The invention relates registering a communication client at a communication server, wherein the communication client is associated to a mobile terminal of a circuit-switched network which is associated to a mobile switching node of the circu it-switched network. The invention relates further supporting a communication between a first communication client which is registered at a first communication server and a second commun ication client wh ich is registered at a second communication server, wherein the first communication client is associated to a mobile terminal of a circuit-switched network which is associated to a mobile switching node of the circuit-switched network.

Background

The Extensible Messag ing and Presence Protocol (XM PP) is an open Extensible Markup Language (XML) protocol for near-real-time messaging, presence, and request-response services. These services are also named as instant messaging services. The core features of the XMPP are defined in the IETF standard RFC 3920. The basic syntax and semantics were developed originally within the Jabber open-source community. Although XMPP is not wedded to any specific network architecture, to date it usually has been implemented via a client-server architecture wherein a client utilizing XMPP accesses a server over a TCP connection, and servers also communicate with each other over TCP connections. Being an open standard, XMPP has got quite attraction in the open source community world wide and numerous free software packages exist implementing XMPP clients and XMPP server on different platforms. Some companies are basing their chat and voice offerings on XMPP specifications. Fig . 1 shows a schematic d iagram of a mobile communication network which is connected to a TCP/IP-based network 100, wh ich can be the Internet or any other TCP/IP based network. In this embodiment, three XMPP servers 1 1 1 , 121 , 131 are connected to the Internet 100. Two XMPP clients 1 12, 122 are associated to two of the XMPP server 1 1 1 , 121 via a TCP/IP connection. The XMPP clients 1 12, 122 can e.g. be a personal computer or a laptop which is connected to the internet 100 via a normal dial-connection. The address 1 13 of the first XMPP client 1 12 "clientl " is "clientl @XMPPserver1 .domain/devicel " wherein the address 1 23 of the second XMPP client 122 is "client2@XMPPserver2.domain/device2". In Fig. 1 and in Fig. 4, the addresses 1 13, 123, 133 are disclosed in a simplified form because the domain indicator and the device indicator are missing for better view. These addresses are in accordance with the standardized XMPP JID (Jabber identity) which is a combination of a user ID, a server ID and a device ID. By these addresses 1 13, 123, 133 all XMPP clients 1 12, 122, 132 can be identified and data can be routed via the internet. Fig. 1 further discloses a mobile communication network, wherein only selected components of the mobile communication network are depicted . A mobile terminal or user equipment 18 comprises a XMPP client 132. The XMPP client 132 can be an application which is stored in the UE 18. The XMPP client 132 is associated to a XMPP server 1 31 via a TCP-based connection. The address 1 33 of the XM P P cl i e n t 1 32 i s " cl i e n t3@XM P P server3.domain/UEdevice". This connection can be realized by a wireless LAN connection, wherein the UE 18 is associated to a WLAN router 19 which is further connected to the Internet 100. Another possibility is that the UE 18 is connected via the radio network 17 to a packet switched (PS) network or to an evolved packet switched (EPS) network. One setup of a PS network is depicted in Fig. 1 by a Serving GPRS Support Node (SGSN) node 15 and Gateway GPRS Support Node (GGSN) 16 which is l in ked via an I P based core network connection and via the Internet 100 to the XMPP server 1 31 . The embodiment according Fig . 1 further discloses a connection between the SGSN node 15 of a packet switched network and a mobile switching node 14, which can be a MSC-S node 14 of a circuit switched (CS) network. This link between both nodes, wh ich is called Gs interface, depicts the possibil ity of transferring data between both networks. A further packet switched network is the Evolved Packet Core (EPC) network, wherein one node is the Mobility Management Entity (MME), which can be linked to the MSC-S via a SGs interface. Fig. 1 does not depict fu rther gateway nodes wh ich m ig ht be necessary to implement a connection between a circuit-switched network and a packet switched network.

