while also keeping file watchers on them. Envoy proxy then connects to istio-agent's SDS Server through the defined socket path and gets the cryptographic materials of the certificate files served by the SDS API.
* If istio-agent does not find either the socket, or the certificate files in their respective paths it will start its own SDS Server using a `caClient` to connect to istiod or an external CA, to fetch cryptographic materials (See Default CA Flow).