We recently switched from a business-class cable connection (100/20) to a symmetrical (100/100) fiber one. This serves a front office, a media department, and several client computers on any given day.
While on the former service we up/downloaded many multi-gig media files from client and graphics computers, with no problems except what you'd expect when several people are competing for limited bandwidth. It all worked, it just slowed down.
But with this new service we get periods where (the supplier says) we "saturate" the connection and all connectivity ends for everyone. What is really going on here? I would guess most traffic is 'web-based' in that it's mediated through ports 80/443, with some FTP.
And some of the file transfers do proceed at amazing speeds -- the remote ends can easily keep up with our puny 100Mb/s, where in the past it was rare to see any given connection exceed 30Mb/s. It's just that when three or more of these up/down transfers are going on, it eventually, to put it crudely, 'clogs the pipes'.
So what's really going on? Why would a faster service with a more dedicated channel be susceptible to this sort of degradation? I've always thought of TCP as somewhat self-balancing in that multiple connections would degrade together, that one or two connections couldn't 'hog' the bandwidth. Is that wrong?