Fig. 2 shows a block diagram of a prior-art mobile switching node 14, which is in this embodiment a MSC-S node 14, wherein only selected parts are depicted. The MSC-S 14 comprises a GSM call control function 143 which contains mobile traffic coordinators for originating and/or terminating calls and emergency calls. The coordinators are mainly used for call transaction setup, call forwarding, call supervision and call release. It allows also direct and handle calls towards other circuit switched networks. The GSM call control function 143 is linked with the core network interface 145 which hosts the core network interfaces of the MSC-S. The core network interface 145 analyses incoming signalling which is either forwarded to another node in the core network or handled locally and terminated at a radio network interface. For outgoing signalling a routing function 146 is consulted to determine the next destination node and the physical interface to reach it. The core network interface 145 is IP (Internet Protocol) based. The GSM call control function 143 is further connected to a GSM mobility function 142 which allows the mobile terminal to roam between radio location areas and to continue ongoing calls also across radio network borders. One main function is the handover procedure to hand over a mobile terminal from one area to another. The GSM mobility function 142 or mobility management function therefore contains a logic coordinator for mobility, roaming and handover procedures and handles the location updating functions and handover functions. Furthermore the GSM mobility function 142 contains functions for packing or unpacking of signalling messages to the terminal and to the radio network belonging to mobility. Signalling messages can be used e.g. in case of authentication, identification and location updating.

The GSM mobility function 142 is connected to the A-/lu-interface function 141 which hosts the radio network interface resources of the MSC-S 14.

The MSC-S 14 further comprises a charging function 144 which is connected to the GSM call control function 143 and the core network interface 145. The charging function 144 is a basic function in the MSC-S 14 to collect traffic case related data to be used for offline billing.

The MSC-S 14 further comprises a VLR data storage 147 which stores the subscriber data. The VLR 147 is connected to a home location register 4 (HLR) which is a central database that contains details of each mobile phone subscriber that is authorized to use the core network.

The MSC-S further comprises a GSM authentication component 148 which implements the GSM authentication algorithm . The GSM authentication component 148 is also con nected to the H LR 4 to receive and verify authentication data from the central database.

Fig. 3 depicts a block diagram of a well known XMPP server 131 . The XMPP server 131 contains a XMPP stanzas router 131 1 which is the backbone of the XMPP server 131 . The XMPP stanzas router 131 1 accepts connections from XM PP server com ponents and passes XM L (extended marku p language) packets between XMPP server components. A client to server component (c2s) 1312 handles communication with associated XMPP clients. The XMPP stanzas router 131 1 is connected to a XMPP session manager 1316. The session manager 1316 implements the bulk of the instant messaging features like message passing, presence, roster and subscription. The session manager 1316 is connected to data storage in order to provide persistent data storage. The associated data storage is not depicted in Fig. 3. It could be located outside the XMPP server 131 or it could be part of the XMPP server 131 . Additionally the session manager 1316 handles the XMPP extensions of service discovery and privacy lists. A c2s component 1312 is connected to the XMPP stanzas router 1 31 1 and is e.g. responsible for connecting XMPP clients 1 12, 122, 1 32 to the XMPP server 1 31 , passing communication packets to a session manager 1316 of the XMPP server 131 , authenticating XMPP clients 1 1 2, 122, 132, registering users and triggers activity with the session manager 1316. A server to server (s2s) component 1 31 5 is con nected to th e XM P P stanzas router 1 31 1 and h and l es communications with external XMPP servers by passing communication packets between other internal components and external servers. The s2s component 1315 further performs dial-back function to authenticate remote XMPP servers. A multi user chat (muc) 1 314 is connected to the XMPP stanzas router 131 1 to implement support for chat rooms. A publish subscribe component (pubsub) 1313 implements a generic functionality for providing presence. The pubsub component 1313 is connected to the Stanzas router 131 1 . The XMPP server 131 is connected via a TCP/IP connection to the Internet 100 such that it possible to reach this server from any other device connected to the Internet 1 00. The s2s component 1315 and the c2s component 1312 communicate via the Internet 100 with external clients 1 12, 122, 132 and external server 1 1 1 , 121 .

In the state of art, if two mobile terminals want to communicate with each other via their XMPP clients, the communication has to be routed via the Internet, even if both mobile terminals are associated to the same mobile network. Operators of mobile communication networks might have the need to run more efficiently instant communication services.

