Two - three phone screens, one day long interview. Some of the people you'll be interviewing with are some of the brightest from carrier, service provider and content, so at senior level+, I'd say be ready for anything. This was the most nervous I'd ever been for an interview, vomited violently the night before my flight and was unable to get any sleep, which at the time I felt crippled me for the interview. But look, everything happens for its reasons (the trick is they're all self generated), and I just wasn't ready for that level of validation.
Most of the material on the phone screens was standard, but you were allowed to couch the portrayal in generalities - understanding of forwarding behavior and mechanics was essential, everything was close to platform neutral. I did find that when I was struggling, some of the coaching started to coalesce around specific platforms, but no biggie. Some of it approached deep, be prepared to unpack transport layer behavior in relation to applications + time + distance.
The recruiter mentioned they would be changing the interview process to multi-day, which will make it more difficult on the candidate logistically, however, future candidates will find metabolizing what they're feeding much easier. It will allow you to hit the design portion of the interview much much easier. Didn't have the "ah-ha!" moment until I had gotten to sleep.