JP2010193124A - Session control system in ims - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a mechanism of session control having an improved load distribution mechanism, reducing burdens on a manager, and improving a service level to a user, in an IMS. <P>SOLUTION: Each I-CSCF server has a user management list for managing the allocation information of an S-CSCF server to a user terminal, the allocation information to one user terminal is managed in the user management list managed by one of the I-CSCF servers for specifying which I-CSCF server should manage the allocation information to one user terminal in its user management list. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to Internet communication server technology, and relates to a technology for distributing user information to a plurality of SIP (Session Initiation Protocol) servers that perform session control.

  In recent years, in order to provide services such as telephones, which were conventionally provided by circuit-switched networks, by packet-switched networks based on IP (Internet Protocol) networks by fixed-line operators and mobile phone operators in various countries. Efforts such as examination and construction of a next generation communication system called NGN (Next Generation Network) are being promoted.

In NGN, a protocol called SIP (Session Initiation Protocol) is used for call control such as specifying an IP address from a telephone number of a call destination, setting or releasing a communication connection, and the like. A common platform for realizing various multimedia services based on this SIP is an architecture called an IP multimedia subsystem (hereinafter referred to as IMS). (See Non-Patent Document 1)
IMS mainly includes P-CSCF (Proxy-CSCF, Proxy Call Session Control Function), I-CSCF (Interrogating-CSCF, Interrogating Call Session Control Function), and S-CSCF (Serving-CSCF, Serving Call Session Control Function). It searches for which HSS registered subscriber information called SLF (Subscription Locator Function) and a basic SIP server group having a function called HSS, a subscriber information management database called HSS (Home Subscriber Server) Containing a database for.

  The P-CSCF is connected from the user terminal, receives the SIP message from the user terminal, and relays it to the I-CSCF and S-CSCF.

  When an IP address is registered from a user terminal (REGISTER request) or when an IP phone call is received from another user terminal, the I-CSCF first accesses the SLF to register the subscriber information of the target user. Specify the HSS. Then, the specified HSS is accessed and the stored subscriber information is acquired. The subscriber information includes information indicating which S-CSCF is in charge of the user when there are a plurality of S-CSCFs. Based on the information, the I-CSCF takes over the processing to the S-CSCF in charge of the user.

  As an SIP registration server, the S-CSCF manages subscriber information received from the HSS and the current IP address of the user terminal, and performs session control for IP telephones between users.

  One or more server devices constituting the IMS may be configured so as to have any one of the functions of P-CSCF, I-CSCF, and S-CSCF. The server device may have a plurality of arbitrary functions. Further, one server device may be provided with a plurality of any of the functions, and the load may be distributed. Hereinafter, a P-CSCF server, an I-CSCF server, and an SCSCF server, which are provided in independent server devices with the above functions, will be described.

  Processing of IP communication (for example, telephone) by SIP is performed as follows. The user terminal that initiates the call is referred to as the calling side, and the user terminal that receives the call is referred to as the called side.

  First, a SIP message indicating the start of a call is relayed in order from the originating user terminal via the originating P-CSCF, S-CSCF, and terminating I-CSCF. The I-CSCF inquires of the HSS which destination S-CSCF is in charge of the user terminal of the call destination based on the call destination SIP-URI included in the SIP message. It transmits to the communication terminal via the called side P-CSCF. Thus, in IMS, various CSCF server groups and HSS are used for a user terminal to make a call.

  Here, IMS requires a procedure for determining an S-CSCF that is responsible for session control of each user terminal from among a plurality of S-CSCFs arranged in the home network of the user terminal. With respect to this procedure, the conventional technique has been realized by the following method.

  (Method 1) The P-CSCF that has received the REGISTER request from the user terminal makes an inquiry to the I-CSCF. The I-CSCF that receives the inquiry first accesses the SLF, specifies the HSS in which the subscriber information of the user is registered, requests the HSS from the S-CSCF list belonging to the home network, and receives it. .

  The I-CSCF determines an S-CSCF in charge of registration of the user terminal that has transmitted the registration request based on the received list in a predetermined fixed order. Then, the determined S-CSCF is registered in the HSS in association with the user terminal.