Summary

It is an object of the present invention to improve the prior art instant communication service. This object is achieved by the independent claims. Advantageous embodiments are described in the dependent claims.

One embodiment of the invention relates to a method of registering a communication client at a communication server, wherein the communication client is associated to a mobile terminal and wherein the communication server is associated to a mobile switching node of a circuit switched network. The method comprises the steps of initiating a connection between the communication server and the communication client, sending identification information to the communication server by the communication client via the connection, interrogating an authentication module of the mobile switching node to perform a user authentication by the communication server, fetching subscriber information from a database by the communication server and sending subscriber information to the communication client via the connection. The communication server could be a XMPP server and the communication client could be a XMPP client but there might be also other communication protocols possible. The switching node could be a MSC-S of a circuit switched network. The database could be a Visitor Location Register, VLR, of the MSC- S.

In an embodiment of the invention, the database, which could be the VLR, fetches the subscriber information from a central database. The central database can be located anywhere in the network and is reachable by any VLR or MSC-S database. If the subscriber information is stored in a central database, which might be the Home Location Register (HLR), a subscriber can be allocated to any commun ication server or MSC-S because it is possible that the communication server or the MSC-S will fetch the needed subscriber data from the centralized database.

The communication server is using components of the MSC-S during the registration process. This will reduce the complexity of the XMPP enhanced MSC-S and the costs for implementing an open communication service like XMPP into a mobile communication network. By implementing such communication service, already established data links and network capacities could be used to transfer communication data . The control of the XMPP services, like Voice-over-IP (VoIP) or subscriber buddy list, is under control of the mobile network operator to use several synerg ies to implement th is service into the mobile network. By using an open communication protocol like XMPP, there is a high acceptance in the user-community because of the transparency of this communication protocol. It is easy to implement further services from other vendors, based on this standard, into the network.

In a further embodiment of the invention, parts of the identification information is determined from a subscriber identity module, SIM, associated with the mobile terminal . The SIM could be a SIM card which comprises e.g . the Mobile Subscriber Integrated Services Digital Network Number, MSISDN or the International Mobile Subscriber Identity, IMSI . The information can be derived from the SIM to construct the identification information or parts of it. It is further possible to derive one part of the identification information from the International Mobile Equipment Identity, IMEI. Another possibility to build parts of the identification information is the use of the Access Point Name, APN.

The advantage of building the identification information from information stored at the SIM card or in the mobile terminal is the reuse of already known information . It is not necessary for a user of a XMPP client to insert a new user name or the l ike. It is an automatic process to create identification information like the Jabber I D from available information on the mobile terminal.

In a further embodiment of the invention, at least one part of the identification information is stored in a Domain Name System, DNS, server in combination with an IP-address of the communication server. The part of the identification information can be the domain name which is stored in the DNS server in combination with an IP-address. This could be done in a table wherein every domain name is correlated to an IP-address such that if an external client or server wants to send data to a client which is located in a specific domain, it fetches the IP address of the specific domain from the DNS server and sends the data to the server related to the fetched IP-address.

In a further embodiment of the invention the mobile terminal is CS connected via a rad io network to the mobile switching node. The method further comprises the step of sending the IP-address of the communication server, which is associated to the mobile switching node to the DNS server in combination with the at least one part of the identification information of the communication client. This will have the effect that if the mobile terminal changes the location and must be attached to a new mobile switching node, the communication server which is allocated to the new mobile switching node, should take over the server function for the communication client which is allocated to the mobile terminal. Therefore the new communication server can use the resources of the new mobile switching node when a communication via the communication client is established.

In a further embod iment of the invention , the method of reg istering a communication client at a communication server the communication client receives a text message by the communication client which contains configuration information. This text message could be a Short Message Service, SMS. The sending of configuration information to the communication cl ient leaves more freedom in the way the identification information is constructed . As an advantage, a subscriber can be distributed to multiple domains or domains different to the APN domain.

