JP5365685B2 - Call control function allocation method, server, I-CSCF and communication system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a concrete method for dynamically allocating any S-CSCF server of a plurality of S-CSCF servers to a terminal based on each state of the plurality of S-CSCF servers. <P>SOLUTION: A call control function allocation method in a network where a terminal and a plurality of call control functions controlling communication of the terminal are arranged is characterized in that: each running state information of the plurality of call control functions is acquired; each terminal accommodation information of the plurality of call control functions is acquired; each allocation order of the plurality of call control functions is determined based on the running state information and the terminal accommodation information; and a response containing the allocation order and information of the call control function corresponding to the allocation order is performed to a request of the terminal. <P>COPYRIGHT: (C)2012,JPO&amp;INPIT

Description

The present invention relates to a call control function allocation method, a server , an I-CSCF and a communication system, and more particularly to a method for allocating an S-CSCF server in an IMS.

IMS is a communication method that integrates access networks such as the public switched telephone network and mobile communication networks to provide communication services, and is a core technology of the next generation network, NGN (Next Generation Network). IMS (IP Multimedia Subsystem) is standardized by the standardization organization 3GPP (Third Generation Partnership Project).

IMS uses a communications protocol called SIP (Session Initiation Protocol) as a base for connecting nodes such as computers and mobile terminals on communication lines. SIP is a session control protocol standardized by the IETF (Internet Engineering Task Force), a standards organization.

Specifically, in IMS, connections are controlled by the Session Control Function (SCF).

The CSCF (Call Session Control Function) configured in the SIP server is particularly important, as it controls SIP messages.

CSCF has three functional entities: P-CSCF (Proxy Call Session Control Function), I-CSCF (Interrogation Call Session Control Function), and S-CSCF (Serving Call Session Control Function).

In addition to the three functional entities mentioned above, the database function HSS (Home Subscriber Server) is an important functional entity.

The P-CSCF is a SIP proxy function that has at least an interface related to SIP, and when it receives a SIP message sent by a terminal, it forwards the SIP message to another CSCF.

I-CSCF is a SIP-Proxy function that has at least SIP and Diameter interfaces.

When the I-CSCF receives a SIP message, it queries the HSS based on the received SIP message, assigns an S-CSCF based on the subscriber information notified by the HSS, and forwards the SIP message to the selected S-CSCF.

S-CSCF is a call control function that has at least a SIP interface.

When the S-CSCF receives a SIP message, it processes it based on the received SIP message.

HSS is a function that stores subscriber information.

The HSS responds to inquiries from the CSCF and notifies it of subscriber information.

Here, the subscriber information stored by the HSS includes a user identifier, a URI (Uniform Resource Identifier), user authentication information, and information about the S-CSCF used by the user.

In IMS, functional entities form the IMS core network and control IMS connections.

In this invention, the network that controls IMS connections is called the IMS core network.

Here, we will explain the outline of the IMS core network using Figure 1.

Note that FIG. 1 is an example of an IMS core network, and the terminal 1 shown in FIG. 1 is not necessarily a required element of an IMS core network.

In FIG. 1, the functional entities are deployed on the network as servers for each functional entity, but it is also possible to provide each functional entity as software on one or more pieces of hardware, for example.

In FIG. 1, the IMS core network includes an IP network 18, and includes a terminal 11, a P-CSCF server 12, an I-CSCF server 13, an HSS server 14, and multiple S-CSCF servers 15 to 17.

Next, the operation related to processing a REGISTER message in the IMS core network shown in Figure 1 will be explained using Figure 6.

REGISTER is a SIP message that is sent from a terminal as a registration request.

We will also explain the case where the HSS server 14 in FIG. 1 stores the S-CSCF server 15 as information on the S-CSCF server used by the terminal 1 in the subscriber information that is prestored therein.

