GB2404302A - Telephone number translation - Google Patents

Abstract

Number translation from non-geographic to geographic telephone numbers is performed on incoming calls by a platform 3 in a PSTN, and the calls are provided with a signature indicating that translation has taken place, in the signalling information. Received calls are checked for the presence of a signature in the signalling information by a signature verification platform 4. Received calls without a signature indicate that such calls have been dialled direct without number translation and so can be rejected. The signature can be encrypted. Suitable for detection of toll/charge fraud in premium rate service calls.

Description

TELECOMMUNICATIONS SERVICES APPARATUS AND METHODS

This invention concerns the field of telecommunications and in particular relates to telecommunications services apparatus and methods, such as in the context of the provision of premium rate telephony services.

It is common for telephone networks to support a range of tariffs for telephony services. These tariffs are also commonly regulated by an official regulator for the territory. Some of the higher tariff bends are collectively known as premium rates, and the telephony services that utilise these tariffs are known as premium rate services.

Premium rates can typically apply not only to voice calls but also to text messages and other types of data traffic. Charging may be call- duration based, a one-off charge (a drop charge') for a message or vote for example, or at the start of a voice call, or a combination of these. In some territories, the numbering plan is used to distinguish different charging bands andlor types of service to help consumers.

Premium rate services for voice are typically provided using Customer Premises Equipments (CPE) operated by a Service Provider (SP) who is independent from the telephone network, although in some cases the operator may offer their own in-house services. The commercial incentive for operators and SPs to offer these services is normally a revenue share. A portion of the call charge paid by the end customer goes to the SP, while the remainder goes to the operator and to cover any inter-operator transit costs. With some premium rate services being very expensive, the potential for making money has assured the growth of such services in many countries, subject to control by the official regulator.

Premium rate services typically require the use of 'non-geographic' telephone numbers or short codes for dialling the service. This makes billing easier, as the tariff can be determined from the number dialled. In most cases, the non-geographic number is translated by the network into a geographic number, routed over the network using standard routing techniques for geographic numbers, and delivered to the CPE at the service provider's premises.

The problem with this technique is that, if a caller can find out the geographic number for a service, he is able to dial that number directly as a normal geographic call, and avoid paying the premium rate that is associated with the non-geographic number.

While non-geographic numbering is also used for freephone (or toll-free) services and by companies who wish to offer a single number at either a local or national rate, these services do not suffer from the same problem. This is because there is no premium rate I charge to be avoided, and so there is no incentive for a caller to attempt to bypass the advertised number by directly calling the geographic number to which it translates.

An alternative technique used by some operators is to implement an overlay network for premium rate calls. The routing in the overlay network is programmed to deliver premium rate traffic to the correct service provider without passing over the PSTN, so there is no opportunity for users to bypass the premium charges.

However the problem with this second technique is that, apart from the complexity of implementing an overlay network, the Customer Premises Equipment of the service provider has to be directly connected into the overlay network, e.g. by ISDN leased line. The public switched telephone network (PSTN) cannot be used, otherwise number translation is required which gives rise to the first problem mentioned above.

As the overlay network is likely to be only implemented as a small number of nodes in key population centres for cost reasons, it follows that service providers must also be located close to these population centres. If a service provider is located far from one of the overlay network nodes, then the leased line charges required to connect may make the business model uneconomic, or at least severely reduce the available revenues.

Service providers are therefore effectively precluded from setting up businesses anywhere other than close to the overlay network nodes.

According to a first aspect of the invention there is provided telecommunications services apparatus for use with a telephone network, the apparatus comprising means for performing number translation on incoming telephone communications from non- geographic telephone numbers to geographic telephone numbers, and means for providing a telephone communication with a signature indicating that the telephone number has been translated.

According to a second aspect of the invention there is provided telecommunications services apparatus for use with a telephone network, the apparatus comprising means for receiving telephone communications from the telephone network, means for I determining whether a received telephone communication has a signature, and means for rejecting a telephone communication that has been dialled direct without translation and thereby lacking a signature.

According to a third aspect of the invention there is provided a telecommunications services method for use with a telephone network, the method comprising performing number translation on incoming telephone communications from non-geographic telephone numbers to geographic telephone numbers, and providing a telephone communication with a signature indicating that the telephone number has been translated.

