AU6246300A - Method of supporting the establishment of telephone calls - Google Patents

Description

P/00/011 Regulation 3.2

AUSTRALIA

Patents Act 1990

ORIGINAL

COMPLETE SPECIFICATION STANDARD PATENT Invention Title: Method of supporting the establishment of telephone calls The following statement is a full description of this invention, including the best method of performing it known to us: FHPSYnrD FNATPn32 nlv73707,7 Method of Supporting the Establishment of Telephone Calls Field of the invention This invention relates to a method of supporting the establishment of telephone calls between telephone terminals of a telephone network and IP terminals, to a server for supporting the establishment of such telephone calls, and to a computer product for supporting the establishment of such telephone calls.

Background of the invention The invention starts from the establishment of telephone calls through IP networks as is described, for example, in ITU-T Specification H.323, 2/1998, pages 1 to 2 and .e pages 12 to 34.

An H.323 gateway provides an interface between an IP network and a telephone network. The gateway encodes, compresses, and packetizes voice and video signals from the telephone network, and then transports them as IP packets to a terminal of the IP network or to another H.323 gateway. In the reverse direction, the gateway 20 decodes, decompresses, and disassembles the IP packets coming from a terminal of the IP network or from another H.323 gateway. This makes it possible to establish a telephone call from a conventional telephone terminal of a telephone network through an IP network.

Such a call is commonly set up as follows. The subscriber dials a specific number that is assigned to the H.323 gateway in the telephone network. To the subscriber, this number thus represents the number of a VOIP service provider (VOIP Voice over IP). By voice response, the H.323 gateway then requests the input of the address of the IP terminal to be called. Using this address, the H.323 gateway then initiates the establishment of a corresponding connection through the IP network.

The applicant does not concede that the prior art discussed in the specification forms part of the common general knowledge in the art at the priority date of this application.

Summary of the invention An object of the invention is to speed up the establishment of a telephone call that is partially routed through an IP network.

According to a first aspect of the invention there is provided a method of supporting the establishment of telephone calls between telephone terminals of a telephone :network and IP terminals wherein two or more VOIP service are assigned a subset of "telephone numbers of the telephone network and that the VOIP service providers, in 0% turn, assign numbers of the subset of numbers to IP terminals, so that the respective IP terminal, in addition to being addressable by an IP address assigned to it, can be addressed by this assigned number, that in order to route a call addressed by one of the telephone terminals of the telephone network to a number from the subset of numbers through the telephone network, a server is contacted, that the server determines from the called number of such a specific call which VOIP service S-provider the IP terminal addressed by the called number is associated with, and that 20 the server arranges for the specific call to be routed through the telephone network to a VOIP gateway associated with the VOIP service provider determined.

According to another aspect of the invention there is provided a server for supporting the establishment of telephone calls between telephone terminals of a telephone network and IP terminals of an IP network, wherein the server comprises an interface unit for communication with one or more components of the telephone network. The server further comprises a control unit designed to be triggered for a specific call when the server is contacted via the interface unit by a component of the telephone network which indicates the establishment through the telephone network of a call directed to a number from a subset of numbers which are assigned to two or more VOIP service providers for assignment to IP terminals such that the respective IP terminal, in addition to being addressable by an IP address assigned to this IP terminal, can be addressed by this associated number, and that the control unit is further designed so that when triggered for the specific call, it determines from the called number of the specific call which VOIP service provider the IP terminal addressed by the called number is associated with, and arranges for the specific call to be routed through the telephone network to a VOIP gateway associated with the VOIP service provider determined.

According to a further aspect of the invention there is provided a computer product for supporting the establishment of such telephone calls wherein the computer product is designed to implement, in conjunction with a computer, a control unit which is designed to be triggered for a specific call when contacted by a component of the telephone network which detects the establishment through the telephone *...network of a call directed to a number from a subset of numbers which are assigned to two or more VOIP service providers for assignment to IP terminals such that the 15 respective IP terminal, in addition to be addressable by an IP address assigned to this IP terminal, can be addressed by this assigned number, and that the control unit is further designed so that when triggered for the specific call, it determines from the called number of the specific call which VOIP service provider the IP terminal addressed by the called number is associated with, and arranges for the specific call to 20 be routed through the telephone network to a VOIP gateway associated with the VOIP service provider determined.

o.o.

