METHOD AND DEVICE IN COMMUNICATION NETWORK

Abstract: A method and an apparatus for enabling the redirection of calls made to a terminal in a first subnetwork to a physical connection in a second subnetwork, said subnetworks constituting parts of a communications network having incompatible addressing standards. The apparatus according to the invention comprises means for dynamically allocating an address in said first subnetwork to an address in said second subnetwork. According to the invention units in the respective subnetwork are used to register associations between the addresses according to the different addressing systems.

Description: METHOD AND DEVI CE IN COMMUNI CATION NETWORK Technical Field The present invention relates to the field of voice communication between a telecommunications network and a data communication network, such as an Internet Protocol (IP) network, and more specifically to a method and an apparatus for enabling the redirection of telephone calls to a physical connection in the data communication network. Description of Related Art Currently, solutions exist for the voice communication with terminals connected to IP networks, said terminals comprising telephony software and hardware such as microphones and loudspeakers. Each terminal is identified by its IP address, which may be permanent or assigned dynamically. As common in the art, each terminal connected to the telephone network is also identified by another identity, such as a Universal Resource Identifier (URI) or an E.164 number. How to assign IP ad- dresses dynamically is well known in the art, and is discussed, for example in Foo et al: "Approaches for resolving dynamic IP addressing, Internet Resarch", Electronic Networking Applications and Policy, Vol. 7, No. 3, 1997, pp. 208-216, ISSN 1066- 2243. EP 0 781 015 A2 discloses a telephone apparatus for use in an IP network, and EP 0 781 016 A2 discloses a telephone system for use with a computer network such as an IP network. Several methods may be used for redirection of calls in the same network: Particular number series may be used for numbers that are only logical numbers associated with one or more physical connections, such as the 020 or 071 numbers in Sweden, that is, toll-free numbers. Subscribers may redirect calls to their own connections. In cellular telecommunications networks the HLR and VLR function may be seen as a kind of redirection service, directing the call to the cell in which the subscriber is currently found. Between different types of telephone networks the number plans are usually coordinated so that each network has its own number series. In this way, the addressing of terminals in telecommunications networks is usually clear and unambiguous even if the terminals are found in different subnetworks. Between other types of networks this is not always the case. There are no known solutions for enabling the redirection, for example, of telephone calls made to terminals in a telecommunications network to terminals in a data communication network. Object of the Invention Thus, it is an object of the present invention to improve the possibilities for voice communication between two subnetworks in a communications network when the addressing systems in said two subnetworks are not coordinated. Summary of the Invention This object is achieved according to the invention by a node for use in a communications network comprising at least a first and a second subnetwork interconnected through at least one connecting means, said subnetworks using different addressing systems, comprising means for dynamically allocating an address in said first subnetwork to an address in said second subnetwork. The object is also achieved by a method in a communications network comprising at least a first and a second subnetwork, said subnetworks having different addressing systems and being interconnected by at least one connection means, said method comprising the following steps: - creating an association between a logical address of a terminal in the second subnetwork and a logical and/or physical address in the first subnetwork; - creating an association between the logical address of said terminal in the second subnetwork and the appropriate physical address in the second subnetwork; - when a call is being made to said terminal in the second subnetwork from a calling terminal in said first or second subnetwork: - resolving the number to find the associated logical address of the terminal; - forwarding the connection to the connection means - resolving number to find the associated physical address of the terminal - connecting to the terminal using the appropriate address. In this way calls for a terminal having an address in a first subnetwork can be redirected to a second subnetwork even if the addressing systems of the two subnetworks are not compatible. According to a preferred embodiment said first subnetwork is a data communications network according to the IP protocol, said second subnetwork is an intelligent telecommunications network and said connection means is a gateway. According to a preferred embodiment, said association between the logical address in the data communications network and the logical and/or physical address in the telecommunications network established in a node in the data communications network. In this case, the node may be a gatekeeper for use in a data communications network, such as an IP network. It may also be a SIP server or an ILS server in a data communications network. According to another preferred embodiment, said association between the logical address in the data communications network and the logical and/or physical address in the telecommunications network is established in a node in the telecommunications network. In this embodiment, said node may be a switching control point in a telecommuni- cations network. It may also be a home location register in a mobile telecommunications network. Brief Description of the Drawings The present invention will be described in more detail in the following, with refer- ence to the appended drawings, in which: Figure 1 is a schematic