JP5489917B2 - Server load balancing system and method - Google Patents

Description

  The present invention relates to a server load distribution system and method, and more particularly to a server for registering a client in IMS (IP (Internet Protocol) Multimedia Subsystem) (3GPP TS 23.228 v10.1.0 “IP Multimedia subsystem,” June. 2010). The present invention relates to a server load balancing system and method for selecting.

  Specifically, for the purpose of distributing the load of multiple servers using the server selection function and the server information DB, the server selection function displays the server status (capability information, load information, maintenance schedule, reduction, etc.). The server selection method when the client registration request is rejected due to a certain method (for example, load status / failure / maintenance schedule / removal schedule), or when the server does not respond and times out The present invention relates to a server load distribution system and method in which a function reselects an alternative server and continues processing.

  As a conventional method for distributing the server load, there are the following methods.

(A) Server selection method using server selection function (for example, see Non-Patent Document 1):
FIG. 1 shows a functional diagram of a server selection method using a conventional server selection function. FIG. 2 shows a sequence for terminal registration. An example of a list of servers including capability information described below is shown in FIG. The IMS architecture shown in FIG. 1 includes a client (UE) 100, a proxy server (P-CSCF) 200, a server selection function (I-CSCF) 300, a server (S-CSCF) 400, and a server information DB (HSS) 500. Is done.

  When the client 100 registers with the server, the proxy server (P-CSCF) 200 and the server selection function (I-CSCF) 300 accept a registration request from the client (UE) (steps 11 and 12). The server selection function 300 makes a list of servers including capability information as shown in FIG. 3 (for example, server URI, IP address, server service type, server processing speed, server information DB (HSS) 500). Requesting whether or not there is charge management capability (step 13), and obtaining (step 14). The server selection function (I-CSCF) 300 compares this capability information with the capability required for the service, selects an appropriate server for the client (UE), and transmits a registration request (step 15).

  At this time, if the selected server does not respond due to an overload or the like, the server selection function (I-CSCF) 300 does not have a method for selecting another server, so registration is not completed and registration fails. .

(A) Redirection destination selection method by an overload server using LDF (Load Detection Function) (for example, see Non-Patent Document 2):
FIG. 4 shows a functional diagram of a redirect selection method by an overload server using LDF. FIG. 5 shows a sequence for terminal registration.

  The load information collection function (LDF) 600 in FIG. 4 periodically receives notification of the load information of each server 400 from each server 400, accumulates the load information in the storage means, and notifies and holds the plurality of servers 400. . Each server 400 shares not only itself but also load information of other servers 400.

When the client 100 performs registration with the server, the proxy server (P-CSCF) 200 and the server selection function (I-CSCF) 300 accept a registration request from the client 100 (steps 41 and 42). The server selection function (I-CSCF) 300 requests the server information DB 500 for a list of servers including capability information (step 43) and acquires it (step 44). The server selection function (I-CSCF) 300 uses this capability information to select an appropriate server for the client 100 and transmits a registration request (step 45). When the server (for example, S-CSCF400 ₁ ) that has received the registration request is overloaded, the server S-CSCF400 ₁ is configured based on the shared load information, for example, a low-load server (for example, S-CSCF400 ₁ ). The server selection function 300 is notified of redirection to -CSCF400 ₂ ) (step 46). In response to this, the server selection function (I-CSCF) 300 transmits a registration request again to the alternative server (S-CSCF400 ₂ ) (step 47).

3GPP TS 24.229 v10.0.0 "IP multimedia call control protocol based on Session Initiation Protocol (SIP) and Session Description Protocol (SDP); Stage 3," June. 2010. [3] 3GPP TR 23.812 v1.1.0 "Feasibility Study on IMS Evolution," June.2010

  When an additional function such as the LDF of the prior art (a) is used, equipment for realizing the additional function is required, leading to an increase in cost. For this reason, without additional functions, it is required to register with the server (S-CSCF) in a low load state without registering with the server (S-CSCF) in an overload state. Further, when the server selection function (I-CSCF) selects the registration destination server (S-CSCF), it is required to reflect the capability information of the server (S-CSCF).

  In the prior art (a), when the S-CSCF that selected and sent the message once rejects the message, or when a timeout occurs, there is no way for the I-CSCF to select another S-CSCF. . For this reason, even when some S-CSCFs are available and other S-CSCFs are available, the S-CSCFs cannot be used.

  In the prior art (a), if the S-CSCF that selected and sent the message once rejects the message or if a time-out occurs, the S-CSCF replaces the S-CSCF with the load information. This method is specified, but this method requires a load information collection / notification function (LDF). In addition, when specifying an alternative S-CSCF, there is no specified method for using S-CSCF capability information as a selection criterion. Therefore, if S-CSCF capability information is not used as an alternative S-CSCF selection criterion, I- When the alternative S-CSCF specified for the S-CSCF is used by the CSCF, there is a possibility that processing cannot be performed because it does not match the capability required by the UE.

The present invention has been made in view of the above points, and when the specific server cannot perform processing,
(A) cannot use other available servers,
(B) Since the server determines an alternative server based on the load information of the server, an additional function called a load information collection function is required.
(C) Server capability information is not used to determine an alternative server;
An object of the present invention is to provide a server load distribution system and method that can continue the processing while distributing the load of a plurality of servers.

