WO2007144681A1

WO2007144681A1 - Method and system for providing portability

Info

Publication number: WO2007144681A1
Application number: PCT/IB2006/001534
Authority: WO
Inventors: Mikko Aittola; Miikka POIKSELKÄ
Original assignee: Nokia Inc
Current assignee: Nokia Inc
Priority date: 2006-06-09
Filing date: 2006-06-09
Publication date: 2007-12-21
Anticipated expiration: 2008-12-09

Abstract

The present invention relates to a method and network elements for providing portability of at least one of a name and a number of a subscriber between a first network and a second network. A first network element is configured to re-spond to a location information request, which comprises at least one of the name and the number of the subscriber in the first network, with an answer indicating an address of an entry point network element of the second network, and a second network element is configured to respond to a location information request, which comprises the at least one of the name and the number of the subscriber in the first network, with an answer indicating an address of a serving network element of the second network. Thereby, a distributed architecture for portability can be implemented in a simple manner involving minimum network changes.

Description

Method and system for providing portability

FIELD OF THE INVENTION

The present invention relates to a method, network elements and system for providing portability of at least one of a name and a number of a subscriber between a first network and a second network. In particular, the present invention relates to name and/or number portability between IMS (Internet Protocol Multimedia Subsystem) networks of different network operators.

BACKGROUND OF THE INVENTION

Number or name portability (MNP) is the industry agreed process by which customers can switch from one network operator to another and take their existing numbers or names with them. This process is also sometimes called migrating or transferring.

In IMS systems, user identities consist of two types: private and public user i- dentities. The private user identity is a user identity that is assigned by the home network operator and is used for such purposes as registration and authorization, while the public user identity is the identity that other users can use for requesting communication with end users. Both telecom and Internet numbering and addressing schemes can be supported as public identities. IMS communication establishment (both mobile originating and terminating) can be based on E.164/TEL Uniform Resource Indicator (URI) (e.g. tel:+4412345678) or SIP URI (sip:my.name@company.org).

In the IMS architecture, a single session control protocol is used, namely the Session Initiation Protocol (SIP). In SIP, URIs are used as simple and extensi- ble means for identifying a resource. In the IMS system, resources can be e.g. network entities and IMS users.

In the following, IMS entities involved in name and/or number portability con- cepts are briefly described together with their key functionalities.

The Proxy-Call Session Control Function (P-CSCF) is the first contact point for users within the IMS. All SIP signalling traffic from or to the terminal device or user equipment (UE) is routed via the P-CSCF. As the name of the entity indicates, the P-CSCF behaves like a proxy, which means that the P-CSCF validates the request, forwards it to selected destinations and processes and for- wards the response.

Furthermore, an Interrogating-CSCF (I-CSCF) is provided as a contact point within an operator's network for all connections destined to a subscriber of that network operator. There may be multiple l-CSCFs within an operator's network. One of the functions performed by the I-CSCF are to contact the HSS to obtain the name of the S-CSCF that is serving a user.

The HSS is the main data storage for all subscriber and service-related data of the IMS. The main data stored in the HSS include user identities, registration information, access parameters and service-triggering information.

Additionally, the Serving-CSCF (S-CSCF) is the brain of the IMS. It is located in the home network. It performs session control and registration services for UEs. While the UE is engaged in a session, the S-CSCF maintains a session state and interacts with service platforms and charging functions as needed by the network operator for support of the services. There may be multiple S-CSCFs, and S-CSCFs may have different functionalities within an operator's network.

The Subscription Locator Function (SLF) is used as a resolution mechanism that enables the I-CSCF and the S-CSCF to find the address of the HSS that holds the subscriber data for a given user identity when multiple and separately addressable HSSs have been deployed by the network operator.

Fig. 1 shows a schematic block diagram indicating how the SLF is used to find a correct HSS of a subscriber when the I-CSCF receives a SIP INVITE request in step 1 and three HSSs have been deployed. Location-Info-Request/Answer (LIR/LIA) commands are used between the I-CSCF and the HSS during the SIP session set-up to obtain the name of the S-CSCF that is serving the user or S- CSCF capabilities for S-CSCF selection. To get an HSS address, the I-CSCF or the S-CSCF sends to the SLF an LIR request aimed for the HSS (step 2). On receipt of the HSS address (here: HSS#2) from the SLF in step 3, the I-CSCF or the S-CSCF will send in step 4 an LIR requests to the HSS#2. In step 5, the HSS responds with an LIA indicating the address of the S-CSCF which has been allocated to the subscriber's UE. Finally, the initial INVITE request is routed to the specified S-CSCF (step 6).

