e functions direct the message to the proper signaling link or user part. 2. Signaling Network Management Functions. These control real-time routing, control, and network reconfiguration, if required. Layer 4 is the user part. Each user part defines the functions and procedures peculiar to the particular user, whether telephone, data, or ISDN user part. The signal message is defined by CCITT Rec. Q.701 as an assembly of information, defined at layer 3 or 4, pertaining to a call, management transaction, and SO on, which is then transferred as an entity by the message transfer function. Each message con- tains "service information," including a service indicator identifying the source user part and possibly whether the message relates to international or national application of the user part. The signaling information portion of the message contains user information, such as data or call control signals, management and maintenance information, and type and format of message. It also includes a "label." The label enables the message to be routed by layer 3 through the signaling network to its destination and directs the message to the desired user part or circuit. On the signaling link such signaling information is contained in the message signal units (MSUs), which also include transfer control functions related to layer 2 functions on the link. There are a number of terms used in SS No. 7 literature that should be understood before we proceed further: Signaling Points Nodes in the network that utilize common-channel signaling; Signaling Relation (similar to traffic relation). Any two signaling points for which the possibility of communication between their corresponding user parts exist are said to have a signaling relation; Signaling Links Signaling links convey signaling messages between two signaling points; Originating and Destination Points The originating and destination points are the loca- tions of the source user part function and location of the receiving user part function, respectively; Signaling Trans