WO2001089154A1

WO2001089154A1 - Transmitting data via broadcast network

Info

Publication number: WO2001089154A1
Application number: PCT/FI2001/000488
Authority: WO
Inventors: Risto Mäkipää
Original assignee: Domiras Oy
Priority date: 2000-05-19
Filing date: 2001-05-18
Publication date: 2001-11-22
Also published as: AU2001262374A1; FI20001212A

Abstract

The invention relates to transmitting datagrams from a service or content provider (S1, S2) to a terminal (TE1, TE2) of a client via a broadcast service (DVB). The idea underlying the invention is that a digital broadcast service is provided with a dedicated data network address. The datagrams routed from a public data network to this address are broadcast to the terminal. The network address may refer to an application of a server (6) connected to the broadcast service which receives the datagrams and stores them in a database (5) of the server serving as a buffer memory of the broadcast service. From the buffer memory, transmission equipment (4) retrieves datagrams to be transmitted to the terminals (TE1, TE2).

Description

TRANSMITTING DATA VIA BROADCAST NETWORK

FIELD OF THE INVENTION

[0001] The invention relates to delivering data from a service or content provider to a terminal of a client via a broadcast service.

BACKGROUND OF THE INVENTION

[0002] New digital broadcast networks have been developed all over the world for delivering radio and television broadcasts. Such networks include e.g. a digital radio network called digital audio broadcasting DAB and a digital television network called digital video broadcasting DVB. Although these networks are mainly responsible for radio and television broadcast, they could also possibly be used for transmitting different data services to clients. European Telecommunications Standards Institute ETSI, for example, has in standard EN 301192 v1.2.1 specified how a DVB system can be used for broadcasting various data to clients. Examples of data broadcasting include downloading software via satellite, cable or terrestrial links, transmitting Internet services via broadcast channels (IP tunnelling), interactive television and other interactive services. The bidirectional, interactive services of the DAB and DVB systems enable e.g. subscribing to chargeable services or transmitting feedback information on a service from a network terminal. Such interac- tive services include e.g. e-commerce, different games and video-on-demand services. This requires that the terminal also comprises means for transmitting data on a return connection, i.e. transmitting data to a broadcast network. Typically, a terminal is then provided with a wired connection to a fixed network, such as a public switched telephone network PSTN, from which a further connection is arranged to a DAB or DVB network or to a server of a service provider. The return connection can also be arranged using a cable or a wireless connection, such as a wireless local area network or a mobile communication network.

[0003] The return connection enables different information, which can be any data, to be selected to be broadcast. Typically, the image or voice information to be broadcast is obtained from the servers of the network of the service provider, such as a television company. The return connection, however, also enables communication with other telecommunication networks, such as networks connected to the Internet, and information to be broadcast to be selected from these other networks. Since the number of subnetworks and servers connected to the Internet is enormous, it is possible for a user to search for information of extremely different kinds via the Internet. The capacity of broadcasts is high, particularly in comparison to wireless mobile communication systems, e.g. in terrestrial DVB broadcasts as high as 22 Mbit/s per multiplex. A terminal can thus access different servers via the Internet and, utilizing a high-speed broadcast, receive data from the servers. This corresponds to the asymmetric channel structure of the third generation mobile communication systems wherein the data transmission capacity from a base transceiver station to a terminal is considerably higher than from the terminal to the base transceiver station. A forward channel is now arranged through a broadcast network and a reverse channel (return channel) through a telecommunication network. The terminal must then be an integrated terminal capable of operating in both of these networks. Such a terminal is often called a multi- mode device or a hybrid terminal. For example, an extension card connected to a personal computer PC enables digital broadcast services, such as digital radio transmissions called digital audio broadcasting DAB or digital television transmissions called digital video broadcasting DVB, to be received. The terminal to receive broadcasts can be e.g. a "set-top box" STB. The STB device enables digital broadcasts or Internet services to be received by the existing analogue TV and radio receivers. In both cases, the return connection can be arranged e.g. as a modem, ISDN or data connection e.g. via a public switched telephone network PSTN or a mobile communication network, such as a public land mobile network PLMN.