First, terminal 11 sends a REGISTER message. (S61)

Next, the P-CSCF server 12 receives the REGISTER message sent by the terminal 11 and forwards the received REGISTER message. (S62)

Next, the -CSCF server 13 receives the REGISTER message transferred by the P-CSCF server 12 and sends a Diameter UAR message to make an inquiry. (S63)

Next, the HSS server 14 receives the Diameter UAR message sent by the I-CSCF server 13 and responds by sending a Diameter UAA message including the pre-stored subscriber information. (S64)

Next, the I-CSCF server 13 receives the Diameter UAA message sent by the HSS server 14, selects the S-CSCF server used by the terminal 11 as the S-CSCF server 15 based on the subscriber information contained in the received Diameter UAA message, and transfers the REGISTER message to the S-CSCF server 5. (S65)

Next, the S-CSCF server 15 receives the REGISTER message transferred by the I-CSCF server 13, performs registration based on the received REGISTER message, and sends a Diameter SAR when registration is complete. (S66)

According to the above explanation, the I-CSCF server and the HSS server work together to assign one of the multiple S-CSCF servers to terminal 1.

The details of allocating one of multiple S-CSCFs through cooperation between the I-CSCF and HSS are described in Non-Patent Document 1.

3GPP TS 22.228

However, Non-Patent Document 1 does not describe the specific contents of assignment to terminals according to the status of the S-CSCF server.

As a result, if multiple S-CSCF servers are deployed, dynamic allocation is not possible, which is an issue.

Because dynamic allocation is not possible, in the operation related to processing the REGISTER message described above with reference to FIG. 2, for example, S-CSCF server 15 is allocated as the S-CSCF server to be used by terminal 11, but if S-CSCF server 5 is abnormal, the REGISTER message sent from terminal 11 will not be processed normally.

The present invention aims to provide a specific method for dynamically assigning one of multiple S-CSCF servers to a terminal based on the operation status information and subscriber capacity information of each of the multiple S-CSCF servers.

The present invention is characterized in that, in a network in which a terminal and a plurality of call control functions that control communication of the terminal are deployed, an information acquisition means acquires the software status of each of the plurality of call control functions, a monitoring means acquires terminal accommodation information of each of the plurality of call control functions, a judgment means judges an allocation order of each of the plurality of call control functions based on the software status and the terminal accommodation information, and a response means responds to a request from the terminal by including information on the allocation order and the call control functions corresponding to the allocation order in a response.

The present invention also provides a server that assigns control functions that control communication between terminals in a network in which terminals and a plurality of control functions that control communication between the terminals are provided, the server comprising: a storage means for storing information; an information acquisition means for acquiring a software state from each of the plurality of control functions and storing it in the storage means; and a judgment means for determining an allocation order for each of the plurality of control functions based on the information stored in the storage means, and the server responds to a request from the terminal by including information on the allocation order determined by the judgment means and the control functions corresponding to the allocation order.

The present invention is also characterized in that an I-CSCF (Interrogation Call Session Control Function) in which an HSS (Home Subscriber Server) determines an allocation order based on the software state of each of a plurality of S-CSCFs (Serving Call Session Control Functions) and the number of terminals accommodated, transmits allocation order information and server information to the I-CSCF, and then performs processing to select an S-CSCF (Serving Call Session Control Function) with allocation order 1 as an SCSF to be used by the terminal based on the allocation order information and server information included in a signal received by the I-CSCF.

The present invention also provides a communication system equipped with a terminal, a plurality of control functions for controlling communication of the terminal, and a database function, wherein the database function acquires the software status and terminal accommodation information of each of the plurality of control functions, determines the allocation order of each of the plurality of call control functions based on the software status and the terminal accommodation information, and responds by including the allocation order information in a response to a request from the terminal.

The present invention has the advantage of being able to realize a method for allocating one of a plurality of S-CSCF servers based on the operating status information and subscriber accommodation rate information of each S-CSCF server.

In addition, S-CSCF servers can be allocated based on the operating status information and subscriber capacity information of each S-CSCF server, which has the effect of enabling dynamic allocation of S-CSCF servers.

Furthermore, since S-CSCF servers can be assigned based on the operating status information and subscriber capacity information of each S-CSCF server, it is possible to prevent processing from concentrating on any one of multiple S-CSCF servers.

Furthermore, since the operating status information and subscriber accommodation rate information of each S-CSCF server are stored in the HSS server, there is an advantage that the status information of each S-CSCF server can be managed centrally.

