Patent Publication Number: US-9407668-B2

Title: Protection against unsolicited communication for internet protocol multimedia subsystem

Description:
TECHNICAL FIELD 
     The present invention relates to the protection against unsolicited communication for Internet protocol multimedia subsystems. 
     The present application claims priority based on Japanese Patent Application No. 2008-260088, the content of which is incorporated herein by reference. 
     BACKGROUND ART 
     The recent stream of telecommunication has led to IP (Internet Protocol) standardization on audio communication systems representative of telephone networks. The 3GPP (3rd Generation Partnership Project), which is the working group on the standardization of mobile communications, drafted the specification for the standardization of the IP multimedia subsystem (IMS) serving as the platform for providing multimedia services such as audio services on the IP network. Recently, assessments have been carried out with respect to the fixed-type IP standardization on the next generation network (NGN). 
     Electronic mailing services have suffered from social problems such as Spam and unsolicited (or junk) mails, which are unwanted mails unilaterally sent to recipients by senders. Unsolicited communications occur due to various factors derived from the popularization of the Internet, such as significant decreases of communication costs and advanced capabilities of network access terminals (such as personal computers purchasable by common users) transmitting numerous electronic mails to unspecified persons or sites. 
     The above problem (already occurring in electronic mailing services) seems to occur in the IMS due to its popularization. The 3GPP specification has initiated the protection against unsolicited communication for EMS (simply referred to as “PUCI”) to protect users from Spam over the IP telephony (SPIT). In this connection, Patent Document 1 discloses a mobile network system having IMS entities. 
     Patent Document 1: Japanese Patent Application Publication No. 2007-527633 
     The 3GPP just started the assessment on the PUCI for the IMS. Subscriber originating calls are each subjected to testing by way of PUCI applications, which in turn evaluate calls with unsolicited rating scores. Unsolicited calls are rejected (or declined) but calls which are not regarded as unsolicited calls are forwarded to the user equipment. Herein, the problem is how the IMS involves the PUCI application for checking scores. 
     DISCLOSURE OF INVENTION 
     To solve the above problem, two alternative solutions are demonstrated below.
     (1) The serving call session control function (S-CSCF) is enhanced to provide a dispatching functionality.   (2) The PUCI application is enhanced to enable the distributed processing for making next-hop routing decisions, in which the PUCI application needs to autonomously determine whether to perform a PUCI test/stage on a next call.   

