JP2009105952A - Packet repeater and packet repeating method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a packet repeater for preventing a packet sent from a terminal where a session has been established from being discarded and for improving the throughput efficiency of the packet. <P>SOLUTION: The packet repeater 10 includes a packet repeating part 18 for repeating a packet sent from a terminal where a session has been established in a use band required for the session. The packet repeater 10 further includes: a session control information analyzing part 12 for specifying the usage band by analyzing session control information sent from the terminal; and a band correction part 14 for correcting the use band specified by the session control information analyzing part 12 based on the amount of header information when the packet is repeated. The packet repeating part 18 repeats the packet sent from the terminal within the band corrected by the band correction part 14. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a packet relay device that relays a packet via a network.

  2. Description of the Related Art Conventionally, a packet relay apparatus suitable for maintaining the quality of service (Quality of Service) when providing a service by real-time communication related to voice, video, etc. via the Internet is known. For example, when a session for transmitting / receiving RTP packets compliant with RTP (Real-time Transport Protocol) used for real-time communication is established, a conventional packet relay device secures the bandwidth required for the established session. By maintaining the quality of service.

  More specifically, a conventional packet relay device includes a reservation reception control unit that assigns a use band to a scheduler queue for transmitting a packet to an adjacent packet relay device, and has a control called RTSP (RealTime Streaming Protocol). When a packet that conforms to the protocol for the session is received, the bandwidth used for the session is extracted from the received packet and registered in the reservation reception control unit. The reservation reception control unit can guarantee bandwidth based on the bandwidth used. Is known (see, for example, Patent Document 1).

Further, the packet relay apparatus described in Patent Document 1 allocates a minimum rate as a use band necessary for a session to a scheduler queue when a session establishment is requested, and has a margin based on overhead associated with RTP packets. The maximum rate can be assigned as the used bandwidth. For example, the overhead is RTP packets transmitted over the Internet, so information such as UDP (User Datagram Protocol), IP (Internet Protocol) headers added to RTP packets and headers defined by lower-layer protocols than IP It is.
JP 2003-158543 A

  The present invention provides a method for identifying information relating to a used band from SDP (Session Description Protocol) syntax.

The present invention receives a packet including session control information for establishing the session communicated between terminals required to establish the session, and is necessary for the session based on the session control information included in the packet. A session control information analysis unit (12) for obtaining a usable bandwidth, and a packet relay unit (18) for relaying packets of the session with the bandwidth necessary for the session obtained by the session control information analysis unit. In the packet relay device (10), the session control information analysis unit uses an SDP (Session Description Protocol) syntax included in the received packet as the session control information, and uses necessary for the session based on the SDP syntax. Seeking bandwidth And butterflies.
Further, according to the present invention, the packet relay device further includes a session database (13), and the session control information analyzing unit includes a packet including an INVITE message of a SIP (Session Initiation Protocol) message or a response message corresponding to the INVITE message. Is generated from the information included in the INVITE message or the response message, and information on the used bandwidth specified from the SDP syntax is added to the session data and stored in the session database. A use band necessary for the session is obtained based on information on the use band.
Furthermore, the present invention is characterized in that in the packet relay device, the session data includes a source IP address, a source port number, a destination IP address, a destination port number, and a protocol.
Further, according to the present invention, the packet relay device further includes a session database (13), and the session control information analysis unit analyzes the INVITE message when receiving a packet including the INVITE message of the SIP message. Session data including a source IP address, protocol, and source port number is generated and stored in the session database. When a packet including a response message corresponding to the INVITE message is received, the session data is stored in the session database. In addition, information related to the used bandwidth specified from the destination IP address, the destination port number, and the SDP syntax is added to the session data corresponding to the response message, and based on the information related to the used bandwidth And obtaining the bandwidth use necessary cushion.
In the present invention, the information on the used band includes a bit rate, and the session information analysis unit obtains a used band necessary for the session from the bit rate.
Alternatively, in the present invention, the information on the use band includes information on a coding standard and a sampling rate, and the session information analysis unit includes information on the coding standard, a sampling rate, and a bit rate prepared in advance. The bandwidth used for the session is obtained by using a bit rate correspondence table in which
Alternatively, in the present invention, the information on the use band includes information on a coding standard, and the session information analysis unit uses the maximum bit defined in the coding standard from the information on the coding standard. The use band required for the session is obtained by specifying the rate.
In addition, the present invention receives a packet including session control information for establishing the session communicated between terminals that are required to establish a session, and based on the session control information included in the packet, the session A packet relay method comprising: a first step of obtaining a used bandwidth necessary for the session; and a second step of relaying a packet of the session with the used bandwidth required for the session obtained in the first step. The first step is characterized in that an SDP (Session Description Protocol) syntax included in the received packet is used as the session control information, and a use band necessary for the session is obtained based on the SDP syntax.
In the packet relay method of the present invention, when the first step further receives an INVITE message of a SIP (Session Initiation Protocol) message or a packet including a response message corresponding to the INVITE message, the INVITE message or the Generating session data from information included in the response message, adding information on the used bandwidth specified from the SDP syntax to the session data and storing the information in the session database (13), and And determining a bandwidth to be used for the session based on the information.
In the packet relay method of the present invention, the session data includes a source IP address, a source port number, a destination IP address, a destination port number, and a protocol.
Further, in the packet relay method of the present invention, when the first step further receives a packet including the INVITE message of the SIP message, the source IP address, the protocol, and the transmission source are analyzed by analyzing the INVITE message. Generating session data including a port number and storing it in the session database (13), and when receiving a packet including a response message corresponding to the INVITE message, corresponding to the response message stored in the session database Adding to the session data information related to a used bandwidth specified from a destination IP address, a destination port number, and the SDP syntax, and obtaining a used bandwidth necessary for the session based on the information related to the used bandwidth. Characterized in that it comprises a that stage.
Further, in the packet relay method of the present invention, the information on the used bandwidth includes a bit rate, and the step of obtaining the used bandwidth necessary for the session includes obtaining the used bandwidth necessary for the session from the bit rate. Features.
Alternatively, in the packet relay method of the present invention, the information on the used band includes information on a coding standard and a sampling rate, and the step of obtaining the used band necessary for the session includes a coding standard prepared in advance. And using the bit rate correspondence table in which the sampling rate and the bit rate correspond to each other, the use band necessary for the session is obtained.
Alternatively, in the packet relay method of the present invention, the information on the used band includes information on a coding standard, and the step of obtaining the used band necessary for the session is performed based on the coding standard information. The use band required for the session is obtained by specifying the maximum bit rate specified in the standard.