The idea underlying the invention is to assign a subset of telephone numbers of a telephone network to VOIP service providers that, in turn, can assign these numbers, as an address in addition to the IP address, to IP terminals on their own responsibility.

By numbers from this subset of numbers, IP terminals are now uniquely addressable for VOIP calls within the telephone network. If it is determined during call establishment in the telephone network that a call contains a number from this subset as a destination number, a server will be triggered. This server ensures that the routing of such a VOIP call through the telephone network corresponds with the instantaneous assignment of numbers to IP terminal addresses that was fixed by VOIP service providers. It is also advantageous to allow porting of numbers between numbers from the subset of numbers reserved for IP terminals and numbers from the remaining number space. For such ported numbers, the server must then be triggered as well.

One advantage of the invention is that the conventional two-stage call establishment is replaced by a single-stage call establishment with only one address, whereby the call establishment as a whole is speeded up and becomes more user-friendly.

Another advantage of the invention is that number portability is made possible between IP terminal numbers assigned by different VOIP service providers. Number portability between VOIP network operators and arbitrary fixed network or mobile •radio network operators is also possible. This, on the one hand, decouples the assignment of numbers by the individual VOIP service providers and, on the other hand, makes it easier for IP subscribers to change from one VOIP service provider to another. This leads to an improvement in the competitive conditions between VOIP service providers.

0Wo• Further advantages of the invention are that the routing of a VOIP call is improved 0. both within the telephone network and within the IP network.

Furthermore, the invention can be implemented in existing systems at low cost, and it optimizes the number of database accesses required to translate the address of a VOIP call.

Advantageous developments of the invention are set forth in the subclaims.

Brief description of the drawings The invention will become more apparent by reference to the following description of several embodiments taken in conjunction with the accompanying drawings, in which: Fig. 1 is a block diagram of a communications environment with a server in accordance with the invention; Fig. 2 is a functional diagram of a part of the communications environment of Fig. 1 for a first embodiment; Fig. 3 is a functional diagram of a part of the communications environment of Fig. 1 for a second embodiment; and 10 Fig. 4 is a functional diagram of a part of the communications environment of Fig. 1 for a third embodiment.

Detailed description of the embodiments Fig. 1 shows a communications system with two communications networks 15 TELENET and IPNET, with four terminals TEl to TE4, with a server SERV, with a management unit NM, and with five VOIP gateways GWI to GW5. VOIP gateways GWI to GW5 are connected, on the one hand, to communications network TELENET and, on the other hand, to communications network IPNET, and thus interconnect the communications networks TELENET and IPNET. Terminals TEl and TE2 are connected to communications network TELENET, and terminals TE3 and TE4 are connected to communications network IPNET. Server SERV exchanges data with communications network TELENET and with management unit NM.

Communications network TELENET is a telephone network, such as an integrated services digital network (ISDN) or a public switched telephone network (PSTN).

Communications network TELENET may also be formed by two or more subnetworks that may also be associated with different network operators. Such subnetworks may also be mobile radio networks, such as networks based on the GSM standard (GSM Global System for Mobile Communications). Terminals may thus be connected to communications network TELENET via an analog PSTN line, an ISDN line, or an air interface according to the GSM or DECT standard (DECT Digital European Cordless Telecommunications).

Terminals TEl and TE2 are telephone terminals, for example ISDN telephones or mobile telephones.

Communications network IPNET is an IP network (IP Internet Protocol). It is formed by a data network that uses an IP protocol as Layer 3. Examples of such an IP protocol are the IPv4 or IPv6 protocols.

Communications network IPNET has a number of subnetworks, of which three, IP1 10 to IP3, are shown in Fig. 1 by way of example. Each of subnetworks IP1 to IP3 is a logical subnetwork of an IP service provider. The IP service providers provide the subscribers associated with them access to communications network IPNET.

Furthermore, they make a VOIP service available to all or part of the subscribers associated with them, and thus additionally appear as VOIP service providers OP1, 15 OP2, and OP3, respectively.