So far, no IMS number or name portability requirements have been defined in the Release 5,6,7 specifications of the Third Generation Partnership Project (3GPP). Technical solutions which have been presented involve substantial modifications of the network architecture and protocol messages.

SUMMARY OF THE INVENTION

It is therefore an object of the present invention to provide a method and system for introducing name and/or number portability, by means of which existing pro- tocol messages and databases can be used, so that impact on existing network elements can be kept small.

This object is achieved by a method of providing portability of at least one of a name and a number of a subscriber between a first network and a second net- work, said method comprising the steps of:

• configuring a first network element to respond to a location information request, which comprises at least one of said name and said number of said subscriber in said first network, with an answer indicating an ad- dress of an entry point network element of said second network; and

• configuring a second network element to respond to a location information request, which comprises said at least one of said name and said number of said subscriber in said first network, with an answer indicating an address of a serving network element of said second network.

Furthermore, the above object is achieved by a network element for providing portability of at least one of a name and a number of a subscriber between a first network and a second network, said network element being part of said first network and being adapted to respond to a location information request, which comprises at least one of said name and said number of said subscriber in said - A -

first network, with an answer indicating an address of an entry point network element of said second network.

Additionally, the above object is achieved by a network element for providing portability of at least one of a name and a number of a subscriber between a first network and a second network, said network element being part of said second network and being adapted to respond to a location information request, which comprises said at least one of said name and said number of said subscriber in said first network, with an answer indicating an address of a serving network element of said second network.

Accordingly, when a call is established by using a subscriber's old name or number which had been allocated by a former network operator, the call is automatically routed or forwarded to the entry point network element of the new network operator, and then routed or forwarded from to the serving network element of new network operator. Hence, no specific changes are needed at the entry point network element. Moreover, there is no need to use additional parameters for the Uniform Resource Indicator (URI) to implement routing and indicating about ported user IDs, i.e., names and/or numbers. In addition, no separate portability data bases or new messages needed to query such databases are required.

Thereby, a distributed architecture can be provided for the portability, so that no single portability database is required and implementation is simple. Name and/or number portability can thus be introduced based on existing protocol messages and databases, which has only small impact on the existing address resolution mechanisms and/or home subscriber server network elements.

The proposed solution preserves the domain-based routing concept of the net- work. The SIP requests can be routed to a destination based on the domain- name so that there is no need to identify the terminating subscriber and resolve the destination network in the originating network based on the terminating subscriber identification.

It is noted that in connection with the present invention, the terms "name" and "number" are intended to designate any kind of address, identification, identity, or the like, suitable to route or connected a call to a subscriber. According to a specific example, registration of the at least one of the name and the number of the subscriber may be disabled in the first network. The disabling may be performed by setting a predetermined flag. Thereby, it can be ensured that the subscriber's name and number previously used in the first network is not registered to the first network anymore.

Additionally, a flag may be set in at least one of said first and second network elements to indicate whether said subscriber is allowed or not to register at least one of a predetermined name and a predetermined number.

Furthermore, the at least one of the name and the number previously used in the first network may be registered by an implicit registration to the second network. Portability thus does not have to be applied to registrations. Thereby, sig- naling load in the first network can be decreased.

The at least one of the name and the number of the subscriber may be implicitly registered in the second network, when at least one of a new name and a new number of the subscriber is registered in the second network.

As an example, the at least one of the name and the number may comprise a Uniform Resource Identifier. The first and second network elements may be home subscriber servers or a network elements having an address resolution mechanism. The first network may be an Internet Protocol Multimedia Subsys- tern (IMS) of a first IMS operator and the entry point network element may comprise an interrogating call session control function, and the second network may be an Internet Protocol Multimedia Subsystem (IMS) of a second IMS operator and the serving network element may comprise a serving call session control function.

As an additional option, the second network element may be adapted to add to the answer an indication that the at least one of the name and the number of the subscriber is ported to the second network. This indication may be for example a result code or an attribute value pair (AVP). Thereby, statistics can be collected about ported subscribers.

Further advantageous modifications are described in the dependent claims. BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will be now be described in greater detail based on a pre- ferred embodiment with reference to the accompanying drawings, in which:

Fig. 1 shows a schematic block diagram indicating a conventional procedure resolution procedure in an IMS environment;

Fig. 2 shows a simplified messaging diagram of a portability mechanism according to the preferred embodiment;

Fig. 3 shows a schematic flow diagram of a portability-related processing at a network element according to the preferred embodiment; and

Fig. 4 shows a schematic flow diagram of a portability-related processing at a network element according to the preferred embodiment.