  (Method 2) The difference from Method 1 is that the HSS manages priority information for allocating user terminals for each S-CSCF, and the allocation priority is determined based on the number of registered user terminals and the load in each S-CSCF. It is a point determined according to the occurrence situation. In (Method 1), when receiving the S-CSCF list request from the I-CSCF and transferring it to the I-CSCF, in Method 2, the HSS determines the S-CSCF to be allocated according to the allocation priority, and the request source To the I-CSCF. The I-CSCF allocates the S-CSCF determined by the HSS to the user terminal. (See Patent Document 1)

JP 2008-236183 A

Gonzalo Camarillo and Miguel A. Garcia-martin, "The 3G IP Multimedia Subsystem (IMS): Merging the Internet and the Cellular Worlds", John Wiley & Sons Inc., 2004.

In IMS, a procedure for determining an S-CSCF in charge of session control of each user terminal from among a plurality of S-CSCFs arranged in the home network of the user terminal is required. However, the above method has the following problems.
In Method 1, the number of user terminals to be registered cannot be evenly distributed among the S-CSCFs, and there is a possibility that the load is concentrated on a specific S-CSCF. In the conventional system, before the registration request from the user terminal is relayed to the S-CSCF, the I-CSCF first accesses the SLF to identify the HSS, and then accesses the identified HSS to identify the S-CSCF. Need to be identified. For this reason, two remote accesses are required. As a result, there is a problem that the response time to the user becomes long due to the delay time of these accesses.
In method 2, since the HSS manages the user terminal registration number information and load information of each S-CSCF in a lump, when the number of user terminals increases, inquiries to the HSS itself are concentrated and the load becomes heavy. In this case, the SLF can distribute the HSS by responding to the HSS in which the subscriber information of the user is registered, but even in that case, the inquiries to the SLF are concentrated and the load becomes heavy. , Does not solve. Furthermore, since a server for SLF has to be prepared, there is a new problem that the equipment cost becomes high.

In summary, the conventional IMS has the following problems to be solved.
(Problem 1) Even when the load is distributed by a plurality of S-CSCFs, the load may be biased to a specific S-CSCF.
(Problem 2) In the conventional system, since the remote access is required twice before the registration request from the user terminal is relayed to the S-CSCF, the response time to the user becomes long and the service is deteriorated.
(Problem 3) As the number of user terminals increases, the load on the HSS that manages which user terminals are registered in which S-CSCF is concentrated, and the capital investment cost for the countermeasures increases, The service will be degraded, such as the response will be degraded.
(Problem 4) When an S-CSCF is added, it is necessary to move data from the existing S-CSCF to the added S-CSCF, which places a heavy burden on the S-CSCF.

  That is, in IMS, there is a need for a session control mechanism that has a more improved load distribution mechanism, reduces the burden on the administrator, and improves the service level for the user.

  The present invention provides a session control system having the following features.

  (Feature 1) Each I-CSCF in the session control system of the present invention has an S-CSCF management list for managing information (IP address, etc.) related to the S-CSCF included in the system. Each I-CSCF uniquely manages the number of user terminals registered in each S-CSCF by “number of registered users” which is one of the items. When each I-CSCF selects an S-CSCF for registering information on a new user terminal, the I-CSCF determines an S-CSCF with the smallest number of user terminals registered in its own S-CSCF management list. .

  Since the number of registered users is small = it is considered that the load is light, it is possible to register a new user terminal in the lightly loaded S-CSCF by the above method, and thus it is possible to prevent a load bias. . Since the number of newly registered new user terminals is not reflected in the number of registered users of the S-CSCF managed by other I-CSCFs, the number of registered users in the management list of each I-CSCF is different. However, since new users are registered so that the number of registered users is equalized in each I-CSCF, the total number of registered users can be expected to be substantially uniform, and it is possible to prevent an uneven load. .

  Further, as described above, the I-CSCF determines the registration destination S-CSCF by referring to its own S-CSCF management list. Therefore, the load on the access to the S-CSCF management list can also be distributed. It becomes possible.

  The feature 1 makes it possible to solve the problem 1.

  (Feature 2) The I-CSCF in the session control system of the present invention has a user management list for managing which user terminal is registered in which S-CSCF. User terminals registered in a certain S-CSCF are managed by this user management list. Thereby, even when the S-CSCF is added, it is not necessary to move data to the added S-CSCF. In addition, since the subscriber information “Which information such as the user's IP address is registered in which S-CSCF”, which is conventionally managed by the HSS, can be managed only by the I-CSCF. Is not necessary, and access for inquiries to the HSS is reduced, the load is lightened, and high-speed response is possible.

  This feature 2 makes it possible to solve the problem 4.

