Merge pull request #1893 from m1093782566/cni-tc

Support traffic shaping for Kubelet CNI network plugin

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diff --git a/contributors/design-proposals/network/support_traffic_shaping_for_kubelet_cni.md b/contributors/design-proposals/network/support_traffic_shaping_for_kubelet_cni.md
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+# Support traffic shaping for CNI network plugin
+
+Version: Alpha
+
+Authors: @m1093782566
+
+## Motivation and background
+
+Currently the kubenet code supports applying basic traffic shaping during pod setup. This will happen if bandwidth-related annotations have been added to the pod's metadata, for example:
+
+```json
+{
+    "kind": "Pod",
+    "metadata": {
+        "name": "iperf-slow",
+        "annotations": {
+            "kubernetes.io/ingress-bandwidth": "10M",
+            "kubernetes.io/egress-bandwidth": "10M"
+        }
+    }
+}
+```
+
+Our current implementation uses the `linux tc` to add an download(ingress) and upload(egress) rate limiter using 1 root `qdisc`, 2 `class `(one for ingress and one for egress) and 2 `filter`(one for ingress and one for egress attached to the ingress and egress classes respectively).
+
+Kubelet CNI code doesn't support it yet, though CNI has already added a [traffic sharping plugin](https://github.com/containernetworking/plugins/tree/master/plugins/meta/bandwidth). We can replicate the behavior we have today in kubenet for kubelet CNI network plugin if we feel this is an important feature.
+
+## Goal
+
+Support traffic shaping for CNI network plugin in Kubernetes.
+
+## Non-goal
+
+CNI plugins to implement this sort of traffic shaping guarantee.
+
+## Proposal
+
+If kubelet starts up with `network-plugin = cni` and user enabled traffic shaping via the network plugin configuration, it would then populate the `runtimeConfig` section of the config when calling the `bandwidth` plugin.
+
+Traffic shaping in Kubelet CNI network plugin can work with ptp and bridge network plugins.
+
+### Pod Setup
+
+When we create a pod with bandwidth configuration in its metadata, for example, 
+
+```json
+{
+    "kind": "Pod",
+    "metadata": {
+        "name": "iperf-slow",
+        "annotations": {
+            "kubernetes.io/ingress-bandwidth": "10M",
+            "kubernetes.io/egress-bandwidth": "10M"
+        }
+    }
+}
+```
+
+Kubelet would firstly parse the ingress and egress bandwidth values and transform them to Kbps because both `ingressRate` and `egressRate` in cni bandwidth plugin are in Kbps. A user would add something like this to their CNI config list if they want to enable traffic shaping via the plugin:
+
+```json
+{
+  "type": "bandwidth",
+  "capabilities": {"trafficShaping": true}
+}
+```
+
+Kubelet would then populate the `runtimeConfig` section of the config when calling the `bandwidth` plugin:
+
+```json
+{
+  "type": "bandwidth",
+  "runtimeConfig": {
+    "trafficShaping": {
+      "ingressRate": "X",
+      "egressRate": "Y"
+    }
+  }
+}
+```
+
+### Pod Teardown
+
+When we delete a pod, kubelet will bulid the runtime config for calling cni plugin `DelNetwork/DelNetworkList` API, which will remove this pod's bandwidth configuration.
+
+## Next step
+
+* Support ingress and egress burst bandwidth in Pod.
+* Graduate annotations to Pod Spec.