Overview
Signaling system No.7 (SS7) is made by International Telephone and Telegraph Consultative Committee (CCITT). SS7 is an international standard common channel signaling, which features high-speed transmission, potentiality of providing a great number of signals, powerful functions, flexibility and reliability. It can meet the signaling requirements of public switched telephone network (PSTN), global system for mobile communications (GSM), and intelligent network (IN).
Functional structure of the SS7 in the NGN is shown in Figure 6-1.
Figure 6-1 Functional structure of the SS7 in the NGN application
From the above figure, it can be seen that SS7 is divided into two parts: user part (UP) and message transfer part (MTP).
l Common MTP: It is to transfer signaling messages between various user functions reliably. The SS7 can be transmitted through TDM or IP network (The protocol is M2UA/M3UA).
l Independent user part applicable to different users: It is a functional entity which makes use of the transmission capability of the MTP, including ISDN user part (ISUP) and IN application part (INAP).
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