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by egd 2786 days ago
I'm not a network engineer, so take this with as much credibility as you'd give an explanation after a few beers:

Most network providers have peering agreements to handle reciprocal traffic flows. In other words, if you're Comcast, you send a shit-ton of traffic to, say, Verizon. But Verizon also sends a shit-ton of traffic to you, as well. Generally, companies will have peering agreements that express the price for which they will route traffic for other network providers, and generally if there's a lot of reciprocal traffic, the peering will be "settlement free" - in other words, neither party charges the other to route traffic. So, in the example above, you as Comcast would agree to route Verizon's traffic across your network for free as long as Verizon did the same.

Cloudflare is a CDN, which means they push a LOT of traffic out across a lot of networks, and it's likely they're not getting as much inbound traffic as they're pushing out. That makes it harder for them to negotiate settlement-free peering, since they're not providing as much reciprocal value to their partners. By owning 1.1.1.1, they can now claim any trafic sent to that IP as "inbound" to Cloudflare's networks for the sake of peering agreements. Since 1.1.1.1 gets a bunch of traffic from either misconfigured equipment or people doing silly tests, routing that traffic helps improve Cloudflare's ability to negotiate better peering agreements.

Which, honestly, is pretty clever, since most of that traffic is garbage.

2 comments

Balanced inbound/outbound traffic only matters for transit networks. That is, networks which are neither the source nor destination of the traffic they carry.

Nobody expects a residential ISP or a CDN to have balanced flows at part of a settlement-free peering agreement.

Cloudflare as a CDN with a lot of peering connections likely helps reduce internal traffic for other carriers by virtue of having endpoint data sources close to the destinations of the data.