The Southern Cross network comprises two physically separate and diverse cables and is configured in self-healing rings to provide the capability of fully protected capacity at the network level.
Network Design Performance
The equipment used on Southern Cross has been designed to achieve 99.999% availability for Protected circuits. This equates to an annual average design objective of <5 minutes of network down-time every year significantly better than the industry average for single strand trans-Pacific cables of approximately 98% (7.3 days down-time per annum).
In accordance with telecommunications industry practices, the value 99.999% is based on theoretical component reliability calculations based on the expected failure rate of components used in the manufacture of the Southern Cross equipment. This measure has a confidence level of 90% and is applied to both Southern Cross and comparative single strand system calculations.
Southern Cross also has dual landings (two cable landing stations) in each of Sydney, Auckland, Hawaii. The West Coast of the USA also has two cable landing stations, but three access points for customer traffic connection. By offering two completely independent paths between each of these four destinations, Southern Cross can lessen the impact on Customers of a failure at any of our cable stations.
Real World Performance
Based on the submarine cable industry's history of external aggression, the availability for Southern Cross protected circuits, including allowance for external aggression, is expected to be better than 99.990%, equivalent to an average unavailability of less than 53 minutes per annum.
In contrast, >99% of Southern Cross protected circuits have achieved 100% availability per annum for the last 7 years.
Products – Protected versus Restored
To deliver even greater security, on our Protected product portfolio, path switching has been adopted to ensure customer capacity is always live by being transported simultaneously around both sides of the network - thereby delivering fully-protected capacity. In the case of a single segment failure, traffic on Protected circuits is switched to the protect path within a target time of 50 milliseconds.
In late 2009 Southern Cross introduced a range of Restored services, leveraging off the capacity from the Phase G upgrade, with the introduction of the Drop Restoration policy on qualifying N-Drop services. Under Drop Restoration, in the event of a failure of either of the two nominated paths (of the N-drop service), Southern Cross will switch the affected capacity to an alternate path within a target time of 5 minutes.