TAILIEUCHUNG - Signaling System No.7 Protocol Architecture And Sevices part 30

Chapter 9. Signaling Connection Control Part (SCCP) The Signaling Connection Control Part (SCCP) is defined in ITU-T Recommendations [58–63] | Chapter 9. Signaling Connection Control Part SCCP The Signaling Connection Control Part SCCP is defined in ITU-T Recommendations 58-63 and for North American markets in ANSI 2 . SCCP sits on top of Message Transfer Part 3 MTP3 in the SS7 protocol stack. The SCCP provides additional network layer functions to provide transfer of noncircuit-related NCR signaling information application management procedures and alternative and more flexible methods of routing. NOTE Technically SCCP can also transfer circuit-related signaling information however this is an exception. As shown in Figure 9-1 the combination of the MTP and the SCCP is termed the Network Service Part NSP . The NSP follows the principles of the OSI reference model as defined in Recommendation 99 as such it provides a subset of the Layer 3 services which are defined in Recommendation 100 . Figure 9-1. SS7 Stack with the Network Service Part NSP Highlighted SCCP was developed after the MTP and together with the MTP3 it provides the capabilities corresponding to Layer 3 of the OSI reference model. Because SCCP is OSI Layer 3 compliant in theory it can be transmitted over any OSI-compliant network. Because the MTP was originally designed to transfer call-control messages coming from the Telephony User Part TUP it was therefore designed to transfer only circuit-related signaling. In combination with the MTP the SCCP can transfer messages that are not circuit-related. These messages are used to support services such as toll-free calling Local Number Portability LNP and Completion of Calls to Busy Subscribers CCBS in Intelligent Networks and mobility roaming and SMS in cellular networks. SCCP provides the following additional capabilities over the MTP Enhances MTP to meet OSI Layer 3 Powerful and flexible routing mechanisms Enhanced transfer capability including segmentation reassembly when message is too large to fit into one Message Signal Unit MSU Connectionless and .

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