overview of a network according to a first embodiment of the invention; Figure 2 shows, in more detail, a network according to a second embodiment of the invention; Figure 3 is a flow chart of the actions taken to register an IP telephone temporarily in the network according to the first embodiment of the invention; Figure 4 is a flow chart of the actions taken to register an IP telephone temporarily in the network according to the second embodiment of the invention; Figure 5 is a flow chart of the actions taken to make a call to an IP telephone regis- tered temporarily in the network according to the invention; Figure 6 is a flow chart of the actions taken to unregister an IP telephone temporarily registered in the network according to the invention. Detailed Description of Embodiments Figure 1 shows an example of a network configuration in which the invention may be carried out. A first 1 and a second 3 subnetwork each forming part of an overall commumcations network are interconnected by means of at least one interworking unit, or connection unit 5 designed for adaptation of the communication between the two subnetworks. The first and second subnetworks may be, for example, a tele- communications network 1 and a data communications network 3, interconnected through a gateway 5 in a way well known in the art. To the first subnetwork a number of terminals 7, 9 are connected. The first subnet- work may be any kind of communications system, such as an ISDN network, a data communications network or a cellular telecommunications network. The first subnetwork also comprises a call direction means 11, which is any node in the subnetwork that can direct, or redirect, calls in the subnetwork or between subnetworks. In an intelligent telecommunications network the call direction means will be a service control point SCP. In a cellular telecommunications network the call direction means will be an home location register (HLR) and/or a visitor location register (VLR). To the second subnetwork 3 a number of terminals 13, 15 are connected. The sec- ond subnetwork 3 comprises, or is connected to a registration device 17, such as a gatekeeper in an H.323 IP telephony system. As common in the art, the registration device 17 comprises, among other things, a first table 18 associating physical addresses in the network, such as IP addresses, with logical addresses, such as an IP telephone number. In ways known in the art IP addresses may be allocated permanently or temporarily to logical addresses. The registration device usually has a number series, or domain, allocated to it so that it can recognize terminals belonging to its number series, or domain, as terminals that it should serve. To enable terminals registered in the first subnetwork to roam into the second subnetwork, according to the invention, the registration device 17 also comprises a list 19 of idle numbers which may be allocated temporarily to guests in the second subnetwork. The registration device 17 also comprises a second table 20 in which the temporarily allocated numbers can be associated with IP addresses. When such a registration is made, the registration device also informs the call directing means 11 in the first subnetwork of the number that has been temporarily allocated to a guest from the first subnetwork. The call direction means 11 registers the temporarily allocated number and the number to which it has been allocated, in a table 21. The IP telephone number may be a logical number configured to identify one or more physical connections, such as a 020 number in Sweden. It may also be an ordinary telephone number according to the EJ64 standard, identifying a physical connection. In this case, the standard service call forwarding may be used to redirect the telephone number to the IP telephone. This has the disadvantage that the call is always routed through the local exchange to which the physical connection identified by the telephone number belongs, which may make a call to the IP telephone more expensive, especially if the IP telephone is far away from the physical connection, but it is nevertheless possible. In both these cases, the call directing node may be a service control point (SCP) in an intelligent network. The number may also be a number in a mobile telephony network, in which case the call directing node is the home location register (HLR) in which the telephone number is registered. Figure 2 shows an embodiment of the invention. In this embodiment, the first and second subnetwork are a telecommunications network 101 and a data communications network 103, respectively, interconnected by at least one gateway 105. In this embodiment, the telecommunications network 101 is a public switched te- lephony system (PSTN) and the data communications network 103 is an IP network, such as the Internet. To the telecommunications network 101 a number of telephones 107, 109 are connected by wired connections. The telecommunications network 101 comprises at least one call directing means 111. In an intelligent network this call directing means is normally a service control point (SCP) or a service switching and control point (SSCP). In other types of networks it may be other types of nodes, as will be discussed below. The IP network comprises a number of terminals, 113, 115. It also comprises a gatekeeper 117, as is well known in the art. The gatekeeper 117, among other things, handles the associations between IP addresses and IP telephone numbers, in a table 118. How to allocate IP addresses permanently or dynamically is well known in the art. In this embodiment, the SCP 111 comprises a list 119 of idle IP telephone numbers in the gatekeeper's 117 domain, which may be dynamically associated with telephone numbers in the SCP's 111 domain. The gatekeeper also comprises a table 120 for handling associations between IP telephone numbers assigned in this way and IP addresses in the IP network. As an example, assume that the IP addresses have the format xxx.xxx, the IP tele- phone numbers, that is, the telephone numbers in the gatekeeper's 117 domain, all belong to the number series 900-xxxx, and