WO2008095536A1 - Method and apparatus for use in a communications network - Google Patents

A method is disclosed for use in a telecommunications network. The method comprises using a Session Initiation Protocol, SIP, message comprising number information at least partly identifying a resource using a telephone number. The number information comprises a local number, context information associated with the local number, and a normalised number derived from the local number and its associated context information. The normalised number may be a global number. The number information may instead comprise a local number, context information associated with the local number, and a global number, which may or may not be a normalised number derived from the local number and its associated context information.

TITLE OF THE INVENTION

Method and Apparatus for use in a Communications Network

BACKGROUND OF THE INVENTION 1. Field of the Invention

The present invention relates to a method and apparatus for use in a communications network, for example a Universal Mobile Telecommunications System having an IP Multimedia Subsystem.

2. Description of the Related Art

IP Multimedia services provide a dynamic combination of voice, video, messaging, data, etc. within the same session. By growing the number of basic applications and the media which it is possible to combine, the number of services offered to the end users will grow, and the inter-personal communication experience will be enriched. This will lead to a new generation of personalised, rich multimedia communication services, including so-called "combinational IP Multimedia" services.

The UMTS (Universal Mobile Telecommunications System) is a third generation wireless system designed to provide higher data rates and enhanced services to subscribers. UMTS is a successor to the Global System for Mobile Communications (GSM), with an important evolutionary step between GSM and UMTS being the General Packet Radio Service (GPRS). GPRS introduces packet switching into the GSM core network and allows direct access to packet data networks (PDNs). This enables high-data rate packets switch transmissions well beyond the 64 kbps limit of ISDN through the GSM call network, which is a necessity for UMTS data transmission rates of up to 2 Mbps. UMTS is standardised by the 3^rd Generation Partnership Project (3GPP) which is a conglomeration of regional standards bodies such as the European Telecommunication Standards Institute (ETSI), the Association of Radio Industry Businesses (ARIB) and others. See 3GPP TS 23.002 for more details. The UMTS architecture includes a subsystem known as the IP Multimedia Subsystem (IMS) for supporting traditional telephony as well as new IP multimedia services (3GPP TS 22.228, TS 23.228, TS 24.229, TS 29.228, TS 29.229, TS 29.328 and TS 29.329 Releases 5 to 7). IMS provides key features to enrich the end-user person-to-person communication experience through the use of standardised IMS Service Enablers, which facilitate new rich person-to-person (client-to-client) communication services as well as person-to-content (client-to-server) services over IP -based networks. The IMS is able to connect to both PSTN/ISDN (Public Switched Telephone Network/Integrated Services Digital Network) as well as the Internet.

The IMS makes use of the Session Initiation Protocol (SIP) to set up and control calls or sessions between user terminals (or user terminals and application servers). The Session Description Protocol (SDP), carried by SIP signalling, is used to describe and negotiate the media components of the session. Whilst SIP was created as a user-to- user protocol, IMS allows operators and service providers to control user access to services and to charge users accordingly. The 3GPP has chosen SIP for signalling between a User Equipment (UE) and the IMS as well as between the components within the IMS.

Specific details of the operation of the UMTS communications network and of the various components within such a network can be found from the Technical Specifications for UMTS that are available from http://www.3gpp.org. Further details of the use of SIP within UMTS can be found from the 3GPP Technical Specification TS 24.228 V5.8.0 (2004-03).

Figure 1 of the accompanying drawings illustrates schematically how the IMS fits into the mobile network architecture in the case of a GPRS/PS access network (IMS can of course operate over other access networks). Call/Session Control Functions (CSCFs) operate as SIP proxies within the IMS. The 3GPP architecture defines three types of CSCFs: the Proxy CSCF (P-CSCF) which is the first point of contact within the IMS for a SIP terminal; the Serving CSCF (S-CSCF) which provides services to the user that the user is subscribed to; and the Interrogating CSCF (I-CSCF) whose role is to identify the correct S-CSCF and to forward to that S-CSCF a request received from a SIP terminal via a P-CSCF.

