Abstract:
A method assists the registration of subscription characteristics in a communications system, wherein a private user identity characteristic can be paired with a public user identity characteristic and more than one private user identity may be associated with a subscription. The method includes transmitting, from a subscription information store entity of the system to a service provision entity of the system, a first message containing data specifying characteristics of a pairing of a first private user identity and a public user identity. The message also includes an indication of any further private user identities other than the first private user identity that are associated with the same subscription as the first private user identity.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     1. Field of the Invention  
         [0002]     This invention relates to the registration of user identities in a communications system.  
         [0003]     2. Description of the Related Art  
         [0004]      FIG. 1  shows part of the architecture of the 3GPP system, including the IP Multimedia Subsystem (IMS)  1 . The IMS includes a serving call session control function (S-CSCF)  2  which can communicate with a home subscriber server (HSS)  3  over a Cx-type interface. The system also includes one or more connection entities  4  such as packet switched domains or P-CSCFs by means of which the IMS  1  can communicate with user entities  5  such as mobile phones. The interface  6  between the S-CSCF  2  and the HSS  3  is a Cx-type interface, whose characteristics are tightly specified.  
         [0005]     The general functionality of the units shown in  FIG. 1  in a current 3G system is well-known. In particular, the S-CSCF provides services to the user entities and the HSS stores information on subscriptions which can be accessed by the S-CSCF and stored by it in a local database  7  for assisting the provision of services to users under that subscription.  
         [0006]     The current specification for 3GPP Rel-6 TS 23.228 (version 6.7.0, chapter 4.3.3.4 FIG. 4.6) defines the IMS subscription, which may consist of multiple private user identities. The private user identities may be paired with dedicated or shared public user identities.  
         [0007]     Currently the public user identity—private user identity pair is registered explicitly and it is assumed that the S-CSCF will find out about the pairing of a subscription&#39;s private user identities with the help of shared public user identity/identities when such are registered. In some situations this can work satisfactorily. However, the private user identities may have also dedicated public user identities, which may be registered independently of the shared public user identities. It has been identified that when this happens under the current design the S-CSCF has no means of finding out that parings of a registered public user identity with a private user identity belong to the same IMS subscription.  
         [0008]     There is therefore a need for a means of enabling the S-CSCF to find out about such pairings.  
         [0009]     WO 2004/000089 (US 2004/0196796) addresses problems associated with an HSS linking multiple user identities to the same subscriber. Such identities must be registered at the same S-CSCF and accordingly the HSS does not give server capabilities for the second and further registrations, but instead gives the name of the already used S-CSCF.  
       SUMMARY OF THE INVENTION  
       [0010]     According to one aspect of the present invention there is provided a method for assisting the registration of subscription characteristics in a communications system in which a private user identity characteristic can be paired with a public user identity characteristic and more than one private user identity may be associated with a subscription; the method comprising transmitting from a subscription information store entity of the system to a service provision entity of the system a first message containing data specifying characteristics of a pairing of a first private user identity and a public user identity, the message also including an indication of any further private user identities other than the first private user identity that are associated with the same subscription as the first private user identity.  
         [0011]     Further aspects and preferred features of the invention are set out in the accompanying claims.  
         [0012]     The present invention will now be described by way of example with reference to the accompanying drawing. 
     
    
     BRIEF DESCRIPTION OF THE DRAWING  
       [0013]      FIG. 1  shows a communications system. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0014]     In summary, this example of the present invention involves the introduction of a new attribute to the Cx interface. This attribute has features that allow it to support IMS subscriptions with multiple private user identities.  
         [0015]     As will be explained in more detail below, in this example of the invention a new attribute is added to the Cx interface. This attribute is referred to herein as an Associated-Identities attribute. The attribute is capable of carrying sufficient information to inform as S-CSCF of private identities of the IMS subscription to the S-CSCF during the registration of a private user identity—public identity pair and when a new private user identity is added into the subscription.  
         [0016]     When a user registers a private user identity—public user identity pair in the IMS, the S-CSCF retrieves the authentication data and user data related to the identity pair from the HSS via the Cx interface. The commands used for this is are Multimedia-Auth-Request (MAR) and Server-Assignment-Request (SAR). The HSS returns the authentication data in the Multimedia-Auth-Answer (MAA) and the user data in the Server-Assignment-Answer (SAA) message.  
         [0017]     If the private identity—public identity pair belongs to a IMS subscription which contains more private identities, the HSS adds a list of the subscription&#39;s other private user identities into the SAA. To do this it uses the Associated-Identities attribute-value pair (AVP). The Associated-Identities AVP is known by the units that use the Cx interface as containing a list of User-Name AVPs, which each contain a private user identity.  
         [0018]     Using the conventional format for 3GPP messages, the SAA message is defined as follows:  
                                                             &lt;Server-Assignment-Answer&gt; ::= &lt; Diameter Header: 301, PXY,           16777216 &gt;                &lt; Session-Id &gt;           {Vendor-Specific-Application-Id}           [ Result-Code ]           [Experimental-Result ]           { Auth-Session-State }           { Origin-Host }           { Origin-Realm }           [ User-Name ]           *[ Supported-Features ]           [ User-Data ]           [ Charging-Information ]           *[ Proxy-Info ]           *[ Route-Record ]           [ Associated-Identities ]           *[ AVP ]                      
 
         [0019]     and the Associated-Identities field is defined as follows:  
                                                             Associated-Identities ::= &lt;AVP header: xxx&gt;                *[User-Name]           *[AVP]                      
 
