Signaling system 7 pdf

signaling system 7 pdf, 3, and 4 protocols compatible with SS7. In its 1980 Yellow Book Q. 7XX-series recommendations ITU-T defined the Signaling System No.

7 as an international standard. SS7 replaced SS6 with its restricted 28-bit signal unit that was both limited in function and not amendable to digital systems. While running on a transport based upon IP, the SIGTRAN protocols are not an SS7 variant, but simply transport existing national and international variants of SS7. Examples of control information are the digits dialed by the caller and the caller’s billing number. With CCS, it becomes possible to exchange signaling without first seizing a voice channel, leading to significant savings and performance increases in both signaling and channel usage. Usually only the dialed digits were signaled, and merely during call setup.

For charged calls, dialed digits and charge number digits were outpulsed. SS7, being a high-speed and high-performance packet-based communications protocol, can communicate significant amounts of information when setting up a call, during the call, and at the end of the call. This permits rich call-related services to be developed. The earliest deployed upper layer protocols in the SS7 suite were dedicated to the setup, maintenance, and release of telephone calls.

ISUP was later used in Europe when the European networks upgraded to the ISDN. NFAS is signaling that is not directly associated with the path that a conversation will traverse and may concern other information located at a centralized database such as service subscription, feature activation, and service logic. This makes possible a set of network-based services that do not rely upon the call being routed to a particular subscription switch at which service logic would be executed, but permits service logic to be distributed throughout the telephone network and executed more expediently at originating switches far in advance of call routing. It also permits the subscriber increased mobility due to the decoupling of service logic from the subscription switch. Another ISUP characteristic SS7 with NFAS enables is the exchange of signaling information during the middle of a call. SS7 also enables Non-Call-Associated Signaling, which is signaling not directly related to establishing a telephone call.

Public Switched Telephone Network following the same path as the associated facilities that carry the telephone call. This mode is more economical for small networks. The associated mode of signaling is not the predominant choice of modes in North America. This mode is more economical for large networks with lightly loaded signaling links. The quasi-associated mode of signaling is the predominant choice of modes in North America.