In order to solve the above problems, the present invention (Claim 1) is a server load balancing method in a system for selecting a server to register a client in an IMS architecture,
at least,
The client terminal used by the user,
A storage device for holding a server information list regarding the status of the session control server, including client user information and session control server capability information;
A session control server for call control;
A server selection device that accepts a registration request from a client and selects a session control server with a low load;
In a system having
The server selection device is
When a registration request is acquired from the terminal of the client, the server selection step of acquiring the server information list by accessing the storage device, storing it in a server information list storage means, and selecting a session control server for registering the client When,
A registration request step for transmitting the registration request to the session control server selected in the server selection step;
When registration is rejected from the session control server or when a timeout occurs, another server is selected from the server information list storage means, and the registration request is sent to the other session control server. and alternate server selection step of transmitting, to have a row,
In the server selection step,
Session control for deleting a session control server that does not satisfy the essential conditions from the server information list stored in the server information list storage means, and transmitting the registration request according to the capability information and load status of each session control server Select the server
In the alternative server selection step,
If registration is rejected from the session control server, record the number of rejections in the server information list storage means, if registration is successful, record the number of successful registrations,
Weighting is performed based on the session control server capability information stored in the server information list storage means, the session control server rejection rate or the rejection count obtained from the registration success count and the rejection count, and the weight Select a session control server based on.

Further, the present invention (Claim 2 ) is the server selection step or the alternative server selection step.
With reference to the capability information of the session control server in the server information list storage means, the session control servers are selected in descending order of the rate that matches the capability required by the client.

The present invention (Claim 3 ) is a server load balancing system for selecting a server for registering a client in the IMS architecture,
at least,
The client terminal used by the user,
A storage device for holding a server information list regarding the status of the session control server, including client user information and session control server capability information;
A session control server for call control;
A server selection device that accepts a registration request from a client and selects a session control server with a low load;
Have
The server selection device includes:
When a registration request is acquired from the client terminal, the server information list is acquired by accessing the storage device, stored in a server information list storage means, and a server selection means for selecting a session control server for registering the client When,
Registration request means for transmitting the registration request to the session control server selected by the server selection means;
When registration is rejected from the session control server or when a timeout occurs, another server is selected from the server information list storage means, and the registration request is sent to the other session control server. and alternate server selecting means for transmitting, to possess,
The server selection means includes
A session control server that deletes a session control server that does not satisfy essential conditions from the server information list stored in the server information list storage means, and transmits the registration request according to the capability information and load status of each session control server Including means for selecting
The server selection means or the alternative server selection means
If registration is rejected from the session control server, the number of rejections is recorded in the server information list storage means, and if the registration is successful, means for recording the number of successful registrations;
Weighting based on the session control server capability information stored in the server information list storage means, the session control server rejection rate or the rejection count obtained from the registration success count and the rejection count, Means for selecting a session control server based on.

The present invention (Claim 4 ) provides the server selection means or the alternative server selection means,
Means for referring to the capability information of the session control server in the server information list storage means and selecting the session control server in descending order of the rate matching the capability required by the client;

The present invention (Claim 5 ) includes at least
The client terminal used by the user,
A storage device for holding a server information list regarding the status of the session control server, including client user information and session control server capability information;
A session control server for call control;
A server selection device that accepts a registration request from a client and selects a session control server with a low load;
And a server selection device in a server load balancing system that selects a server for registering a client in the IMS architecture,
When a registration request is acquired from the client terminal, the server information list is acquired by accessing the storage device, stored in a server information list storage means, and a server selection means for selecting a session control server for registering the client When,
Registration request means for transmitting the registration request to the session control server selected by the server selection means;
When registration is rejected from the session control server or when a timeout occurs, another server is selected from the server information list storage means, and the registration request is sent to the other session control server. An alternative server selection means for transmitting,
The server selection means includes
Session control for deleting a session control server that does not satisfy the essential conditions from the server information list stored in the server information list storage means, and transmitting the registration request according to the capability information and load status of each session control server A means of selecting a server,
Or
Means for referring to the capability information of the session control server in the server information list storage means, and selecting the session control server in descending order of the rate matching the capability required by the client;
Or
When registration is rejected from the session control server, the number of rejections is recorded in the server information list storage means. When registration is successful, the number of successful registrations is recorded and stored in the server information list storage means. capability information of the session control server is, rejection rate of the session control server obtained from the registration number of successful and the refusal number or based on the refusal number weighted, selects a session control server based on the heavy wear Means ,
Including at least one of
The alternative server selection means includes
When registration is rejected from the session control server, the number of rejections is recorded in the server information list storage means. When registration is successful, the number of successful registrations is recorded and stored in the server information list storage means. capability information of the session control server is, rejection rate of the session control server obtained from the registration number of successful and the refusal number or based on the refusal number weighted, selects a session control server based on the heavy wear means,
Or
Reference is made to the capability information of the session control server in the server information list storage means, and at least one of the means for selecting the session control server in descending order of the rate matching the capability required by the client is included.

The present invention (Claim 6 ) is a server load distribution program for causing a computer to function as each means constituting the server selection apparatus according to Claim 5 .

