[ss7] signalling system no. 7
signaling system no. 7 (ss7) is a set of telephony signaling protocols developed in 1975, which is used to set up and tear down most of the world's public switched telephone network(pstn) telephone calls. it also performs number translation, local number portability, prepaid billing, short message service (sms), and other mass market services.
in north america it is often referred to as ccss7, abbreviated for common channel signaling system 7. in the united kingdom, it is called c7 (ccitt), number 7 and ccis7(common channel interoffice signaling 7). in germany, it is often called zzk-7 (zentraler zeichengabekanal nummer 7).
the only international ss7 protocol is defined by itu-t's q.700-series recommendations in 1988. of the many national variants of the ss7 protocols, most are d on variants of the protocol as standardized by ansi and etsi. national variants with striking characteristics are the chinese and japanese (ttc) national variants.
the internet engineering task force (ietf) has defined the sigtran protocol suite that implements levels 2, 3, and 4 protocols compatible with ss7. sometimes also called pseudo ss7, it is layered on the stream control transmission protocol (sctp) transport mechanism.
know more:- https://en.m.wikipedia.org/wiki/signalling_system_no._7