Telecommunications Signaling
Highlights the conventions of signalling systems and provides a detailed assessment of their architecture.
TABLE OF CONTENTS Telecommunications Signaling
Chapter 5: Signalling Connection Control Part
5.1 Introduction
The evolution towards more use of non-circuit-related signalling requires a comprehensive platform upon which information can be transferred. The Signalling Connection Control Part (SCCP)1 of CCSS7 is specified to provide the means to establish logical (i.e. non-circuit-related) signalling connections. It also provides a capability to transfer elements of information termed 'Network Service Data Units' (NSDUs). The SCCP is defined in terms of the Open Systems Interconnection (OSI) 7-Layer Model.
5.2 Architecture
5.2.1 OSI Model
Although the MTP is a comprehensive transfer mechanism, it was specified before the OSI Model was applied to telecommunications signalling systems. The MTP adequately covers Layers 1 and 2 of the OSI Model, but a number of functions need to be added to the MTP to provide adequate Layer 3 functions. For flexibility in future network environments, it is important that CCSS7 fits within the OSI 7-Layer Model approach for non-circuit-related applications.
It is the SCCP that provides functions in addition to those of the MTP in order to offer an OSI Network Service. The combination of the MTP and the SCCP is called the Network Service Part (NSP). By offering a Network Service, the NSP can be utilised by a variety of users.
Chapter 3 describes how the SCCP fits into the overall architecture of CCSS7 and provides the interface between Layers 3 and 4 of the OSI Model.
5.2.2 Structure
The structure of the SCCP is illustrated in Fig. 5.1.
Figure 5.1: SCCP Structure
The SCCP has four main functional groups. The...
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