  (1) When the server selection function selects a server, not only the server capability (eg, service type, server processing speed, presence / absence of billing management capability), but also the server status (eg, load status, maintenance schedule, failure) Information, planned removal, etc.).

  (2) Also, when the load is biased to a specific server, by registering with other servers where the load is below a certain level without registering any more on the server where the load is above a certain level, Load distribution is possible. In addition, since this load information collecting function is not used for this realization, such an additional function is unnecessary. Further, when selecting an alternative server, it is possible to select a server having an appropriate capability using a list of servers including capability information possessed by the server selection function.

  Note that, due to the effect (1) described above, even when the processing capabilities of a plurality of servers are different, it is possible to apply the technique to a technique for fixing the load factor of each server.

It is a system configuration diagram consisting of UE, CSCF and HSS in IMS architecture. This is a terminal registration sequence in the IMS architecture. It is an example of the list | wrist of the server containing capability information. It is a functional diagram of a server redirection method using LDF. This is a server redirection sequence using LDF (until the Register arrives at the alternative S-CSCF). It is a block diagram of I-CSCF in one embodiment of this invention. It is an example of the information which HSS in one embodiment of this invention has. It is an example of the list | wrist of S-CSCF containing the capability information which I-CSCF in one embodiment of this invention acquires from HSS. It is an example (the 1) of S-CSCF information which HSS holds in one embodiment of the present invention. It is an example (the 1) of the list | wrist of S-CSCF containing the capability information which I-CSCF in one embodiment of this invention acquires from HSS. It is an example (the 2) of S-CSCF information which HSS holds in one embodiment of the present invention. It is an example (the 2) of the list | wrist of S-CSCF containing the capability information which I-CSCF in one embodiment of this invention acquires from HSS. It is an example of a table, such as a weight of S-CSCF which I-CSCF hold | maintains in one embodiment of this invention, a success rate. It is an example of the weight table of S-CSCF which I-CSCF holds in one embodiment of the present invention. It is an example of the record regarding the rejection from S-CSCF which I-CSCF hold | maintains in one embodiment of this invention. It is an example of the record regarding the rejection from S-CSCFa in one embodiment of this invention. It is the sequence in the 2nd Embodiment of this invention. It is a server redirection system sequence (until the Register reaches the pattern / alternative S-CSCF using capability information retention) in the third embodiment of the present invention. It is a server redirection method sequence using the LDF according to the third embodiment of the present invention (a method for designating a plurality of redirect destinations / until a Register reaches the alternative S-CSCF).

  Embodiments of the present invention will be described below with reference to the drawings.

  First, the outline of the present invention will be described.

  In the IMS architecture, the server selection function (I-CSCF) selects a server (S-CSCF) that accepts a registration request transmitted by a terminal.

  In the present invention, when the S-CSCF rejects the message, the I-CSCF selects an alternative S-CSCF, thereby distributing the load of the S-CSCF. Also, the load information collection function is not required when selecting an alternative S-CSCF, and it is possible to use S-CSCF capability information and the load status of the S-CSCF when selecting an alternative S-CSCF. is there.

  The processing of the present invention is roughly divided into two. The first is a method for creating and acquiring an S-CSCF list for the I-CSCF to select an alternative S-CSCF. The second is a method in which the I-CSCF selects an alternative S-CSCF from the list.

  Before describing these methods, first, an IMS (IP Multimedia Subsystem) architecture used in the present invention and a terminal registration method will be described.

  In the IMS architecture, as shown in FIG. 1, a user terminal (UE) 100, a session control server (P-CSCF200, I-CSCF300, S-CSCF400), a subscriber information database (HSS) 500, and the like exist. These components have the following functions.

-UE (User Equipment) 100:
A terminal used by a user. It registers its own information and sends a call request to the session control server (P-CSCF200, I-CSCF300, S-CSCF400). It also has a function of receiving incoming calls from other UEs from the session control server.

・ P-CSCF (Proxy-Call Session Control Function) 200:
This is the server that the UE 100 contacts first. In addition to receiving messages and transferring them to the I-CSCF300, it also has security functions such as IP-sec.

・ I-CSCF (Interrogating-Call Session Control Function) 300:
As shown in FIG. 6, the I-CSCF 300 includes a terminal / user information acquisition unit 301, a message transfer destination selection unit 302, and a message transfer unit 303. Upon receiving the REGISTER message from the P-CSCF 200, the terminal / user information acquisition unit 301 inquires the HSS 500 for capability information of the S-CSCF 400 and a list of S-CSCFs in order to select a registration destination S-CSCF 400. The message transfer destination selection unit 302 selects the S-CSCF 400 that matches the required ability from the information (S-CSCF list) of the S-CSCF 400 acquired by the terminal / user information acquisition unit 301. The message transfer unit 303 transfers the message from the P-CSCF 200 to an appropriate S-CSCF 400.

・ S-CSCF (Serving-Call Session Control Function) 400:
The S-CSCF 400 is a server that plays a central role as a SIP server, and all IMS messages pass through the S-CSCF 400. It also manages user information downloaded from the HSS 500. S-CSCF400 may have different capabilities depending on the type.