         [0020]     The term “xxx” indicates a number, which can be selected to comply with the requirements of the system.  
         [0021]     Based on the associated private user identities that it receives the S-CSCF is able to learn the IMS subscription&#39;s private user identities before carrying out further actions, and pre-store them into its database.  
         [0022]     If a new private user identity is added into the IMS subscription in the HSS, the HSS informs the S-CSCF by sending a Push-Profile-Request (PPR) to the S-CSCF. The PPR contains as a key any of the private user identities that the S-CSCF already posses and the updated list of the associated private user identities in the Associated-Identities AVP. The AVP contains also the new private user identity. The S-CSCF identifies that it does so and stores the new identity in its database.  
         [0023]     The format of the push-profile request message is as follows:  
                                                             &lt; Push-Profile-Request &gt; ::= &lt; Diameter Header: 305, REQ, PXY,           16777216 &gt;                &lt; Session-Id &gt;           { Vendor-Specific-Application-Id }           { Auth-Session-State }           { Origin-Host }           { Origin-Realm }           { Destination-Host }           { Destination-Realm }           { User-Name }           *[ Supported-Features ]            [ User-Data ]           [ Charging-Information ]           *[ Proxy-Info ]           *[ Route-Record ]           [ Associated-Identities ]           *[ AVP ]                      
 
         [0024]     If an existing private user identity is deleted from a subscription, the HSS utilises a Registration-Termination-Request (RTR) message to inform the S-CSCF. The basis of a message is currently specified in the 3GPP standards. However, at present the RTR may contain only one private identity (i.e. User-Name AVP) at a time. The present inventors have identified that the efficiency with which the RTR message is used may be improved by additionally including the Associated-Identities AVP in the RTR command. According to this enhancement, the RTR command would have the following format:  
                                                             &lt;Registration-Termination-Requst&gt; ::=&lt; Diameter Header: 304,           16777216, REQ &gt;                &lt; Session-Id &gt;           { Vendor-Specific-Application-Id }           { Auth-Session-State }           { Origin-Host }           { Origin-Realm }           { Destination-Host }           { Destination-Realm }           { User-Name }           *[ Supported-Features ]           *[ Public-Identity ]           { Deregistration-Reason }            [ Associated-Identities ]           *[ Proxy-Info ]           *[ Route-Record ]           *[ AVP ]                      
 
         [0025]     The following is a list of 3GPP A VP codes suitable for implementing the features described above in conjunction with other features of the 3GPP system.  
                                                                                                                                                                                               TABLE 7.1                           3GPP specific AVP codes            AVP           Specified in       Code   Attribute Name   Data Type   the 3GPP TS                    Note: The AVP codes from 1 to 255 are reserved for backwards       compatibility with 3GPP RADIUS Vendor Specific Attributes       (See TS 29.061 [13])       Note: The AVP codes from 256 to 299 are reserved for future use.                29.234 [6]            Note: The AVP codes from 300 to 399 are reserved for TS 29.234                29.109 [7]            Note: The AVP codes from 400 to 499 are reserved for TS 29.109            500   Abort-Cause   Enumerated   29.209 [8]       501   Access-Network-Charging-Address   Address       502   Access-Network-Charging-   Grouped           Identifier       503   Access-Network-Charging-   OctetString           Identifier-Value       504   AF-Application-Identifier   OctetString       505   AF-Charging-Identifier   OctetString       506   Authorization-Token   OctetString       507   Flow-Description   IPFilterRule       508   Flow-Grouping   Grouped       509   Flow-Number   Unsigned32       510   Flows   Grouped       511   Flow-Status   Enumerated       512   Flow-Usage   Enumerated       513   Gq-Specific-Action   Enumerated       514   Max-Requested-Bandwidth   Unsigned32       515   Max-Requested-Bandwidth-DL   Unsigned32       516   Max-Requested-Bandwidth-UL   Unsigned32       517   Media-Component-Description   Grouped       518   Media-Component-Number   Unsigned32       519   Media-Sub-Component AVP   Grouped       520   Media-Type   Enumerated       521   RR-Bandwidth   Unsigned32       522   RS-Bandwidth   Unsigned32       523   SIP-Forking-Indication   Enumerated            Note: The AVP codes from 524 to 599 are reserved for TS 29.209            600   Visited-Network-Identifier   OctetString   29.229 [2]       601   Public-Identity   UTF8String       602   Server-Name   UTF8String       603   Server-Capabilities   Grouped       604   Mandatory-Capability   Unsigned32       605   Optional-Capability   Unsigned32       606   User-Data   OctetString       607   SIP-Number-Auth-Items   Unsigned32       608   SIP-Authentication-Scheme   UTF8String       609   SIP-Authenticate   OctetString       610   SIP-Authorization   OctetString       611   SIP-Authentication-Context   OctetString       612   SIP-Auth-Data-Item   Grouped       613   SIP-Item-Number   Unsigned32       614   Server-Assignment-Type   Enumerated       615   Deregistration-Reason   Grouped       616   Reason-Code   Enumerated       617   Reason-Info   UTF8String       618   Charging-Information   Grouped       619   Primary-Event-Charging-Function-   DiameterURI           Name       620   Secondary-Event-Charging-   DiameterURI           Function-Name       621   Primary-Charging-Collection-   DiameterURI           Function-Name       622   Secondary-Charging-Collection-   DiameterURI           Function-Name       623   User-Authorization-Type   Enumerated       624   User-Data-Already-Available   Enumerated       625   Confidentiality-Key   OctetString       626   Integrity-Key   OctetString       627   User-Data-Request-Type   Enumerated       628   Supported-Features   Grouped       629   Feature-List-ID   Unsigned32       630   Feature-List   Unsigned32       631   Supported-Applications   Grouped       632   Associated-Identities   Grouped            Note: The AVP codes from 633 to 699 are reserved for TS 29.229.            700   User-Identity   Grouped   29.329 [4]       701   MSISDN   OctetString       702   User-Data   OctetString       703   Data-Reference   Enumerated       704   Service-Indication   OctetString       705   Subs-Req-Type   Enumerated       706   Requested-Domain   Enumerated       707   Current-Location   Enumerated       708   Identity-Set   Enumerated            Note: The AVP codes from 709 to 799 are reserved for TS 29.329.                32.299 [5]            Note: The AVP codes from 800 to 899 are reserved for TS 32.299                29.061 [13]            Note: The AVP codes from 900 to 999 are reserved for TS 29.061                29.210 [15]            Note: The AVP codes from 1000 to 1099 are reserved for TS 29.210                  
 