  According to the present invention, there is provided a method for specifying information related to a used band from SDP (Session Description Protocol) syntax.

However, in the conventional packet relay device described above, if the difference between the minimum rate and the maximum rate in the bandwidth used for the session is reduced, the RTP packet is discarded when the overhead size related to the RTP packet is large. Therefore, if the difference between the minimum rate and the maximum rate is increased too much, there remains a problem that the packet throughput efficiency is lowered.
The invention according to Japanese Patent Application No. 2006-99112 (hereinafter referred to as the original application) was made to solve this problem, and prevents the packet transmitted from the terminal with which the session has been established from being discarded. An object of the present invention is to provide a packet relay device that improves the throughput efficiency of the packet.
The packet relay device of the invention according to the original application is transmitted from the terminal in a packet relay device having a packet relay unit that relays a packet transmitted from a terminal with a session established in a use band necessary for the session. A session control information analysis unit that analyzes session control information to identify the used bandwidth, and corrects the used bandwidth identified by the session control information analyzing unit based on a header information amount when the packet is relayed A band correction unit, and the packet relay unit relays a packet transmitted from the terminal in a band corrected by the band correction unit.
With this configuration, since the used bandwidth necessary for the session is corrected based on the amount of header information when the packet transmitted from the terminal is relayed, and the packet is relayed in the corrected bandwidth, the terminal from which the session is established It is possible to prevent the transmitted packet from being discarded and to improve the packet throughput efficiency.
Further, in the packet relay device of the invention according to the original application, the band correction unit has a configuration for correcting based on a header information amount obtained from header information added when the session control information is received. .
With this configuration, an accurate amount of header information can be obtained, so that packet discard can be reliably prevented.

Further, in the packet relay apparatus according to the invention according to the original application, the band correction unit corrects based on a header information amount corresponding to a port to which the packet is transmitted when the packet transmitted from the terminal is relayed have.
With this configuration, an accurate amount of header information can be obtained, so that packet discard can be reliably prevented.

Further, in the packet relay device of the invention according to the original application, the session control information analysis unit has a configuration for specifying the used band by the band information included in the session control information.
With this configuration, since the bandwidth to be used is specified based on the bandwidth information included in the session control information, accurate header information is obtained, and packet discard can be reliably prevented.

