it was 3D Realms official BBS
https://nitter.privacyredirect.com/ScottApogee/status/159372... Scott Miller - Apogee/3D Realms Founder :
>BBS's (bulletin board systems) were the backbone of the online world before the Internet came along in 1995. Apogee teamed up with Dan Linton's BBS, called Software Creations, and we poured $200k+ into it to grow it to nearly 140 call-in nodes with a T3 (high bandwidth) line.
I seem to recall that the release of DooM caused BBSs around the world to be backed up for ages.
I was lucky enough to have a T1 in 1995 and still think to this day that 1.544 Mbps is enough to do real work.