The interview process started with a casual chat about my background, experience, etc. Fairly standard questions and no surprises. The challenge begun when a service provider network topology was presented to me and an in-depth questioning about how traffic would move from one place to the other, starting from the very basics, and gradually increasing in difficulty until I was unable to answer questions. A strong understanding of the entire network protocol stack was required, from fundamentals all the way up to detailed knowledge of advanced subjects. Based on the individual, their mileage may vary on how long the interview goes and how difficult it is. I would expect the individual to have a strong service provider background and a strong understanding of different protocols.