A user registers with the IMS using the specified SIP REGISTER method. This is a mechanism for attaching to the IMS and announcing to the IMS the address at which a SIP user identity can be reached. In 3GPP, when a SIP terminal performs a registration, the IMS authenticates the user, and allocates a S-CSCF to that user from the set of available S-CSCFs. Whilst the criteria for allocating S-CSCFs is not specified by 3GPP, these may include load sharing and service requirements. It is noted that the allocation of an S-CSCF is key to controlling (and charging for) user access to IMS- based services. Operators may provide a mechanism for preventing direct user-to-user SIP sessions which would otherwise bypass the S-CSCF.

During the registration process, it is the responsibility of the I-CSCF to select an S- CSCF if a S-CSCF is not already selected. The I-CSCF receives the required S-CSCF capabilities from the home network's Home Subscriber Server (HSS), and selects an appropriate S-CSCF based on the received capabilities. [It is noted that S-CSCF allocation is also carried out for a user by the I-CSCF in the case where the user is called by another party, and the user is not currently allocated an S-CSCF.] When a registered user subsequently sends a session request to the IMS, the P-CSCF is able to forward the request to the selected S-CSCF based on information received from the S-

CSCF during the registration process.

Within the IMS service network, Application Servers (ASs) are provided for implementing IMS service functionality. Application Servers provide services to end- users in an IMS system, and may be connected either as end-points over the 3GPP defined Mr interface, or "linked in" by an S-CSCF over the 3GPP defined ISC interface. In the latter case, Initial Filter Criteria (IFC) are used by an S-CSCF to determine which Applications Servers should be "linked in" during a SIP Session establishment. Different IFCs may be applied to different call cases. The IFCs are received by the S- CSCF from an HSS during the IMS registration procedure as part of a user's User Profile. Certain Application Servers will perform actions dependent upon subscriber identities (either the called or calling subscriber, whichever is "owned" by the network controlling the Application Server). For example, in the case of call forwarding, the appropriate (terminating) application server will determine the new terminating party to which a call to a given subscriber will be forwarded. In the case that an IFC indicates that a SIP message received at the S-CSCF should be forwarded to a particular SIP AS, that AS is added into the message path. Once the SIP message is returned by the AS to the S-CSCF, it is forwarded on towards its final destination, or forwarded to another AS if this is indicated in the IFCs.

Telephone numbers are carried in SIP -based networks (such as IMS) in TEL URI (Uniform Resource Identifier), SIP URI, and SIPS URI formats, as defined in RFC 3966 and RFC 3261.

In addition to globally-unique telephone numbers, these formats also allow for a local phone number to be carried, but require that a phone context accompanies the local number. The phone context is a prerequisite for the SIP network nodes to be able to identify unambiguously the entity addressed by the local number.

To be able to perform their routing, service delivery and other functions, SIP network nodes perform number normalisation of the local numbers. The number normalisation function turns the local number based on its context into a normalised number, which is typically a globally-unique E.164 telephone number.

In some cases, a SIP network node that is able to normalise the local number may replace the local number with the normalised number before forwarding it, without preserving the local number and its context information.

In other cases, a SIP network node may normalise the local number in order to perform some logic, but may forward the local number and its context unchanged, making it necessary for the downstream nodes to normalise the number again.

As appreciated by the applicant, a potential problem in the case where a SIP network node replaces the local number with the normalised number is that a downstream SIP network node may require the actual local number information to perform its logic. As also appreciated by the applicant, a potential problem in the case where a SIP network node with number normalisation function does normalise the local number but does not forward it, a downstream SIP network node without that function may be unable to perform its functions if it relies on normalised numbers and does not itself have access to a number normalisation function.

It is desirable to address at least some of the above-identified issues.

