CLAIMS :

1.

A communication system comprising: an IP network offering services to users ; and an IPT provider network providing call related functions to users and comprising serving entities which are arranged to receive a control protocol message, analyze the control protocol message, and, depending on the analyzing result, perform call related functions, wherein the IP network is arranged to receive a control protocol message, analyze the control protocol message and, depending on the analyzing result, execute services.

2.	A system according to claim 1, wherein the IPT provider network comprises a subscriber database containing subscriber subscription information.

3.

A system according to claim 1, wherein, when a respective serving entity receives, from a user equipment, a control protocol message for registering the user equipment, it analyzes a user address in the control protocol message, and registers the user equipment to the IPT provider network in accordance with the user address.

4.

A system according to claim 3, wherein, when the IP network receives, from the user equipment, another control protocol message for registering the user equipment, it analyzes an IP network user identification address in the control protocol message, and registers the user equipment to the IP network in accordance with the IP network user identification address.

5.

A system according to claim 2, wherein, when a respective serving entity receives, from a user equipment, a control protocol message for registering the user equipment, it analyzes a user address in the control protocol message, registers the user equipment to the IPT provider network in accordance with the user address, fetches an IP network user identification address related to the user address from the subscriber database and generates a control protocol message with the IP network user identification address and sends it to the IP network for registering the user equipment to the IP network.

6.

A system according to claim 1, wherein, when a respective serving entity receives, from a user equipment, a control protocol message for initiating a call, it analyzes the control protocol message and, if an IP network user identification address of a called party and an originating call indication are present in the control protocol message, forwards the control protocol message to the IP network.

7.

A system according to claim 2, wherein, when a respective serving entity receives, from a user equipment, a control protocol message for initiating a call, it analyzes the control protocol message and, if a called party address is present in the control protocol message, it fetches an IP network user identification address related to the called party address from the subscriber database and sends a control protocol message with the IP network user identification address and an originating call indication towards the IP network.

8.

A system according to claim 1, wherein, when a respective serving entity receives a control protocol message indicating an initiated call to a user equipment, it analyzes the control protocol message, and, if a user identification address and a terminating call indication are present in the control protocol message, forwards the control protocol message to the IP network.

9.

A system according to claim 2, wherein, when a respective serving entity receives a control protocol message indicating an initiated call to a user equipment, it analyzes the control protocol message and, if a user address is present in the control protocol message, fetches an IP network user identification address related to the user address from the subscriber database and sends a control protocol message with the IP network user identification address and a terminating call indication towards the IP network.

10.	A system according to claim 8, wherein the IP network, upon receiving the control protocol message sent from the respective serving entity, executes terminating services.

11.	A system according to claim 9, wherein the IP network, upon receiving the control protocol message sent from the respective serving entity, executes terminating services.

12.

A system according to claim 10, wherein the respective serving entity indicates an address of another serving entity in the IPT provider network in the control protocol message indicating the initiated call and sent to the IP network, and the IP network uses the other serving entity when routing the call towards the user equipment.

13.

A system according to claim 11, wherein the respective serving entity indicates an address of another serving entity in the IPT provider network in the control protocol message indicating the initiated call and sent to the IP network, and the IP network uses the other serving entity when routing the call towards the user equipment.

14.	A system according to claim 12, wherein the respective serving entity indicates the address of the other serving entity by adding a parameter containing the address to a descriptor contained in the control protocol message indicating the initiated call which is sent towards the IP network.

15.	A system according to claim 13, wherein the respective serving entity indicates the address of the other serving entity by adding a parameter containing the address to a descriptor contained in the control protocol message indicating the initiated call which is sent towards the IP network.

16.	A system according to claim 12, wherein the respective serving entity indicates the address of the other serving entity by adding a control protocol header containing the address to the control protocol message indicating the initiated call which is sent towards the IP network.

17.	A system according to claim 13, wherein the respective serving entity indicates the address of the other serving entity by adding a control protocol header containing the address to the control protocol message indicating the initiated call which is sent towards the IP network.

18.	A system according to claim 7, wherein the respective serving entity adds a new control protocol header comprising the originating call indication to the control protocol message.

19.	A system according to claim 9, wherein the respective serving entity adds a new control protocol header comprising the terminating call indication to the control protocol message sent to the IP network.

20.	A system according to claim 1, wherein the control protocol comprises SIP.

21.

A method of communicating in a communication system which comprises an IP network offering services to users and an IPT provider network providing call related functions to users, said method comprising the steps of: receiving a control protocol message by a respective serving entity in the IPT provider network; analyzing the received control protocol message by the respective serving entity; depending on the analyzing result, performing call related functions by the respective serving entity; analyzing a received control protocol message by the IP network ; and depending on the analyzing result, executing services by the IP network.

22.

