Contacting a paper author: best way to address an engineer I would like to send an email to a paper author, but I'm not sure how to address them.

The author is not a professor, 
their google+ profile says "Network Engineer" (in an important network company BBTW).
As far as I know has a degree and has several publications like articles, conference papers, RFC's.

I'm a Master degree student.

What form of address should I use?
Default to "Dear Mr. [last name]" (assuming you're sure the person is male).  If you're not sure the person is male, use "Dear [first name] [last name]".  Don't worry about other titles unless the person specifically uses "PEng." or other professional association designation after their name, in which case include that.