Further, in the packet relay device of the invention according to the original application, the session control information analysis unit, when the bandwidth information does not exist in the session control information, based on the coding type information included in the session control information It has a configuration for obtaining information.
With this configuration, since the band information is obtained based on the encoding type information included in the session control information, it is possible to specify the used band even if no band information exists in the session control information.

  The invention according to the original application provides a packet relay device that prevents the discard of a packet transmitted from a terminal with a session established and improves the throughput efficiency of the packet.

  Hereinafter, a packet relay device according to an embodiment of the present invention will be described with reference to the drawings.

  FIG. 1 shows a configuration diagram of a communication system according to an embodiment of the present invention. As shown in FIG. 1, terminals 21 and 22 are connected to a provider network 9 provided by an ISP (Internet Service Provider), and terminals 31 and 32 are connected to a network 8. The provider network 9 and the network 8 are connected via a packet relay device 10.

  The terminals 21, 22, 31, and 32 are, for example, IP telephone terminals that transmit and receive IP-compliant packets (hereinafter referred to as IP packets). Of course, the terminals 21, 22, 31, and 32 are not limited to IP telephone terminals, but may be terminals that transmit and receive packets by real-time communication such as videophones, terminals that transmit and receive packets by streaming audio and video distribution, servers, and the like. .

  FIG. 2 is a sequence diagram showing a procedure based on SIP (Session Initiation Protocol) when making an IP phone call between the terminal 21 and the terminal 31. As shown in FIG. 2, after a SIP message such as INVITE is transmitted / received, a session for an IP phone or the like is established. Note that when performing a procedure compliant with SIP, the packet relay device 10 identifies a used bandwidth necessary for the session from the SIP message, and relays the packet using the used bandwidth.

  After the session is established, RTP packets for transferring voice data in real time are transmitted and received between the terminal 21 and the terminal 31. For example, an RTP packet transmitted from the terminal 21 is relayed by the packet relay device 10 and received by the terminal 31 via the network 8.

  When the packet relay apparatus 10 receives the RTP packet transmitted from the terminal 21, the packet relay apparatus 10 secures a use bandwidth for the received RTP packet and header information related to the RTP packet and relays it to the network 8.

  Hereinafter, a packet relay device according to an embodiment of the present invention will be described. FIG. 3 shows a configuration diagram of the packet relay apparatus according to the embodiment of the present invention.

  The packet relay apparatus 10 includes a processor (not shown) such as a CPU, memories such as a RAM and a ROM, and a network interface 20 that processes packets transmitted and received from a network. Note that the network interface 20 transmits and receives packets via a port serving as a gateway to the network.

  As shown in FIG. 3, the packet relay apparatus 10 includes a packet classification unit 11, a session control information analysis unit 12, a session database 13, a bandwidth correction unit 14, a reservation reception control unit 15, a traffic management database 16, and a buffer queue 17. And a packet relay unit 18.

  The packet classification unit 11, the session control information analysis unit 12, the session database 13, the bandwidth correction unit 14, the reservation reception control unit 15, the traffic management database 16, and the packet relay unit 18 are, for example, programs executed by a processor. It may be a module or an integrated circuit.

  The packet classification unit 11 identifies a packet received via the network interface 20 with reference to the flow table 19 and queues the packet in one of a plurality of buffer queues 17 based on the identification result. ing. Further, when the packet classification unit 11 receives a packet and refers to the flow table 19, if there is no flow entry to which the packet belongs in the flow table 19, the destination IP address, source IP address, protocol The destination port number and the source port number are registered.

  For example, the flow table 19 is data in which a queue ID is specified using a destination IP address, a source IP address, a protocol, a destination port number, and a source port number as keys as shown in FIG. Here, the queue ID is identification information used inside the packet relay apparatus of the present invention in order to identify each queue.

  When the packet classification unit 11 receives a packet including session control information such as an SIP message for establishing a session, the packet classification unit 11 copies the packet including the received session control information. In addition to outputting to the control information analysis unit 12, other copied packets are queued in the buffer queue 17.

  The session control information analyzing unit 12 analyzes the session control information. For example, the session control information analyzing unit 12 analyzes information included in an INVITE message that is a SIP message or a response message of the INVITE message, and determines a use band from these SIP messages. It has come to identify. In addition, the session control information analysis unit 12 stores session data including a used bandwidth necessary for the session in the session database 13.