SUMMARY OF THE INVENTION

According to a first aspect of the present invention there is provided a method for use in a telecommunications network, the method comprising using a Session Initiation Protocol, SIP, message comprising number information at least partly identifying a resource using a telephone number, characterised in that the number information comprises a local number, context information associated with the local number, and a normalised number derived from the local number and its associated context information.

Using the SIP message may comprise providing at least one of the local and normalised numbers in the message.

Using the SIP message may comprise providing the normalised number in the message.

The method may comprise deriving the normalised number from the local number.

Using the SIP message may comprise removing at least one of the local and normalised numbers from the message.

Using the SIP message may comprise removing the local number from the message.

Using the SIP message may comprise sending the SIP message.

Using the SIP message may comprise receiving the SIP message. Using the SIP message may comprise producing the SIP message.

Using the SIP message may comprise modifying the SIP message.

The SIP message may be a SIP request.

The local number and the normalised number may be provided in a first portion of the message.

One of the local number and the normalised number may be provided in a first portion of the message and the other of the local number and the normalised number may be provided in a second portion of the message, different to the first portion of the message.

For at least one SIP message used in the method, the first portion may be a SIP Uniform Resource Identifier portion.

For at least one SIP message used in the method, the first portion may be a SIPS URI portion.

For at least one SIP message used in the method, the first portion may be a telephone Uniform Resource Identifier portion.

The context information associated with the local number may comprise at least one of a domain context and a global number context.

The normalised number may be a global number.

The message may comprise context information associated with the normalised number.

The network may be a Universal Mobile Telecommunications System comprising an IP Multimedia Subsystem.

The method may be performed in a Breakout Gateway Control Function of the network. The method may be performed in a Serving Call Session Control Function of the network.

According to a second aspect of the present invention there is provided a method for use in a telecommunications network, the method comprising using a Session Initiation Protocol, SIP, message comprising number information at least partly identifying a resource using a telephone number, characterised in that the number information comprises a local number, context information associated with the local number, and a global number

The global number may be derived from the local number and its associated context information.

The global number may comprise a normalised number derived from the local number and its associated context information.

According to a third aspect of the present invention there is provided an apparatus for use in a telecommunications network, the apparatus comprising means for using a Session Initiation Protocol, SIP, message comprising number information at least partly identifying a resource using a telephone number, characterised in that the number information comprises a local number, context information associated with the local number, and a normalised number derived from the local number and its associated context information.

According to a fourth aspect of the present invention there is provided an apparatus for use in a telecommunications network, the apparatus comprising means for using a Session Initiation Protocol, SIP, message comprising number information at least partly identifying a resource using a telephone number, characterised in that the number information comprises a local number, context information associated with the local number, and a global number.

According to a fifth aspect of the present invention there is provided a Session Initiation Protocol, SIP, message comprising number information at least partly identifying a resource using a telephone number, characterised in that the number information comprises a local number, context information associated with the local number, and a normalised number derived from the local number and its associated context information.

According to a sixth aspect of the present invention there is provided a Session Initiation Protocol, SIP, message comprising number information at least partly identifying a resource using a telephone number, characterised in that the number information comprises a local number, context information associated with the local number, and a global number.

According to a seventh aspect of the present invention there is provided a signal comprising a SIP message comprising number information at least partly identifying a resource using a telephone number, characterised in that the number information comprises a local number, context information associated with the local number, and a normalised number derived from the local number and its associated context information.

According to an eighth aspect of the present invention there is provided a signal comprising a SIP message comprising number information at least partly identifying a resource using a telephone number, characterised in that the number information comprises a local number, context information associated with the local number, and a global number.

According to a ninth aspect of the present invention there is provided a program for controlling an apparatus to perform a method according to the first or second aspect of the present invention or which, when loaded into an apparatus, causes the apparatus to become an apparatus according to the third or fourth aspect of the present invention. The program may be carried on a carrier medium. The carrier medium may be a storage medium. The carrier medium may be a transmission medium.

