1) Brief history about yourself. 2) What is OSS/BSS? 3) What is Orchestration? 4) Complete Order Journey. 5) Which product did you supported. Basically interviewee should be having a good grip on what he/she has done and about OSS/BSS, its different components. If you have specifically worked in any components i.e. Orchestration, Work Force, Inventory etc than you should good knowledge about it. In my case I had 3 rounds each went for an hour but the panel was very supportive.