  The band correction unit 14 corrects the used band specified by the session control information analysis unit 12 based on the amount of header information of the packet. For example, when the packet relay apparatus 10 transmits a packet related to real-time communication (payload) in accordance with Ethernet (registered trademark), IP, UDP, RTP, the packet shown in FIG. In order to transmit in the bandwidth used for the session, the bandwidth correction unit 14 calculates the amount of header information of the packet to be transmitted from the information registered in the flow table 19, and uses Ethernet (registered) for the payload information. (Trademark), IP, UDP, and RTP, the use band is corrected in consideration of 54 bytes, which is the total amount of header information.

Further, as shown in FIG. 5B, when the packet relay apparatus 10 transmits a packet by a communication method in which a gap or preamble exists, the bandwidth correction unit 14 further uses the gap or preamble in consideration. The band may be corrected.
That is, the header information described here is not only information added as a header when composing a packet, but information added as a footer, or is not directly recognized by a user such as a gap or a preamble. However, it may include those necessary for performing communication on the communication standard to be used and affecting the actual bandwidth.

  The reservation acceptance control unit 15 determines whether or not a session can be accepted with the correction band corrected by the band correction unit 14. If the session can be accepted, a buffer for queuing packets based on the correction band One queue is generated in the queue 17 and the corrected bandwidth is registered in the traffic management database 16.

  In the traffic management database 16, a correction band is registered for each queue ID of the flow table 19. In the example shown in FIG. 6, the correction band set for each queue ID in the flow table 19 is registered in a table format. For example, the bandwidth assigned to queue ID 1 is a session packet rate of 50 packets (packet / sec) and 160 bytes per packet, so the session bit rate for real-time communication is 64K (bit / sec). The band correction unit 14 corrects the 160 bytes by adding the header information amount of Ethernet (registered trademark), IP, UDP, and RTP, and 54 bytes.

For example, the session control information analysis unit 12 is configured to specify a use band by a bit rate and a packet rate that are band information from the SIP message, and the band correction unit 14 is a bit rate that is a use band necessary for the session. When the packet rate is expressed as Rd (bit / sec) and Rp (packet / sec) and the header information amount of the packet is expressed as Ph (byte), the correction band is calculated by the following formula 1.
((Rd / (Rp * 8)) + Ph) * Rp * 8 = correction band Equation 1

  The packet relay unit 18 is configured to output the packets queued in the buffer queue 17 to the network interface 20 based on the corrected bandwidth registered in the traffic management database 16. For example, the packet relay unit 18 outputs 50 packets (214 bytes) queued in the queue having the queue ID 1 per second.

  Note that the queue with the queue ID 0 shown in FIG. 6 is a best-effort queue, and the packet relay unit 18 sets the queue ID to 0 when no packet is queued in the queue with the queue ID of 1 or more. Controls such as outputting packets queued in the queue. In addition, the total bandwidth of queues with a queue ID of 1 or more is allowed up to a predetermined bandwidth, and the reservation acceptance control unit 15 adds the correction bandwidth when a new session is accepted and the total bandwidth at the current stage. If the determined bandwidth exceeds the predetermined bandwidth, it is determined not to accept the session.

  The operation of the packet relay apparatus according to the embodiment of the present invention configured as described above will be described below with reference to the drawings. FIG. 7 is a flowchart showing the operation of the packet relay apparatus according to the embodiment of the present invention.

First, when receiving a packet (S1), the packet classification unit 11 checks whether or not the received packet includes an INVITE message of a SIP message (S2). When the received packet includes the INVITE message, the session control information analysis unit 12 is configured by analyzing the information included in the INVITE message, by information regarding the transmission source IP address, the protocol, the transmission source port number, the used bandwidth, and the like. Session data to be generated is generated, and the generated session data is stored in the session database 13 (S3).
Further, when the packet classification unit 11 receives a packet and refers to the flow table 19, if there is no flow entry to which the packet belongs in the flow table 19, the destination IP address, source IP address, protocol The destination port number and the source port number are registered.

  Further, when the received packet does not include the INVITE message, the packet classification unit 11 confirms whether or not the received packet includes a response message corresponding to the INVITE message (S4). When the received packet does not include the response message (200 OK), the packet classification unit 11 refers to the flow table 19 to identify the packet, and the packet is stored in any of the plurality of buffer queues 17 based on the identification result. Queuing

  When the received packet includes a response message, the session control information analysis unit 12 refers to the session database 13 and confirms whether there is session data corresponding to the response message (S5). When there is session data corresponding to the response message, information on the destination IP address, the destination port number, and the used bandwidth is added to the session data and stored in the session database 13 (S6).

