Sentinel supports two CDR formats "out of the box". These are the AVP CDR format, and the legacy format.
Note that Sentinel can be configured to use a user provided CDR format, or even no CDRs.
An AVP CDR is an OpenCloud defined CDR that contains AVPs. This type of CDR is consistent with the approaches used in Diameter Ro and Diameter Rf interfaces. An AVP CDR contains AVPs that are standardised (e.g. 3GPP and IETF), or non-standardised (e.g. product specific or project specific).
AVP CDRs can almost be considered an "on-disk" form of the content contained in the Rf interface.
AVP CDRs are used by default in the Sentinel SIP service. The Sentinel SIP service can be configured to use the legacy format.
A legacy CDR is an OpenCloud defined CDR that is used in the Sentinel product set prior to (and during) the introduction of AVP CDRs. The product continues support for this format so that customers who use this format do not need migrate.
Legacy CDRs remain in use by the Sentinel SS7 and Sentinel Diameter services.