・ HSS (Home Subscriber Server) 500:
The HSS 500 is a subscriber information database, which includes basic information of subscribers (for example, the type of service subscribed, authentication user ID, public user ID (SIP URI, TEL URI, etc.), authentication vector, etc.) Is managed to which S-CSCF 400 is assigned. It also holds capability information of the S-CSCF 400 and provides it in response to an inquiry from the I-CSCF 300. Information managed by the HSS 500 is shown in FIG. The information of the HSS 500 shown in the figure includes an authentication ID, a public ID (SIP URI), a service type, an authentication vector, and S-CSCF allocation.

  Note that the UE 100, the I-CSCF 300, and the S-CSCF 400 include storage means such as a memory for holding received data, tables, calculation results, and the like.

  The operation in the above configuration will be described below.

[1] Terminal registration in IMS architecture:
In order to make a call between terminals, it is necessary to first register the terminal to the P-CSCF 200. Terminal registration is performed by a REGISTER message. The REGISTER message issued by the terminal 100 includes P-CSCF 200 information (for example, IP address and FQDN (Fully Qualified Domain Name)), user identification information (for example, SIP URI and TEL URI), and UE 100 information (IP address and authentication). USIM (Universal Subscriber Identity Module) IMSI (International Mobile Subscriber Identity) information, etc. This sequence is as shown in FIG.

  When the P-CSCF 200 receives the first REGISTER message from the UE 100 (step 11), the P-CSCF 200 transmits the REGISTER message to an arbitrary I-CSCF 300 (step 12).

  Upon receiving the REGISTER message, the I-CSCF 300 queries the HSS 500 for an S-CSCF list including capability information (an example of a list of servers including capability information is shown in FIG. 3) in order to select a registration destination S-CSCF 400. (Step 13). The I-CSCF 300 stores the S-CSCF list acquired from the HSS 500 in a memory (not shown), selects the S-CSCF 400 from the list based on predetermined essential conditions and capability information, and transmits a REGISTER message. (Step 15).

  In addition, there are things that are indispensable and those that are not (for example, it is conceivable that the presence or absence of charge management is an indispensable condition and the processing speed is not an indispensable condition). The S-CSCF 400 that does not satisfy the essential conditions in the server list is excluded, and then the S-CSCF 400 is selected with reference to the non-essential capability information. This selection is, for example, a level that matches the capability required of the UE 100 (for example, the necessity of charging management and the processing speed required for the S-CSCF 400) (for example, whether or not the processing capability exists in charging management or the like, or a certain threshold for the processing speed) Etc.).

  The S-CSCF 400 obtains information (authentication vector, etc.) necessary for authentication from the HSS 500 and indicates that the user has been selected by the I-CSCF 300, so that the relationship between the user information (SIP URI, etc.) and the S-CSCF (Steps 16 and 17). The S-CSCF 400 generates a challenge and notifies the UE 100 via the I-CSCF 300 and the P-CSCF 200 (steps 18 and 19).

  The UE 100 that has received this challenge generates an authentication key (response) using the challenge as an argument, and transmits a second REGISTER including the response again (step 21). Receiving this, the P-CSCF transmits a REGISTER message to 200 arbitrary I-CSCFs 300 (step 22). The I-CSCF 300 may be an I-CSCF different from the I-CSCF that received the first REGISTER.

  The I-CSCF 300 that has received the REGISTER message makes an inquiry to the HSS 500 to obtain information on the registration destination S-CSCF (steps 23 and 24). Based on this information, the I-CSCF 300 transmits a REGISTER message to the S-CSCF 400 (step 25).

  S-CSCF400 which received this collates the response transmitted from UE100 with the authentication vector acquired from HSS500, and if it matches, UE100 will complete registration as having been authenticated by S-CSCF400, and if it does not match The UE 100 is notified that the authentication has failed (steps 28, 29, 30).

[2] Selection of S-CSCF during terminal registration:
In this process, the I-CSCF 300 selects the S-CSCF 400 at the time of terminal registration in the above [1] in order to distribute the load of the S-CSCF 400.

In order to distribute the load of S-CSCF400,
-Creation and acquisition of S-CSCF list for I-CSCF300 to select S-CSCF;
-I-CSCF300 selects S-CSCF from the list;
The following two processes are performed. These processes will be described in the first embodiment, and further, a countermeasure method in the case where the S-CSCF selected by the I-CSCF refuses registration or the registration times out will be described in the second embodiment. .

[First Embodiment]
In the present embodiment, an S-CSCF list creation / acquisition method (A) by I-CSCF at the time of terminal registration and a method (B) in which the ICSCF selects an S-CSCF from the S-CSCF list will be described.

(A) How to create and obtain an S-CSCF list for I-CSCF to select S-CSCF:
This method is a method in which the I-CSCF 300 that has received the REGISTER message from the UE 100 and the P-CSCF 200 acquires a list of S-CSCFs including capability information from the HSS 500.

  In order to select the S-CSCF 400 and the alternative S-CSCF 400 by the I-CSCF 300, the I-CSCF 300 accesses the HSS 500 and acquires a list of S-CSCFs including capability information. At this time, in addition to capability information, for example, load information, maintenance information, failure information, deinstallation information, or the availability of S-CSCF can be included in the S-CSCF list. By using this information by I-CSCF300, a certain standard (for example, the load is above a certain level, maintenance is scheduled, the S-CSCF is scheduled to be removed, maintenance is underway, failure occurs) It is possible to prevent specific S-CSCFs from being selected.

