WO2009036798A1

WO2009036798A1 - Method and device for improving the credibility of a calling line identity

Info

Publication number: WO2009036798A1
Application number: PCT/EP2007/059844
Authority: WO
Inventors: Thomas Korst; Joerg Christian Ewert
Original assignee: Telefonaktiebolaget Lm Ericsson (Publ)
Priority date: 2007-09-18
Filing date: 2007-09-18
Publication date: 2009-03-26

Abstract

A method is described for improving, in a first communication network (106), the credibility of a calling line identity, CLI, (CLI1) associated with a call when receiving a call from another communication network (102). A call reference uniquely identifies a first origin of the call. In the method the call is received from the other communication network (102). The first origin of the call is determined from the call reference. A further origin of the call is determined from the CLI. The first origin is compared with the further origin, and depending on the comparison, a further processing of the CLI is decided. A device and a program embodying the invention are also described.

Description

Title

Method and Device for Improving the Credibility of a Calling Line Identity

Technical field

The present invention generally relates to a method for improving the credibility of the calling line identity in a telecommunication network. A device and a program embodying the invention are also described.

Background

The nodes in a communication network allow the exchange of data with external networks such as the Internet or mobile or fixed networks of other operators. A very big part of the exchanged data is voice, which, during a telephone call, is transported between the calling and the called party. The telephone number of the calling party can be transmitted to the called party's telephone equipment during the ringing signal or when the call is being set up but before the call is answered. This is achieved thanks to a telephony service providing the Calling Line Identity (CLI). The name of the calling party can also appear together with the telephone number. This is made possible either if the number of the calling party is stored together with a name in the called party's telephone equipment or if there is a service allowing a phone number to be sent together with the name to which it associates. This happens often in corporate telephone networks, where a called party can see the number and the name of the calling party.

When a telephone call is set up the CLI has to be transported through the different networks and nodes that handle the call in order to reach the called party. Preferably the subscriber has also constant access to services like the voicemail.

In customary mobile networks, e.g. GSM networks, the mobile subscriber may roam inside or outside the home network. A Home Location Register (HLR) stores information about a node where the subscriber roams at any time. The HLR is a database used to store the subscriber location information and the subscriber related information which is needed to provide telecommunication services. The current location of the subscriber is provided to the HLR from a Mobile Switching Center (MSC). The MSC is a telephone exchange which provides subscriber mobility management, and GSM services, like circuit switched calling, to the mobile phones roaming within an area that it serves. Another database called Visitor Location Register (VLR) stores information about subscribers that are currently served by an associated MSC. Whenever an MSC detects a new mobile phone requiring service, it creates a new record in the associated VLR and updates the HLR with the MSCA/LR address of the subscriber. In this way the HLR is constantly updated of the actual location of the subscriber so that all services depending on the location and identity of the subscriber can function properly.

It has been observed that the CLI shown in the phone display of the called party may not reflect the real identity of the calling party. For example, in some networks, depending on the vendor and the operator settings, subscribers with an integrated services digital network (ISDN) modem could manipulate the CLI sent towards the destination. In Internet Protocol (IP) telephony, the provider may not guarantee the integrity of the CLI since, especially in international calls, IP telephony systems use intermediate telephone numbers. Also, telemarketing organizations often manipulate the CLI. In some instances, this is done to provide a "central number" for consumers to call back or in other cases this is done to prevent being traced. The manipulation of the CLI is also called CLI- spoofing. Such services are also offered from specialized companies, like SPOOFTEL (www.spooflel.com). Customers of such companies have the possibility to change the number which reaches the cellular or land line telephone of the called party, when they make a phone call.

There are also a number of telephony services which are dependent on identification of the subscriber. For example, one way for the subscriber to gain access to a personal voicemail is through identification of the subscriber's CLI. Manipulating the CLI can cause a series of problems when the user needs to be identified in order to gain access to services.

Today the only efficient measure to avoid the problems occurring from manipulation of the CLI is to discard the CLI for calls coming from an untrustworthy source. This, however, also impacts traffic coming from trustworthy sources.

