Have you've ever had the experience where even though it looked like there was no issues on your end for your internet connection, lots of websites are loading extremely slowly or not at all. Or maybe you've even had the opportunity to see the wonders of YouTube loading videos and 144p, despite the fact that you have fiber.
Well, if you've tried all the usual steps to fix your connection, like rebooting your router, or adjusting your DNS settings or switching to a wired Ethernet connection, and still nothing helps not even calling your ISP, chances are there's a peering issue to blame. But the heck does that mean?
Alright, so because the internet is not one centralized network, it has to work through, different physical networks connecting to each other through some sort of agreement.
The largest networks called Tier 1 networks, connect to each other using something called settlement-free peering. What this means is that they agree to carry each other's data without an expectation of payment.
Strictly speaking, peering technically refers to no cost arrangements such as these for the purposes of this article, we're using a broader definition where peering refers to any agreement between networks to carry data, including paid agreements.
Anyhow, these big Tier 1 networks can reach the entire internet without having to pay for the privilege. For example, our American viewers will recognize big names such as AT&T, CenturyLink, and Sprint, which have Tier 1 networks. However, most ISP are Tier 2 or Tier 3 networks.
A Tier 2 network can do some free peering with other networks, but has to pay money or purchase transit to Tier 1 services to access portions of the internet, while a Tier 3 network only purchases transit, and then sells the internet access they bought to consumers. 
Typically, all this behind the scenes buying and selling results in a seamless experience for the user. Whether you're trying to view a website hosted halfway around the world, or just watch video on Youtube, but sometimes, a poorly conceived peering agreement, can really gum up the works.
You see peering agreements usually include an understanding about how much bandwidth each network can use. If one networks data ends up hitting a bandwidth cap or overwhelming the second network, throttling, and slowdowns can result and that's something you're going to experience.
This famously happened with Netflix when Cogent a Tier 1 network that carry lots of Netflix traffic, had to dispute with Comcast, since Netflix traffic takes up a surprisingly large chunk of internet bandwidth. Its data ended up throttled when it hit Comcast servers before it was able to make its way to viewers at home dear to sheer volume. 
And because it puts so much load on Comcast, Comcast asked Cogent to start paying for access to its network. As previously the two were connected via settlement free peering when Cogent said law, lol no. Comcast fired back by essentially allowing all that traffic at the interconnection point to bottleneck. And guess what customers got choppy video until the two companies decided to bury the hatchet. But in the meantime, Netflix went straight to Comcast for a better deal and paid for the privilege of hooking up its servers directly to Comcast network, obviating some of the need to buy transit from Tier 1 Cogent
There have actually been a number of instances of peering shenanigans over the years, whether it be from one side's infrastructure, not being up to scratch, or business disputes, such as the Netflix example we just discussed. But if you're faced with slowdowns at home because of peering problems, you can try using a VPN and if that doesn't work, well there's not much else you can do other than wait for the problem to get resolved or just switch ISP is because you know what? We all have plenty of those to choose from right.
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