According to a tenth aspect of the present invention there is provided an apparatus programmed by a program according to the ninth aspect of the present invention. According to an eleventh aspect of the present invention there is provided a storage medium containing a program according to the ninth aspect of the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1, discussed hereinbefore, illustrates schematically the integration of an IP Multimedia Subsystem into a 3 G mobile communications system;

Figure 2 illustrates a scheme according to an embodiment of the present invention;

Figure 3 illustrates a scheme according to another embodiment of the present invention; and

Figure 4 illustrates a scheme according to an embodiment of the present invention as applied to IMS.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

According to a basic concept underlying an embodiment of the present invention, a SIP network node that performs number normalisation of a local number received in a SIP request preserves both the received local number and its context information, and adds to those the normalised-to number information in the SIP request that it forwards. Such a scheme is illustrated schematically in Figure 2.

The above concept is general and can apply to any local telephone number received in a SIP request. The concept therefore is able to cover cases where the local telephone number is used for any purpose, e.g. to identify a destination, origination or intermediary of the request.

As a complement to the basic concept as expressed above, it is also possible to introduce a mechanism or function for a SIP proxy that has knowledge of both the local telephone number and the normalised telephone number to remove the local telephone number information from the SIP request that it sends out. The decision to remove the local telephone number (referred to as local number policy) may be based on: • The inability of the downstream node or nodes to interpret the local telephone number

• The inability of the downstream node or nodes to receive both the local and normalised telephone numbers

• The downstream node or nodes are not trusted to receive the local telephone number

• The operator's choice to not forward local telephone numbers to other parties, e.g. with which the operator has no agreement

This complementary concept is illustrated schematically in Figure 3. Note that these complementary concepts can be used in combination.

There are at least two possible alternatives to implement the above-mentioned basic concepts:

1. Extend the definitions of TEL URI, SIP URI and SIPS URI to include both the original local telephone number and the normalised number.

2. Define new SIP headers specific to the usage of the telephone number.

Some specific implementation examples will now be provided.

Example implementation Ia

One implementation of the basic idea is to extend the definition of the TEL, SIP and SIPS URIs with the normalised number information. In this example, the normalised number is added to the local number in the definition of TEL (and SIP and SIPS) URI.

The current TEL URI definition (as in RFC 3966) does not allow for addition of the normalised-to number, e.g.: Say a TEL URI is received with a local number: tel:7042;phone-context=example.com when normalised to e.g. +12015550123, it performs some logic, but does not replace the local number, and instead forwards the local number and its context unchanged, resulting in a TEL URI like: tel:7042;phone-context=example.com

With this example implementation, the normalised number is added to the local number information. Using the previous example again:

Say a TEL URI is received with a local number: tel:7042;phone-context=example.com when normalised to e.g. +12015550123, the normalised-to number is added to the TEL URI as a uri parameter: tel:7042;phone-context=example.com;norm=+12015550123

In general the normalised number may also have a phone context and therefore the new format can also allow for that possibility. For example:

Say a local number: tel:7042;phone-context=example.com is normalised to 8631234 in the context of +1914555: tel:7042;phone-context=example.com;norm=8631234;norm- context=+1914555

Note that the parameter names "norm" and "norm-context" are just examples; other parameter names or formats can be used.

Example implementation Ib

Another implementation of the basic idea is to extend the definition of the TEL, SIP and SIPS URIs with the originally dialled number information. In this example, the original local number is added in the definition of TEL (and SIP and SIPS) URI. The current TEL URI definition (as in RFC 3966) does not allow for addition of the originally dialled number, e.g.:

Say a TEL URI is received with a local number: tel:7042;phone-context=example.com when normalised to e.g. +12015550123, it replaces the local number and results in a TEL URI like: tel:+12015550123

With this example implementation, the originally dialled number is added to the normalised number. Using the previous example again:

Say a TEL URI is received with a local number: tel:7042;phone-context=example.com when normalised to e.g. +12015550123, the normalised-to number replaces the originally dialled number but the original local number is added to the TEL URI as a uri parameter: tel: +12015550123 ;local=7042 ;local-context=example.com

In general the normalised number may also have a phone context and therefore the new format can also allow that possibility. For example:

Say a local number: tel:7042;phone-context=example.com is normalised to 8631234 in the context of +1914555: tel:8631234;phone-context=+1914555;local=7042;local- context=example.com

Note that the parameter names "local" and "local-context" are just examples; other parameter names or formats can be used.

