WO2009095532A1

WO2009095532A1 - Method, communication arrangement, server arrangement and computer program product for establishing a communication connection

Info

Publication number: WO2009095532A1
Application number: PCT/FI2009/050041
Authority: WO
Inventors: Henri KESKI-SIKKILÄ
Original assignee: Sesca Group Oy
Priority date: 2008-02-01
Filing date: 2009-01-19
Publication date: 2009-08-06
Also published as: FI20085088A0; FI20085088L

Abstract

The invention relates to a method for establishing a real-time, duplex virtual connection (220a, 220b) in a communication network, which comprises both packet-switched (10, 10a, 11, 12) and circuit-switched (23) communication networks. The invention also relates to a communication network arrangement to be utilized in the method and a computer program product to implement the method. A step of the method is activating by a terminal device (112, 113) of the subscriber A in the first packet-switched communication network (11) link information of a web page on a server (30) of the subscriber B in the second packet-switched communication network (12). By means of the activated link information, the subscriber A is connected to a server arrangement in a server (30) administered by the subscriber B, by which a duplex virtual connection is established from a unique communication network address of the first terminal device (112, 113) of the subscriber A in the first communication network to a unique communication network address of the second terminal device (24) of the subscriber B in the second communication network (23).

Description

METHOD, COMMUNICATION ARRANGEMENT, SERVER ARRANGEMENT AND COMPUTER PROGRAM PRODUCT FOR ESTABLISHING A COMMUNICATION CONNECTION

The present invention relates to a method, communication arrangement, server arrangement and a computer program product for establishing a duplex, virtual con- nection using real-time communication in a communication network, which comprises both packet-switched and circuit-switched communication networks. The method includes: activating, by the terminal device of subscriber A in a first packet-switched communication network, the link information of a web page on a server of subscriber B in a second packet-switched communication network, connect- ing the terminal device of subscriber A to a signaling proxy using the SIP protocol and administered by subscriber B, and informing subscriber A of the presence of subscriber B by the information of subscriber B retrieved from a presence server before the virtual connection is established.

Information exchange between people by electronic communication means has become more diversified along with the spreading use of the Internet and wireless communication means. People can communicate with each other by using various real-time communication means. Thereby the communication connection between people is formed at least partly by either a speech connection and/or a video connection. Alternatively, people can communicate with each other using non-real- time methods and equipment. In that case, the communication may comprise, for example, the use of e-mail or exchange of information by non-real-time communication means provided by the Internet. Examples of these are various discussion forums. The equipment used for information exchange in the above includes computers, laptops, palm computers or smart phones.

The utilized communication connections may be either circuit-switched, like the conventional telephone connections, or packet-switched, like data communications taking place via the Internet. The development trend is towards packet-switched forms of communication also for speech and/or in connection with live image transmission. However, packet-switched systems have their own restrictions on the implementation of real-time voice and image transmission.

The packet-switched networks used for data transmission, such as the Internet, require various elements connected to the network, which monitor and control the operation of the network. For example, a single user may connect to the Internet directly via a local Internet operator or some closed local area network. In both cases it is in the interest of the user to be able to prevent the access of non- desired users to the confidential information in the terminal device used by the user through the communication network used. Control or restriction of communications between the user and the communication network can be implemented by routers, network address translators, firewalls or virtual networks, for example.

The most frequently used data network, the Internet, also enables the creation of marketplaces utilizing various business methods. It is possible to create web pages in the Internet, through which different services and goods can be bought and sold. Information exchange through the web pages is mainly based on purchasing actions taking place by writing on the terminal device or otherwise through the op- eration of the terminal device without the need for duplex, real-time information exchange between the parties.

However, solutions are known in which the buyer of a service or a product may set up a duplex communication connection with the supplier of the service or goods through a link found on the web page of the supplier of the service or goods.

For example, the published application WO 00/41534 describes a communication system in which a server connected to a communication network controls the transmission of data between the buyer's and seller's computers. The party sending the message logs in to the recipient's website and selects the message delivery method that suits him and/or the recipient from among the message delivery methods found on the website of the other party. Selectable message delivery methods include sending an audio message and saving it in the recipient's computer, and sending a collect call request.