For telephone calls, charging records between the operator and the nodes serving the call are correlated using the Global Call Reference (GCR) (ITU-T Rec. Q.1902.3 (07/2001 ), chapter 6.48). The GCR is created either in the originating telephone exchange or in an exchange receiving a call from a trunk without a GCR. It consists of a network identity, a node identity and a call reference. The network identity specifies the network which generates the call reference, the node identity is a binary number which uniquely identifies within the network, the node which generates the call reference and the call reference identity is a binary number generated by the node for each call. The GCR is generally considered to be reliable and cannot easily be manipulated. Summary

It is an object of the proposed method and devices to improve the credibility of a calling line identity.

According to the invention, the method described in claim 1 is performed. Furthermore, the invention is embodied in a processing device and a program as described in claims 7 and 9. Advantageous embodiments are described in the dependent claims.

By the proposed method, in a first communication network, the credibility of a calling line identity associated with a call received from another communication network is secured. When a call is received from another communication network, a first origin of the call is determined from the call reference and a further origin is determined from the calling line identity. The call reference uniquely identifies the first origin of the call. The two origins are compared and a further processing of the calling line identity is decided, depending on the result of the comparison.

The proposed device processes a call in a communication network. It comprises a receiver unit for receiving a call setup message comprising a calling line identity which determines a calling party. The device also comprises a unit for determining a first origin of the call from the call reference, a unit for determining a further origin of the call from the calling line identity and a controller for comparing the two origins. According to the output from the controller, the call can be further processed.

The proposed method can also be embodied in a software program which can be loaded in the processing system of the proposed device and can be stored on a data carrier or transmitted as a sequence of signals. The proposed method and device make it possible to improve the credibility of a calling line identity and to avoid access to network services, like the personal voicemail, from untrustworthy sources.

The foregoing and other objects, features and advantages of the present invention will become more apparent in the following detailed description of preferred embodiments as illustrated in the accompanying drawings.

Brief description of the drawings

Fig. 1 shows a communication system comprising different networks

Fig. 2 shows a flow chart of an embodiment of the proposed method

Fig. 3 shows a signaling diagram of a call between two networks Fig. 4 shows a device which is adapted to perform the proposed method

Detailed description

Figure 1 shows a simplified representation of a call between two communication networks. A subscriber of network 106 who roams in network 102 makes a call which is transported to the destination network. A call request is sent to an MSC 110 in network 102, which routes the call towards its destination. The MSC creates a call reference GCR1 which, together with the calling line identity CLM , is sent to the destination network. When the call arrives in network 106, it is received by a gateway node 112. The gateway node 112 receives the call reference GCR1 and the calling line identity CLM . The call may reach network 106 through one or more transit networks 104.

The basic concept of improving the credibility of the calling line identity is based on the use of the call reference. A call reference can uniquely identify an origin of a call. A flow diagram of the proposed method of the invention is shown in Figure 2. Upon reception 202 of an initial address message from another communication network, the call reference is checked in a processing step 204 and a first origin of the subscriber is determined. A further origin of the subscriber is determined in a next processing step 206, checking the calling line identity. In the step 208 the two origins determined from the global call reference and from the calling line identity are compared and the further handling of the CLI is decided, for example, whether the calling line identity will be discarded 210 or whether it will be forwarded to a next node 212.

A call reference, as it can be used in the proposed method, can comprise a network identity as well as a node identity. It can be created in the originating exchange, here an MSC 110, or in an exchange receiving a call from a trunk without a call reference. The call reference is considered to be reliable since it is introduced by an operator in the network and it is used to correlate charging records between nodes and operator for calls. If two operators have an agreement to provide the call reference it will be provided with guarantee for each call and it cannot be altered by the subscriber.

In the check of the calling line identity, information about where the subscriber roams and consequently about the location of the subscriber can be fetched from the Home Location Register 108 in the home network of the subscriber. The Home Location Register stores information about the subscriber and gets updates about the location of the subscriber from the mobile switching center which serves the subscriber. An example for a call reference as it is used in the proposed method is the global call reference. The Network ID and Node ID of the global call reference which reach the destination network are compared with the subscriber address in the Home Location Register (HLR). If there is a match between the address in the home location register and the global call reference then the calling line identity is confirmed and it can be forwarded to the destination. In the case that access to a telephony service, for example voicemail, is dependent on the calling line identity, then access to this service can be granted.