A method according to claim 21, wherein, when in said receiving step a control protocol message for registering a user equipment is received, a user address in the control protocol message is analyzed, and the user equipment is registered to the IPT provider network in accordance with the user address.

23.

A method according to claim 22, comprising the further step of: receiving, from the user equipment, another control protocol message for registering the user equipment, by the IP network, whereupon an IP network user identification address in the control protocol message is analyzed by the IP network, and the user equipment is registered to the IP network in accordance with the IP network user identification address.

24.

A method according to claim 21, wherein, when a control protocol message for registering a user equipment is received in said receiving step, a user address in the control protocol message is analyzed, the user equipment is registered to the IPT provider network in accordance with the user address, an IP network user identification address related to the user address is fetched from a subscriber database in the IPT provider network and a control protocol message with the IP network user identification address is generated and sent towards the IP network for registering the user equipment to the IP network.

25.

A method according to claim 21, wherein, when a control protocol message for initiating a call is received in said receiving step, the control protocol message is analyzed and, if an IP network user identification address of a called party and an originating call indication are present in the control protocol message, the control protocol message is forwarded to the IP network.

26.

A method according to claim 21, wherein, when a control protocol message for initiating a call is received in said receiving step, the control protocol message is analyzed and, if a called party address is present in the control protocol message, an IP network user identification address related to the called party address is fetched from a subscriber database in the IPT provider network and a control protocol message with the IP network user identification address and an originating call indication is sent towards the IP network.

27.

A method according to claim 21, wherein, when a control protocol message indicating an initiated call to a user equipment is received in said receiving step, the control protocol message is analyzed, and, if a user identification address and a terminating call indication are present in the control protocol message, the control protocol message is forwarded to the IP network.

28.

A method according to claim 21, wherein, when a control protocol message indicating an initiated call to a user equipment is received in said receiving step, the control protocol message is analyzed and, if a user address is present in the control protocol message, an IP network user identification address related to the user address is fetched from a subscriber database in the IPT provider network and a control protocol message with the IP network user identification address and a terminating call indication is sent towards the IP network.

29.	A method according to claim 27, wherein the control protocol message sent from a respective serving entity is received by the IP network and terminating services are executed by the IP network.

30.	A method according to claim 28, wherein the control protocol message sent from a respective serving entity is received by the IP network and terminating services are executed by the IP network.

31.

A method according to claim 29, wherein an address of another serving entity in the IPT provider network is indicated in the control protocol message indicating the initiated call which is sent towards the IP network, and the other serving entity is used by the IP network when routing the call towards the user equipment.

32.

A method according to claim 30, wherein an address of another serving entity in the IPT provider network is indicated in the control protocol message indicating the initiated call which is sent towards the IP network, and the other serving entity is used by the IP network when routing the call towards the user equipment.

33.	A method according to claim 31, wherein the address of the other serving entity is indicated by adding a parameter containing the address to a descriptor contained in the control protocol message indicating the initiated call which is sent towards the IP network.

34.	A method according to claim 32, wherein the address of the other serving entity is indicated by adding a parameter containing the address to a descriptor contained in the control protocol message indicating the initiated call which is sent towards the IP network.

35.	A method according to claim 31, wherein the address of the other serving entity is indicated by adding a control protocol header containing the address to the control protocol message indicating the initiated call which is sent towards the IP network.

36.	A method according to claim 32, wherein the address of the other serving entity is indicated by adding a control protocol header containing the address to the control protocol message indicating the initiated call which is sent towards'the IP network.

37.	A method according to claim 26, wherein a new control protocol header comprising the originating call indication is added to the control protocol message.

38.	A method according to claim 28, wherein a new control protocol header comprising the terminating call indication is added to the control protocol message sent towards the IP network.

39.	A method according to claim 21, wherein the control protocol comprises SIP.

40.	A user equipment for communicating in a communication system according to any one of claims 1 to 20, wherein the user equipment is arranged to use control protocol methods for attaching to said system.

41.	A user equipment according to claim 40, wherein the user equipment is arranged to use a control protocol message for registering to said system.

42.	A user equipment according to claim 41, wherein the user equipment sends a control protocol message with a user address towards the IPT provider network for registering to the system.

43.

A user equipment according to claim 41, wherein the user equipment sends a control protocol message with a user address towards the IPT provider network and another control protocol message with an IP network user identification address related to the user address to the IP network for registering to the system.

44.	A user equipment according to claim 40, wherein the user equipment is arranged to send a control protocol message towards the system for initiating a call.

45.	A user equipment according to claim 44, wherein the user equipment sends a control protocol message for initiating a call comprising an IP user identification address of a called party and an originating call indication towards the IPT provider network.

46.	A user equipment according to claim 44, wherein the user equipment sends a control protocol message for initiating a call comprising an address of a called party towards the IPT provider network.