Published application WO 01/61530 discloses a system in which the buyer can set up a voice call from a suitable computer to the service person of the seller of a service or goods by activating a link found on the web page of the seller by a computer mouse or the like. As a result, the VoIP program (Voice over Internet Protocol) is loaded to the buyer's computer from an Internet server providing voice services in order to establish a voice connection. The supplier of the service or goods is also connected to the same server. The server presented in the telephone ser- vice according to the published application also includes the required telephone numbers used by the selling party. Between the described server and the conventional telephone network of the seller there are signal conversion means, by which the signals are converted between the Internet and the conventional telephone network. The system enables a VoIP call from the buyer's computer to the seller's conventional telephone as a collect call in the described communication network. One way of defining a connection in a packet-switched communication network is to utilize the SIP protocol (Session Initiation Protocol). The SIP protocol is standardized by IETF (Internet Engineering Task Force), and its standard number is RFC 2543. In the SIP protocol, the contact information/addresses of the parties are generally defined or presented in some other way than the conventional telephone number. The address of the recipient or user according to the SIP protocol is advantageously of the form: user@networklocation[parameters][additional information], i.e. it resembles the form of e-mail addresses. The SIP protocol also enables the utilization of various addresses that resemble e-mail addresses in the establishment of a voice connection via the data network.

However, different network elements that control and secure the operation of a packet-switched network make it more difficult to implement real-time services, such as voice transfer, utilizing the SIP protocol between two terminal devices connected to the network. Real-time communication of either one of the terminal devices may be made more difficult or entirely prevented by, for example, a firewall or network address translator between the terminal device and the packet- switched network.

A network address translator is commonly used between the Internet and the local area networks in order to save the limited address space of the IPv4 protocol. When a network address translator is used, it is not necessary to allocate a dedicated IPv4 address for each terminal device connected to the local area network. However, it is not possible to establish a communication connection to another communication network using the SIP protocol from networks in which network address translators are used. For example, in the case that in the system of the publication WO 01/61530 there is at some point of the network arrangement a network address translator or a firewall, the establishment of a real-time, duplex voice connection using the SIP protocol between the parties cannot be realized by the procedures described in the reference.

Fig. 1 shows schematically a prior art network arrangement. A local area network A, ref. 11 , is connected through a firewall/network address translator 1 11 to the core network 10 of the Internet via the IP network 10a of a local Internet service provider, by utilizing the communication connection 111a. Between the network

10a of the local Internet service provider and the core network 10 of the Internet there may be routers, network address translators and firewalls 1 10. In the exam- pie of Fig. 1 , the local area network includes two computers, 113 and 1 12. The computers may be connected to the local area network A by either wired or wireless connections 112a and 1 13a.

The local area network B, ref. 12, is also connected to the Internet 10 through a firewall/network address translator 121 by the connection 121a, either directly to the Internet core network 10 or through the network of a local Internet service provider. The server 122 of a service provider is connected to the local area network B by the connection 122a. The computer 123 also has a communication connection to the local area network B, ref. 12. The computer 123 can be used to carry out the measures related to the selling of the services and goods saleable from the server 30.

The firewalls, shown by way of example in Fig. 1 , are used to protect the computers connected to the local area networks from attacks potentially coming from outside the local area networks. When the network address translator 11 1 is used, it is not necessary to acquire a dedicated user address according to the IPv4 proto- col for each computer 112 and 114 of the local area network A.

In the example of Fig. 1 , if the computer 112 connected to the local area network A tries to establish a duplex communication channel adapted to real-time communication to server 122 in local area network B using the SIP protocol, for example, the firewalls and network address translators on the desired communication con- nection, references 1 10, 11 1 and 121 , do not allow the establishment of a realtime communication connection. Therefore, it is not possible to establish a voice connection from computer 112 to computer 123.