  The session control information analysis unit 12 obtains the bit rate and the packet rate, and the band correction unit 14 obtains the header information amount of the packet with reference to the flow table 19 and calculates the correction band based on Equation 1 (S7). .

  For example, the bandwidth correction unit 14 may obtain the header information amount from the header information added when transmitting the SIP message. Further, the bandwidth correction unit 14 has correspondence information that associates the port with the header information amount in advance, and when the packet is transmitted from the terminal, the port to which the packet is to be transmitted when the packet is relayed And corresponding header information amount may be obtained. For example, communication conforming to the VLAN standard and communication conforming to a speeded up standard such as 100BASE-T are performed corresponding to the port, and the amount of header information varies depending on such a standard.

  Note that the SIP message does not necessarily include the bit rate or the packet rate, and there is a combination pattern regarding the presence / absence of information regarding the used bandwidth as shown in FIG. In addition, the information regarding a use band is specified from the SDP (Session Description Protocol) syntax of the received SIP message, for example.

  Information on bandwidth used includes coding standard information, which is coding type information, real-time communication coding standard information, real-time communication sampling rate, packet rate (packet / sec), bit rate (bit / sec), etc. Session control information When the analysis unit 12 receives a SIP message, the analysis unit 12 checks whether the received SIP message has such information. The encoding standard is ITU-T recommendation G.264. 711 series and H.264. Standards such as 261 to 263.

  For example, in the case of pattern 1, the session control information analysis unit 12 can extract all the information of the encoding standard, the sampling rate, the packet rate, and the bit rate from the SIP message, so that the bandwidth correction unit 14 extracts the extracted packet rate, The correction band is calculated from the bit rate using Equation 1.

  In the case of pattern 2, the session control information analysis unit 12 can extract only the information of the coding standard, the sampling rate, and the packet rate from the SIP message. That is, the bit rate is not included in the SIP message. In this case, the session control information analysis unit 12 has a bit rate correspondence table that associates the coding standard information with the sampling rate and bit rate of real-time communication in advance. The bit rate is obtained using the rate correspondence table, and the band correcting unit 14 calculates the corrected band using Expression 1 from the extracted packet rate and the obtained bit rate.

  In the case of pattern 3, since the packet rate and the bit rate are not included in the SIP message, the session control information analysis unit 12 uses the bit rate correspondence table described above from the coding standard information and the sampling rate. And the packet rate is set to the maximum rate such as 50 (packet / sec).

  In the case of pattern 4, since only the coding standard is included in the SIP message, the session control information analysis unit 12 specifies the maximum bit rate specified in the coding standard and sets the packet rate to 50 (packet / sec). Etc. to the maximum rate.

  The reservation acceptance control unit 15 generates a queue for queuing packets based on the corrected bandwidth (S8), and registers the corrected bandwidth in the traffic management database 16 (S9).

  In the embodiment of the present invention, since a queue is generated when requesting establishment of a session, the correspondence between the session and the queue is 1: 1, but in the present invention, the correspondence between the session and the queue is Is not limited to 1: 1.

  As described above, the packet relay apparatus according to the embodiment of the present invention corrects the used bandwidth necessary for the session based on the header information amount when relaying the packet transmitted from the terminal, and the corrected bandwidth Since the packet is relayed by this, discarding of a packet transmitted from a terminal with which a session is established can be prevented and the throughput efficiency of the packet can be improved.

  As described above, the packet relay apparatus according to the present invention has an effect of preventing the discard of a packet transmitted from a terminal with which a session is established and improving the throughput efficiency of the packet. It is useful as a router, shaper, switch, or the like that performs bandwidth control when relaying the network.

Configuration diagram of a communication system according to an embodiment of the present invention Sequence diagram showing the procedure based on SIP when making an IP phone call between terminals Configuration diagram of a packet relay device according to an embodiment of the present invention The figure showing the flow table which concerns on embodiment of this invention Configuration diagram of a packet according to an embodiment of the present invention A diagram showing the correspondence between queue IDs and correction bands in a table format The flowchart showing operation | movement of the packet relay apparatus concerning embodiment of this invention. A diagram showing a combination pattern related to the presence or absence of information about the bandwidth used

8 network 9 provider network 10 packet relay device 11 packet classification unit 12 session control information analysis unit 13 session database 14 bandwidth correction unit 15 reservation reception control unit 16 traffic management database 17 buffer queue 18 packet relay unit 19 flow table 20 network interface 21, 22, 31, 32 terminals

Claims (14)

