3 ms·

| Aspect | Direct EC2 (No K8s) | Kubernetes (K8s Pods)

| Aspect | Direct EC2 (No K8s) | Kubernetes (K8s Pods) | |-------------------------|-------------------------------------------------------|-------------------------------------------------------------------------------------| | Networking Layers | Direct connection to EC2 instance (optional load balancer). | Service VIP → kube-proxy → CNI → pod (plus optional external load balancer). | | Load Balancing | Optional, handled by ELB/ALB or application. | Built-in via kube-proxy (iptables/IPVS) and Service. | | IP Addressing | Static or dynamic EC2 instance IP. | Pod IPs are dynamic, abstracted by Service VIP. | | Connection Persistence | Depends on application and OS TCP stack. | Depends on session affinity, graceful termination, and application reconnection logic. | | Overhead | Minimal (direct TCP). | Additional latency from kube-proxy, CNI, and load balancer. | | Resilience | Connection drops if instance fails. | Connection may drop if pod is rescheduled, but Kubernetes can reroute to new pods. | | Configuration Complexity| Simple (OS-level TCP tuning). | Complex (session affinity, PDBs, graceful termination, CNI tuning). |

avianlyric 1y ago
If you read my reply again, you’ll notice that I explicitly highlight that K8s does not require the use of a CNI. There’s a reason CNIs are plugins, and not core parts of k8s. How do you think external network traffic gets routed into a CNIs front proxy? It’s not via kube-proxy, kube-proxy isn’t designed for use in proper production systems, it’s only a stop gap to provide a functioning cluster to enable bootstrapping of a proper network management layer. There is absolutely nothing preventing a network layer directly routing external traffic to pods, with the only translation being a basic iptable rule to enable routing of data sent to a nodes network interface with a pod IP to be accepted by the node and routed to the pod. Given it’s just basic Linux network interface bridging, happening entirely in the kernel with zero copies, the impact of this layer is practically zero. Indeed the k8s services setup with external load balancers basically handle all of this setup for you. There are plenty of reasons not to use k8s, but arguing that a k8s cluster must inherently introduce multiple additional network components and complexity is simply incorrect.
- andrewfromx 1y ago
  While Kubernetes theoretically allows for simple iptables-based routing, in practice, very few production environments stop there. Most clusters do use CNIs, kube-proxy, Service abstraction, and often external load balancers or Ingress controllers, which together form a nontrivial networking stack. The claim that kube-proxy is “not designed for use in proper production systems” is simply incorrect. It is widely used in production and supported by Kubernetes core. While it has limitations—especially with high-connection-load environments—it is still the default in most distros, and even advanced CNIs like Calico and Cilium often interact with or replace kube-proxy functionality rather than ignore it. If kube-proxy is just a stopgap, why do so many managed Kubernetes platforms like GKE, EKS, and AKS still ship with it? While it’s true CNIs are plugins and not core to Kubernetes, this outsources complexity rather than eliminates it. Different CNIs (e.g., Calico, Cilium, Flannel, etc.) use different overlay models, BPF implementations, or routing approaches. Even in a CNI with kernel-fast path routing, pod churn, rolling updates, or horizontal scaling still introduce issues. Service IPs are stable, but pod IPs are ephemeral, which means Long-lived TCP clients pinned to pod IPs. You can design a lean Kubernetes network path with minimal abstractions, but: You lose things like dynamic service discovery, load balancing, and readiness-based traffic shifting. You must manage more infra manually (e.g., configure iptables or direct routing rules yourself). You’re fighting against the grain of what Kubernetes is designed to do.
  - avianlyric 1y ago
    Not entirely sure what your point is. You state that Kubernetes must come with a complex networking stack, and I point out that simply isn’t true, which apparently you agree with. But because other people use complex networking stacks in Kubernetes, that means for a bunch of good reasons, that apparently means it can’t be used without that stack? If you don’t need that functionality, and you have different requirements, then why would you implement a k8s stack that includes all that functionality? That would be foolish. Everyone ships with kube-proxy because it’s the simplest way to provide an unopinionated network stack that will give you a fully functional k8s cluster with expected bells and whistles like simple service discovery. But most people quickly replace it with a CNI for various reasons. My understanding is that your application is all about managing high throughput, direct to application TCP connections. So I have no idea why you’re talking about the need for fully fledged service discovery, or long lived TCP connections pinned to a single pod (I mean, that just the nature of TCP, got nothing to do with k8s or any of its network stacks). > You can design a lean Kubernetes network path with minimal abstractions, but: You lose things like dynamic service discovery, load balancing, and readiness-based traffic shifting. You must manage more infra manually (e.g., configure iptables or direct routing rules yourself). You’re fighting against the grain of what Kubernetes is designed to do. If you’re building a stack without k8s, then you don’t get any of those feature either, so not sure what the fuss is about. Doesn’t mean that’s k8s core competency as a workload schedular, and its general framework for managing stateful and stateless resources doesn’t provide a lot of value. You just need to learn how to take advantage of it, rather than following some cookie cutter setup for a stack that doesn’t meet your needs.