1 is a schematic configuration of an IMS core network according to the present invention. 2 is a schematic configuration of a management table according to the present invention. 4 is a schematic diagram of a maximum accommodation number table according to the present invention. 3 is a schematic configuration of a judgment priority table according to the present invention. 4 is a sequence showing the operation of an IMS core network according to the present invention. 1 is a sequence showing the operation of a conventional IMS core network.

Figure 1 illustrates an embodiment of the server allocation method of the present invention, using an example in which the method is applied to an IMS core network.

Figure 1 shows a configuration that is basically the same as that of a conventional IMS core network. In Figure 1, the IMS core network has an IP network 18, and is equipped with a terminal 11, a P-CSCF server 12, an I-CSCF server 13, an HSS server 14, and multiple S-CSCF servers 15 to 17.

The IP network 18 provided in the IMS core network may be a wired transmission path or a wireless transmission path.

Furthermore, the communication protocol used in the IP network 18 provided in the IMS core network may be either IPv4 (Internet Protocol Version 4) or IPv6 (Internet Protocol Version 6).

Furthermore, the casting method used in the IP network 18 provided in the IMS core network may be unicast, broadcast, or anycast.

Furthermore, the terminal 11, the P-CSCF server 12, the I-CSCF server 13, the HSS server 14, and the multiple S-CSCF servers 15 to 17 deployed in the IMS core network can transmit and receive data between each other via the IP network 18.

In addition, when considering network operations, it is natural that the IMS core network may contain nodes not shown, such as DNS servers, DHCP servers, routers, and switches.

Furthermore, terminal 1 is not limited to being deployed in IP network 18, but may be deployed in a network other than IP network 18, such as a public network or an internal line network (not shown). In that case, it goes without saying that there will be a node such as a connection device (not shown) that connects IP network 18 to a network other than IP network 18.

The terminal 11 is a terminal used by a user, such as a mobile phone, a landline phone, or a PC (Personal Computer).

The P-CSCF server 12 is basically the same as the conventional P-CSCF server described above, and when it receives a SIP message, it forwards the SIP message to another CSCF.

The I-CSCF server 13 is basically the same as the conventional I-CSCF server described above. When it receives a SIP message, it queries the HSS based on the received SIP message, assigns an S-CSCF based on the subscriber information notified by the HSS, and transfers the SIP message to the selected S-CSCF.

S-CSCF servers 15 to 17 are basically the same as the conventional S-CSCF servers described above, and when they receive a SIP message, they perform processing based on the received SIP message.

The HSS server 14 is basically the same as the conventional HSS server described above, and responds to inquiries from the CSCF and notifies subscriber information. However, the HSS server 14 differs from conventional HSS servers in that it has information acquisition means, information monitoring means, information storage means, and allocation order determination means.

Here we provide a detailed explanation of the information acquisition means, information monitoring means, information storage means, and allocation order determination means possessed by the HSS server 14.

First, the information acquisition means is a means by which the HSS server 14 acquires information from each of the multiple S-CSCF servers 15 to 17.

The information acquisition means connects to each of the multiple S-CSCF servers 15-17 at predetermined intervals, acquires information held by the connected servers, and provides the acquired information to the information storage means.

Here, the information acquisition means pre-stores information such as 1 second, 1 minute, and 1 hour as the predetermined period.

The specified period pre-stored by the information acquisition means can be updated as appropriate.

The information acquisition means uses communication protocols such as FTP (File Transfer Protocol), HTTP (Hyper Text Transfer Protocol), Telnet, and SNMP (Simple Network Management Protocol) to connect to each of the multiple S-CSCF servers 15-17 and acquires at least the software status, CPU usage, and network usage information held by the connected servers.

In addition, the information acquisition means not only connects to each of the multiple S-CSCF servers 15-17 and acquires information held by the connected server, but also, when connected to by each of the multiple S-CSCF servers 15-17, acquires information held by the connected server using communication protocols such as FTP, HTTP, Telnet, and SNMP. The information acquisition means is capable of acquiring information autonomously and heteronomously.

Furthermore, when the information acquisition means provides the acquired information to the information storage means, the information acquisition means also provides the information to the information storage means together with server information from which the acquired information was obtained.

The server information in this invention includes the host name and IP address, etc.