DESCRIPTION OF THE PREFERRED EMBODIMENT

In the following, the preferred embodiment of the present invention will be described with respect to portability of a Public User Identity (i.e. SIP Address of Record) in an IMS network.

According to the preferred embodiment, a simple solution is introduced to achieve name portability in the 3GPP IMS architecture, wherein the HSS returns the LIA message an address of the next I-CSCF instead of an address of the S-CSCF. This functionality can also be implemented to the SLF, so that the SLF acts in the role of the HSS and - instead of sending the redirect indication with HSS address - the SLF would send its LIA message with the next I-CSCF address.

Furthermore, in the preferred embodiment, SIP registration of identities that re- quire portability is always done by utilizing implicit registration, so that the registration is always done with an identity that does not require name portability, i.e., the identities that require name portability are registered implicitly. This decreases the signalling and load in the "old" network.

Additionally, a new flag can be introduced in the SLF and/or the HSS to indicate whether the user is allowed or not to register a public user identity. I.e., when an identity is moved from old operator to new operator, the moved identity can only be registered to the network of the new operator and it is not allowed to register it anymore to the network of the old operator.. The new thing is that this information can be given to the device. Thus, an identity is not barred for all com- munication. Rather, the identity can be used to make and receive calls.

Fig. 2 shows a schematic messaging diagram which indicates message flows and a processing step between/at respective network elements in case of a portability of a public user identity of a subscriber (e.g. Alice) between a first network of a first network operator NO1 (e.g. IMS operator Telia) and a second network of a second network operator NO2 (e.g. IMS operator Elisa).

Initially, Alice's network operator NO1 is Telia and Alice's public user identity is sip:alice@telia.se.

Then, Alice decides to switch her network operator. She chooses as her new IMS provider a new network operator NO2 which is Elisa. The new network operator Elisa assigns a new address (or public user identity) sip:alice@elisa.fi to Alice. However, Alice wants to keep the old address (or public user identity) as well, so that she can continue to receive all calls and sessions to her old address sip:alice@telia.se. The two network operators Telia and Elisa have made an agreement to implement the proposed name portability solution according to the preferred embodiment.

To achieve this, the first network operator Telia configures the HSS/SLF_NOi 20 of his network so that registration of the old address sip:alice@telia.se is disabled and the old address cannot be registered anymore. Nevertheless, if an LIR message is received for the old address sip:alice@telia.se, the HSS/SLF_NOi 20 of the network of the first network operator sends an LIA response with the address of the I-CSCF_NO2 30 of the network of the new or second network operator Elisa. The network operator Elisa and the subscriber Alice have configured Alice's subscription in the HSS/SLFNO240 of Elisa's network so that whenever Alice register's sip:alice@elisa.fi her old address sip:alice@telia.se is registered implicitly. If LIR is received for sip:alice@telia.se the HSS/SLF_No₂ 40 sends back an LIA response with the address of the S-CSCFN_O2 50 of the Elisa's network, that has been allocated to her.

Referring to Fig. 2, a partial message sequence is shown for a case where a calling party, e.g. Bob, tries to call Alice's old address sip:alice@telia.se.

In step 1 , the SIP-request with Alice's old address URI_NOi is routed normally based on the telia.se domain in the URI_Noi to the l-CSCF_NOi 10 of the network of the first network operator Telia., The l-CSCF_Noi 10 sends an LIR with Alice's old address URI_NOi (sip:alice@telia.se) to Telia's HSS/SLF_NOi 20 (step 2). Then, in step 3, the HSS/SLF_NOi 20 retrieves the SIP-URI of the second network operator's (Elisa's) I-CSCFN_O230 and answers in step 4 with an LIA response where the Server-Name AVP contains the URI of the I-CSCF_NO2 30, e.g. sip:i-cscf.elisa.fi.

In step 5, the l-CSCF_Noi 10 forwards the SIP-request to Elisa's I-CSCF_NO2 30 which sends an LIR message with the old address sip:alice@telia.se of the SIP- request in step 6 to Elisa's HSS/SLF_N0240. The HSS/SLF_No240 of the network of the second network operator Elisa answers in step 7 with an LIA response where the Server-Name AVP code contains the SIP-URI of Elisa's S-CSCF_N02 50. Finally, in step 8, Elisa's I-CSCF_NO2 30 forwards the SIP-request to Elisa's S-CSCFNO2 50. After that, normal session termination applies.

