Telecommunications network having number portability

1. A method of monitoring number portability in a communication system, the method comprising:

receiving ported-out information at an originating network, wherein the received ported-out information identifies a ported-out subscriber of the originating network and a recipient network;

providing the ported-out information to a charging system configured to determine a charge for a call involving the ported-out subscriber in the recipient network; and

transmitting a message to the recipient network, wherein the message indicates that the ported-out subscriber is ported-in to the recipient network.

2. The method of claim 1 , further comprising querying a mobile number portability database to determine that the ported-out subscriber is ported-out from the originating network.

3. The method of claim 2 , wherein the ported-out information is received at a serving call state control function of the originating network from the mobile number portability database.

4. The method of claim 2 , wherein the mobile number portability database is queried in response to a request at the originating network for the call to be connected to the ported-out subscriber.

5. The method of claim 2 , wherein the ported-out information further comprises an indication that a called subscriber is the ported-out subscriber.

6. The method of claim 1 , wherein the message includes at least a portion of the ported-out information.

7. The method of claim 1 , wherein the message comprises a session initiation protocol (SIP) INVITE message.

8. The method of claim 7 , wherein the SIP INVITE message includes the ported-out information in at least one of a P-header or a charging information header.

9. The method of claim 1 , wherein the ported-out information is provided to the charging system as part of a session initiation protocol message or a diameter protocol message.

10. The method of claim 1 , wherein the message is provided by a serving call state control function of the originating network to an interrogating call state control function of the recipient network.

11. The method of claim 1 , further comprising inserting the ported-out information into a credit control request, wherein providing the ported-out information to the charging system comprises providing the credit control request to the charging system.

12. The method of claim 11 , further comprising receiving a credit control assured message from the charging system in response to the credit control request.

13. The method of claim 12 , wherein the credit control assured message is received prior to transmitting the message to the recipient network such that the charging system is a pre-paid charging system.

14. The method of claim 1 , further comprising:

receiving a session established message from the recipient network;

inserting the ported-out information into an accounting control request; and

transmitting the accounting control request to the charging system.

15. The method of claim 14 , wherein the ported-out information is transmitted as one or more attribute value pairs within the accounting control request.

16. The method of claim 14 , further comprising receiving an accounting control answer from the charging system, and wherein the charge comprises a post-paid billing charge.

17. A network element for monitoring number portability in a communication system, the network element comprising:

means for receiving ported-out information at an originating network, wherein the ported-out information identifies a ported-out subscriber and a recipient network;

means for monitoring a call involving the ported-out subscriber in the recipient network; and

means for determining a charge for the call based on the monitoring of the call.

18. The network element of claim 17 , wherein the charge is based on a service provided by at least one of the recipient network or the originating network of the ported-out subscriber.

19. The network element of claim 17 , wherein the ported-out information is received in response to a session established message received at the originating network of the ported-out subscriber.

20. The network element of claim 17 , wherein the received ported-out information is incorporated in an accounting control request message.

21. The network element of claim 20 , further comprising means for providing an accounting control answer in response to the accounting control request message.

22. A system for providing number portability, the system comprising:

a first network element configured to establish a call involving a ported-out subscriber, wherein the ported-out subscriber is located in a recipient network;

a second network element configured to

receive ported-out information at an originating network of the ported-out subscriber, wherein the ported-out information identifies the ported-out subscriber and the recipient network;

monitor the call; and

determine a charge for the call based on the monitoring of the call.

23. The system of claim 22 , wherein the second network element receives the ported-out information from the first network element.

24. The system of claim 22 , wherein the first network element is further configured to provide the ported-out information to the recipient network.

25. The system of claim 22 , wherein the first network element and the second network element are part of the originating network.