[0004] The Internet is a combination of numerous networks, which supports transport control protocol/Internet protocol TCP/IP based applications, such as the world wide web WWW, simple message transport protocol SMTP, e-mail or file transfer protocol FTP. The parts of the Internet are often called subnetworks that are interconnected by gateways or routers. Computers connected to a network are called hosts. One host computer is often a cli- ent while another is a server. A client is a computer which requests for or receives services from another computer in the network. A server is a computer which provides services for other computers in the network.

[0005] A network layer, or an Internet layer, is a layer in which the IP protocol provides logical, equipment-independent address processing to enable data to be transmitted from one subnetwork to another although a different technique were used in the lower layers of the subnetworks. The IP protocol is a packet-switched protocol which is mainly responsible for routing IP packets over the Internet to their final destination and for informing the destination of the source. Therefore, a header of an IP packet comprises an IP source address and an IP destination address to unambiguously identify the original source and the final destination. The source and destination addresses remain unchanged when the IP packet travels from the source to the destination. The TCP/IP networks use 32-bit addresses to identify the host computer and the network to which the host is connected. In other words, the IP address comprises the address of the network and the address of the host. [0006] A transport layer lies between a network and applications in the application layer. The most important protocols of the transport layer are a transport control protocol TCP and a user datagram protocol UDP, which enable a particular application to be arranged as the address of the data in the IP packets. To be more precise, the applications are connected to TCP and UDP protocol modules through "ports", each port being provided with a unique number. The ports are fixedly allocated to certain popular client/server applications at the server end, and the allocation is standardized to cover the entire Internet. Such ports are called well-known ports, and they enable a service application being compelled to advertise its port number before communicat- ing to be avoided. When a client transmits an IP packet, it simply enters the known port number of the destination application (server) into the destination port field of the UDP or TCP header and the free, unknown port number of the client into the source port field. When the server receives the first packet, the server is thus informed of the port number associated with the client applica- tion. The different traffic streams of the end applications communicating with each other can thus be separated from each other using a combination of five different identifiers; IP source address, source port, IP destination address, destination port and transport layer protocol (TCP, UDP). In connection with ports also sockets are usually mentioned. A socket is an address which is formed by combining an IP address and a port number. For example, socket 111.121.131.141.80 refers to port 80 of a computer whose IP address is 111.121.131.141. A socket address is thus an unambiguous identifier of an application operating on a server.

[0007] As becomes apparent from what has been disclosed above, a basic characteristic of an IP network is that when a server receives a service request, the server transmits datagrams relating to the reply to the source ad- dress contained in the service request. In the case of a hybrid terminal, the sen/ice request is supplied via the telecommunication network providing the return channel, and, typically, the network address of the IP address of the terminal also refers to this IP subnetwork. The response datagrams transmit- ted by the server comprise the IP address of the terminal as the destination address. In the usual operation of the IP network, also the response datagrams are routed to the subnetwork indicated by the IP address, i.e. to the network providing the return channel. Each service should, however, be routed to the terminal via a unidirectional broadcast network, i.e. the datagrams should be directed to routers routing the datagrams to the broadcast network.

DISCLOSURE OF THE INVENTION

[0008] An object of the invention is to enable datagrams to be routed in the forward direction to a receiver via a broadcast network.

[0009] The objects of the invention are achieved by a method and a system which are characterized by what is disclosed in the independent claims. Preferred embodiments of the invention are disclosed in the dependent claims.

[0010] The idea underlying the invention is that a digital broadcast sen/ice is provided with a dedicated data network address such that the data- grams routed from a public data network to this address are broadcast to the terminals. In a first preferred embodiment of the invention, a network address refers to the application of a server connected to the broadcast service which receives the datagrams and stores them in a directory or another memory of the server serving as a buffer memory of the broadcast service. From this buffer memory, the transmission equipment retrieves datagrams to be transmitted to the terminals. The broadcast server may receive datagrams from many sources, in which case the server stores the datagrams and the transmission equipment transmits the datagrams in an order according to a suitable criterion, typically in the order in which the datagrams are stored in the buffer memory.