Example implementation 2a Other implementation alternatives of the basic concept also exist. For instance new SIP headers specific to the usage of the telephone number may be defined. In this example, the normalised number is added to the request in a new SIP header. For example:

A SIP proxy receives a SIP request with a local number in the Request-URI:

INVITE tel:7042;phone-context=example.com

Which it normalises and forwards the SIP request including a new SIP header representing a normalised-to number of the requested target URI: INVITE tel:7042;phone-context=example.com

Normalized-R-URI:<tel:+12015550123>

Note that the header name "Normalized-R-URI" is just an example; another name or format can be used.

Example implementation 2b

Other implementation alternatives of the basic concept also exist. For instance new SIP headers specific to the usage of the telephone number may be defined. In this example, the original local number is added to the request in a new SIP header. For example:

A SIP proxy receives a SIP request with a local number in the Request-URI: INVITE tel:7042;phone-context=example.com

Which it normalises and forwards the SIP request replacing the Request-URI with the normalised-to number and including a new SIP header representing the original local number from the: INVITE tel:+12015550123 Local-R-URI:<tel:7042;phone-context=example.com>

Note that the header name "Local-R-URI" is just an example; another name or format can be used. An embodiment of the present invention is particularly useful in the context of IMS. This is illustrated schematically in Figure 4. The illustration highlights the advantages of having both the local and normalised-to number transported on the ISC interface, which allows for the number normalisation to be centralised in the S-CSCF without the need for this function in the Application Servers. Figure 4 also shows an example usage of the local number policy in the IMS where the policy is placed in the BGCF (Breakout Gateway Control Function). Note that the number normalisation function and the local number policy function can be placed in other nodes of the IMS architecture.

An embodiment of the present invention has one or both of the following advantages:

1. Local number information is preserved and can be used in downstream nodes to execute local number specific logic.

2. Number normalisation need not be redone in multiple network nodes.

It will be appreciated that operation of one or more of the above-described components can be controlled by a program operating on the device or apparatus. Such an operating program can be stored on a computer-readable medium, or could, for example, be embodied in a signal such as a downloadable data signal provided from an Internet website. The appended claims are to be interpreted as covering an operating program by itself, or as a record on a carrier, or as a signal, or in any other form.

It will also be appreciated by the person of skill in the art that various modifications may be made to the above-described embodiments without departing from the scope of the present invention as defined by the appended claims. In particular, it will be appreciated that, although described in relation to a Universal Mobile Telecommunications System having an IP Multimedia Subsystem, the present invention is also applicable to other types of network.

WHAT IS CLAIMED IS:

1. A method for use in a telecommunications network, the method comprising using a Session Initiation Protocol, SIP, message comprising number information at least partly identifying a resource using a telephone number, characterised in that the number information comprises a local number, context information associated with the local number, and a normalised number derived from the local number and its associated context information.

2. A method as claimed in claim 1, wherein using the SIP message comprises providing at least one of the local and normalised numbers in the message.

3. A method as claimed in claim 2, wherein using the SIP message comprises providing the normalised number in the message.

4. A method as claimed in claim 1, 2 or 3, comprising deriving the normalised number from the local number.

5. A method as claimed in any preceding claim, wherein using the SIP message comprises removing at least one of the local and normalised numbers from the message.

