JP5147562B2 - Call control method, system, server, and session border controller - Google Patents

Description

  The present invention relates to a call control method, a system, a server, and a session border controller. More specifically, the present invention relates to a session border controller having a plurality of terminals and an input buffer for retaining packets from the plurality of terminals. SBC), and call control in a system having a call control server that controls the SBC.

  Along with the rapid spread of the Internet, in recent years, a faster bidirectional broadband service has been desired. Furthermore, cooperation between fixed communication and mobile communication, integration of telephone network, broadcasting network and Internet, cost reduction, improvement of service quality, etc. are desired. To realize these, standardization organizations such as the International Telecommunication Union (ITU-T), the European Telecommunications Standards Institute (ETSI), and the IETF (Internet Engineering Task Force) Next Generation Network (NGN) technology standards have been established, and NGNs are being built around the world.

  NGN connects terminals and operators with call control server, router and session border controller (SBC) connected by packet transfer nodes based on Internet Protocol (IP) and Asynchronous Transfer Mode (ATM), (1) SIP (Session Initiation Protocol), which is a communication protocol for control that is also used for IP telephones, is used for establishing and disconnecting a session. (2) A control device for performing QoS (service quality) control such as bandwidth securing and security-related processing such as NAT / firewall is provided.

  FIG. 1 is a system configuration diagram for explaining the operation of a conventional call control server and SBC in the NGN 100. Such a configuration is described in Non-Patent Document 1. The NGN 100 shown in the upper half of FIG. 1 includes terminals 110a and 110b, an input buffer for retaining packets from the terminals, an SBC 120 that controls a session between the terminals, a call control server 130 that controls the SBC 120, The network 140a of the business operator A and the network 140b of the business operator B are connected. The call control server 130 performs call admission control according to the performance limit of the SBC 120 set for itself, and ensures the quality of traffic passing through the SBC 120. When the call admission control is performed, the call control server 130 refers to a session description defined by a session description protocol (SDP). In general, information regarding the performance limit of the session description is only bandwidth information. is there.

  FIG. 2 shows a call acceptance sequence when the conventional call control server manages the bandwidth. In step 202, the terminal 110a makes a call. In step 204, the call control server 130 adds the band information described in the session description, and calculates the total x1 + x2 + x3 + x4 of the traffic band requested by the service provider including the terminal 110a. If the total bandwidth is less than XMbit / s, which is the performance limit of the SBC 120, that is, X> x1 + x2 + x3 + x4, the call control server 130 transmits call setting information to the SBC 120 in step 206. The call setting information is, for example, an address of the terminal 110a, a destination address for the terminal 110a to send to the SBC, an address of the terminal 110b, a destination address for the terminal 110b to send to the SBC, a traffic communication band, and a physical interface through which the traffic passes. . In step 208, when the SBC 120 sets a call according to the call setting information, the SBC 120 transmits a setting completion message to the call control server 130. In step 210, the call control server 130 transfers the call received in step 202 to the terminal 110b. In step 212, the terminal 110b notifies the terminal 110a that the call has been accepted. In step 214, a call is realized between the terminal 110a and the terminal 110b.

  FIG. 3 is a call acceptance sequence when the conventional SBC manages the bandwidth. In step 302, the terminal 110a makes a call. In step 304, the call control server 130 transmits call setting information similar to that in step 206 of FIG. At step 306, the SBC 120 calculates the total traffic bandwidth in the same manner as step 204 of FIG. 2 and compares it with the performance limits of the SBC 120. If the total bandwidth is less than XMbit / s, which is the performance limit of the SBC 120, the SBC 120 transmits a setting completion message to the call control server 130 in step 308. Steps 310 to 314 are similar to steps 210 to 214 in FIG.

  FIG. 4 is a call acceptance rejection sequence when the conventional call control server manages the bandwidth. In step 402, the terminal 110a makes a call. In step 404, the call control server 130 calculates the total traffic bandwidth in the same manner as in step 204 of FIG. 2 and compares it with the performance limit of the SBC 120. If the total bandwidth is greater than XMbit / s, which is the performance limit of the SBC 120, in step 406, the call control server 130 transmits a call acceptance rejection message to the terminal 110a and rejects the call in step 402.