the telephone numbers in the telecommunications network, that is in the SCP's 111 domain all belong to the number series 700-xxxx, each x representing an arbitrary digit. In this case, as before, the gatekeeper 117 comprises a table 118 providing associations between IP addresses and IP telephone numbers. It also comprises a table 120 having the same format, but the IP telephone numbers registered here will be numbers taken from the list 119 of idle numbers, which, in this embodiment, is found in the SCP 111. The SCP 111 also comprises a table 121 providing associations between the numbers in the SCP's domain, that is numbers in the number series 700-xxxx, and IP telephone numbers, that is, numbers in the number series 900-xxxx. In all examples, x indicates a digit. Of course, the format shown is only intended as an example. The addresses, and/or telephone numbers may have any format including any combination of alphanumeric or other characters. Shown in Figure 2, to illustrate the invention, the terminals 107, 109 connected to the telecommunications network 101 are identified by numbers in the SCP's domain, 700-5678 and 700-2345, respectively. One of the terminals 113 connected to the data communications network 103 is identified by a number in the SCP's do- main, 700-1234. The other terminal 115 connected to the data communications network 103 is identified by a number 900-3456 in the gatekeeper's 117 domain. This means that the terminal 115 having a number in the gatekeeper's domain only needs to get an IP address associated with its number and the association registered in the first table 118. The terminal 113 having only a number in the SCP's domain must first have a number in the gatekeeper's domain allocated to it, the allocation registered in the SCP and then an IP address associated with the number in the gatekeeper's domain. The procedure of allocating numbers is described in more detail in connection with Figures 3 and 4. Calls can be made from a terminal in the telecommunications network 101 to a terminal connected to the data communications network 103, or between two terminals connected to the data communications network. The procedure of making a call is described in more detail in connection with Figure 5. In a third embodiment, not shown in the Figures, the list of numbers that may be allocated dynamically may be found in the connection means 5 or 105, respectively, instead of a in node in one of the subnetworks. The terminals connected to the data communications network may be devices in- tended specifically for telephony through an IP network or computers or computer terminals equipped with the necessary hardware and software for IP telephony. Figure 3 is a flow chart of the actions taken to register an IP telephone temporarily in the network shown in Figure 1 and make sure any calls made to one or more specified numbers are directed to this IP telephone. It is assumed that the IP tele- phone has a permanent IP address or has already obtained a dynamic IP address before the procedure starts. The process of allocating dynamic IP addresses is well known in the art. Step S301: The IP telephone is logged on to the registration means, i.e. in the example shown in Figure 1, the gatekeeper. The login includes the telephone number or numbers, as well as the IP address or host name on which the IP telephone resides. Of course, some or all of these numbers and addresses may be preset in the login window as is common in login procedures. Step S302: If the number to be registered is within the domain of the registration means, go to step S306; otherwise, go to step S303. Step S303: Does the registration means have an associated call direction means for this domain? If yes, go to step S304, if no, go to step S308. Step S304: A number is dynamically taken from a subset of the previously unused numbers of the domain for the registration means. Step S305: The registration means informs the call directing means, i.e. in the example shown in Figure 1, the SCP, that the allocated dynamic address should be used to identify the IP telephone in question. This is indicated as a dashed line between the registration means and the call directing means in Figure 1. Step S306: The registration means associates the new allocated number in the registration means with the IP address registered in the registration means. Step S307: The registration means confirms the registration of the IP telephone to the user of the IP telephone. End of procedure. Step S308: The registration is refused. End of procedure. In the discussion above, the table of idle numbers in the domain of the second subnetwork has been assumed to be found in the registration means of the second sub- network. It may, however, be found in any other node in the overall network, such as the call directing means or the interworking unit. Figure 4 is a flow chart of the actions that are taken to register an IP telephone, that is, corresponding to the procedure shown in Figure 2, assuming that the list of idle numbers is managed by the call directing means. Step S401: The IP telephone is logged on to the registration means, that is, in the example shown in Figure 2, the gatekeeper. The login procedure includes the telephone number or numbers, as well as the IP address or host name where the IP telephone resides. Of course, some or all these numbers and addresses may be preset in the login window as is common in login procedures. Step S402: Is the number to be registered within the domain of the registration means? If no, go to step S406, if yes, go to step S403. Step S403 : Is the number to be registered in a domain for which the registration means has an associated call direction means? If yes, go to step 404; if no, go to step S408. Step S404: The registration means asks the call direction means to allocate a dynamic address and associate this dynamic number to the telephone number that is to be registered. The call direction means allocates a dynamic address taken from a subset of idle numbers. The allocated dynamic address is now marked as occupied and cannot be allocated to another telephone