According to a fourth aspect of the invention there is provided a telecommunications services method for use with a telephone network, the method comprising receiving telephone communications from the telephone network, determining whether a received telephone communication has a signature, and rejecting a telephone communication that has been dialled direct without translation and thereby lacking a signature.

The signature adding and signature detecting techniques may be provided in combination.

Further aspects of the invention provide a computer program for carrying out the above method(s), and a storage medium on which such computer program is stored.

The invention will now be described by way of example with reference to the accompanying single figure drawing which shows a block diagram of telecommunications services apparatus according to an embodiment of the invention.

Referring to the drawing, a caller 1 to a non-geographic number (e.g. premium rate) ; calls from any part of an operator's territory, and is connected through the PSTN via one or more switches 2. His call is delivered to a number translation and signature platform 3, which translates the dialled number to a geographic number corresponding to the service provider associated with the dialled number. The platform 3 also adds a signature to the signalling information to indicate that the number has been translated from a non-geographic number. The call may then either be tromboned through the number translation and signature platform 3, or may use an IN (intelligent network) I technique whereby one of the switches 2 queries the number translation and signature platform 3, and performs the necessary signalling changes according to the response.

The call is then delivered via one or more of the switches 2 to the customer's premises where it passes through a signature verification platform 4. This checks that the number has been properly translated and not dialled direct, by detection and verification of the signature in the signalling information. If this check is successful then the call is passed to the customer premises equipment (CPE) 5. Alternatively, the call and the result of the check may be passed to the CPE 5.

In a typical overlay network for handling premium rate traffic, the service providers (SPs) connect directly into nodes attached to the overlay network, and not to the PSTN. These nodes may provide protocol translation features, for example so that the SPs can connect using ISDN rather than an SS7 signalling scheme, and may also provide other features such as malicious call tracing and blocking. Traffic dialled using a non-geographic premium rate number is typically network-routed to one of these nodes by an address prefix added by the caller's local exchange.

In the present technique, the same architecture is appropriate, but with some enhancements. The call is still routed to a first platform, such as the number translation and signature platform 3, for example by means of a network routing prefix added by the caller's local exchange. This routing may take place over an overlay network if one exists, or over the main network. The first platform removes the prefix, provides non- geographic to geographic number translation and also adds a signature as a security measure, which is described in more detail below. The call is then routed over the PSTN to the service provider, using normal geographic call routing, which allows the SP to be anywhere in the territory, not just close to certain population centres.

The call is received at the SP's premises by a second platform, such as the signature verification platform 4, which checks the signalling information for the presence of the correct security signature added by the first platform. If the signature is not validated, then the call may be rejected. The signature may be encrypted to make it difficult for direct access to the non-geographic number to be achieved with a spoof signature.

Since the interface from the network, via the PSTN, to the customer premises is most likely to be ISDN, it is appropriate to choose an ISDN signalling parameter to carry the signature. There are many candidate methods of providing such signature transport.

For example the following fields are typically available in an ISDN call set-up message: Information element Direction Protocol discriminator Both Call reference Both Message type Both Sending complete Both dearer capability Both Channel identification Both regress indicator Both Network specific facilities Both Jisplay n u Keypad facility u n Calling party number Both Calling party sub address Both Called party number Both Called party sub address Both Redirecting number n u transit network selection u n Low layer compatibility Both High layer compatibility Both Jeer to User signalling n u The redirecting number could be used, but if the call is diverted en-route to the SP, then the network could overwrite this. A good candidate is user-to-user signalling, which may not be modified by the network, although other methods could be used.

The signature itself could take many forms, and should preferably be specified to be difficult to spoof. A simple encryption of the A party number and a predefined key number (possibly also including a numeric representation of the date) would be adequate. The second platform would implement the same algorithm and check that the result matched the received key. Near a date boundary, the second platform would preferably accept encryptions with either date. The encryption could be as simple as module N addition, where N is a large integer.

For example:

A party number: 01489760000 Fixed Key: 7849382089 Date (days since 1970) : 12283 Signature (sum module 93472971): 85330243 More complex encryptions could be used.

If physical secrecy can be assured, then encryption could be dispensed with in favour of a fixed signature, since the signature is not visible anywhere other than at the receiving equipment.

It would be advantageous if the first platform also logged traffic that was successfully translated and routed. This would then provide the possibility of checking SP records against the logs to ensure that no unexpected traffic was bypassing the signature validation.

The second platform may be implemented as a software modification to existing Customer Premises Equipment, reducing the cost of implementation.

