Move externalTrafficPolicy section to virtual-ips.md

Author: alexanderConstantinescu

content/en/docs/concepts/services-networking/service.md

@@ -627,74 +627,7 @@ dispatch traffic to. The Kubernetes APIs do not define how health checks have to
 implemented for Kubernetes managed load balancers, instead it's the cloud providers
 (and the people implementing integration code) who decide on the behavior. Load
 balancer health checks are extensively used within the context of supporting the
-`externalTrafficPolicy` field for Services. If `Cluster` is specified all nodes are
-eligible load balancing targets _as long as_ the node is not being deleted and kube-proxy
-is healthy. In this mode: load balancer health checks are configured to target the
-service proxy's readiness port and path. In the case of kube-proxy this evaluates
-to: `${NODE_IP}:10256/healthz`. kube-proxy will return either an HTTP code 200 or 503.
-kube-proxy's load balancer health check endpoint returns 200 if:
-
-1. kube-proxy is healthy, meaning:
-   - it's able to progress programming the network and isn't timing out while doing
-     so (the timeout is defined to be: **2 × `iptables.syncPeriod`**); and
-2. the node is not being deleted (there is no deletion timestamp set for the Node).
-
-The reason why kube-proxy returns 503 and marks the node as not
-eligible when it's being deleted, is because kube-proxy supports connection
-draining for terminating nodes. A couple of important things occur from the point
-of view of a Kubernetes-managed load balancer when a node _is being_ / _is_ deleted.
-
-While deleting:
-
-* kube-proxy will start failing its readiness probe and essentially mark the
-   node as not eligible for load balancer traffic. The load balancer health
-   check failing causes load balancers which support connection draining to
-   allow existing connections to terminate, and block new connections from
-   establishing.
-
-When deleted:
-
-* The service controller in the Kubernetes cloud controller manager removes the
-  node from the referenced set of eligible targets. Removing any instance from
-  the load balancer's set of backend targets immediately terminates all
-  connections. This is also the reason kube-proxy first fails the health check
-  while the node is deleting.
-
-It's important to note for Kubernetes vendors that if any vendor configures the
-kube-proxy readiness probe as a liveness probe: that kube-proxy will start
-restarting continuously when a node is deleting until it has been fully deleted.
-
-Users deploying kube-proxy can inspect both the readiness / liveness state by
-evaluating the metrics: `proxy_livez_total` / `proxy_healthz_total`. Both
-metrics publish two series, one with the 200 label and one with the 503 one.
-
-For Services of `externalTrafficPolicy: Local`:  kube-proxy will return 200 if
-
-1. kube-proxy is healthy/ready, and
-2. has a local endpoint on the node in question.
-
-Node deletion does **not** have an impact on kube-proxy's return
-code for what concerns load balancer health checks. The reason for this is:
-deleting nodes could end up causing an ingress outage should all endpoints
-simultaneously be running on said nodes.
-
-It's important to note that the configuration of load balancer health checks is
-specific to each cloud provider, meaning: different cloud providers configure
-the health check in different ways. The three main cloud providers do so in the
-following way:
-
-* AWS: if ELB; probes the first NodePort defined on the service spec
-* Azure: probes all NodePort defined on the service spec.
-* GCP: probes port 10256 (kube-proxy's healthz port)
-
-There are drawbacks and benefits to each method, so none can be considered fully
-right, but it is important to mention that connection draining using kube-proxy
-can therefore only occur for cloud providers which configure the health checks to
-target kube-proxy. Also note that configuring health checks to target the application
-might cause ingress downtime should the application experience issues which
-are unrelated to networking problems. The recommendation is therefore that cloud
-providers configure the load balancer health checks to target the service
-proxy's healthz port.
+`externalTrafficPolicy` field for Services.
 
 #### Load balancers with mixed protocol types
 

content/en/docs/reference/networking/virtual-ips.md

@@ -488,6 +488,67 @@ route to ready node-local endpoints. If the traffic policy is `Local` and there
 are no node-local endpoints, the kube-proxy does not forward any traffic for the
 relevant Service.
 
+If `Cluster` is specified all nodes are eligible load balancing targets _as long as_
+the node is not being deleted and kube-proxy is healthy. In this mode: load balancer 
+health checks are configured to target the service proxy's readiness port and path.
+In the case of kube-proxy this evaluates to: `${NODE_IP}:10256/healthz`. kube-proxy
+will return either an HTTP code 200 or 503. kube-proxy's load balancer health check
+endpoint returns 200 if:
+
+1. kube-proxy is healthy, meaning:
+   - it's able to progress programming the network and isn't timing out while doing
+     so (the timeout is defined to be: **2 × `iptables.syncPeriod`**); and
+2. the node is not being deleted (there is no deletion timestamp set for the Node).
+
+The reason why kube-proxy returns 503 and marks the node as not
+eligible when it's being deleted, is because kube-proxy supports connection
+draining for terminating nodes. A couple of important things occur from the point
+of view of a Kubernetes-managed load balancer when a node _is being_ / _is_ deleted.
+
+While deleting:
+
+* kube-proxy will start failing its readiness probe and essentially mark the
+   node as not eligible for load balancer traffic. The load balancer health
+   check failing causes load balancers which support connection draining to
+   allow existing connections to terminate, and block new connections from
+   establishing.
+
+When deleted:
+
+* The service controller in the Kubernetes cloud controller manager removes the
+  node from the referenced set of eligible targets. Removing any instance from
+  the load balancer's set of backend targets immediately terminates all
+  connections. This is also the reason kube-proxy first fails the health check
+  while the node is deleting.
+
+It's important to note for Kubernetes vendors that if any vendor configures the
+kube-proxy readiness probe as a liveness probe: that kube-proxy will start
+restarting continuously when a node is deleting until it has been fully deleted.
+kube-proxy exposes a `/livez` path which, as opposed to the `/healthz` one, does
+**not** consider the Node's deleting state and only its progress programming the
+network. `/livez` is therefore the recommended path for anyone looking to define
+a livenessProbe for kube-proxy.
+
+Users deploying kube-proxy can inspect both the readiness / liveness state by
+evaluating the metrics: `proxy_livez_total` / `proxy_healthz_total`. Both
+metrics publish two series, one with the 200 label and one with the 503 one.
+
+For `Local` Services: kube-proxy will return 200 if
+
+1. kube-proxy is healthy/ready, and
+2. has a local endpoint on the node in question.
+
+Node deletion does **not** have an impact on kube-proxy's return
+code for what concerns load balancer health checks. The reason for this is:
+deleting nodes could end up causing an ingress outage should all endpoints
+simultaneously be running on said nodes.
+
+The Kubernetes project recommends that cloud provider integration code
+configures load balancer health checks that target the service proxy's healthz
+port. If you are using or implementing your own virtual IP implementation,
+that people can use instead of kube-proxy, you should set up a similar health
+checking port with logic that matches the kube-proxy implementation.
+
 ### Traffic to terminating endpoints
 
 {{< feature-state for_k8s_version="v1.28" state="stable" >}}