Good news for you – there are many fast growing overlay solutions that are adopted by apps and security teams and bypass the networking teams altogether.
That sounds awesome in a VC pitch deck. Let’s see how well that concept works out in reality using Docker Swarm as an example (Kubernetes is probably even worse).
It took me a long while to decode what Docker is doing behind the scenes (documentation lacking critical details didn’t exactly help), but finally I got there with copious help of detailed third-party blog posts. Here’s a diagram documenting the Linux networking constructs a packet must traverse to get from an Ethernet NIC to a container deployed as a simple Docker Swarm service:
- Gray boxes are namespaces (from host TCP stack to container namespace);
- Bridges are Linux bridges;
- Routers are full-blown Linux TCP/IP stacks;
- Vertical boxes are iptables tables.
All it takes to get Docker Swarm service up and running are three Linux bridges, three full-blown TCP stacks, two sets of NAT iptables, a mangle iptable, and a kernel-based load balancer. To make it even more fun, Docker hides most of these constructs in three network namespaces that are not visible unless you remap /var/run directories. What could be more fun to troubleshoot? How about the same service spread across multiple Docker hosts (omitting the host TCP stack transporting VXLAN packets)?
For a step-by-step deep dive into behind-the-scenes packet processing, register for the Docker Networking Deep Dive live session on September 1st 2020.