     The conventional IMS specification adopting the initial filter criteria (iFC) accepts only the static routing on application servers and is limited to the dynamic application server (AS) assignment based on the digital subscriber network (DSN). This requires the IMS to be enhanced in providing an adequate flexibility for handling the PUCI. 
     The present invention seeks to solve the above problem, wherein the object thereof is to expand functions of the IMS by way of enhancing the S-CSCF or implementing a new routing logic to an application server. 
     Specifically, a protection against an unsolicited communication for an IMS (PUCI) system includes a call session control function (CSCF), and a plurality of PUCI application servers. The PUCI application servers make an evaluation as to whether a communication received from the user equipment is an unsolicited communication; the CSCF makes a decision on routing toward the PUCI application servers based on the evaluation; then, the PUCI application servers execute the routing based on the decision. 
     According to Solution 1, the PUCI system implements the processing comprising: forwarding an INVITE from the user equipment to the CSCF; executing a PUCI service in the CSCF; forwarding the INVITE in light of an initial filter criteria (iFC) from the CSCF to a first PUCI application server; executing a PUCI Test 1 in the first PUCI application server, thus producing the result indicating a probability of occurrence of an unsolicited call; sending back the INVITE including the result of the PUCI Test 1 from the first PUCI application server to the CSCF; evaluating the result so as to forward the INVITE to a second PUCI application server suitable for further testing; executing a PUCI Test 2 in the second PUCI application server, thus producing the result indicating a further probability of the occurrence of the unsolicited call; sending back the INVITE including the result of the PUCI Test 2 from the second PUCI application server to the CSCF; and evaluating both the results so as to reject the unsolicited call. 
     According to Solution 2, the PUCI system implements the processing comprising: forwarding an INVITE from the user equipment to the CSCF; executing a PUCI service in the CSCF; forwarding the INVITE in light of an initial filter criteria (iFC) from the CSCF to a first PUCI application server; executing a PUCI Test 1 in the first PUCI application server, thus producing the result indicating a probability of occurrence of an unsolicited call; evaluating the result so as to determine a second PUCI application server suitable for further testing; sending back the INVITE including the result destined to the second PUCI application server from the first PUCI application server to the CSCF; forwarding the INVITE to the second PUCI application server from the CSCF to the second PUCI application server; executing a PUCI Test 2 in the second PUCI application server, thus producing the result indicating a further probability of the occurrence of the unsolicited call; evaluating the result so as to route the unsolicited call to a terminating party or to send back the INVITE including the result indicating no probability of the occurrence of the unsolicited call to the CSCF. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a block diagram showing the constitution for the protection against unsolicited communication for an Internet protocol multimedia subsystem, i.e. a PUCI system. 
         FIG. 2  is a block diagram showing the constitution of a PUCI system according to Embodiment 1. 
         FIG. 3  is a sequential flow chart used for explaining the processing executed between user equipment, a proxy call session control function (P-CSCF), a serving call session control function (S-CSCF), and application servers (PUCI AS 1 -AS 2 ) included in the PUCI system of  FIG. 2 . 
         FIG. 4  is a block diagram showing the constitution of a PUCI system according to Embodiment 2. 
         FIG. 5  is a sequential flow chart used for explaining the processing executed between the user equipment, P-CSCF, S-CSCF, and PUCI AS 1 -AS 2  included in the PUCI system of  FIG. 4 . 
     
    
    
     BEST MODE FOR CARRYING OUT THE INVENTION 
     The present invention refers to dynamic routing decisions on unsolicited calls using a plurality of PUCI application servers by way of two methods, i.e. a first method for executing dynamic routing in the serving call session control function (S-CSCF) or a second method for executing dynamic routing in the PUCI application server. Herein, dynamic routing decisions are made in either the S-CSCF or the PUCI application server based on results of PUCI testing and scores of testing. 
     Specifically, the present invention demonstrates the following technical features.
     (1) The S-CSCF is enhanced to perform dynamic routing toward PUCI application servers based on the special PUCI information added to signaling messages (e.g. IMS/SIP headers, where SIP stands for Signal Initiated Protocol) or by way of out-of-band signaling between the S-CSCF and the PUCI application server.   (2) The PUCI application server is designed to have a dynamic call routing capability based on the special PUCI information included in the signaling messages (e.g. IMS/SIP headers).   