U.S. Patent No. 6980556 discloses a method by means of which the SIP protocol can be used even in networks that use firewalls and/or network address transla- tors. In the system presented in the patent, the SIP proxy, which utilizes the SIP protocol, is divided into two parts. One part of the SIP proxy operates in each terminal device of the local area network, and the other part of the SIP proxy operates in the server of the Internet service provider. By this arrangement, the firewall or network address translator can be bypassed by tunneling the communication connection in the connections according to the SIP protocol from the SIP server operation of a single terminal device to the SIP proxy of the Internet service provider. However, the utilization of the solution described in the patent requires the installation of a separate SIP proxy application in each terminal device utilizing the method. An object of the invention is to provide a communication arrangement and a method by which it is possible, by using a link found on a web page, to establish a real-time, duplex communication connection between two terminal devices connected to a packet-switched communication network, the terminal devices of sub- scriber A and subscriber B, although the packet-switched network used comprises a plurality of packet-switched networks connected to each other, which may comprise routers, firewalls and network address translators. The communication connection may be used to transfer, for example, voice and/or image, presence information of the parties and instant messages in text form.

The objects of the invention are achieved by an arrangement and a method in which the opening of a link on a web page starts a process by which the requested real-time, duplex communication connection is tunneled between two interfaces of the communication network belonging to the communication connection by server means on the server of the service provider. By utilizing the arrangement, the ter- minal device of subscriber A can be connected unambiguously to one of the interfaces formed by tunneling, and the terminal device of subscriber B unambiguously to the other one of the formed interfaces. A duplex, virtual connection has thus been established between the interfaces.

The method according to the invention has the advantage that from the link on the web page it is possible to establish a real-time communication connection over the packet-switched network using the SIP protocol, although there are elements in the network that restrict communication.

In addition, the invention has the advantage that from the link on the web page it is possible to open a duplex voice or video connection between two terminal devices.

Furthermore, the invention has the advantage that from the link on the web page it is possible to transmit presence information and instant messages in text form between the terminal devices.

The invention also has the advantage that the receiving party can be given a piece of information that indicates from which link of the web page the establishment of the communication connection was started.

In addition, the invention has the advantage that in a packet-switched core network there is no need for a separate server to carry out the conversion of the address information used by the packet-switched network and the telephone network when moving from one network to another. The method according to the invention for establishing a duplex communication connection using real-time data transmission in a communication network comprising both packet-switched and circuit-switched communication networks is characterized in that in order to accomplish a real-time, duplex communication connec- tion:

- a virtual connection is established from the unique communication network address of subscriber A in the first communication network to a unique communication network address of subscriber B in the second communication network, and

- the terminal device of subscriber A is connected to a switching point belonging to the virtual connection in the first communication network, and the terminal device of subscriber B is connected to a second switching point of the same virtual connection in the second communication network.

The communication network arrangement according to the invention, in which a duplex communication connection using real-time data transmission is established in a communication network between subscriber A and subscriber B, which communication network arrangement comprises both circuit-switched and packet- switched communication networks, is characterized in that a virtual connection is arranged to be established on a server arrangement administered by subscriber B from a unique communication network address of the first terminal device of sub- scriber A in the first communication network to the unique communication network address of the second terminal device of subscriber B in the second communication network.

The server arrangement according to the invention for establishing a real-time, duplex, virtual connection between subscriber A and subscriber B, is characte- rized in that it comprises:

- a component server for providing a customer web page to the terminal device of subscriber A

- a signaling proxy for switching a virtual connection between the terminal device of subscriber A and the terminal device of subscriber B - a tunneling server for by-passing the firewalls on the virtual connection to be created between the terminal device of subscriber A and subscriber B

- a media proxy for by-passing the network address translators on the virtual connection to be created between the terminal device of subscriber A and subscriber B, and - a presence server for informing the terminal device of subscriber A of the capability of subscriber B to become switched to the virtual connection to be created. The computer program product according to the invention is characterized in that it comprises computer program code means, the execution of which in a computer is arranged to implement a server arrangement, by which a real-time, duplex virtual connection can be established between subscriber A and subscriber B in a com- munication network, which comprises both packet-switched and circuit-switched communication networks.

Some preferred embodiments of the invention are presented in the dependent claims.

The basic idea of the invention is the following: A packet-switched network com- prises a group of communication servers of the service provider, including media and signaling proxies and a component, tunneling and presence server for establishing real-time, duplex communication connections. The duplex communication connection to be established by the group of communication servers may advantageously comprise a voice and/or video connection, presence information of the parties and instant messages in text form. When establishing a connection between the terminal devices participating in the communication, the signaling proxy advantageously uses the SIP protocol. If there are firewalls and/or network address translators on the communication connection to be established, the tunneling server or media server belonging to the group of communication servers es- tablishes a tunneled connection between two network elements, which are such that subscriber A can be connected to one of them by one, permanent address identifier and subscriber B to the other by its own, permanent network identifier. The desired real-time, duplex communication connection between subscriber A and subscriber B can be realized through the created tunnel.