The invention also relates to a method of supporting a communication between a first communication cl ient wh ich is reg istered at a fi rst communication server via a connection and a second communication client which is registered at a second communication server, wherein the first communication client is associated to a mobile terminal. The communication server is associated to a mobile switching node of a circuit switched network. The method comprises the steps of sending of communication data between the first communication client and the first communication server over the connection and routing communication data between the first communication server and the second communication server over a core network interface of the mobile switching node. Again there is the advantage of reusing already established components and network capacity. The communication server could be a XMPP server and the communication client could be a XMPP client but there might be also other commu n ication protocols possible. The switching node could be a MSC-S of a circuit switched network.

In a further embodiment, the mobile terminal is CS connected via a radio network to the mobile switching node. The method further comprises the step of sending the IP-address of the communication server, which is associated to the mobile switching node, to the Domain Name System, DNS, server in combination with identification information of the commun ication cl ient. Advantageously the method further comprises the step of fetching the addresses of the first communication client and the second communication client from the DNS server when communication data is routed between the first communication server and the second communication server. Therefore it is possible that a mobile terminal, comprising the first communication client, can be allocated to a new mobile switching node with a new allocated communication server because the IP-address of the new communication server will be send to the DNS server and replaces the old IP-address which was correlated to the current identification information.

In a further embodiment the core network interface is an IP core network interface. Further the connection is a Transmission Control Protocol, TCP, or a Hypertext Transfer Protocol (HTTP) based connection. The communication according to the XMPP standard is based on the TCP protocol or the HTTP protocol (called BOSH) which is setup on the IP protocol.

If the core network interface is also IP based, no protocol transfer must be performed. This will reduce latency in the network.

In a further embodiment of the invention, the method further comprises the step of providing charging data to a charging function of the mobile switching node based on the communication data. The implementation of the already used charging function of an MSC-S in a mobile communication makes it easier to implement the charging of the XMPP-services like VoIP or the like.

In a further embodiment the communication server is integrated in the mobile switch ing node. This will reduce the costs for implementing the communication service into the mobile network because the communication server could use several components of the MSC-S including e.g. also the power supply. "Integrated" means that the commun ication server is a hardware module in the MSC-S or a plug-in board which could be inserted into a rack which comprises among others several MSC-S plug-in boards.

The invention further relates to a mobile switching node of a circuit-switched network, CS, comprising a communication server which is adapted to register with a communication client over a client to server component, wherein the communication client is associated to a mobile terminal. The client to server component comprises a comm un ication un it, adapted to establ ish a connection to the communication client, a receiving unit, adapted to receive identification information from the communication client by the connection, an interrogation unit, adapted to interrogate an authentication module of the mobile switching node to perform a user authentication , a fetching unit, adapted to fetch subscriber information from a database, and a sending unit, adapted to send subscriber information to the communication client via the connection.

The invention further relates to a mobile switching node of a circuit-switched network, CS, comprising a core network interface adapted to connect the mobile switching node to the circuit-switched network and a communication server. The communication server is adapted to communicate to a communication client which is associated to a mobile terminal. The communication server comprises a client to server component adapted to send communication data to the communication client. The core network interface is further adapted to route communication data from a server to server component of the communication server to a further communication server.

The mobile switching node, which could be a MSC-S, could be adapted to perform all the steps of the before mentioned methods.

The present invention also concerns computer programs comprising portions of software codes in order to implement the method as described above when operated by a respective processing unit of a user device and a recipient device. The computer prog ram can be stored on a computer-readable medium. The computer-readable medium can be a permanent or rewritable memory within the user device or the recipient device or located externally. The respective computer program can also be transferred to the user device or recipient device for example via a cable or a wireless link as a sequence of signals. In the following, detailed embodiments of the present invention shall be descri bed i n o rd e r to g ive th e s k i l l ed pe rson a fu l l a n d co m plete understanding. However, these embodiments are illustrative and not intended to be limiting.

