Signalling Information Field (SIF): message flow -----> | +-E + - - - - - Parameters ----------+------------+---+-----+-----+- - - | O |User message data|Message header|Message type|SLS| OPC | DPC | SIO +-P-+- - - - - - - - -+--------------+------------+-4-+--14-+--14-+- - - | | | | |-routing label-| | | |-----label-----| | +----------------------+ | | +------------------+---------------------+ TCAP |Component Portion | Transaction Portion | +------------------+---------------------+ DPC - destination point code (cod: binary) OPC - originating point code (cod: binary) SLS - signalling link selection The parts of the SCCP messages: 1 routing label (Q.704/2) 2 message type code 3 mandatory fixed part 4 mandatory variable part 5 Optional part The Message header includes called and calling-party addresses and local references(Technical Information)