In the following, the invention will be described in more detail. Reference will be made to the accompanying drawings, in which

Fig. 1 shows an example of the structure of a prior art packet-switched network,

Figure 2a shows an example of an arrangement which enables non-real-time communication in the communication arrangement according to the invention,

Figure 2b shows an example of an arrangement which enables real-time, duplex communication in the communication arrangement according to the invention, Fig. 3 presents a server arrangement utilized in the communication arrangement according to the invention by way of example, and

Fig. 4 presents a flow chart of the main steps of creating a communication arrangement according to the invention by way of example.

Figure 1 was explained in connection with the description of the prior art.

The establishment of a real-time, duplex communication connection according to the invention in a communication network including at least one packet-switched communication network is schematically illustrated in Figures 2a and 2b. The exemplary communication network of Figures 2a and 2b includes all the elements of the communication network arrangement shown in connection with Fig. 1. In addition, the examples of Figures 2a and 2b show a circuit-switched telecommunication network 23, which is connected by a gateway 230 to the packet-switched core network. Through the gateway 230 it is possible to transmit VoIP voice connections between the Internet 10 and the telecommunication network 23.

The telecommunication network 23 may be either a prior art wired telephone network or a cellular telephone network. In both cases, the telephone 24 connected to the telecommunication network 23 has been assigned a unique telephone number. The connection 231 to the telecommunication network 23 may be either a wired or wireless communication connection.

In the examples of Figures 2a and 2b, reference number 20 denotes that in addition to the computer 123, the telephone 24 can be utilized in the administration and control of the services obtained from the server 30. In the examples of Figures 2a and 2b, the computer 123 and the telephone 24 connected to the telecommunication network 23 are advantageously used by a person employed by the service provider. That would enable the service provider to provide simultaneously by one person both data services from the server 30 and telephone service by the telephone 24.

In the situation of Fig. 2a, the exemplary subscriber A has established a connection to the local area network A by the computer 113, reference 11. The computer 113 advantageously comprises a microphone and a loudspeaker, which can be utilized on the voice connection to be established. The accessories of the computer 1 13 may also include a video camera. The local area network A is connected through the local area network 10a of a local service provider to the Internet 10. Another exemplary local area network B, reference 12, is also connected to the In- ternet 10. The server 30 of the service provider is connected to this local area network B. The computer 123 using the server 30 is also connected to the local area network B. A packet-switched communication connection 210 to the server 30 can be created by prior art procedures from the computer 113. The computer 123 may also comprise a microphone, loudspeaker and a video camera.

In the example of Fig. 2a, the communication connection 210 has three separate elements, 110, 111 and 121 , which connect the packet-switched networks 11 , 10, 10a and 12. They can be, for example, firewalls, routers or network address translators or combinations thereof. Non-real-time communication between the com- puter 1 13 and the server 30 runs on the packet-switched communication connection 210 through said elements that connect the communication networks described above.

For example, through the packet-switched connection 210, a web page on the server 30 can be opened by the computer 1 13. The opened web page may con- tain a link which, according to the invention, starts the establishment of a real-time, duplex communication connection 220a or 220b using the SIP protocol between the computer 113 and the telephone 24 or computer 123 used by a service employee of the service provider.

The establishment of a voice connection 220a according to the invention, shown in Fig. 2b, is managed by a communication server arrangement 300 included in the server 30 (which is shown in Fig. 3). It is used for tunneling a real-time communication connection 220a from the local area network A to the telecommunication network 23. For creating the tunnel, http (Hypertext Transfer Protocol) or https (Hypertext Transfer Protocol Secure) is advantageously utilized. One end point of the created tunnel 220a is located in the network element 111 on its interface that is visible to the local area network A. In the local area network A, a unique, unchangeable network address has been defined for the computer 113. The other end point of the tunnel is on the interface on the side of the telecommunication network 23 of the gateway 230 connecting the telecommunication network to the Internet 10. In the telecommunication network 23 each telephone 24 has an unambiguously defined network identifier. In the procedure according to the invention, a tunnel is formed between these two interfaces, after which real-time, duplex communication is possible between the computer 113 and the telephone 24.

