Division 4.2 Connection type principal CS-SIS — backup CS-SIS

The required connection type for the interconnectivity between the principal CS-SIS and the backup CS-SIS must be an SDH ring or equivalent, meaning be open also for the new future architectures and technologies. The SDH infrastructure will be used to extend the local networks of both central units to create a seamless single LAN. This LAN will then be used for the continuous synchronisation between the CU and BCU.