* If the serialization type is application/vnd.kubernetes.protobuf, and protobuf marshaling is not implemented for the requested API resource type, a '406 Not Acceptable is returned'.
    * If the serialization type is 'application/json':

### SIG AWS

In v1.13 we worked on tighter integrations of Kubernetes API objects with AWS services. These include three out-of-tree alpha feature releases:

1) Alpha for AWS ALB (Application Load Balancer) integration to Kubernetes Ingress resources.
2) Alpha for CSI specification 0.3 integration to AWS EBS (Elastic Block Store)

  * The webhook and log file now output the `v1beta1` event format.

    For more details, see [Advanced audit](https://kubernetes.io/docs/tasks/debug-application-cluster/audit/#advanced-audit).

* The deprecated `ThirdPartyResource` (TPR) API was removed.

- client-go discovery clients constructed using `NewDiscoveryClientForConfig` or `NewDiscoveryClientForConfigOrDie` default to rate limits that cause normal discovery request...

    <td>GET /swagger.json</td>
    <td>GET /openapi/v2
Accept: application/json</td>
  </tr>
  <tr>
    <td>GET /swagger-2.0.0.pb-v1</td>
    <td>GET /openapi/v2
Accept: application/com.github.proto-openapi.spec.v2@v1.0+protobuf</td>
  </tr>
  <tr>
    <td>GET /swagger-2.0.0.pb-v1.gz</td>
    <td>GET /openapi/v2
Accept: application/com.github.proto-openapi.spec.v2@v1.0+protobuf Accept-Encoding: gzip</td>

Kubelet supports 100 pods per node with 4x reduced system overhead.
  * <strong>Simplified application deployment and management. </strong>
     * Dynamic Configuration (ConfigMap API in the core API group) enables application
configuration to be stored as a Kubernetes API object and pulled dynamically on
container startup, as an alternative to baking in command-line flags when a

- Fixed file permission issues that happened during update of `Secret`/`ConfigMap`/`projected volume` when `fsGroup` is used. The problem caused a race condition where application gets intermittent permission denied error when reading files that were just updated, before the correct permissions were applied. ([#114464](https://github.com/kubernetes/kubernetes/pull/114464), [@tsaarni](https://github.com/tsaarni))

    - [**Other notable changes**](#other-notable-changes-16)
      - [Admission plugin](#admission-plugin)
      - [API Machinery](#api-machinery-1)
      - [Application autoscaling](#application-autoscaling-1)
      - [Application Deployment](#application-deployment-1)
      - [Cluster Autoscaling](#cluster-autoscaling)
      - [Cloud Provider Enhancement](#cloud-provider-enhancement)

  - [beta] PodDisruptionBudget has been promoted to beta, can be used to safely drain nodes while respecting application SLO's ([docs](http://kubernetes.io/docs/tasks/administer-cluster/safely-drain-node/)) ([kubernetes/features#85](https://github.com/kubernetes/enhancements/issues/85))
- **UI**

- kubeadm: fix "certificate-authority" files not being pre-loaded when using file discovery ([#80966](https://github.com/kubernetes/kubernetes/pull/80966), [@neolit123](https://github.com/neolit123))
- Add instruction to setup "Application Default Credentials" to run GCE Windows e2e tests locally. ([#81337](https://github.com/kubernetes/kubernetes/pull/81337), [@YangLu1031](https://github.com/YangLu1031))