It is also possible, of course, that the VOIP service providers OPI, OP2, and OP3 are S00•.* not simultaneously IP service providers, and thus make VOIP services available to arbitrary subscribers of communications network IPNET.

Terminals TE3 and TE4 are IP terminals, such as internet-capable telephones or computers that are equipped with an interface card for communication over communications network IPNET. They are provided with VOIP software, which enables a user to conduct telephone communications over communications network

IPNET.

The number of VOIP gateways GWI to GW5 has been chosen by way of example.

VOIP gateways GWI to GW5 are gateways which allow a telephone call to be established through communications network IPNET. To accomplish this, they perform address translation into an IP address, encoding/decoding, and packet assembly/disassembly of the data stream for transport through communications network IPNET, as well as further functions, such as echo cancellation. Furthermore, they control the establishment of calls through communications network IPNET.

VOIP gateways GW1 to GW5 may be implemented in accordance with ITU-T Recommendation H.323, for example. To perform their functions, they could additionally access a gatekeeper that performs the address translation function centrally for two or more of VOIP gateways GW1 to GW5. The gatekeeper may also be implemented in accordance with ITU-T Recommendation H.323, for example.

10 Each of VOIP gateways GWI to GW5 is associated with a respective one of VOIP service providers OP1, OP2, OP3. VOIP gateways GWI and GW2 are associated with VOIP service provider OP1; VOIP gateways GW3 and GW4 are associated with VOIP service provider OP2; and VOIP gateway GW5 is associated with VOIP service provider OP3. VOIP gateways GW1 to GW5 are preferably addressed via the subnetwork of the VOIP service provider they are associated with. Furthermore, they are preferably operated by the VOIP service provider they are associated with. It is also possible, however, that VOIP gateways GWI to GW5 are operated by another service provider or network operator.

Within communications network TELENET, each of VOIP gateways GW1 to is assigned one range of telephone numbers of communications network TELENET.

Thus, calls through communications network TELENET that are directed to a number from such a number range are automatically routed through communications network TELENET to the respective one of VOIP gateways GWI to GW5 to which this number range is assigned.

Advantageously, two VOIP gateways from different areas of communications network TELENET are assigned the same number range by influencing the routing in communications network TELENET by number translation) by means of server SERV or an IN service of communications network TELENET. This reduces the load and shortens the path length for VOIP calls.

Management unit NM serves to manage numbers assigned to IP terminals for VOIP service providers OP1 to OP3.

Within the number space available in communications network TELENET, VOIP service providers OPI to OP3 are assigned a subset of telephone numbers of communications network TELENET. VOIP service providers OPI to OP3, in turn, assign numbers from the subset of numbers to IP terminals via management unit NM.

Thus, these IP terminals, for instance terminals TE3 and TE4, in addition to being addressable by the IP address assigned to the respective IP terminal, can be addressed 10 by this respective assigned number.

o:oo Furthermore, it is possible to also assign to an IP terminal a number from a portion of the number space that is not assigned to the subset of numbers, in which case this IP terminal, in addition to being addressable by the respective assigned IP address, can be addressed by this respective assigned number. This permits porting of numbers to numbers of the subset of numbers assigned to IP terminals.

Server SERV performs the following functions: ooooo When contacted by a component of communications network TELENET that detects the establishment through the telephone network of a call directed to a number from the above-defined subset of numbers, server SERV is triggered for this specific call.

It is also possible to additionally trigger the server for calls directed to a number whose associated terminal has been ported to a VOIP service provider.

When server SERV has been triggered for a specific call, it determines from the called number which VOIP service provider the IP terminal addressed by the called number is associated with, and arranges for the specific call to be routed through communications network TELENET to a VOIP gateway associated with the VOIP service provider determined.

Server SERV is formed by one or more interconnected processors, on top of which a software platform consisting of, an operating system and a database system is implemented. The software platform and the processors together form a computer SP.

Together with a computer product CP, computer SP performs the above-described functions of server SERV.

Computer product CP is formed by a data carrier and a computer program stored on this data carrier. If this computer program runs on computer SP, then server SERV executes the above-described functions. Server SERV is thus formed by computer CP 10 and this computer program. Computer product CP may also be formed solely by this "computer program as such.

