Merge pull request #1377 from openservicemesh/draychev/xds-v3

reference xDS v3 & no-cliff design

DESIGN.md

@@ -54,8 +54,8 @@ The Open Service Mesh project is composed of the following five high-level compo
 
 Let's take a look at each component:
 
-### (1) Proxy control plane
-Proxy Control plane plays a key part in operating the [service mesh](https://www.bing.com/search?q=What%27s+a+service+mesh%3F). All proxies are installed as [sidecars](https://docs.microsoft.com/en-us/azure/architecture/patterns/sidecar) and establish an mTLS gRPC connection to the Proxy Control Plane. The proxies continuously receive configuration updates. This component implements the interfaces required by the specific reverse proxy chosen. OSM implements [Envoy's go-control-plane xDS](https://github.com/envoyproxy/go-control-plane).
+### (1) Proxy Control Plane
+The Proxy Control Plane plays a key part in operating the [service mesh](https://www.bing.com/search?q=What%27s+a+service+mesh%3F). All proxies are installed as [sidecars](https://docs.microsoft.com/en-us/azure/architecture/patterns/sidecar) and establish an mTLS gRPC connection to the Proxy Control Plane. The proxies continuously receive configuration updates. This component implements the interfaces required by the specific reverse proxy chosen. OSM implements [Envoy's go-control-plane xDS v3 API](https://github.com/envoyproxy/go-control-plane). The xDS v3 API can also be used to extend the functionality provided by SMI, when [advanced Envoy features are needed](https://github.com/openservicemesh/osm/issues/1376).
 
 ### (2) Certificate Manager
 Certificate Manager is a component that provides each service participating in the service mesh with a TLS certificate.