[0011] In an embodiment of the invention, datagrams received by the broadcast server comprise the data network address of the content or sen/ice provider selected by the terminal as the source address, said data network address of the broadcast service as the destination address, and the data network address of the terminal as additional information. The broadcast server (or more generally, the transmission equipment) is then arranged to change the destination address of the datagrams to said data network address of the terminal before the datagrams are stored in the buffer memory or before the datagrams are broadcast. In another embodiment of the invention, the datagrams received by the broadcast server comprise the data network address of said broadcast service as the destination address and, encapsulated into a payload field, datagrams to be transmitted to the terminal. These encapsulated datagrams comprise the data network address of the terminal as the destination address. The broadcast server then decapsulates the datagrams and stores them in the buffer memory of the transmission equipment.

[0012] Many different ways exist in which said address can be transmitted to the user, terminal or content server. In an embodiment of the invention, said data network address is broadcast to the terminals as service information on the broadcast service. In the DVB standard, the data network address can be included e.g. in a service description table SDT. The SDT describes a service multiplexed to the DVB signal as a dedicated DVB transport stream. An Internet broadcast service can be implemented by multiplexing the service in many different ways also to be part of the transport stream transmitting other services, but most commonly, a unique transport stream for data broadcast services is used since it is the preferred use as far as dynamic use of capacity left over from program services for data services is concerned. The type and content of the service are specified at the SDT. In a preferred embodiment of the invention, a "linkage descriptor", i.e. a standardized description of additional information being linked to the service, can be added to the SDT. Types of information that can be linked to the service have been standardized using numerical values. Free numerical values are available, however, and one of them can be reserved to describe the data network address of the broadcast service. A linkage descriptor enables the data network address to be unambiguously associated with the service presented according to the DVB standard in the frame information. This is the simplest way to ensure a correct address to be used for each broadcast service and automation of the functions of the invention to be achieved. If, for example, district or local transmitters are used for broadcasting, the terminal or the user always receives a correct address without needing to know the transmitter in the area of which the terminal or the user is located. If a forward broadcast service is implemented as a subtransmission network, wherein subtransmitters do not transmit their own service information, the data network addresses of the broadcast service can be transmitted e.g. as an IP multicast service via a sub- transmitter. Another implementation of the distribution of the data network addresses of the subtransmitters is to also attach geographical coordinates to the service information to enable each subtransmitter and a corresponding data network address to be linked to each other. When requesting for a service, the terminal or user can transmit said data network address to the server of the content or service provider, which then transmits, using this network address, the datagrams of the service to the broadcast server in question. [0013] The invention provides a simple way to deliver datagrams to a terminal from any content or service provider server or other source via any broadcast service, using e.g. the usual routing mechanisms of an IP network. In other words, a user can choose both the source of a service and the broadcast service to be used for the delivery freely and independently of each other.

BRIEF DESCRIPTION OF THE DRAWINGS

[0014] The invention is now described in closer detail in connection with the preferred embodiments and with reference to the accompanying drawings, in which

[0015] Figure 1 illustrates an embodiment of the invention wherein the broadcast network is a DVB network, the source of datagrams is an Internet server and the return channel is arranged via a PSTN, ISDN or PLMN network.

[0016] Figure 2 is a signalling diagram illustrating datagram transmission of the invention, [0017] Figure 3 illustrates a service request,

[0018] Figures 4A and 4B illustrate a service datagram and a tunnelling datagram of an embodiment of the invention, and

[0019] Figures 5A and 5B illustrate a service datagram and a modified service datagram of another embodiment of the invention.

