Pod Network

jonniefivebikes

Question: Why does Kubernetes lack a pod network?
Details: The materials for Install and Config for the LFS258 class, and Kubernetes.io docs indicate that it's required to use a 3rd party pod networking tool for pod to pod communication among various other communication functionality. Why is this not something that's included with base Kubernetes functionality ?

serewicz

Hello,

I would encourage you to revisit the section about architecture. Kubernetes is not a drop-in replacement for some single-vendor tool. It's not just another OpenStack for VMs. The very architecture itself is different. We want decoupled, transient microservices. I think if you look into those three terms, and see that this is true of Kubernetes as well as all the projects of CNCF micro and macro, it will make more sense. As soon as you want to tie more components together, for whatever reason, you are reverting to a legacy approach. This is the hardest part of using Kubernetes and the Cloud. Changing the approach from legacy/mainframe concepts to flexible and scaleable microservices.

Said another way, we are not building model airplanes such that our cluster look like the box the kit came in (Following best practices from VMWare perhaps). Instead we are building with legos. Using lots and lots of legos. The legos I need at the moment may change. I may need bigger or smaller, more colors or less. More or fewer. With this analogy in mind, it would be like asking why didn't they put the legos together for me when they shipped them?

Regards,

recentcoin

Networking is so fundamental to everything that I would think that some basic connectivity "out of the box" would be desirable even if it were to get disabled and replaced by something more sophisticated (e.g. calico, etc.) later on.

Since it seems like running this on a home network using something like KVM or OpenBox virtualization is really common, I am very surprised that the defaults for the class are an entire /16. The other networking defaults in the course files also seems like it creates a lot of 10.0.0.0/8 addresses and and 172.16.0.0/12 so its almost impossible not to have some kind of an overlap.

chrispokorni

Hi @recentcoin,

It is true that the default configs are not necessarily designed for smaller size home network setups, but, considering all the flexibility that comes out of the box with all tools mentioned above, network sizes can be easily reconfigured to avoid any such overlaps.

Regards,
-Chris

jonniefivebikes

Thanks for the response. I understand your point, that Kubernetes is not intended to be a complete and monolithic solution. Similarly, one could ask why doesn't Kubernetes have a container subsystem, but instead uses Docker or CRI-O. Of course it's going to re-use good existing utilities that already exist!