 The following is a description of a S-CSCF registration/deregistration notification procedure suitable for implementing the features described above in the 3GPP system. 
 
         [0026]     This procedure is used between the S-CSCF and the HSS. The procedure is invoked by the S-CSCF, corresponds to the combination of the operations Cx-Put and Cx-Pull (see 3GPP TS 23.228[1]) and is used: 
        To assign an S-CSCF to a Public User Identity, or to clear the name of the S-CSCF assigned to one or more Public User Identities.     To download from HSS the relevant user information that the S-CSCF needs to serve the user.        
 
         [0029]     This procedure is mapped to the commands Server-Assignment-Request/Answer in the Diameter application specified in 3GPP TS 29.229[5]. Tables 6.1.2.1 and 6.1.2.2 describe the involved information elements.  
                                 TABLE 6.1.2.1                           S-CSCF registration/deregistration notification request                Mapping               Information   to       element   Diameter       name   AVP   Cat.   Description               Public   Public-   C   Public User Identity or list of Public User Identities.       User   Identity       One and only one Public User Identity shall be present if       Identity           the Server-Assignment-Type is any value other than       (See 7.2)           TIMEOUT_DEREGISTRATION,                   USER_DEREGISTRATION or                   ADMINISTRATIVE_DEREGISTRATION.                   If Server-Assignment-Type indicates deregistration of                   some type and Private User Identity is not present in the                   request, at least one Public User Identity shall be                   present.       S-CSCF   Server-   M   Name of the S-CSCF.       Name   Name       (See 7.4)       Private   User-   C   Private User Identity.       User   Name       It shall be present if it is available when the S-CSCF       Identity           issues the request.       (See 7.3)           It may be absent during the initiation of a session to an                   unregistered user. In such situation, Server-Assignment-                   Type shall contain the value UNREGISTERED_USER.                   In case of de-registration, Server-Assignment-Type                   equal to TIMEOUT_DEREGISTRATION,                   USER_DEREGISTRATION or                   ADMINISTRATIVE_DEREGISTRATION, if no Public                   User Identity AVPs are present then Private User                   Identity shall be present.       Server   Server-   M   Type of update the S-CSCF requests in the HSS (e.g.:       Assignment   Assignment-       de-registration). See 3GPP TS 29.229 [5] for all the       Type   Type       possible values.       (See 7.8)       User Data   User-Data-   M   This indicates if the user profile is already available in       Already   Already-       the S-CSCF.       Available   Available       In the case where Server-Assignment-Type is not equal       (See 7.16)           to NO_ASSIGNMENT, REGISTRATION,                   RE_REGISTRATION or UNREGISTERED_USER, the                   HSS shall not use User Data Already Available when                   processing the request.       Routing   Destination-   C   If the S-CSCF knows the HSS name, the Destination-       Information   Host       Host AVP shall be present in the command.       (See 7.13)           This information is available if the request belongs to an                   already existing registration, e.g. in case of the re-                   registration, where the HSS name is stored in the S-                   CSCF. The HSS name is obtained from the Origin-Host                   AVP, which is received from the HSS, e.g. included in                   the MAA command.                   This information may not be available if the command is                   sent as a consequence of a session termination for an                   unregistered user. In this case the Destination-Host AVP                   is not present and the command is routed to the next                   Diameter node, e.g. SLF, based on the Diameter routing                   table in the S-CSCF.                  
 