(Characteristic 3) The session control system of the present invention does not centrally manage the above-mentioned user management list by one I-CSCF but distributes and manages them by a plurality of I-CSCFs. In order to realize this, the correspondence relationship between the SIP-URI and the I-CSCF that manages the user management list is managed by each I-CSCF. As a method for realizing the correspondence, for example, the consistent hash method disclosed in the following document is applied.
(1) US Pat. No. 6,430,618 specification (2) “Tom White's Blog: Consistent Hashing”, [online], [searched on January 22, 2009], Internet <URL: http://weblogs.java.net/ blog / tomwhite / archive / 2007/11 / consistent_hash.html>
Specifically, in advance, the system administrator inputs the ID of each I-CSCF into a hash function to obtain a hash value, and creates a table in which the obtained hash values are arranged in descending or ascending order. The I-CSCF that has received the request from the user terminal that is the access source uses the hash value of the user terminal ID (for example, SIP-URI) as the user ID and the hash having the same length as the hash value of the ID of the I-CSCF. An I-CSCF that is calculated using a hash function that outputs a value and has a value that is equal to or greater than (or less than) the obtained hash value and that is the closest to the I-CSCF that manages the user management list for the user terminal decide. The I-CSCF that has received the request from the user terminal requests the contents of the user management list for the user terminal from the determined I-CSCF.

  The I-CSCF that has received the request for the contents of the user management list assigns the S-CSCF to the user terminal according to the above-described feature 1 when the user terminal is not yet registered in any S-CSCF. If already registered, the contents of the access source user terminal registered in the user management list are returned to the requesting I-CSCF. According to this method, even when the number of user terminals increases, it is possible to load balance access to the user management list to each I-CSCF.

  Even when the number of I-CSCFs is increased with the increase in the number of user terminals, it is only necessary to move some of the user information managed by the I-CSCF, which simplifies the processing. Specifically, for example, among user information managed by the I-CSCF with the next largest (or next smallest) I-CSCF hash value, the hash value of the user terminal ID is the new I-CSCF. What is necessary is just to move the user information below (or more than) the hash value of ID.

  The feature 3 can solve the problem 3. The feature 3 is not intended for the data arrangement itself but for the arrangement of information (user management list) for managing the data. For this reason, unlike the method disclosed in the above document, no data movement occurs between the S-CSCFs. In general, since the S-CSCF is a heavily loaded server having a database, according to the feature 3, it is possible to avoid heavy processing such as moving and deleting data on the database during service.

  Also, by combining the above features 2 and 3, it becomes possible to manage only the I-CSCF information about which user's subscriber information is registered in which I-CSCF. Therefore, in order to relay the registration request from the user terminal to the S-CSCF, the I-CSCF only needs to access the I-CSCF that manages the user management list of the user once. That is, since the conventional SLF is not required, the equipment cost can be reduced, and the remote access delay time can be shortened, so that the response time to the user can be shortened.

  The combination 2 can solve the problem 2.

A more specific aspect of the present invention includes a plurality of I-CSCF servers and a plurality of S-CSCF servers, performs SIP communication with a user terminal, and performs registration and session control of the user terminal. A session control system in the IMS in charge of any of the S-CSCF servers assigned to a terminal,
The session control system in the IMS is
Each of the I-CSCF servers includes a user management list that manages allocation information of the S-CSCF servers to the user terminals,
The allocation information to one user terminal is managed by the user management list managed by any one of the I-CSCF servers,
Each of the I-CSCF servers uses an I-CSCF management table used to identify which allocation information to one user terminal is managed by the user management list included in which I-CSCF server. It is characterized by comprising.

Furthermore, the session control system in the IMS is
In the SIP method in the SIP communication, the I-CSCF server requested to specify the S-CSCF server allocated to the user terminal is the I-CSCF server that should manage the allocation information to the target user terminal. Based on the I-CSCF management table,
Request the allocation information to the target user terminal from the identified I-CSCF server,
The requested I-CSCF server may have a feature that the allocation information to the target user terminal is returned based on the user management list managed by the I-CSCF server.

Furthermore, in the session control system in the IMS,
The I-CSCF management table associates a hash value obtained by inputting the identifier of the I-CSCF server into a first hash function and information for communicating with the I-CSCF server. ,
The I-CSCF server requested to specify the S-CSCF server inputs the identifier of the target user terminal into a second hash function that outputs a hash value having the same length as the hash value, Find the hash value of the user terminal identifier,
The requested S-CSCF server may be specified based on the hash value of the user terminal identifier and the I-CSCF management table.

Furthermore, in the session control system in the IMS,
The SIP method includes at least an INVITE request for starting a session from the user terminal to another user terminal, or a REGISTER request for registering the IP address information of the user terminal in the S-CSCF server device. , May be.

