There were long running issues between at least a couple major ISPs and Netflix back around 2014. Verizon was one. I think Time Warner Cable was the other, but I'm not positive. Since I personally experienced the effects of the Verizon incident, I will stick to describing that.
The backbone of the Internet is made of up Tier 1 ISPs. These are the biggest 'pipes', so to speak, and they include carriers like Cogent and Level 3. Most business and consumer ISPs are Tier 2 or Tier 3. This illustration might help:
The 'Internet' as we know it ultimately relies on Tier 1 networks to shuffle data across the globe, and those networks are all interconnected. Tier 1 providers, being the largest, all tend to be responsible for lots of traffic, and in order to get from Point A to Point B, traffic often has to cross more than one Tier 1 network. Tier 1 providers have "peering" agreements with each other that basically say "we won't charge our peers (other Tier 1 providers) for any traffic we exchange". It's always worked that way, and it works out well because they're all pretty similar in size, and in the grand scheme of things, the flow of traffic tends to be pretty equal.
Verizon is an outlier, because unlike pretty much every other business or consumer ISP you've heard of, Verizon is also a Tier 1 provider. Back in 2014, Netflix was using Level 3 to distribute its content, and Verizon's interconnect with Level 3 became highly congested. The results were readily apparent to users like me, who endured video quality in the range of 240p to 480p for streams that should have been 1080p. Keep in mind, I was paying Verizon for a 50/50 Mbps FiOS connection.
Normally, when this sort of thing happens, the affected peers simply connect a few more cables in the room where where their networks converge. Verizon refused to do that, hoping to extort some kind of monetary toll out of Netflix. In effect, they wanted Netflix to pay them to deliver the traffic that Verizon customers were already paying Verizon to deliver, at the speeds Verizon advertised. This, to me, was a ridiculous situation. Imagine you had to take a toll road to get to the store, and the government suddenly said, "if you take this road to the store, not only do you have to pay a toll, but the store has to pay a toll too." Seriously? No. You get paid once
, by one party.
Verizon saw things differently. They saw that most of the traffic they exchanged with other Tier 1s flowed one way: to Verizon customers. Someone should pay for that imbalance, right? Not so fast. Most users' ISPs are Tier 3 or Tier 2, meaning their ISP pays Tier 1 providers to deliver data, and the Tier 2 and 3 providers charge their customers a larger amount, then pocket the difference as profit. This bears repeating: for most business and residential ISPs, the transit costs are paid for by the customer
(e.g., you and me). Verizon was large enough that it made financial sense to become a full-blown Tier 1 provider. They would save a lot of money by not having to pay for peering agreements with the Tier 1 providers, thus keeping a larger chunk of their customers' subscription fees. Pretty smart move. Now, Verizon may have been large enough to be a Tier 1, but because they mostly serve end users, the traffic they exchange with other Tier 1s tends to be rather one-sided (we download a lot but upload relatively little). Despite the imbalance, the other Tier 1 providers went along with it, essentially saying, "ok, fine, you're pretty big now, so you can peer with us for free." To emphasize: this inherent traffic imbalance was a natural consequence of an arrangement that favored Verizon
. Pretty sweet deal, right? And how did Verizon respond? They went to Level 3's biggest customer and said, "okay, now you
." Naturally, Netflix told them to zark off, because that's just not how the Internet works. When users complained to Verizon, they tried to pass the blame off on Netflix. Level 3 stepped in and, in a rather detailed blog post that is no longer online, ripped Verizon a new one. Level 3 even offered to buy and install the hardware necessary to relieve the congestion, the costs of which would have been negligible to either party (a one-time cost of a few thousand bucks). Still, Verizon refused. Why? Because Verizon was losing customers to Netflix, whose streaming service competed with Verizon's own TV service. Verizon couldn't compete on the merits of their product, so they abused their position as gatekeepers instead. They allowed their interconnect with Level 3 to become congested, and they refused to fix it, even when it would have cost them nothing to do so. I, along with many other Verizon customers, suffered the consequences. We paid for service, and Verizon did not deliver. But there was collateral damage too: Level 3's other customers, and any Verizon customers trying to get data from them, got screwed along with us.
Long story short, Verizon tried to use its position as a large ISP to extort money out of a competitor, and their own users suffered the consequences. The Title II reclassification put an end to these kinds of shenanigans, and now those protections are gone.