Add doc about NGINX Plus

README.md

@@ -31,6 +31,8 @@ NGINX Ingress controller works with both NGINX and NGINX Plus and supports the s
 
 Additionally, several NGINX and NGINX Plus features are available as extensions to the Ingress resource via annotations and the ConfigMap resource. In addition to HTTP, NGINX Ingress controller supports load balancing Websocket, gRPC, TCP and UDP applications. See [ConfigMap and Annotations doc](docs/configmap-and-annotations.md) to learn more about the supported features and customization options.
 
+Read [this doc](docs/nginx-plus.md) to learn more about NGINX Ingress controller with NGINX Plus.
+
 ## Getting Started
 
 1. Install the NGINX Ingress controller using the Kubernetes [manifests](deployments) or the [helm chart](deployments/helm-chart).

docs/nginx-ingress-controllers.md

@@ -8,7 +8,7 @@ If you are unsure about which implementation you are using, check the container
 
 ## The Key Differences
 
-The table below summarizes the key difference between nginxinc/kubernetes-ingress and kubernetes/ingress-nginx Ingress controllers. Note that the table has two columns for the nginxinc/kubernetes-ingress Ingress controller, as it can be used both with NGINX and NGINX Plus
+The table below summarizes the key difference between nginxinc/kubernetes-ingress and kubernetes/ingress-nginx Ingress controllers. Note that the table has two columns for the nginxinc/kubernetes-ingress Ingress controller, as it can be used both with NGINX and NGINX Plus. For more information about nginxinc/kubernetes-ingress with NGINX Plus, read [here](nginx-plus.md). 
 
 | Aspect or Feature | kubernetes/ingress-nginx | nginxinc/kubernetes-ingress with NGINX | nginxinc/kubernetes-ingress with NGINX Plus |
 | --- | --- | --- | --- |

docs/nginx-plus.md

@@ -0,0 +1,15 @@
+# NGINX Ingress Controller with NGINX Plus
+
+NGINX Ingress controller works with both [NGINX](https://nginx.org/) and [NGINX Plus](https://www.nginx.com/products/nginx/) -- a commercial closed source version of NGINX that comes with additional features and support. 
+
+Below are the key characteristics that NGINX Plus brings on top of NGINX into the NGINX Ingress controller:
+* **Additional features**
+    * *Real-time metrics* A number metrics about how NGINX Plus and applications are performing are available through the API or a [built-in dashboard](installation.md#5-access-the-live-activity-monitoring-dashboard--stub_status-page). Optionally, the metrics can be exported to [Prometheus](installation.md#support-for-prometheus-monitoring).
+    * *Additional load balancing methods*. The following additional methods are available: `least_time` and `random two least_time` and their derivatives. See the [documentation](https://nginx.org/en/docs/http/ngx_http_upstream_module.html) for the complete list of load balancing methods.
+    * *Session persistence* The *sticky cookie* method is available. See the [Session Persistence](../examples/session-persistence) example.
+    * *Active health checks*. See the [Support for Active Health Checks](../examples/health-checks) example.
+    * *JWT validation*. See the [Support for JSON Web Tokens (JWTs)](../examples/jwt) example.
+
+    See [ConfigMap and Annotations](configmap-and-annotations.md) doc for the complete list of available NGINX Plus features. Note that such features are configured through annotations that start with `nginx.com`, for example, `nginx.com/health-checks`.
+* **Dynamic reconfiguration** Every time the number of pods of services you expose via an Ingress resource changes, the Ingress controller updates the configuration of the load balancer to reflect those changes. For NGINX, the configuration file must be changed and the configuration subsequently reloaded. For NGINX Plus, the dynamic reconfiguration is utilized, which allows NGINX Plus to be updated on-the-fly without reloading the configuration. This prevents increase of memory usage during reloads, especially with a high volume of client requests, as well as increased memory usage when load balancing applications with long-lived connections (WebSocket, applications with file uploading/downloading or streaming).
+* **Commercial support** Support from NGINX Inc is available for NGINX Plus Ingress controller.