Ss7 definition

Also known as Common Channel Signaling System 7 (CCS7), SS7 protocols were developed by AT&T in 1975 for use in the public switched telephone network (PSTN). The protocols were adopted and enhanced by the ITU-T in 1981, and are defined in the Q.7XX series of Recommendations. SS7 in a common channel signaling (CCS) system that uses channels separate from the communications channels for signaling and control purposes. In the United States, at least, SS7 operates not only over separate channels, but generally over a physically distinct network or subnetwork. SS7 significantly speeds call setup and call completion processes, allows access to databases that enable toll-free calling and number portability, and supports the CLASS (Customer Local Access Signaling Services) services such as caller ID, name ID, selective ringing (or priority ringing), selective call forwarding, call block (or call screen), repeat dial, call trace, and automatic call-back (call return). SS7 is fully deployed in all major TDM-based interexchange carrier (IXC) networks.While SS7 is largely deployed in the major incumbent local exchange carrier (ILEC) networks in developed countries, older central office (CO) switches do not support it. See also all of the features listed above. See also CCS, CLASS, CO, ILEC, IXC, and signaling and control.
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