CSA ISO/IEC 15991:04 (R2019)

CSA Preface Standards development within the Information Technology sector is harmonized with international standards development. Through the CSA Technical Committee on Information Technology (TCIT), Canadians serve as the Canadian Advisory Committee (CAC) on ISO/IEC Joint Technical Committee 1 on Information Technology (ISO/IEC JTC1) for the Standards Council of Canada (SCC), the ISO member body for Canada and sponsor of the Canadian National Committee of the IEC. Also, as a member of the International Telecommunication Union (ITU), Canada participates in the International Telegraph and Telephone Consultative Committee (ITU-T). This International Standard was reviewed by the CSA TCIT under the jurisdiction of the Strategic Steering Committee on Information Technology and deemed acceptable for use in Canada. (A committee membership list is available on request from the CSA Project Manager.) From time to time, ISO/IEC may publish addenda, corrigenda, etc. The CSA TCIT will review these documents for approval and publication. For a listing, refer to the CSA Information Products catalogue or CSA Info Update or contact a CSA Sales representative. This Standard has been formally approved as a National Standard of Canada by the Standards Council of Canada. Scope This International Standard specifies the Supplementary Services Call Priority Interruption (SS-CPI) and Call Priority Interruption Protection (SS-CPIP), which are applicable to various basic services supported by Private Integrated Services Networks (PISN). Basic services are specified in ISO/IEC 11574. NOTE 1 - This edition of this International Standard does not apply to the circuit-mode Multiple Rate Bearer Service. SS-CPI is a supplementary service that allows a call request for a priority call to proceed successfully in the case that there is no user information channel available. This is accomplished by force releasing an established call of lower priority. SS-CPIP is a supplementary service that allows for the protection of calls against interruption from other, priority, calls. SS-CPI and SS-CPIP are described separately because SS-CPI is a service used by a calling user, and SS-CPIP is a service used by either a calling user or a called user. Supplementary service specifications are produced in three stages, according to the method described in ETS 300 387. This International Standard contains the stage 1 and stage 2 specifications of SS-CPI. The stage 1 specification (clause 6) specifies the general feature principles and capabilities. The stage 2 specification (clause 7) identifies the Functional Entities involved in the supplementary service and the information flows between them.