         [0030]                                      TABLE 6.1.2.2                           S-CSCF registration/deregistration notification response                Mapping               Information   to       element   Diameter       name   AVP   Cat.   Description               Private   User-   C   Private User Identity.       User   Name       It shall be present if it is available when the HSS sends       Identity           the response.       (See 7.3)           It may be absent in the following error case: when the                   Server-Assignment-Type of the request is                   UNREGISTERED_USER and the received Public User                   Identity is not known by the HSS.       Registration   Result-   M   Result of registration.       result   Code/       Result-Code AVP shall be used for errors defined in the       (See 7.6)   Experimental-       Diameter Base Protocol.           Result       Experimental-Result AVP shall be used for Cx/Dx errors.                   This is a grouped AVP which contains the 3GPP Vendor                   ID in the Vendor-Id AVP, and the error code in the                   Experimental-Result-Code AVP.       User   User-Data   C   Relevant user profile.       Profile           It shall be present when Server-Assignment-Type in the       (See 7.7)           request is equal to NO_ASSIGNMENT,                   REGISTRATION, RE_REGISTRATION or                   UNREGISTERED_USER according to the rules defined                   in section 6.6.                   If the S-CSCF receives more data than it is prepared to                   accept, it shall perform the de-registration of the user                   with User-Authorization-Type set to                   DEREGISTRATION_TOO_MUCH_DATA and send                   back a SIP 3xx or 480 (Temporarily Unavailable)                   response, which shall trigger the selection of a new S-                   CSCF by the I-CSCF, as specified in 3GPP TS 24.229                   [8].       Charging   Charging-   C   Addresses of the charging functions.       Information   Information       It shall be present when the User-Data AVP is sent to       (See 7.12)           the S-CSCF.                   When this parameter is included, the Primary Charging                   Collection Function address shall be included. All other                   elements shall be included if they are available.       Associated   Associated-   C   This AVP contains the private user identities, which       Private   Identities       belong to the same IMS subscription as the private user       Identities           identity or public user identity received in the SAR                   command.                   If the IMS subscription contains only single private user                   identity, this AVP shall not be present.                    
 Detailed Behaviour 
 
         [0031]     On registering/deregistering a Public User Identity the S-CSCF shall inform the HSS. The same procedure is used by the S-CSCF to get the user information which contains the user profile and the charging information. The relevant user profile downloaded is described in more detailed in sections 6.5.1 and 6.6. The HSS holds information about the state of registration of all the identities of the user. The S-CSCF uses this procedure to update such states. For implicitly registered identities, the rules defined in Section 6.5.1 shall apply. The HSS shall, in the following order (in case of an error in any of the steps the HSS shall stop processing and return the corresponding error code, see 3GPP TS 29.229[5]): 
        1. Check that the user is known. If not Experimental-Result-Code shall be set to DIAMETER_ERROR_USER_UNKNOWN. If there is neither a Public User Identity nor a Private User Identity included, the Experimental-Result-Code shall be set to DIAMETER_MISSING_USER_ID.     2. The HSS may check whether the Private and Public User Identities received in the request belong to the same user. If not Experimental-Result-Code shall be set to DIAMETER_ERROR_IDENTITIES_DONT_MATCH.     3. Check the Server Assignment Type value received in the request: 
            If it indicates REGISTRATION or RE_REGISTRATION, the HSS shall download the relevant user information. If the Public User Identity&#39;s authentication pending flag which is specific for the Private User Identity is set, the HSS shall clear it. The Result-Code shall be set to DIAMETER_SUCCESS and the HSS shall set the registration state of the Public User Identity as registered (if not already registered). If there are multiple private user identities, which belong to the served IMS subscription, the Associated-Identities AVP shall be added to the answer message and it shall contain all private user identities associated to the IMS subscription.     Only one Public User Identity shall be present in the request. If more than one identity is present the Result-Code shall be set to DIAMETER_AVP_OCCURS_TOO_MANY_TIMES and no user information shall be returned. If there is no Public User Identity present, the Experimental-Result-Code shall be set to DIAMETER_MISSING_USER_ID.     If it indicates UNREGISTERED_USER, the HSS shall store the S-CSCF name, set the registration state of the Public User Identity as unregistered, i.e. registered as a consequence of a terminating call and download the relevant user information. If there are multiple Private User Identities associated to the Public User Identity in the HSS, the HSS shall arbitrarily select one of the Private User Identities and put it into the response message. The Result-Code shall be set to DIAMETER_SUCCESS. If there are multiple private user identities, which belong to the served IMS subscription, the Associated-Identities AVP shall be added to the answer message and it shall contain all private user identities associated to the IMS subscription.     Only one Public User Identity shall be present in the request. If more than one identity is present the Result-Code shall be set to DIAMETER_AVP_OCCURS_TOO_MANY_TIMES and the modifications specified in the previous paragraph shall not be performed. If there is no Public User Identity present, the Experimental-Result-Code shall be set to DIAMETER_MISSING_USER_ID.     If it indicates TIMEOUT_DEREGISTRATION, USER_DEREGISTRATION, DEREGISTRATION_TOO_MUCH_DATA or ADMINISTRATIVE_DEREGISTRATION, the HSS shall clear the S-CSCF name associated to the Private User Identity for all the Public User Identities that the S-CSCF indicated in the request and set the registration state of the identities as not registered. If no Public User Identity is present in the request, the Private User Identity shall be present; in this case the HSS shall clear the S-CSCF name for all the Public User Identities associated to the Private User Identity and set their registration state to not registered. The Result-Code shall be set to DIAMETER_SUCCESS.     If it indicates TIMEOUT_DEREGISTRATION_STORE_SERVER_NAME or USER_DEREGISTRATION_STORE_SERVER_NAME the HSS decides whether to keep the S-CSCF name associated to the Private User Identity stored or not for all the Public User Identities that the S-CSCF indicated in the request. If no Public User Identity is present in the request, the Private User Identity shall be present. If the HSS decides to keep the S-CSCF name stored the HSS shall keeps the S-CSCF name stored for all the Public User Identities associated to the Private User Identity and set their registration state to unregistered.     The Result-Code shall be set to DIAMETER_SUCCESS.     If the HSS decides not to keep the S-CSCF name the Experimental-Result-Code shall be set to DIAMETER_SUCCESS_SERVER_NAME_NOT_STORED. If the HSS received Public User Identities in the request, the HSS shall set the registration state to not registered for the Public User Identity(ies) that the S-CSCF indicated in the request. If the HSS received a Private User Identity in the request, the HSS shall set the registration state of all Public User Identities related to the private identity to not registered.     If it indicates NO_ASSIGNMENT, the HSS checks whether the user is assigned for the S-CSCF requesting the data and download the relevant user information. The Result-Code shall be set to DIAMETER_SUCCESS. If there are multiple private user identities, which belong to the served IMS subscription, the Associated-Identities AVP shall be added to the answer message and it shall contain all private user identities associated to the IMS subscription.     If the requesting S-CSCF is not the same as the assigned S-CSCF, the Result-Code shall be set to DIAMETER_UNABLE_TO COMPLY.     Only one Public User Identity shall be present in the request. If more than one Public User Identity is present the Result-Code shall be set to DIAMETER_AVP_OCCURS_TOO_MANY_TIMES and no user information shall be returned. If there is no Public User Identity present, the Experimental-Result-Code shall be set to DIAMETER_MISSING_USER_ID.     If it indicates AUTHENTICATION_FAILURE or AUTHENTICATION_TIMEOUT, the HSS shall clear the S-CSCF name for the Public User Identity associated to the Private User Identity that the S-CSCF indicated in the request and set the registration state of the identity as not registered. If the Public User Identity&#39;s authentication pending flag which is specific for the Private User Identity is set, the HSS shall clear it. The Result-Code shall be set to DIAMETER_SUCCESS.     Only one Public User Identity shall be present in the request. If more than one identity is present the Result-Code shall be set to DIAMETER_AVP_OCCURS_TOO_MANY_TIMES and the modifications specified in the previous paragraph shall not be performed. If there is no Public User Identity present, the Experimental-Result-Code shall be set to DIAMETER_MISSING_USER_ID.    
               