  FIG. 5 shows a call acceptance refusal sequence when the conventional SBC manages the bandwidth. Steps 502 to 504 are the same as steps 302 to 304 in FIG. In step 506, the call control server 130 performs the same calculation and comparison as in step 404 of FIG. If the total bandwidth is greater than XMbit / s, which is the performance limit of the SBC 120, the SBC 120 transmits a setting acceptance rejection message due to insufficient bandwidth to the call control server 130 in step 508. Step 510 is similar to step 406.

The state of call acceptance refusal described with reference to FIGS. 4 and 5 is shown in the lower half of FIG. In FIG. 1, the traffic acceptance shown at the bottom is rejected. However, since the call control server 130 cannot recognize the packet processing performance for a second which is a performance limit other than the bandwidth of the SBC 120, even if the call reception is controlled based on the total bandwidth as described above, the packet processing performance for the second is equal to that of the SBC 120. Performance limits may be exceeded. Therefore, even if the packet processing performance for the second, which is a performance limit other than the bandwidth, reaches the limit, call acceptance cannot be restricted, and packet discard or packet delay occurs for the traffic that is communicated.
Yuji Inoue, introduction to the latest technology NGN that he wants to know, (Japan), Impress R & D, January 30, 2007, p. 156-172

  An object of the present invention is to provide a method, a system, and an apparatus that perform call admission control considering not only bandwidth information but also packet processing performance.

  According to the first aspect of the present invention, a call of a system having a plurality of terminals, a session border controller (SBC) having an input buffer for retaining packets from the plurality of terminals, and a call control server for controlling the SBC. A control method is provided. The method includes the steps of: (a) the SBC monitoring the input buffer to determine whether a packet is retained exceeding a predetermined congestion threshold; and (b) a packet exceeding the predetermined congestion threshold. If it is determined that it is stagnant, the SBC notifies the call control server of congestion, and (c) the call control server instructs the SBC not to accept a new call. .

  According to a second aspect of the present invention, a system for performing call control is provided. The system includes a plurality of terminals, a session border controller (SBC) having an input buffer for retaining packets from the plurality of terminals, and a call control server for controlling the SBC. A congestion monitoring unit that monitors a buffer and determines whether or not a packet is retained exceeding a predetermined congestion threshold; and when it is determined that a packet is retained exceeding the predetermined congestion threshold, the call control A control signal processing unit that notifies the server of congestion, and the call control server instructs the SBC not to accept a new call when the SBC is notified of the congestion.

  According to a third aspect of the present invention, a call control for controlling the SBC used in a system having a plurality of terminals and a session border controller (SBC) having an input buffer for retaining packets from the plurality of terminals. A server is provided. When the SBC is notified of the congestion, the call control server instructs the SBC not to accept a new call, or uses more bandwidth among calls connected to the SBC. Further instructing to disconnect one or a plurality of calls among a call using the codec and a call using a codec having a higher processing load.

  According to a fourth aspect of the present invention, there is provided a session border controller (SBC) used in a system having a plurality of terminals and a call control server, and having an input buffer for retaining packets from the plurality of terminals. . The SBC has a congestion monitoring unit that monitors the input buffer and determines whether or not a packet is retained exceeding a predetermined congestion threshold, and a control signal processing unit that notifies the call control server of the congestion. When it is determined that the packet has accumulated exceeding the predetermined congestion threshold, among calls connected to the SBC, calls using a codec that uses more bandwidth and processing load Delete one or more interfaces or VPN (Virtual Private Network) settings corresponding to one or more calls using a larger codec.

  According to the present invention, it is possible to perform further call control based on the SBC second packet processing performance while using an existing call control method based on bandwidth information, and it is possible to prevent deterioration of traffic.

[Overview]
FIG. 6 is a system configuration diagram for explaining the operation of the call control server and the SBC of the present invention in the NGN 200. The NGN 200 shown in the upper half of FIG. 6 includes a call control server 230 that controls the terminals 210a and 210b, the SBC 220, and the SBC 220, and the network 240a of the operator A and the network 240b of the operator B that connect them.

  FIG. 7 is a diagram showing the configuration of the SBC 220 in detail. The SBC 220 processes the packets received in the input buffer 221 and the input buffer 221 for retaining packets received from the carrier network 240a or 240b, and transmits them to the carrier network 240a or 240b. Receives call setting information from the call control server 230 via the congestion monitoring unit 223, the operator network 240a or 240b, which monitors whether or not the staying packet exceeds the congestion threshold and generates a congestion notification, and the call control server 230 includes a control signal processing unit 224 that transmits a congestion notification to 230 and a session control unit 225 that controls a session based on the call setting information.

