I've had it yesterday in both csgo/dota. Just changed my IP by restarting the router and it was back to normal.
I think your in the same boat as chrisJ now. During rush hour your internet will suck :D
Did you contact your provider and see if their logs showed something strange?
They might be able to check it live once you try to play ESEA and the same happens.
wtf at some of these suggestions,
log into the modem and look for game mode or an allow list. It will be some NAT filter rule, the modem thinks it's an intrusion and locks it down.
What brand of modem is it?
Still not working guys...
I can play cod without any problems, so it has something to do with steam or CSGO itself..
mate is valve
thousands randomly get it sometimes