A packet including session control information for establishing the session communicated between terminals that are required to establish a session is received, and a bandwidth required for the session is determined based on the session control information included in the packet. A desired session control information analysis unit (12);
In a packet relay device (10) comprising a packet relay unit (18) that relays a packet of the session in a use band required for the session determined by the session control information analysis unit,
The session control information analyzing unit uses an SDP (Session Description Protocol) syntax included in the received packet as the session control information, and obtains a use band necessary for the session based on the SDP syntax. Packet relay device. The packet relay device further comprises a session database (13),
The session control information analysis unit
When a packet including an INVITE message of a SIP (Session Initiation Protocol) message or a response message corresponding to the INVITE message is received, session data is generated from the information included in the INVITE message or the response message, and the session data is included in the session data. Adding information on the bandwidth used identified from the SDP syntax and storing it in the session database;
2. The packet relay device according to claim 1, wherein a used bandwidth necessary for the session is obtained based on information on the used bandwidth. The packet relay apparatus according to claim 2, wherein the session data includes a source IP address, a source port number, a destination IP address, a destination port number, and a protocol. The packet relay device further comprises a session database (13),
The session control information analysis unit
When a packet including an INVITE message of a SIP message is received, session data including a source IP address, a protocol, and a source port number is generated by analyzing the INVITE message, and stored in the session database.
When a packet including a response message corresponding to the INVITE message is received, the session data corresponding to the response message stored in the session database is specified from a destination IP address, a destination port number, and the SDP syntax Information about the bandwidth used,
2. The packet relay device according to claim 1, wherein a used bandwidth necessary for the session is obtained based on information on the used bandwidth. The information on the used bandwidth includes a bit rate,
The packet relay device according to claim 2, wherein the session information analysis unit obtains a use band necessary for the session from the bit rate. The information on the used band includes information on a coding standard and a sampling rate,
The session information analysis unit obtains a use band necessary for the session using a coding rate information prepared in advance and a bit rate correspondence table in which a sampling rate and a bit rate are associated with each other. Item 5. The packet relay device according to any one of Items 2 to 4. The information on the used band includes information on a coding standard,
The session information analysis unit obtains a use band necessary for the session by specifying a maximum bit rate defined in the encoding standard from the information of the encoding standard. 5. The packet relay device according to any one of 4 to 4. A packet including session control information for establishing the session communicated between terminals that are required to establish a session is received, and a bandwidth required for the session is determined based on the session control information included in the packet. A first stage of seeking,
A packet relay method including a second step of relaying a packet of the session in a use band required for the session determined in the first step;
In the first step, the SDP (Session Description Protocol) syntax included in the received packet is used as the session control information, and a use band necessary for the session is obtained based on the SDP syntax. Relay method. The first stage further includes
When receiving an INVITE message of a SIP (Session Initiation Protocol) message or a packet including a response message corresponding to the INVITE message, generating session data from the information included in the INVITE message or the response message;
Adding information on the used bandwidth specified from the SDP syntax to the session data and storing it in the session database (13);
The packet relay method according to claim 8, further comprising: obtaining a used bandwidth necessary for the session based on information on the used bandwidth. The packet relay method according to claim 9, wherein the session data includes a source IP address, a source port number, a destination IP address, a destination port number, and a protocol. The first stage further includes
When a packet including an INVITE message of a SIP message is received, session data including a source IP address, a protocol, and a source port number is generated by analyzing the INVITE message and stored in the session database (13). Stages,
When a packet including a response message corresponding to the INVITE message is received, the session data corresponding to the response message stored in the session database is specified from a destination IP address, a destination port number, and the SDP syntax Adding information about the bandwidth used,
The packet relay method according to claim 8, further comprising: obtaining a used bandwidth necessary for the session based on information on the used bandwidth. The information on the used bandwidth includes a bit rate,
12. The packet relay method according to claim 9, wherein in the step of obtaining a use band necessary for the session, a use band necessary for the session is obtained from the bit rate. The information on the used band includes information on a coding standard and a sampling rate,
In the step of obtaining the use band necessary for the session, the use band necessary for the session is obtained by using information of a coding standard prepared in advance and a bit rate correspondence table in which a sampling rate and a bit rate are associated with each other. The packet relay method according to claim 9, wherein: The information on the used band includes information on a coding standard,
The step of obtaining a use band necessary for the session is to obtain a use band necessary for the session by specifying a maximum bit rate defined in the coding standard from the information of the coding standard. The packet relay method according to claim 9.