 
         [0048]     If the HSS cannot fulfil the received request, e.g. due to database error, it shall set the Result-Code to DIAMETER_UNABLE_TO_COMPLY. The HSS shall not modify any user state nor download any user Public User Identity information to the S-CSCF.  
         [0049]     See chapter 8.1.2 and 8.1.3 for the description of the handling of the error situations: reception of an S-CSCF name different from the one stored in the HSS and reception of a Server-Assignment-Type value not compatible with the registration state of the user.  
         [0000]     The following is a description of an authentication procedure suitable for implementing the features described above in the 3GPP system.  
         [0050]     This procedure is used between the S-CSCF and the HSS to exchange information to support the authentication between the end user and the home IMS network. The procedure is invoked by the S-CSCF, corresponds to the combination of the operations Cx-AV-Req and Cx-Put (see 3GPP TS 33.203[3]) and is used: 
        To retrieve authentication vectors from the HSS.     To resolve synchronization failures between the sequence numbers in the UE and the HSS.        
 
         [0053]     This procedure is mapped to the commands Multimedia-Auth-Request/Answer in the Diameter application specified in 3GPP TS 29.229[5]. Tables 6.3.1-6.3.5 detail the involved information elements.  
                                 TABLE 6.3.1                           Authentication request                Mapping               Information   to       element   Diameter       name   AVP   Cat.   Description               Public   Public-   M   This information element contains the public identity of       User   Identity       the user       Identity       (See 7.2)       Private   User-   M   This information element contains the user private       User   Name       identity       Identity       (See 7.3)       Number   SIP-   M   This information element indicates the number of       Authentication   Number-       authentication vectors requested       Items   Auth-Items       (See 7.10)       Authentication   SIP-Auth-   M   See Tables 6.3.2 and 6.3.3 for the contents of this       Data   Data-Item       information element. The content shown in table 6.3.2       (See 7.9)           shall be used for a normal authentication request; the                   content shown in table 6.3.3 shall be used for an                   authentication request after synchronization failure.       S-CSCF   Server-   M   This information element contains the name (SIP URL)       Name   Name       of the S-CSCF.       (See 7.4)       Routing   Destination-   C   If the S-CSCF knows the HSS name this AVP shall be       Information   Host       present.       (See 7.13)           This information is available if the MAR belongs to an                   already existing registration, e.g. in case of the re-                   registration, where the HSS name is stored in the S-                   CSCF. The HSS name is obtained from the Origin-Host                   AVP, which is received from the HSS, e.g. included in                   the MAA command.                   This information may not be available if the command is                   sent in case of the initial registration. In this case the                   Destination-Host AVP is not present and the command                   is routed to the next Diameter node, e.g. SLF, based on                   the Diameter routing table in the client.                  
 
         [0054]    
       
         
               
             
               
               
               
               
             
           
               
                 TABLE 6.3.2 
               
             
             
               
                   
               
               
                   
               
               
                 Authentication Data content - request 
               
             
          
           
               
                   
                 Mapping 
                   
                   
               
               
                 Information 
                 to 
               
               
                 element 
                 Diameter 
               
               
                 name 
                 AVP 
                 Cat. 
                 Description 
               
               
                   
               
               
                 Authentication 
                 SIP- 
                 M 
                 This information element 
               
               
                 Scheme 
                 Authentication- 
                   
                 indicates the authentication 
               
               
                 (See 7.9.2) 
                 Scheme 
                   
                 scheme. It shall contain 
               
               
                   
                   
                   
                 “Digest-AKAv1-MD5”. 
               
