Networking on Chen Kai Blog

Alibaba Cloud Full Stack (3): VPC, SLB, and the Network Layer

Thu, 30 Apr 2026 09:00:00 +0000

Every outage I have debugged in the cloud ultimately traced back to networking. Bad CIDR planning that ran out of IPs six months in. Missing routes that silently dropped traffic between tiers. Security groups that were either wide open (hello, port 22 to 0.0.0.0/0) or so locked down that health checks failed and the load balancer kept draining healthy instances. Getting the network layer right is the single most important thing you can do before deploying anything else, and it is the single most painful thing to fix retroactively because changing a VPC CIDR means recreating everything inside it.

System Design (2): DNS, CDN, and Load Balancing — The First Three Hops

Sat, 12 Jul 2025 09:00:00 +0000

In 2017, a single misconfigured DNS record at a major cloud provider took down a significant portion of the internet for several hours. Thousands of websites became unreachable — not because their servers were down, but because the system that translates domain names into IP addresses stopped working correctly. The incident was a stark reminder that the infrastructure we take for granted — DNS, CDN, load balancers — is the foundation everything else rests on.

Docker and Containers (4): Networking and Volumes — How Containers Talk and Persist

Mon, 19 Jun 2023 09:00:00 +0000

Containers are deliberately isolated. That’s the point. But useful applications need to accept connections from the outside world, talk to databases, and store data that survives container restarts. Docker provides two mechanisms for this: networks (for communication) and volumes (for persistent storage). Getting these right makes the difference between a demo and a deployment.

Docker Networking#

When Docker starts, it creates a virtual network infrastructure on the host. Each container gets its own network namespace (with its own IP address, routing table, and network interfaces), and Docker manages the traffic flow between containers and the outside world.