# What is Authentication, Authorization, and Accounting (AAA)?

> Authentication, authorization, and accounting (AAA) is an architectural model for coordinating three access functions: verifying a requesting identity, determining which services or actions it may use, and recording relevant activity or resource consumption.

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## Content

AAA is widely used for network and remote-access services, although the model also applies wherever these functions are handled by shared policy services.

In a typical deployment, an access device sends a request to an AAA server using a protocol such as Remote Authentication Dial-In User Service (RADIUS) or Diameter. The response can carry an accept or reject result and authorization attributes. Accounting messages may record session starts and stops, duration, traffic, assigned addresses, or other service-specific facts.

### Key points

- **Authentication:** Establishes confidence in the user, device, or other subject making the request.
- **Authorization:** Determines permitted services, configuration, scope, or constraints after evaluating policy and request context.
- **Accounting:** Produces records for operations, capacity analysis, chargeback or billing, investigations, and policy review; the exact fields and reliability depend on the protocol and deployment.
- **Important limitation:** AAA records are not automatically a complete or tamper-proof audit trail. Missing events, shared identities, clock errors, transport weaknesses, or inconsistent enforcement can undermine attribution and review.

### Related terms

[Authentication](<https://yellowcube.eu/glossary/authentication/>) · [Authorization](<https://yellowcube.eu/glossary/authorization/>) · [Remote Authentication Dial-In User Service (RADIUS)](<https://yellowcube.eu/glossary/remote-authentication-dial-in-user-service/>) · [IEEE 802.1X authentication](<https://yellowcube.eu/glossary/ieee-802-1x-authentication/>) · [Network access control (NAC)](<https://yellowcube.eu/glossary/network-access-control/>)

### Sources

[IETF RFC 3539: Authentication, Authorization, and Accounting Transport Profile](https://www.rfc-editor.org/info/rfc3539) · [IETF RFC 6733: Diameter Base Protocol](https://www.rfc-editor.org/info/rfc6733)

## Attribution and scope

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