  As shown in the lower half of FIG. 6, in the present invention, when the call control server 230 receives a congestion notification from the SBC 220, in addition to the above-described conventional bandwidth control, the call control server 230 is based on the congestion notification. Perform call control. The SBC 220 has a plurality of addresses, and the terminals 210a and 210b transmit traffic via the carrier networks 240a and 240b with any one of the plurality of addresses as a destination. The call control server 230 knows which address is used from among the plurality of addresses, and selects an appropriate address to set a call.

[Example 1]
A first embodiment of the present invention will be described with reference to FIGS.

  FIG. 8 is a system configuration diagram for explaining the first embodiment of the present invention. The upper half of FIG. 8 is the same as the configuration of the upper half of FIG.

  FIG. 9 is a sequence diagram for explaining the first embodiment of the present invention. FIG. 9A shows an acceptance rejection sequence when the congestion threshold is exceeded by acceptance of a new call. Steps 902 to 904 in FIG. 9 are the same as steps 302 to 304 in FIG. In step 906, the SBC 220 sums the bandwidth information included in the session description and compares it with the performance limit of the SBC 220 in the same manner as the conventional sequence described with reference to FIGS. When the total exceeds the performance limit, the same processing as the conventional sequence is performed. Otherwise, in step 906, the congestion monitoring unit 223 of the SBC 220 monitors the input buffer 221 and detects that the packet has accumulated exceeding the congestion threshold. The fact that a packet stays beyond the congestion threshold means that there is a possibility that a packet exceeding the packet processing performance of SBC per second may flow. That is, as shown in the lower half of FIG. 8, it is expected that y1 + y2 + y3 + y4, which is the total number of packets per second of traffic passing through the SBC, exceeds the SBC second packet processing performance Ypps. In step 908, the control signal processing unit 224 of the SBC 220 determines that there is a possibility that the packet flowing into the SBC 220 may exceed the performance of the packet processing function unit 222, and transmits a setting acceptance rejection message to the call control server 230. In step 910, the call control server 230 transmits a call rejection message rejecting the call in step 902 to the terminal 110a.

  FIG. 9B shows a call acceptance rejection sequence when the congestion threshold is exceeded before a new call is accepted. In step 912, the SBC 220 detects that the packet has remained above the congestion threshold in the same manner as in step 906. In step 914, the SBC 220 sends a packet processing performance shortage alarm to the call control server 230 indicating that there is a possibility that the packet may flow in excess of its own packet processing performance. In step 916, the terminal 110a places a call. In response to this, in step 918, the call control server 230 transmits a call acceptance rejection message to the terminal 110a.

  According to the first embodiment of the present invention described above, since the call control server 230 can recognize that the packet flowing into the SBC 220 may exceed the packet processing performance limit of the SBC 220, it is shown in the lower half of FIG. As described above, even if the total bandwidth information included in the session description is below the performance limit of the SBC 220, that is, even if the bandwidth of the SBC 220 is surplus, there is a possibility of exceeding the packet processing performance limit of the SBC 220. Do not accept calls. Accordingly, call admission control is appropriately performed before the SBC 220 reaches the performance limit of the packet processing performance per second, and traffic degradation can be avoided.

[Example 2]
A second embodiment of the present invention will be described with reference to FIGS.

  FIG. 10 is a system configuration diagram for explaining a second embodiment of the present invention.

  FIG. 11 shows a call disconnection sequence in the case of disconnecting an existing call by detecting congestion according to the second embodiment of the present invention. Steps 1102 to 1114 in FIG. 11 are the same as the conventional call acceptance sequence, and are the same as steps 202 to 214 in FIG. Alternatively, steps 1102 to 1114 in FIG. 11 may be replaced with steps 302 to 314 in FIG. In step 1116, it is detected that the packet stays above the congestion threshold as in step 906 of FIG. In step 1118, a packet processing performance deficiency alarm is transmitted in the same manner as in step 914 in FIG. In step 1120, the call control server 230 checks the codec included in the SIP packet, the ptime parameter that gives the time length in milliseconds of the media in the packet included in the SDP packet, and loads the packet processing function unit 222 of the SBC 220 with a larger load. Select one or more existing calls that are making calls or using more bandwidth. In step 1122, the call control server 230 disconnects the existing call or calls selected in step 1120. Here, as an example, the call of the terminal 110a is disconnected. In step 1124, the call control server 230 instructs the SBC 220 to delete the call setting information of the call disconnected in step 1120. In step 1126, the SBC 220 notifies the call control server 230 that the call setting information has been deleted. Steps 1118 to 1126 are repeated until the lack of processing performance of the SBC 220 is resolved, that is, until congestion is not detected. In step 1128, when congestion is not detected, the SBC 220 transmits a packet processing performance deficiency alarm clear message to the call control server 230 indicating that the packet processing performance is not deficient.

