sunrpc on port 111 and domain on port 53

[Aaron Brashears <aaron@myplay.com>]

I'm making some efforts to tighten up security on my home server. I've
been closing some services that I don't need, and after thinking I'd
cleared everything out, I did an nmap scan of the box. Everything was as
it should be except for sunrpc on port 111 and domain on port 53. I
couldn't find any packages with dpkg -l which contained any part of that
string. Plus, there is no whatis or man information.

What are those services? What packages are they kept in?