It is also possible to run on computer SP further programs that provide service management functions or service control functions.

The detailed structure of server SERV and the sequence of steps in the method according to the invention will now be explained with reference to Fig. 2.

Fig. 2 shows the communications networks TELENET and IPNET, the server SERV, the management unit NM, the VOIP gateway GWI, and the terminals TEl and TE3.

Communications network TELENET contains one or more specifically designed components, of which three, SWI to SW3, are shown in Fig. 2 by way of example.

These components contact the server SERV when they detect the establishment through communications network TELENET of a call VCON that is directed to a number from the above-described subset of numbers of communications network

TELENET.

The numbers of this subset are assigned to VOIP service providers OP1 to OP3 for assignment to IP terminals in such a way that the respective IP terminal, in addition to being addressable by an IP address assigned to this IP terminal, can be addressed by this assigned number. Each of the numbers occupied in the number space of communications network TELENET by the subset of numbers is assigned to one or more of VOIP gateways GWI to GW5. Thus, all calls that are directed to a number from the subset of numbers address one or more VOIP gateways within communications network TELENET.

Components SWI to SW3 are preferably service switching points (SSPs) according to the IN architecture (IN Intelligent Network) which send a request message to server SERV when the called number contained in a call through communications network TELENET is a number from the above-described subset of numbers.

It is also possible, however, that components SWI to SW3 contact server SERV for each call that is routed through them. Server SERV will then determine from the S"respective called number whether it is to be triggered for the respective call or not.

Components SWI to SW3 may also be service control points (SCPs) according to the IN architecture which send a request message to server SERV on the occurrence of such an event. The determination of this event may be made by the service control point itself if the latter is triggered for all calls, for example. The service control point o*oom may also act only as a mediator between service switching points and server SERV.

From a functional point of view, server SERV comprises an interface unit INTI, a control unit CONTRI, and a database RNDB.

Interface unit INT1 provides for communication with components SWI to SW3 of communications network TELENET. In particular, it provides functions for processing the protocol stacks necessary for this communication.

The communication preferably takes place via the signaling system of communications network TELENET. Interface unit INTI thus comprises functions for processing the protocol stack of Signaling System No. 7 and of the INAP protocol (INAP Intelligent Network Application Part).

It is also possible to transport the INAP protocol between components SWI to SW3 and server SERV via an IP protocol stack. Communication between components SWI to SW3 and server SERV via a software bus, for example in accordance with the Common Object Request Broker Architecture (CORBA), communication which does not require the INAP protocol, is also possible.

Database RNDB serves mainly to translate numbers from the above-described subset of numbers.

10 Advantageously, each of VOIP service providers OP1 to OP3 is permanently "assigned a portion of the above-described subset of telephone numbers, so that the VOIP service provider is addressed directly by the telephone number. Within S•communications network TELENET, the VOIP gateways associated with a particular VOIP service provider are then assigned the numbers from the portion of the subset of numbers which are assigned to the particular VOIP service provider. Thus, within communications network TELENET, all numbers of a portion of the subset of numbers directly address a VOIP gateway associated with the VOIP service provider to which this portion is assigned.

ooooo In database RNDB, first numbers from the range of numbers assigned to a portion of the subset of numbers assigned to a first VOIP service provider are combined with second numbers from the range of numbers assigned to a portion of the subset of numbers of a second VOIP service provider when the IP terminal designated by the called number has been ported from the first to the second VOIP service provider. It is also possible that in database RNDB, first numbers which do not form part of the above-described subset of numbers are combined with numbers assigned to the portion of the subset of numbers of a VOIP service provider when a terminal designated by the respective called number has been ported from a network operator of communications network TELENET to the VOIP service provider.

This combination enables control unit CONTRI to determine the currently correct number of an IP terminal, and thus the currently correct VOIP service provider the IP terminal is associated with.

It is also possible, of course, that in database RNDB, each of the first numbers is associated directly with a code of the VOIP service provider which the IP terminal addressed by the number is currently associated with.

In another preferred embodiment, in database RNDB, each of the first numbers is 10 combined with the IP address of the IP terminal to which the respective number is assigned.