If Alice does not want to use the address sip:alice@elisa.fi at all, it can be configured as barred identity that is used only for registration purposes.

In the following, modified processing flows at the HSS/SLFNOI 20 and the HSS/SLF_No₂40 are described with reference to Figs. 3 and 4. In both cases, the modified processing may alternatively be implemented in the HSS or the SLF

Fig. 3 shows a schematic flow diagram of a portability-related processing at the "old" network operator's HSS/SLFNOI 20 according to the preferred embodi- ment. When the HSS/SLF_Noi 20 receives an LIR message with an oid address URINOI which has been replaced by a new address URI_N02 of a new network operator, retrieves the address of the I-CSCF_NO2 30 of the network of the new network operator (step S101). Then, it creates an LIA response message con- taining the address of the l-CSCF_No2 30 (step S102). Thereafter, the

HSS/SLFNOI 20 sends the created LIA message in step S 103 as a response to the received LIR message. Thereby, portability of old addresses to the network of the new network operator is achieved by routing corresponding messages to the correct entry point network element of the network of the new network op- erator.

Fig. 4 shows.a schematic flow diagram of a portability-related processing at the new network operator's HSS/SLFN_O240 according to the preferred embodiment. When the HSS/SLFNO2 40 receives an LIR message with an old address URI_Noi of the old network operator, it retrieves a corresponding address of the S- CSCFNO2 50 of the network of the new network operator (step S201). Then, it creates an LIA response message containing the address of the S-CSCFN_C>2 50 (step S202). Thereafter, the HSS/SLF_N0240 sends the created LIA message in step S203 as a response to the received LIR message.

Thereby, portability of old addresses to the network of the new network operator is achieved by routing corresponding messages based on the old address within the network of the new network operator to the correct serving network element of the subscriber.

To generalize the above preferred embodiment, instead of returning the S- CSCF capabilities or S-CSCF name of the user in the LIA message the SLF/HSS of the old network operator may return the address of an entry point network element of the new network operator. The address of the entry point network element of the new network operator can be for example an I-CSCF address or IBCF (Interconnection Border Control Function) address of the new network operator. The entry point network element may also be some other kind of SIP proxy. The proposed solution is thus in no way considered limited to an I-CSCF only.

Although in the implementation of the above preferred embodiment the address of the entry point network element of the new operator is transferred in the Server-Name AVP of the LIA message, it can be transferred also in some other AVP. For example, a new I-CSCF-Name AVP or a IBCF-Name AVP could be defined.

Although the solution according to the above preferred embodiment does not necessarily require any changes to the I-CSCF of the old network operator, the preferred embodiment may optionally be modified so that the HSS/SLF of the old network operator indicate in the LIA message to the I-CSCF of the old network operator that the subscriber's name and/or number (e.g. user ID) is ported to the new network. This indication could be for example a new result-code. For example "DIAMETER_SUCCESS_PORTED_USER". Another implementation option would be to define a new AVP for the indication. The name of the new AVP could be for example "Portability-Indication". As another option, the AVP could be of type "Enumerated", where an Enumeration value "PORTEDJJSER (1)" could indicate that the user is served by a new network operator. The benefit of indicating the ported user to entry point network element (e.g. I-CSCF) of the old network operator could be for example that the I-CSCF is able to collect statistics about the ported users and it could be also used for charging purposes.

However, it is noted that the present invention is not restricted in a sense that the LIA/LIR related functionalities or functions are tight to the network of the old operator who originally owned the ported identity (i.e., at least one of the name and the number). That is, it is not necessary or essential that the "first" network must be the network who owns the old identity, meaning that the solution also applies to cases where the originating network makes a query to the database.

As an example, Alice may have had a subscription from operator A (identity: alice@operatorA.com) and she moves to operator B, while she still can use the old identity. In the above exemplary case, Bob calls Alice and the call is routed from Bob's network to operator A which applies the proposed solution and the call is then routed to operator B. The present invention is intended to also cover the case where Bob's network applies the proposed solution (acts as "first" network) and directly routes the call to operator B without involving operator A.