       FIG. 1  is a block diagram showing the constitution of a PUCI system, i.e. a system for the protection against unsolicited communication for the IMS, which is constituted of user equipment (UE A)  100  for originating calls, a proxy call session control function (P-CSCF)  200  for transferring calls originated by the user equipment  100  to destinations, a serving call session control function (S-CSCF)  300  requesting application servers to make decisions as to whether or not transferred calls are regarded as unsolicited calls, and a plurality of application servers (AS 1  to AS 4 )  401  to  404  for making decisions on unsolicited calls. 
     The 3GPP is the project regarding the third generation cellular phone system for preparing specifications on an extended network implementing wideband code division multiple access (W-CDMA) and a global system for mobile communications (GMS), and it recently started studying the PUCI system which is implemented by use of one PUCI application or by use of plural PUCI applications. Herein, the PUCI application tests a session regarding each subscriber call so as to check whether or not each subscriber call is regarded as a potentially unsolicited call. There are various methods and standards enabling PUCI applications to classify sessions into potentially unsolicited calls by way of various stages, wherein PUCI applications evaluate calls with unsolicited rating scores, which are sequentially accumulated. In this connection, the PUCI application is capable of sending the session signaling including the detailed information of the PUCI testing to the next PUCI application or the S-CSCF  300  (i.e. the IMS for designating the next PUCI application). 
     Calls which pass through various stages of the PUCI testing are finally regarded as solicited calls (which are not unsolicited calls) and then transferred to the user equipment (UE), while other calls are rejected. The PUCI application or the IMS handles a rejected session by way of three procedures, i.e. (i) to silently discard the rejected session, (ii) to gracefully terminate the rejected session by transmitting an ERROR or BYE message, and (iii) to present an explicit indication including a reason for rejection to a source entity. 
     Specific ideas are presented with respect to the following information elements (which are transmitted to a source entity, e.g. the user equipment  100  sending unsolicited calls) included in a REJECT message, and a method how to use them.
     (1) The name of the PUCI application, which is used to presume the result and the type of testing to be carried out.   (2) The testing result of the PUCI application, which is produced by way of specific testing.   (3) The signature of the PUCI application, which is used to validate the testing and to access the testing history.   (4) The cumulative PUCI score and a list of PUCI applications.   (5) Indication whether or not each session passes through the PUCI testing, which is used to prevent the SIP terminal adaptation from easily occurring.   (6) The signature of a legal entity which carries out the testing, which is used to validate the testing.   

     Since the user equipment (UE) is designed to finally terminate calls when the operator has no legal right to block calls on behalf of the end-user, the above information is added to a REJECT message by way of a PUCI application/function included in the UE which may finally block calls or by way of the PUCI application server or the IMS which is involved in the processing of a SIP BYE message or an ERROR message. 
     The 3GPP suffers from a problem in which when the IMS is designed to support several potentially independent PUCI application servers, the IMS needs to achieve the dynamic PVCI routing functionality, or each PUCI application server needs to autonomously route each session to the next PUCI application. 
     In addition, the present IMS specification may demonstrate a routing logic involving several application servers based on the initial filter criteria (iFC); however, this solution merely achieves static routing toward application servers based on the simple filter criteria. 
     Besides, the present IMS specification may ensure the dynamic application server assignment based on the DSN name; however, this solution is merely beneficial for the load balancing purpose. 
     In order to chain several PUCI application servers in a dynamic way based on the PUCE specification, the present invention provides the following solutions.
     (1) The S-CSCF of the IMS is enhanced to secure dynamic routing toward the PUCI application servers based on the special PUCI information added to signaling messages (e.g. IMS/SIP headers) or by way of out-of-band signaling between the S-CSCF and the PUCI application server.   (2) The PUCI application server is designed to have a dynamic call routing capability based on the special PUCI information included in the IMS/SIP signaling.
 
1. Embodiment 1 (or Solution 1 Implementing the Enhancement of IMS/S-CSCF)
   

       FIG. 2  is a block diagram showing the constitution of a PUCI system according to Embodiment 1, which includes the user equipment (UE A)  100  for originating calls, the proxy call session control function (P-CSCF)  200  for transferring calls originated by the user equipment  100  to destinations, the serving call session control function (S-CSCF)  200  requesting application servers to make decisions as to whether or not transferred calls are regarded as unsolicited calls, and a plurality of application servers (PUCI AS 1  to PUCI AS 4 )  501  to  504  for making decisions on unsolicited calls by way of various stages. The PUCI system of  FIG. 2  further includes a call session control function (CSCF)  600  for transferring calls to destinations, and user equipment (UE B)  700  serving as one destination. 
     Solution 1 implements a new PUCI-aware routing logic to the IMS/S-CSCF, which evaluates previous PUCI testing results included in either session signaling headers or out-of-band IMS service control (ISC), thus making a decision as to which PUCI application is to operate next or whether to reject sessions. 
     Solution 1 refers to the following information elements included in IMS/SIP signaling headers or out-of-band ISC (which should be used for further processing based on a routing logic).
     (1) The name of the PUCI application (which is used to presume the testing result).   (2) The indication as to whether or not each session passes through the PUCI testing.   (3) The detailed result of the PUCI application testing.   (4) The signature of the PUCI application, which is used to validate the testing to be carried out.   (5) The cumulative PUCI score and a list of PUCI applications.   