If the computer 123 used by the service provider comprises a microphone and a loudspeaker, the communication connection can be tunneled, instead of the tele- communication network 23, to the element 121 separating the local area network B from the Internet 10, i.e. to the interface of the element 121 visible to the local area network B. Because the computer 123 has a unique network address in the local area network B, a real-time, duplex communication connection can be estab- lished between the computers 113 and 123. It may comprise, for example, a voice connection and/or real-time presentation of a message written in real time.

The starting of the establishment of a communication connection by the opening of a web page by subscriber A has been described above. The establishment of a communication connection according to the invention can advantageously also be started by a link included in an e-mail message or a text document, for example. After the activation of the link, the web page of the service provider opens in the manner described above, and the creation of the tunnel for data transmission takes place in the manner described above.

Fig. 3 shows, by way of example, a communication server arrangement 300 ac- cording to the invention, and the way that subscriber A and subscriber B are connected to it when a communication connection according to the invention is established.

Subscriber A opens with his terminal device 113 the web page of the service provider from the server 30. The opened web page 310 also comprises a link, by which the establishment of a duplex communication connection can be started. The link, which is found on the web page of the service provider, includes the URL address (Uniform Resource Locator) of a component server 301 according to the invention.

When a link on the web page 310 of the service provider (subscriber B) is acti- vated by the terminal device 113 of subscriber A, the component server 301 sends to the computer 113, which requested the establishment of the connection, a customer web page, which is utilized in the establishment of the SIP communication connection. By means of the information of the customer web page, the computer of subscriber A starts the establishment of a communication connection to the sig- naling proxy 302, using the SIP protocol. If a firewall or firewalls exist(s) between the computer 113 and the signaling proxy 302, they are detected, and a tunneled, virtual, duplex communication connection is built between them by a tunneling server 304 belonging to the communication server arrangement 300 using advantageously either the http or https protocol. If a firewall or firewalls or a network gateway 230 belonging to the telecommunication network also exist(s) between the terminal device 24 of subscriber B and the signaling proxy 302, another duplex tunnel is created between the gateway 230 of the telecommunication network 23 and the signaling proxy 302 by the tunneling server 304.

The communication server arrangement 300 advantageously also comprises a presence server 305. The presence server transmits information about the presence of subscriber B to subscriber A during the establishment of the connection. If the presence information indicates that subscriber B is capable of real-time, dup- lex communication, communication between subscriber A and subscriber B can be started. On the basis of the information delivered by the presence server, subscriber A can make the decision on whether to try a voice connection or whether some other real-time manner of communication is possible.

When both subscribers are at the ends of a duplex tunneled, duplex communica- tion connection and subscriber B is capable of real-time communication, communication can be started between the terminal devices of subscriber A and subscriber B. The RTP protocol (Real Time Protocol) or the SRTP protocol (Secure Real Time Protocol), for example, can be used in the communication.

In an advantageous embodiment of the invention, the SIP protocol is used in con- nection with the establishment of the communication connection to send information concerning the subject of the call of subscriber A to the receiving subscriber B by an instant message. The content of the instant message may be text, which is shown to the receiving subscriber B. The content may advantageously also be an URL, which is opened to the display of the telephone or the network browser of the receiving party B. The message may also comprise a parameter, to which the terminal device of the receiving party B reacts in a predetermined manner.

For example, if the party B is a travel agency, on the web pages of which there is a link connected to the travel destination, the activation of the link by subscriber A may start a VoIP applet, which sends the URL parameters related to the travel destination to subscriber A. The applet also starts a call to the customer service of the travel agency and sends the URL to the terminal device of the customer service employee of the travel agency, which advantageously opens a web page corresponding to the URL. Thus the customer service employee of the travel agency knows at once for which travel destination the caller has contacted the travel agency. In an advantageous embodiment of the invention, the terminal device of the customer service employee of the travel agency opens the reservation system with the information of the travel destination.

If either or both of the terminal devices connected to the communication connec- tion are behind a network address translator, the media proxy 303 belonging to the communication server arrangement 300 detects the situation. In this case, the media proxy 303 is directed to manage the traffic according to the RTP protocol past the network address translators.