Furthermore, in the session control system in the IMS,
The I-CSCF server includes an S-CSCF server management list for managing the number of user terminals allocated to each S-CSCF server,
The I-CSCF server
When the allocation information to the target user terminal is not managed by the user management list managed by itself, the S-CSCF server management list is referred to and the S-CSCF having the smallest number of user terminals is referred to. Assigning a server to the target user terminal and updating the user management list;
A feature of responding to the allocation information to the target user terminal based on the updated user management list may be provided.

Furthermore, in the session control system in the IMS,
The identifier of the I-CSCF server is an IP address,
The user terminal identifier is a SIP-URI;
The first hash function and the second hash function may be the same.

Due to the above features, the session control system of the above aspect has the following effects.
(Effect 1) When there are a plurality of S-CSCFs, it is possible to prevent the load from being biased toward a specific S-CSCF.
(Effect 2) Even when the S-CSCF is added, data transfer from the existing S-CSCF to the added S-CSCF can be made unnecessary. As a result, it is not necessary to place a burden on the S-CSCF during service.
(Effect 3) Information for managing which S-CSCF accommodates which user terminal is distributed and managed in a plurality of I-CSCFs, and the I-CSCF is increased as the number of user terminals increases. Even in the case of expansion, it is only necessary to move part of the information managed by one I-CSCF, and the processing becomes simple, so that the load of the system itself can be distributed.
further,
(Effect 4) Since the access until the I-CSCF relays the registration request from the user terminal to the S-CSCF is one time, as a result, the access delay time is shortened and the response time to the user is shortened. be able to. In addition, the number of servers can be reduced and the equipment cost can be reduced.

  According to the present invention, it is possible to realize an IMS network that can provide a high-level service to a user with less burden on an administrator.

It is a figure which illustrates the structure of IMS in this embodiment. It is a figure which illustrates the structure of an I-CSCF management table. It is a figure which illustrates the structure of an S-CSCF management list. It is a figure which illustrates the composition of a user management list. In this embodiment, it is a sequence diagram which illustrates the process at the time of receiving the REGISTER request | requirement from a user terminal. FIG. 6 is a sequence diagram illustrating details of processing in S12 to S14 in FIG. 5. In this embodiment, it is a sequence diagram which illustrates the addition process in I-CSCF when S-CSCF is newly expanded. It is a figure which illustrates the hardware constitutions of each server in this embodiment.

  The best mode for carrying out a SIP relay device according to the present invention will be described below with reference to the drawings.

  FIG. 1 is a system configuration diagram illustrating an example of a configuration of an IMS according to the present embodiment. The system of FIG. 1 is configured such that each function of the P-CSCF 11, the I-CSCF 12, and the S-CSCF 13 is provided in a physically independent server device, and the user terminal 10 is connected to a network such as the Internet. 14 is connected.

  The user terminal 10 communicates with the I-CSCF 12 via the P-CSCF 11. The I-CSCF 12 includes an I-CSCF management table 121, an S-CSCF management list 122, and a user management list 123, and further, a SIP session processing unit for processing a SIP session similar to a known general I-CSCF And a distributed database management unit 125 that makes a request for access to another user management list 123 managed by another I-CSCF and a response to a request from another I-CSCF. The I-CSCF 12 manages IP address information necessary for connecting to another I-CSCF 12 using the I-CSCF management table 121.

  FIG. 2 shows an example of the I-CSCF management table 121. The I-CSCF management table 121 is a table for managing the ID 12111 of the I-CSCF 12, the IP address 12112 of the I-CSCF 12, and the hash value 12121 of the ID 12111 of the I-CSCF 12 in association with each other. The ID 12111 of the I-CSCF 12 is identifier information by a character string that is uniquely assigned to the I-CSCF 12.

  The I-CSCF management table 121 includes an I-CSCF table 1211 and a hash table 1212 for managing all I-CSCFs. The I-CSCF table 1211 is a list for managing the I-CSCF ID 12111 and the IP address 12112 in association with each other.

  The hash table 1212 is a table for performing a hash search of the ID 12111 of the I-CSCF from the I-CSCF table 1211 and manages the hash value 12121 of the ID 12111 of the I-CSCF. In this example, the ID 12111 of the I-CSCF is the host name (FQDN format) of the I-CSCF 12. The ID 12111 of the I-CSCF may be generated from the IP address 12112 based on a predetermined rule.