     In addition, Solution 1 refers to the following ideas on the routing logic (or the routing logic module).
     (1) The routing logic decides based on the cumulative PUCI score.   (2) The routing logic decides based on a weighted cumulative PUCI score, wherein the operator can configure different weights on the PUCI applications.   (3) The weights are determined based on the PUCI applications and/or the legal entity carrying out the testing.   (4) The routing logic decides based on the detailed result of the last PUCI testing.   (5) The routing logic decides by way of the analysis on all detailed results of previous PUCI testing.   (6) The routing logic module decides based on a program which is flexibly/dynamically extended/replaced (by way of upgrading the fly).   (7) The routing logic module decides based on a pattern matching algorithm.   (8) The routing logic utilizes a self-learning strategy, wherein upon the installation of a new   

     PUCI application, the routing logic learns how to interpret the results based on the explicit user feedback, the results of other PUCI applications and/or call patterns (which are used to presume whether or not calls are solicited), and the detailed PUCI application outputs.
     (9) The routing logic evaluates whether or not the testing is already carried out to avoid double triggering by the same application server.   

     The new PUCI routing logic should be invoked prior to the execution of the standard initial filter criteria, since the PUCI feature likely makes a decision to reject sessions so that the processing of various application servers will be wasted. 
       FIG. 3  is a sequential flow chart used for explaining the processing executed between the user equipment  100 , the P-CSCF  200 , the S-CSCF  300 , and the application servers (PUCI AS 1 -AS 2 )  501 ,  502  included in the PUCI system of  FIG. 2 . 
     Step S 101 : The A-party user equipment (UE A)  100  sends an INVITE for the B-party user equipment (UE B)  700  to the P-CSCS  200 . 
     Step S 102 : The P-CSCF  200  determines the S-CSCF  300  so as to forward the INVITE thereto. 
     Step S 103 : The S-CSCF  300  triggers the iFC (initial filter criteria) so as to execute the PUCE service. 
     Step S 104 : The S-CSCF  300  forwards the INVITE to the application server (PUCI AS 1 )  501  in light of the iFC. 
     Step S 105 : The application server  501  executes a PUCI Test 1 so as to produce a score rating the probability of the occurrence of an unsolicited call. 
     Step S 106 : The application server  501  incorporates the result of the PUCI Test 1 into a PUCI header of the INVITE, which is then sent back to the S-CSCF  300 . 
     Step S 107 : The S-CSCF  300  evaluates the result of the PUCI Test 1, wherein when the score of the PUCI Test 1 indicates the probability of the unsolicited call, the S-CSCF  300  a certain application server suitable for the further testing. When the S-CSCF  300  receives the result of the PUCI Test 1 indicating the probability of a solicited call (which is not a unsolicited call), the S-CSCF  300  performs the normal call processing so that not further testing is performed. When the S-CSCF  300  detects an unsolicited call at a high probability, the S-CSCF  300  immediately rejects such an unsolicited call. 
     Step S 108 : When the S-CSCF  300  detects the need of the further testing, the S-CSCF  300  selects a certain application server suitable for the further testing, that is, it forwards the INVITE to the application server (PUCI AS 2 )  502 . 
     Step S 109 : The application server  502  performs a PUCI Test 2 so as to make a determination on the unsolicited call. 
     Step S 110 : The application server  502  sends the result of the PUCI Test 2 to the S-CSCF  300 . 
     Step S 111 : The S-CSCF  300  evaluates both the result of the PUCI Test 1 and the result of the PUCI Test 2 so as to determine whether to deliver the call, whether to perform further testing, or whether to reject the call. 
     2. Embodiment 2 (or Solution 2 Implementing the Enhancement of the IMS/S-CSCF) 
       FIG. 4  is a block diagram showing the constitution of a PUCI system according to Embodiment 2, which includes the user equipment (UE A)  100 , the proxy call session control function (P-CSCF)  200 , the serving call session control function (S-CSCF)  300 , the application servers (PUCI AS 1  to PUCI AS 4 ), the call session control function (CSCF)  600 , and the user equipment (UE B)  700 . 