In this invention, the information acquisition means uses SNMP to connect to each of the multiple S-CSCF servers 15 to 17, collects MIB (Management Information Base) information held by the connected servers, and provides at least the software status, CPU usage rate, NW usage rate, and connected server information to the information storage means.

Next, the information monitoring means is a means for monitoring the information that the HSS server 14 transmits and receives with each of the multiple S-CSCF servers 15 to 17.

The information monitoring means monitors the information sent to and received from each of the multiple S-CSCF servers 15-17, and when it finds information containing specific information, it acquires the server information of the sender of the found information and provides the acquired server information to the information storage unit.

Here, the information monitoring means prestores predetermined information such as REGISTER, INVITE, and MESSAGE.

The specified information pre-stored by the information monitoring means can be updated as appropriate.

In the present invention, the information monitoring means prestores Diameter SAR information as predetermined information, monitors packets sent to and received from each of the multiple S-CSCF servers 15 to 17, and when it detects the receipt of a Diameter SAR message, it obtains server information of the sender of the Diameter SAR message and provides the obtained server information to the information storage means.

Next, the information storage means is a means for storing information provided by the information acquisition means and the information monitoring means.

The information storage means has a table for storing information provided by the information acquisition means and the information monitoring means.

Tables held by the information storage means are, for example, management table 21(a) shown in FIG. 2 and maximum capacity table 31(a) shown in FIG. 3.

Management table 21(a) in Figure 2 is a table for storing information provided by the information acquisition means.

Management table 21(a) has attributes (columns) for at least server information, software status, CPU usage, network usage, capacity, and allocation order, and stores pairs of server information, software status, CPU usage, network usage, capacity, and allocation order information. If there are multiple pieces of server information, the software status, CPU usage, network usage, capacity, and allocation order are stored in pairs for each piece of server information.

Management table 21(a) can be searched and updated as appropriate using the information contained in the rows and columns.

The maximum capacity table 31(a) in Figure 3 is a table for storing information provided by the information monitoring means.

The maximum capacity table 31(a) has at least server information, maximum capacity, and capacity attributes (columns), and stores the server information, maximum capacity, and capacity information in pairs. If there is multiple server information, the maximum capacity information is stored for each server information in pairs.

The maximum capacity table 31(a) can be searched and updated as appropriate using the information contained in the rows and columns.

The server information and maximum capacity in the maximum capacity table 31(a) are stored in advance.

When the information storage means receives at least the destination server information, software status, CPU usage rate, NW usage rate, and capacity rate information from the information acquisition means, it stores these in pairs in the management table 21(a).

When the information storage means is provided with at least the server information of the sender of the Diameter SAR message from the information monitoring means, it uses the server information to search the maximum capacity table 31(a) and increments the number in the capacity column of the row of the corresponding server information.

The information storage means further performs a calculation between the capacity and the maximum capacity based on the maximum capacity table 31(a) by dividing the capacity by the maximum capacity x 100. This calculation determines the ratio of the capacity to the maximum capacity, and derives the capacity rate. The value derived by the calculation is output as a percentage.

The information storage means further searches the management table 21 using the server information of the sender of the Diameter SAR message, and stores the value derived by calculating the capacity divided by the maximum capacity x 100 in the capacity rate column of the row of the corresponding server information.

In the present invention, the information storage means has in advance the management table 21(a) shown in FIG. 2 and the maximum capacity table 31(a) shown in FIG. 3, and the operation will be described below in which the information provided by the information acquisition means is stored in the management table 21, the information provided by the information monitoring means is stored in the maximum capacity table 31(a), the capacity rate is derived based on the maximum capacity table 31(a), and the derived capacity rate value is stored in the management table 21(a).

Next, the allocation order determination means is a means for determining the allocation order of the servers based on the management table 21(a).

The allocation order determination means has a table in advance that stores information on the contents of the determination to be made based on the management table 21(a).

The table held by the allocation order determination means is, for example, the determination order table 41 shown in FIG. 4.

The judgment order table 41 in FIG. 4 has at least the judgment order attribute (column), and stores information on the judgment contents of software status 411, accommodation rate 412, CPU usage rate 413, and NW usage rate 414.