  The hash value 12121 of the ID 12111 of the I-CSCF is a fixed-length numerical value (digest value) calculated by inputting the ID 12111 of the I-CSCF into a hash function. In the example of FIG. 2, the size of the hash space is 32 bits (0x00000000 to 0xFFFFFFFF). A known algorithm can be used for the hash function. For example, when MD5 (Message Digest Algorithm 5) is used, the size of the hash space is 128 bits.

The I-CSCF 12 calculates a responsible I-CSCF 12 to which an S-CSCF 13 responsible for registration of a certain user terminal 10 is assigned based on the consistent hash method disclosed in the above document. For example, it is calculated as follows.
(1) The SIP-URI of the user terminal 10 is input to a hash function to calculate a hash value. Here, when a REGISTER request is received as the SIP method, the SIP-URI described in the From header (area indicating the transmission source of the request) is targeted. When an INVITE request is received, the SIP-URI described in the request line is targeted.

  The hash function used in this process is to output a hash value having the same bit length as the hash function used to create the hash table 1212 (the same hash function may be used). Same hash function used.

Due to the nature of the hash function, even if the ID 12111 of the input I-CSCF is different from the SIP-URI length of the user terminal 10, the obtained hash values have the same length.
(2) Use the hash table 1212 of the I-CSCF management table 121 to search for the closest hash value of the ID of the I-CSCF that is greater than (or less than) the hash value of the SIP-URI calculated in (1). . For this reason, it is desirable that the hash table 1212 sorts the entries in ascending or descending order of the hash value 12121. (3) The value of the IP address 12112 corresponding to the entry having the hash value 12121 obtained by the search in (2) is used as the IP address of the I-CSCF 12 in charge of the user terminal 10.

  Each I-CSCF 12 includes an S-CSCF management list 122. As will be described later, each I-CSCF 12 manages the same S-CSCF 13, but each “number of users registered in the S-CSCF 13” has a different value for each I-CSCF 12.

  FIG. 3 shows an example of the S-CSCF management list 122. The S-CSCF management list 122 manages the ID 12221 of the S-CSCF, the IP address 12222 of the S-CSCF 13, and the number of registered users 12223 in a list format. The ID 12221 of the S-CSCF is identifier information by a character string that is uniquely assigned to the S-CSCF 13. In this example, the S-CSCF ID 12221 is the host name of the S-CSCF 13 (FQDN format). Alternatively, the IP address 12222 may be generated based on a predetermined rule. The number of registered users 12223 is the number of users accommodated in each S-CSCF 13. The number of registered users 12223 is corrected by the I-CSCF 12 every time the number of users accommodated by the S-CSCF 13 increases (details will be described later).

  Further, the I-CSCF 12 includes a user management list 123.

  FIG. 4 shows an example of the user management list 123. The user management list 123 includes a user management structure 1233 managed in a list format and a hash table 1231 for performing a hash search. The hash table 1231 includes fields for a SIP-URI hash value 12311 and pointer information 12312 to the user management structure 1233. The SIP-URI hash value 13211 is a fixed-length numerical value calculated by inputting the SIP-URI into a hash function.

  The hash function used here outputs a hash value having the same bit length as the hash function used to calculate the hash value 12121 of the ID 12111 of the I-CSCF (the same hash function may be used).

  If there is no hash value 12311 in the hash table 1231, the user management structure 1233 does not exist, so the value stored in the pointer information 12312 is set to NULL. When there is a SIP-URI corresponding to the hash value 12311, since the user management structure 1233 exists, a pointer to the user management structure 1233 is set.

  The user management structure 1233 includes the SIP-URI information 12331, the ID 12332 of the S-CSCF 13 of the user terminal registration destination, the entry state 12333, and the user management structure having the next (the SIP-URI 12331 having the same hash value 12311). This structure includes a pointer 12334 to the body 1233 as a member. The SIP-URI 12331 is SIP format user identifier information using a character string that is uniquely assigned to each user terminal 10. The entry state 12333 is an area for setting the entry state.

  There are two types of entry states 12333: “Preparing for creation” and “Complete”. When the entry state 12333 is “complete”, the I-CSCF 12 can respond to the search request from the P-CSCF.

  On the other hand, if the entry status 12333 is “preparing for creation”, the processing for the search request is suspended until the status changes to “complete”. This prevents a situation where search requests received from a plurality of I-CSCFs 12 are overlapped to create a plurality of user management structures 1233 having the same SIP-URI.

  Each I-CSCF 12 requests all other I-CSCFs 12 to set information related to the I-CSCF 12 in the respective I-CSCF management tables 121 at the time of activation.