               
                   
               
             
          
         
       
     
         [0055]    
       
         
               
             
               
               
               
               
             
           
               
                 TABLE 6.3.3 
               
             
             
               
                   
               
               
                   
               
               
                 Authentication Data content - request, synchronization failure 
               
             
          
           
               
                   
                 Mapping 
                   
                   
               
               
                 Information 
                 to 
               
               
                 element 
                 Diameter 
               
               
                 name 
                 AVP 
                 Cat. 
                 Description 
               
               
                   
               
               
                 Authentication 
                 SIP- 
                 M 
                 Authentication scheme. It shall 
               
               
                 Scheme 
                 Authentication- 
                   
                 contain “Digest-AKAv1- 
               
               
                 (See 7.9.2) 
                 Scheme 
                   
                 MD5”. 
               
               
                 Authorization 
                 SIP- 
                 M 
                 It shall contain the concatenation 
               
               
                 Information 
                 Authorization 
                   
                 of nonce, as sent to the terminal, 
               
               
                 (See 7.9.4) 
                   
                   
                 and auts, as received from 
               
               
                   
                   
                   
                 the terminal. Nonce and auts 
               
               
                   
                   
                   
                 shall both be binary encoded. 
               
               
                   
               
             
          
         
       
     
         [0056]    
       
         
               
             
               
               
               
               
             
           
               
                 TABLE 6.3.4 
               
             
             
               
                   
               
               
                   
               
               
                 Authentication answer 
               
             
          
           
               
                   
                 Mapping 
                   
                   
               
               
                 Information 
                 to 
               
               
                 element 
                 Diameter 
               
               
                 name 
                 AVP 
                 Cat. 
                 Description 
               
               
                   
               
               
                 User 
                 Public- 
                 C 
                 User public identity. It shall be present when the result is 
               
               
                 Identity 
                 Identity 
                   
                 DIAMETER_SUCCESS. 
               
               
                 (See 7.2) 
               
               
                 Private 
                 User- 
                 C 
                 User private identity. It shall be present when the result 
               
               
                 User 
                 Name 
                   
                 is DIAMETER_SUCCESS. 
               
               
                 Identity 
               
               
                 (See 7.3) 
               
               
                 Number 
                 SIP- 
                 C 
                 This AVP indicates the number of authentication vectors 
               
               
                 Authentication 
                 Number- 
                   
                 delivered in the Authentication Data information 
               
               
                 Items 
                 Auth-Items 
                   
                 element. It shall be present when the result is 
               
               
                 (See 7.10) 
                   
                   
                 DIAMETER_SUCCESS. 
               
               
                 Authentication 
                 SIP-Auth- 
                 C 
                 If the SIP-Number-Auth-Items AVP is equal to zero or it 
               
               
                 Data 
                 Data-Item 
                   
                 is not present, then this AVP shall not be present. 
               
               
                 (See 7.9) 
                   
                   
                 See Table 6.3.5 for the contents of this information 
               
               
                   
                   
                   
                 element. 
               
               
                 Result 
                 Result- 
                 M 
                 Result of the operation. 
               
               
                 (See 7.6) 
                 Code/ 
                   
                 Result-Code AVP shall be used for errors defined in the 
               
               
                   
                 Experimental- 
                   
                 Diameter Base Protocol. 
               
               
                   
                 Result 
                   
                 Experimental-Result AVP shall be used for Cx/Dx errors. 
               
               
                   
                   
                   
                 This is a grouped AVP which contains the 3GPP Vendor 
               
               
                   
                   
                   
                 ID in the Vendor-Id AVP, and the error code in the 
               
               
                   
                   
                   
                 Experimental-Result-Code AVP. 
               
               
                 Associated 
                 Associated- 
                 C 
                 This AVP contains the private user identities, which 
               
               
                 Private 
                 Identities 
                   
                 belong to the same IMS subscription as the private user 
               
               
                 Identities 
                   
                   
                 identity received in the MAR command. 
               
               
                   
                   
                   
                 If the IMS subscription contains only single private user 
               
               
                   
                   
                   
                 identity, this AVP shall not be present. 
               
               
                   
               
             
          
         
       
     
         [0057]                                      TABLE 6.3.5                           Authentication Data content - response                Mapping               Information   to       element   Diameter       name   AVP   Cat.   Description               Item   SIP-Item-   C   This information element shall be present in a SIP-Auth-       Number   Number       Data-Item grouped AVP in circumstances where there       (See 7.9.1)           are multiple occurrences of SIP-Auth-Data-Item AVPs,                   and the order in which they should be processed is                   significant. In this scenario, SIP-Auth-Data-Item AVPs                   with a low SIP-Item-Number value should be processed                   before SIP-Auth-Data-Items AVPs with a high SIP-Item-                   Number value.       Authentication   SIP-   M   Authentication scheme. It shall contain “Digest-AKAv1-       Scheme   Authentication-       MD5”.       (See 7.9.2)   Scheme       Authentication   SIP-   M   It shall contain, binary encoded, the concatenation of the       Information   Authenticate       authentication challenge RAND and the token AUTN.       (See 7.9.3)           See 3GPP TS 33.203 [3] for further details about RAND                   and AUTN.       Authorization   SIP-   M   It shall contain binary encoded, the expected response       Information   Authorization       XRES. See 3GPP TS 33.203 [3] for further details about       (See 7.9.4)           XRES.       Confidentiality   Confidentiality-   O   This information element, if present, shall contain the       Key   Key       confidentiality key. It shall be binary encoded.       (See 7.9.5)       Integrity   Integrity-   M   This information element shall contain the integrity       Key   Key       key. It shall be binary encoded.       (See 7.9.6)                    
 Detailed Behaviour 
 
