* kubectl: This client version requires the `apps/v1` APIs, so it will not work against a cluster version older than v1.9.0. Note that kubectl only guarantees compatibility with clusters that are +/-1 minor version away. ([#61419](https://github.com/kubernetes/kubernetes/pull/61419), [@enisoc](https://github.com/enisoc))

- Kubectl version changed to write a warning message to stderr if the client and server version difference exceeds the supported version skew of +/-1 minor version. ([#98250](https://github.com/kubernetes/kubernetes/pull/98250), [@brianpursley](https://github.com/brianpursley)) [SIG CLI]

* fixes configuration error when upgrading kubeadm from 1.9 to 1.10+ ([#62568](https://github.com/kubernetes/kubernetes/pull/62568), [@liztio](https://github.com/liztio))
    * enforces  kubeadm  upgrading kubernetes from the same major and minor versions as the kubeadm binary.
* Bugfix allowing use of IP-aliases with custom-mode network in GCE setup scripts. ([#62172](https://github.com/kubernetes/kubernetes/pull/62172), [@shyamjvs](https://github.com/shyamjvs))

* Protobuf serialization does not distinguish between `[]` and `null`.

* Add automatic etcd 3.2->3.1 and 3.1->3.0 minor version rollback support to gcr.io/google_container/etcd images. For HA clusters, all members must be stopped before performing a rollback. ([#59298](https://github.com/kubernetes/kubernetes/pull/59298), [@jpbetz](https://github.com/jpbetz))

- kubeadm: Allow users to skip the kube-proxy init addon phase during init and still be able to join a cluster and perform some other minor operations (but not upgrade). ([#82248](https://github.com/kubernetes/kubernetes/pull/82248), [@rosti](https://github.com/rosti))

### SIG Network

For 1.13, the areas of focus were in IPv6, DNS improvements and some smaller items:

pkg syscall (netbsd-arm64-cgo), type BpfVersion struct
pkg syscall (netbsd-arm64-cgo), type BpfVersion struct, Major uint16
pkg syscall (netbsd-arm64-cgo), type BpfVersion struct, Minor uint16
pkg syscall (netbsd-arm64-cgo), type Cmsghdr struct
pkg syscall (netbsd-arm64-cgo), type Cmsghdr struct, Len uint32
pkg syscall (netbsd-arm64-cgo), type Cmsghdr struct, Level int32

* Bump cluster autoscaler to v0.5.4, which fixes scale down issues with pods ignoring SIGTERM. ([#45483](https://github.com/kubernetes/kubernetes/pull/45483), [@mwielgus](https://github.com/mwielgus))
* Fixes and minor cleanups to pod (anti)affinity predicate ([#45098](https://github.com/kubernetes/kubernetes/pull/45098), [@wojtek-t](https://github.com/wojtek-t))

- The `gcp` and `azure` auth plugins have been restored to client-go and kubectl until https://issue.k8s.io/111911 is resolved in supported kubectl minor versions. ([#111918](https://github.com/kubernetes/kubernetes/pull/111918), [@liggitt](https://github.com/liggitt))

### Documentation