Certification is a generic level of functionality to be expected for hardware running on an Ubuntu Release. Part of the challenge is to identify what hardware components should be included in the test.
The aim is to cover all widely accepted components, while excluding fringe ones that may only be of interest to a small set of the user base.
In the past it has been a bit hard to understand what components were tested for Certification and this has lead to questions like “Why is the finger reader scan not working in this certified system?” when the answer is simply that certification does not test for finger-reading functionality.
You can now see at a high level what certification includes for both servers and clients (click on the image to see the full list):
Victor Tuson Palau 
And what about network controllers (ethernet or wireless) ?
that is cover on the networking subsystem