The information stored in the judgment ranking table 41 is ranked higher at the top and lower at the bottom.

In other words, the judgment order in the judgment order table 41 in Figure 4 is, in descending order, software status 411, capacity rate 412, CPU usage rate 413, and network usage rate 414, with the first judgment content being software status 411, the second judgment content being capacity rate 412, the third judgment content being CPU usage rate 413, and the fourth judgment content being network usage rate 414.

The judgment order table 41 can be searched and updated as appropriate.

The determination made based on the software status 411 is to search the software status column stored in the management table 21(a) and determine whether it is stored as normal. If it is stored as normal, the server information stored as normal is obtained.

The determination based on the occupancy rate 412 is made by searching the occupancy rate column stored in the management table 21(a) and determining which has a low occupancy rate value. If the occupancy rate value is determined to be low, server information is obtained.

The determination made by CPU usage 413 is to search the column of CPU usage stored in management table 21(a) and determine which has a low CPU usage. If the CPU usage value is determined to be low, server information is obtained.

The determination based on the NW usage rate 414 is made by searching the column of NW usage rates stored in the management table 21(a) and determining which has a low NW usage rate. If the value of the NW usage rate is determined to be low, server information is obtained.

The allocation ranking determination means searches the judgment ranking table 41 from the top to the bottom to obtain information on the judgment content and the judgment ranking.

Furthermore, the allocation ranking determination means obtains server information based on the information of the judgment content that is ranked first.

The allocation priority determination means further searches management table 21(a) using the server information obtained based on the information on the first determination content to identify a row, and obtains server information for the identified row based on the information on the determination content with the second determination priority.

The allocation priority determination means further searches management table 21(a) using the server information obtained based on the information on the second determination content to identify a row, and obtains server information for the identified row based on the information on the determination content that is third in the determination priority.

The allocation priority determination means further searches management table 21(a) using the server information obtained based on the information on the third determination content to identify a row, and obtains server information for the identified row based on the information on the determination content with the fourth determination priority.

Furthermore, when the allocation rank determination means obtains server information based on information on the judgment content that has the last judgment rank, it searches the management table 21 using the obtained server information to identify a row, and stores the number obtained by incrementing the number of allocation ranks previously stored in the allocation rank column of the identified row. If there is no number of allocation ranks previously stored, it stores 1 obtained by incrementing 0.

Here, if there are multiple pieces of server information to be acquired based on the judgment of the judgment content that has the last judgment rank, the number obtained by incrementing the number of allocation ranks stored most recently is stored in the column of allocation ranks of the server information located at the top of management table 21(a), and the number obtained by incrementing the number of allocation ranks stored most recently is stored in the column of allocation ranks of the server information located at the bottom of management table 21. This process is repeated.

The allocation rank determination means further searches the management table 21(a) to identify rows in which no allocation rank is stored, and repeats the operations described above for the identified rows to repeatedly store the allocation rank. The allocation rank is incremented and stored, so that the same allocation rank is not stored.

Furthermore, when the information in a column other than the allocation rank in management table 21(a) is updated, the allocation rank determination means deletes the information in the allocation rank column and stores the allocation rank by repeating the operation described above. In this case, the number of allocation ranks stored immediately before is set to 0, and the operation described above is started.

In the present invention, the allocation rank determination means has in advance a determination rank table 41 shown in FIG. 4, searches the management table 21(a) based on the determination rank table 41, makes a determination, and stores the number of allocation ranks in the management table 21(a).

The operation of the best mode for implementing the invention configured as described above will be explained using Figures 2, 3, 4, and 5.

First, the HSS 14 uses the information acquisition means to connect to each of the multiple S-CSCF servers 15-17 using SNMP, collects the MIB information held by the connected servers, and acquires at least the software status, CPU usage rate, and NW usage rate. (S51)

The information acquisition means acquires the following information from the S-CSCF server 15: software status = normal, CPU usage = 50%, and NW usage = 10%.

The information acquisition means acquires the following information from the S-CSCF server 16: software status = normal, CPU usage = 40%, and NW usage = 10%.

The information acquisition means acquires the following information from the S-CSCF server 17: software status = normal, CPU usage = 40%, and NW usage = 10%.