DETAILED DESCRIPTION OF THE INVENTION

[0020] In the following, the invention will be described using a digital television system with a digital video broadcasting DVB standard being applied thereto as an example. According to the invention, transmission of information as a broadcast to a terminal TE via a network BN can be implemented using any broadcasting technique according to prior art technology known per se. Other important broadcasting standards include digital audio broadcasting DAB and advanced television systems committee ATSC. Furthermore, a broadcast can be implemented as a satellite transmission, terrestrial transmission or cable transmission. [0021] In Figure 1 , the terminal TE receives broadcasts from a DVB distribution network. For the sake of clarity, in Figure 1 the DVB distribution network only comprises a transmission mast 3, transmission equipment (Tx) 4, a database (DB) 5 serving as a buffer memory, and a DVB server 6. Typically, a broadcast comprises information on services and programs to be selected by a user, which is presented using an electronic programming guide EPG. The information is preferably shown on the terminal TE by means of a browser-type user interface wherein different information sources are linked (cf. hyperlinks in a WWW browser).The information can be divided into services which do not require a return connection to be set up and into services which do require a return connection to be set up. A return connection must also be set up if the user wishes to receive services from other sources than from the network of the operator providing broadcast services.

[0022] When the user wishes to affect the broadcast services to be transmitted, a return connection can be set up from the terminal TE to the network of the operator providing broadcast services. The user may e.g. desire a certain program to be transmitted from the DVB network or, on the other hand, the user may wish to transmit information from a server S1 , S2 connected to the Internet via the high-speed broadcast. The user can then transmit a request to another network for establishing a return connection, e.g. a return connection setup request via the Internet to a certain server on the basis of a URL identifier identifying the service.

[0023] A unidirectional or bidirectional data transmission connection can be established from the terminal TE via a suitable return network. The return connection can be arranged wirelessly e.g. via a GSM (Global System for Mobile communications) network or a wireless local area network WLAN. On the other hand, the return connection can also be arranged via a wired network, such as a cable television network, public switched telephone network PSTN or an integrated services digital network ISDN. PLMN, ISDN and PSTN networks 8 and 10 are connected to the Internet via routers, gateways GW or dial-up servers 7 and 9. [0024] The terminal TE comprises necessary functions both for establishing a return connection and receiving broadcasts, preferably integrated into a single device. In Figure 1 , the terminal TE comprises e.g. a digital television and a PSTN/ISDN modem MOD connected to a return network 8. The terminal receiving broadcasts can also be e.g. a "set-top box" STB. The STB device enables digital broadcasts or Internet services to be received using the existing analogue TV and radio receivers. An extension card connected to a personal computer PC also enables digital broadcast services, such as DAB or DVB, to be received. A terminal TE2 may be otherwise similar except for the fact it comprises a radio terminal MT for establishing a return channel via the mobile communication network PLMN 10.

[0025] The source of data can be e.g. the server S1 or S2 of a content or service provider connected to the Internet. According to the invention, at least one broadcast service of the DVB network is provided with a net- work address to which the data to be transmitted via a broadcast network can be routed. The address can be the IP address of the physical network interface of a DVB server 6, a socket address referring to a certain port or application at the server 6, or a uniform resource locator (URL). The URL is a name which is provided with a protocol name (e.g. tcp:\\), a host address of a server (e.g. DVB-alma.com) and a file path name (e.g. IP services) before it. Typically, the host address of a server is a domain name system (DNS) address to enable the actual IP address at which the service is located to be obtained.

[0026] In the case of Figure 1 , an URL address such as tcp:\\DVB- alma.com/IP-services could indicate a certain subdirectory in a database 5 connected to the DVB server 6. When the server S1 transmits IP datagrams to this URL address, the server 6 stores them in the directory. The directory serves as the buffer memory of transmission equipment 4, from which the IP datagrams are added to the DVB broadcast. In the following description, however, a socket address, i.e. IPaddr_DVB, which indicates a certain application at the DVB server 6, will be used as an example.