47.	A user equipment according to claim 40, wherein the user equipment is arranged to receive a control protocol message initiated from another party to invite the user equipment to a call from the system.

48.	A user equipment according to claim 40, wherein the control protocol comprises SIP.

49.

A serving entity in an IPT provider network providing call related functions to users and communicating with an IP network offering services to users, wherein said serving entity is arranged to receive a control protocol message, analyze the control protocol message, and, depending on the analyzing result, perform call related functions.

50.

A serving entity according to claim 49, wherein, when said serving entity receives, from a user equipment, a control protocol message for registering the user equipment, it analyzes a user address in the control protocol message, and registers the user equipment to the IPT provider network in accordance with the user address.

51.

A serving entity according to claim 49, wherein, when said serving entity receives, from a user equipment, a control protocol message for registering the user equipment, it analyzes a user address in the control protocol message, registers the user equipment to the IPT provider network in accordance with the user address, fetches an IP network user identification address related to the user address from a subscriber database in the IPT provider network and generates a control protocol message with the IP network user identification address and sends it towards the IP network for registering the user equipment to the IP network.

52.

A serving entity according to claim 49, wherein, when said serving entity receives, from a user equipment, a control protocol message for initiating a call, it analyzes the control protocol message and, if an IP network user identification address of a called party and an originating call indication are present in the control protocol message, forwards the control protocol message to the IP network.

53.

A serving entity according to claim 49, wherein, when said serving entity receives, from a user equipment, a control protocol message for initiating a call, it analyzes the control protocol message and, if a called party address is present in the control protocol message, it fetches an IP network user identification address related to the called party address from a subscriber database in the IPT provider network and sends a control protocol message with the IP network user identification address and an originating call indication towards the IP network.

54.

A serving entity according to claim 49, wherein, when said serving entity receives a control protocol message indicating an initiated call to a user equipment, it analyzes the control protocol message, and, if a user identification address and a terminating call indication are present in the control protocol message, forwards the control protocol message to the IP network.

55.

A serving entity according to claim 49, wherein, when said serving entity receives a control protocol message indicating an initiated call to a user equipment, it analyzes the control protocol message and, if a user address is present in the control protocol message, fetches an IP network user identification address related to the user address from the subscriber database and sends a control protocol message with the IP network user identification address and a terminating call indication towards the IP network.

56.	A serving entity according to claim 54, wherein said serving entity indicates an address of another serving entity in the IPT provider network in the control protocol message indicating the initiated call and sent towards the IP network.

57.	A serving entity according to claim 55, wherein said serving entity indicates an address of another serving entity in the IPT provider network in the control protocol message indicating the initiated call and sent towards the IP network.

58.	A serving entity according to claim 56, wherein said serving entity indicates the address of the other serving entity by adding a parameter containing the address to a descriptor contained in the control protocol message indicating the initiated call which is sent towards the IP network.

59.	A serving entity according to claim 57, wherein said serving entity indicates the address of the other serving entity by adding a parameter containing the address to a descriptor contained in the control protocol message indicating the initiated call which is sent towards the IP network.

60.	A serving entity according to claim 56, wherein said serving entity indicates the address of the other serving entity by adding a control protocol header containing the address to the control protocol message indicating the initiated call which is sent towards the IP network.

61.	A serving entity according to claim 57, wherein said serving entity indicates the address of the other serving entity by adding a control protocol header containing the address to the control protocol message indicating the initiated call which is sent towards the IP network.

62.	A serving entity according to claim 53, wherein said serving entity adds a new control protocol header comprising the originating call indication to the control protocol message.

63.	A serving entity according to claim 55, wherein said serving entity adds a new control protocol header comprising the terminating call indication to the control protocol message sent towards the IP network.

64.	A serving entity according to claim 49, wherein the control protocol comprises SIP.

65.

An IP network offering services to users and communicating with an IPT provider network providing call related functions to users, wherein said IP network is arranged to receive a control protocol message, analyze the control protocol message and, depending on the analyzing result, execute services.

66.	An IP network according to claim 65, wherein said IP network is arranged to receive control protocol messages from a serving entity in the IPT provider network.

67.	An IP network according to claim 65, wherein said IP network is arranged to receive control protocol messages from a user equipment.

68.

An IP network according to claim 67, wherein, when said IP network receives, from the user equipment, a control protocol message for registering the user equipment, it analyzes an IP network user identification address in the control protocol message, and registers the user equipment to the IP network in accordance with the IP network user identification address.

69.	An IP network according to claim 66, wherein, when said IP network receives, from a serving entity, a control protocol message indicating an initiated call towards a user equipment, it executes terminating services.

70.	An IP network according to claim 69, wherein, if an address of another serving entity in the IPT provider network is indicated in the control protocol message, said IP network uses the other serving entity when routing the call towards the user equipment.

71.	An IP network according to claim 65, wherein the control protocol comprises SIP.