The information acquisition means provides the information acquired from each of the multiple S-CSCF servers 15-17, as well as the connection destination server information, to the information storage means.

Next, the information storage means has in advance a management table 21(a) shown in FIG. 2, and stores the information provided by the information acquisition means in the management table 21(a).

When the information storage means receives from the information acquisition means the software status = normal, CPU usage = 50%, NW usage = 10%, and server information = S-CSCF server 15, it stores them in the management table 21(a).

When the information storage means receives from the information acquisition means the software status = normal, CPU usage = 40%, NW usage = 10%, and server information = S-CSCF server 16, it stores them in the management table 21(a).

When the information storage means receives from the information acquisition means the software status = normal, CPU usage = 40%, NW usage = 10%, and server information = S-CSCF server 17, it stores them in the management table 21(a).

When the information provided by the information acquisition means is stored, management table 21(a) becomes management table 21(b). The following explanation will be given using management table (b).

Next, a terminal not shown in FIG. 5 sends a REGISTER message not shown in FIG. 5.

The REGISTER message (not shown in FIG. 5) sent by a terminal (not shown in FIG. 5) is received by, for example, the S-CSCF server 16, which performs registration based on the received REGISTER message and transmits a Diameter SAR message when registration is complete. (S52)

Next, the HSS 14 prestores the Diameter SAR information as predetermined information, and monitors packets sent to and received from each of the multiple S-CSCF servers 15 to 17 using information monitoring means.

HSS14 receives the Diameter SAR message sent by S-CSCF server 16.

When HSS 14 receives a Diameter SAR message, it detects the reception using the information monitoring means and obtains server information (S-CSCF server 16) which is the server information of the sender of the Diameter SAR message.

The information monitoring means provides the server information (S-CSCF server 16) of the sender of the acquired Diameter SAR message to the information storage means.

Here, the information storage means has a maximum capacity table 31(a) shown in FIG. 3 in advance, and the maximum capacity table 31(a) stores server information and the maximum capacity in advance.

The maximum capacity table 31(a) prestores server information = S-CSCF server 15 and maximum capacity = 100.

The maximum capacity table 31(a) prestores server information = S-CSCF server 16 and maximum capacity = 100.

The maximum capacity table 31(a) prestores server information = S-CSCF server 17 and maximum capacity = 50.

Furthermore, the maximum capacity table 31(a) stores the current capacity of the server of the S-CSCF server 15 as server information, which is capacity = 60.

Furthermore, the maximum capacity table 31(a) stores the current capacity of the server of the server information = S-CSCF server 16, which is capacity = 49.

Furthermore, the maximum capacity table 31(a) stores the current capacity of the server of the S-CSCF server 17 as server information, which is capacity = 45.

Then, when the information storage means receives server information, server information = S-CSCF server 16, from the information monitoring means, it searches the maximum capacity table 31(a) using the received server information to identify a row and increments the number of columns for the capacity of the identified row.

If an increment is made here, maximum capacity table 31(a) becomes maximum capacity table 31(b). From here on, explanation will continue using maximum capacity table 31(b).

Furthermore, the information storage means calculates the capacity between the capacity and the maximum capacity based on the maximum capacity table 31(b) by dividing the capacity by the maximum capacity x 100 to derive the capacity rate.

The server information in the maximum capacity table 31(b) = the capacity rate of the S-CSCF server 15 is derived as 60%.

The server information in the maximum capacity table 31(b) = the capacity rate of the S-CSCF server 16 is derived as capacity rate = 50%.

The server information in the maximum capacity table 31(b) = the capacity rate of the S-CSCF server 17 is derived as 90%.

Furthermore, the information storage means stores each derived capacity rate in a management table (b).

If the capacity rate provided by the information storage means is stored here, management table 21(b) will become management table 21(c). The following explanation will be given using management table (c).

Next, the allocation order determination means obtains information on the determination order and the determination content from a pre-stored determination order table 41.

Here, the information on the judgment order and judgment content is as follows: the first judgment content is software status 411, the second judgment content is capacity rate 412, the third judgment content is CPU usage rate 413, and the fourth judgment content is NW usage rate 414.

