This counter reports the total number of calls that failed to complete successfully through the CUSP system since the last counter reset. An admin tracks this counter's growth rate relative to cuspTotalCalls to detect deteriorating call quality or routing problems, prompting investigation into causes like licensing rejections or server group outages. A sharp jump in cuspTotalFailedCalls right after cuspLicenseState changes to outofcompliance would confirm to the admin that licensing, not a network problem, is behind the failures.