Brief Description of the Figures

Fig. 1 shows a schematic diagram of a mobile communication network which is connected to a TCP/IP-based network according to the prior art;

Fig. 2 shows a block diagram of an embodiment of a mobile switching node without an integrated communication server according to the prior art;

Fig. 3 shows a block diagram of an embodiment of a communication server according to the prior art;

Fig. 4 shows a schematic diagram of a mobile communication network wh ich is connected to a TCP/I P-based network, according to an embodiment of the invention;

Fig. 5 shows a block diagram of an embodiment of a mobile switching node with an integrated communication server;

Fig. 6 shows a block diagram of an embodiment of a mobile switching node with an integrated communication server;

Fig. 7 shows a schematic diagram of an embodiment of a communication network including several communication servers and mobile switching nodes. Detailed Description

Fig. 4 depicts one embodiment of the invention. The third XMPP server 3 is associated to the MSC-S 2 of a mobile communication network which can also be understood as an MSC. It is possible that the XMPP server 3 is an integral part of the MSC-S 2. Therefore the MSC-S 2 is enhanced by the XMPP server 3. The XMPP server 3 can also be a server node which is logically associated to the MSC-S 2 to use some of the MSC-S functions. The embodiment according Fig. 4 further discloses a Gs-connection between the SGSN node 15 of a packet switched network and the MSC node 2 of a circuit switched network. This link between both nodes depicts the possibility of transferring data between both mobile networks. Fig. 4 does not depict further gateway nodes which might be necessary to implement a connection between a circuit-switched network and a packet switched network. Another alternative for a packet switched network is the EPC network which comprises a MME. The MME is connected via a SGs interface to the MSC-S 2. This alternative is not depicted in Fig. 4.

Fig. 5 depicts one embodiment of MSC-S 2 with an integrated XMPP server 3. The XM PP server 3 can be a separate module wh ich is inserted as a hardware component into the MSC-S hardware. The XMPP server 3 could also be a separate plug in card which can be inserted into a rack which comprises among others several MSC-S plug-in cards. The XMPP server 3 must be logically associated to the MSC-S 2. In the embodiment of Fig. 5 the XMPP stanzas router 35 of the XMPP server 3 is connected to the GSM call control function 23 of the MSC-S for XMPP-CS interworking to perform the conversion between the XMPP protocol and the CS protocol at breakout.

Further the XMPP session manager 34 of the XMPP server 3 is connected to the charging function 24 of the MSC-S 2 to add XMPP related data to the charging information. E.g. when the session manager 34 reports information about a chat session to the charging function of the MSC-S 2 the operator of this mobile network is able to charge e.g. the duration of the chat or the number of chat messages. The XMPP session manager 34 is further connected to the visitor location register (VLR) 27 of the MSC-S 2. The VLR 27 is associated to the MSC-S 2 and can be located inside the MSC-S 2 or can be an outside entity which is e.g. inserted into a rack which comprises among others the MSC-S 2 plug in card . This subscriber storage area can now be used as persistent data storage for the XMPP protocol such as offline messages or privacy lists.

The GSM authentication function 28 of the MSC-S 2 is connected via the c2s component 36 with the XMPP stanzas router 35. The GSM authentication function 28 can be used by the c2s component 36 to authenticate a XMPP client or user.

The XMPP stanzas router 35 is connected via the s2s component 33 with the core network interface 25 and the routing function 26 of the MSC-S. The routing function 26 acts in support of the s2s component to resolve hostnames for the s2s component 25 as part of the XMPP dial-back authentication. The dial-back authentication, as mentioned in the RFC standard 3920, is for verification of the identity of an originating XMPP server. The s2s component 33 can reuse the existing IP network interface of the MSC-S node and the core network of the mobile communication network to send communication data to another XMPP server 1 1 1 , 121 which can be located anywhere in the Internet 100 or in another node of the same or another mobile communication network.

