as i understand it, these very specific definitions, for example Answer Seizes Ratio ASR] in SIP terms i.e. Session Establishment Ratio & were produced by the IETF to standardize on measuring performance between carriers . I was wondering if anyone was using them internally and also with any of your interconnect partners? Another example would be Session Defects Ratio (SDR) is the percentage of call attempts receiving the following responses, in relation to total call attempts or INVITES: o 500 Server Internal Error o 503 Service Unavailable o 504 Server Timeout Or do you just measure 503?s? Thanks , Richard Jobson E-mail:richard at teraquant.com Web:www.teraquant.com <http://www.teraquant.com>