eference model processing dimension (defined by AML) private automatic branch exchange point code (defined by MTP, part of CCS) pulse code modulation process control system (defined by AML) packet data channel plesiochronous digital hierarchy packet data network protocol data unit (defined by OSI) packet handler physical media connection (defined by AML) public land mobile network plain old telephony service postcondition (defined by AML) precondition (defined by AML) primitive service (defined by AML) or packet switching primitive service identifier (defined by AML) public switched telephony network quality of service routing analyser (defined by AML) radio link control (part of GPRS) route manager (defined by AML) real-time object-oriented modelling remote operation service element (part of OSI) resource system (defined by AML) resource system model (defined by AML) SAP handler (defined by AML) service access point (defined by AML) SAP identifier (defined by OSI) segmentation and reassembly (part of ATM) signalling connection control part (part of CCS) service control function (part of IN) service control point (part of IN) synchronous digital hierarchy specification and description language (specified by ITU-T) service data unit (defined by OSI) service element (defined by AML) service element identifier (defined by AML) serving GSN (part of GPRS) service indicator (the SAPI of MTP, part of CCS) service information unit (defined by AML) Abbreviations sysnet modelling (defined by AML) short message service SNDCP subnetwork dependent convergence protocol (part of GPRS) simple network management protocol (part of Internet) SONET synchronous optical network structured query language service relation (defined by AML) special resource function (part of IN) service relation identifier (defined by AML) service switching function (part of IN) subsystem number (defined by SCCP, part of CCS) service switching point (part of IN) signalling system seven (same as CCS) switch controller (defined by AML) transmission transpor