AVP decoding failure in Gx

Reporting an AVP decoding problem in Gx is described in the following example:

A Gx directive is received to install two overrides on the node. The two overrides are supposed to change the sla-profiles and sub-profiles for the subscriber host. The AVP that is used to change the sla-profile is miss-formatted. The predefined sla-profile keyword in the Charging-Rule-Install AVP is misspelled as spa-profile instead of sla-profile.

Charging-Rule-Install ::= <AVP Header: 1001>
    Charging-Rule-Name <AVP Header: 1005> = ‟Sub-Profile:prem”
    Charging-Rule-Name <AVP Header: 1005> = ‟Spa-Profile:voip+data”

Because the Charging-Rule-Name AVP has the M-bit set, the whole message fails and an error is reported. No rules within this Gx message is installed (not even the valid ones, then this would be the Charging-Rule-Name = ‟Sub-Profile:prem”).

Note: If the M-bit was clear in the Charging-Rule-Name AVP, the erroneous AVP would be simply ignored and proceed with installation of the remaining, correctly formatted rules.

The nature of the error depends on the original directive sent by the PCRF (RAR or CCA – push or pull model).

If the directive from the PCRF is passed with the cca command, the response is CCR-U with the following error related AVPs:

[ Error-Message ] — ‟Invalid value spa-profile:voip+data”

Charging-Rule-Report ::= < AVP Header: 1018 >
    *[ Charging-Rule-Name ] — Spa-Profile:voip+data
    [ PCC-Rule-Status ]    — INACTIVE (1)
    [ Rule-Failure-Code ]  — GW/PCEF_MALFUNCTION (4)
    

Charging-Rule-Report ::= < AVP Header: 1018 >
    *[ Charging-Rule-Name ]      —  Sub-Profile:prem
    [ PCC-Rule-Status ]          —  INACTIVE (1)
    [ Rule-Failure-Code ]        —  GW/PCEF_MALFUNCTION (4) 

Failed-AVP ::= < AVP Header: 279 >        
    Charging-Rule-Name = Spa-Profile:voip+data

If the directive is passed to the node through RAR, the node responds with the following RAA message:

Failed-AVP ::= < AVP Header: 279 >
    Charging-Rule-Name = Spa-Profile:voip+data 
 
Result-Code ::= < AVP Header: 268 > = DIAMETER_INVALID_AVP_VALUE (5004)

Similarly, if the number of filter entries for each entry type (NAS-Filter-Rule — host-specific or Alc-NAS-Filter-Rule-Shared — shared) exceeds the maximum supported number (see the 7750 SR Gx AVPs Reference Guide), the whole message fails the decoding phase.

The reason that the Result-Code AVP is present in the RAA message and not in the CCR-U message is that this code is only allowed to be present in the answer messages, according to the standard.