[0027] According to a preferred embodiment of the invention, the service information on the transmission of the broadcast service providing the IP service comprises the IP address IPaddr_DVB of the service (Figure 2, step 21). The terminals TE1 and TE2 receive the address and store it in their mem- ory. Alternatively, the terminals may receive the address e.g. via the return channel as an IP multicast or when the user registers as a client for the broadcast service.

[0028] Assume that the user of the terminal TE1 desires a service from the Internet server S1. The terminal TE1 establishes a return channel via the PSTN/ISDN network 8 to the server S1 and transmits a service request (Figure 2, step 22). The service request may be e.g. an IP datagram according to Figure 3. The service request (the header of the IP datagram) comprises the IP address IPaddr_TE1 of the terminal as the source address and the IP address IPaddr_S1 of the server S1 as the destination address. The destina- tion address and the source address are in accordance with a usual service request used on the Internet, so the service request is routed to the server S1. The terminal TE1 also adds the IP address IPaddr_DVB of the DVB service to the service request. Two versions of IP packets have been defined: version 4 (IPv4) and version 6 (IPv6). An IPv6 header can be provided with extension headers, particularly a destination options header. No definite use has yet been specified for this extension header, but it is meant to transfer information to be examined by a destination node (machine). It is thus well suited to the purpose of the invention. An IPv4 header also comprises an options field of a varying length, which can be used for carrying an additional address according to the invention.

[0029] A TCP/IP header comprises a field to enable the type of service to be indicated, the type of service in this connection being used for indicating the different routing in the forward direction. A four-bit field is reserved for indicating the type of service (TOS). Only some of the TOS bit val- ues are assigned numbers. The type of service can be used for informing a router or server of how a particular IP datagram should be handled. A number could be assigned from among the TOS bits to indicate to the server that the options field of a datagram comprises the data network address of a broadcast service. An implementation is also feasible wherein the TOS has a default value 0000 and the server simply always examines whether the options field comprises this additional data network number when the type of service has the default value 0000.

[0030] An IPv6 header structure comprises fields that can be utilized in implementing the invention. An IPv6 header field called a destination options header is a field specified to carry information from a node that has transmitted a request to a server. A field does provide an obvious place for transmitting the data network address of a broadcast network service from a client terminal to a server. Only the use of filling bits has yet been specified for a field. A datagram can be routed from a server to a client via a broadcast service also without any new specifications since the IPv6 standard is pro- vided with a specified routing header. The routing header can be provided with the addresses of data network nodes through which a datagram is to pass. According to an embodiment of the invention, the server thus inserts the data network address of the broadcast service received in the destination options header into the routing header of the datagram to be transmitted in response to a service request, and routers supporting the IPv6 routing are able to route the datagram first to the address of the broadcast network, i.e. to the server 6, according to the invention. So long as the routers do not support the IPv6 protocol or when the datagrams designated to the client are tunnelled from the content server S1 to the server 6 of the broadcast network, the destination address in the datagram to be transmitted from the server to the client must be changed to the data network address of the broadcast network and the original data network address of the client is to be transmitted to the server 6 e.g. in the destination options header. The IPv6 protocol specification enables new header fields and options to be specified in a flexible manner; an extension of the extension or options header field can thus be uniquely specified for the present invention.

[0031] A service request can alternatively be a usual request e.g. to a WWW service, a WWW page then being downloaded to the server of the terminal TE1. This page can be a service order form to enable the user to specify the way in which the service is to be transmitted and the deviating routing address IPaddr_DVB. When the server S1 has thus received a new routing address, it tunnels the service datagrams as will be shown below.

