device. The relay apparatus according to claim 1 or 2. The relay device can also relay packets other than the voice packet to the communication network on the transmission side,
4. The relay apparatus according to claim 1, wherein the header compression unit and the control unit process only the voice packet among the voice packet and the other packets. A first predetermined value serving as a determination criterion for switching from the full header mode to the header compression mode and a second predetermined value serving as a determination criterion for switching from the header compression mode to the full header mode are defined in the communication network. The relay apparatus according to claim 1, further comprising setting means that can be set for each port. A control method for a relay device that relays at least a voice packet to an external device via a communication network on a transmission side,
A network state determination step for predicting the occurrence of congestion in the communication network and determining recovery from the congestion state;
In response to a predicted occurrence of congestion in the communication network, a header compressed packet is obtained by compressing the header data out of the header data and the voice data constituting the voice packet with respect to a voice packet to be transmitted thereafter. On the other hand, during the transmission of the header compressed packet, the header data is not compressed for the voice packet to be transmitted after that when the recovery from the congestion state of the communication network is determined. A switching step of switching a voice packet to be transmitted from the header compressed packet to a full header packet without header compression;
A control method for a relay device, comprising: In the network state determination step,
7. The method of controlling a relay apparatus according to claim 6, wherein the prediction of congestion occurrence and the determination of recovery from the congestion state are performed based on a usage rate of a transmission buffer included in the relay apparatus. The relay device can also relay packets other than the voice packet to the communication network on the transmission side,
8. The relay apparatus control method according to claim 6, wherein the header compression unit and the control unit process only the voice packet among the voice packet and the other packets. A first predetermined value serving as a determination criterion for switching from the full header mode to the header compression mode and a second predetermined value serving as a reference for switching from the header compression mode to the full header mode are determined by the communication network. The relay apparatus control method according to claim 6, further comprising a setting step of setting for each port. In the setting step,
Of the plurality of ports of the communication network, a port having a large number of voice channels accommodated has a lower value than both the first and second predetermined values compared to other ports having a small number of voice channels. 10. The relay device control method according to claim 9, wherein the switching timing between the full header mode and the header compression mode is set earlier than the other ports by setting.

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