There are cases where specific network identities and node identities are in blacklists. A blacklist can be used in an access control mechanism. A blacklist can contain entities which can be denied access to a service or some other privilege. In the case that the network and node ID of the call reference belong to such a blacklist, the CLI is potentially manipulated. In this case a decision about the further processing of the CLI can be taken and the CLI can, for example, be again discarded or an alarm can be issued. If access to a service is dependent on the calling line identity then access to this service can be denied or restricted if the CLI is potentially manipulated.

Figure 3 illustrates a further embodiment and shows a BICC (Bearer Independent Call Control) signaling diagram for getting access to a voicemail service. An Initial Address Message is sent from a Network 302 to a voicemail platform 308 through a gateway node 304 in a destination network, together with a global call reference. Both are received by the voicemail platform which can be configured to perform a check of the global call reference against the calling line identity, against a blacklist, against the location of the subscriber or any combination of such checks. When the calling line identity is not suspected to be manipulated then access to the voicemail is provided 314 and an acknowledgement message ACM 310 is sent to the subscriber together with an answer message ANM 312. If there is no match between the address of the Visiting Location Register and the global call reference then it is possible that the calling line identity has been manipulated. In this case access to the voicemail is denied. Alternatively, the check of the global call reference can be performed in the gateway node 304. If the calling line identity is suspected to be manipulated the gateway node can remove the calling line identity and access to the voicemail is denied.

The invention can be embodied in a processing device which is shown in Figure 4. The device can be adapted to perform the method of the invention. A call setup message which comprises the calling line identity and the call reference is entering a receiver unit 402. The receiver unit 402 is adapted to process the incoming call setup message and forward the call reference and the calling line identity respectively to a first 404 and a second origin determination unit 406. Each origin determination unit derives an origin of the call, from the calling line identity and from the global call reference respectively. The first origin determination unit 404 can exchange information with a register comprising a present location of the subscriber, e.g. an HLR, in order to derive the location of the subscriber from the calling line identity. The output of each origin determination unit is further forwarded to a controller 408 which compares the two locations and generates an output according to the comparison. A call processor 410 receives the output from the controller and further processes the call setup message, according to the output of the controller. For example, if the two locations are the same, the call processor forwards the calling line identity towards the destination. If the two locations are not the same then the call processor can further process the calling line identity for example discarding it or issuing an alarm. Units 404, 406 as well as controller 408 and call processor 410 can be embodied as hardware or as software executed in an operating system of the device. The processing device can be implemented for example in a gateway node. The gateway node can be for example in the home network of the subscriber.

The above embodiments admirably achieve the objects of the invention. However, it will be appreciated that departures can be made by those skilled in the art without departing from the scope of the invention which is limited only by the claims.

Claims

1. A method for improving, in a first communication network (106), the credibility of a calling line identity, CLI, (CLM ) associated with a call, when receiving a call from another communication network (102), wherein a call reference uniquely identifies a first origin of the call, the method comprising the steps of

- receiving the call from the other communication network (102), - determining the first origin of the call from the call reference,

- determining a further origin of the call from the CLI,

- comparing the first origin with the further origin, and

- depending on the comparison, deciding a further processing of the CLI.

2. The method according to claim 1 , wherein a location register (108) is adapted to store subscriber data comprising an indication of a subscriber location and wherein the further origin is determined from said indication.

3. The method according to any preceding claim, wherein, when receiving the call from the other network (102), the call reference is compared with a list of suspicious origins and depending on the comparison a further processing of the CLI is decided.

4. The method according to any preceding claim, wherein the call reference is a global call reference (GCR1 ) indicating an originating node, an originating network and a call reference identity.

5. The method according to any preceding claim, wherein the further processing of the CLI comprises at least one of discarding the CLI and issuing an alarm.

6. The method according to any preceding claim, wherein the further processing of the CLI comprises providing access to a service based on the

CLI.

7. Device for processing a call in a communication network, the device comprising a receiver unit (402) for receiving a call setup message which comprises a Calling Line Identity, CLI, wherein the CLI (CLM ) designates a calling party, characterized in that the device comprises

- a first unit (404) for determining a first origin of the call from a call reference sent in connection with a telephone call, wherein the call reference uniquely identifies the first origin of the call, - a second unit (406) for determining a further origin of the call from the CLI, and

- a controller (408) for comparing the first and the further origin and deciding a further processing of the CLI.

8. Device according to claim 7, adapted to a method according to any of the claims 2 - 6.

9. A program which is adapted to perform a method according to any of the claims 1 - 6.