The allocation order determination means further acquires server information based on the first determination content, software status 411. Software status 411 searches the software status column stored in management table 21(c), determines whether it is described as normal, and acquires server information for S-CSCF server 15, S-CSCF server 16, and S-CSCF server 17 that are described as normal.

The allocation order determination means further searches management table 21(c) using the server information acquired in the first determination content to identify a row, and acquires server information for the identified row based on occupancy rate 412, which is the second determination content. For occupancy rate 412, the means searches the occupancy rate column stored in management table 21(c), determines which has a low occupancy rate value, and acquires server information for S-CSCF server 16 and S-CSCF server 17 that have been determined to have a low occupancy rate value.

The allocation order determination means further searches management table 21(c) using the server information acquired in the second determination content to identify a row, and acquires server information for the identified row based on the third determination content, CPU utilization rate 413. CPU utilization rate 413 searches the CPU utilization rate column stored in management table 21(c), determines which has a low CPU utilization rate value, and acquires server information for the S-CSCF server 16 that has been determined to have a low CPU utilization rate value.

The allocation order determination means further searches the management table 21(c) using the server information acquired in the third determination content to identify a row, and acquires server information for the identified row based on the fourth determination content, NW utilization rate 414. NW utilization rate 414 searches the NW utilization rate column stored in the management table 21(c), determines which has a low NW utilization rate, and acquires server information for the S-CSCF server 16 whose NW utilization rate value is determined to be low.

Furthermore, when the allocation order determination means obtains server information of the S-CSCF server 16 based on the information on the determination content that has the last determination order, it searches the management table 21 using the obtained server information to identify a row, and in the allocation order column of the identified row, it sets the number of allocation orders previously stored to 0, and stores 1, which is the increment of 0.

The allocation order determination means further searches the management table 21(c) to identify rows in which the allocation order is not stored, and repeats the operations described above for the identified rows to repeatedly store the allocation order.

If the capacity rate provided by the information storage means is stored here, management table 21(c) will become management table 21(d). The following explanation will be given using management table (d).

Next, terminal 11 sends a REGISTER message. (S53)

The P-CSCF server 12 receives the REGISTER message sent by the terminal 11 and forwards the received REGISTER message. (S54)

The I-CSCF server 13 receives the REGISTER message transferred by the P-CSCF server 12 and sends a Diameter UAR message to make an inquiry. (S55)

Then, the HSS server 14 receives the Diameter UAR message sent by the I-CSCF server 13, and responds by sending a Diameter UAA message containing the server information and allocation order information stored in the management table (d). (S56)

Next, the I-CSCF server 13 receives the Diameter UAA message sent by the HSS server 14, and based on the server information and allocation order information contained in the received Diameter UAA message, selects the S-CSCF server 16 with an allocation order of 1 as the S-CSCF server to be used by the terminal 1.

Then, the I-CSCF server 13 transfers the REGISTER message received from the P-CSCF server 12 to the S-CSCF server 16. (S57)

Next, the S-CSCF server 16 receives the REGISTER message transferred by the I-CSCF server 13, performs registration based on the received REGISTER message, and when registration is complete, sends a Diameter SAR message. (S58)

As described above, according to the best mode for implementing the present invention, the HSS server acquires the operation status information and subscriber accommodation rate information of each of the multiple S-CSCF servers, determines the allocation order of the S-CSCF servers based on the acquired information, and when queried by the I-CSCF server, responds with the allocation order and the server information of the S-CSCF servers. Therefore, it becomes possible to dynamically assign one of the multiple S-CSCF servers based on the operation status information and subscriber accommodation rate information of each of the multiple S-CSCF servers.