         [0058]     The HSS shall, in the following order (in case of an error in any of the steps the HSS shall stop processing and return the corresponding error code, see 3GPP TS 29.229[5]): 
        1. Check that the user exists in the HSS. If not Experimental-Result-Code shall be set to DIAMETER_ERROR_USER_UNKNOWN.     2. The HSS may check that the private and public identities belong to the same user. If not Experimental-Result-Code shall be set to DIAMETER_ERROR_IDENTITIES_DONT_MATCH.     3. Check that the authentication scheme indicated in the request is supported. If not Experimental-Result-Code shall be set to DIAMETER_ERROR_AUTH_SCHEME_UNSUPPORTED.     4. If the request indicates there is a synchronization failure, the HSS shall compare the S-CSCF name received in the request to the S-CSCF name stored in the HSS: 
            If they are identical the HSS shall process AUTS as described in 3GPP TS 33.203[3] and return the requested authentication information. The Result-Code shall be set to DIAMETER_SUCCESS.    
            5. Check the registration status of the public identity received in the request: 
            If it is registered, the HSS shall compare the S-CSCF name received in the request to the S-CSCF name stored in the HSS: 
                If they are different, the HSS shall store the S-CSCF name. The HSS shall download Authentication-Data-Item stored up to a maximum specified in SIP-Number-Auth-Items received in the command Multimedia-Auth-Request. The HSS shall set the public identity&#39;s authentication pending flag which is specific to the private identity which was received in the request. The Result-Code shall be set to DIAMETER_SUCCESS.     If they are identical, the HSS shall download Authentication-Data-Item stored up to a maximum specified in SIP-Number-Auth-Items received in the command Multimedia-Auth-Request. The Result-Code shall be set to DIAMETER_SUCCESS.    
                If it is unregistered (i.e. registered as a consequence of a terminating call to unregistered user or there is an S-CSCF keeping the user profile stored), the HSS shall compare the S-CSCF name received in the request to the S-CSCF name stored in the HSS: 
                If they are different, the HSS shall store the S-CSCF name. The HSS shall download Authentication-Data-Item stored up to a maximum specified in SIP-Number-Auth-Items received in the command Multimedia-Auth-Request. The HSS shall set the public identity&#39;s authentication pending flag which is specific to the private identity which was received in the request. The Result-Code shall be set to DIAMETER_SUCCESS.     If they are identical, the HSS shall download Authentication-Data-Item stored up to a maximum specified in SIP-Number-Auth-Items received in the command Multimedia-Auth-Request. The HSS shall set the public identity&#39;s authentication pending flag which is specific to the private identity that was received in the request. The Result-Code shall be set to DIAMETER_SUCCESS.    
                If it is not registered, the HSS shall store the S-CSCF name. The HSS shall download Authentication-Data-Item stored up to a maximum specified in SIP-Number-Auth-Items received in the command Multimedia-Auth-Request. The HSS shall set the public identity&#39;s authentication pending flag which is specific to the private identity that was received in the request. The Result-Code shall be set to DIAMETER_SUCCESS.    
            6. If there are multiple private user identities, which belong to the served IMS subscription, the Associated-Identities AVP shall be added to the answer message and it shall contain all private user identities associated to the IMS subscription.        
 
         [0073]     Exceptions to the cases specified here shall be treated by HSS as error situations, the Result-Code shall be set to DIAMETER_UNABLE_TO_COMPLY. No authentication information shall be returned.  
         [0074]     This associated private identities information element indicates to the S-CSCF the private user identities, which belong to the same IMS subscription. See 3GPP TS 29.229[5].  
         [0000]     The following is a description of the Server-Assignment-Answer (SAA) Command suitable for implementing the features described above in the 3GPP system.  
         [0075]     The Server-Assignment-Answer (SAA) command, indicated by the Command-Code field set to 301 and the ‘R’ bit cleared in the Command Flags field, is sent by a server in response to the Server-Assignment-Request command. The Result-Code or Experimental-Result AVP may contain one of the values defined in section 6.2 in addition to the values defined in IETF RFC 3588[6]. If Result-Code or Experimental-Result does not inform about an error, the User-Data AVP shall contain the information that the S-CSCF needs to give service to the user.  
                                                             Message Format           &lt;Server-Assignment-Answer&gt; ::= &lt; Diameter Header: 301, PXY,           16777216 &gt;                &lt; Session-Id &gt;           { Vendor-Specific-Application-Id }           [ Result-Code ]            [Experimental-Result ]            { Auth-Session-State }            { Origin-Host }            { Origin-Realm }            [ User-Name ]            *[ Supported-Features ]            [ User-Data ]            [ Charging-Information ]            [ Associated-Identities ]            *[ AVP ]            *[ Proxy-Info ]            *[ Route-Record ]                      
 
 The following is a description of the Multimedia-Auth-Answer (MAA) Command suitable for implementing the features described above in the 3GPP system. 
 