  There are the following three methods for preventing a specific S-CSCF from being selected.

(A) Method of not reporting information on the state of the S-CSCF 400 from the S-CSCF 400 to the HSS 500:
This method is the same as that described in the terminal registration in the IMS architecture in [1] above. The S-CSCF 400 does not notify the HSS 500 of information related to the state of the S-CSCF 400. When the I-CSCF 300 receives the first REGISTER message from the UE 100, the I-CSCF 300 requests a list of S-CSCF including capability information from the HSS 500, and the HSS 500 includes a list of S-CSCF including capability information (FIG. The CSCF 300 responds with an example of an S-CSCF list including capability information acquired from the HSS 500 (procedure 1). The I-CSCF 300 that has received this selects the S-CSCF 400 (details will be described later in (B) How the I-CSCF selects an S-CSCF from the S-CSCF list). That is, the S-CSCF 400 that is inconvenient to be selected does not register its own information in the HSS 500, so that the S-CSCF is not included in the S-CSCF list.

(B) A method for notifying the availability of its own from the S-CSCF 400 to the HSS 500, or a method for setting whether or not the S-CSCF can be used by the operator:
In this method, the S-CSCF 400 uses its own status (for example, load information, maintenance schedule, failure information, planned to be removed, etc.) and is scheduled for maintenance within a certain standard (for example, the load is above a certain level). Whether or not it is possible to accept further registration of the UE 100 based on whether the failure has occurred, the reduction is scheduled within one week). Based on the determination result, the S-CSCF 400 notifies the HSS 500 of whether or not it can be used periodically (for example, every 10 minutes). The HSS 500 holds information on availability of each S-CSCF 400. Alternatively, an operator or the like can directly set whether or not the S-CSCF 400 can be used in the HSS 500.

  An example of the S-CSCF table managed by the HSS 500 is shown in FIG. As shown in FIG. 9, the HSS 500 stores the SIP URI, IP address, processing performance, charge management function, availability of use, etc. of the S-CSCF in a table in the database.

  When the I-CSCF 300 receives the first REGISTER message from the UE 100, the I-CSCF 300 requests the SSSCS list including capability information from the HSS 500, and the HSS 500 includes a list of S-CSCF 400 including capability information and availability (see FIG. 10). An example) is responded (procedure 1).

  Receiving this, the I-CSCF 300 stores the received S-CSCF list in an internal memory (not shown), and after removing the unavailable S-CSCF from the list, the S-CSCF Selection is made (details are described in (B) by the I-CSCF selecting the S-CSCF from the S-CSCF list).

(C) How to notify the SSS from the S-CSCF to HSS:
The S-CSCF 400 notifies the HSS 500 of its own status (for example, load information, maintenance schedule, failure information, reduction schedule, etc.) periodically (for example, every 10 minutes) and holds it. Alternatively, the operator or the like can directly set the status of the S-CSCF 400 in the HSS 500. An example of the S-CSCF table managed by the HSS 500 is shown in FIG. When the I-CSCF 300 receives the first REGISTER message from the UE 100, the I-CSCF 300 requests the list of S-CSCF including capability information from the HSS 500, and the HSS 500 lists the S-CSCF list including capability information and status (example in FIG. 12). Is displayed (step 1).

  Upon receiving this, the I-CSCF 300 stores the list of the S-CSCF in a memory (not shown) and includes the status of each S-CSCF 400 (for example, load information, maintenance schedule, failure information, reduction schedule, etc.). The I-CSCF300 is used with a certain standard (for example, the load is above a certain level, maintenance is scheduled within 24 hours, a failure has occurred, and reduction is scheduled within one week. Whether or not the S-CSCF 400 is to be used. After removing unused S-CSCFs from the list, the I-CSCF 300 selects S-CSCFs (details will be described later in (B) How I-CSCF Selects S-CSCFs from S-CSCF Lists). .

  When the HSS 500 notifies the I-CSCF 300 of the list of S-CSCFs including the capability information, the order in the list is sequentially rearranged (for example, every time the notification is sent to the I-CSCF, It is also possible to move the entry to the end).

(B) How I-CSCF selects S-CSCF from the list of S-CSCF:
In this embodiment, a list of S-CSCF 400 including capability information is obtained from HSS 500, temporarily stored in a memory (not shown), and in some cases, an I-S that excludes unused S-CSCF 400 entries from the list. The CSCF 300 relates to a method for selecting the S-CSCF 400 using this list.

  The following five methods can be considered as the selection method of the S-CSCF400.

(1) Select the first one:
Select the one at the top of the S-CSCF400 list.

  As described in (A) above, every time the HSS 500 notifies the I-CSCF 300 of the list of S-CSCFs including the capability information, the order in the list is rearranged (for example, for each notification to the I-CSCF 300). The S-CSCF 400 can be selected by round robin.

(2) Select at random:
The S-CSCF 400 is selected at random from the list of S-CSCF 400. When selecting the S-CSCF 400 at random, a method of assigning weights based on capability information, the rejection rate from the S-CSCF 400, or the number of rejections is also conceivable.