11 terminal 12 P-CSCF server 13 I-CSCF server 14 HSS server 15, 16, 17 S-CSCF server 18 IP network 21 management table 31 maximum capacity table 41 judgment priority table

Claims (21)

In a network having terminals and a plurality of call control functions for controlling communications between the terminals,
an information acquisition means acquires a software status of each of the plurality of call control functions;
A monitoring means acquires terminal accommodation information of each of the plurality of call control functions,
a determining means for determining an allocation order of each of the plurality of call control functions based on the software state and the terminal accommodation information;
A call control function allocation method, characterized in that a response means includes information on the allocation order and the call control functions corresponding to the allocation order in a response to a request from the terminal. 2. The method according to claim 1, wherein the terminal accommodation information is a terminal accommodation rate. 2. The method of claim 1, wherein the request is a registration request. 4. The call control function allocation method according to claim 3, wherein the registration request is a REGISTER of SIP (Session Initiation Protocol). 2. The method of claim 1, wherein the software status is acquired using any one of the following communication protocols: FTP (File Transfer Protocol), HTTP (Hyper Text Transfer Protocol), Telnet, and SNMP (Simple Network Management Protocol). When the determining means determines the allocation order of each of the plurality of call control functions based on the software state and the terminal accommodation information,
3. The call control function allocation method according to claim 2, wherein among said plurality of call control functions, a call control function in which the software state is normal and the terminal accommodation rate is smallest is given a first allocation priority. In the network further comprising a database function,
the database function stores in advance the maximum terminal accommodation numbers of each of the plurality of call control functions;
the monitoring means monitors predetermined information exchanged between each of the plurality of call control functions and the database function to obtain terminal accommodation information for each of the plurality of call control functions;
3. The call control function allocation method according to claim 2, wherein said database function derives said terminal accommodation rate based on said maximum accommodated number of terminals and said accommodated number of terminals. 8. The method according to claim 7, wherein the predetermined information is information related to completion of registration of a terminal. 9. The method of claim 8, wherein the information on the completion of the registration is a Diameter SAR. 8. The method of claim 7, wherein the network corresponds to an IMS (IP Multimedia Subsystem), each of the plurality of call control functions is an S-CSCF (Serving Call Session Control Function), and the database function is an HSS (Home Subscriber Server). 2. The method according to claim 1, wherein the information on the call control function is either a host name or an IP address. A server that assigns a control function that controls communication of a terminal in a network in which the terminal and a plurality of control functions that control communication of the terminal are provided, comprising:
A storage means for storing information;
an information acquisition means for acquiring a software state from each of the plurality of control functions and storing the state in the storage means;
a determination means for determining an allocation priority of each of the plurality of control functions based on the information stored in the storage means;
And,
The server responds to a request from the terminal by including information on the allocation order determined by the determination means and on the control functions corresponding to the allocation order. A monitoring means for acquiring terminal accommodation information of each of the plurality of control functions and storing the information in the storage means;
13. The server of claim 12, further comprising: The server according to claim 13, wherein the terminal accommodation information acquired by the monitoring means is a terminal accommodation rate. The server according to claim 14, wherein the determining means assigns a first priority to a control function among the plurality of control functions, the control function for which the software state is normal and the terminal accommodation rate is smallest. the storage means stores in advance the maximum terminal accommodation numbers of each of the plurality of call control functions;
said monitoring means monitors predetermined information among information exchanged between each of said plurality of control functions and said server, acquires the number of terminals accommodated in each of said plurality of call control functions, and stores the number of terminals accommodated in said storage means;
15. The server according to claim 14, wherein the server derives the terminal accommodation rate based on the maximum accommodated terminal number and the accommodated number of terminals. 17. The server according to claim 16, wherein the predetermined information is information relating to completion of registration of a terminal. The server of claim 17, wherein the information regarding the completion of the registration is a Diameter SAR. 13. The server according to claim 12, wherein the information of the control function is one of a host name and an IP address. I-CSCF (Interrogation Call Session Control)
role Function),
The HSS (Home Subscriber Server) determines the allocation order based on the software status and the number of terminals accommodated in each of a plurality of S-CSCFs (Serving Call Session Control Functions) and transmits allocation order information and server information to the I-CSCF.
An I-CSCF characterized by performing processing to select an S-CSCF with an allocation priority of 1 as an S-CSCF to be used by a terminal based on allocation order information and server information contained in a signal received by the I-CSCF. A communication system including a terminal, a plurality of control functions for controlling communication between the terminal, and a database function,
The database function is
Acquire software status and terminal accommodation information for each of the plurality of control functions;
determining an allocation order of each of the plurality of control functions based on the state of the software and the terminal accommodation information;
A communication system comprising: a terminal that transmits a response to a request from the terminal including allocation order information.

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