  An example of a hardware configuration for realizing the P-CSCF 11, the I-CSCF 12, and the S-CSCF 13 is shown in FIG. These include a CPU 1001, a main storage device 1002, a secondary storage device 1005 such as an HDD, a reading device 1003 that reads information from a portable storage medium 1008 such as a CD-ROM or DVD-ROM, a display, a keyboard, a mouse, etc. It can be realized by a general computer 1000 having an input / output device 1006, a communication device 1004 such as a NIC (Network Interface Card) for connecting to a communication network, and an internal communication line 1007 such as a bus connecting these devices.

  For example, the I-CSCF management table 121, the S-CSCF management list 122, and the user management list 123 are realized using a partial area of the main storage device 1002 or the secondary storage device 1005. Further, the P-CSCF 11, the I-CSCF 12, and the S-CSCF 13 load one or more programs stored in the secondary storage device 1005 into the main storage device 1002 and execute them by the CPU 1001, via the communication device 1004. By performing network communication with the user terminal 10 and other servers, various server functions described above or described below are realized.

  The one or more programs may be stored in advance in the main storage device 1002 or the secondary storage device 1005, and when necessary, other programs may be stored via the network 14 or the portable storage medium 1008. It may be introduced from the device.

  FIG. 5 is a sequence diagram showing processing when a REGISTER request is received as the SIP method from the user terminal 10 in the system configuration of the present embodiment.

  When the I-CSCF 12a receives the REGISTER request from the user terminal 10 via the P-CSCF 11, the I-CSCF 12 is in charge of managing the user terminal 10 from the sender SIP-URI in the From header of the REGISTER request. Specifically, a hash value of the caller SIP-URI is calculated using a hash function, the hash table 1212 of the I-CSCF management table 121 is searched, and the calculated hash value is greater than (or less than) and the highest. A close hash value 12121 is obtained. Information of the I-CSCF 12 in charge is stored in the entry of the I-CSCF table 1211 pointed to by the obtained entry pointer 12122 (S10).

  As a preliminary preparation, the system administrator creates a hash table 1212 in which hash values of IDs of the respective I-CSCFs 12 are arranged in ascending order or descending order, and sets the hash table 1212 using a management terminal (not shown).

  A search request for the S-CSCF 13 in charge of SIP-URI registration of the caller (the user of the user terminal 10) is transmitted to the I-CSCF 12b having the IP address 12112 of the entry obtained in S10 ( S11). The search request preferably includes the caller SIP-URI and further includes the hash value.

  Upon receiving the caller SIP-URI search request from the I-CSCF 12a, the I-CSCF 12b performs a hash search on the hash table 1231 of the user management list 123 based on the SIP-URI hash value included in the search request (S12). ).

  If there is no hit in the hash search (N in S13), it is regarded as a SIP-URI not assigned to the S-CSCF 13, and the S-CSCF 13 with the smallest number of registered users 12223 is searched from the S-CSCF management list 122 and obtained. The determined S-CSCF is assigned to manage the user having the SIP-URI (S14), and the number of registered users 12223 in the S-CSCF management structure 1222 of the determined S-CSCF 13 is counted up. Then, the S-CSCF ID 12221 and the IP address information 12222 determined in S14 are returned to the search request source I-CSCF 12a (S15).

  On the other hand, when a hash search results in a hit (Y in S13), it is regarded as a SIP-URI already assigned to the S-CSCF 13, and the S-CSCF ID 12332 of the hit user management structure 1233 and the S-CSCF management from the ID 12332 The IP address information 12222 obtained by searching the list 122 is returned to the search request source I-CSCF 12a (S15). The I-CSCF 12a that has received the information of the S-CSCF 13 transfers a REGISTER request to the IP address 12222 of the S-CSCF 13 that has been responded in S15 (S16).

  Upon receiving the REGISTER request, the S-CSCF 13 acquires user profile information from the HSS 131 (S17), performs user terminal registration processing according to the profile information, and sends a “200 OK” response indicating a normal response to the I-CSCF 12a. Transmit (S18). Upon confirming the normal response from the S-CSCF 13, the I-CSCF 12a transfers a “200 OK” response to the user terminal 10 via the P-CSCF 11 (S19).

  Details of the processing of S12 to S14 in FIG. 5 will be described with reference to FIG.

(Processing equivalent to S12)
Upon receiving the caller SIP-URI search request from the I-CSCF 12a, the I-CSCF 12b calculates the SIP-URI hash value included in the search request (S20). From the obtained hash value, the user management structure 1233 indicated by the pointer 12312 corresponding to the corresponding hash value 12311 of the hash table 1231 of the user management list 123 is obtained (S21).