The first platform may be implemented as a software modification to existing overlay network nodes, in networks that already have an overlay network for handling non- geographic or premium rate traffic.

Even if the caller is unable to avoid a premium rate service charge by dialling a geographic number, there is a fraud window in relation to other licensed operators (OLOs). Being a network operator, an OLO has full access to signalling information and can perform translation on numbers before passing them across the interconnect to another operator to which an SP is connected. If the signature scheme used in implementing this technique is as simple as inserting, say, a fixed value into the redirected number field, then the OLO would be able to spoof this operation, and could then route a call directly to the geographic number of a service, inserting the fixed value as required and defeating the security.

For example, if the security measure consisted of putting a prefix on the A number (caller CLI), this would be adequate to prevent callers from directly dialling the geographic number for the service because the A number is checked by the network so that invalid CLIs cannot be provided from the edge of a network. However, at an OLO interconnect, an unscrupulous OLO would be able to prefix the CLI, and then route the call over the interconnect as a PSTN call direct to the geographic number of the service, avoiding premium rate charging. In this case the security measure is inadequate unless the receiving interconnect switches do some validation on the CLI presented, thereby allowing the network to reject manipulated CLIs from the OLO. On the other hand, if CLIs are validated to some level at the interconnect, then CLI prefixing, or alternatively swapping A and B numbers, provides a simple way to implement the necessary signature protocol between the first and second platforms.

In so far as the embodiment(s) of the invention described above may be implemented, at least in part, using software controlled processing apparatus, it will be appreciated that a computer program providing such software control and a storage medium by which such a computer program is stored are envisaged as aspects of the invention.

Claims (22)

1. Telecommunications services apparatus for use with a telephone network, the apparatus comprising means for performing number translation on incoming telephone communications from non-geographic telephone numbers to geographic telephone numbers, and means for providing a telephone I communication with a signature indicating that the telephone number has been I translated.

2. Telecommunications services apparatus for use with a telephone network, the apparatus comprising means for receiving telephone communications from the telephone network, means for determining whether a received telephone communication has a signature, and means for rejecting a telephone communication that has been dialled direct without translation and thereby lacking a signature.

3. In combination, apparatus according to claim 1 and apparatus according to claim 2.

4. Apparatus according to claim 1, claim 2 or claim 3, wherein the signature is carried by an ISDN signalling parameter.

5. Apparatus according to any one of the preceding claims, including encryption I means for encrypting the signature according to an encryption scheme.

6. Apparatus according to claim 5, wherein the encryption scheme is based on the telephone number of the calling party and a predefined key number.

7. Apparatus according to claim 6, wherein the encryption scheme is further based on a numeric representation of the date.

8. Apparatus according to claim 5, claim 6 or claim 7, wherein the encryption scheme is based on module N addition.

9. Apparatus according to any one of the preceding claims, including means for logging telephone communications that have been successfully translated and ' routed. I

10. Telecommunications services apparatus substantially as herein described with reference to and as illustrated in the accompanying drawing.

11. A telecommunications services method for use with a telephone network, the method comprising performing number translation on incoming telephone communications from non-geographic telephone numbers to geographic telephone numbers, and providing a telephone communication with a signature indicating that the telephone number has been translated.

12. A telecommunications services method for use with a telephone network, the method comprising receiving telephone communications from the telephone network, determining whether a received telephone communication has a signature, and rejecting a telephone communication that has been dialled direct without translation and thereby lacking a signature.

1 3. In combination, a method according to claim 11 and a method according to I claim 12.

14. A method according to claim 11, claim 12 or claim 13, wherein the signature is carried by an ISDN signalling parameter.

15. A method according to any one of claims 11 to 14, including encrypting the signature according to an encryption scheme. 1 '

16. A method according to claim 15, wherein the encryption scheme is based on the telephone number of the calling party and a predefined key number.

17. A method according to claim 16, wherein the encryption scheme is further based on a numeric representation of the date.

18. A method according to claim 15, claim 16 or claim 17, wherein the encryption scheme is based on module N addition.

19. A method according to any one of claims 11 to 18, including logging telephone communications that have been successfully translated and routed.

20. A telecommunications services method substantially as herein described with reference to and as illustrated in the accompanying drawing.

21. A computer program for implementing a method according to any one of claims 11 to 20.

22. A storage medium storing a computer program according to claim 21.