I'm attempting to add ethernet to a bedroom. This will involve drilling a hole from the attic to route the cables behind the drywall. I expected to see 2×4 above the interior wall but found a tongue and groove 2×6 as shown in the photos below. It runs in parallel with the ceiling joists and ends about an inch away from the roof overhang. House is in California and built in 1958.
Does this beam have a name and what is the purpose? Can I drill down through it to route cables?