         [0076]     The Multimedia-Auth-Answer (MAA) command, indicated by the Command-Code field set to 303 and the ‘R’ bit cleared in the Command Flags field, is sent by a server in response to the Multimedia-Auth-Request command. The Result-Code or Experimental-Result AVP may contain one of the values defined in section 6.2 in addition to the values defined in IETF RFC 3588[6].  
                                                                       Message Format                &lt; Multimedia-Auth-Answer &gt; ::= &lt; Diameter Header: 303,           PXY, 16777216 &gt;                &lt; Session-Id &gt;           { Vendor-Specific-Application-Id }           [ Result-Code ]           [ Experimental-Result ]           { Auth-Session-State }           { Origin-Host }           { Origin-Realm }           [ User-Name ]           *[ Supported-Features ]            [ Public-Identity ]            [ SIP-Number-Auth-Items ]           * [ SIP-Auth-Data-Item ]           [ Associated-Identities ]           * [ AVP ]           * [ Proxy-Info ]           * [ Route-Record ]                      
 
 The following is a description of the A VPs suitable for implementing the features described above in the 3GPP system in conjunction with other features of the system. 
 
         [0077]     The following table describes the Diameter AVPs defined for the Cx interface protocol, their AVP Code values, types, possible flag values and whether or not the AVP may be encrypted. The Vendor-Id header of all AVPs defined in this specification shall be set to 3GPP (10415).  
                                                                                                         TABLE 6.3.1                           Diameter Multimedia Application AVPs                AVP Flag rules                    AVP   Section               Should   Must   May       Attribute Name   Code   defined   Value Type   Must   May   not   not   Encr.                    Visited-Network-   600   6.3.1   OctetString   M, V               No       Identifier       Public-Identity   601   6.3.2   UTF8String   M, V               N       Server-Name   602   6.3.3   UTF8String   M, V               No       Server-Capabilities   603   6.3.4   Grouped   M, V               No       Mandatory-Capability   604   6.3.5   Unsigned32   M, V               No       Optional-Capability   605   6.3.6   Unsigned32   M, V               No       User-Data   606   6.3.7   OctetString   M, V               No       SIP-Number-Auth-   607   6.3.8   Unsigned32   M, V               No       Items       SIP-Authentication-   608   6.3.9   UTF8String   M, V               No       Scheme       SIP-Authenticate   609   6.3.10   OctetString   M, V               No       SIP-Authorization   610   6.3.11   OctetString   M, V               No       SIP-Authentication-   611   6.3.12   OctetString   M, V               No       Context       SIP-Auth-Data-Item   612   6.3.13   Grouped   M, V               No       SIP-Item-Number   613   6.3.14   Unsigned32   M, V               No       Server-Assignment-   614   6.3.15   Enumerated   M, V               No       Type       Deregistration-Reason   615   6.3.16   Grouped   M, V               No       Reason-Code   616   6.3.17   Enumerated   M, V               No       Reason-Info   617   6.3.18   UTF8String   M, V               No       Charging-Information   618   6.3.19   Grouped   M, V               No       Primary-Event-   619   6.3.20   DiameterURI   M, V               No       Charging-Function-       Name       Secondary-Event-   620   6.3.21   DiameterURI   M, V               No       Charging-Function-       Name       Primary-Charging-   621   6.3.22   DiameterURI   M, V               No       Collection-Function-       Name       Secondary-Charging-   622   6.3.23   DiameterURI   M, V               No       Collection-Function-       Name       User-Authorization-   623   6.3.24   Enumerated   M, V               No       Type       User-Data-Already-   624   6.3.26   Enumerated   M, V               No       Available       Confidentiality-Key   625   6.3.27   OctetString   M, V               No       Integrity-Key   626   6.3.28   OctetString   M, V               No       User-Data-Request-   627   6.3.25   Enumerated   M, V               No       Type       Supported-Features   628   6.3.29   Grouped   V   M           No       Feature-List-ID   629   6.3.30   Unsigned32   V           M   No       Feature-List   630   6.3.31   Unsigned32   V           M   No       Supported-Applications   631   6.3.32   Grouped   V           M   No       Associated-Identities   632   6.3.33   Grouped   M, V               No                 NOTE 1:            The AVP header bit denoted as ‘M’, indicates whether support of the AVP is required. The AVP header bit denoted as ‘V’, indicates whether the optional Vendor-ID field is present in the AVP header. For further details, see IETF RFC 3588 [6].            NOTE 2:            Depending on the concrete command.             
 
         [0078]     The Associated-Identities AVP is of type Grouped and it contains the private user identities associated to an IMS subscription.  
                                                   AVP format             Associated-Identities ::= &lt;AVP header: 632 10415&gt;                       *[User-Name]                       *[AVP]                      
 
         [0079]     The present invention is applicable in systems other than the present 3G communications system. In principle, the ability to inform a service-providing entity (e.g. an S-CSCF) of multiple parings of public and private user identities is useful in a wide range of systems. It is particularly advantageous to achieve this by means of the same message as is used to inform the service-providing entity of information regarding a primary identity pair (e.g. a SAR message and/or a PPR message). Correspondingly, it is also advantageous to be able to trigger the deletion of multiple parings through a single message (e.g. an RTR message).  
         [0080]     The applicant hereby discloses in isolation each individual feature described herein and any combination of two or more such features, to the extent that such features or combinations are capable of being carried out based on the present specification as a whole in the light of the common general knowledge of a person skilled in the art, irrespective of whether such features or combinations of features solve any problems disclosed herein, and without limitation to the scope of the claims. The applicant indicates that aspects of the present invention may consist of any such individual feature or combination of features. In view of the foregoing description it will be evident to a person skilled in the art that various modifications may be made within the scope of the invention.