Telecommunication

What is UAR User authorization request

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UAR: User Authorization Request Explained

In the realm of mobile network communication, particularly within the Diameter protocol, UAR stands for User Authorization Request. It's a crucial message exchanged between network entities to determine if a specific user is authorized to access network services.

Understanding UAR Messages:

  • Function: A UAR message is sent by a network element, typically a Serving Gateway (SGSN) in 2G/3G or a Packet Gateway (PGW) in 4G/5G, to a Diameter server (often the Home Subscriber Server - HSS) requesting authorization for a user.
  • Information Contained: The UAR message carries essential information about the user and the access request:
    • User Identity: This includes identifiers like the International Mobile Subscriber Identity (IMSI) or the Public User Identity (PUI), depending on the network configuration.
    • Visited Network Information: This specifies the network where the user is currently attempting to access services (e.g., Mobile Network Code - MNC).
    • User Authorization Type: This indicates the type of authorization requested, such as registration (attaching to the network) or de-registration (detaching from the network).
    • Additional Information (Optional): Depending on network configuration, the UAR might include details about the user's device type, requested services, or QoS (Quality of Service) requirements.

UAR Message Flow:

  1. Initiation: Upon receiving a service request from a User Equipment (UE), the Serving Gateway (SGSN/PGW) initiates the authorization process.
  2. UAR Transmission: The SGSN/PGW crafts a UAR message containing the user identity and relevant information.
  3. Routing: The UAR message is routed to the Diameter server, typically the Home Subscriber Server (HSS) associated with the user's home network.
  4. Authorization Check: The HSS verifies the user's identity, checks for any restrictions or active subscriptions, and performs authorization checks based on network policies.
  5. UAA (User Authorization Answer) Response: The HSS sends a UAA (User Authorization Answer) message back to the Serving Gateway (SGSN/PGW) with the authorization decision:
    • Success: The user is authorized to access services, and the Serving Gateway can proceed with service provisioning.
    • Failure: The user is not authorized, and the Serving Gateway might deny access or request additional information.
  6. Service Provisioning: Based on the UAA response, the Serving Gateway (SGSN/PGW) initiates service provisioning or informs the UE about the access denial.

Benefits of UAR Messages:

  • Centralized Control: UAR messages enable centralized user authorization by offloading this task from individual network elements to the HSS, which has access to user profiles and authorization policies.
  • Security: User authorization checks can be performed based on user credentials and network policies, enhancing overall network security.
  • Policy Enforcement: Network policies regarding user access, service limitations, or QoS parameters can be enforced through UAR messages and the HSS decisions.

Additional Considerations:

  • Diameter Protocol: UAR messages are part of the Diameter protocol, a widely used application layer protocol for authentication, authorization, and accounting (AAA) in IP networks.
  • Alternative Approaches: In some mobile network architectures, other mechanisms like EAP (Extensible Authentication Protocol) might be used for user authentication, potentially in conjunction with UAR for authorization.
  • Evolving Use Cases: With the emergence of 5G and network slicing, UAR messages might evolve to support new functionalities like authorization for specific network slices or differentiated service levels for different applications.

Conclusion:

UAR messages play a vital role in mobile network communication by facilitating user authorization and access control. They enable centralized authorization policies, enhance network security, and contribute to efficient service provisioning for UEs. As mobile network technologies continue to advance, the role of UAR messages might expand further to accommodate the evolving needs of future network architectures.

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