Broadcast packet meltdown
On very slow or particularly large networks, as judged by the state of the art when Doom was released in 1993, the broadcast packet netgame system employed by early Doom versions could crash the network. Packets were sent to every computer on the network, even if a Doom game was not running on it. Slow computers on the network would also suffer performance problems if their network adapter could not handle the traffic. id Software addressed the issue in version 1.2.
The Jargon File cites Doom as an example of "network meltdown" due to overuse of broadcast packets, but does not mention the fix.