The above described servers 301-305 belonging to the communication server ar- rangement can advantageously be implemented as computer programs saved in the memory of one or more computers 30. Then any one of the server functions described above can be realized by executing a computer program corresponding to the server function in the computer processor.

Fig. 4 is an exemplary flow chart of the main steps of the establishment of a com- munication connection according to the invention. In step 40, subscriber A opens with his terminal device 113 a web page on the server 30 of subscriber B. In step

41 , subscriber A activates the URL address of a component server found on the web page of subscriber B. When the activation has taken place, the component server 301 belonging to the communication server arrangement 300 sends to the terminal device 123 of subscriber A a customer web page, which contains the URL address of a signaling server belonging to the communication server arrangement

300.

In step 42, it is checked if there is a firewall between subscriber A and the signaling proxy 302 that would prevent using the SIP protocol. If no firewall is detected, a connection between the terminal device 123 and the signaling proxy 302 is opened in step 44 using the SIP protocol.

If at least one firewall is found in step 42 between subscriber A and the signaling proxy 302, in that case a connection to the signaling proxy 302 is opened for subscriber A through the tunneling server 304 in step 43, using the SIP protocol.

In step 44, the functionality included in the customer web page connects the terminal device of subscriber A to the signaling proxy 302. The communication connection to the signaling proxy 302 has thus been established by using the SIP protocol. In step 45, the presence server 305 belonging to the communication server arrangement 300 informs subscriber A of the possibility of subscriber B to connect to a real-time, duplex communication connection. On the basis of the information received, subscriber A makes the decision as to in what way to try the communica- tion connection to subscriber B in step 46.

At the same time, it is advantageously also possible to inform subscriber B with an instant message as to through which web link subscriber A has started the establishment of the communication connection. The terminal device of subscriber B can utilize this message by retrieving, already when the link is being established, information related to the web link for the use of subscriber B.

When the decision on the establishment of the communication connection has been made, it is checked in step 47 if the communication connection to be established to subscriber B contains network address translators, which would prevent the establishment of a real-time, duplex communication connection. If at least one network address translator is detected, in that case the connection between subscriber A and subscriber B is established through the media proxy 303 belonging to the communication server arrangement 300.

In step 49, a duplex virtual connection has been tunneled from the unique network address of the terminal device 113 of subscriber A to the unique network address of the terminal device 24 of subscriber B. After this, real-time, duplex communication can be started between the terminal devices of subscriber A and subscriber B.

Some preferred embodiments of the method and communication arrangement according to the invention have been described above. The invention is not limited to the solutions described above, but the inventive idea can be applied in numerous ways within the scope defined by the claims.

Claims

1. A method for establishing a duplex communication connection (220a, 220b) using real-time data transmission in a communication network, which comprises both packet-switched (10, 10a, 1 1 , 12) and circuit-switched (23) communication networks, which method comprises:

- activating (40, 41 ) with a terminal device (112, 113) of a subscriber A in a first packet-switched network (11 ) a link information of a web page on a server (30) of a subscriber B in a second packet-switched communication network (12)

- connecting (42, 44) the terminal device (1 12, 113) of the subscriber A to a sig- naling proxy (302) administered by subscriber B and using the SIP protocol, and

- informing (45) the subscriber A of the presence of the subscriber B by information of the subscriber B retrieved from the presence server (305), characterized in that in order to accomplish the real-time, duplex communication connection (220a, 220b): - a virtual connection (220a, 220b) is established from a communication network address of the subscriber A, belonging to the first communication network (11 ) and unique in the first communication network to a communication network address of subscriber B in the second communication network (12) and unique in the second communication network, and - the terminal device of the subscriber A (1 12, 113) is connected (46, 47, 49) to a switching point in the first communication network (11 ) and belonging to the virtual connection, and the terminal device of subscriber B (24) is connected to another switching point of the same virtual connection in the second communication network (23).

2. The method according to Claim 1 , characterized in that the terminal device (1 12, 113) of subscriber A is connected to the signaling proxy (302) through (43) a tunneling server (304) if there is a firewall (110, 11 1 , 121 ) between the terminal device (1 12, 113) of subscriber A and the signaling proxy (304).