(Processing equivalent to S13)
The character string of the SIP-URI 12331 of the user management structure 1233 is compared with the character string of the SIP-URI included in the search request (S22). It is checked whether or not the character strings completely match (S23), and if they match completely (Y in S23), the entry status 12333 is checked. If the entry status 12333 is “preparing for creation”, it waits until it is changed to “completed” (S24). If it is “completed”, the S-CSCF of the user terminal 10 is regarded as already assigned, and the process of S15 is performed. If they do not match completely (N in S23), the next user management structure 1233 is acquired by referring to the address indicated by the next pointer 12334 of the user management structure 1233 (S25). If the next user management structure 1233 exists (N in S26), the process returns to S22. On the other hand, if it does not exist, that is, if the address indicated by the next pointer 12334 is NULL (Y in S26), the S-CSCF of the user terminal 10 is regarded as unallocated, and processing corresponding to S14 is performed.

(Processing equivalent to S14)
First, a new user management structure 1233 is created, and the SIP-URI character string included in the search request is set in the SIP-URI 12331, “Preparing for creation” is set in the entry state 12333, and NULL is set in the next pointer 12334. . Then, the address of the newly created user management structure 1233 is set in the next pointer 12334 of the user management structure 1233 that is currently referenced. Further, the head S-CSCF management structure 1222 is acquired from the head pointer 12211 of the header information 1221 of the S-CSCF management list 122 (S27). The number of registered users 12223 is acquired and compared with the upper limit value of the number of registered users set in the I-CSCF 12 in advance (S28). If it is equal to or smaller than the upper limit value (Y in S28), the S-CSCF ID 12221 of the S-CSCF management structure 1222 acquired earlier is changed to the ID 12332 of the S-CSCF for the user management structure 1233 newly created in S26. “Complete” is set in the entry state 12333. Further, after the value of the number of registered users 12223 is incremented by 1, the S-CSCF management structure 1222 is sorted in ascending order using the number of registered users 12223 in the S-CSCF management list as a key (S-CSCF management in ascending order of the number of registered users). The structures are rearranged) (S29), and the process of S15 is performed. On the other hand, if it is larger than the upper limit (N in S28), it is determined that the state is not normal, and an error response is sent to the search request source I-CSCF 12a (S30).

  When the I-CSCF 12 is added due to an increase in the number of user terminals 10, the I-CSCF management table 121 of all the I-CSCFs 12 is updated using an administrator terminal (not shown). Specifically, for the new I-CSCF 12, the hash value of the ID is obtained, added to the hash table 12121 and re-sorted, and the ID and IP address are added to the I-CSCF table 1211.

  Along with these processes, the administrator terminal moves the user management list 123 of the user terminal to be newly assigned to the new I-CSCF 12. According to the method of the present embodiment, a new I-CSCF 12 of the user management list 123 managed by the I-CSCF 12 having the next larger (or next smaller) hash value than the hash value of the ID of the new I-CSCF 12 is used. The hash table 1231 and the user management structure 1233 of the user terminal 10 having a SIP-URI hash value less than (or more than) the hash value of the ID of the CSCF 12 are moved to the new I-CSCF 12.

  Next, an additional process in the I-CSCF 12 when the S-CSCF 13 is added will be described with reference to FIG. This processing is performed independently by each I-CSCF 12.

  When the administrator terminal instructs the addition of the S-CSCF 13, a new S-CSCF management structure 1222 is created, values are stored in the ID 12221 and IP address 12222 of the S-CSCF, and the number of registered users 12223 is set. It is initialized to 0 (S31). Then, the value indicated by the head pointer 12211 of the header information 1221 is acquired, and the value is stored in the next structure pointer 12224 of the S-CSCF management structure 1222 (S32). Then, the address on the memory of the S-CSCF management structure 1222 is stored in the head pointer 12211 of the header information 1221 (S33). By this processing, the newly added S-CSCF management structure 1222 of the S-CSCF 13 is arranged at the head of the S-CSCF management list 122.

  Since the S-CSCF having the smallest number of registered users is selected by the process of S28 in FIG. 6, the number of registered users in each S-CSCF is gradually averaged.

  Each I-CSCF 12 performs the updating process of the added S-CSCF management structure 1222 independently. Therefore, the number of registered users is different from those managed by other I-CSCFs 12. However, as described above, since each I-CSCF 12 performs the process of equalizing the number of registered users, the number of registered users managed by each S-CSCF 13 is expected to be substantially equal even when viewed from the entire system. it can.