  According to the second embodiment of the present invention described above, since the call control server 230 can recognize that the packet flowing into the SBC 220 exceeds the packet processing performance limit of the SBC 220, as shown in the lower half of FIG. Even if the call is accepted because the total bandwidth information included in the session description is below the performance limit of the SBC 220, the call is disconnected if the packet processing performance of the SBC 220 may reach the limit. Accordingly, call admission control is appropriately performed before the SBC 220 reaches the performance limit of the packet processing performance per second, and traffic degradation can be avoided.

[Example 3]
A third embodiment of the present invention will be described with reference to FIGS.

  FIG. 12 is a system configuration diagram for explaining a third embodiment of the present invention. 12 is provided with two SBCs 220a and 220b, and a router or switch 250 that connects the SBCs 220a and 220b and the operator network B, and the other components are the same as those in the upper half of FIG.

  FIG. 13 is a sequence diagram for explaining a third embodiment of the present invention when an SBC autonomously links down due to congestion. Steps 1302 to 1318 in FIG. 13 are the same as steps 1102 to 1118 in FIG. However, the SBC 220 is replaced with the SBC 220a. In step 1320, the session control unit 225 of the SBC 220a autonomously links down the interface with the router or switch 250, thereby deleting the route information held in the route selection table of the router or switch 250 to the router or switch 250. Let In step 1322, the SBC 220a transmits a deletion completion message to the call control server 230 to notify that the route addressed to the SBC 220a has been deleted due to the link down. In step 1324, the call control server 230 transmits call setting information to the SBC 220b. In step 1326, the SBC 220b transmits a setting completion message indicating that the call setting is completed to the call control server 230. Steps 1328 to 1330 are the same as steps 1124 to 1126 in FIG.

  According to the third embodiment of the present invention described above, a call accepted because the sum of the bandwidth information included in the session description is below the performance limit of the SBC 220a may cause the second packet processing performance of the SBC 220a to reach the limit. If there is, the processing is performed by the SBC 220b having sufficient processing performance instead of the SBC 220a. Therefore, before the SBC 220a reaches the performance limit of the packet processing performance for a second, the SBC that processes the call is appropriately switched, the traffic is appropriately bypassed, and the deterioration of the traffic can be avoided.

[Example 4]
A fourth embodiment of the present invention will be described with reference to FIGS. The configuration of the fourth embodiment is the same as that of the third embodiment.

  FIG. 14 is a sequence diagram for explaining a fourth embodiment of the present invention when the call control server 230 instructs to delete an interface or VPN (virtual private network) setting due to congestion. Steps 1402 to 1418 in FIG. 14 are the same as steps 1302 to 1318 in FIG. In step 1420, similar to step 1120 of FIG. 11, one or more existing calls that are heavily loaded or using more bandwidth are selected by the packet processing function 222 of the SBC 220a. In step 1422, the call control server 230 instructs the SBC 220a to delete one or more interfaces or one or more VPN settings to which the one or more existing calls selected in step 1420 are assigned. Steps 1424 to 1432 are the same as Steps 1322 to 1330 in FIG.

  According to the above-described fourth embodiment of the present invention, a call accepted because the sum of the bandwidth information included in the session description is below the performance limit of the SBC 220a may cause the second packet processing performance of the SBC 220a to reach the limit. If there is, the processing is performed by the SBC 220b having sufficient processing performance instead of the SBC 220a. Therefore, before the SBC 220a reaches the performance limit of the packet processing performance for a second, the SBC that processes the call is appropriately switched, the traffic is appropriately bypassed, and the deterioration of the traffic can be avoided.

[Example 5]
A fifth embodiment of the present invention will be described with reference to FIGS.

  FIG. 15 is a system configuration diagram for explaining a fifth embodiment of the present invention, which is the same as the configuration of FIG.