SThe management unit NM of the VOIP service providers accesses the database RNDB and thus manages the server SERV. By accessing database RNDB and 15 modifying the data contained in database RNDB, VOIP service providers OPI to OP3 are in a position to assign numbers to their subscribers and adapt the routing of calls to a change of subscribers from a first to a second VOIP service provider.

Control unit CONTR1 comprises a management unit MANG and a number of processes, of which three, P1 to P3, are shown in Fig. 2 by way of example.

Management unit MANG is responsible for the communication between processes PI to P3 and interface unit INT1 and between processes PI to P3 and database RNDB, and for the management of these processes.

Control unit CONTRI is triggered for a specific call, such as a call VCON, when server SERV is contacted via interface unit INT1 by one of components SW1 to SW3, for instance by component SW3, which indicates to control unit CONTR1 the establishment through communications network TELENET of a call that is directed to a number from the above-described subset of numbers.

It is also possible to additionally trigger control unit CONTRI for a specific call when server SERV is contacted via interface unit INTI by one of components SWI to SW3 which indicates the establishment through the telephone network of a call directed to a number whose associated terminal has been ported to a VOIP service provider.

Management unit MANG determines whether the above-mentioned conditions are present and, thus, whether control unit CONTR1 is to be triggered for a call of communications network TELENET or not. It detects the presence of these conditions by the type of request messages with which it is contacted by components 10 SWI to SW3, for example. Management unit MANG may also determine the presence of these conditions by checking whether the called number is associated with the above-described subset of numbers, and by accessing database RNDB to determine whether the number has been ported to a VOIP service provider.

If control unit CONTR1 is to be triggered for a call of communications network TELENET, management unit MANG will generate a process which then provides the functions for this call, which are described below with reference to process P1. When these functions have been provided for this call, the associated process is deleted by management unit MANG.

Each of processes P1 to P3 represents the execution of a computer program. The functions performed by them will now be described using process P1 as an example.

In response to a specific request message from component SW3, control unit CONTRI is triggered for the call VCON, and process P1 for the call VCON is generated by management unit MANG. From component SW3, process PI receives, together with the specific request message, a number CN which represents the called number of the specific call VCON. Alternatively, process P1 requests this number for component SW3. From the number CN, process PI then determines which VOIP service provider the IP terminal addressed by the called number is associated with.

Then, process P1 arranges for the specific call VCON to be routed through communications network TELENET to a VOIP gateway associated with the VOIP service provider determined.

This function is implemented, for example, by accessing database RNDB to determine whether the number CN is associated in database RNDB with another number from the subrange of a (another) VOIP service provider or not.

If that is not the case, the call has already been addressed to a VOIP gateway 10 associated with the VOIP service provider of the addressed IP terminal. In that case, the process will not intervene in the establishment of the call VCON through communications network TELENET. If the number CN is associated with another number from that subrange, for instance with a number CN', process PI will send to component SW3 a control message which instructs this component to arrange for the call VCON to be routed to the number CN' as the called number. In this way, routing of the call to a VOIP gateway associated with the other VOIP network operator is initiated.

This function can also be implemented by accessing database RNDB to determine an operator code associated with the telephone number CN. Process P1 will then send to component SW3 a control message which instructs this component to route the call see VCON to a VOIP gateway that is addressed by this operator code in communications network TELENET. The operator code may, for instance, serve as a prefix before the number CN within the call request or, in a separate field of the call request, to address the call VCON within communications network TELENET.

Furthermore, the number CN of the IP address assigned to the call VCON, an IP address IPA, is advantageously determined by the database access. The IP address IPA is sent in a control message to component SW3, which is instructed by the control message to transport the IP address IPA during the establishment of the call VCON through communications network TELENET to the addressed VOIP gateway, here the VOIP gateway GWI. The IP address IPA may, for example, be entered in the request for the call VCON and transported together with the call request. It is also possible to transport the IP address IPA to gateway GW1 over a signaling or user channel of communications network TELENET. This transport may also take place directly from server SERV to gateway GWI if server SERV has a suitable connection to communications network TELENET.

The IP address IPA is then used by VOIP gateway GW1 to complete the call VCON through communications network IPNET to the called terminal, here terminal TE3.

