When Netflix agreed to pay Comcast for a direct connection to the ISP's network, video performance improved immediately . Verizon subscribers aren't so lucky. Although Netflix and Verizon confirmed on April 28 that they had struck a paid peering deal , performance continued to drop in May and could remain poor for months while the companies upgrade infrastructure.

"Verizon FiOS is down two slots and now ranks behind DSL providers Frontier and Windstream," Netflix wrote today after releasing its monthly speed index.

In the US, Netflix performance on Verizon FiOS dropped from 1.99Mbps in April to 1.90Mbps in May, and performance on Verizon DSL dropped from 1.08Mbps to 1.05Mbps. This is the average performance of all Netflix streams on each ISP's network. The drops are small, but they show that the paid peering deal didn't make any immediate impact.

Netflix has continued to blame Verizon for poor performance, and Verizon last week sent a cease and desist letter demanding that Netflix stop bad-mouthing the ISP. Verizon says this dispute isn't preventing network upgrades, but they are proceeding slowly nonetheless. A Wall Street Journal article from last week says:

The connections are just getting set up. Data from network research firm Renesys show the two networks already set up a test connection to carry video in the Dallas area, but major networks typically need links in dozens of cities to deliver traffic effectively. Verizon said it plans to fulfill the terms of its agreement with Netflix over the next few months. "We are working on the first 13 cities, and we do plan to have everything done in 2014," said Verizon spokesman Bob Elek. "All of this kerfuffle that is going on isn't affecting that."

A Verizon spokesperson confirmed to Ars today that the Journal's "reporting is correct," but they company didn't provide any further details in response to our questions. Netflix declined to say why it's taking longer to set up connections with Verizon than it did with Comcast.

Verizon VP David Young told CNET, "We can't just snap our fingers and the network is upgraded. We need new facilities. We have to do the equipment engineering. Build it and test it. We are doing all of that right now. And it should be completed during this year." When finished, Netflix's connection to the Verizon network will supply "adequate capacity to satisfy the needs of their subscribers."

The cease and desist letter Verizon sent to Netflix was spurred by Netflix sending error messages to customers that blame ISPs for poor performance in cases when a customer's stream quality declined. "We are testing this across the US wherever there is significant and persistent network congestion," Netflix said today. "This test is scheduled to end on June 16. We will evaluate rolling it out more broadly."

Netflix performance on Comcast also fell a bit in May, but just from 2.77Mbps to 2.72Mbps. Comcast previously moved from 1.51Mbps in January 2014 to 1.68Mbps in February, 2.5Mbps in March, and 2.77Mbps in April. A Netflix spokesperson told Ars that the links between Netflix and Comcast are "almost" complete.

Netflix was previously sending traffic over congested links between the ISPs and transit providers such as Cogent and Level 3. Those companies have also argued with ISPs over whether they should have to pay the Internet providers for direct network access.

Netflix performance on AT&T was just 1.7Mbps in May, worse than Verizon FiOS. AT&T said in February that it's negotiating to get payments from Netflix in exchange for a direct network connection, but no deal has been struck yet.