For example, when the processing capability of the S-CSCF 400 is s, the rejection rate is p, and an arbitrary constant is N, the weight function w (s, p) is defined as shown in Equation (1), and a certain S-CSCF ( A method of defining the probability q _i for selecting the number i) as in equation (2) is conceivable.

なお、この時Kは、I-CSCF３００が持つ能力情報を含むS-CSCFのリストに含まれるS-CSCF４００のうち、必須能力を満たすものの集合である。

At this time, K is a set of S-CSCFs 400 satisfying the essential capabilities among the S-CSCFs 400 included in the S-CSCF list including the capability information of the I-CSCF 300.

  The following can be considered as an example of a method for determining the weight. In this method, the initial value of the weight is set to a constant value (for example, 1), and the weight is changed when each S-CSCF rejects. There are the following two methods (a) and (b).

(A) A method of subtracting weights based on a rejection rate for each fixed period:
The I-CSCF 300 stores the weight w, the number of successful registrations s, the number of rejections f, and the rejection rate p (= f / (s + f)) in the memory (not shown) for the S-CSCF 400 that has transmitted REGISTER until the present time. Z). For the new S-CSCF, the weight is the initial value and the rejection rate is 0. An example of this is shown in FIG. When the I-CSCF sends a REGISTER to the S-CSCF, the I-CSCF records the number of registration successes and holds the rejection rate.

  The weight of each S-CSCF is updated based on this rejection rate at regular intervals (for example, 1 hour). For this update, for example, a gradient method can be used. In this case, for example, a weight is calculated as in the following Expression (3).

なお、ここで、iはS-CSCFの番号、pは前述の一定周期(例えば、１時間)毎に計測される拒否率、Δは定数である。

Here, i is the S-CSCF number, p is the rejection rate measured every predetermined period (for example, 1 hour), and Δ is a constant.

  Note that normalization of the weights of these subtracted S-CSCFs (such as setting the sum of weights to 1) may be performed at regular intervals. Further, the rejection rate p may be reset (that is, the registration success count s and the registration failure count f are reset to 0) at regular intervals.

b) A method of subtracting the weight each time the S-CSCF 400 rejects:
There is also a method of changing the weight when the S-CSCF 400 selected by the I-CSCF 300 rejects the registration.

  The I-CSCF 300 holds the weight w for the S-CSCF 400 that has transmitted REGISTER up to the present time. For the new S-CSCF, the weight is the initial value. An example of this is shown in FIG. If the registration fails when the I-CSCF 300 transmits REGISTER to the S-CSCF 400, the weight is subtracted by, for example, Expression (4). Here, Δ is a constant.

なお、一定周期毎に、これらの減算されたS-CSCF４００の重みの正規化(重みの合計を1にするなど)を行ってもよい。

Note that normalization of the weights of the subtracted S-CSCF 400 (such as setting the sum of the weights to 1) may be performed at regular intervals.

  When these algorithms are used, it is possible to send no more messages to the S-CSCF whose load has reached a certain level.

(3) Refer to the capability information of the S-CSCF and select in descending order of the matching ratio of the capability required by the UE:
According to the IMS standard rules (Non-Patent Document 1), the I-CSCF 300 selects the S-CSCF 400 that matches the S-CSCF capability required by the UE 100 when the terminal is registered. When selecting an alternative S-CSCF, by referring to the list of S-CSC 400F that includes the capability information acquired by the I-CSCF 300 from the HSS 500, an appropriate S-CSCF 400b next to the S-CSCF 400a selected first is selected. select. This selection is similar to that described in [1] above, for example, to the extent that it matches the capability required by the UE 100 (for example, the necessity of charging management, the processing speed required for the S-CSCF 400, etc.) This is performed based on the presence or absence of capability or a certain threshold of processing speed).

(4) Refer to the past S-CSCF rejection ratio and select an S-CSCF with the lowest rejection ratio as much as possible:
The I-CSCF 300 can record the percentage of registration rejections received from the S-CSCF 400 selected in the past. For example, the number of selection attempts and the number of rejections are recorded in a memory (not shown) for each target S-CSCF 400, and the rejection rate (p = f / (s + f)) (where s = number of successful registrations, f = number of rejections)). When the number of trials is a certain number (for example, 10 times) or less, the rejection rate is specifically set to 0. An example of this is shown in FIG. In addition, the time and success / failure of each trial is recorded in the memory (not shown) of the I-CSCF 300 (an example is shown in FIG. 16), and a certain time or a certain number of times (eg, 1 hour or 100 times) The data that has passed is deleted, and when it is deleted, the rejection rate is recalculated.

  Based on this information, for example, a method may be considered in which an S-CSCF having a rejection rate above a certain level is not selected for a certain period of time. For example, when the time when the rejection rate exceeds a certain level is recorded for each S-CSCF 400, and the difference from the time when the S-CSCF is selected is within a certain time (for example, 30 minutes, 48 hours, etc.) Has a method to remove the S-CSCF from the selection.

  As a result, for example, when the S-CSCF 400 is refusing on the basis of the load status, it prevents the message from being continuously sent to the S-CSCF where the load is high and the message cannot be accepted. Can protect from down.

(5) Combination of the above:
By combining the methods (1) to (4) above, for example, it is a principle to select an S-CSCF that matches the capability required by the UE 100, for example. However, avoid selecting an S-CSCF that seems to be a heavy load. The method of, etc. can be considered.