10 If two or more spatially distributed VOIP gateways are associated with the VOIP network operator determined, process PI will advantageously route the call VCON to that VOIP gateway of the VOIP network operator which is closest to the calling telephone terminal and where the charge to be made for the call VCON in communications network TELENET is the lowest.

A further embodiment of the invention will now be described with reference to Fig. 3.

Fig. 3 shows the communications networks TELENET and IPNET, the server SERV', the management unit NM', the VOIP gateway GW1, the gatekeeper GK, and the terminals TEl and TE3.

Gatekeeper GK is a gatekeeper of communications network IPNET. It contains a database RIPDP. In this database, telephone numbers are combined with IP addresses.

By accessing database RIPDP, each VOIP service provider can freely determine the IP addresses associated with the numbers assigned to its subrange of numbers.

Control unit SERV' is constructed like control unit SERV of Fig. 2 with the following differences: Database RNDB has been replaced by a database NPDB. Database NPDB is of the same design as database RNDB of Fig. 2 except for the fact that telephone numbers are not combined with IP addresses.

Control unit CONTRI has been replaced by a control unit CONTRI' which is constructed like control unit CONTRI of Fig. 2 with the following difference: For each called number, for example the number CN, control unit CONTRI', by accessing database RIPDB of gatekeeper GK, determines the IP address that addresses the same IP terminal (TE3) as the called number. This database access takes place via interface unit INT2, which, analogously to interface unit INTI, provides for communication between gatekeeper GK and server SERV'. This 10 communication preferably takes place over communications network IPNET.

OS

o o Management unit NM' performs the functions of management unit NM. Functionally, o. it comprises several management areas GP and SPP1 to SPP3. Management areas SPP1 to SPP3 are associated with VOIP service providers OP1, OP2, and OP3, respectively. Within its respective management area, the respective service provider can control the combination of numbers of its subset with IP addresses independently by accessing database RIPDB. Management area GP controls the change of a S subscriber from one VOIP service provider to another by accessing database NPDB.

This management area is covered by a central function. Through this division of the management areas GP and SPPI to SPP3, effective management of the numbers of the subset of numbers becomes possible.

A further embodiment of the invention will now be described with reference to Fig. 4.

Fig. 4 shows the communications networks TELENET and IPNET, the server SERV", the management unit NM, the VOIP gateway GW4, the components SWI to SW3, and the terminals TEl and TE4.

Control unit CONTR1 has been replaced by a control unit CONTRI" which is constructed like control unit CONTRI of Fig. 2 with the following difference: Control unit CONTR1" does not determine the IP address for a called number. The determination of an IP address is performed by a control unit CONTR2.

Control unit CONTR2, on the one hand, also accesses database RNDB and, on the other hand, communicates via an interface unit INT3 with VOIP gateways GW1 to In response to a request from one of VOIP gateways GWI to GW5, for instance from VOIP gateway GW4, control unit CONTR2 determines an IP address for a called number that addresses the same IP terminal as the called number. The IP address determined by server SERV" is thus transported to the VOIP gateway having 10 sent the request. In determining the IP address, control unit CONTR2 takes account of the fact that the called number may already have been translated by control unit

CONTRI".

Interface unit INT3 is identical in construction to interface unit INT1 of Fig. 2. To permit communication with server SERV, VOIP gateways GW1 to GW5 may incorporate SSF functionality (SSF Service Switching Function) according to the IN functionality. It is also possible, of course, that server SERV communicates with S VOIP gateways GWI to GW5 using the communications mechanisms provided for VOIP gateway- gatekeeper communication. Within this communication, the server can thus act as a gatekeeper for VOIP gateways GWI to Advantageously, server SERV" is designed as a server of communications network IPNET. In another advantageous development, server SERV" is functionally integrated into a gatekeeper of communications network IPNET.

