For single floor homes with a basement the basement may be the best path.
Cable drop through attic multistories.
My cable tv is distributed through the attic so it seemed like a good solution to run my home network through there as well.
By using a drill bit sized large enough for the cable.
These methods will work for any cable telephone network thermostat power etc.
I ve mounted a junction box on the stud by cutting into the wall then made a small pilot hole into the attic through the ceiling to register the main hole through the 2x4.
There s a 2x4 at the top of the wall with vertical 2x4 studs.
I have run the odd cable in my house wood frame wallboard by drilling down from the attic into the hollow wall.
To drill through a rug make a small cut in the rug with a utility knife and then drill down through the cut.
Drop the string and catch it in the wall cutout and use that to pull the cable through.
Install coaxial cable cable tv or satellite tv cables concealed in wall spaces from non living spaces above or below.
The upstairs room solution is pretty obvious go vertically up through the wall in the computer room into the attic space run the cables to where they need to go then drop then down into the rooms punch them into the back of a wall plate done.