System and method for allocating session initiation protocol (SIP) identifications (IDs) to user agents

1. A method of enabling communication on an Internet Protocol based network which comprises:

establishing a communications connection between a communications device and a server via a network;

querying a database associated with the server, the database containing data relating to free Session Initiation Protocol ID's that are available to be allocated to the communications device and data relating to allocated Session Initiation Protocol ID's, for determining a free Session Initiation Protocol ID that can be allocated to the communications device;

allocating the determined free Session Initiation Protocol ID for use by the communications device;

moving the determined free Session Initiation Protocol ID to the data relating to allocated Session Initiation Protocol ID's; and

after the communications device to which the Session Initiation Protocol ID was originally allocated has completed a communications session using SIP, returning the Session Initiation Protocol ID to the data relating to free Session Initiation Protocol ID's for use by another communications device.

2. The method according to claim 1 , wherein the communications device comprises a portable communications device.

3. The method according to claim 1 , which further comprises allocating a unique identifier for the communications device.

4. The method according to claim 3 , which further comprises allocating from the server to the communications device a Session Initiation Protocol ID associated with an IP address, PIN number, or email address.

5. The method according to claim 1 , wherein the communications device comprises one of a hardware or a software agent as a user agent.

6. The method according to claim 1 , wherein the server is operative as a Session Initiation Protocol registrar server.

7. A communications system comprising:

a server that is operable for communicating with a communications device;

a database associated with the server, the database comprising data relating to free Session Initiation Protocol ID's that are available to be allocated to the communications device and data relating to allocated Session Initiation Protocol ID's;

wherein the server is operative for querying the database and determining a free Session Initiation Protocol ID that can be allocated to the communications device;

allocating the determined free Session Initiation Protocol ID for use by the communications device;

moving the determined free Session Initiation Protocol ID to the data relating to allocated Session Initiation Protocol ID's; and

after the communications device to which the Session Initiation Protocol ID was originally allocated has completed a communications session using Session Initiation Protocol, returning the Session Initiation Protocol ID to the data relating to free Session Initiation Protocol ID's for use by another communications device.

8. The communications system according to claim 7 , wherein the communications device comprises a portable communications device.

9. The communications system according to claim 7 , which further comprises allocating a unique identifier for the communications device.

10. The communications system according to claim 9 , which further comprises the server being operative to allocate from the server to the communications device a Session Initiation Protocol ID associated with an IP address, PIN number or email address.

11. The communications system according to claim 7 , wherein the communications device comprises one of a hardware or a software agent as a user agent.

12. The communications system according to claim 7 , wherein the server is operative as a Session Initiation Protocol registrar server.