 Scope One of the ISSI Performance Recommendations for Voice Services provides agreed upon (by manufacturers and end users) average and maximum values for the IVS-CSD and IVS-MTD performance parameters described in the ISSI Measurement Methods for Voice Services standard.The ISSI Conformance testing for Voice Services defines a set of procedures to test the conformance between two RF Sub-systems using an IP backbone network.The procedures define reference-signaling sequences for SU-to-SU and Group call scenarios.