[Second Embodiment]
In the present embodiment, when a transmission of a REGISTER message is transmitted from the I-CSCF 300 to the S-CSCF 400 in the first embodiment described above, the response when the S-CSCF 400 rejects the registration or the registration times out is described. To do.

  FIG. 17 shows a sequence in the second embodiment of the present invention.

  As shown in FIG. 17 (a), when the I-CSCF 300 transmits a REGISTER message to the S-CSCF 400, the S-CSCF 400 is initially set by an operator or the like according to a certain standard (for example, when the load is a certain level or more). (It can be specified by setting or resetting.) This can be rejected. If the message is not rejected, the S-CSCF 400 acquires an authentication vector from the HSS 500 and generates a challenge (this is the same as in the previous embodiment).

  On the other hand, as shown in FIG. 17B, when the message is rejected or when transmission of the REGISTER message to the S-CSCF 400a times out, the I-CSCF 300 inquires the HSS 500 about the S-CSCF information. A different S-CSCF 400b is selected as an alternative S-CSCF from the list acquired at this time, and a REGISTER message is transmitted again (procedure 2). Note that the availability or status of the S-CSCF 400 can also be reflected in the selection of the alternative S-CSCF at this time by performing the selection method described in (B) in the first embodiment. . The S-CSCF 400b that has received the REGISTER again from the I-CSCF 300 acquires an authentication vector from the HSS 500 and generates a challenge. If the S-CSCF 400b selected for the second time is also rejected, the above procedure 1 or procedure 2 is repeated. The same is true for the third and later rejections. In this way, the selection of the alternative S-CSCF is repeated, but the S-CSCF selection process is stopped at a certain point (for example, when rejected from a total of 10 S-CSCFs or timed out) due to operator settings, etc. It is also possible to return an error.

  In the above processing, although related to the first embodiment, when the REGISTER message is rejected, the number of rejections is recorded in a memory (not shown).

[Third Embodiment]
In the present embodiment, an example will be described in which capability information at the time of selecting an alternative S-CSCF in the prior art (A) is used.

  It is possible to select an alternative S-CSCF that reflects capability information by improving the prior art (a). The functional diagram is the same as that shown in FIG.

(1) How LDF collects capability information as well as S-CSCF load information:
The sequence is shown in FIG. The LDF 600600 receives periodic notification of not only the load information but also the capability information from the S-CSCF 400, and the LDF accumulates the load information and capability information of each S-CSCF 400, and notifies and holds the plurality of S-CSCFs. Each S-CSCF shares not only itself but also load information and capability information of other S-CSCFs.

  When the UE 100 registers with the S-CSCF 400, the P-CSCF 300 and the I-CSCF 300 accept a registration request from the UE 100 (Steps 301 and 302). The I-CSCF 300 requests the HSS 500 for a list of S-CSCF 400 including capability information (step 303) and acquires it (step 304). The I-CSCF 300 selects an S-CSCF 400 appropriate for the UE 100 using this capability information, and transmits a registration request (step 305). When the S-CSCF 400a that has received the registration request is overloaded, the S-CSCF 400a redirects to the low-load S-CSCF 400b based on the shared load information and capability information. (Step 306). In response, the I-CSCF 300 transmits a registration request again to the alternative S-CSCF 400b (step 307).

(2) Method for notifying the I-CSCF of multiple alternative S-CSCFs when the S-CSCF specifies a redirect destination:
The sequence is shown in FIG. The LDF 600 receives a periodic notification of load information from the S-CSCF 400, and the LDF 600 accumulates the load information of each S-CSCF 400 in an internal storage means (for example, a memory), and notifies and holds a plurality of S-CSCFs 400. Each S-CSCF 400 shares not only itself but also load information of other S-CSCFs.

  When the UE 100 registers with the S-CSCF 400, the P-CSCF 300 and the I-CSCF 300 accept a registration request from the UE 100 (Steps 401 and 402). The I-CSCF 300 requests the HSS 500 for an S-CSCF list including capability information (step 403) and acquires it (step 404). The I-CSCF 300 selects the S-CSCF 400 (400a) appropriate for the UE 100 using this capability information, and transmits a registration request (step 405). When the S-CSCF 400a that has received the registration request is overloaded, the S-CSCF 400a notifies the I-CSCF 300 of a plurality of low-load S-CSCFs based on the shared load information. (Step 406). In response, the I-CSCF 300 determines which of the plurality of S-CSCFs is to be used as an alternative S-CSCF based on the capability information, determines an appropriate S-CSCF 400b as an alternative S-CSCF, and The alternative S-CSCF transmits a registration request again (step 407).

  Note that the operation of the I-CSCF 300 can be constructed as a program and installed in a computer used as an I-CSCF (server selection device) or distributed via a network.

  In addition, the constructed program can be stored in a portable storage medium such as a hard disk, a flexible disk, or a CD-ROM, and installed in a computer or distributed via a network.

  The present invention is not limited to the above-described embodiment, and various modifications and applications can be made within the scope of the claims.