In summary, a method and network elements for providing portability of at least one of a name and a number of a subscriber between a first network and a sec- ond network have been described, wherein a first network element is configured to respond to a location information request, which comprises at least one of the name and the number of the subscriber in the first network, with an answer indicating an address of an entry point network element of the second network, and a second network element is configured to respond to a location information request, which comprises the at least one of the name and the number of the subscriber in the first network, with an answer indicating an address of a serving network element of the second network. Thereby, a distributed architecture for portability can be implemented in a simple manner involving minimum network changes.

Although the above preferred embodiment has been described in connection with an IMS environment, the present invention can be applied to other networks, as well. As an example, the proposed solution can be applied to Euro- pean Telecommunications Standards Institute (ETSI) Telecommunications and Internet converged Services and Protocols for Advanced Networks (TISPAN) Next Generation Networks (NGN) architecture. Moreover, the present invention can be applied to any portability of any kind of numbers or names, which are used for addressing or identifying subscribers. For example, it can be applied to TEL-URI and SIP-URI type of addresses that contain phone numbers. The modified processing at the HSS or SLF can be performed in any network element with an address resolution, translation or storing function, provided in other network environments. As a further option, the proposed solution may be applied to a case where portability is used also with registrations. In that case, the SLF/HSS needs to send the entry-point address also in the User- Authorization-Answer (UAA) message for a ported user. The UAA is the answer to User-Authorization-Request (UAR).The preferred embodiments my thus vary within the scope of the attached claims.

Claims

1. A method of providing portability of at least one of a name and a number of a subscriber between a first network and a second network, said method comprising the steps of:

a) configuring a first network element to respond to a location information request, which comprises at least one of said name or said number of said subscriber in said first network, with an answer indicating an address of an entry point network element of said second network; and

b) configuring a second network element to respond to a location information request, which comprises said at least one of said name and said number of said subscriber in said first network, with an answer indicating an address of a serving network element of said second network.

2. A method according to claim 1 , further comprising disabling registration of said at least one of said name and said number of said subscriber in said first network.

3. A method according to claim 2, wherein said disabling is performed by setting a predetermined flag.

4. A method according to any one of the preceding claims, wherein said at least one of the name and the number previously used in said first network may be registered by an implicit registration to said second network..

5. A method according to any one of the preceding claims, further comprising the step of implicitly registering said at least one of said name and said number of said subscriber in said second network, when at least one of a new name and a new number of said subscriber is registered in said second network.

6. A method according to any one of the preceding claims, further comprising the step of setting a flag in at least one of said first and second network elements to indicate whether said subscriber is allowed or not to register at least one of a predetermined name and a predetermined number.

7. A method according to any one of the preceding claims, wherein said at least one of said name and said number comprises a Uniform Resource Identifier.

8. A method according to any one of the preceding claims, wherein said first and second network elements are home subscriber servers or a network elements having an address resolution mechanism.

9. A method according to any one of the preceding claims, wherein said first network is an Internet Protocol Multimedia Subsystem (IMS) of a first IMS operator and said entry point network element comprises an interrogating call session control function, and said second network is an Internet Protocol Multimedia Subsystem (IMS) of a second IMS operator and said serving network element comprises a serving call session control function.

10. A method according to any one of the preceding claims, further comprising the step of configuring said first network element to add to said an- swer an indication that said at least one of said name and said number of said subscriber is ported to said second network.

11. A method according to claim 10, wherein said indication is a result code or an attribute value pair (AVP).

12. A network element for providing portability of at least one of a name and a number of a subscriber between a first network and a second network, said network element being part of said first network and being adapted to respond to a location information request, which comprises at least one of said name and said number of said subscriber in said first network, with an answer indicating an address of an entry point network element of said second network.

13. A network element according to claim 12, wherein said network element is adapted to to add to said answer an indication that said at least one of said name and said number of said subscriber is ported to said second network.

14. A network element according to claim 12 or 13, wherein said indication is a result code or an attribute value pair (AVP).

15. A network element according to any one of claims 12 to 14, wherein said network element is a home subscriber server or a network element with an address resolution mechanism.

16. A network element for providing portability of at least one of a name and a number of a subscriber between a first network and a second network, said network element being part of said second network and being adapted to respond to a location information request, which comprises said at least one of said name and said number of said subscriber in said first network, with an answer indicating an address of a serving network element of said second network.

17. A network element according to claim 16, wherein said network element is a home subscriber server or a network element with an address resolution mechanism.

18. A system for providing portability of at least one of a name and a number of a subscriber between a first network and a second network, said system comprising a first network element according to claim 12 and a second network element according to claim 16.