Gy/Ro Diameter Answer Message Processing

When OC-DRA forwards a Diameter Request message to DRL for routing, it requests that the corresponding Answer response message is forwarded back to PCA for Answer message processing.

Note: PCA requests that DRL forward all Gy/Ro Answers back to PCA for Answer message processing in order to maintain measurements. PCA processing all Gy/Ro Answers for accounting purposes is not expensive since the OC-DRA and the routing layer are guaranteed to be on the same physical server (different threads in the same process) and avoids lots of explaining about why some measurements are not pegged.

On receipt of a Gy/Ro Diameter Credit Control Application Answer message, OC-DRA performs validation checks on the contents of the message before it attempts to relay the message. Validation is limited to header information and routable Attribute Value Pairs (AVPs) that are used by OC-DRA for making processing decisions for Answer message routing.

OC-DRA validates the Application ID and Command Code in the Diameter Answer message for consistency. OC-DRA supports the Gy/Ro DCCA Answer messages. If OC-DRA receives a Diameter Answer message with a Command Code that is not supported, PCA will send the Answer message without modification to the downstream peer that initiated the Diameter transaction.

Command Name	Abbreviation	Code	Source	Destination
Credit-Control-Answer	CCA	272	OCS	CTF
Re-Auth-Answer	RAA	258	CTF	OCS

OC-DRA makes Diameter Answer message processing decisions based on a small subset of AVPs defined in the Diameter protocol for online charging. Those Diameter AVPs that are used specifically by OC-DRA for making routing decisions. These AVPs are shown in Table 1 and marked "M" or " -" to indicate which ones are mandatory or not used for each of the supported Gy/Ro DCCA Answer messages.

Diameter AVPs used by OC-DRA for Answer Message Processing
AVP Name	AVP Code	Used In		Value Type	Description
AVP Name	AVP Code	CCR	RAR	Value Type	Description
Session-Id	263	M	M	UTF8String	Contains the session identifier.
Result-Code	268	M	M	Unsigned32	Contains whether a particular request was completed successfully (i.e., 2xxx) or an error occurred (non-2xxx).
Origin-Host	264	M	M	DiamIdent	Contains the end point that originated the Diameter message.
Origin-Realm	296	M	M	DiamIdent	Contains the realm of the originator of the Diameter message.
Auth-Application-Id	258	M	M	Unsigned32	Contains the application ID of the Diameter Credit Control Application which is 4.
CC-Request-Type	416	M	-	Enumerated	Contains the transfer type: event for event based charging and initial, update, terminate for session based charging.

OC-DRA validates all the AVPs listed except for those that have already been validated by DCL and DRL prior to the invocation of OC-DRA which includes the Origin-Host AVP and the Origin-Realm AVP. OC-DRA Diameter message header field and AVP validation requirements.

Once validation of the Diameter Answer content is complete, OC-DRA performs Diameter Answer message processing and routing.