Diameter Mobile IPv4 Application (application id: 2)

The Diameter Mobile IPv4 Application, defined by RFC 4004, is an essential protocol for supporting Mobile IPv4 services within the context of Authentication, Authorization, and Accounting (AAA) operations. This application facilitates seamless mobility management for Mobile Nodes (MNs) as they move across different administrative domains while maintaining a constant IP address.
The primary purpose of the Diameter Mobile IPv4 Application is to provide a standardized mechanism for AAA functions within the Mobile IPv4 framework. This includes verifying the identity of a Mobile Node (MN), authorizing its access to network resources, and accounting for its usage while connected to the network. The application ensures that these functions are securely and efficiently performed as the MN moves between home and foreign networks.

The architecture involves key entities:

• Mobile Node (MN): A device that moves between networks, maintaining connectivity through a fixed home IP address.
• Home Agent (HA): A network node in the home domain responsible for managing the MN's IP address and forwarding packets to its current location.
• Foreign Agent (FA): A network node in the visited domain that facilitates the MN's attachment to the network and interacts with the HA to tunnel packets to the MN.
• AAA Home (AAAH) and AAA Foreign (AAAF) Servers: These servers are responsible for authenticating and authorizing the MN in the home and visited domains, respectively.

Diameter Mobile IPv4 Application interface workflow:

1. Registration Request and Creation of AMR Message:
   • When an MN moves into a foreign domain, it initiates a Registration Request to the FA. The FA creates an AA-Mobile-Node-Request (AMR) message, encapsulating important details such as the MN’s Home Address, Home Agent, and other relevant attributes.
2. AMR Message Handling:
   • The FA forwards the AMR message to the AAAF in the visited realm. The AAAF determines whether to process the request locally or forward it to the home realm's AAAH for further processing. If forwarded, the AAAH authenticates the MN and verifies its authorization to use network resources.
3. Authorization and Response:
   • The AAAH processes the request and sends back an AA-Mobile-Node-Answer (AMA) message. This message grants or denies the requested service, including the expiration time of the authorization.
4. Session Establishment and Management:
   • Upon successful authorization, the HA is involved to establish the necessary tunneling and routing mechanisms to forward packets to the MN in the foreign network. Session identifiers are generated and managed to track the ongoing session of the MN as it moves across networks. These identifiers ensure that the session remains intact even if the MN connects to multiple FAs during its mobility.
5. Session State and Management:
   • The session state may be maintained by either the AAAH or the AAAF, depending on the session's specific requirements. Some session information is kept at the FA and HA levels to facilitate continued service delivery as the MN roams.

For complete technical specification of Diameter Mobile IPv4 Application interface in Diameter protocol please refer to: [RFC4004]