ts of one or several actions (Figure 6.2). An action consists of a series of commands to modify or examine the context property. Each action usually specifies a context identifier (Figure 6.2). Each command consists of an identifier and a termination descriptor. The descriptor contains the parameters of a termination concerning a command. A descriptor consists of a name and a list of elements (Figure 6.2). H.248 Message Message Transaction Transaction Transaction Transaction header Transaction Action Action Action identifier Context Command Command Command identifier Termination Termination identifier descriptor Figure 6.2. H.248 structure message The terminations which are physical entities have a semi-permanent existence like a time-slot in a time-division multiplexing (TDM). Interconnections The temporary terminations are real-time transport protocol (RTP) flow, in the case of the interface with the IP network. The protocol provides commands to manipulate the logical entities, the contexts and the terminations of the connection model. ADD command adds a termination to a context. Applied to the first termination of a context, it also serves to create a context. MODIFY command modifies the properties of a termination. SUBTRACT command disconnects a termination from its context and sends back statistics about the participation of this termination in this context. Applied to the last termination of a context, it serves to cancel this context. MOVE command moves a termination to another context. AuditValue command sends back the current states of the properties and statistics associated with the terminations. AuditCapabilities command sends back all the possible values of termination properties authorized by the IMS-MGW gateway. NOTIFY command allows the IMS-MGW gateway to inform the MGCF entity about the development of events in this gateway. ServiceChange command allows the IMS-MGW gateway to signal to the MGCF entity that a termination or a group of terminations is about to be disabled or has just been enabled. 