avianlyric 1y ago

If you read my reply again, you’ll notice that I explicitly highlight that K8s does not require the use of a CNI. There’s a reason CNIs are plugins, and not core parts of k8s. How do you think external network traffic gets routed into a CNIs front proxy? It’s not via kube-proxy, kube-proxy isn’t designed for use in proper production systems, it’s only a stop gap to provide a functioning cluster to enable bootstrapping of a proper network management layer. There is absolutely nothing preventing a network layer directly routing external traffic to pods, with the only translation being a basic iptable rule to enable routing of data sent to a nodes network interface with a pod IP to be accepted by the node and routed to the pod. Given it’s just basic Linux network interface bridging, happening entirely in the kernel with zero copies, the impact of this layer is practically zero. Indeed the k8s services setup with external load balancers basically handle all of this setup for you. There are plenty of reasons not to use k8s, but arguing that a k8s cluster must inherently introduce multiple additional network components and complexity is simply incorrect.

andrewfromx 1y ago
While Kubernetes theoretically allows for simple iptables-based routing, in practice, very few production environments stop there. Most clusters do use CNIs, kube-proxy, Service abstraction, and often external load balancers or Ingress controllers, which together form a nontrivial networking stack. The claim that kube-proxy is “not designed for use in proper production systems” is simply incorrect. It is widely used in production and supported by Kubernetes core. While it has limitations—especially with high-connection-load environments—it is still the default in most distros, and even advanced CNIs like Calico and Cilium often interact with or replace kube-proxy functionality rather than ignore it. If kube-proxy is just a stopgap, why do so many managed Kubernetes platforms like GKE, EKS, and AKS still ship with it? While it’s true CNIs are plugins and not core to Kubernetes, this outsources complexity rather than eliminates it. Different CNIs (e.g., Calico, Cilium, Flannel, etc.) use different overlay models, BPF implementations, or routing approaches. Even in a CNI with kernel-fast path routing, pod churn, rolling updates, or horizontal scaling still introduce issues. Service IPs are stable, but pod IPs are ephemeral, which means Long-lived TCP clients pinned to pod IPs. You can design a lean Kubernetes network path with minimal abstractions, but: You lose things like dynamic service discovery, load balancing, and readiness-based traffic shifting. You must manage more infra manually (e.g., configure iptables or direct routing rules yourself). You’re fighting against the grain of what Kubernetes is designed to do.
- avianlyric 1y ago
  Not entirely sure what your point is. You state that Kubernetes must come with a complex networking stack, and I point out that simply isn’t true, which apparently you agree with. But because other people use complex networking stacks in Kubernetes, that means for a bunch of good reasons, that apparently means it can’t be used without that stack? If you don’t need that functionality, and you have different requirements, then why would you implement a k8s stack that includes all that functionality? That would be foolish. Everyone ships with kube-proxy because it’s the simplest way to provide an unopinionated network stack that will give you a fully functional k8s cluster with expected bells and whistles like simple service discovery. But most people quickly replace it with a CNI for various reasons. My understanding is that your application is all about managing high throughput, direct to application TCP connections. So I have no idea why you’re talking about the need for fully fledged service discovery, or long lived TCP connections pinned to a single pod (I mean, that just the nature of TCP, got nothing to do with k8s or any of its network stacks). > You can design a lean Kubernetes network path with minimal abstractions, but: You lose things like dynamic service discovery, load balancing, and readiness-based traffic shifting. You must manage more infra manually (e.g., configure iptables or direct routing rules yourself). You’re fighting against the grain of what Kubernetes is designed to do. If you’re building a stack without k8s, then you don’t get any of those feature either, so not sure what the fuss is about. Doesn’t mean that’s k8s core competency as a workload schedular, and its general framework for managing stateful and stateless resources doesn’t provide a lot of value. You just need to learn how to take advantage of it, rather than following some cookie cutter setup for a stack that doesn’t meet your needs.