I notice that you conveniently left out the "ingress" component. Stuff in K8s talking with other K8s stuff is easy. Getting the flows into K8s apps from outside the K8 network is amazingly clunky in its current state.
But outside the container, the strategy is still much simpler than other solutions (most of which predate Kubernetes). Kubernetes chooses to give every pod its own IP. This means choosing an internal network such as 10.x.x.x, and giving each machine a slice of it. This way, one single cluster shares the same big, flat space of IP addresses; not only do pods have the same IP inside the container, but they can talk to other pods using the other pod's IP, too.
But a key point is that Kubernetes is designed to take care of most of it. One part of it is the iptables proxy magic that it does to allow services to have dynamically assigned IPs, too, with simple load-balancing between them. The second part is the many built-in plugins for different, more complicated overlay strategies. Kubernetes' automatic configuration works out of the box on, say, AWS, without anything magical — Kubernetes natively talks to AWS to set up a routing table so that packets end up where they should. You don't need more complex overlay networking stacks such as Calico, Flannel or Weave right away.
As for ingress, it has absolutely been Kubernetes' weakest point for several years, and the Kubernetes team knows this perfectly well. That said, it's not complicated, thanks to the above. Once you have, say, Nginx listening on a port, routing traffic into the cluster is a matter of setting up a load balancer (at least on clouds like GCP, DigitalOcean and AWS), something which Kubernetes even can do automatically for you. The weak links are the ingress controller — the Nginx one is popular because it's stable and supports common features such as TLS, whereas others such as Voyager and Traefik are lagging — as well as the impedance mismatch with cloud LBs such as the Google Load Balancer.
So far, Kubernetes' ingress support has been generic: One ingress object can be used to "drive" different HTTP servers. The problem being, of course, that all HTTP implementations which have different settings (timeouts, TLS certs, CDN functionality) and concerns that the current, simple ingress format cannot support. I'm expecting this to change soon. Ingress portability really isn't an important concern, and the generic ingress format is a bottleneck for the ingress functionality to mature.
Why is having a big, flat namespace important? Routers route. Clos L3 networks are no longer a fancy thing. They're commonplace now. I don't see any advantage of having a flat network.
> One part of it is the iptables proxy magic that it does to allow services to have dynamically assigned IPs, too, with simple load-balancing between them.<
Ah yes, the iptables "magic". We call this, slowness and obfuscation. People who understand how to run networks don't like handwavy magic. We like simple, elegant concepts. Kubernetes networking is very far from simple and elegant. It's blackbox "magic".
>You don't need more complex overlay networking stacks such as Calico, Flannel or Weave right away.<
I run a native L3 network so have no need for an overlay network on top of it. That said, I'd argue that the overlay junk is probably easier for non-networking-fluent developers to setup and run compared to routing in AWS.
Kubernetes networking can be summed up thusly: Great for developers who know nothing about networking but want to run at hyperscale. Terrible for people who actually know how to run networks properly.
Kubernetes ingress is garbage. Stop apologizing for it.
IPv6 would also get rid of 99% of these overly complicated hand-wavy solutions that Kubernetes proponents constantly tout as strong points. Give each node a /64, and you're set.
You're arguing against the value of a "big, flat namespace", yet you're also arguing for IPv6, which itself is a big, flat namespace? Do you see the contradiction, perhaps?
Dedicated CIDR for pods is important because it's simple. The symmetry is simple to explain, simple to understand; the same simplicity you'd get from IPv6.
Moreover, it's an abstraction that can be implemented however you want (custom routing on L3, SDN overlay, BGP). Not everone has a native L3 network. If you're on Google Cloud Platform, you get a virtual L3, but with other clouds, the networking is a bit more old hat. So again, simplicity and convenience. As for "overlay junk", the entirety of the Google Cloud itself is virtualized over what is probably the world's most sophisticated SDN overlay, so, well, some people's junk is other people's ragingly successful business, I suppose.
I'm not sure why you categorize the automatic iptables rules that Kubernetes set up as slow or obfuscated. It's only magical in the sense that Kubernetes automatically makes its cluster IPs load-balanced, a convenient system that you are in no way forced to use. If you have a better setup, feel free to use it instead.
We use Kubernetes ingress. It works. It could be better, but it's not "garbage". I really recommend against putting everything in such categorical terms. Everything in your comment is "junk" and "garbage", and the people who designed it (Google!) are morons who don't understand networking, somehow. That kind of arrogance on HN just makes you look foolish.
Ingress components are maturing, and I think will seem more natural once they've matured, stabilized, and become more visible in the documentation.
At present though it's a bit of a hump... Running my own K8s cluster on-premise I suspect like a lot of that clunkiness ie because in its natural environments (Google and Googles Cloud), it has direct access to nice load balancing and routing systems/services.
