To maximise efficient use of bandwidth and performance, communication should be subscription based, by default.
The OPC UA interface is exception driven and a publishing interval of 2 seconds or less should be used between the SPCS and the DCS. Update rates from subsea to the SPCS is outside the scope of MDIS and can be much longer than 2 seconds. Maximum allowable update rates for individual controllers should be determined and based on system architecture and hardware capabilities.
Requirements should be developed on a project basis to provide sufficient bandwidth between the SPCS and DCS to ensure all commands, issued both during normal operation and shutdowns, are passed across the interface effectively.
Evaluation of communication performance and testing requirements should take into account any latency or communication limitations due to physical system architecture constraints between SPCS and the DCS. (i.e. radio communication).