I received a phone call from the recruiter. He arranged a technical phone screen with the hiring manager.

Three hours later, I got a call from the recruiter asking for a time for a second phone screen.

The second phone screen was with a senior technical member of the hiring team. It was completely technical. He started with technical questions related to my experience, followed by questions related to problem-solving, troubleshooting, and testing methods.

There weren't many difficult questions. They were mostly relevant to telephony.

I answered them in depth as much as possible. The job deals with the protocol stack from top to bottom, which was not mentioned as a requirement.

I was familiar with mostly Layer 3, and my answers were limited to that perspective. They expected details across all layers of the protocol stack.