[0032] The server S1 receives the service request and carries out the usual functions for producing a service to a terminal. In addition, the server S1 checks whether the service request comprises an additional address in a predetermined place (e.g. the options field), to which the service datagrams are to be routed. If there is no additional address, the server S1 transmits datagrams as usual (Figure 4A), the destination address in the datagrams being IPaddr_TE1. These datagrams are routed to the PSTN/ISDN network and further to the terminal TE1. This is also the procedure if the server S1 does not support the routing of the invention, i.e. is incapable of utilizing the additional address. If, however, the service request does comprise an additional address IPaddr_DVB, the server S1 generates the usual service datagrams having IPaddr_TE1 as the destination address (Figure 4A), but encapsulates the datagrams into the payload field of a tunnelling datagram (Figure 4B). The tun- nelling datagram has the IP address IPaddr_DVB of the DVB service as the destination address and IPaddr_S1 as the source address. These tunnelling datagrams are routed through the Internet to the DVB server 6 (Figure 2, step 23) and further, the IP services are routed to the application. The application receives the tunnelling datagrams, decapsulates the datagrams (takes off the header of the tunnelling datagram), and stores the actual service datagram (Figure 4A) in the buffer memory in the database 5 (Figure 2, step 24). The application may also carry out a subscriber identification procedure e.g. for billing for the service. Solutions related to user authentication and billing are, however, irrelevant to the invention. [0033] The server S1 may carry out tunnelling also in another way.

In this other embodiment, the server S1 does not generate the usual service datagram but a "tunnelling" service datagram of Figure 5A. The source address in this datagram is the IP address IPaddr_S1 of the server S1 and the destination address is the IP address IPaddr_DVB of the DVB server 6. The datagram further comprises the address IPaddr_TE1 of the terminal TE1 as the additional address, e.g. in the options field, in a similar manner to that in the service request of Figure 3. The payload comprises the usual payload of a service datagram. These datagrams are also routed to the application of the DVB server 6. The application changes the destination address of the service datagram to the content of the options field, i.e. to the address IPaddr_TE1 of the terminal TE1. A "modified" sen/ice datagram of Figure 5A is thus generated, which, as a matter of fact, is similar to the normal service datagram of Figure 4A. The application stores this modified service datagram in the database 5. [0034] The database 5 serves as the buffer memory in the DVB transmission equipment 4. In other words, the transmission equipment 4 retrieves data (datagrams) from the database 5 and transmits the data to the terminal in a manner known per se. It is to be noted that the transmission method used is irrelevant to the invention. In the following, however, the DVB broadcast will be described to some extent. [0035] The signal destined for the terminal TE is multiplexed together with other signals to be transmitted, and encoded and modulated according to the transmission path.

[0036] The information to be transmitted to the terminal TE in the DVB network, such as IP datagrams, is converted into a DVB data stream called elementary stream ES, which can be identified from a packet identifier PID ESENC. The DVB system allows data to be transmitted according to an MPEG-2 standard or as a data stream of its own, distinguishable by a PID identifier. The DVB system allows data to be transmitted in many different ways, as separate packets as necessary, or as periodic transmissions called data carousels, in a manner similar to a teletext. Different alternatives for arranging data transmission in a DVB system have been described in DVB standard EN 301 192 titled "DVB specification for data broadcasting", version 1.2.1. [0037] The data stream is further error encoded EENC using forward error coding FEC, multiplexed MUX and space-carrier modulated MOD using orthogonal frequency division multiplex OFDM modulation (different constellations are possible), and transmitted at a transmission frequency to a transmission path TR. In the data transmission of the DVB system, a sen/ice information SI frame of the multiplex comprises service identification information, on the basis of which a terminal MS finds a desired service from the DVB multiplex. According to the invention, this identification information may also comprise the address IPaddr_DVB. The services can be encrypted using conditional access CA encryption, and in addition, separate personal encryption is preferably also used, the key necessary for decryption preferably being stored on a smart card.

[0038] A DVB-T receiver contained in the terminal TE receives the broadcast. The received broadcast is demodulated, decoded and demultiplexed. The typically source encoded signal thus obtained can be further de- constructed into actual information e.g. by decoding the MPEG-2 coding.