Fig . 6 depicts an embodiment of a mobile switching node, MSC-S, 2 of a circuit-switched network, CS, comprising a communication server 3. The communication server 3 is associated to the MSC-S 2 (e.g. integrated into the MSC-S 2). The communication server 3, which could be a XMPP server, is adapted to register with a communication client 132 which can be a XMPP client over a client to server component 36. The XMPP client 132 is not shown in this figure. The client to server component 36 comprises a communication unit 361 , adapted to initiate or establish a connection to the XMPP client 132. The establishment of the connection could be initiated by the XMPP client 132 or by the XMPP server 3. The establishment of a communication means that the communication unit 361 helps to build-up a communication with the XMPP client 132. The client to server component 36 further comprises a receiving unit 362 which is adapted to receive identification information from the XMPP cl ient 1 32 via the connection . The identification information could be the Jabber ID or any other kind of identification, which is described in some of the next paragraphs. Further the client to server component 36 comprises an interrogation unit 363 wh ich is adapted to interrogate an authentication module 28 of the MSC-S 2 to perform a user authentication. The client to server component 36 further comprises a fetching unit 364, adapted to fetch subscriber information from a database 27. The database is in this embodiment the VLR of the MSC-S 2. A sending unit 365 at the client to server component 36 is adapted to send subscriber information to the XMPP client 132 via the connection. The connection could be a TCP connection.

In the following, some use cases are described in detail. The use cases below do not cover all XMPP capabilities but focuses on those use cases where MSC-S functions can be reused.

In a first use case, a XMPP client 132 which is implemented on a mobile phone or mobile terminal 18 wants to register at a XMPP server 3 which is associated to the MSC-S of a mobile communication network. It is not necessary that the mobile terminal is CS associated to this network. To register the XMPP client 132 at the XMPP server 3 the client 132 has to construct an identity which is called the Jabber identity. The Jabber ID looks like the following: "user@jabberserver.tld/device". The term "user" identifies the user of this service, "jabberserver" refers to the domain name of the XMPP server 3 and "device" represents the actual device the user is using for the registration request. The term "tld" stands for a top level domain which could be a .com or .de domain or any other known domain . A user may have several parallel registrations via different devices or different XMPP client instances on the same device.

To construct the Jabber ID, the XMPP client 132 could use information from the SIM card of the mobile phone 18. The subscriber identity module (SIM) card contains e.g. the MSISDN number or the IMSI which can be user by the XMPP client 132 to construct a "user" for the Jabber ID. The MSISDN number is the Mobile Subscriber Integrated Services Digital Network Number. The IMSI is the abbreviation for the International Mobile Subscriber Identity. The domain name can be derived from the GPRS domain name of the Access Point Name (APN) as defined and stored also on the SIM card. The device can be constructed from the International Mobile Equipment Identity (IMEI) of the mobile phone. The constructed Jabber ID may look like the following : IMSI@XMPP.APNdomain.com/IMEI.

Another option would be that the operator sends a configuration text message, e.g. a SMS message, to configure the XMPP client on the mobile phone 1 8. This option leaves more freedom in the way the Jabber ID is constructed. Subscribers can then be distributed to multiple domains or domains different to the APN domain.

To register the XMPP client 132 at the XMPP server 3 associated to the MSC- S 2, the XMPP client 132 opens a connection to the XMPP server 3 in the MSC-S 2. The mobile terminal 18 uses a normal packet switched connection. This connection can be based on the Transmission Control Protocol (TCP) and can be established via a wireless LAN connection of a WLAN router 19 through the Internet 100 to the c2s component 36 of the XMPP server 3. Another way of connecting the XMPP client 132 to the XMPP server 3 is an established radio connection to a packet core network. The SGSN 15 and the GGSN 16 route the TCP connection the c2s component 36 of the XMPP server 3. The c2s component 36 hand les this connection request and interrogates the GSM authentication module 28 of the MSC-S 2 to perform user authentication. The GSM authentication function 28 of the MSC-S 2 may have to retrieve authentication triplets from AUC via the home location register (HLR) 4. After successful authentication subscriber information is fetched from the database 27, e.g. the VLR, and the subscriber information is sent to the XMPP client 132 via the connection.

After the XMPP client 132 has been registered to the XMPP server 3 in the MSC-S 2, the mobile subscriber can start a chat session to any other already registered XMPP client. In case both cl ients are associated to the same XMPP server 3, the chat session is local to that XMPP server 3. The c2s component 36 receives chat related XMPP stanzas and will forward them to the XMPP session manager 34 via the XMPP stanzas router 35. The session manager 34 will determine whether the destination Jabber ID is currently available or offline.

