stem No. 7 network A transfer capability for network service signaling data units (NSDUs) with or with- out the use of logical signaling connections Functions of the SCCP are also used for the transfer of circuit-related and call-related signaling information of the ISDN user part (ISUP) with or without setup of end-to-end logical signaling connections. 14.11.2 Services Provided by the SCCP The overall set of services is grouped into: Connection-oriented services Connectionless services Four classes of service are provided by the SCCP protocol, two for connectionless services and two for connection-oriented services. The four classes are: 0 Basic connectionless class 1 Sequenced connectionless class 2 Basic connection-oriented class 3 Flow control connection-oriented class 14.11 SIGNALING CONNECTION CONTROL PART (SCCP) For connection-oriented services, a distinction has to be made between temporary signaling connections and permanent signaling connections. Temporary signaling connection establishment is initiated and controlled by the SCCP user. Temporary signaling connections are comparable with dialed telephone connections. Permanent signaling connections are established and controlled by the local or remote O&M function or by the management function of the node and they are provided for the SCCP user on a semipermanent basis. 6 They can be compared with leased telephone lines. 14.11.3 Peer-to-Peer Communication The SCCP protocol facilitates the exchange of information between two peers of the SCCP. The protocol provides the means for Setup of logical signaling connection Release of logical signaling connections Transfer of data with or without logical signaling connections 14.11.4 Connection-Oriented Functions: Temporary Signaling Connections 14.11.4.1 Connection Establishment. The following are the principal functions used in the connection establishment phase by the SCCP to set up a signaling connection. Setup of a signaling connection Establishment of the optimum size of NPDUs (network protocol data units) 