## Reference

```

### New API customization

The [new platform level installation API](https://github.com/istio/api/blob/master/operator/v1alpha1/operator.proto)
defines install time parameters like component and enablement and namespace, and K8s settings like resources, HPA spec etc. in a structured way.
The simplest customization is to turn components on and off. For example, to turn on cni ([samples/cni-on.yaml](samples/cni-on.yaml):

```yaml

### Examples

#### Configuring mesh configuration settings

Any [Mesh Config](https://istio.io/latest/docs/reference/config/istio.mesh.v1alpha1/) options can be configured like below:

```yaml
meshConfig:
  accessLogFile: /dev/stdout
```

#### Revisions

Control plane revisions allow deploying multiple versions of the control plane in the same cluster.

```

#### Migrating an existing Helm release

An existing helm release can be `helm upgrade`d to this chart by using the same release name. For example, if a previous
installation was done like:

```console
helm install istio-ingress manifests/charts/gateways/istio-ingress -n istio-system
```

It could be upgraded with

```console

   between services in the cluster and from a service to external
   services. The proxies form a _secure microservice mesh_ providing a rich
   set of functions like discovery, rich layer-7 routing, circuit breakers,
   policy enforcement and telemetry recording/reporting
   functions.

  > Note: The service mesh is not an overlay network. It