Claims (12)

1. A method of supporting the establishment of telephone calls between telephone terminals of a telephone network and IP terminals of an IP network, wherein two or more VOIP service are assigned a subset of telephone numbers of the telephone network and that the VOIP service providers, in turn, assign numbers of the subset of numbers to IP terminals, so that the respective IP terminal, in addition to being addressable by an IP address assigned to it, can be addressed by this assigned number, that in order to route a call addressed by one of the telephone terminals of the telephone network to a number from the subset of numbers through the telephone network, a server is contacted, that the server determines from the called number of such a specific call which VOIP service provider the IP terminal addressed by the called number is associated with, and that the server arranges for the specific call to be routed through the telephone network to a VOIP gateway associated with the VOIP service provider determined.

2. A method as claimed in claim 1, wherein each of the two or more VOIP service providers is permanently assigned a portion of the subset of telephone numbers of the oeoo telephone network, that by means of a database, the server maps a called first number eoool S" 20 to a second number assigned to the portion of the subset of numbers of one of the VOIP service providers when the terminal assigned to the called number has been ported to this VOIP service provider, and that the server, using the second number as the called number, arranges for the specific call to be routed to the VOIP gateway associated with the VOIP service provider determined.

3. A method as claimed in claim 1, wherein the server further determines the IP address assigned to the called number of the specific call.

4. A method as claimed in claim 3, wherein the IP address is determined by the server when the latter is contacted, and is transported through the telephone network to the VOIP gateway during call establishment. 19 A method as claimed in claim 3, wherein the IP address determined by the server is transported to the VOIP gateway in response to a request of the VOIP gateway.

6. A method as claimed in claim 1, wherein the server is managed by a management unit of the VOIP service provider.

7. A server for supporting the establishment of telephone calls between telephone terminals of a telephone network and IP terminals of an IP network, wherein the server comprises an interface unit for communication with one or more 10 components of the telephone network, that the server further comprises a control unit designed to be triggered for a specific call when the server is contacted via the interface unit by a component of the telephone network which indicates the establishment through the telephone network of a call directed to a number from a subset of numbers which are assigned to two or more VOIP service providers for assignment to IP terminals such that the respective IP terminal, in addition to being addressable by an IP address assigned to this IP terminal, can be addressed by this associated number, and that the control unit is further designed so that when triggered for the specific call, it determines from the called number of the specific call which VOIP service provider the IP terminal addressed by the called number is associated with, and arranges for the specific call to be routed through the telephone network to VOIP gateway associated with the VOIP service provider determined.

8. A server as claimed in claim 7, wherein the control unit is further designed to be additionally triggered for a specific call when the server is contacted via the interface unit by a component of the telephone network which indicates the establishment through the telephone network of a call directed to a number whose associated terminal has been ported to a VOIP service provider.

9. A server as claimed in claim 7, further comprising a database which combines a first number, assigned to a first one of the VOIP service providers, with an IP address and, if the IP terminal designated by the called number has been ported from the first to the second VOIP service provider, with a second number, assigned to a second one of the VOIP service providers. A server as claimed in claim 7, wherein the control unit is further designed to determine for the called number an IP address which addresses the same IP terminal as the called number, the determination being made by accessing a database of a gatekeeper of the IP network.

11. A server as claimed in claim 7, wherein said server is designed as a server of the 10 IP network. .:io 12. A server as claimed in claim 7, wherein said server is functionally integrated with a gatekeeper of the IP network.

13. A computer product for supporting the establishment of telephone calls between Stelephone terminals of a telephone network and IP terminals of an IP network, wherein the computer product is designed to implement, in conjunction with a computer, a control unit which is designed to be triggered for a specific call when contacted by a component of the telephone network which detects the establishment through the telephone network of a call directed to a number from a subset of numbers which are assigned to two or more VOIP service providers for assignment to IP terminals such that the respective IP terminal, in addition to be addressable by an IP address assigned to this IP terminal, can be addressed by this assigned number, and that the control unit is further designed so that when triggered for the specific call, it determines from the called number of the specific call which VOIP service provider the IP terminal addressed by the called number is associated with, and arranges for the specific call to be routed through the telephone network to a VOIP gateway associated with the VOIP service provider determined.

14. A method of supporting the establishment of telephone calls between telephone terminals of a telephone network and IP terminals of an IP network substantially as herein described with reference to the accompanying drawings. A server substantially as herein described with reference to the accompanying drawings.

16. A computer product substantially as herein described with reference to the accompanying drawings. *04 :i e