[0039] When the data transmission is Internet data transmission according to the TCP/IP or user datagram protocol UDP/IP protocol, the terminal TE1 further recontructs the IP datagrams, identifies the IP datagrams designated to itself by means of the destination address IPaddr_TE1 , and, on the basis of the port number, transmits the IP datagrams to correct applications, e.g. to FTP or HTTP applications. In addition to the encryption carried out by the DVB network, the information to be transmitted can be encrypted at the application layer e.g. by utilizing a public key encryption technique. Since the broadcast network provides an excellent way to deliver data to a large number of terminals, information can also be transmitted to a group of terminals. The data obtained from the Internet can be broadcast e.g. using an IP multicast service.

[0040] It is obvious to one skilled in the art that as technology advances, the basic idea of the invention can be implemented in many different ways. The invention and its embodiments are thus not restricted to the exam- pies described above but they can vary within the scope of the claims.

1. A broadcast system comprising terminals (TE1, TE2) and broadcast services, characterized in that at least one broadcast service of the broadcast system (DVB) is provided with a dedicated public data network address, and the broadcast system is arranged to broadcast datagrams routed from a public data network to said dedicated network address to the terminals (TE1.TE2).

2. A broadcast system as claimed in claim 1, characterized in that said network address refers to a broadcast server connected to the broadcast service or to an application or directory of such a broadcast server which receives the datagrams and stores them in a buffer memory of the broadcast service to be transmitted to the terminals.

3. A broadcast system as claimed in claim 1 or 2, characterized in that said routed datagrams are tunnelling datagrams to enable rou- ing from a source connected to the public data network to a data network address of the broadcast service, using routing mechanisms of the public data network, and the broadcast system is arranged to decapsulate or modify the tunnelling datagrams into actual datagrams to be transmitted to a terminal.

4. A broadcast system as claimed in any one of claims 1 to 3, characterized in that said routed datagrams comprise the data network address of a content or service provider (S1 , S2) selected by the terminal (TE1, TE2) as a source address, said data network address of the broadcast service as a destination address, and the data network address of the terminal as additional information, and the broadcast system is arranged to change the destination address of the datagrams to said data network address of the terminal before the datagrams are broadcast.

5. A broadcast system as claimed in any one of claims 1 to 4, characterized in that said routed datagrams comprise the data network address of a content or service provider selected by the terminal as a source address, said data network address of the broadcast service as a destination address, and, encapsulated into a payload field, the actual datagrams to be transmitted to the terminal equipment (TE1 , TE2) that comprise the data network address of the terminal as a destination address, and the broadcast system (DVB) is arranged to decapsulate the routed datagrams in order to obtain the actual datagrams before the datagrams are broadcast.

Claims

6. A broadcast system as claimed in any one of claims 1 to 5, characterized in that the system (DVB) broadcasts said data network address as service information to the terminals (TE1 , TE2).

7. A broadcast system as claimed in any one of claims 1 to 6, characterized in that the terminal equipment (TE1 , TE2) is arranged to transmit said data network address to a server (S1, S2) of the content or service provider, from which the terminal is to receive a service as datagrams transmitted via said broadcast service (DVB).

8. A broadcast system as claimed in any one of the preceding claims, characterized in that the broadcast system is a digital television broadcast system or a digital radio broadcast system.

9. A broadcast system as claimed in any one of the preceding claims, characterized in that said public data network is the Internet, and said data network addresses include IP addresses, IP socket addresses and/or uniform resource locator URL addresses.

10. A method for transmitting datagrams from a server of a service provider to a terminal via a broadcast service of a broadcast system, characterized by allocating to the broadcast service a data network address in a pub- lie data network, routing datagrams associated with a selected service from said server of the service provider to said broadcast service on the basis of said data network address, transmitting said datagrams via said broadcast service to the termi- nal, said datagrams being provided with the data network address of the terminal.