  As described above, according to this embodiment, since the I-CSCF includes the distributed database management unit 125, the conventional SLF becomes unnecessary. Further, according to the present embodiment, the “information about which S-CSCF the user information is stored” stored in the conventional HSS is also stored in the I-CSCF of the present embodiment. The amount is reduced, and access to the HSS 131 is reduced, and the response speed of the entire system is improved.

  Although the REGISTER request process has been described as the SIP method with reference to FIGS. 5 and 6, the INVITE request and other request processes for establishing a session with the communication partner terminal are also performed in S10 to S10 of FIG. The process of S16 is performed similarly.

  In addition, this invention is not limited to the said embodiment, A various deformation | transformation and application are possible.

10: User terminal, 11: P-CSCF, 12: I-CSCF, 13: S-CSCF, 121: I-CSCF management table, 122: S-CSCF management list, 123: User management list, 124: SIP session processing , 125: distributed database management unit, 1211: I-CSCF table, 1212: hash table of I-CSCF table, 12111: ID of I-CSCF, 12112: IP address of I-CSCF, 12121: ID of I-CSCF Hash value, 12122: pointer to entry of I-CSCF table, 1221: header information of S-CSCF management list, 12211: pointer to head S-CSCF management structure, 12212: tail S-CSCF management Pointer to structure, 12221: S-CSC ID: 12222: IP address of S-CSCF, 12223: Number of registered users of S-CSCF, 12224: Pointer to next S-CSCF management structure, 1231: Hash table of user management structure, 1233: User management Structure, 12311: hash value of SIP-URI, 12312: pointer to user management structure, 13331: SIP-URI, 13332: ID of assigned S-CSCF server, 13333: entry state, 13334: next user management structure Pointer to body, 1000: computer, 1001: CPU, 1002: main storage device, 1003: reading device, 1004: communication device, 1005: secondary storage device, 1006: input / output device, 1007: internal communication line, 1008: A portable storage medium.

Claims (6)

A plurality of I-CSCF servers and a plurality of S-CSCF servers are provided, perform SIP communication with a user terminal, and perform registration and session control of the user terminal with any one of the S assigned to the user terminal. A session control system in the IMS in charge of the CSCF server,
Each of the I-CSCF servers includes a user management list that manages allocation information of the S-CSCF servers to the user terminals,
The allocation information to one user terminal is managed by the user management list managed by any one of the I-CSCF servers,
Each of the I-CSCF servers uses an I-CSCF management table used to identify which allocation information to one user terminal is managed by the user management list included in which I-CSCF server. A session control system in IMS, comprising: In the session control system in IMS of Claim 1,
In the SIP method in the SIP communication, the I-CSCF server requested to specify the S-CSCF server allocated to the user terminal is the I-CSCF server that should manage the allocation information to the target user terminal. Based on the I-CSCF management table,
Request the allocation information to the target user terminal from the identified I-CSCF server,
The requested I-CSCF server responds with the allocation information to the target user terminal based on the user management list managed by the I-CSCF server. In the session control system in IMS of Claim 2,
The I-CSCF management table associates a hash value obtained by inputting the identifier of the I-CSCF server into a first hash function and information for communicating with the I-CSCF server. ,
The I-CSCF server requested to specify the S-CSCF server inputs the identifier of the target user terminal into a second hash function that outputs a hash value having the same length as the hash value, Find the hash value of the user terminal identifier,
A session control system in IMS, wherein the requested S-CSCF server is specified based on a hash value of the user terminal identifier and the I-CSCF management table. In the session control system in IMS of Claim 2,
The SIP method includes at least an INVITE request for starting a session from the user terminal to another user terminal, or a REGISTER request for registering the IP address information of the user terminal in the S-CSCF server device. A session control system in IMS, characterized in that In the session control system in IMS of Claim 2,
The I-CSCF server includes an S-CSCF server management list for managing the number of user terminals allocated to each S-CSCF server,
The I-CSCF server
When the allocation information to the target user terminal is not managed by the user management list managed by itself, the S-CSCF server management list is referred to and the S-CSCF having the smallest number of user terminals is referred to. Assigning a server to the target user terminal and updating the user management list;
A session control system in IMS, characterized by responding to the assignment information to the target user terminal based on the updated user management list. In the session control system in IMS of Claim 3,
The identifier of the I-CSCF server is an IP address,
The user terminal identifier is a SIP-URI;
The session control system in IMS, wherein the first hash function and the second hash function are the same.

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