Explained: CoreDNS

You deploy a new service to your Kubernetes cluster. The pods come up healthy. You open a shell inside one of them and try to reach another service by name — http://payments-service — and nothing happens. Timeout. You try the full name: http://payments-service.billing.svc.cluster.local . Still nothing. You try the service's ClusterIP directly, and it works fine. Something in the cluster is resolving names, but it's not resolving yours. If … Read More

Explained: STUN Protocol

You're on a video call. The connection is direct — low latency, no relay, no server in the middle eating your bandwidth. Yet both you and the person you're talking to are behind routers, on private networks, with addresses the internet has never heard of. How did your browser find the other person? The answer, almost certainly, involved STUN . It ran silently in the background before the call even connected, took a fraction of a second,… Read More

Explained: NAT

Your laptop is sitting on a home network. It has an IP address — something like 192.168.1.42 . But that address means nothing to the rest of the internet. It's a private address, invisible beyond your router. And yet, you can open a browser, load a webpage hosted on a server in another country, and the response comes back to exactly the right device, on exactly the right tab. How? The answer is NAT — Network Address Translation. It's on… Read More

Explained: DERP Protocol

Imagine two friends trying to pass notes in a room full of locked doors. They can't reach each other directly, so they slip their notes — already sealed in envelopes — to a trusted courier standing in the middle of the room. The courier doesn't open the envelopes. They just read the name on the outside and pass them along. That, in essence, is DERP. DERP stands for Designated Encrypted Relay for Packets . It's a protocol designed to … Read More