3. The method according to Claim 1 or 2, characterized in that the terminal de- vice of subscriber B (24, 123) is connected to the signaling proxy (302) through the tunneling server (304) if there is a firewall between the terminal device (24, 123) of subscriber B and the signaling proxy (302).

4. The method according to Claim 1 , characterized in that if there is at least one network address translator (110, 111 ) in the communication connection (220a, 220b) to be established between the terminal device (112, 113) of subscriber A and the terminal device (24, 123) of subscriber B, the communication connection (220a, 220B) is directed to run through the media proxy (303).

5. The method according to Claim 1 , characterized in that the information about a link information of a web page activated by the subscriber A is also trans- mitted to the terminal device (24, 123) of subscriber B.

6. The method according to Claim 5, characterized in that the web link transmitted to the terminal device (24, 123) of the subscriber B is opened to the display of the terminal device.

7. A communication network arrangement for establishing a duplex communica- tion connection (220a, 220b) using real-time data transmission in a communication network, which comprises:

- at least one packet-switched communication network (10, 10a, 11 , 12)

- at least one circuit-switched communication network (23)

- a first terminal device (1 12, 113) of a subscriber A connected to a packet- switched communication network (11 )

- a second terminal device (24) of a subscriber B connected to a communication network (23) supporting real-time communication, and

- a server arrangement (30) of the subscriber B, connected to the second packet- switched communication network, characterized in that a virtual connection (220a, 220b) is configured to be created by the server arrangement (30) from a communication network address of the first terminal device of the subscriber A (112, 1 13), unique in the first communication network (11 ), to a communication network address of the second terminal device of the subscriber B (24), unique in the second communication network.

8. The communication network arrangement according to Claim 7, characterized in that a component server (301 ) belonging to the server arrangement (30) is configured to provide a customer web page to the terminal device of the subscriber A for establishing a virtual connection (220a, 220b).

9. The communication network arrangement according to Claim 8, characte- rized in that the component server (301 ) belonging to the server arrangement (30) is also arranged to provide to the terminal device of the subscriber B (24, 123) information about a link information included in the web page activated by subscriber A.

10. The communication network arrangement according to Claim 8, characterized in that a signaling proxy (302) belonging to the server arrangement (30) is configured to switch a virtual connection (220a, 220b) between the terminal device of the subscriber A (1 12, 1 13) and the terminal device of the subscriber B (24, 123).

11. The communication network arrangement according to Claim 10, characterized in that a tunneling server (304) belonging to the server arrangement (30) is configured to by-pass firewalls (110, 1 11 ) on the virtual connection (220a, 220b) to be created between the terminal device of the subscriber A and the terminal de- vice of the subscriber B.

12. The communication network arrangement according to Claim 11 , characterized in that a media proxy (303) belonging to the server arrangement (30) is configured to by-pass network address translators (110, 111 , 230) on the virtual connection (220a, 220b) to be created between the terminal device of the subscriber A and the terminal device of the subscriber B.

13. The communication network arrangement according to Claim 12, characterized in that a presence server (305) belonging to the server arrangement (30) is configured to inform the terminal device of the subscriber A (1 12, 113) of the capability of the terminal device of the subscriber B to become switched to the virtual connection (220a, 220b) to be established.

14. A server arrangement (300) for establishing a real-time, duplex virtual connection (220a, 220b), characterized in that it comprises:

-- a component server (301 ) for providing a customer web page to a terminal device of a subscriber A - a signaling proxy (302) for switching a virtual connection (220a, 220b) between the terminal device of the subscriber A (1 12, 113) and a terminal device of a subscriber B (24, 123).

- a tunneling server (304) for by-passing firewalls (110, 1 11 ) on the virtual connection (220a, 220b) to be created between the terminal device of the subscriber A and the subscriber B

- a media proxy (303) for by-passing network address translators (110, 11 1 , 230) on the virtual connection (220a, 220b) to be created between the terminal device of the subscriber A and the terminal device of the subscriber B, and - a presence server (305) for informing the terminal device of the subscriber A (112, 1 13) about the capability of the terminal device of the subscriber B to become switched to the virtual connection (220a, 220b) to be created.

15. A computer program product, characterized in that it comprises computer program code means stored on a computer-readable storage medium, which code means are configured to implement the functions of the servers (301-305) of a server arrangement (300) defined in Claim 15 when said program is executed in a computer (30).