100 clients (UE)
200 Proxy server (P-CSCF)
300 Server selection function (I-CSCF)
301 Terminal / User Information Acquisition Unit 302 Message Transfer Destination Selection Unit 303 Message Transfer Unit 400 Server (S-CSCF)
500 Server information DB (HSS)
600 Load information collection function (LDF)

Claims (6)

A server load balancing method in a system for selecting a server for registering a client in IMS (Internet protocol Multimedia Subsystem) architecture,
at least,
The client terminal used by the user,
A storage device for holding a server information list regarding the status of the session control server, including client user information and session control server capability information;
A session control server for call control;
A server selection device that accepts a registration request from a client and selects a session control server with a low load;
In a system having
The server selection device is
When a registration request is acquired from the terminal of the client, the server selection step of acquiring the server information list by accessing the storage device, storing it in a server information list storage means, and selecting a session control server for registering the client When,
A registration request step for transmitting the registration request to the session control server selected in the server selection step;
When registration is rejected from the session control server or when a timeout occurs, another server is selected from the server information list storage means, and the registration request is sent to the other session control server. An alternative server selection step to send;
And
In the server selection step,
Session control for deleting a session control server that does not satisfy the essential conditions from the server information list stored in the server information list storage means, and transmitting the registration request according to the capability information and load status of each session control server Select the server
In the alternative server selection step,
If registration is rejected from the session control server, record the number of rejections in the server information list storage means, if registration is successful, record the number of successful registrations,
Weighting based on the session control server capability information stored in the server information list storage means, the session control server rejection rate or the rejection count obtained from the registration success count and the rejection count, The session control server based on
Server load balancing wherein a call. In the server selection step or the alternative server selection step,
The session controlling server refers to the capability information, server load balancing method of claim 1 Symbol placement selects the session control server descending order of proportion that matches the ability of the client asks the server information list storage unit. A server load balancing system for selecting a server for registering a client in an IMS (Internet protocol Multimedia Subsystem) architecture,
at least,
The client terminal used by the user,
A storage device for holding a server information list regarding the status of the session control server, including client user information and session control server capability information;
A session control server for call control;
A server selection device that accepts a registration request from a client and selects a session control server with a low load;
Have
The server selection device includes:
When a registration request is acquired from the client terminal, the server information list is acquired by accessing the storage device, stored in a server information list storage means, and a server selection means for selecting a session control server for registering the client When,
Registration request means for transmitting the registration request to the session control server selected by the server selection means;
When registration is rejected from the session control server or when a timeout occurs, another server is selected from the server information list storage means, and the registration request is sent to the other session control server. An alternative server selection means for transmitting;
Have
The server selection means includes
A session control server that deletes a session control server that does not satisfy essential conditions from the server information list stored in the server information list storage means, and transmits the registration request according to the capability information and load status of each session control server Including means for selecting
The server selection means or the alternative server selection means
If registration is rejected from the session control server, the number of rejections is recorded in the server information list storage means, and if the registration is successful, means for recording the number of successful registrations;
Weighting based on the session control server capability information stored in the server information list storage means, the session control server rejection rate or the rejection count obtained from the registration success count and the rejection count, Means for selecting a session control server based on the server load distribution system. The server selection means or the alternative server selection means
4. The server load distribution system according to claim 3 , further comprising means for referring to the capability information of the session control server in the server information list storage means and selecting the session control servers in descending order of matching with the capability required by the client. at least,
The client terminal used by the user,
A storage device for holding a server information list regarding the status of the session control server, including client user information and session control server capability information;
A session control server for call control;
A server selection device that accepts a registration request from a client and selects a session control server with a low load;
A server selection device in a server load balancing system for selecting a server to register a client in an IMS (Internet protocol Multimedia Subsystem) architecture,
When a registration request is acquired from the client terminal, the server information list is acquired by accessing the storage device, stored in a server information list storage means, and a server selection means for selecting a session control server for registering the client When,
Registration request means for transmitting the registration request to the session control server selected by the server selection means;
When registration is rejected from the session control server or when a timeout occurs, another server is selected from the server information list storage means, and the registration request is sent to the other session control server. An alternative server selection means for transmitting,
The server selection means includes
Session control for deleting a session control server that does not satisfy the essential conditions from the server information list stored in the server information list storage means, and transmitting the registration request according to the capability information and load status of each session control server A means of selecting a server,
Or
Means for referring to the capability information of the session control server in the server information list storage means, and selecting the session control server in descending order of the rate matching the capability required by the client;
Or
When registration is rejected from the session control server, the number of rejections is recorded in the server information list storage means. When registration is successful, the number of successful registrations is recorded and stored in the server information list storage means. capability information of the session control server is, rejection rate of the session control server obtained from the registration number of successful and the refusal number or based on the refusal number weighted, selects a session control server based on the heavy wear Means ,
Including at least one of
The alternative server selection means includes
When registration is rejected from the session control server, the number of rejections is recorded in the server information list storage means. When registration is successful, the number of successful registrations is recorded and stored in the server information list storage means. capability information of the session control server is, rejection rate of the session control server obtained from the registration number of successful and the refusal number or based on the refusal number weighted, selects a session control server based on the heavy wear means,
Or
Referring to capability information of the session control server in the server information list storage means, and including at least one of means for selecting the session control server in descending order of the rate matching the capability required by the client,
The server selection apparatus characterized by the above-mentioned.   A server load distribution program for causing a computer to function as each means constituting the server selection device according to claim 5.

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