networking: One way to make containers network: BGP - Julia Evans

One way to make containers network: BGP - Julia Evans: "Okay, so, again, I have 5 containers, all running things on port 4000. The key observation here is -- it's okay to run a bunch of things on the same port as long as they're on different IPs. Normally on one computer you only use one IP address. But that doesn't have to be true! You can have lots!

So. I have 5 containers, and I've assigned them IPs 10.0.1.101, 10.0.1.102, 10.0.1.103, 10.0.1.104, 10.0.1.105. Inside my computer, this is fine -- it's easy to imagine that I can just know which one is which.

But what do I do if I have another computer on the same network? How does that container know that 10.0.1.104 belongs to a container on my computer?

The Linux kernel knows about the BGP protocol. Calico knows about the Linux kernel. So Calico says "hey linux! Tell these other computers on the network to find these IP addresses here, okay?" And then all the traffic for those IPs comes to our computer, and everything is great.

To me, this seems pretty nice. It means that you can easily interpret the packets coming in and out of your machine (and, because we love tcpdump, we want to be able to understand our network traffic). I think there are other advantages but I'm not sure what they are.



 I find reading this networking stuff pretty difficult; more difficult than usual. For example, Docker also has a networking product they released recently. The webpage says they're doing "overlay networking". I don't know what that is, but it seems like you need etcd or consul or zookeeper. So the networking thing involves a distributed key-value store? Why do I need to have a distributed key-value store to do networking? There is probably a talk about this that I can watch but I don't understand it yet."



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