Appendix 4: ITU-T Signalling System No. 6
Institution of Engineering and Technology eBooks · 1999
ITU-T Signalling System No. 6 (CCSS6) was the first CCS system to be implemented internationally. It was originally designed for use in the international network, but some flexibility is included to allow its use in national networks. It is an inter-exchange signalling system that was implemented widely, but it has now been superseded by ITU-T CCSS7. CCSS6 offers a wide range of features associated with CCS systems, including operation in the quasi-associated mode, error detection and correction mechanisms and re-routing capabilities in fault conditions. However, its main drawback is its limited evolutionary potential, caused by its lack of a tiered architecture. In a dynamic environment, CCSS7 offers far greater flexibility and evolutionary capability, particularly due to its structured architecture.