CDR collection does storage of usage information in the forma of Call Detail Records from VoIP network infrastructure (SIP Proxies, VoIP gateways and Session Border Controllers).
SIP
In the SIP world there are different CDR types:
- Start and stop messages (which defines the beginning and end of a call)
- SIP messages (per transaction)
- SIP traces (per packet)
A CDR collection system would calculate call duration from individual INVITE and BYE messages generated by SIP proxies. As there is no guarantee that BYE message will be received a CDR collection could do the following:
- Match information from SIP Proxy with call information from PSTN gateway (if call went to PSTN world)
- Match information from Session Border Controller for IP calls. As SBC stay in media path can always accurately determine when the last information was sent/received.
April 7, 2023
Phone System 