6. A method as claimed in claim 5, wherein using the SIP message comprises removing the local number from the message.

7. A method as claimed in any preceding claim, wherein using the SIP message comprises at least one of sending, receiving, producing, and modifying the SIP message.

8. A method as claimed in any preceding claim, wherein the SIP message is a SIP request.

9. A method as claimed in any preceding claim, wherein the local number and the normalised number are provided in a first portion of the message.

10. A method as claimed in any preceding claim, wherein one of the local number and the normalised number is provided in a first portion of the message and the other of the local number and the normalised number is provided in a second portion of the message, different to the first portion of the message.

11. A method as claimed in claim 9 or 10, wherein the first portion is a SIP Uniform Resource Identifier portion, for at least one SIP message used.

12. A method as claimed in claim 9, 10 or 11, wherein the first portion is a SIPS URI portion, for at least one SIP message used.

13. A method as claimed in any one of claims 9 to 12, wherein the first portion is a telephone Uniform Resource Identifier portion, for at least one SIP message used.

14. A method as claimed in any preceding claim, wherein the context information associated with the local number comprises at least one of a domain context and a global number context.

15. A method as claimed in any preceding claim, wherein the normalised number is a global number.

16. A method as claimed in any preceding claim, wherein the message comprises context information associated with the normalised number.

17. A method as claimed in any preceding claim, wherein the network is a Universal Mobile Telecommunications System comprising an IP Multimedia Subsystem.

18. A method as claimed in claim 17, when dependent on claim 6, comprising performing the method in a Breakout Gateway Control Function of the network.

19. A method as claimed in claim 17 or 18, when dependent on claim 3, comprising performing the method in a Serving Call Session Control Function of the network.

20. A method for use in a telecommunications network, the method comprising using a Session Initiation Protocol, SIP, message comprising number information at least partly identifying a resource using a telephone number, characterised in that the number information comprises a local number, context information associated with the local number, and a global number

21. A method as claimed in claim 20, wherein the global number is derived from the local number and its associated context information.

22. A method as claimed in claim 21, wherein the global number comprises a normalised number derived from the local number and its associated context information.

23. An apparatus for use in a telecommunications network, the apparatus comprising means for using a Session Initiation Protocol, SIP, message comprising number information at least partly identifying a resource using a telephone number, characterised in that the number information comprises a local number, context information associated with the local number, and a normalised number derived from the local number and its associated context information.

24. An apparatus for use in a telecommunications network, the apparatus comprising means for using a Session Initiation Protocol, SIP, message comprising number information at least partly identifying a resource using a telephone number, characterised in that the number information comprises a local number, context information associated with the local number, and a global number.

25. A program for controlling an apparatus to perform a method as claimed in any one of claims 1 to 22.

26. A program which, when loaded into an apparatus, causes the apparatus to become an apparatus as claimed in claim 23 or 24.

27. A program as claimed in claim 25 or 26, carried on a carrier medium.

28. A program as claimed in claim 27, wherein the carrier medium is a storage medium.

29. A program as claimed in claim 27, wherein the carrier medium is a transmission medium.

30. An apparatus programmed by a program as claimed in any one of claims 25 to 29.

31. A storage medium containing a program as claimed in any one of claims 25 to

28.

32. A Session Initiation Protocol, SIP, message comprising number information at least partly identifying a resource using a telephone number, characterised in that the number information comprises a local number, context information associated with the local number, and a normalised number derived from the local number and its associated context information.

33. A Session Initiation Protocol, SIP, message comprising number information at least partly identifying a resource using a telephone number, characterised in that the number information comprises a local number, context information associated with the local number, and a global number.

34. A signal comprising a SIP message comprising number information at least partly identifying a resource using a telephone number, characterised in that the number information comprises a local number, context information associated with the local number, and a normalised number derived from the local number and its associated context information.

35. A signal comprising a SIP message comprising number information at least partly identifying a resource using a telephone number, characterised in that the number information comprises a local number, context information associated with the local number, and a global number.