Mapping network address onto signaling relations Selecting operational functions during data-transfer phase (e.g., layer service selec- tion) Providing means to distinguish network connections Transporting user data (within the request) 14.11.4.2 Data Transfer Phase. The data transfer phase functions provide the means of a two-way simultaneous transport of messages between two endpoints of a signaling connection. The principal data transport phase functions are listed below. These are used or not used in accordance with the result of the selection function performed in the connection establishment phase. Segmenting/reassembling Flow control Connection identification NSDU delimiting (M-bit) Expedited data Missequence detection Reset Receipt confirmation Others 60&M stands for operations and maintenance. CCITT SIGNALING SYSTEM NO. 7 14.11.4.3 Connection Release Functions. Release function disconnect the signal- ing connection regardless of the current phase of the connection. The release may be performed by an upper-layer stimulus or by maintenance of the SCCP itself. The release can start at each end of the connection (symmetric procedure). Of course, the principal function of this phase is disconnection. 14.11.5 Structure of the SCCP The basic structure of the SCCP is illustrated in Figure 14.9. It consists of four functional blocks as follows: 1. SCCP Connection-Oriented Control. This controls the establishment and release of signaling connections for data transfer on signaling connections. 2. SCCP Connectionless Control. This provides the connectionless transfer of data units. 3. SCCP Management. This functional block provides the capability, in addition to the signal route management and lower control functions of the MTP, to handle the congestion or failure of either the SCCP user or signaling route to the SCCP user. REQUEST (1) )2) REPLY N-CONNECT REQ. N-DISCONNECT IND. N-CONNECT RESP. N-CONNECT CONF. N-DISCONNECT REQ N-DISCONNECT IND Connection- N-DATA REQ. oriented N-DATA IND. transfer control (SCOC) N-EXP