open-cgf provides a 3GPP-compliant charging gateway function (CGF) as a sink for SGSN, GGSN, and other streamed CDRs on the 3GPP Ga/Gz interface using GTP' (GTP prime). Refer to 3GPP 32.295. These are common packet-switched data elements of GSM/UMTS mobile telephone networks. It aims to supply a telco-grade solution to this common, albeit very specialized, need. It does not decode the ASN.1 CDRs, but simply and reliably writes them to disk for later processing.