     Solution 2 implements a dynamic call routing capability as a part of each application server, which allows each application server to make an autonomous decision on the next PUCI application to be performed. A routing decision will be made based on the result of the PUCI application just performed as well as previous results of other PUCI applications previously performed. Previous results are provided to each application server in an in-band manner as a part of IMS/SIP signaling (i.e. PUCI specific header information). 
     In the above, the application server needs to act as a back-to-back user agent and to thereby change a request URI to the next desired application server for further testing. Herein, the application server includes the result of testing already executed in a special header record, so that the succeeding application server recognizes the testing already executed so as to take its information into consideration when another testing is required. 
       FIG. 5  is a sequential flow chart used for explaining the processing executed between the user equipment (UE A)  100 , the P-CSCF  200 , the S-CSCF  300 , the application servers (PUCI AS 1 -AS 2 )  501 ,  502  included in the PUCI system of  FIG. 4 . 
     Step S 201 : The A-party user equipment  100  sends an INVITE for the B-party user equipment  700  to the P-CSCF  200 . 
     Step S 202 : The.P-CSCF  200  determines the S-CSCF  300  so as to forward the INVITE thereto. 
     Step S 203 : The S-CSCF  300  triggers the initial filter criteria (iFC) so as to execute the PUCI service. 
     Step S 204 : The S-CSCF  300  forwards the INVITE to the application server (PUCI. ASO  501  in light of the iFC. 
     Step S 205 : The application server  501  executes a PUCI Test 1 so as to produce a score rating the probability of the occurrence of an unsolicited call. 
     Step S 206 : The application server  501  evaluates the result of the PUCI Test 1, wherein when the result indicates the probability of the unsolicited call, the application server  501  determines a certain PUCI application server suitable for further testing. When the application server  501  receives the result indicating the probability of a solicited call (which is not an unsolicited call), it performs the normal call processing so that no further testing is performed. When the application server  501  detects an unsolicited call, it directly rejects such an unsolicited call. 
     Step S 207 : The application server  501  incorporates the result of the PUCI Test 1 (as well as its test information) in a PUCI header of the INVITE, which is then sent back to the S-CSCF  300  as the INVITE destined to the application server (PUCI AS 2 )  502 . 
     Step S 208 : The S-CSCF  300  sends the INVITE including the result and test information of the PUCI Test 1 to the application server (PUCI AS 2 )  502 . 
     Step S 209 : The application server  502  performs a PUCI Test 2 so as to make a further determination on the unsolicited call. 
     Step S 210 : The application server  502  evaluates both the result of the PUCI Test 1 and the result of the PUCI Test 2 so as to determine whether to deliver the call, whether to perform further testing, or whether to reject the call. 
     Step S 211 : In the case of the further testing, the application server  502  sends the INVITE including the result of the PUCI Test 2 to the S-CSCF  300 . When the application server  502  detects an unsolicited call, it is unnecessary to deliver such an unsolicited call, which is thus routed to the terminating party. 
     As described above, the present embodiment is exemplarily involved in the following steps.
     (1) The EMS has a dynamic routing capability to invoke a desired order of PUCI application servers.   (2) The IMS (S-CSCF) is enhanced to ensure dynamic routing toward PUCE application servers based on the special PUCI information added to signaling messages (e.g. IMS/SIP headers) or by way of out-of-band signaling bet Ween the IMS (S-CSCF) and the PUCI application servers.   (3) The PUCI application server has a dynamic call routing capability based on the special information included in IMS/SIP signaling.   

     Lastly, the present invention is not necessarily limited to Embodiments 1 and 2, which can be further modified within the scope of the invention as defined by the appended claims.