  FIG. 16 is a sequence diagram for autonomously deleting a VPN configuration due to congestion, explaining a fifth embodiment of the present invention. Steps 1602 to 1618 in FIG. 16 are the same as steps 1302 to 1318 in FIG. In step 1620, the session control unit 225 of the SBC 220a autonomously deletes the VPN setting corresponding to the input buffer 221 in which congestion is detected, so that the router or switch 250 holds the VPN held by the router or switch 250. Delete the setting. Steps 1622 to 1630 are the same as steps 1322 to 1330 in FIG.

  According to the fifth embodiment of the present invention described above, a call accepted because the sum of the bandwidth information included in the session description is below the performance limit of the SBC 220a may cause the second packet processing performance of the SBC 220a to reach the limit. In this case, the processing is performed by the SBC 220b having sufficient processing performance instead of the SBC 220a. Therefore, before the SBC 220a reaches the performance limit of the packet processing performance for a second, the SBC that processes the call is appropriately switched, the traffic is appropriately bypassed, and the deterioration of the traffic can be avoided.

It is a system block diagram explaining operation | movement of the conventional call control server and SBC. This is a call acceptance sequence when a conventional call control server manages a bandwidth. This is a call acceptance sequence when a conventional SBC manages a band. It is a call acceptance rejection sequence when a conventional call control server manages a bandwidth. It is a call acceptance rejection sequence when a conventional SBC manages a band. It is a system block diagram explaining operation | movement of the call control server and SBC of this invention. It is a figure which shows the structure of SBC of this invention in detail. 1 is a system configuration diagram illustrating a first embodiment of the present invention. It is a sequence diagram explaining the 1st example of the present invention. It is a system block diagram explaining the 2nd Example of this invention. It is a sequence diagram explaining the 2nd example of the present invention. It is a system block diagram explaining the 3rd Example of this invention. It is a sequence diagram explaining the 3rd example of the present invention. It is a sequence diagram explaining the 4th example of the present invention. It is a system block diagram explaining the 5th Example of this invention. It is a sequence diagram explaining the 5th example of the present invention.

Explanation of symbols

110a, 110b, 220a, 220b Terminal 120, 220, 220a, 220b Session border controller (SBC)
130, 230 Call control server 140a, 140b, 240a, 240b Carrier network 221 Input buffer 222 Packet processing function unit 224 Control signal processing unit 225 Session control unit 250 Router or switch

Claims (6)

