Netflix says its service during peak hours is getting noticeably slower. It’s putting the blame on cable ISPs, but it seems more a case of what those companies aren’t doing than what they are.

The precise details of the slowdown seem to vary depending on which account you read, but the biggest problem seems to be for customers on Verizon’s FiOS service. Netflix says peak viewing time speeds there have slowed by 14 percent over the past month.

The way Netflix adjusts picture quality based on the connection means many users whose speed was previously just good enough to get a full HD connection are now getting visibly lower quality.

Strictly speaking it’s not a net neutrality issue as such, despite the recent court ruling in favor of ISPs. The cable firms appear treating the traffic they do handle in an equal manner.

The issue is instead the route the data takes from Netflix’s servers to the ISPs (who then pass it on to customers.) Netflix wants to set up a system by which it gives the data directly to the ISPs. However, Verizon and company say that as Netflix traffic involves so much data flowing in one direction, they’re only willing to set up a direct connection for a fee.

Instead Netflix data has to be routed through third-party services, most notably a firm called Cogent Communications. Cogent says that increasing demand means it can’t maintain high speeds for everyone at peak times unless the ISPs upgrade the link between Cogent and the ISPs.

The ISPs are refusing to do so. While there’s no way to prove it, the implication is that they are intentionally holding out on upgrades that would normally be considered a no-brainer, a deliberate move aimed at causing Netflix headaches and pressuring them into agreeing to pay for a direct connection.

For their part the ISPs deny using any unfair leverage. Verizon says it continues to treat traffic equally and is “open to ideas about the best ways to alleviate congestion so all customers benefit from the best quality of service possible.”