Hi there,
An expert in any discipline is a title with a lot of weight!
I'd say it is a kin to a Principle/ Lead Network Engineer. Tier 3 position (no talking on the phone to users :) ), creates and manages the deployment of LLDs, leads any priority 1 incidents, liaises with other IT stakeholders to manage their expectations and takes great pleasure in handing said priority 1 incidents back to the server team!
Maybe a little of HLD work to, but depending on the size of the organisation they will be network designers for that.
cheers,
Seb.