A call control method for a system having a plurality of terminals, a session border controller (SBC) having an input buffer for retaining packets from the plurality of terminals, and a call control server for controlling the SBC,
(A) the SBC monitors the input buffer to determine whether a packet has accumulated beyond a predetermined congestion threshold;
(B) if it is determined that the packet is retained beyond the predetermined congestion threshold, the SBC notifies the call control server of the congestion;
(C) the call control server instructs the SBC not to accept a new call;
(D) The call control server uses, for the SBC, a call using a codec that uses a larger band and a codec with a larger processing load among calls connected to the SBC. Instructing to disconnect one or more of the calls;
Have
The system further includes one or more packet forwarding nodes connecting the plurality of terminals, one or more SBCs, and the call control server,
(E) The call control server deletes the route including the address of the SBC that has notified the congestion from the route selection table of the packet forwarding node for the packet forwarding node that receives the packet flowing into the system, or Instructing the route to link down,
(F) the call control server transmits setting information necessary for setting a call to one SBC not informing the congestion; and (g) the SBC not informing the congestion is in the setting information. Re-establishing all calls addressed to the SBC address notifying the congestion as calls addressed to the SBC address not notifying the congestion,
A call control method comprising: A call control method for a system having a plurality of terminals, a session border controller (SBC) having an input buffer for retaining packets from the plurality of terminals, and a call control server for controlling the SBC,
(A) the SBC monitors the input buffer to determine whether a packet has accumulated beyond a predetermined congestion threshold;
(B) if it is determined that the packet is retained beyond the predetermined congestion threshold, the SBC notifies the call control server of the congestion;
(C) the call control server instructs the SBC not to accept a new call;
(D) The call control server uses, for the SBC, a call using a codec that uses a larger band and a codec with a larger processing load among calls connected to the SBC. Instructing to disconnect one or more of the calls;
Have
The system further includes one or more packet forwarding nodes connecting the plurality of terminals, one or more SBCs, and the call control server,
(H) The call control server includes a VPN path including an address of an SBC that has notified the packet transfer node that receives a packet flowing into the system of congestion from a VPN (virtual private network) path of the packet transfer node. Instructing you to delete,
(F) the call control server transmits setting information necessary for setting a call to one SBC not informing the congestion; and (g) the SBC not informing the congestion is in the setting information. And re-establishing all calls addressed to the SBC address notifying the congestion as calls addressed to the SBC address not notifying the congestion. A system for performing call control,
Multiple devices,
A session border controller (SBC) having an input buffer for retaining packets from the plurality of terminals;
A call control server for controlling the SBC;
The SBC is
A congestion monitoring unit that monitors the input buffer and determines whether or not a packet remains above a predetermined congestion threshold;
A control signal processing unit for notifying the call control server of congestion when it is determined that the packet is retained exceeding the predetermined congestion threshold;
The call control server instructs the SBC not to accept a new call when congestion is notified from the SBC.
The call control server sends a call using a codec that uses more bandwidth and a codec that uses a larger processing load to the SBC. Further instructing to disconnect one or more calls;
The system further includes one or more packet forwarding nodes connecting the plurality of terminals, one or more SBCs, and the call control server,
The call control server deletes a route including the address of the SBC that has notified the congestion from the route selection table of the packet forwarding node, or links the route to the packet forwarding node that receives the packet flowing into the system. Instructed to go down,
The call control server transmits setting information necessary for setting a call to one SBC not informing the congestion, and the SBC not informing the congestion has notified the congestion based on the setting information. A call control system for reestablishing all calls addressed to an SBC address as calls addressed to an SBC address that has not been notified of the congestion. A system for performing call control,
Multiple devices,
A session border controller (SBC) having an input buffer for retaining packets from the plurality of terminals;
A call control server for controlling the SBC;
The SBC is
A congestion monitoring unit that monitors the input buffer and determines whether or not a packet remains above a predetermined congestion threshold;
A control signal processing unit for notifying the call control server of congestion when it is determined that the packet is retained exceeding the predetermined congestion threshold;
The call control server instructs the SBC not to accept a new call when congestion is notified from the SBC.
The call control server sends a call using a codec that uses more bandwidth and a codec that uses a larger processing load to the SBC. Further instructing to disconnect one or more calls;
The system further includes one or more packet forwarding nodes connecting the plurality of terminals, one or more SBCs, and the call control server,
The call control server instructs the packet forwarding node that receives a packet flowing into the system to delete the VPN path including the address of the SBC that has notified the congestion from the VPN path of the packet forwarding node;
The call control server transmits setting information necessary for setting a call to one SBC not informing the congestion, and the SBC not informing the congestion has notified the congestion based on the setting information. A call control system for reestablishing all calls addressed to an SBC address as calls addressed to an SBC address that has not been notified of the congestion. A call control server for controlling the SBC used in a system having a plurality of terminals and a session border controller (SBC) having an input buffer for retaining packets from the plurality of terminals. Terminal, one or a plurality of the SBCs, and one or a plurality of packet forwarding nodes connecting the call control servers,
When notified of congestion from the SBC,
Instruct the SBC not to accept a new call, or use a codec that uses a codec that uses more bandwidth and a codec with a higher processing load among calls connected to the SBC Further instructing one or more calls to be disconnected
Instructs the packet forwarding node that receives a packet flowing into the system to delete the route including the address of the SBC that has notified the congestion from the route selection table of the packet forwarding node or to link down the route. ,
Sending the setting information necessary for setting up a call to one SBC not reporting congestion,
The SBC not informing the congestion re-establishes all calls addressed to the SBC address informing the congestion as calls addressed to the SBC address not informing the congestion, based on the setting information.
Call control server. A session border controller (SBC) used in a system having a plurality of terminals and a call control server and having an input buffer for retaining packets from the plurality of terminals,
A congestion monitoring unit that monitors the input buffer and determines whether or not a packet is retained exceeding a predetermined congestion threshold; and a control signal processing unit that notifies the call control server of congestion,
When it is determined that the packet has accumulated exceeding the predetermined congestion threshold, among calls connected to the SBC, calls using a codec that uses more bandwidth and processing load. Delete one or more interfaces or VPN (Virtual Private Network) settings corresponding to one or more calls using a large codec ;
The call control server instructs the terminal that receives a packet flowing into the system to delete the VPN path including the address of the SBC that has notified the congestion from the VPN (virtual private network) path of the terminal,
The call control server sends setting information necessary for setting a call to one SBC not informing the congestion; and
The SBC not informing the congestion re-establishes all calls addressed to the SBC address informing the congestion as calls addressed to the SBC address not informing the congestion based on the setting information. .

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