Offline messages are stored in the VLR data storage 27 and will be delivered once the destination becomes available. If the destination JID is reachable, the session manager 34 forwards the message to the destination, via the stanzas router 35 and the responsible c2s instance of function 36.

The session manager 34 stays in control of the entire chat session. The session manager could report information about the chat session to the charging function 24 in the MSC-S 2. The operator is now able to charge e.g. duration of the chat, or the number of chat messages. It is also possible (not shown in the figures) to report the details of the chat session to a legal interception point.

In case the destination Jabber ID is not registered at the same local XMPP server 3, the XMPP session manager 34 tries to route the chat message to the destination XMPP server. This is done via the XMPP stanzas router 35 and the s2s component 33. The s2s component 33 reuses the existing IP core network interface 25 of the MSC-S 2. Also the same routing functional component 26 of the MSC-S 2 is reused in order to resolve the destination address and determine the appropriate physical core network interface. Also in this case charging information is collected and provided to the charging function 24, and legal interception, if applicable, can be performed.

Similar actions are performed if a remote XMPP client wants to reach the local associated XMPP client 132. In th is case the message arrives at a core network interface 25 of the MSC-S 2. The routing function 26 determines that this message is targeted to the internal XMPP server 3 and forwards the message to the s2s component 33, which forwards it via the XMPP stanzas router 35 to the XMPP session manager 34. In the context of XMPP, a Jingle call is handled in the same way as a chat session. A Jingle call is a peer-to-peer call between XMPP clients, where the negotiation occurs over the XMPP signalling channel and the med ia is exchanged over a data channel that is usual ly a ded icated non-XMPP transport channel. Therefore a Jingle call can also be termed as a Voice over IP call. Further information about the Jingle call is mentioned in the XMPP standard XEP-0166. The user plane details are negotiated end-to-end via the XM PP server, without XM PP server involvement. Also the user plane addresses are exchanged directly between the XMPP clients. Therefore the above described use cases for local and remote chats are also applicable for this use case. This applies also for the direction from a remote client towards a local client. Also the data collection for input to the charging function in the MSC-S can be used . The legal interception of the user plane has to be performed by devices in the IP backbone, to mirror the IP packet flow between the clients. Offline correlation is required to relate the collected XMPP Jingle signalling information with the IP flows.

One essential benefit of the XMPP enabled MSC-S 2 is that it efficiently allows to provide interworking between XMPP clients using Jingle for call setup and the existing fixed or wireless telephony networks.

On the other hand the XMPP server 3 integrated in the MSC-S 2 shall be based as much as possible on existing definitions, in order to allow reuse of al ready available XM PP server 3 implementations (open source or commercial products). The XMPP-concept of XMPP server component- connections is used to interconnect the MSC-S parts with the XMPP server 3 to provide legacy network breakout.

The XMPP standard XEP-01 14 defines a Jabber Component Protocol. This protocol allows connecting external server components to a XMPP server 3. So the GSM Call Control function 23 of the MSC-S 2 uses this protocol to be connected to the XMPP server 3. When establishing the connection, the GSM Call Control function 23 registers a specific sub-domain of the XMPP server domain. Whenever the XMPP server 3 receives a stanza addressed with this registered sub-domain, the stanza will directly be routed by the stanzas router 35 to the external component GSM Call Control function 23.

For the interworking as such the Gateway Interaction according to the XMPP standard XEP-0100 provides additional information. E.g . when the XMPP client 132 wants to address an E.164 number in a Jingle call, it will use the following format: "E164Address@CSgateway.domain.com". The term "E164Address" is the telephone number in accordance with the E.164 standard of the ITU-T, "CSgateway" is the sub-domain registered by the GSM Call Control function 23 when connecting as a component to the XMPP server 3. The term "domain" would be the domain used by the operator for his XMPP service. When the GSM Call Control function 23 received the Jingle call request, it will decide based on a destination number analysis whether to route it to the core network interface 25 located in the MSC-S 2 or, if the destination is a mobile terminal 18 associated to the same MSC-S 2, terminate it locally.