number. Step S405: The call direction means informs the registration means of the new dy- namic address. Step S406: The registration means associates the new dynamic address, received from the call direction means, with the IP address stored in the registration means. Step S407: The registration means confirms or denies the registration of the IP telephone to the user of the IP telephone. End of procedure. Step S408: The registration is denied. End of procedure. Figure 5 shows the actions that take place when someone makes a call that is redirected to an IP telephone registered according to the procedure shown in Figure 2: Step S501: The caller calls the desired telephone number. Step S502: The telephone number is recognized as one that should be redirected, and is therefore forwarded to the call directing means which resolves the number and returns the resulting number, which in this case will be a previously dynamically allocated number. Step S503: The gateway handling the resulting number is identified, for example the gateway 5 in Figure 1, and a call is set up through this gateway. Step S504: The gateway forwards the number to the registration means to be re- solved into an IP address. Step S505: The call is set up to the IP address identified in step S504. Figure 6 is a flow chart of the actions taken when the IP telephone is no longer to receive the calls to the telephone number concerned: Step S601: The IP telephone is turned off, or a notification is sent from the IP telephone to the registration means that the IP telephone is no longer to receive calls made to a certain telephone number. If the IP telephone is turned off, all entries of telephone numbers to be directed to this telephone will be deleted in the registration means and forwarding means. If the IP telephone remains turned on, it may send a notification to the registration means that one or more telephone numbers, for which the IP telephone should no longer be registered, should no longer be associated with it. Calls to other numbers may still be directed to the IP telephone. Step S602: The registration means notifies the call directing means that the association or associations should be removed for the specified numbers. Step S603 : The call directing means removes the association or associations to be removed. Step S604: The client is notified that the associations have been removed. End of procedure.

Claims: Claims 1. A node for use in a communications network comprising at least a first and a second subnetwork interconnected through at least one connecting means, said subnetworks using different addressing systems, said node being characterized in that it comprises means for dynamically allocating an address in said first subnetwork to an address in said second subnetwork. 2. A node according to claim 1, said node being a gatekeeper for use in a data communications network. 3. A node according to claim 1, said node being a home location register in a mobile telecommunications network. 4. A node according to claim 1, said node being a switching control point in a tele- communications network. 5. A node according to claim 1, said node being a SIP server in a data communications network. 6. A node according to claim 1, said node being an ILS server in a data communications network. 7. A communications network comprising at least a first and a second subnetwork and means for interconnecting said two subnetworks, said subnetworks having different addressing systems, said communications network being characterized in that it comprises a node according to any one of the claims 1-4 and a node comprising a list of addresses in one subnetwork that may be dynamically allocated to addresses in another subnetwork. 8. A method in a communications network comprising at least a first and a second subnetwork, said subnetworks having different addressing systems and being interconnected by at least one connection means, characterized by the following steps: - creating an association between a logical address of a terminal in the second subnetwork and a logical and/or physical address in the first subnetwork; - creating an association between the logical address of said terminal in the second subnetwork and the appropriate physical address in the second subnetwork; - when a call is being made to said terminal in the second subnetwork from a call- ing terminal in said first or second subnetwork: - resolving the number to find the associated logical address of the terminal; - forwarding the connection to the connection means - resolving number to find the associated physical address of the ter- minal - connecting to the terminal using the appropriate address. 9. A method according to claim 8, wherein said first subnetwork is a data communications network according to the IP protocol, said second subnetwork is an intel- ligent telecommunications network and said connection means is a gateway. 10. A method according to claim 8, wherein said association between the logical address in the data communications network and the logical and/or physical address in the telecommunications network is established in a node in the data communications network. 11. A method according to claim 8 or 9, wherein said association between the logical address in the data communications network and the logical and/or physical address in the telecommunications network is established in a node in the tele- communications network. 12. A method according to claim 11, wherein the telecommunications network is a PSTN network and said node in the telecommunications network is an SCP. 13. A method according to claim 11, wherein the telecommunications network is a cellular network and said node in the telecommunications network is an HLR.

Inventors: LUNDGREN HENRIK, LUNDSTROEM JENS, VASQUEZ MARCELA, LUNDGREN, HENRIK, LUNDSTROEM, JENS, VASQUEZ, MARCELA
Applicants: ERICSSON TELEFON AB L M, LUNDGREN HENRIK, LUNDSTROEM JENS, TELIA AB, VASQUEZ MARCELA, LUNDGREN, HENRIK, LUNDSTROEM, JENS, TELEFONAKTIEBOLAGET LM ERICSSON (PUBL), TELIA AB (PUBL), VASQUEZ, MARCELA
Application year: 1999
Main classification: H04M3
IPC codes: H04M3, H04M7, H04Q3