how SLP works for OST optimized duplication

Hi All

would like to know how slp works for  OST optimized duplication . I heard data transfer is OFF of mediaserver, and mediaserver role is just to establish connection and data flows between data domains .

But bpdm runs on mediaserver , and it means its performing some IO operation on disk.SO is it true that data directly flows between data domains ? not mediaserver reads from one datadomain and writes to other ? please clarify