11. A method as claimed in claim 10, characterized in that said routing comprises tunnelling of the datagrams associated with the service from said server to the network address of the broadcast service. 12. A method as claimed in claim 10 or 11, characterized by transmitting, from the server of the content provider or the service provider to the broadcast sen/ice, datagrams comprising the data network address of the server as a source address, the data network address of the broadcast service as a destination address, and the data network address of the terminal as additional information, changing, in the broadcast service, the destination address in the datagrams to the data network address of the terminal, broadcasting the modified datagrams to the terminal via the broadcast service. 13. A method as claimed in claim 10 or 11, characterized by transmitting, from the server of the content provider or the sen/ice provider to the broadcast service, datagrams comprising the data network address of the server as a source address, the data network address of the broadcast service as a destination address, and, encapsulated into a payload field, the actual datagram designated to the terminal, decapsulating the datagrams in the broadcast service, broadcasting said actual datagrams to the terminals.

14. A method as claimed in any one of claims 10 to 13, charac- terized by broadcasting said data network address to the terminals of the broadcast system as service information.

15. A method as claimed in any one of claims 10 to 14, character i z e d by broadcasting said data network address to the terminals of the broadcast system as an IP multicast. 16. A method as claimed in any one of claims 10 to ^.characterized by transmitting said data network address from the terminal to the server of the content or service provider in a service request transmitted to the server via another network than said broadcast network.

17. A method as claimed in any one of claims 10 to 16, charac- terized in that the broadcast system is a digital television broadcast system or a digital radio broadcast system.

18. A method as claimed in any one of claims 10 to ^.characterized in that said public data network is the Internet, and said data network addresses include IP addresses, IP socket addresses and/or uniform resource locator URL addresses.

19. A terminal which operates as a receiver in a broadcast network (DVB) and which is capable of establishing a connection to a public data network via a telecommunication network (8, 10), c h aracte rize d in that the terminal (TE1, TE2) is arranged to receive a data network address of a broadcast service of said public data network as service information from the broadcast network, and the terminal (TE1, TE2) is_. arranged to transmit said data network address to a content or service provider (S1 , S2) as an address to which datagrams associated with a requested service are to be routed.

20. A terminal which operates as a receiver in a broadcast network and which is capable of establishing a connection to a public data network via a telecommunication network (8, 10), c h a r a c t e r i z e d in that the terminal is arranged to receive a data network address of a broadcast service of said public data network as an IP multicast from the broadcast network, and the terminal is arranged to transmit said data network address to a content or service provider (S1 , S2) as an address to which datagrams associated with a requested service are to be routed.

21. A terminal as claimed in claim 20, c h a r a c t e r i z e d in that the network is a digital television broadcast network or a digital radio broadcast network.

22. A terminal as claimed in claim 20 or 21 , c h a r a c t e r i z e d in that said public data network is the Internet, and said data network addresses include IP addresses, IP socket addresses and/or uniform resource locator URL addresses.

23. A server connected to a public data network to provide content or other services to be transmitted to a client in the form of datagrams, c h a r a c t e r i z e d in that the server (6) is, in response to a service request comprising, in addition to a data network address of the client, a second data network address to which service datagrams are to be routed, arranged to tunnel the service datagrams destined for the client to said second data network address. 24. A server as claimed in claim 23, c h a r a c t e r i z e d in that the server is arranged to transmit datagrams comprising the data network address of the server as a source address and the second data network address as a destination address.

25. A server as claimed in claim 23 or 24, c h a r a c t e r i z e d in that the datagrams comprise the data network address of the client as additional information.

26. A server as claimed in claim 23 or 24, c h a r a c t e r i z e d in that the actual service datagrams comprising the data network address of the terminal (TE1 , TE2) are encapsulated into a payload field of the datagrams. 27. A server as claimed in any one of claims 23 to 26, c h a r a c - t e r i z e d in that said public data network is the Internet, and said data net- work addresses include IP addresses, IP socket addresses and/or uniform resource locator URL addresses.

28. A server as claimed in any one of claims 23 to 27, c h a r a c - t e r i z e d in that said second data network address is the data network address of a broadcast service of a broadcast system.