Based on the reference connections for ISDN circuit switched services and the grade-of-service (GOS) parameter values contained in Recommendation E.721, this Recommendation provides appropriate reference connections for the S.S. No. 7 network and identifies the signalling network GOS parameters and their target values. Further, the Recommendation also provides guidelines for partitioninghllocafhg the signalling network end-to-end GOS to the basic components of the S.S. No. 7 network, The reference connection and GOS parameters and values for source transaction type services requiring data base lookup are also included.