SCCP Architecture

As shown in Figure 9-3, SCCP is composed of the following four functional areas:

• SCCP connection-oriented control (SCOC)— Responsible for setting up and releasing a virtual connection between two SCCP users. SCOC can offer features including sequencing, flow control, and segmentation and can override congestion procedures by assigning data priority. The section, "SCCP Connection-Oriented Control (SCOC)" describes SCOC in more detail

• SCCP connectionless control (SCLC)— Responsible for transferring data between SCCP users without creating a virtual connection. SCLC is described in the "SCCP Connectionless Control (SCLC)" Section. In addition to segmentation, it can perform limited sequencing.

• SCCP routing control (SCRC)— Provides additional routing beyond that offered by MTP3, through the use of global titles. The "Global Title Routing" section fully explains global titles.

• SCCP management (SCMG)— Responsible for tracking application status and informing SCMG at other SCCP nodes, as necessary. It is described later in this chapter in the section, "SCCP Management (SCMG)."

The term SCCP Users refers to the applications that use SCCP's services. These are primarily database-driven applications. Such applications use the services of TCAP described in Chapter 10 for peer application layer communication and the services of SCCP for managing the transport of messages between those applications.

Applications that use the services of SCCP are known as subsystems.