ISO/IEC 15991:2003 Preview
Information technology -- Telecommunications and information exchange between systems -- Private Integrated Services Network -- Specification, functional model and information flows -- Call Priority Interruption and Call Priority Interruption Protection supplementary services
This standard was last reviewed and confirmed in 2008. Therefore this version remains current.
The electronic version of this International Standard can be downloaded from the ISO/IEC Information Technology Task Force (ITTF) web site
ISO/IEC 15991:2003 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 This edition of ISO/IEC 15991 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. ISO/IEC 15991:2003 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.