XMPP clients can use the Service Discovery mechanism in accordance with the XMPP standard XEP-0030 to discover the telecom breakout service offered by the XMPP server 3 integrated in the MSC-S 2. In this scenario the existing charging and legal intercept mechanisms can be fully reused.

Instead of storing the XMPP Server related subscriber data into the VLR 27 allocated to the MSC-S 2, it also possible to store it into an external database. One important embodiment of an external database is the Common Usage Database (CUDB), which is also used in mobile networks to centralize all subscriber data . Access to the CU DB is done via H LR-front-ends in a backward compatible way. If a network deploys a front-end-central database approach it would also prefer to store the XMPP data into such CUDB. The XM PP server data can be stored and access e.g . using a Lightweight Directory Access Protocol (LDAP) or other commonly used database access protocols.

Fig. 7 shows another embodiment of the invention. A mobile terminal 71 1 comprises a CS client 713 which is adapted to establish a communication with a CS mobile commun ication network over a rad io network 1 7. I n th is embodiment the mobile terminal 71 1 is CS attached 723 over the CS client 71 3 to a mobile switching node 72, which can be a MSC-S. The mobile terminal 71 1 comprises further a communication client 712 which can be a XMPP client or any other instant messaging client which is connected via a XMPP access interface 724 with a communication server 721 which is in this embodiment a XMPP server. The XMPP server is associated to the MSC-S 72. A further MSC-S 73 exists which also comprises a XMPP server 731 with an XMPP access interface 734. A further XMPP server 76 is shown in this figure which might be a stand-alone server in the Internet. All XMPP servers 721 , 731 , 76 are connected with each other over their server to server (s2s) components 33 via a network (e.g. IP network). The MSC-S 72, 73 comprise a Dynamic Domain Name System (DNS) client 722, 732 which are connected to a Dynamic DNS server 74. The Dynamic DNS clients 722, 732 are also connected with other components inside the MSC-S 72, 73, especially to the integrated XMPP server 721 , 731 . The Dynamic DNS server 74 is further connected to the mobile terminal 71 1 and to the other XMPP server 76. A central database 75 is connected to the XMPP servers 721 , 731 . The central database 75, which could be the Home Location Register (HLR) of a mobile communication network, comprises subscriber related data which can be fetched by the XMPP servers 721 , 731 or the MSC-S 72, 73. Therefore the XMPP servers 721 , 731 in the different MSC-S 72, 73 are set-up in a way that they do not store subscriber specific data locally but use a central database 75 for dynamic and static data storage. By this it is ensured that any of the XMPP server 721 , 731 can handle any of the subscribers or mobile terminals 71 1 . On activation of the XMPP server instance 721 , 731 it fetches the needed data from the central database 75 and caches them locally (e.g. in the VLR or any other local database) or will always store and retrieve data from the central database 75 directly.

The mechanism how a XMPP client 712 finds its responsible server is by DNS resolving the own JID domain. Therefore the XMPP client fetches the address from the Dynamic DNS server 74. The same mechanism is used by external XMPP servers 76 from different domains to route terminating XMPP traffic between XMPP servers 721 , 76. In order to change the DNS resolution of the Jabber I D (J I D) domain according to the XMPP server allocation, dynamic DNS is used. To achieve th is, the central DNS server entity 74 is upgraded to support real-time dynamic change of the configuration of domain resolution to IP addresses. When a CS client 713 registers into a new MSC-S, e.g. via a location update procedure or an IMSI attach, the registration function in the MSC-S 72, 73 will determine the physical address of its integrated XMPP server 721 , 731 . This IP address information is then fed into the Dynamic DNS client 722, 732 in the MSC-S, which then updates the configuration of the Dynamic DNS Server 74 to match the domain of the XMPP client to the IP address resolution.

With th is dynamic storage of DNS information it is possible to move the responsible XMPP server 721 , 731 along with the serving MSC-S when the mobile terminal with the integrated XMPP client 712 and the CS client 713 roams between different locations. The responsible XMPP server 721 , 731 can therefore always uses the local VLR data, MSC-S configuration, local core network interfaces, charging relations and other MSC-S resources. It is assumed that every MSC-S 72, 73 have an XMPP server 721 , 731 integrated as mentioned before.