JUNOSe 9.1.x Broadband Access Configuration Guide > Configuring RADIUS Dynamic-Request Server > RADIUS-Initiated Change of Authorization

RADIUS-Initiated Change of Authorization

This section describes the RADIUS dynamic-request server's support for CoA messages. CoA messages are used by the E-series router's RADIUS-initiated packet mirroring feature, which is described in JUNOSe Policy Management Configuration Guide, Chapter 12, Configuring RADIUS-Based Mirroring, and by Service Manager, which is described in Chapter 27, Configuring Service Manager of this guide.

Change-of-Authorization Messages

The RADIUS dynamic-request server receives and processes the unsolicited CoA messages from RADIUS servers. The RADIUS-initiated CoA feature uses the following codes in its RADIUS request and response messages:

• CoA-Request (43)
• CoA-ACK (44)
• CoA-NAK (45)

Message Exchange

The RADIUS server and the router's RADIUS dynamic-request server exchange messages using UDP. The CoA-Request message sent by the RADIUS server has the same format as the Disconnect-Request packet that is sent for a disconnect operation.

The response is either a CoA-ACK or a CoA-NAK message:

• If AAA successfully changes the authorization, the response is a RADIUS-formatted packet with a CoA-ACK message, and the data filter is applied to the session.
• If AAA is unsuccessful, the request is malformed, or attributes are missing, the response is a RADIUS-formatted packet with a CoA-NAK message.

Supported Error-Cause Codes (RADIUS Attribute 101)

When AAA is unsuccessful, the RADIUS dynamic-request server includes an error-cause attribute (RADIUS attribute 101) in the CoA-NAK message that it sends back to the RADIUS server. If the detected error does not map to one of the supported error-cause attributes, the router sends the CoA-NAK without an error-cause attribute. Table 43 lists the supported error-cause codes.

 Table 43:  Error-Cause Codes (RADIUS Attribute 101) 

 Code
 Value
 Description

 401

 Unsupported attribute

 The request contains an attribute that is not supported (for example, a third-party attribute). 


 402

 Missing attribute

 A critical attribute (for example, the session identification attribute) is missing from a request. 


 404

 Invalid request

 Some other aspect of the request is invalid, such as if one or more attributes (for example, the packet mirroring Mirror Identifier value) are not formatted properly. 


 503

 Session context not found

 The session context identified in the request does not exist on the NAS. 


 504

 Session context not removable

 The subscriber identified by attributes in the disconnect request is owned by a component that does not support RADIUS-initiated disconnect (for example, IP LAC subscribers cannot be disconnected). 


 506

 Resources unavailable

 A request could not be honored due to lack of available NAS resources (such as memory).



 

Qualifications for Change of Authorization

To complete the change of authorization for a user, the CoA-Request must contain one of the following RADIUS attributes. AAA services handle the actual request.

• User-Name [attribute 1] (per virtual router context)
• Framed-IP-Address [attribute 8] (per virtual router context)
• Calling-Station-ID [attribute 31]
• Acct-Session-ID [attribute 44]

Security/Authentication

For change-of-authorization operations, the RADIUS server calculates the authenticator as specified for an Accounting-Request message in RFC 2866. The RADIUS dynamic-request server verifies the request using authenticator calculation as specified for an Accounting-Request in RFC 2866. A key (secret), as specified in RFC 2865, must be configured and used in the calculation of the authenticator. The response authenticator is calculated as specified for an Accounting-Response message in RFC 2866.