ss7
...tive call acceptance, selective call forwarding and selective call rejection. These features are referred to as CUSTOM LOCAL AREA SIGNALING SERVICES (CLASS) – These features are only possible if the local office is connected into the SS7 network. The features will only work if the call is placed between 2 SS7 networks. Common channel signaling technique, using a separate network of computers to send and receive messages as signals, has been adopted by the international community as CCIS #7 and is referred to as signaling system 7 SS7 was developed to handle ISDN SS7 does not use the voice path, it will issue a request for a continuity check as part of the call setup message SS7 was designed to place addressing and supervisory signals over a separate network from the voice network. In SS7, the first layer, or physical layer, is called the Signaling Data Link Layer. It is a Full-Duplex connection between components of the SS7 network and normally operates at 64kbps. The second layer is the signaling link layer and is software that provides flow control, error detection, error correction, and delivery of data packets in the proper sequence. The third layer is the Signaling Network Layer and is software designed to route messages from source to destination and from signaling layer to a user defined fourth layer called the Signaling Connection Control Part (SCCP). The SCCP is software that is application specific such as the upper-layer software used in a SCP database. The first Three layers of the software are called Message Transfer Part (MTP); these three layers form an interface to conform with CCITT now known as (International Telecommunications Union) x.25. This MTP is a datagram service. Datagram’s are p...