Maintaining a common identifier for a user session on a communication network

1. A method for maintaining a common billing identifier for a user session in a communication network, the method comprising:

transferring an authentication request associated with a user session from an access node of the communication network to an authentication, authorization, and accounting (AAA) server;

at the access node, receiving an authentication acknowledgment transferred from the AAA server in response to the authentication request;

at the access node, generating a billing identifier associated with the user session in response to the authentication acknowledgment;

transferring the billing identifier from the access node to an application node;

generating a registration request at the access node, wherein the registration request comprises the billing identifier;

transferring the registration request from the access node to the application node;

transferring a registration acknowledgment from the application node to the access node in response to the registration request;

transferring a first accounting start message from the access node to the AAA server in response to the registration acknowledgment; and

transferring a second accounting start message from the application node to the AAA server in response to the registration acknowledgment;

wherein at least one of the first accounting start message and the second accounting start message comprises the billing identifier.

2. The method of claim 1 , wherein the access node comprises one of a packet data serving node and an access service network.

3. The method of claim 1 , wherein the application node comprises a home agent of a mobile Internet Protocol network.

4. The method of claim 1 , further comprising:

at the access node, receiving a registration request from a user device; and

in response to the authentication acknowledgment, transferring a registration acknowledgment from the access node to the user device;

wherein transferring the authentication request from the access node to the AAA server occurs in response to receiving the registration request from the user device.

5. The method of claim 1 , further comprising:

generating first usage data records associated with the user session in the access node;

transferring the first usage data records from the access node to a billing system;

generating second usage data records associated with the user session in the application node; and

transferring the second usage data records from the application node to the billing system;

wherein the first usage data records and the second usage data records comprise the billing identifier.