* Kubernetes now supports up to 5,000 nodes via etcd v3, which is enabled by default.
* [Role-based access control (RBAC)](https://kubernetes.io//docs/admin/authorization/rbac) has graduated to beta, and defines secure default roles for control plane, node, and controller components.
* The [`kubeadm` cluster bootstrap tool](https://kubernetes.io/docs/getting-started-guides/kubeadm/) has graduated to beta. Some highlights:

- The built-in system:csi-external-provisioner and system:csi-external-attacher cluster roles are removed as of 1.17 release ([#84282](https://github.com/kubernetes/kubernetes/pull/84282), [@tedyu](https://github.com/tedyu))

  - The built-in `system:csi-external-provisioner` and `system:csi-external-attacher` cluster roles are deprecated and will not be auto-created in a future release. CSI deployments should provide their own RBAC role definitions with required permissions. ([#69868](https://github.com/kubernetes/kubernetes/pull/69868), [@pohly]( https://github.com/pohly))...

* Fix credentials providers for docker sandbox image. ([#51870](https://github.com/kubernetes/kubernetes/pull/51870), [@feiskyer](https://github.com/feiskyer))
* Fix security holes in GCE metadata proxy. ([#51302](https://github.com/kubernetes/kubernetes/pull/51302), [@ihmccreery](https://github.com/ihmccreery))

- The `BalancedAllocation` plugin now skips all best-effort (zero-requested) pods. ([#130260](https://github.com/kubernetes/kubernetes/pull/130260), [@Bowser1704](https://github.com/Bowser1704))
- The following roles have had `Watch` added to them (prefixed with `system:controller:`):
  
  - `cronjob-controller`
  - `endpoint-controller`
  - `endpointslice-controller`
  - `endpointslicemirroring-controller`

* corrects a race condition in bootstrapping aggregated cluster roles in new HA clusters ([#63761](https://github.com/kubernetes/kubernetes/pull/63761), [@liggitt](https://github.com/liggitt))

- Warn instead of fail when creating Roles and ClusterRoles with custom verbs via kubectl ([#92492](https://github.com/kubernetes/kubernetes/pull/92492), [@eddiezane](https://github.com/eddiezane)) [SIG CLI]

* Corrected a race condition in bootstrapping aggregated cluster roles in new HA clusters ([#63761](https://github.com/kubernetes/kubernetes/pull/63761), [@liggitt](https://github.com/liggitt))

- `kubectl create token` can now be used to request a service account token, and permission to request service account tokens is added to the `edit` and `admin` RBAC roles ([#107880](https://github.com/kubernetes/kubernetes/pull/107880), [@liggitt](https://github.com/liggitt))

        FLAGS[prefixFlag or frameFlag or FLAG_PADDED] =
          FLAGS[prefixFlag] + '|'.toString() + FLAGS[frameFlag] + "|PADDED"
      }
    }

    for (i in FLAGS.indices) { // Fill in holes with binary representation.
      if (FLAGS[i] == null) FLAGS[i] = BINARY[i]
    }
  }

  /**
   * Returns a human-readable representation of HTTP/2 frame headers.
   *
   * The format is:
   *